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detection of paramagnetic contrast enhancement the diagnosis of disk versus scar in lumbar i989;i72(P):286 Ross JS, Masaryk TJ, Medic MT. 3-Dimensional

Nonneurologic Bernd

IN CONTRAST-ENHANCED

by PEACH MA imaging. FLASH

imaging for Radiology

imaging

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tion with gadolinium DTPA. J Comput Assist Tomogr i988;13:547-552 Majumdar 5, Zoghbi SS, Gore JG. Regional differences in rat brain displayed by fast MAI with superparamagnetic Imag i988;6:61 1-615

contrast

agents.

Magn

Reson

Applications

Harnm

Clinical studies investigating the use of contrast agents in MR imaging of the body are few in comparison to studies of contrast-enhanced MR imaging of the brain and spinal canal. This fact is attributable in part to the relatively greater complexity associated with contrast-enhanced MR imaging of nonneurobogic disorders. For example, gadopentetate dimeglumine-induced signal enhancement can result in more pronounced motion artifacts, and the rapid diffusion of gadopentetate dimeglumine into the extracellubar space may neutralize soft-tissue contrast between healthy and diseased tissue. As there is considerable organ-to-organ variation in the use of contrast agents, in this section we will present an organspecific discussion on nonneurologic applications of MR contrast agents.

Extracraniab

Head

and Neck

Experience in MR imaging of the head and neck with gadopentetate dimeglumine suggests that contrast-enhanced MR imaging will be of variable usefulness. Although the exact role of gadopentetate-enhanced imaging of head and neck tumors is still evolving, CT is still required to evaluate bony changes. In normal persons, contrast enhancement is particularly striking in the well-perfused nasal mucosa. Thus, diagnostic improvement associated with contrast-enhanced MR imaging does not extend to all tumors of the nasopharynx and oropharynx, but mainly to those in the nasal and paranasal cavities [1 -3]. The advantage of contrast-enhanced imaging results from improved demarcation of tumors from thickened mucosa, scar tissue, or sinus secretions, because tumors show only modest enhancement as opposed to the intense enhancement of mucosa and the nonenhancement of scar tissue or secretions [1 2, 4]. Compared with Ti weighted precontrast images, there also may be better debineation of tumors from muscles and connective tissue, although the tumor enhancement reduces contrast with fatty tissue. In the neck, good visualization of the highly vascubarized paragangliomas of the carotid body is possible with dynamic contrast-enhanced MR imaging [5]. Maximal signal intensity is seen approximately 300 sec after bolus application of gadopentetate dimeglumine [6]. The sensitivity of contrast,

enhanced MR imaging is far superior to that of CT for detecting even small paragangliomas in the temporal bone and the carotid body. The usefulness of dynamic gadopentetate dimeglumine-enhanced MR imaging with gradient-echo pulse sequences is still being examined for differentiation between various histologic types.

Mediastinum Few reports are available on the use of gadopentetate dimeglumine in the chest. A major drawback is that gadopentetate dimeglumine reduces contrast between mediastinal fat and enhancing tumors (Fig. i) [7, 8], although this limitation can be overcome with the use of fat-suppressed imaging techniques [9]. Our experience (unpublished data) shows that contrast-enhanced MR imaging does not improve the staging of esophageal carcinoma compared with unenhanced MR imaging or CT. Contrast-enhanced MR imaging, however, does permit differentiation between viable and necrotic tumor areas, which may be useful for the evaluation of mediastinal tumors (especially bymphomas) in patients undergoing chemotherapy or radiation treatment.

Heart Research on contrast-enhanced MR imaging of the heart has focused on the diagnosis of myocardial infarction, because congenital heart disease, acquired valvubar defects, and cardiac function are adequately evaluated with unenhanced MR imaging. Assessment of myocardial infarction requires ECG-gated, Ti-weighted, SE pulse sequences with gadopentetate dimeglumine being applied as a bolus [1 0-i 2]. Gadopentetate dimeglumine produces pronounced shortening of Ti in the infarcted area, thus enhancing the signal intensity of this area relative to unaffected myocardium [i 0, 1 3]. This observation is explained by the fact that the accumulation of gadopentetate dimeglumine in myocardiab tissue is determined not only by the tissue blood volume and blood flow, but also by the size of the extracelbular space and capillary permeability [i4]. De Roos et al. [10] found the highest contrast between normal and infarcted myocardium to occur 20 to 30 mm after the application of gadopentetate

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Fig. i.-Ti-weighted (SE 500/i5) MR images of esophageal carcinoma obtained at 1.5 T before (A) and after (B) administration of gadopentetate dimeglumine. Note intense enhancement of tumor obscuring its border with adjoining fat.

