Neuroradiology
Computed Tomography with the EMI Scanner in the Diagnosis of Primary and Metastatic Intracranial Neoplasms1 Paul F. J. New, M.D., William R. Scott, M.D.,2 James A. Schnur, M.D.,2 Kenneth R. Davis, M.D.,2 Juan M. Taveras, M.D., and Fred H. Hochberg, M.D. The findings and diagnostic results in 600 examinations of primary and metastatic intracranial neoplasms performed at one hospital with the EMI scanner are presented and the effectiveness of this method is compared with that of radionuc1ide imaging, cerebral angiography, and pneumoencephalography. The computed scan proved to be highly reliable in the diagnosis of glioma, cerebral metastases, meningioma, and acoustic neuroma. INDEX TERMS: Brain Neoplasms, diagnosis • Brain Neoplasms, metastases • Computed Tomography • Glioma. Meninges, neoplasms. Neurinoma Radiology 114:75-87, January 1975
OMPUTED tomography (CT) with the EMI scanner is a relatively new method of brain study that has been described and discussed in several articles within the past two years (1-8). In this technique the cranium is scanned 180 times at different angles by a narrow x-ray beam. Differential absorption by tissues in contiguous slices is calculated by a computer and presented as a series of images of the structure of the brain. This method is capable of revealing a remarkable amount of anatomical and pathological information and is rapidly gaining wide acceptance as an important and clinically useful modality. We now wish to review in detail the results of computed tomographic studies in our initial series of 600 patients.
TABLE
C
I:
RESULTS OF
600
EXAMINATIONS
No. of Examinations Normal Atrophic disease Porencephaly Obstructive hydrocephalus (nontumorous) Mixture of normal-pressure hydrocephalus and atrophy Infarct Ischemic (59 cases) Hemorrhagic (4 cases) Extradural hematoma Subdural hematoma Intracranial hematoma Hypertensive supratentorial (14 cases) infratentorial (2 cases) Traumatic (4 cases) Arteriovenous malformation (4 cases) Aneurysm (1 case) Coumadin (1 case) Abscess Glioma Medulloblastoma Metastases Meningioma Acoustic neuroma Pineal area tumor Craniopharyngioma Pituitary adenoma Miscellaneous lesions Not proved Technically unsatisfactory
MATERIAL Our patients ranged between 3 days and 90 years of age. Several patients had more than one type of lesion, and classification was based on the clinically dominant condition (TABLE I). Many patients were scanned more than once, often 3 or 4 times, for a number of reasons: (a) unsatisfactory initial scans due to excessive motion, (b) for followup of the progress of a lesion, including irradiated tumors, and (c) diagnosis of suspected postoperative or other complications. Eleven per cent of the examinations were classified as normal. One patient seen early in the series was thought to have a normal CT scan, whereas angiography and radionuclide images indicated infarction. Subsequent review revealed evidence of infarction on the CT scan as well.
68 94 6 19
% of Total Examinations 11 16 3
3 77
13
2
12 35
6
4
43
7
1
26 14 8 11 5 5
4
32 118 17 600
20 3
83%
(9 groups)
In one 45-year-old man with a three-year history of temporal-lobe seizures, two CT scans taken five months apart revealed no convincing evidence of pathology, although pneumoencephalography had suggested a mass in the left temporal lobe. A left carotid angiogram was interpreted as probably
1 From the Departments of Radiology (P. F. J. N., W. R. S., J. A. S., K. R. D., J. M. T.) and Neuropathology (F. H. H.), Massachusetts General Hospital and Harvard Medical School, Boston, Mass. Accepted for publication in September 1974. Presented at the Tenth International Symposium Neuroradiologicum, Punta del Este, Uruguay, March 10-16, 1974. 2 Supported in part by NINDS Neuroradiology Special Fellowships 5F 11 NS 02458-02 (W. R. S.), 5F 11 NS 02586-02 (J. A. S.), and 5F 11 NS 02622-02 (K. R. D.). sjh
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normal. Multiple serum samples were positive for glioma antigen, and an en bloc medial temporal lobectomy was performed by Dr. William H. Sweet. No definite histological abnormality was identified in the portion of the resected specimen subjected to neuropathological examination. However, tissue cultures from an adjacent portion of the specimen supported growth of cells, 41% of which were multinucleated (as described by Dr. Paul L. Kornblith) and which were shown by electron microscopy to contain many glial-type fibrils measuring 90-100 A. The cells have continued to grow in a rapid and vigorous fashion, more compatible with tumor than with normal brain cells. In another patient with suspected glioma of the optic chiasm, the CT scan was unrevealing, but pneumoencephalography and laminagraphy revealed minor changes in the area of the optic chiasm, suggesting a very small glioma. Proof is lacking to date. A diagnosis of anatomical normality on the CT scan was not disproved by other radiological tests in any other case in this series, save for small structural abnormalities of the cerebral arteries, such as atheromas and anuerysms. Various forms of atrophy and degenerative disease were seen in 16% of cases, and 55% of these patients had dementia. Nontumorous obstructive hydrocephalus was found in 3% of cases, primarily patients with dementia. In all but 3 cases, atrophic brain disease was easily differentiated from occult obstructive hydrocephalus. In 2, elements of both conditions seemed to be present, and a mixed pattern was also indicated by radionuclide studies of cerebrospinal fluid flow in these cases. Cerebral or cerebellar infarcts were seen in 13% of patients of various ages. The ratio of ischemic to hemorrhagic infarction was 15 to 1. Intracerebral hematomas of various types were seen in 6% of cases. Seven per cent of the entire series of patients had glioma and 4% had metastases to the brain. Twenty per cent could not be classified satisfactorily owing to insufficient proof of pathology in the relatively short follow-up period involved. Three per cent of the examinations proved to be technically unsatisfactory, mostly due to motion, with a few due to the presence of gas, Pantopaque, or metal surgical structures. In most of the former cases, a subsequent study was satisfactory. We have been able to reduce effectively or eliminate head movement during CT scanning by using a dental plate and mold as will be described elsewhere (9). In one case, an acromegalic patient's head was too large to fit through the retaining ring of the scanner.
January 1975
Postoperative changes per se were not a serious problem in re-evaluation by CT scanning unless a large number of sizable metal surgical clips, burr hole plugs, or the valves of certain ventricular shunts were present, as these tend to produce more or less severe artifacts which obscure anatomical detail. On the other hand, the tissue changes produced by surgery do not affect CT scans obtained long afterward as they do postoperative radionuclide images. Also, edema, contusion, or hematoma can be correctly attributed to trauma to the scalp and cranial vault without the confusion of intracranial diagnosis that sometimes occurs with radionuclide images.
Gliomas A low- or intermediate-grade astrocytoma typically appears as an area of reduced absorption relative to the brain (range, M 6 to 16) having an irregular margin with an ameboid or frond-like contour. Mass effects upon the ventricular contours and displacement of midline structures are generally obvious, though they may be very slight in more infiltrating forms; such effects are generally greater than those produced by ischemic infarcts of equal volume, and the latter usually have smoother contours, although the absorption values may be similarly decreased. Calcific foci are much more readily identifiable on CT scans than on plain films, although the exact morphological pattern of calcification is not shown. Glioblastomas may be similar in appearance to astrocytomas (Fig. 1) but commonly show a heterogeneous pattern of absorption values in which ill-defined patches of greater density than the normal brain (M 18 to 35) are distributed throughout the lesion or occur in one area of it. These regions represent minor local hemorrhagic extravasation or areas of more densely compacted cells. The latter pattern can mimic hemorrhagic infarction quite closely, atlhough again the contour of the lesion tends to be smoother in infarction than in glioblastoma. In a small number of cases, it may be difficult to differentiate a glioma from an infarction on the initial CT scan. If the clinical presentation is equivocal, the CT scan should be repeated after an interval of 10 to 14 days; by then the edema accompanying an acute infarction will have subsided to some degree, while the neoplasm will generally appear unchanged or larger. Cystic changes are usually clearly indicated by low absorption values (M () to 14), representing the contained fluid (Fig. 2). Highly proteinaceous fluid in neoplastic cysts may occasionally be so similar to the brain in density that the cyst cannot be discriminated from the surrounding cerebral tissue.
