•
An Extravascular Component of Contrast Enhancement in Cranial Computed Tomography
Computed Tomography
Part I: The Tissue-Btood Ratio of Contrast Enhancement 1 Mokhtar H, Gado, M.D., Michael E. Phelps, Ph.D., and R. Edward Coleman, M.D. One can calculate the tissue-blood ratio of enhancement by analyzing the quantitative aspects of the CT scans of the cranium and blood samples both before and after the injection of contrast medium. This ratio is equivalent to that between the iodine content of a given volume of tissue and an equal volume of blood. Analysis of 47 normal patients, including 27 with pathological brain lesions, indicated that there is significant extravasation of contrast medium in patients with such lesions. INDEX TERMS:
Computed Tomography, cranial. Contrast media
Radiology 117:589-593, December 1975
• experience with cranial computed tomography (CCT) revealed that several cerebral lesions were visualized better after the intravenous administration of iodinated contrast media immediately prior to the scan (1, 2). The injection resulted in increased x-ray attenuation by the lesion, which subsequently appeared as a denser area on the CTT image. This "contrast enhancement" depends on the iodine content of the lesion (Fig. 1). The contrast media used for this purpose are the same pharmaceuticals used for excretory urography and angiography. The intravenous injection of contrast media introduces iodine into the systemic circulation and consequently into the blood pool of the lesion. This factor has been stressed (2, 4, 5), but the possibility of the extravasation of iodine has not been investigated. Several observations have led some investigators to ignore the possibility of an extravascular component of contrast enhancement: in the normal CeT image after contrast enhancement, one often identifies the large cerebral arteries and veins (Fig. 2); furthermore, highly vascular lesions such as aneurysms (Fig. 3) and arterio-
E
ARLY
Fig. 2. Normal CCT scan after intravenous injection of contrast medium. Note the visualization of the middle cerebral arteries (arrowheads) and straight sinus (arrows).
venous malformations show a remarkable degree of contrast enhancement. We intend to prove and discuss the implications of the presence of an extravascular component. The evidence provided in Part I is based upon the difference in
Fig. 1. CCT scan of a patient with a metastatic tumor in the right cerebral hemisphere. A. Before intravenous injection of contrast medium. B. After contrast injection, the image of the lesion is denser due to the increased x-ray attenuation by the iodine in the lesion.
Fig. 3. CCT scan of a patient with a large suprasellar aneurysm. A Before intravenous injection of contrast material. B. After contrast injection. Note the enhancement of the image of the aneurysm.
1 From the Neuroradiology Section (M. H. G.), the Division of Radiation Sciences (M. E. P.), and the Division of Nuclear Medicine (R. E. C.), ss Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Mo. Accepted for publication in September 1975.
589
590
MOKHTAR
Table I:
H. GADO AND OTHERS
samples obtained before and after contrast injection may be scanned and a value of enhancement directly proportional to the concentration of contrast medium can be calculated for the blood. The value of enhancement of an intracranial structure divided by that of the blood is designated the tissue-blood ratio of enhancement. By definition, this ratio is equivalent to that between the iodine content of the intracranial structure and an equivalent volume of circulating blood.
Case Material
Diagnosis
Number of Patients
Normal Degenerative disease Stroke Neoplasms Metastasis (5) Glioblastoma (7) Meningioma (5) Pituitary adenoma (1)
20
5 4
18
47
Total
December 1975
MATERIAL AND METHODS
contrast enhancement of tissue and blood, utilizing the quantitative aspects of the CT image. In Part II we will discuss the relationship between contrast enhancement and the blood-tissue barrier, as well as the implications of this relationship on the prospective roles of CT and radionuclide brain scanning in the investigation of intracranial disease. INTRODUCTION
The printout which accompanies each CCT image produced by the EMI scanner consists of an array of numbers which correspond to the elements of the image. Each number is equivalent to 5X the percentage difference between the reconstructed x-ray attenuation coefficient (Jli) and the attenuation coefficient of water (Jlw) divided by the coefficient of water, i.e.,
EM! number
=
5x J.1.i -
J.1. w x 100
(1)
fJ. w
We refer to the EMI number as the "attenuation value." The reason for the X5 factor in Equation 1 is that most normal intracranial structures have attenuation coefficients higher than that of water by only 4-5 %. Therefore, if the Jl of a medium is 4 % higher than that of water il.e., 1.04 X ~water), the attenuation value is 20 EMI scale units.
