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The early effects of in vivo platinum-rhodamine (PtR) chemotherapy on tumor high-energy phosphorous metabolism was investigated using phosphorus-31 (31P) magnetic resonance spectroscopy (MRS), magnetic resonance imaging (MRI), and histologic examination in a subcutaneously implanted hamster melanoma model. PtR was chosen because of its potential antimitochondrial and antineoplastic properties. All melanomas were clearly observed on both T1- and T2-weighted images (T1WI and T2WI), with viable tumor regions generally characterized by low to intermediate intensity on T1WI and high intensity on T2WI. Necrotic regions were more variable in appearance, depending on the amount of cystic fluid and hemorrhage. No changes were detected on either T1WI or T2WI within 90 minutes of a tumoristatic dose of PtR (40 mg/kg) by visual examination, but slight differences were seen on calculations of relative signal intensities. However, this same dose of PtR caused a 50% drop in tumor ATP and phosphocreatine content (relative to Pi) measured by 31P MRS within 90 minutes of drug injection. Magnetic resonance spectroscopy appears to offer a sensitive means of detecting the earliest biochemical effects of chemotherapeutic agents that are known to affect tumor bioenergetics.

Comparison between computed tomography and nuclear magnetic resonance imaging in 17 patients with intracranial hematomas indicates a distinct role for NMR in evaluating the stable patient with hematoma. NMR is useful for delineating the extent of the hematoma, the relationship of the hematoma to brain anatomy, and the presence of hematoma at a time when the hematoma is isodense on CT.

High-field magnetic resonance (MR) imaging was performed in three patients with clinically diagnosed acute disseminated encephalomyelitis (ADEM). Contrast enhanced CT was normal in all cases. Magnetic resonance demonstrated multiple foci of demyelination in the brain stem, cerebrum, and cerebellum. Lesions were characteristic, in that they were relatively few in number, frequently present in the brain stem and posterior fossa, nonhemorrhagic, asymmetric, and easily correlated with clinical symptoms and signs. Follow-up MR in one patient who had clinically improved after steroid therapy showed marked resolution of previously documented lesions. Typical MR findings in combination with the appropriate clinical presentation can confirm the diagnosis of ADEM, obviate other more invasive diagnostic tests, identify the extent and sites of involvement, and follow response to therapy.

Nineteen patients with proven pancreatic disease and 50 control subjects were examined by magnetic resonance (MR) using a variety of spin echo and inversion recovery techniques. The MR results were then compared with CT scans. The normal pancreatic head, body, and tail were identified by MR in approximately 60% of patients. Pancreatic adenocarcinoma and retroperitoneal lymphoma were detected using morphologic criteria similar to those used in CT. Differentiating bowel from pancreas was difficult on MR in patients with little retroperitoneal fat, and tissue relaxation times were usually not helpful in differentiating adenocarcinoma or lymphoma from normal pancreatic tissue. However, MR intensity, T1, and T2 were useful in differentiating pancreatic islet cell tumors from normal pancreatic tissue. MR accurately identified retroperitoneal invasion, vascular involvement, and liver metastases. In pancreatitis, tissue T1 and T2 relaxation times were prolonged and complications such as ductal dilatation, pseudocyst, phlegmon, and ascites were identified. Small pancreatic calcifications were not detected by MR. Pancreatic iron overload was seen in patients with hemochromatosis. Although respiratory motion and spatial resolution are currently limiting factors, MR is a versatile and unique modality for the evaluation of pancreatic disease.

Experimental animal models of hepatitis, fatty liver, and hepatic iron overload were evaluated using a 3.5-kGauss nuclear magnetic resonance (NMR) imaging system. Increases in image intensity measurements and in T2 relaxation times equalled the sensitivity of histologic findings for the detection of early stages of hepatitis. A significant shift in T1 relaxation times characterized the early stages of hepatic necrosis. Liver triglyceride content correlated significantly with increases in NMR intensity measurements (p less than 0.01); however, changes in liver water content had a much greater influence on intensity, T1, and T2. Thus, it may be possible to distinguish hepatitis from benign fatty liver. Liver iron content correlated with decreases in NMR intensity measurements (p less than 0.001), and iron levels as low as 1.2 mg/g were detected. NMR may more specifically identify hepatocellular iron overload than do other techniques that do not distinguish hepatocellular from reticuloendothelial iron.

This review includes the initial experience with NMR imaging of the liver, spleen, and pancreas at the University of California, San Francisco, using a prototype 0.35 Tesla system. This experience shows great promise for detection of hepatic metastases using T1-weighted pulse sequences. T2-weighted pulse sequences appear sensitive for detecting cavernous hemangioma of the liver and may allow tissue specific discrimination of the benign lesion from cancer. NMR is also suitable for evaluating diffuse metabolic alterations and is sensitive and specific for the diagnosis of iron overload. Detection of fatty liver requires use of chemical shift techniques as conventional NMR imaging pulse sequences are relatively insensitive. Motion artifacts and lack of an effective bowel contrast agent limits imaging of the pancreas and retroperitoneum, where CT remains the procedure of choice. The normal spleen has longer T1 and T2 relaxation times than liver or pancreas and NMR has not been successful in diagnosing splenic metastases or lymphoma on a routine basis. We conclude that NMR imaging will be valuable in the diagnosis of focal liver disorders; until fast scan techniques and effective magnetic contrast agents are available for oral and/or intravenous use, other abdominal applications will remain limited.