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Fi g, 1. Glioblas toma of the left cerebra l hem ispher e , The CT sca n wa s obtained a short t ime bef ore death , Slices 13 m m t hick were scanned at 25° to the anatomi cal base line . f\ . Scan through the infe rio r po rtio ns of the frontal horns and the anterio r portion of the t hir d ve nt ricle. Posteriorl y , the sca n plane passed through th e Quadri gem inal plate a nd upper cere bellum . T he sca n shows co mpression of t he left fr ont al horn a nd th ird ventricle . with di sp lacement of th e se pt urn lucidu m and third ventricle 6-9 nu n to the ri ght of the midline . Small , patch y areas of a bno rmal absorption are sca t te red througho ut t he frontal lob e , the cor pus st ria t u m , and most of the temporal lo be. Ab sorption values in thi s region va ry from slight ly ahove to slight ly bel ow normal ; this was obvious during an a lysi s of the image on t he cat ho de-ray t ube but is difficult to sho w clearly in a print. The marked midline d islocation and foca l mass effect on the fro ntal horn a re sho wn re latively well. B. Brain slice ob tained at a utop sy , closely matchin g the sec t ion sho wn in Fi gure I, A. Widespread glioblas t om a was demonstrated in t he abnormal a reas referred t o a bove an d e xtended laterall y from t he wall of t he frontal horn an d thi rd ven tricle , A bo undary zo ne an terolate ra!ly, laterally, and posterola te rally consist ed primarily of react ive gliosis and edema , with a few possibly m ali gnant cells di stributed t hro ugho ut . Ab sor ption values d id not pe rmit d ist inct ion be tw een th is boundary zon e a nd th e a rea of ?;rOSS t umor , but the ge nera l corres pondence between t he scan a nd t he pathological findi ngs was re ma r ka bly good . C. CT sca n slice 1.3 cm above t ha t show n in Figure 1, A, clearly de mo ns t ra ti ng t he mass eflect ca use d by a n immed iately adjacent t umor impingin g u pon the frontal ho rn a nd t hird ventricle. The re is marked d islocation of the compresse d t hird ventricle to the ri ght. The temporal portion of th e mass shows a more st ri king de cre ase in a bsor pt ion values than in Fi gu re 1, A (p. 9 to 12 ), especially posterior ly . A hi ghl y irregula r , frond-lik e margin is apparent be tween the abnormal t issue and a pparen tl y norm al areas. Farther anterior ly , red uction of absorp t ion is less homogen eou s a n d less marked. Absorpt ion value s in the medial portion of th e t umor a re ba rel y d istingui shable from t he normal value s in t he co r pus st ria t um , but a heterogene ou s pattern may be detected. D . CT section 25 m m above th a t shown in Fi gure 1, C , a t the level of the markedl y comp ressed body of t he left la t era l ventricle . Reducti on in absorp tion is more st riking th rough out the tum or ar ea, th ou gh ag-ain with a he t erogene ous pattern resultin g from the pre sen ce of small, irregular islands of more absorbent tissue wit hin the le sion , The margin is again highly irregul ar . Abso rption valu es (p.) ra nge between 7 a nd 17. There a re no di screte ar eas in whi ch a bsor pt ion is redu ced enough to indi cate fra nk cavit a t ion.
T he role of intravenou s inj ection of contrast materi al (cont ra st enhancement ) in CT examinat ion is a most important cons idera t ion that re-
mains to be established pr ecisely.
Most sympt om-
atic gliomas are apparently identifiable on pl ain CT scans; however, the accuracy of different ial
Fig. 2. Cystic cerebellar astrocytoma in a 7-year-old girl with a three-week history of headaches and acute onset of bilateral sixth-nerve palsy one week before admission. Bilateral papillederna, right arm drift, truncal ataxia, and instability of gait with falling to the left were additional neurological findings. A. CT scan at an angle of 15 0 to the anatomical base line (the maximum angle obtainable) and extending through the orbital roof anteriorly and the midcerebellar region posteriorly shows a huge, rounded area of markedly diminished absorption with irregular margins occupying most of the left cerebellar hemisphere and extending several milIimeters to the right of the midline. General absorption values (/1) in this lesion ranged from 4 to 11, indicating a fluid-containing cyst. A large, irregular nodule of higher absorption (/1 11 to 14) projects posteriorIy into the cyst cavity from the left side. A narrow rim of tissue surrounds the cystic mass anterolaterally and posterolaterally. A narrow zone of heterogeneous absorption a few millimeters in width surrounds the cyst cavity. Adjacent to this in the anteromedial area is a flat, crescentic zone of decreased absorption 3 mm wide and displaced anteriorIy and to the right, consistent with a greatly compressed fourth ventricle. 99mTc brain images showed increased uptake in the left cerebellar region. Left vertebral angiography showed a large, avascular mass in the left cerebellar hemisphere. At surgery, viscous yellowish fluid was aspirated from the cyst, which did not clot on standing. During resection of the lesions, a narrow tumor layer was found around the cyst cavity in addition to the mural nodule. Histologically, the tumor was diagnosed as a grade I astrocytoma. B. Same tissue slice as in Figure 2, A but photographed at window M and level 13. The irregular wall of the cyst cavity and the large mural nodule are shown more clearly.
Fig. 3. Metastatic adenocarcinoma in a 58-year-old woman with carcinoma of the colon in whom grand mal seizures and mild right hemiparesis developed. The CT scan revealed two metastases, of which the larger is visible in this picture in the inferior portion of the right frontal lobe. This dense nodule had an absorption range of /1 18 to 32 and was surrounded by a large volume of markedly decreased absorption (/1 6 to 17), indicating perifocal edema. B. A second, somewhat smaller lesion was visible in the superior portion of the left cerebral hemisphere, at the junction of the frontal and parietal lobes. It was somewhat less dense than the nodule on the right (/1 15 to 25) and was again surrounded by a large volume of edema (/16 to 15). Angiography was not necessary, and the patient was referred directly for radiotherapy.
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Fig. 4. Metastatic hypernephroma in a 59-year-old man with a history of resected hypernephroma and evidence of rib metastases. The patient's history included progressive numbness of the left side of the body of one month duration, several focal motor seizures involving the left foot, and mild left hemiparesis. A. A plain CT scan revealed a large region of decreased absorption (IJ. 9 to 15) in the right frontal region, at the level of and compressing the right frontal horn and containing a small (less than 6 mm) focus of considerably increased absorption (IJ. 15 to 24). B. The scan was repeated following intravenous injection of 50 ml of Hypaque 60M. The quality of the scan was somewhat degraded by head motion, but there was no definite change in the volume of reduced absorption, a finding compatible with edema. However, the small, dense nodule now appeared considerably larger, measuring about 12 X 15 mm in diameter. A considerable proportion of this nodule, later diagnosed as metastatic hypernephroma, was apparently obscured on the plain scan by the large volume of surrounding edema, which had a lower absorption value. Following intravenous injection of contrast material, the resulting increase in the density of the blood in the vascular nodule set it apart from the surrounding edematous region. Additional metastatic lesions accompanied by large volumes of edema were demonstrated in the superior portions of the posterior right frontal lobe and the anterior right parietal lobe.
diagnosis (e.g., separation from infarcts and nonneoplastic cystic lesions) and the sensitivity of the examination in detecting earlier, still asymptomatic lesions can undoubtedly be increased by contrast enhancement. The same is true of metastases. However, there are disadvantages to the regular use of contrast enhancement. First, the use of 50-200 m! of intravenous contrast material changes the nature of the CT scan from a hazardfree procedure to one with a small but well-defined risk of possibly fatal reaction, even when the most modern resuscitative measures are applied promptly. Second, repeating the CT scan entirely or in part on the same day or later considerably increases the scheduling problems that are likely to remain severe until CT scanners are widely available. The alternative would be to perform a CT scan with contrast enhancement at the outset; however, this can lead to ambiguities in interpretation, especially when a large intravenous dose is given, and serious errors of diagnosis may result. Comparative Diagnostic Effectiveness of CT Scans in Glioma: Of the 3,5 patients with glioma scanned, only one gave a false-negative result. In
another case, pneumoencephalography indicated either perichiasmatic arachnoid adhesions or a very small optic chiasm glioma. This case has not yet been proved but is retained here because it is clear that very small tumors in the region of the optic chiasm and hypothalamus are likely to prove un diagnosable on CT scans. Two false-positive studies occurred, but these involved metastatic neoplasms and were seen early in the series. With greater experience, we would expect to diagnose both cases correctly. Thus CT scanning may be considered highly accurate in the diagnosis of glioma. Twenty-four of our 35 patients underwent radionuclide imaging; of these, 21 were positive and :3 were negative. CT scans were far superior in diagnosing the type and extent of lesion. Angiography was performed in 22 cases. CT scans were considered to be far superior in the diagnosis of glioma and its extent in 10, distinctly better in G, and approximately equal in 5. One patient with an angiographic diagnosis of glioma had a technically unsatisfactory CT scan due to motion. Twelve patients underwent pneumoencephal-
80
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Jan uar y IV7!)