One EM! scale unit
=
1/5 (.01 x fJ. w)
== 0.002 x
J.l w
(2)
Since the EMI numbers are of the form shown in Equation 1, the value for water is O. Scans which show increased attenuation subsequent to injection of contrast medium are designated to have a value of enhancement in units of the EMI scale unit as previously defined. Blood Table I I: Attenuation Values of Different Dilutions of Methylglucamine lothalamate (60%) in Distilled Water Methylglucamine lothalamate (60%) (ml/100 ml of mixture)
0.1 0.3 0.5 1.0 1.5 2.0
Iodine Content (mg/100 ml of mixture) 28.2
84.6 141.0 282.0
423.0 564.0
Attenuation Value 4.4
9.6 15.8 37.5 55.6 72.9
All EMI scans were done with the 160 X 160 convolution-based algorithm. Numerical printouts using either the 160 X 160 or 80 X 80 array were employed for quantitative determinations of attenuation. Several dilutions of methylglucamine iothalamate (60 %) in distilled water were prepared to get these solutions: 0.1%, 0.3%, 0.5%, 1%, 1.5% and 2.0%. Six milliliters of each solution were drawn in a plastic syringe with a barrel diameter of 10 mm and inserted into a Plexiglas phantom filled with water which was placed in the EMI scanner. Scans were performed using an 8.0-mm collimator. The x-ray tube was operated at 120 kV and 33 mA, and the duration of each scan was 4.5 minutes. The numerical values from the printouts of the 160 X 160 matrix were used to compute a mean value for the attenuation of each solution. Forty-seven patients (TABLE I) were studied by CCT (Fig. 1). A second scan (Fig. 2) was obtained after the intravenous administration of 100 ml of contrast medium via a 19 gauge needle over the course of four minutes. Six-milliliter samples of venous blood were obtained in a heparinized plastic syringe with a barrel diameter of 10 mm at the end of Scan 1 and at the beginning and end of Scan 2. These were scanned in a phantom filled with water, and 80 X 80 printouts were obtained for each scan of the patient's head and for the blood samples. The enhancement of normal intracranial structures and pathological lesions was calculated. A normal structure or lesion was identified on the first scan; the attenuation values corresponding to these areas on the printout were averaged, and the mean value recorded. The same area was then identified on the second scan and the mean value of attenuation calculated. The dif~ ference between these two mean values was taken as the quantitative value of enhancement. In the case of blood samples, three mean values were obtained using the same method and the values for the second and third samples were averaged. The difference between this average and the mean attenuation value for the first sample was taken as the quantitative value of enhancement of the blood. Since the enhancement of tissue and blood is related to their iodine content, the ratio of enhancement of tissue to that of blood was calculated and' multiplied by 100. If iodine were confined strictly to the blood space, this ratio would correspond to the per cent blood volume in the tissue.
THE TISSUE-BLOOD RATIO OF CONTRAST ENHANCEMENT
Vol. 117
Circulating blood before contrast injection Enhancement of circulating blood Estimated iodine content
Range
Mean (±S.O.)
EMI scale units
17.8-26.7
21.4 (±2.4)
u
~
600 2.0 II:
"E
...'"c
CO'
E
1.5
... 400
EMI scale units mgj100 ml
5.6-36.9 43-284
z
22.5 (±8.5)
...z '"
~
Table IV: Mean Attenuation Values and Values of Contrast Enhancement of Normal Structures
Normal Structures
n*
White matter Basal ganglia Choroid plexus Straight sinus
62 14 9 30
Attenuation Value Before Contrast Injectiont 16.2 17.7 27.5 19.1
(1.6) (1.5) (14.8) (3.0)
Value of Contrast Enhancementt 0.6 0.6 6.3 9.3
(1.6) (1.8) (4.9) (5.3)
* Number of measurements. I n several cases, measurements of white matter were taken from more than one area of the same scan. t Results, expressed as a mean (S.D.).