A

B

dimeglumine, and the authors considered the delineation of infarcted area to be substantially improved in the postcontrast images. However, the interesting question of differentiation between reperfused and nonperfused myocardial infarction is presently insufficiently answered by contrast-enhanced MR imaging. Gadopentetate dimeglumine may be used to distinguish between acute and chronic myocardiab infarction. Although no significant uptake of gadopentetate dimeglumine occurs in chronic myocardial infarction, and the affected area is therefore delineated only indirectly on the basis of morphologic changes, such as thinning of the wall and aneurysm formation, gadopentetate dimeglumine also can be a positive marker of acute myocardial infarction [i i i 5]. For instance, Nishimura et al. [i i ] found enhancement in the infarcted area in (82%) of i 7 patients with acute myocardial infarction but only in three (21 %) of i 4 patients 90 days later. The use of gadopentetate dimeglumine in the evaluation of the myocardium is limited by diffusion of the contrast agent into the extracellular space and rapid renal excretion [i 6]. Better results might be obtained by combining the use of gadopentetate dimeglumine as a myocardium-perfusion substance with fast imaging techniques. Additionally, intravascular contrast agents such as albumin-gadopentetate dimeglumine could further improve the diagnostic value of myocardial perfusion studies [1 7, i 8].

carcinomas show the lowest increase [22]. Normal glandular tissue and nonproliferating mastopathy as well as scars after 6 months show no or only insignificant uptake of the contrast agent [i 9]. Proliferating mastopathy displays considerable variation with respect to contrast uptake, but increasing enhancement is observed with higher degrees of proliferation [22]. The greatest variation in contrast behavior and signal enhancement is seen in fibroadenomas [1 9, 20]. Thus, because of the strong and early contrast enhancement of carcinomas of the breast as opposed to the delayed and less pronounced enhancement of most benign lesions, dynamic contrast-enhanced examination appears to be promising for MR imaging of the breast.

,

Breast Gadopentetate dimeglumine-enhanced MR imaging may provide valuable information for tumor diagnosis in dense breasts, differentiation of scars from carcinoma, and screening for tumor recurrence between silicone implants and the thoracic wall. Dynamic contrast-enhanced MR imaging provides the key for improving the differential diagnosis [19-22]. Carcinomas are characterized by a strong increase in signal intensity of up to i 00% within the first 2 mm after contrast administration and a subsequent plateau [20]. The increase in signal intensity is strongest in mucinous carcinomas, followed by ductal and lobular carcinomas, whereas scirrhous

Liver Both paramagnetic gadopentetate dimeglumine and superparamagnetic iron oxide particles have been investigated in clinical studies of liver tumors. Results obtained so far indicate that these two substances do no compete with each other: dynamic gadopentetate dimeglumine-enhanced MR imaging yields important physiologic information for the differential diagnosis of liver tumors, whereas iron oxides are of particular interest for tumor screening. Gadopentetate dimeglumine-enhanced MR imaging of liver tumors requires that fast imaging techniques be used in combination with bolus application of the contrast agent. An increase in contrast between liver and tumor occurs only in the first 2-3 mm after administration of gadopentetate dimeglumine [23, 24]. Subsequent diffusion of the contrast agent into the tumor reduces tumor-liver contrast. As there is no significant hepatocyte excretion of gadopentetate dimeglumine, delayed MR imaging, unlike CT with iodinated contrast media, does not improve the detection of hepatic lesions [25]. Dynamic gadopentetate dimeglumine-enhanced MR rnaging is most useful for studying perfusion of hepatic tumors. The enhancement patterns of benign and malignant liver tumors in MR imaging are similar to those seen in CT [2630]. However, enhancement induced by gadopentetate di-

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meglumine in MR imaging (on strongly Ti -weighted fast pulse sequences) is more pronounced than enhancement with iodinated contrast media in dynamic CT [3i ]. The appearance of hernangiomas in dynamic gadopentetate dimeglumineenhanced MR imaging is characterized by hyperintense peripherab enhancement followed by a fill-in phenomenon (Fig. 2). This is quite distinct from the enhancement behavior of liver metastases (Fig. 3) and hepatocellular carcinomas [32]. The difference in signal intensity between hemangiomas and metastases is most striking on delayed images [30]. Hypervascular metastases do not show the homogeneous high signal intensity typical of hemangiomas [3i ]. Focal-nodular hyperplasia is characterized in dynamic contrast-enhanced MR imaging by strong contrast enhancement, with a peak during the first 30 sec after contrast administration, and by a rapid decrease in signal intensity (Fig. 4) [31]. The effect of superparamagnetic iron oxide particles on MR imaging is fundamentally different from that of gadopentetate dimeglumine. Animal studies showed that IV iron oxide selectiveby reduces signal intensity of healthy liver tissue, whereas signal intensity of intrahepatic tumors remains constant. Thus contrast between the two tissues increases [33, 34]. Although