Fig. 5. M etast atic mali gnant melanoma in a 53-year-old woman with a histo ry of malignant melanoma and recent onset' of r ight homony mous hem ian opsia. A. Plain CT scan at an an gle of 25° to th e base line a nd pass ing through t he pineal gland (t he den se 6-9-mm area in the midline ) dem onst rates a lar ge ovoid zone of markedly increased absorptio n (I' 22 to 34) in th e occipital lobe and extending into the pariet otemp oral region , containing a sma ller zone of lesser den sit y consiste nt with necrosis and surro unded by a narrow zone of dimi nished absorpt ion . B. Following int raven ous injecti on of 50 ml of Conr ay 60, a repeat scan at the same level shows a modest increase in a bsorpt ion (maximum, I' 38). The mass appears somewhat lar ger, suggesting th at par t of the per iphery had previously been obscured becau se of th e very low a bsorpt ion of the surrounding edema. TABLE
II :
CT Scans (35) Positive
32t
Negative
1
+ ?It
Technically 1 (motion) unsatisfactory
GLIOMAS
(35
CASE S)
Comparison Radio- Comparison with with nuclide AngiPneumoImages ography encephalogra phy (24) (22) * (12) * 21 3
°
»10 > 6 =5
«1 0
»1 >5 =
2
= CT distinctly superior to an giography/ pneumoencephalogra phy . § = CT approximately equal to angiogra phy/ pneumoencephalography. « = CT far inferior to ang iogr aph y / pneumoencephalography. t Error in interpretation regarding t he nature of the tumor : 2 cases were diagnosed as metastases. t Suspected optic chiasm glioma (unp roved) .
ography. CT scans were considered to be far superior in I , distinctly better in 5, equal in 2, somewhat less informative in 2, an d far less informative in 1. One CT scan was negative in a patient suspect ed of having a small optic chiasm glioma ( T A B L E II). Metastatic I ntracerebral Neoplasms
Metastatic adenocarcinomas are seen on CT scans as dense nodules of various sizes with an absorpt ion range (p,) of from 12-15 to 28-30, sur-
rounded by a very large volume of diminished absorption cau sed by edema (p, 4 to 14) (Fig. 3). The sm allest metastatic nodules identified have been on the order of 6-9 mm. In a number of cases , scanning before and after intravenous injection of cont r ast material has revealed a distinct increase in absorption by those nodules which have an in trinsic circulation, making the smaller nodules easier to identify (Fig. 4). Very small nodules, occupying only a fraction of the full thickness of the slice and surrounded by edem a of low density, may be made inconspicuous by ab sorption averaging until the den sity is increased by 'cont rast material. The degree to which den sity is increased is proportional to the blood level of iodine and the vascularity of the nodule. We have demonstrated a considerable increase in the den sit y of both small and large nodules of adenocarcinoma by inj ection of contrast material, usually 40 to 50 ml . This method is more sensitive than an giography in revealing tumor vascular it y. M etastatic melanomas also tend to have initially high ab sorption values, somet ime s in the high 30s, a feature st rongly suggest ive of tumor hemorrhage (F ig. 5). A case of metastatic angiosarcoma with hemorrhage also showed high absorption values (F ig. 6). In other cases, a considerable increase in density following intravenous injection of contrast material demonstrated the marked vascularity of the tumor. Larger nodules of metastatic
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Fig. 6. Multiple malignant angiosarcomas in a 57-year-old man with a two-week history of dysarthria and right hemiparesis preceded by numbness and tingling in the right arm. Bilateral common carotid angiography indicated avascular cerebral masses in the left anterior parietal parasagittal region and the right frontal opercular area. As neither vertebral artery could be catheterized, the posterior circulation was studied by injection of the left subclavian artery and right retrograde brachial angiography. These studies suggested a diffuse posterior fossa mass effect without lateralization. A 99mTc brain image was interpreted as showing foci of abnormal activity in the left occipital region and possibly in the right parasagittal region. A C'T brain scan obtained on the same day as the radionuclide image revealed many nodular lesions, including 9 foci in the cerebral hemispheres and one in the cerebellum. The largest nodules measured 21 and 24 mm and lay superiorly in the left parietal and right posterior frontal lobes. The remainder varied from a few millimeters up to approximately 15 mm in diameter. All of the lesions had high absorption values, generally ranging from the low 20s to the high 30s and low 40s. These findings led to a diagnosis of numerous metastatic nodules associated with hemorrhagic necrosis. There were small perifocal zones of diminished absorption, consistent with edema. Melanoma and hypernephroma were considered the most likely possibilities. At autopsy, histological examination revealed angiosarcoma associated with large amounts of hernorrhage into the foci. No primary lesion was found. A. CT section at the level of the frontal horns shows a IS-mm dense nodule in the left frontal lobe with a minimal associated mass effect. Calcifications in the choroid glomi of the lateral ventricles are symmetrically disposed posteriorly. Behind these in each occipital lobe are irregular regions of increased density merging with the cerebral cortex. B. Autopsy brain slice corresponding approximately to the level of the previous CT scan. The left frontal lesion has evidently become a little larger since the scan was obtained. Two separate small hemorrhagic nodules, impossible to discriminate as separate lesions on the CT scan, are visible in the right occipital lobe. The 5-mm nodule just behind the glomus of the right lateral ventricle cannot be identified on the CT scan, even in retrospect. Small lesions are visible in the left occipital lobe. C. CT scan at a level 13 mm above that in Figure 6, A. The left frontal nodule is clearly visible. A somewhat smaller nodule surrounded by a zone of decreased density due to edema is also readily visible in the right frontal lobe in this slice. A slightly more irregular lesion of similar size is evident in the right frontoparietal opercular region and is also surrounded by edema. Only a single dense oval area of moderate size is apparent in the right occipital region. D. Autopsy brain slice corresponding approximately to the level scanned in Figure 6, C. The right and left frontal nodules are clearly shown. The slice passes just below the right lateral lesion, which is suggested by a small area of staining. Four discrete contiguous nodules not separately discriminated on the CT scan are seen in the right occipital lobe.
82
PAUL
TABLE
Positive Nega t ive
*» >
=
CT Scans (24)
R adionuclide Images (12)
24t
11 (false diagnosis of a sing le lesion in 3 cases ) 1
o
F.
Ill :
J. N EW
AND O T H E RS
MRTASTASES
(24
Comparison with Angiography * (12)
»
8 (false diagnosis of a sin gle lesion in 1 case )
J a nu ar y 197 5
CASES )
Comparison with Pn eumoencephalography Pneumoen cephalography " Ventriculography ( 1) (1)
+
No diagnosis
"Cerebellar mass"
>4
CT far superior t o angiography/ pneumoencephalogra phy .
= CT dist inctly su perio r t o an giogr aph yj pneumoencep ha logra phy .
t E rror in inter pr et at ion : 2 cases were diagnosed as glioblast om a.