200
~
~
C II: Z
., 0
0
0.5
~
In 6 patients in whom brain tumors were suspected (and later confirmed histologically), CCT scans of the lesion and the systemic venous blood were repeated over periods of 30-90 minutes. The tissue-blood ratio of enhancement was calculated and recorded as a function of the time lapse after injection.
The attenuation values of different dilutions of contrast material are shown in TABLE II and Figure 4. There is a linear relationship between the attenuation values and the iodine content in the concentration range of 28-560 mg/100 ml of iodine; the slope of the line indicates that each 100 mg/100 ml of iodine corresponds to 13 EMI scale units in this concentration range. This validates this method for comparing the iodine content in tissue and blood scanned by the EMI scanner. The tissue-blood ratio of pathological lesions and normal intracranial structures were calculated in 47 patients (TABLE I). Twenty patients showed no evidence of abnormality on the CCT scan; 4 cases were diagnosed as stroke, 5 as metastatic disease, 5 as meningioma, 1 as pituitary adenoma, and 7 as glioblastoma. In the 13 patients with primary intracranial neoplasms, the diagnosis was confirmed histologically. In the 5 patients with metastatic disease, the diagnoses were presumptive on the basis of a history of known primary disease in 4 cases; histological confirmation was obtained in only one patient in this group. In the 4 patients with stroke, the diagnosis was made on the basis of clinical criteria. In 3 of them, the CCT diagnosis was intracerebral hematoma, and in 1 patient it was infarction. The attenuation values of circulating blood before contrast injection varied from 17.8 to 26.7 EMI scale units, with a mean value of 21.4 (± 2.4) (TABLE III). The increase in attenuation of blood due to the presence of
1.0
u
o
• 0 cD
o
173 (±65)
RESULTS
Computed Tomograph)
2.5
Table III: Attenuation Values of Blood and Values of Contrast Enhancement in Blood in 47 Patients Unit
591
EMI
NUMBER
Fig. 4. The relationship between the EMI number (attenuation value) and iodine concentration in various dilutions of Conray in distilled water.
iodine in the circulation during Scan 2 varied from 5.6 to 36.9, with a mean value of 22.5 (± 8.5). From Figure 4, this mean value corresponds to an iodine content in the circulating blood of 173 (± 65) mg/100 rnl, The attenuation values of normal intracranial structures and the enhancement of these structures after administration of the iodinated contrast medium are shown in TABLE IV. The values of enhancement of the white matter and the basal ganglia were insignificant (0.6 EMI scale units), but highly vascular structures showed significant values. The choroid plexus was shown to gain 6.3 (± 4.9) units and the straight sinus 9.3 (± 5.3) units after intravenous administration of contrast medium. The enhancement and tissue-blood ratios obtained from the studies of 18 patients with neoplastic lesions are shown in TABLE V. The lesion enhancement varied from 2.1 to 18.6 units in glioblastoma, 1.9 to 24.2 units in meningioma, and 5.5 to 8.0 units in metastases. The relatively low value of 1.9 in a patient with a meningioma was related to a calcified meningioma with an initial attenuation value of 190. A value of enhancement of Table V:
Pt. No. 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18
Contrast Enhancement and Tissue-Blood Ratio in Neoplasms
Contrast Enhancement Systemic Lesion Blood 11.7 18.9 24.6 17.2 28.0 14.6 16.8 18.5 10.2 17.4 18.2 17.3 40.6 30.2 15.4 16.4 19.1 17.5
2.1 3.8 6.5 6.0 16.5 10.1 18.6 1.9 3.4 8.2 24.2 10.3 8.0 7.2 6.6 6.8 8.0 10.5
TissueBlood Ratio (%)
Diagnosis
17.9 20.1 26.4 34.8 59.0 69.1 110.0 10.3 33.3 47.1 133.0 59.5 19.6 23.8 42.9 41.5 41.9 60.0
Glioblastoma Glioblastoma Glioblastoma Glioblastoma Glioblastoma Glioblastoma Glioblastoma Meningioma Meningioma Meningioma Meningioma Meningioma Metastasis Metastasis Metastasis Metastasis Metastasis Pituitary adenoma
MOKHTAR H. GADO AND OTHERS
592
Table V I:
Tissue-Blood Ratio of Enhancement in 4 Patients with Stroke
Diagnosis
Tissue-Blood Ratio (%)
Intracerebra I hematoma Intracerebra I hematoma Intracerebral hematoma Cerebral infarct
o o o