Fig. 2.-Dynamic gadopentetate dimeglumine-enhanced MR images (GRE iOO/5, 80#{176}) of hemangiomas at i.5 T. Large hemangioma shows peripheral enhancement on early image (A, 5 mm) and fill-in phenomenon on delayed image (B, 20 mm). Smaller hemangiomas (arrows) show early and persistent homogeneous enhancement after gadopentetate dimeglumine administration. Thus hemangiomas show slow fill-in and slow washout of contrast agent.

Fig. 3.-Dynamic gadopentetate dimeglumine-enhanced MR images (GRE iOO/5, 800) of adenocarcinoma metastasis at i.5 T. Lesion shows inhomogeneous enhancement on immediate (30 sac) image (A) and remains hypointense relative to surrounding liver parenchyma at 5 mm (B). Thus hypovascular metastases show limited enhancement with contrast agent.

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iron oxide-induced signal reduction of liver tissue is strongest on gradient-echo sequences [35], intermediately weighted spin-echo sequences are more suitable for liver imaging because they offer better anatomic resolution owing to their superior signal-to-noise ratios. Preliminary clinical evaluation of patients with liver cancer suggests that iron oxide-enhanced MR imaging may increase the conspicuity of liver lesions and bower the size threshold for lesion detection (Fig. 5) [36, 37]. More importantly, this contrast agent also appears to reduce the rigid scanning requirements associated with paramagnetic gadopentetate dimeglumine (Fig. 6). Discriminating benign from malignant lesions has been investigated also. Hahn et al. [38] showed that iron oxides produce prolonged diminution in signal intensity of cavernous hemangiomas and that this phenomenon was absent in hypovascular and hypervascular metastases. Difficulties in image interpretation after iron oxide administration arise from signal in blood vessels and perivascular fat. Although this problem has not been fully evaluated, possible solutions include the use of fatsuppressed techniques (to eliminate signal from lipid protons) and early dynamic imaging after iron oxide administration (to eliminate intravascular signal) (Fig. 7).

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248

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Fig. 4.-Dynamic gadopentetate dimeglumine-enhanced MR images (GRE iOO/5, 800) of focal nodular hyperplasia at i.5 T. Note immediate (A, 30 sac) and strong enhancement of hyperperfused lesion, which subsequently becomes isointense on delayed scans (B, 4 mm). Thus focal nodular hyperplasia shows rapid fillin and rapid washout of contrast agent.

Fig. 5.-Iron oxide-enhanced A-C, SE 275/14, precontrast of lesions seen on postcontrast

MR imaging of liver metastases at 0.6 T. Ti-weighted (A), SE 500/30, postcontrast (B) and precontrast scan (B) compared with best precontrast image (A).

Fig. 6.-Iron oxide-enhanced MR imaging of liver metastases at 0.6 T. Precontrast Ti-weighted SE 275/i4 (A), postcontrast proton-density SE i500/40 high lesion-liver contrast on postcontrast images. compare with Fig. 5B. These post-iron parameters can be used to provide high tumor-liver contrast. A-C,

Spleen The sensitivity of MR imaging in the detection of tumorous lesions of the spleen is bow because relaxation times and signal intensities of normal spleen and intrasplenic tumors are

(C) mixed

Ti-T2

weighted

images.

Note increased

number

(B), and postcontrast T2-weighted SE i500/80 (C) images. Note oxide images illustrate that wide range of pulse-sequence timing

very similar. The size and extent of focal processes are therefore easily underestimated or lesions completely escape detection [39]. Contrast agents can dramatically improve tumor detection. For example, the early phase of dynamic gadopentetate dirneglumine-enhanced MR imaging is char-

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IMAGING

Fig. 7.-Dynamic iron oxide-enhanced MR imaging (SE i500/80) of normal liver at 0.6 T. A-C, Precontrast (A), dynamic image at i-iO mm after contrast administration (B), delayed image at 60 mm after signal intensity in blood vessels (aorta and intrahepatic vessels) seen on precontrast and delayed postcontrast images effect can be exploited to assess tissue perfusion.