Fi g. 7. Squamous -cell metastases in a 68-year-old wom an with car cin oma of the laryn x who wa s t reat ed ' by lar yngectomy and irr adi at ion follo wed by wedge resecti on of pulmonary meta st ases. A CT scan obta ined be cau se of recent pro gre ssive left hemiparesis reveal ed a ro unded volume of decre ased a bsorp tion (I' 4 to 14) me asuring slight ly greater th an 5 cm in t he an ter ior por tion of th e righ t frontal lobe , wit h sma ll foci of high a bsorptio n scattered wit hin a gener al back gr ound of lower a b sorp tion. T he margins of the lesion wer e relatively re gul ar. A smaller lesion with som ewh at more irregul ar margins a nd a similar a bsorpt ion range was de m onst rated in t he left t em por al lobe and t he region of the left in sul a . A " mTc bra in image t aken the sa me day as the CT scan was negative. The patien t was referred for 'ra diot hera py withou t the need for a ngiogra phy or pneumoencep hal ogra phy .
adenocarcinoma and melanoma may contain irregular, less dense central areas repr esenting ti ssue necrosis (F ig. 5). In contrast, metastatic squa mou s-cell carcinoma genera lly presents a low density relative to that of the brain (IJ- 4 to ] 2-14) and rather smoothly rounded contours with little or no surrounding edema (F ig. 7). In our series, metastatic undifferen tiated carcinoma has resembled squamous-cell carcinoma. A sing le case of rhabdomyosarcoma metastatic to the cerebellum reve aled low absorption values (IJ- 8 to 14). Metastases arid gliomas treated by radiation therapy and chemotherapy may show decreased absorption values on repeat CT examination. Comparative Diagnostic A ccuracy of CT Scans in Cerebral M etastases: There were no false-positive diagnoses among th e 24 cas es of cerebral metastases
Fi g. S. Large men ingiom a of moder at e sca n den sit y in the sp henoid win g and planu m sphen oida le in a 52-y ea r-old woma n wh o had h ad a ra dical maste ct omy (j ye ars ago. F ive years ago she had had intermittent loss of vision in t he left eye followed by permanent visu al loss. M ore recent difficulty with vision in the right eye led t o inv est igati on for sus picion of metastatic carcin om a . Pl ain films of the skull reve al ed chr onic er osion of the upper portion of t he dorsum sellae and ind icated sligh t hyperostosis of the planum sphenoidale . A 99mTc brain im age taken three weeks before the C T scan reveale d a bnorm al uptake ad jacent t o t he left sph en oid wing , thought t o be in the left fr ontal lobe a nd re garded as cons isten t with metast ati c di sease. A plain CT sca n revealed a la rge , rounded vo lume of in cre ased abso r ption occup yi ng mu ch of th e ante rio r portion of t he left middle fossa and ex tending acro ss t he m idline supe rio rl y a nd t o the ri gh t into the inf erior fr ontal r egion and high supras ellar region . The left fr ontal hor n was mark edly com presse d an d t he th ird ve nt r icle was disp lace d severa l rnillim et ers t o th e right. T he m ass measu red 5 cm in antero pos te r ior di am eter and 6 cm t ra nsver sely a nd was rela tively hom ogen eou s in te xt ure (p. 20 t o 30 ). Bilatera l ca ro t id and left ver tebral a ngiograp hy 'clearly reveal ed an ovo id mass in t hese regions, sho wing the charac terist ic vascula r supp ly and pat tern of a men in giom a 7 cm in m aximum di ameter. T his case illu strates the fact t ha t CT scannin g does not obviate the need for good preliminary plain-film exa min at ion , which can pr ov ide ext remely useful in for mat ion re gard ing the presence or a bsen ce of a chro nic in crease in intra cra nial pressure, detail s of bone changes ind icati ve of t he in tr acranial process , and infor mat ion regard ing th e textur e a nd pa tte rn of in t ra cranial ca lcificati on s, all of wh ich are bey ond t he resolution of presen t CT exami na ti on . The con figu rat ion of t he sku ll and the presence or ab sen ce of pla in- film findings assist in planni n g an opt im al individual CT sca n , and t he scan and plain-fil m st ud y should be inter pret ed together.
in this series, Two cases seen earlier in the series were thought to represent glioblastoma, an err or we would not make today. Thus we feel that with som e experience, the accuracy of CT scanning in the identification of mctast ases should approach
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Fig. 9. Plain CT scan reveals a meningioma of moderate size and relatively low density in the left sphenoid wing in a 39-year-old woman with increasing headaches and intermittent diplopia of several months duration as well as visual difficulty and bilateral papilledema for several weeks. A radionuclide image obtained at another center revealed uptake in the left frontotemporal region, and carotid angiography demonstrated a highly vascular mass 3 cm in diameter in the left middle fossa. consistent with a meningioma of the lateral sphenoid wing. The left temporal mass effect was so striking that the possibility of a glioma was entertained. A. The plain CT scan revealed a rather poorly defined region of abnormal absorption (range, p. 17 to 23) in the left middle fossa. In the central portion of this zone was a small region with an absorption range of 19-27. B. A repeat scan following intravenous injection of 50 ml of Hypaque 60M revealed a relatively sharply defined homogeneous zone of markedly increased absorption (p. 23 to 39) measuring 3 cm in diameter extending posteriorly from the sphenoid ridge. Scans at higher levels, both plain and contrast-enhanced, revealed a large volume of diminished absorption (range. p. 7 to 15) in the region of the temporal lobe, deep frontal white matter, and corpus striatum, indicating marked perifocal edema. This explained the temporal lobe mass effect seen at angiography. Both Cl' scans revealed marked mass effects in the lateral and third ventricles.
100%, but only in patients with related neurological signs or symptoms (TABLE Ill). Radionuclide images were obtained in 12 cases; they were positive in 11 and negative in 1. However, in 3 of the positive cases only a single lesion was seen, whereas multiple lesions were demonstrated on the CT scans. Angiography was performed in 12 cases. The CT scan was considered to be far superior in diagnosing the presence, size, and distribution of metastases in 7 and distinctly better in 4. In one case of multiple metastases revealed by the CT scan, only a single mass was identified by angiography; multiplicity was always demonstrated better by the CT scan. Pneumoencephalography was performed in only 2 cases. In one case, no diagnosis was obtained. In the other, ventricular injection of gas was helpful in establishing the correct diagnosis of a cerebellar mass producing hydrocephalus.
Meningiomas Meningiomas are frequently though not invariably of moderate density, with M values ranging from the 20s to the 40s (Fig. 8). These are not
remarkably different from the values seen in intracerebral hematoma, and confusion is possible if the site of the lesion is atypical. However, even in these cases, the clinical context should serve to distinguish the two lesions. A repeat scan following intravenous injection of contrast material should permit differentiation, as there will generally be an obvious increase in the density of meningiomas in the lower and medium density ranges and no increase in that of hematomas. In other cases, the plain CT scan density is only a little higher than that of the brain. In general, when the initial density of a meningioma is relatively low, it is markedly increased by injection of contrast material due to the vascularity of the tumor (Fig. 9). In many cases, the plain CT density of a meningioma is very high, ranging up to as much as 90 or more, due to psammomatous calcification (Fig. 10). In such cases, the calcified regions show little or no further increase in density following injection of contrast material. Calcification can be diagnosed on the CT scan (M> 60) even when none is visible on the plain film. Whether the initial density is high or low, it is generally homogeneous, although large lobulated tumors
84
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January 197;)
Fig. 10. Three posterior fossa meningiomas containing psammomatous calcification in a 57-year-old woman admitted because of a suspected mass lesion in the posterior fossa. A radionuclide brain image revealed areas of abnormal uptake in the right and left sides of the posterior fossa. Plain films did not show calcification. Cerebral angiography revealed considerable dilatation of the lateral ventricle and evidence of an avascular mass (thought to be extracerebral) in the anterolateral portion of the posterior fossa in the cerebellopontine angle cistern. Another avascular mass was seen in the left side of the posterior fossa. A. CT scans obtained before and immediately following intravenous injection of 50 ml of Hypaque 60M revealed a large, homogeneous area of markedly increased absorption in the area of the right angle cistern (p. 25 to 75 on the plain scan, 26 to 85 with Hypaque ). A huge homogeneous lobulated density occupied most of the left half of the posterior fossa (p. 33 to 80 on the plain scan, 36 to 95 with Hypaque). The superior portions of this mass showed f1. values extending up to 170. B. A third lesion 2.5 cm in maximum diameter was demonstrated just below the tentorium posteriorly on the right side. This lesion could not be identified on either the gamma camera image or the angiogram. The homogeneous appearance of all three lesions, the absorption values indicating diffuse calcification within the lesions, and the slight additional increase in density following the injection of contrast material led to a confident CT scan diagnosis of meningioma. Radionuclide studies and angiography gave no indication of the nature of the lesions and even failed to show one of them. The degree and cause of obstructive hydrocephalus were clearly shown on the CT scan.