10.5 units was seen in the case of pituitary adenoma. In this series, the two highest values of contrast enhancement were from a glioblastoma and a meningioma with values of 18.6 and 24.2, respectively. The majority of the other lesions showed comparable ranges of enhancement, whatever the histological type. The most significant part of TABLE V is the tissueblood ratio of enhancement. This ratio is the amount of iodine in a volume of tissue divided by the amount in an equivalent volume of blood. If the tissue iodine within the field of the scan was solely confined to the blood space, this ratio would be equal to the blood volume per unit volume of tissue. The tissue-blood ratios varied, however, from 10 to 133 ok, and were comparable irrespective of the histological nature of the lesion. In 12 of the 18 cases, the ratio was higher than 40 %. In one glioblastoma and one meningioma the ratios were 110% and 133 ok, respectively. Of those patients with stroke (TABLE VI), none of the 3 with an intracerebral hematoma showed contrast enhancement. The single patient with a thromboembolic infarction showed a tissue-blood ratio of 9 % . The variation of the tissue-blood ratio of enhancement as a function of time was examined in 6 cases (Fig. 5). In 4, the tissue-blood ratio increased with time; these included 2 patients with glioblastoma, 1 with meningioma, and 1 with metastasis. The remaining 2 pa-
a
RATIO BETWEEN TUMOR BLOOD ENHANCEMENT AS A FUNCTION OF TIME IN FOUR CASES (I) (2) (3) (4)
l 0
2
0:: 0
a
RATIO BETWEEN TUMOR BLOOD ENHANCEMENT AS A FUNCTION OF TIME IN TWO CASES
GLIOBLASTOMA MENINGIOMA METASTASIS
80
~~
IaJ
r
/
/(3) ,,
41
,
60
I
40
00 2 0 ~..J
2~
L&JW
,
..
A
-- ---
--
- - - - __ (I)
75
«
An Extravascular Component of Contrast Enhancement in Cranial Computed Tomography
Computed Tomography
Part I: The Tissue-Btood Ratio of Contrast Enhancement 1 Mokhtar H, Gado, M.D., Michael E. Phelps, Ph.D., and R. Edward Coleman, M.D. One can calculate the tissue-blood ratio of enhancement by analyzing the quantitative aspects of the CT scans of the cranium and blood samples both before and after the injection of contrast medium. This ratio is equivalent to that between the iodine content of a given volume of tissue and an equal volume of blood. Analysis of 47 normal patients, including 27 with pathological brain lesions, indicated that there is significant extravasation of contrast medium in patients with such lesions. INDEX TERMS:
Computed Tomography, cranial. Contrast media
Radiology 117:589-593, December 1975
• experience with cranial computed tomography (CCT) revealed that several cerebral lesions were visualized better after the intravenous administration of iodinated contrast media immediately prior to the scan (1, 2). The injection resulted in increased x-ray attenuation by the lesion, which subsequently appeared as a denser area on the CTT image. This "contrast enhancement" depends on the iodine content of the lesion (Fig. 1). The contrast media used for this purpose are the same pharmaceuticals used for excretory urography and angiography. The intravenous injection of contrast media introduces iodine into the systemic circulation and consequently into the blood pool of the lesion. This factor has been stressed (2, 4, 5), but the possibility of the extravasation of iodine has not been investigated. Several observations have led some investigators to ignore the possibility of an extravascular component of contrast enhancement: in the normal CeT image after contrast enhancement, one often identifies the large cerebral arteries and veins (Fig. 2); furthermore, highly vascular lesions such as aneurysms (Fig. 3) and arterio-
E
ARLY
Fig. 2. Normal CCT scan after intravenous injection of contrast medium. Note the visualization of the middle cerebral arteries (arrowheads) and straight sinus (arrows).
venous malformations show a remarkable degree of contrast enhancement. We intend to prove and discuss the implications of the presence of an extravascular component. The evidence provided in Part I is based upon the difference in
Fig. 1. CCT scan of a patient with a metastatic tumor in the right cerebral hemisphere. A. Before intravenous injection of contrast medium. B. After contrast injection, the image of the lesion is denser due to the increased x-ray attenuation by the iodine in the lesion.