249

contrast administration (C). is absent in dynamic phase.

High This

7.

Fig. 8.-Dynamic gadopentetate dimeglumine-enhanced MR imaging at i.5 T, GRE 100/5, 80#{176}. A and B, Precontrast image (A ) shows paraaortic lymph node (arrow). Focus of nodular lymphoma in spleen is seen on i-mm postcontrast scan (B).

acterized by improved contrast between the hypointense tumor and the surrounding hyperintense tissue. However, diffusion of the contrast agent into the lesion destroys this enhanced lesion-spleen contrast within a few minutes (Fig. 8). More promising results have been obtained with IV administered iron oxide particles. As in the liver, they reduce the signal intensity of normal splenic tissue. Clinical examinations of splenic tumors with iron oxide show that at a dose of 30 mob Fe/kg, a significant signal reduction in normal spleen occurs, while metastases remain unaffected, which results in improved visualization of metastases [40]. Iron oxide-enhanced MR imaging is also a promising procedure for distinguishing normal spleens from those diffusely infiltrated by lymphoma (Fig. 9) [41]. The diagnostic indicator in this case is the change in signal intensity after contrast administration (40 mol Fe/kg), because bymphomatous spleens show a significantly higher signal intensity than do normal spleens or spleens that are enlarged because of benign diseases.

Fig. 9.-Iron oxide-enhanced MR image of splenic lymphoma at 0.6 T. Owing to lymphomatous infiltration, spleen does not trap iron oxide particles and therefore fails to turn black. Compare with signal decrease after iron oxide administration in normal spleen in Fig. 6. (Reproduced with permission from Weissleder et al. [4i]).

Pancreas In evaluating diseases of the pancreas, MR is still inferior to CT [42]. No concrete results have been published so far on the use of contrast-enhanced MR imaging of the pancreas, and it remains to be seen whether dynamic gadopentetate dimeglumine-enhanced MR imaging will yield better results in the future. However, development of oral contrast agents is a first step toward improving the usefulness of MR imaging of the pancreas, because first the pancreas must be differentiated from the gastrointestinal tract [43].

Kidney Gadopentetate dimeglumine has limited application in the kidney. This is due in part to the high accuracy of the less expensive contrast-enhanced CT in tumor identification and the competition of nuclear scintigraphy in the evaluation of

HAMM

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250

kidney function. Contrast-enhanced MR imaging, for both tumor diagnosis and functional assessment, is best achieved when dynamic studies are performed in combination with bobus injection of gadopentetate dimeglumine [44-46]. Contrast administration allows better visualization of tumor extension within the kidney than imaging without contrast material does, but it does not improve the assessment of extrarenab tumor extension because of the high signal intensity of perirenal fat [45]. T2 (susceptibility) effects resulting from accumulation of the contrast agent in the renal pyramids and pebvicaliceab system produce signal-free areas, which also impair the interpretation (Fig. 4) [46]. This effect also limits quantitative evaluation of renal function.

Adrenal

Glands

The results of a preliminary clinical study of adrenal masses with gadopentetate dimeglumine have given rise to optimism for increased reliability with tissue characterization [47]. Although malignant tumors and pheochromocytomas show a significantly greater signal intensity than adenomas do in precontrast images, after administration of gadopentetate dimeglumine, only moderate enhancement and quick washout is observed in adenomas, whereas malignant tumors and pheochromocytomas show strong enhancement and slower washout. This information may therefore be useful for differentiation between benign and malignant adrenal masses.

Pelvis For diagnostic assessment of urinary bladder tumors, gadopentetate dimeglumine can be applied either intravesicalby or IV. On Ti -weighted images, intravesical administration (dilution i :50) leads to a clear distinction of the hypointense tumor from the signal-rich fluid in the bladder [48]. However, no major additional information relative to T2-weighted images is obtained. MR examinations of patients with urinary bladder tumors also show significant contrast enhancement in the tumors after IV application of gadopentetate dimeglumine [49]. Dynamic studies show that the signal intensity of tumors peaks within i 20 sec and remains elevated for up to 45 mm. Because of the plateaulike course of the signal enhancement and the better spatial resolution, Ti -weighted spin-echo sequences are to be preferred to Ti -weighted fast gradient-echo pulse sequences for staging of bladder tumors. Contrast-enhanced MR imaging appears to allow better tumor staging than do precontrast Ti - and/or T2-weighted pulse sequences. This is especially true for the distinction of superficial tumors from those infiltrating the muscle, because noninvolvement of the muscle layer is visualized as an intact hypointense line in the region underlying the tumor [48]. However, transurethral resection may lead to overstaging, because contrast-enhanced MR imaging cannot differentiate between inflammation and tumor. In the diagnosis of tumors of the uterus, gadopentetate dimeglumine-enhanced MR imaging can yield additional information in patients with endometriab carcinoma. Viable and necrotic areas are easier to distinguish on postcontrast than

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on T2-weighted precontrast images. In the evaluation of ovarian masses, gadopentetate dimeglumine improves the visualization of the internal tumor structure and may allow better distinction of inflammatory adnexab processes from malignant tumors on the basis of the strong contrast enhancement in the former.