TABLE
Positive Negative
IV:
MENINGIOMAS
CT Scans (11)
Radionuclide Images (11)
lIt
9
0
2+
(11
CASES)
Comparison Comparison with with AngiPneumoography* encephalogniphy* (9) (1) »3
=3
? Arnold-Chiari malformation
Computed Tomography with the EMI Scanner in the Diagnosis of Primary and Metastatic Intracranial Neoplasms1 Paul F. J. New, M.D., William R. Scott, M.D.,2 James A. Schnur, M.D.,2 Kenneth R. Davis, M.D.,2 Juan M. Taveras, M.D., and Fred H. Hochberg, M.D. The findings and diagnostic results in 600 examinations of primary and metastatic intracranial neoplasms performed at one hospital with the EMI scanner are presented and the effectiveness of this method is compared with that of radionuc1ide imaging, cerebral angiography, and pneumoencephalography. The computed scan proved to be highly reliable in the diagnosis of glioma, cerebral metastases, meningioma, and acoustic neuroma. INDEX TERMS: Brain Neoplasms, diagnosis • Brain Neoplasms, metastases • Computed Tomography • Glioma. Meninges, neoplasms. Neurinoma Radiology 114:75-87, January 1975
OMPUTED tomography (CT) with the EMI scanner is a relatively new method of brain study that has been described and discussed in several articles within the past two years (1-8). In this technique the cranium is scanned 180 times at different angles by a narrow x-ray beam. Differential absorption by tissues in contiguous slices is calculated by a computer and presented as a series of images of the structure of the brain. This method is capable of revealing a remarkable amount of anatomical and pathological information and is rapidly gaining wide acceptance as an important and clinically useful modality. We now wish to review in detail the results of computed tomographic studies in our initial series of 600 patients.
TABLE
C
I:
RESULTS OF
600
EXAMINATIONS
No. of Examinations Normal Atrophic disease Porencephaly Obstructive hydrocephalus (nontumorous) Mixture of normal-pressure hydrocephalus and atrophy Infarct Ischemic (59 cases) Hemorrhagic (4 cases) Extradural hematoma Subdural hematoma Intracranial hematoma Hypertensive supratentorial (14 cases) infratentorial (2 cases) Traumatic (4 cases) Arteriovenous malformation (4 cases) Aneurysm (1 case) Coumadin (1 case) Abscess Glioma Medulloblastoma Metastases Meningioma Acoustic neuroma Pineal area tumor Craniopharyngioma Pituitary adenoma Miscellaneous lesions Not proved Technically unsatisfactory
MATERIAL Our patients ranged between 3 days and 90 years of age. Several patients had more than one type of lesion, and classification was based on the clinically dominant condition (TABLE I). Many patients were scanned more than once, often 3 or 4 times, for a number of reasons: (a) unsatisfactory initial scans due to excessive motion, (b) for followup of the progress of a lesion, including irradiated tumors, and (c) diagnosis of suspected postoperative or other complications. Eleven per cent of the examinations were classified as normal. One patient seen early in the series was thought to have a normal CT scan, whereas angiography and radionuclide images indicated infarction. Subsequent review revealed evidence of infarction on the CT scan as well.
68 94 6 19
% of Total Examinations 11 16 3
3 77
13
2
12 35
6
4
43
7
1
26 14 8 11 5 5
4
32 118 17 600
20 3
83%
(9 groups)
In one 45-year-old man with a three-year history of temporal-lobe seizures, two CT scans taken five months apart revealed no convincing evidence of pathology, although pneumoencephalography had suggested a mass in the left temporal lobe. A left carotid angiogram was interpreted as probably
1 From the Departments of Radiology (P. F. J. N., W. R. S., J. A. S., K. R. D., J. M. T.) and Neuropathology (F. H. H.), Massachusetts General Hospital and Harvard Medical School, Boston, Mass. Accepted for publication in September 1974. Presented at the Tenth International Symposium Neuroradiologicum, Punta del Este, Uruguay, March 10-16, 1974. 2 Supported in part by NINDS Neuroradiology Special Fellowships 5F 11 NS 02458-02 (W. R. S.), 5F 11 NS 02586-02 (J. A. S.), and 5F 11 NS 02622-02 (K. R. D.). sjh
75
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normal. Multiple serum samples were positive for glioma antigen, and an en bloc medial temporal lobectomy was performed by Dr. William H. Sweet. No definite histological abnormality was identified in the portion of the resected specimen subjected to neuropathological examination. However, tissue cultures from an adjacent portion of the specimen supported growth of cells, 41% of which were multinucleated (as described by Dr. Paul L. Kornblith) and which were shown by electron microscopy to contain many glial-type fibrils measuring 90-100 A. The cells have continued to grow in a rapid and vigorous fashion, more compatible with tumor than with normal brain cells. In another patient with suspected glioma of the optic chiasm, the CT scan was unrevealing, but pneumoencephalography and laminagraphy revealed minor changes in the area of the optic chiasm, suggesting a very small glioma. Proof is lacking to date. A diagnosis of anatomical normality on the CT scan was not disproved by other radiological tests in any other case in this series, save for small structural abnormalities of the cerebral arteries, such as atheromas and anuerysms. Various forms of atrophy and degenerative disease were seen in 16% of cases, and 55% of these patients had dementia. Nontumorous obstructive hydrocephalus was found in 3% of cases, primarily patients with dementia. In all but 3 cases, atrophic brain disease was easily differentiated from occult obstructive hydrocephalus. In 2, elements of both conditions seemed to be present, and a mixed pattern was also indicated by radionuclide studies of cerebrospinal fluid flow in these cases. Cerebral or cerebellar infarcts were seen in 13% of patients of various ages. The ratio of ischemic to hemorrhagic infarction was 15 to 1. Intracerebral hematomas of various types were seen in 6% of cases. Seven per cent of the entire series of patients had glioma and 4% had metastases to the brain. Twenty per cent could not be classified satisfactorily owing to insufficient proof of pathology in the relatively short follow-up period involved. Three per cent of the examinations proved to be technically unsatisfactory, mostly due to motion, with a few due to the presence of gas, Pantopaque, or metal surgical structures. In most of the former cases, a subsequent study was satisfactory. We have been able to reduce effectively or eliminate head movement during CT scanning by using a dental plate and mold as will be described elsewhere (9). In one case, an acromegalic patient's head was too large to fit through the retaining ring of the scanner.
January 1975
Postoperative changes per se were not a serious problem in re-evaluation by CT scanning unless a large number of sizable metal surgical clips, burr hole plugs, or the valves of certain ventricular shunts were present, as these tend to produce more or less severe artifacts which obscure anatomical detail. On the other hand, the tissue changes produced by surgery do not affect CT scans obtained long afterward as they do postoperative radionuclide images. Also, edema, contusion, or hematoma can be correctly attributed to trauma to the scalp and cranial vault without the confusion of intracranial diagnosis that sometimes occurs with radionuclide images.
Gliomas A low- or intermediate-grade astrocytoma typically appears as an area of reduced absorption relative to the brain (range, M 6 to 16) having an irregular margin with an ameboid or frond-like contour. Mass effects upon the ventricular contours and displacement of midline structures are generally obvious, though they may be very slight in more infiltrating forms; such effects are generally greater than those produced by ischemic infarcts of equal volume, and the latter usually have smoother contours, although the absorption values may be similarly decreased. Calcific foci are much more readily identifiable on CT scans than on plain films, although the exact morphological pattern of calcification is not shown. Glioblastomas may be similar in appearance to astrocytomas (Fig. 1) but commonly show a heterogeneous pattern of absorption values in which ill-defined patches of greater density than the normal brain (M 18 to 35) are distributed throughout the lesion or occur in one area of it. These regions represent minor local hemorrhagic extravasation or areas of more densely compacted cells. The latter pattern can mimic hemorrhagic infarction quite closely, atlhough again the contour of the lesion tends to be smoother in infarction than in glioblastoma. In a small number of cases, it may be difficult to differentiate a glioma from an infarction on the initial CT scan. If the clinical presentation is equivocal, the CT scan should be repeated after an interval of 10 to 14 days; by then the edema accompanying an acute infarction will have subsided to some degree, while the neoplasm will generally appear unchanged or larger. Cystic changes are usually clearly indicated by low absorption values (M () to 14), representing the contained fluid (Fig. 2). Highly proteinaceous fluid in neoplastic cysts may occasionally be so similar to the brain in density that the cyst cannot be discriminated from the surrounding cerebral tissue.