Fig. 3. CCT scan of a patient with a large suprasellar aneurysm. A Before intravenous injection of contrast material. B. After contrast injection. Note the enhancement of the image of the aneurysm.
1 From the Neuroradiology Section (M. H. G.), the Division of Radiation Sciences (M. E. P.), and the Division of Nuclear Medicine (R. E. C.), ss Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Mo. Accepted for publication in September 1975.
589
590
MOKHTAR
Table I:
H. GADO AND OTHERS
samples obtained before and after contrast injection may be scanned and a value of enhancement directly proportional to the concentration of contrast medium can be calculated for the blood. The value of enhancement of an intracranial structure divided by that of the blood is designated the tissue-blood ratio of enhancement. By definition, this ratio is equivalent to that between the iodine content of the intracranial structure and an equivalent volume of circulating blood.
Case Material
Diagnosis
Number of Patients
Normal Degenerative disease Stroke Neoplasms Metastasis (5) Glioblastoma (7) Meningioma (5) Pituitary adenoma (1)
20
5 4
18
47
Total
December 1975
MATERIAL AND METHODS
contrast enhancement of tissue and blood, utilizing the quantitative aspects of the CT image. In Part II we will discuss the relationship between contrast enhancement and the blood-tissue barrier, as well as the implications of this relationship on the prospective roles of CT and radionuclide brain scanning in the investigation of intracranial disease. INTRODUCTION
The printout which accompanies each CCT image produced by the EMI scanner consists of an array of numbers which correspond to the elements of the image. Each number is equivalent to 5X the percentage difference between the reconstructed x-ray attenuation coefficient (Jli) and the attenuation coefficient of water (Jlw) divided by the coefficient of water, i.e.,
EM! number
=
5x J.1.i -
J.1. w x 100
(1)
fJ. w
We refer to the EMI number as the "attenuation value." The reason for the X5 factor in Equation 1 is that most normal intracranial structures have attenuation coefficients higher than that of water by only 4-5 %. Therefore, if the Jl of a medium is 4 % higher than that of water il.e., 1.04 X ~water), the attenuation value is 20 EMI scale units.
One EM! scale unit
=
1/5 (.01 x fJ. w)
== 0.002 x
J.l w
(2)
Since the EMI numbers are of the form shown in Equation 1, the value for water is O. Scans which show increased attenuation subsequent to injection of contrast medium are designated to have a value of enhancement in units of the EMI scale unit as previously defined. Blood Table I I: Attenuation Values of Different Dilutions of Methylglucamine lothalamate (60%) in Distilled Water Methylglucamine lothalamate (60%) (ml/100 ml of mixture)
0.1 0.3 0.5 1.0 1.5 2.0
Iodine Content (mg/100 ml of mixture) 28.2
84.6 141.0 282.0
423.0 564.0
Attenuation Value 4.4
9.6 15.8 37.5 55.6 72.9
All EMI scans were done with the 160 X 160 convolution-based algorithm. Numerical printouts using either the 160 X 160 or 80 X 80 array were employed for quantitative determinations of attenuation. Several dilutions of methylglucamine iothalamate (60 %) in distilled water were prepared to get these solutions: 0.1%, 0.3%, 0.5%, 1%, 1.5% and 2.0%. Six milliliters of each solution were drawn in a plastic syringe with a barrel diameter of 10 mm and inserted into a Plexiglas phantom filled with water which was placed in the EMI scanner. Scans were performed using an 8.0-mm collimator. The x-ray tube was operated at 120 kV and 33 mA, and the duration of each scan was 4.5 minutes. The numerical values from the printouts of the 160 X 160 matrix were used to compute a mean value for the attenuation of each solution. Forty-seven patients (TABLE I) were studied by CCT (Fig. 1). A second scan (Fig. 2) was obtained after the intravenous administration of 100 ml of contrast medium via a 19 gauge needle over the course of four minutes. Six-milliliter samples of venous blood were obtained in a heparinized plastic syringe with a barrel diameter of 10 mm at the end of Scan 1 and at the beginning and end of Scan 2. These were scanned in a phantom filled with water, and 80 X 80 printouts were obtained for each scan of the patient's head and for the blood samples. The enhancement of normal intracranial structures and pathological lesions was calculated. A normal structure or lesion was identified on the first scan; the attenuation values corresponding to these areas on the printout were averaged, and the mean value recorded. The same area was then identified on the second scan and the mean value of attenuation calculated. The dif~ ference between these two mean values was taken as the quantitative value of enhancement. In the case of blood samples, three mean values were obtained using the same method and the values for the second and third samples were averaged. The difference between this average and the mean attenuation value for the first sample was taken as the quantitative value of enhancement of the blood. Since the enhancement of tissue and blood is related to their iodine content, the ratio of enhancement of tissue to that of blood was calculated and' multiplied by 100. If iodine were confined strictly to the blood space, this ratio would correspond to the per cent blood volume in the tissue.