Muscuboskebetab

System

The majority of clinical studies investigating gadopentetate dimeglumine-enhanced MR imaging concentrate on the diagnosis of bone and soft-tissue tumors [50-52]. Contrastenhanced MR imaging with Ti -weighted SE pulse sequences is more reliable in distinguishing different tumor components, in particular, necrosis and viable tumor tissue, than is precontrast imaging. Although marked improvement occurs after contrast application compared with the Ti -weighted precontrast image (in which contrast between tumor and soft tissue is often absent), the contrast is never as strong as in T2weighted precontrast sequences. However, IV application of gadopentetate dimeglumine reduces the contrast between enhancing tumor and signal-intensive fatty tissue and bone marrow. Contrast-enhanced MR imaging is therefore no substitute for precontrast spin-echo pulse sequences. More promising results are obtained with gadopentetate dimeglumine in distinguishing residual or recurrent sarcomas from posttherapy changes [53].

Lymph

Nodes

MR imaging has proved unreliable in the distinction of normal and neoplastic nodes by means of signal-intensity characteristics because relaxation times and proton densities of normal and metastatic nodes overlap [54]. Initial animal investigations have shown that iron oxide particles applied directly or via interstitial administration to a lymphatic vessel produce a loss of signal in normal lymph node tissue [55, 56]. Lymph node metastases, on the other hand, are characterized by a constant signal intensity and can thus be distinguished from unaffected lymph nodes. MR bymphography in combination with superparamagnetic iron oxide partides opens up promising future prospects for lymph node staging.

Future

Directions

The application of contrast agents in sites other than the CNS is still in its infancy. Considerable improvement in image quality is still needed to produce motion-free images. With novel formulations such as the nonionic isosmobar preparations, higher doses and/or prolonged infusion may further improve diagnostic information. Most importantly, without a gastrointestinal contrast agent, MR imaging will be unable to provide global examination of the abdomen. Once these technical hurdles have been overcome, the pace of development of contrast agents with organ and disease-specific applications will quicken.

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REFERENCES 26.

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1 . Aobinson JD, Crawford SC, Teresi LM, et al. Extracranial head and neck: preliminary experience with gadopentetate imaging. Radiology i989;172: 165-170