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Fi g, 1. Glioblas toma of the left cerebra l hem ispher e , The CT sca n wa s obtained a short t ime bef ore death , Slices 13 m m t hick were scanned at 25° to the anatomi cal base line . f\ . Scan through the infe rio r po rtio ns of the frontal horns and the anterio r portion of the t hir d ve nt ricle. Posteriorl y , the sca n plane passed through th e Quadri gem inal plate a nd upper cere bellum . T he sca n shows co mpression of t he left fr ont al horn a nd th ird ventricle . with di sp lacement of th e se pt urn lucidu m and third ventricle 6-9 nu n to the ri ght of the midline . Small , patch y areas of a bno rmal absorption are sca t te red througho ut t he frontal lob e , the cor pus st ria t u m , and most of the temporal lo be. Ab sorption values in thi s region va ry from slight ly ahove to slight ly bel ow normal ; this was obvious during an a lysi s of the image on t he cat ho de-ray t ube but is difficult to sho w clearly in a print. The marked midline d islocation and foca l mass effect on the fro ntal horn a re sho wn re latively well. B. Brain slice ob tained at a utop sy , closely matchin g the sec t ion sho wn in Fi gure I, A. Widespread glioblas t om a was demonstrated in t he abnormal a reas referred t o a bove an d e xtended laterall y from t he wall of t he frontal horn an d thi rd ven tricle , A bo undary zo ne an terolate ra!ly, laterally, and posterola te rally consist ed primarily of react ive gliosis and edema , with a few possibly m ali gnant cells di stributed t hro ugho ut . Ab sor ption values d id not pe rmit d ist inct ion be tw een th is boundary zon e a nd th e a rea of ?;rOSS t umor , but the ge nera l corres pondence between t he scan a nd t he pathological findi ngs was re ma r ka bly good . C. CT sca n slice 1.3 cm above t ha t show n in Figure 1, A, clearly de mo ns t ra ti ng t he mass eflect ca use d by a n immed iately adjacent t umor impingin g u pon the frontal ho rn a nd t hird ventricle. The re is marked d islocation of the compresse d t hird ventricle to the ri ght. The temporal portion of th e mass shows a more st ri king de cre ase in a bsor pt ion values than in Fi gu re 1, A (p. 9 to 12 ), especially posterior ly . A hi ghl y irregula r , frond-lik e margin is apparent be tween the abnormal t issue and a pparen tl y norm al areas. Farther anterior ly , red uction of absorp t ion is less homogen eou s a n d less marked. Absorpt ion value s in the medial portion of th e t umor a re ba rel y d istingui shable from t he normal value s in t he co r pus st ria t um , but a heterogene ou s pattern may be detected. D . CT section 25 m m above th a t shown in Fi gure 1, C , a t the level of the markedl y comp ressed body of t he left la t era l ventricle . Reducti on in absorp tion is more st riking th rough out the tum or ar ea, th ou gh ag-ain with a he t erogene ous pattern resultin g from the pre sen ce of small, irregular islands of more absorbent tissue wit hin the le sion , The margin is again highly irregul ar . Abso rption valu es (p.) ra nge between 7 a nd 17. There a re no di screte ar eas in whi ch a bsor pt ion is redu ced enough to indi cate fra nk cavit a t ion.
T he role of intravenou s inj ection of contrast materi al (cont ra st enhancement ) in CT examinat ion is a most important cons idera t ion that re-
mains to be established pr ecisely.
Most sympt om-
atic gliomas are apparently identifiable on pl ain CT scans; however, the accuracy of different ial
Fig. 2. Cystic cerebellar astrocytoma in a 7-year-old girl with a three-week history of headaches and acute onset of bilateral sixth-nerve palsy one week before admission. Bilateral papillederna, right arm drift, truncal ataxia, and instability of gait with falling to the left were additional neurological findings. A. CT scan at an angle of 15 0 to the anatomical base line (the maximum angle obtainable) and extending through the orbital roof anteriorly and the midcerebellar region posteriorly shows a huge, rounded area of markedly diminished absorption with irregular margins occupying most of the left cerebellar hemisphere and extending several milIimeters to the right of the midline. General absorption values (/1) in this lesion ranged from 4 to 11, indicating a fluid-containing cyst. A large, irregular nodule of higher absorption (/1 11 to 14) projects posteriorIy into the cyst cavity from the left side. A narrow rim of tissue surrounds the cystic mass anterolaterally and posterolaterally. A narrow zone of heterogeneous absorption a few millimeters in width surrounds the cyst cavity. Adjacent to this in the anteromedial area is a flat, crescentic zone of decreased absorption 3 mm wide and displaced anteriorIy and to the right, consistent with a greatly compressed fourth ventricle. 99mTc brain images showed increased uptake in the left cerebellar region. Left vertebral angiography showed a large, avascular mass in the left cerebellar hemisphere. At surgery, viscous yellowish fluid was aspirated from the cyst, which did not clot on standing. During resection of the lesions, a narrow tumor layer was found around the cyst cavity in addition to the mural nodule. Histologically, the tumor was diagnosed as a grade I astrocytoma. B. Same tissue slice as in Figure 2, A but photographed at window M and level 13. The irregular wall of the cyst cavity and the large mural nodule are shown more clearly.
Fig. 3. Metastatic adenocarcinoma in a 58-year-old woman with carcinoma of the colon in whom grand mal seizures and mild right hemiparesis developed. The CT scan revealed two metastases, of which the larger is visible in this picture in the inferior portion of the right frontal lobe. This dense nodule had an absorption range of /1 18 to 32 and was surrounded by a large volume of markedly decreased absorption (/1 6 to 17), indicating perifocal edema. B. A second, somewhat smaller lesion was visible in the superior portion of the left cerebral hemisphere, at the junction of the frontal and parietal lobes. It was somewhat less dense than the nodule on the right (/1 15 to 25) and was again surrounded by a large volume of edema (/16 to 15). Angiography was not necessary, and the patient was referred directly for radiotherapy.
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Fig. 4. Metastatic hypernephroma in a 59-year-old man with a history of resected hypernephroma and evidence of rib metastases. The patient's history included progressive numbness of the left side of the body of one month duration, several focal motor seizures involving the left foot, and mild left hemiparesis. A. A plain CT scan revealed a large region of decreased absorption (IJ. 9 to 15) in the right frontal region, at the level of and compressing the right frontal horn and containing a small (less than 6 mm) focus of considerably increased absorption (IJ. 15 to 24). B. The scan was repeated following intravenous injection of 50 ml of Hypaque 60M. The quality of the scan was somewhat degraded by head motion, but there was no definite change in the volume of reduced absorption, a finding compatible with edema. However, the small, dense nodule now appeared considerably larger, measuring about 12 X 15 mm in diameter. A considerable proportion of this nodule, later diagnosed as metastatic hypernephroma, was apparently obscured on the plain scan by the large volume of surrounding edema, which had a lower absorption value. Following intravenous injection of contrast material, the resulting increase in the density of the blood in the vascular nodule set it apart from the surrounding edematous region. Additional metastatic lesions accompanied by large volumes of edema were demonstrated in the superior portions of the posterior right frontal lobe and the anterior right parietal lobe.
diagnosis (e.g., separation from infarcts and nonneoplastic cystic lesions) and the sensitivity of the examination in detecting earlier, still asymptomatic lesions can undoubtedly be increased by contrast enhancement. The same is true of metastases. However, there are disadvantages to the regular use of contrast enhancement. First, the use of 50-200 m! of intravenous contrast material changes the nature of the CT scan from a hazardfree procedure to one with a small but well-defined risk of possibly fatal reaction, even when the most modern resuscitative measures are applied promptly. Second, repeating the CT scan entirely or in part on the same day or later considerably increases the scheduling problems that are likely to remain severe until CT scanners are widely available. The alternative would be to perform a CT scan with contrast enhancement at the outset; however, this can lead to ambiguities in interpretation, especially when a large intravenous dose is given, and serious errors of diagnosis may result. Comparative Diagnostic Effectiveness of CT Scans in Glioma: Of the 3,5 patients with glioma scanned, only one gave a false-negative result. In
another case, pneumoencephalography indicated either perichiasmatic arachnoid adhesions or a very small optic chiasm glioma. This case has not yet been proved but is retained here because it is clear that very small tumors in the region of the optic chiasm and hypothalamus are likely to prove un diagnosable on CT scans. Two false-positive studies occurred, but these involved metastatic neoplasms and were seen early in the series. With greater experience, we would expect to diagnose both cases correctly. Thus CT scanning may be considered highly accurate in the diagnosis of glioma. Twenty-four of our 35 patients underwent radionuclide imaging; of these, 21 were positive and :3 were negative. CT scans were far superior in diagnosing the type and extent of lesion. Angiography was performed in 22 cases. CT scans were considered to be far superior in the diagnosis of glioma and its extent in 10, distinctly better in G, and approximately equal in 5. One patient with an angiographic diagnosis of glioma had a technically unsatisfactory CT scan due to motion. Twelve patients underwent pneumoencephal-
80
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AND OTHERS
Jan uar y IV7!)