THE TISSUE-BLOOD RATIO OF CONTRAST ENHANCEMENT
Vol. 117
Circulating blood before contrast injection Enhancement of circulating blood Estimated iodine content
Range
Mean (±S.O.)
EMI scale units
17.8-26.7
21.4 (±2.4)
u
~
600 2.0 II:
"E
...'"c
CO'
E
1.5
... 400
EMI scale units mgj100 ml
5.6-36.9 43-284
z
22.5 (±8.5)
...z '"
~
Table IV: Mean Attenuation Values and Values of Contrast Enhancement of Normal Structures
Normal Structures
n*
White matter Basal ganglia Choroid plexus Straight sinus
62 14 9 30
Attenuation Value Before Contrast Injectiont 16.2 17.7 27.5 19.1
(1.6) (1.5) (14.8) (3.0)
Value of Contrast Enhancementt 0.6 0.6 6.3 9.3
(1.6) (1.8) (4.9) (5.3)
* Number of measurements. I n several cases, measurements of white matter were taken from more than one area of the same scan. t Results, expressed as a mean (S.D.).
200
~
~
C II: Z
., 0
0
0.5
~
In 6 patients in whom brain tumors were suspected (and later confirmed histologically), CCT scans of the lesion and the systemic venous blood were repeated over periods of 30-90 minutes. The tissue-blood ratio of enhancement was calculated and recorded as a function of the time lapse after injection.
The attenuation values of different dilutions of contrast material are shown in TABLE II and Figure 4. There is a linear relationship between the attenuation values and the iodine content in the concentration range of 28-560 mg/100 ml of iodine; the slope of the line indicates that each 100 mg/100 ml of iodine corresponds to 13 EMI scale units in this concentration range. This validates this method for comparing the iodine content in tissue and blood scanned by the EMI scanner. The tissue-blood ratio of pathological lesions and normal intracranial structures were calculated in 47 patients (TABLE I). Twenty patients showed no evidence of abnormality on the CCT scan; 4 cases were diagnosed as stroke, 5 as metastatic disease, 5 as meningioma, 1 as pituitary adenoma, and 7 as glioblastoma. In the 13 patients with primary intracranial neoplasms, the diagnosis was confirmed histologically. In the 5 patients with metastatic disease, the diagnoses were presumptive on the basis of a history of known primary disease in 4 cases; histological confirmation was obtained in only one patient in this group. In the 4 patients with stroke, the diagnosis was made on the basis of clinical criteria. In 3 of them, the CCT diagnosis was intracerebral hematoma, and in 1 patient it was infarction. The attenuation values of circulating blood before contrast injection varied from 17.8 to 26.7 EMI scale units, with a mean value of 21.4 (± 2.4) (TABLE III). The increase in attenuation of blood due to the presence of
1.0
u
o
• 0 cD
o
173 (±65)
RESULTS
Computed Tomograph)
2.5
Table III: Attenuation Values of Blood and Values of Contrast Enhancement in Blood in 47 Patients Unit
591
EMI
NUMBER
Fig. 4. The relationship between the EMI number (attenuation value) and iodine concentration in various dilutions of Conray in distilled water.