lesions of the enhanced MR

2. Crawford SC, Hamsberger HA, Lufkin RB, Hanafee WN. The role of gadolinium-DTPA in the evaluation of extracranial head and neck mass lesions. Radiol Clin North Am i989;27:219-242 3. yogI T, MarkI AF, Bruening A, Greves G, Kang K, Lissner JA. MA imaging of oropharynx and oral cavity: gadopentetate and fast imaging technique. Radiology i988;169(P):308 4. VogI T, Dresel ST. Schedel H, Greves G, Lissner J. MA imaging of the nasopharynx: fast imaging technique and gadopentetate studies. J Comput Assist Tomogr i988;i2:427-433 5. VogI T, Bruening A, Schedel H, et al. Paragangliomas of the jugular bulb and carotid body: MA imaging with short sequences and gadopentetate enhancement. AJNR i989;10:823-827 6. yogI T, Bruening A, Schedel H, et aI. MR imaging of paragangliomas of the jugular bulb and carotid body: fast imaging technique and gadopentetate. Radiology 1988;169(P):72 7. Garr DH. Paramagnetic contrast media for magnetic resonance imaging of the mediastinum and lungs. J Thorac Imaging i985;i :74-78 8. Nagele M, Hahn D, Seelos K, Ussner J. Gadopentetate-Kontastverstarkung in der kernspintomographischen Diagnostik thorakaler Raumforderungen. ROFO i988;149:69-75 9. Hahn D, Stelzer 5, Schmidt H, Lissner J. MA imaging of the mediastinum: value of Gd-DTPA and fast MA imaging. Radiology i988;i 69(P):219 1 0. de Roes A, Doombos J, van der Wall EE, van Voorthuisen AE. MR imaging of acute myocardial infarction: value of Gd-DTPA. AJR 1988:150:531-534 1 1 . Nishimura T, Kobayashi H, Ohara Y, et al. Serial assessment of myocardial infarction by using gated MA imaging and gadopentetate. AJR i989;153:715-720 12. de Roes A, van Rossum AG, van der Wall E, et aI. Aeperfused and nonreperfused myocardial infarction: diagnostic potential of gadopentetate enhanced MA imaging. Radiology 1989:172:717-720 13. Aehr RB, Peshock AM, Malloy CR, et al. Improved in vivo magnetic resonance imaging of acute myocardial infarction after intravenous paramagnetic contrast agent administration. Am J Cardiol i986;57:864-868 14. McNamara MT, Higgins GB, Ehman AL, Revel D, Sievers A, Brasch AG. Acute myocardial ischemia: magnetic resonance contrast enhancement with gadolinium-DTPA. Radiology i984;153: 157-i 63 1 5. Seiderer M, von Arnim T, Moser E, Rienmuller A, Hahn D. Gadopentetate in der kemspintomographischen Diagnostik chronischer Myokardinfarkte. ROFO i986;i45:666-673 1 6. Brown JJ, Higgins GB. Myocardial paramagnetic contrast agents for MR imaging. AJR i988;i51 :865-871 17. Schmiedl U, Ogan MD, Paajanen H, et al. Albumin labeled with Gd-DPTA as in intravascular, blood pool enhancing agent for MA imaging: biodistribution and imaging studies. Radiology i987;i62:205-2i0 1 8. Moseley ME, White DL, Wang 5, et al. Vascular mapping using albumin (gadopentetate), an intravascular MA contrast agent, and projection MA imaging. J Comput Assist Tomogr i989;i3:215-221 19. Heywang SH, Wolf A, Pruss E, Hilbertz T, Eiermann W, Permanetter W. MA imaging of the breast with gadopentetate: use and limitations. Radio!ogy i989;17i :95-1 03 20. Kaiser WA, Zeitler E. MA imaging of the breast: fast imaging sequences with and without gadopentetate: preliminary observations. Radiology i989;i70:68i-686 21 . Heywang SH, Hilbertz TH, Pruss E, et aI. Contrast material-enhanced MR imaging in patients with postoperative scarring and silicon implants. Radiology i988;169(P):352 22. Hilbertz TH, Heywang SH, Fink U, Permanetter W, Eiermann W. Contrast material enhanced MA imaging of the breast with histopathologic correlation. Radiology i988;i69(P):352 23. Saini 5, Stark DD, Brady TJ, Wittenberg J, Ferrucci JT Jr. Dynamic spinecho MA imaging of liver cancer using gadolinium DTPA: animal investigations. AJR i986;i47:357-362 24. Hamm B, Wolf KJ, Felix A. Conventional and rapid MA imaging of the liver with gadolinium-DTPA. Radiology i987;164:313-320 25. Nelson AC, Umpierrez ME. GhezmarJL, Bemardino ME. Delayed magnetic resonance hepatic imaging with gadolinium-DTPA. Invest Radio! 1988;

27.

28.

29. 30.

31

.

32.

33.

34.

35.

36.

37.

38.

39. 40.

41

42. 43.

44.

45. 46.

47.

48.

49.

.