Fig. 5. M etast atic mali gnant melanoma in a 53-year-old woman with a histo ry of malignant melanoma and recent onset' of r ight homony mous hem ian opsia. A. Plain CT scan at an an gle of 25° to th e base line a nd pass ing through t he pineal gland (t he den se 6-9-mm area in the midline ) dem onst rates a lar ge ovoid zone of markedly increased absorptio n (I' 22 to 34) in th e occipital lobe and extending into the pariet otemp oral region , containing a sma ller zone of lesser den sit y consiste nt with necrosis and surro unded by a narrow zone of dimi nished absorpt ion . B. Following int raven ous injecti on of 50 ml of Conr ay 60, a repeat scan at the same level shows a modest increase in a bsorpt ion (maximum, I' 38). The mass appears somewhat lar ger, suggesting th at par t of the per iphery had previously been obscured becau se of th e very low a bsorpt ion of the surrounding edema. TABLE
II :
CT Scans (35) Positive
32t
Negative
1
+ ?It
Technically 1 (motion) unsatisfactory
GLIOMAS
(35
CASE S)
Comparison Radio- Comparison with with nuclide AngiPneumoImages ography encephalogra phy (24) (22) * (12) * 21 3
°
»10 > 6 =5
«1 0
»1 >5 =
2
= CT distinctly superior to an giography/ pneumoencephalogra phy . § = CT approximately equal to angiogra phy/ pneumoencephalography. « = CT far inferior to ang iogr aph y / pneumoencephalography. t Error in interpretation regarding t he nature of the tumor : 2 cases were diagnosed as metastases. t Suspected optic chiasm glioma (unp roved) .
ography. CT scans were considered to be far superior in I , distinctly better in 5, equal in 2, somewhat less informative in 2, an d far less informative in 1. One CT scan was negative in a patient suspect ed of having a small optic chiasm glioma ( T A B L E II). Metastatic I ntracerebral Neoplasms
Metastatic adenocarcinomas are seen on CT scans as dense nodules of various sizes with an absorpt ion range (p,) of from 12-15 to 28-30, sur-
rounded by a very large volume of diminished absorption cau sed by edema (p, 4 to 14) (Fig. 3). The sm allest metastatic nodules identified have been on the order of 6-9 mm. In a number of cases , scanning before and after intravenous injection of cont r ast material has revealed a distinct increase in absorption by those nodules which have an in trinsic circulation, making the smaller nodules easier to identify (Fig. 4). Very small nodules, occupying only a fraction of the full thickness of the slice and surrounded by edem a of low density, may be made inconspicuous by ab sorption averaging until the den sity is increased by 'cont rast material. The degree to which den sity is increased is proportional to the blood level of iodine and the vascularity of the nodule. We have demonstrated a considerable increase in the den sit y of both small and large nodules of adenocarcinoma by inj ection of contrast material, usually 40 to 50 ml . This method is more sensitive than an giography in revealing tumor vascular it y. M etastatic melanomas also tend to have initially high ab sorption values, somet ime s in the high 30s, a feature st rongly suggest ive of tumor hemorrhage (F ig. 5). A case of metastatic angiosarcoma with hemorrhage also showed high absorption values (F ig. 6). In other cases, a considerable increase in density following intravenous injection of contrast material demonstrated the marked vascularity of the tumor. Larger nodules of metastatic
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Fig. 6. Multiple malignant angiosarcomas in a 57-year-old man with a two-week history of dysarthria and right hemiparesis preceded by numbness and tingling in the right arm. Bilateral common carotid angiography indicated avascular cerebral masses in the left anterior parietal parasagittal region and the right frontal opercular area. As neither vertebral artery could be catheterized, the posterior circulation was studied by injection of the left subclavian artery and right retrograde brachial angiography. These studies suggested a diffuse posterior fossa mass effect without lateralization. A 99mTc brain image was interpreted as showing foci of abnormal activity in the left occipital region and possibly in the right parasagittal region. A C'T brain scan obtained on the same day as the radionuclide image revealed many nodular lesions, including 9 foci in the cerebral hemispheres and one in the cerebellum. The largest nodules measured 21 and 24 mm and lay superiorly in the left parietal and right posterior frontal lobes. The remainder varied from a few millimeters up to approximately 15 mm in diameter. All of the lesions had high absorption values, generally ranging from the low 20s to the high 30s and low 40s. These findings led to a diagnosis of numerous metastatic nodules associated with hemorrhagic necrosis. There were small perifocal zones of diminished absorption, consistent with edema. Melanoma and hypernephroma were considered the most likely possibilities. At autopsy, histological examination revealed angiosarcoma associated with large amounts of hernorrhage into the foci. No primary lesion was found. A. CT section at the level of the frontal horns shows a IS-mm dense nodule in the left frontal lobe with a minimal associated mass effect. Calcifications in the choroid glomi of the lateral ventricles are symmetrically disposed posteriorly. Behind these in each occipital lobe are irregular regions of increased density merging with the cerebral cortex. B. Autopsy brain slice corresponding approximately to the level of the previous CT scan. The left frontal lesion has evidently become a little larger since the scan was obtained. Two separate small hemorrhagic nodules, impossible to discriminate as separate lesions on the CT scan, are visible in the right occipital lobe. The 5-mm nodule just behind the glomus of the right lateral ventricle cannot be identified on the CT scan, even in retrospect. Small lesions are visible in the left occipital lobe. C. CT scan at a level 13 mm above that in Figure 6, A. The left frontal nodule is clearly visible. A somewhat smaller nodule surrounded by a zone of decreased density due to edema is also readily visible in the right frontal lobe in this slice. A slightly more irregular lesion of similar size is evident in the right frontoparietal opercular region and is also surrounded by edema. Only a single dense oval area of moderate size is apparent in the right occipital region. D. Autopsy brain slice corresponding approximately to the level scanned in Figure 6, C. The right and left frontal nodules are clearly shown. The slice passes just below the right lateral lesion, which is suggested by a small area of staining. Four discrete contiguous nodules not separately discriminated on the CT scan are seen in the right occipital lobe.
82
PAUL
TABLE
Positive Nega t ive
*» >
=
CT Scans (24)
R adionuclide Images (12)
24t
11 (false diagnosis of a sing le lesion in 3 cases ) 1
o
F.
Ill :
J. N EW
AND O T H E RS
MRTASTASES
(24
Comparison with Angiography * (12)
»
8 (false diagnosis of a sin gle lesion in 1 case )
J a nu ar y 197 5
CASES )
Comparison with Pn eumoencephalography Pneumoen cephalography " Ventriculography ( 1) (1)
+
No diagnosis
"Cerebellar mass"
>4
CT far superior t o angiography/ pneumoencephalogra phy .
= CT dist inctly su perio r t o an giogr aph yj pneumoencep ha logra phy .
t E rror in inter pr et at ion : 2 cases were diagnosed as glioblast om a.