iodine in the circulation during Scan 2 varied from 5.6 to 36.9, with a mean value of 22.5 (± 8.5). From Figure 4, this mean value corresponds to an iodine content in the circulating blood of 173 (± 65) mg/100 rnl, The attenuation values of normal intracranial structures and the enhancement of these structures after administration of the iodinated contrast medium are shown in TABLE IV. The values of enhancement of the white matter and the basal ganglia were insignificant (0.6 EMI scale units), but highly vascular structures showed significant values. The choroid plexus was shown to gain 6.3 (± 4.9) units and the straight sinus 9.3 (± 5.3) units after intravenous administration of contrast medium. The enhancement and tissue-blood ratios obtained from the studies of 18 patients with neoplastic lesions are shown in TABLE V. The lesion enhancement varied from 2.1 to 18.6 units in glioblastoma, 1.9 to 24.2 units in meningioma, and 5.5 to 8.0 units in metastases. The relatively low value of 1.9 in a patient with a meningioma was related to a calcified meningioma with an initial attenuation value of 190. A value of enhancement of Table V:
Pt. No. 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18
Contrast Enhancement and Tissue-Blood Ratio in Neoplasms
Contrast Enhancement Systemic Lesion Blood 11.7 18.9 24.6 17.2 28.0 14.6 16.8 18.5 10.2 17.4 18.2 17.3 40.6 30.2 15.4 16.4 19.1 17.5
2.1 3.8 6.5 6.0 16.5 10.1 18.6 1.9 3.4 8.2 24.2 10.3 8.0 7.2 6.6 6.8 8.0 10.5
TissueBlood Ratio (%)
Diagnosis
17.9 20.1 26.4 34.8 59.0 69.1 110.0 10.3 33.3 47.1 133.0 59.5 19.6 23.8 42.9 41.5 41.9 60.0
Glioblastoma Glioblastoma Glioblastoma Glioblastoma Glioblastoma Glioblastoma Glioblastoma Meningioma Meningioma Meningioma Meningioma Meningioma Metastasis Metastasis Metastasis Metastasis Metastasis Pituitary adenoma
MOKHTAR H. GADO AND OTHERS
592
Table V I:
Tissue-Blood Ratio of Enhancement in 4 Patients with Stroke
Diagnosis
Tissue-Blood Ratio (%)
Intracerebra I hematoma Intracerebra I hematoma Intracerebral hematoma Cerebral infarct
o o o
10.5 units was seen in the case of pituitary adenoma. In this series, the two highest values of contrast enhancement were from a glioblastoma and a meningioma with values of 18.6 and 24.2, respectively. The majority of the other lesions showed comparable ranges of enhancement, whatever the histological type. The most significant part of TABLE V is the tissueblood ratio of enhancement. This ratio is the amount of iodine in a volume of tissue divided by the amount in an equivalent volume of blood. If the tissue iodine within the field of the scan was solely confined to the blood space, this ratio would be equal to the blood volume per unit volume of tissue. The tissue-blood ratios varied, however, from 10 to 133 ok, and were comparable irrespective of the histological nature of the lesion. In 12 of the 18 cases, the ratio was higher than 40 %. In one glioblastoma and one meningioma the ratios were 110% and 133 ok, respectively. Of those patients with stroke (TABLE VI), none of the 3 with an intracerebral hematoma showed contrast enhancement. The single patient with a thromboembolic infarction showed a tissue-blood ratio of 9 % . The variation of the tissue-blood ratio of enhancement as a function of time was examined in 6 cases (Fig. 5). In 4, the tissue-blood ratio increased with time; these included 2 patients with glioblastoma, 1 with meningioma, and 1 with metastasis. The remaining 2 pa-
a
RATIO BETWEEN TUMOR BLOOD ENHANCEMENT AS A FUNCTION OF TIME IN FOUR CASES (I) (2) (3) (4)
l 0
2
0:: 0
a
RATIO BETWEEN TUMOR BLOOD ENHANCEMENT AS A FUNCTION OF TIME IN TWO CASES
GLIOBLASTOMA MENINGIOMA METASTASIS
80
~~
IaJ
r
/
/(3) ,,
41
,
60
I
40
00 2 0 ~..J
2~
L&JW
,
..
A
-- ---
--
- - - - __ (I)
75
«