MR

IMAGING

251

23:509-511 Freeny PC, Marks WM. Hepatic hemangioma: dynamic bolus CT. AJR 1986:147:711-719 Freeny PC, Marks WM. Pattems of contrast enhancement of benign and malignant hepatic neoplasms during bolus dynamic and delayed CT. Radiology i986;160:6i3-618 Mano I, Yoshida H, Nakabayashi K, Yashiro N, ho M. Fast spin echo imaging with suspended respiration: gadolinium enhanced MA imaging of liver tumors. J Comput Assist Tomogr i987;i 1 :73-80 Ohtomo K, Itai Y, Yoshikawa K, et al. Hepatictumors: dynamic MA imaging. Radiology 1987:163:27-31 Hamm B, Fischer E, Taupitz M. Differentiation of hepatic hemangiomas from hepatic metastases by using dynamic contrast enhanced MR imaging. J Comput Assist Tomogr i990;15:205-216 Hamm B, Taupitz M, Felix A, Wolf KJ. Dynamic contrast enhanced MR imaging of benign and malignant liver tumors at 0.5 and 1 .5 Tesla. In: Book of Abstracts: Society of Magnetic Resonance in Medicine, 1989. Berkeley, CA: Society of Magnetic Resonance in Medicine, 1989:91. Yoshida H, Itai Y, Ohtomo K, Kokubo T, Minami M, Yashiro N. Small hepatocellular carcinoma and cavernous hemangioma: differentiation with dynamic FLASH MA imaging with gadopentetate. Radiology i989;i 71: 339-342 Saini 5, Stark DD, Hahn PF, et al. Ferrite particles: a superparamagnetic MR contrast agent for enhanced detection of liver carcinoma. Radiology i987;i62:2i 7-222 Taupitz M, Hamm B, Wolf KJ. Efficacy of superparamagnetic iron oxide in MR imaging in liver tumors: in vivo and in vitro animal investigations. Radiology i989;i 73(P): 174 Fretz GJ, Elizondo G, Weissleder A, Hahn PF, Stark DD, Ferrucci JT. Superparamagnetic iron oxide enhanced MA imaging: pulse sequence optimization for detection of liver cancer. Radiology i989;i72:393-397 Stark DD, Weissleder A, Elizondo G, et aI. Superparamagnetic iron oxide: clinical application as a contrast agent for MA imaging of the liver. Radio!ogy i988;i68:297-30i Marchal G, van Hecke P. Demaerel P, et al. Detection of liver metastases with superparamagnetic iron oxide in 1 5 patients: results of MA imaging at i.5T.AJR i989;i52:771-775 Hahn PF, Stark DD, Weissleder A, Elizondo E, Saini 5, Ferrucci JT. Clinical application of superparamagnetic iron oxide to MA imaging of tissue perfusion in vascular liver tumors. Radiology 1990:174:361-366 Hahn PF, Weissleder A, Stark DD, Saini 5, Elizondo G, Ferrucci JT. MR imaging of focal splenic tumors. AJR 1988:150:823-827 Weissleder A, Hahn PF, Stark DD, et al. Superparamagnetic iron oxide: enhanced detection of focal splenic tumors with MR imaging. Radiology i988;i 69:399-403 Weissleder A, Elizondo G, Stark DD, et al. The diagnosis of splenic lymphoma by MA imaging: value of superparamagnetic iron oxide. AJR i989;i52: 175-i 80 Steiner E, Stark DD, Hahn PF, et al. Imaging of pancreatic neoplasms: comparison of MR and CT. AJR i989;i52:487-491 Laniado M, Kornmesser W, Hamm B, Glauss W, Weinmann HJ, Felix A. MA imaging of the gastrointestinal tract: value of Gd-DTPA. AJR 1988:150:817-821 Laniado M, Kornmesser W, Nagel A, et al. Spin echo, inversion recovery and fast imaging sequences with gadopentetate enhanced magnetic resonance imaging of renal tumors. In: Aunge VM, Glaussen C, Felix A, James AE, eds. Contrast agents in magnetic resonance imaging. Princeton, NJ: Excerpta Medica, 1986:162-166 Yashiro N, Suzuki M, Kishi H, ho M. Is gadopentetate necessary to stage renal adenocarcinoma? Radiology i988;169(P):193 Kikinis A, von Schulthess GK, Jager P. et al. Normal and hydronephrotic kidney evaluation of renal function with contrast enhanced MR imaging. Radiology i987;165:837-842 Kresin GP, Steinbrich W, Friedmann G. Adrenal masses: evaluation with fast gradient-echo MR imaging and gadopentetate enhanced dynamic studies. Radiology i987;i7i :675-680 Sparenberg A, Hamm B, Klaen A, Wolf KJ. Contrast material-enhanced MA imaging of bladder neoplasms: correlation with CT and pathologic staging. Radiology i989;i73(P):176 Neuerburg JM, Bohndorf K, Sohn M, Teufi F, Guenther AW, Daus HJ. Urinary bladder neoplasms: evaluation with contrast enhanced MR imag-

252

HAHN

ing. Radiology i989;172:739-743 Reiser M, Bohndorf K, Niendorf HP, Friedmann G, Erlemann A, Kunze V. Preliminary results with gadolinium-DTPA in magnetic resonance tomography of bone and soft-tissue tumors. Radio!oge i987;27:467-472 51 . Pettersson H, Eliasson J, Egund N, et al. Gadolinium-DTPA enhancement of soft tissue tumors in magnetic resonance imaging: preliminary clinical experience in five patients. Skeletal Radio! i988;17:3i9-323 52. Erlemann A, Aeiser MF, Peters PE, et al. Musculoskeletal neoplasms: static and dynamic gadopentetate enhanced MR imaging. Radiology 1989:171:767-773 53. Kim E, Abello A, Holbert JM, et al. Differentiation of therapeutic changes

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50.