Fi g. 7. Squamous -cell metastases in a 68-year-old wom an with car cin oma of the laryn x who wa s t reat ed ' by lar yngectomy and irr adi at ion follo wed by wedge resecti on of pulmonary meta st ases. A CT scan obta ined be cau se of recent pro gre ssive left hemiparesis reveal ed a ro unded volume of decre ased a bsorp tion (I' 4 to 14) me asuring slight ly greater th an 5 cm in t he an ter ior por tion of th e righ t frontal lobe , wit h sma ll foci of high a bsorptio n scattered wit hin a gener al back gr ound of lower a b sorp tion. T he margins of the lesion wer e relatively re gul ar. A smaller lesion with som ewh at more irregul ar margins a nd a similar a bsorpt ion range was de m onst rated in t he left t em por al lobe and t he region of the left in sul a . A " mTc bra in image t aken the sa me day as the CT scan was negative. The patien t was referred for 'ra diot hera py withou t the need for a ngiogra phy or pneumoencep hal ogra phy .
adenocarcinoma and melanoma may contain irregular, less dense central areas repr esenting ti ssue necrosis (F ig. 5). In contrast, metastatic squa mou s-cell carcinoma genera lly presents a low density relative to that of the brain (IJ- 4 to ] 2-14) and rather smoothly rounded contours with little or no surrounding edema (F ig. 7). In our series, metastatic undifferen tiated carcinoma has resembled squamous-cell carcinoma. A sing le case of rhabdomyosarcoma metastatic to the cerebellum reve aled low absorption values (IJ- 8 to 14). Metastases arid gliomas treated by radiation therapy and chemotherapy may show decreased absorption values on repeat CT examination. Comparative Diagnostic A ccuracy of CT Scans in Cerebral M etastases: There were no false-positive diagnoses among th e 24 cas es of cerebral metastases
Fi g. S. Large men ingiom a of moder at e sca n den sit y in the sp henoid win g and planu m sphen oida le in a 52-y ea r-old woma n wh o had h ad a ra dical maste ct omy (j ye ars ago. F ive years ago she had had intermittent loss of vision in t he left eye followed by permanent visu al loss. M ore recent difficulty with vision in the right eye led t o inv est igati on for sus picion of metastatic carcin om a . Pl ain films of the skull reve al ed chr onic er osion of the upper portion of t he dorsum sellae and ind icated sligh t hyperostosis of the planum sphenoidale . A 99mTc brain im age taken three weeks before the C T scan reveale d a bnorm al uptake ad jacent t o t he left sph en oid wing , thought t o be in the left fr ontal lobe a nd re garded as cons isten t with metast ati c di sease. A plain CT sca n revealed a la rge , rounded vo lume of in cre ased abso r ption occup yi ng mu ch of th e ante rio r portion of t he left middle fossa and ex tending acro ss t he m idline supe rio rl y a nd t o the ri gh t into the inf erior fr ontal r egion and high supras ellar region . The left fr ontal hor n was mark edly com presse d an d t he th ird ve nt r icle was disp lace d severa l rnillim et ers t o th e right. T he m ass measu red 5 cm in antero pos te r ior di am eter and 6 cm t ra nsver sely a nd was rela tively hom ogen eou s in te xt ure (p. 20 t o 30 ). Bilatera l ca ro t id and left ver tebral a ngiograp hy 'clearly reveal ed an ovo id mass in t hese regions, sho wing the charac terist ic vascula r supp ly and pat tern of a men in giom a 7 cm in m aximum di ameter. T his case illu strates the fact t ha t CT scannin g does not obviate the need for good preliminary plain-film exa min at ion , which can pr ov ide ext remely useful in for mat ion re gard ing the presence or a bsen ce of a chro nic in crease in intra cra nial pressure, detail s of bone changes ind icati ve of t he in tr acranial process , and infor mat ion regard ing th e textur e a nd pa tte rn of in t ra cranial ca lcificati on s, all of wh ich are bey ond t he resolution of presen t CT exami na ti on . The con figu rat ion of t he sku ll and the presence or ab sen ce of pla in- film findings assist in planni n g an opt im al individual CT sca n , and t he scan and plain-fil m st ud y should be inter pret ed together.
in this series, Two cases seen earlier in the series were thought to represent glioblastoma, an err or we would not make today. Thus we feel that with som e experience, the accuracy of CT scanning in the identification of mctast ases should approach
Vo!. 114
COMPUTED TOMOGRAPHY WITH TIlE
EMI
SCANNER
83
Neuroradiology
Fig. 9. Plain CT scan reveals a meningioma of moderate size and relatively low density in the left sphenoid wing in a 39-year-old woman with increasing headaches and intermittent diplopia of several months duration as well as visual difficulty and bilateral papilledema for several weeks. A radionuclide image obtained at another center revealed uptake in the left frontotemporal region, and carotid angiography demonstrated a highly vascular mass 3 cm in diameter in the left middle fossa. consistent with a meningioma of the lateral sphenoid wing. The left temporal mass effect was so striking that the possibility of a glioma was entertained. A. The plain CT scan revealed a rather poorly defined region of abnormal absorption (range, p. 17 to 23) in the left middle fossa. In the central portion of this zone was a small region with an absorption range of 19-27. B. A repeat scan following intravenous injection of 50 ml of Hypaque 60M revealed a relatively sharply defined homogeneous zone of markedly increased absorption (p. 23 to 39) measuring 3 cm in diameter extending posteriorly from the sphenoid ridge. Scans at higher levels, both plain and contrast-enhanced, revealed a large volume of diminished absorption (range. p. 7 to 15) in the region of the temporal lobe, deep frontal white matter, and corpus striatum, indicating marked perifocal edema. This explained the temporal lobe mass effect seen at angiography. Both Cl' scans revealed marked mass effects in the lateral and third ventricles.
100%, but only in patients with related neurological signs or symptoms (TABLE Ill). Radionuclide images were obtained in 12 cases; they were positive in 11 and negative in 1. However, in 3 of the positive cases only a single lesion was seen, whereas multiple lesions were demonstrated on the CT scans. Angiography was performed in 12 cases. The CT scan was considered to be far superior in diagnosing the presence, size, and distribution of metastases in 7 and distinctly better in 4. In one case of multiple metastases revealed by the CT scan, only a single mass was identified by angiography; multiplicity was always demonstrated better by the CT scan. Pneumoencephalography was performed in only 2 cases. In one case, no diagnosis was obtained. In the other, ventricular injection of gas was helpful in establishing the correct diagnosis of a cerebellar mass producing hydrocephalus.
Meningiomas Meningiomas are frequently though not invariably of moderate density, with M values ranging from the 20s to the 40s (Fig. 8). These are not
remarkably different from the values seen in intracerebral hematoma, and confusion is possible if the site of the lesion is atypical. However, even in these cases, the clinical context should serve to distinguish the two lesions. A repeat scan following intravenous injection of contrast material should permit differentiation, as there will generally be an obvious increase in the density of meningiomas in the lower and medium density ranges and no increase in that of hematomas. In other cases, the plain CT scan density is only a little higher than that of the brain. In general, when the initial density of a meningioma is relatively low, it is markedly increased by injection of contrast material due to the vascularity of the tumor (Fig. 9). In many cases, the plain CT density of a meningioma is very high, ranging up to as much as 90 or more, due to psammomatous calcification (Fig. 10). In such cases, the calcified regions show little or no further increase in density following injection of contrast material. Calcification can be diagnosed on the CT scan (M> 60) even when none is visible on the plain film. Whether the initial density is high or low, it is generally homogeneous, although large lobulated tumors
84
PAUL
F.
J.
NEW AND OTHERS
January 197;)
Fig. 10. Three posterior fossa meningiomas containing psammomatous calcification in a 57-year-old woman admitted because of a suspected mass lesion in the posterior fossa. A radionuclide brain image revealed areas of abnormal uptake in the right and left sides of the posterior fossa. Plain films did not show calcification. Cerebral angiography revealed considerable dilatation of the lateral ventricle and evidence of an avascular mass (thought to be extracerebral) in the anterolateral portion of the posterior fossa in the cerebellopontine angle cistern. Another avascular mass was seen in the left side of the posterior fossa. A. CT scans obtained before and immediately following intravenous injection of 50 ml of Hypaque 60M revealed a large, homogeneous area of markedly increased absorption in the area of the right angle cistern (p. 25 to 75 on the plain scan, 26 to 85 with Hypaque ). A huge homogeneous lobulated density occupied most of the left half of the posterior fossa (p. 33 to 80 on the plain scan, 36 to 95 with Hypaque). The superior portions of this mass showed f1. values extending up to 170. B. A third lesion 2.5 cm in maximum diameter was demonstrated just below the tentorium posteriorly on the right side. This lesion could not be identified on either the gamma camera image or the angiogram. The homogeneous appearance of all three lesions, the absorption values indicating diffuse calcification within the lesions, and the slight additional increase in density following the injection of contrast material led to a confident CT scan diagnosis of meningioma. Radionuclide studies and angiography gave no indication of the nature of the lesions and even failed to show one of them. The degree and cause of obstructive hydrocephalus were clearly shown on the CT scan.
TABLE
Positive Negative
IV:
MENINGIOMAS
CT Scans (11)
Radionuclide Images (11)
lIt
9
0
2+
(11
CASES)
Comparison Comparison with with AngiPneumoography* encephalogniphy* (9) (1) »3
=3
? Arnold-Chiari malformation