Gastrointestinal Peter

Contrast

55.

56.

1991

from recurrent or residual musculoskeletal sarcomas with gadopentetate enhanced MA imaging. Radiology i989;173(P): 104 Bottomley PA, Hardy RE, Argersinger RE, Allen-Moore G. A review of iH nuclear magnetic resonance relaxation in pathology: are Ti and T2 diagnostic? Med Phys i987;i4: 1-37 Weissleder A, Elizondo G, Josephson L, et al. Experimental lymph node metastases: enhanced detection with MR lymphography. Radiology i989;171 :835-839 Hamm B, Taupitz M, Wagner 5, Hussmann P. Wolf KJ. MR lymphography: initial experimental results with superparamagnetic iron oxide. Radiology i989;i 73(P):274

Agents

F. Hahn

There is widespread agreement that development of a gastrointestinal contrast agent will be necessary for abdominab MR imaging to progress. For example, one reason that MR imaging of the liver has not been adopted more widely, despite evidence that it can compete favorably with CT in detecting and characterizing focal hepatic lesions, is that examinations performed to stage cancer in the liver routinely miss three times as many important extrahepatic lesions as CT does [i 2]. Although issues of noise and spatial resolution must be confronted, bowel marking, with confident delineation of the pancreas and paraaortic area, seems an essential prerequisite for expanding the use of MR beyond the liver. In general, MR contrast agents for use in the gastrointestinal tract may be classified according to whether they contribute signal to the bowel lumen (positive contrast agent) or reduce signal normally associated with the bowel lumen (negative contrast agent). This classification must be used cautiousby, however, because changes in concentration, technical factors, and physiologic conditions can change a positive contrast agent into a negative agent. For example, although gadolinium compounds usually increase signal intensity by shortening Ti higher concentrations of these compounds and more heavily T2-weighted imaging can result in predominance of the T2-shortening effect, resulting in a decrease in signal intensity. Thus, an agent that began in the stomach as a positive agent might, after concentration in the colon by physiologic water resorption, become a negative agent. A second useful distinction can be made between contrast agents intended to mix with bowel contents, so-cabled miscible agents, and those intended to replace bowel contents, immiscible agents. Table i displays many of the materials that have been tested as gastrointestinal contrast agents, separated according to the positive-negative and miscibleimmiscible characteristics. ,

,

Positive

54.

February

Agents

Positive contrast netic substances,

agents for MR imaging include which mix with bowel contents,

paramagand fats

and oils, which must replace bowel contents in order to mark the bowel. Although fatty materials, with inherently short Ti, were among the earliest materials investigated for oral contrast in MR imaging [3], delivery of sufficient volume to replace all of the small-bowel contents has not been reported. Gadopentetate dimeglumine has been developed for use as an oral contrast agent (Fig. i). With conventional spin-echo and gradient-echo techniques and doses on the order of 500-700 ml of 1 mmol/l solution, gadopentetate dimeglumine is a positive contrast agent that mixes with gastrointestinal tract contents, shortening Ti [4]. In order to ensure delivery deep into the small bowel, gadopentetate dimeglumine is given with a nonabsorbable sugar such as i 5-30 g of mannitol. Positive contrast agents can increase image noise through motion of the bowel during imaging. Therefore, investigators using oral gadopentetate dimeglumine have obtained best results with fast gradient-echo imaging, abdominal compression, and pharmacologic reduction of bowel peristabsis. Other paramagnetic substances have been investigated as oral contrast agents. The first proposed for this purpose was ferric ammonium citrate [5], widely available as the hematinic in Geritol (Beecham, Bristol, TN). Ferric ammonium citrate produces about one fifth as much Ti shortening as gadopentetate dimeglumine does at equal concentrations. At first only limited delivery offerric ammoniurn citrate into the small bowel was achieved. Recently, a mixture of ice cream (30%), corn oil (20%), milk (38%), and ferric ammonium citrate (1 2%) has been found to be well tolerated and to achieve positive gastroduodenal and small-bowel marking [6]. Negative

Agents

Negative contrast agents include clays, barium sulfate, iron oxides, perfluorocarbons, and gas-evolving pellets. The clay mineral kaolin used to be in the nonprescription medication Kaopectate (Upjohn, Kalamazoo, Ml). Kaolin is on the U.S. Food and Drug Administration list of substances generally recognized as safe for use as an indirect food additive. Kaolin produces diamagnetic Ti and T2 shortening in aqueous sus-

Advances in contrast-enhanced MR imaging. Nonneurologic applications.

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