Computed tomography (CT) and magnetic resonance (MR) imaging were performed in ten patients with paranasal sinus hemorrhage after trauma. Acute or subacute hemorrhage was detected on MR images by using T1- and T2-weighted imaging to identify the chemical state of the blood and to differentiate blood from mucosal thickening and sinus effusion. Surgical proof of intrasinus hemorrhage was obtained in only two cases. Displaced fractures, associated cerebral contusions, and traumatic encephalocele were well shown on MR imaging. Nondisplaced and minimally displaced fractures were better evaluated with CT.

Fifteen patients with clinical presentations compatible with idiopathic inflammatory orbital pseudotumor were examined by CT and MR imaging to determine if MR could add specificity to the CT appearance of this entity. MR was performed on a 1.5 T system, using surface-coil and head-coil techniques. Idiopathic pseudotumor was confirmed in nine patients on the basis of response to steroid therapy in the absence of local cause or systemic illness. One other patient had biopsy-proven idiopathic pseudotumor. Five patients proved to have other orbital entities, including metastases, infectious myositis, hemorrhage, and orbital sarcoid. In all 10 patients with confirmed pseudotumor, CT and MR were abnormal. MR abnormalities in 10 of 10 patients with pseudotumor were hypointense to fat and isointense to muscle on T1-weighted images. On T2-weighted images the lesions of pseudotumor were isointense or only minimally hyperintense to fat in nine of 10 cases; in one case, the enlarged muscle was markedly hyperintense to fat. The MR signal intensity of pseudotumor was similar to that found in infectious myositis and sarcoid. These findings contrasted to the MR appearance of the other disease entities examined. Metastases appeared markedly hyperintense to fat on T2-weighted images, while hematoma was hyperintense to muscle and isointense to fat on T1-weighted images and markedly hyperintense to fat on T2-weighted images. In our preliminary series, surface-coil MR appears to add specificity to the CT appearance of orbital pseudotumor.

The magnetic resonance (MR) features of primary and metastatic hepatic tumors were analyzed and compared with CT findings in 28 patients. MR images were obtained on a 0.35-Tesla superconducting magnet using a variety of spin echo and inversion recovery imaging techniques. The normal liver appeared homogeneous and of moderate intensity. Tumors typically appeared as masses of increased intensity on spin echo images and diminished intensity on inversion recovery images. Tumors had prolonged T1 and T2 times, which varied in different types of tumors and within regions of a single tumor. A specific T1 and/or T2 time could not be ascribed to any tumor. Tumor intensity varied greatly depending on the imaging techniques employed, becoming isointense with normal liver on some imaging sequences. MR and CT detected lesions equally well, but internal architecture and the relationship of tumors to hepatic vascular structures were better displayed on MR.

In patients with central nervous system problems, a comparison of the results obtained with high-field MRI (1.5 T) to those achieved with more conventional imaging studies, primarily CT, reveals significant improvement in the demonstration of various abnormalities by MRI (56.5%), with increased specificity in some (29.5%). High-field MRI provides advantages over CT by providing both multiplanar images and superior contrast resolution. The diagnostic specificity of MRI is increased when acute, subacute, and chronic hematomas are visualized and when flowing blood within vessels is demonstrated in addition to the location and extent of the disease process. In this series, MRI produced a more accurate diagnosis in 8.7% of cases, revealed clinically unexpected abnormalities in 3.9% of cases, and was less invasive or avoided the risk of complications in 17.4% of cases. Despite the success of MRI, CT continues to play an important role in demonstrating calcification and contrast enhancement, and in evaluating patients in whom MRI is contraindicated or impossible because of an unsuitable clinical state.

The sensitivity and specificity of CT and high-field MR (1.5 T) were compared in an evaluation of 30 patients with head injuries (eight acute, 15 subacute, and seven chronic). By using T1- and T2-weighted images, it was possible to detect various stages of hemorrhages and their separation from edema. In the acute category, both CT and MR showed acute hemorrhagic lesions, but only MR demonstrated coexisting chronic hematomas or small hypothalamic or brainstem infarctions. MR was far superior to CT in the detection and characterization of subacute injuries, including shearing injuries, hemorrhagic and nonhemorrhagic contusions, and subdural hematomas. In chronic injury, atrophy was demonstrated by both techniques, but only MR showed parenchymal abnormalities and old hemorrhages. Its ease in monitoring patients and its greater speed make CT the procedure of choice for the evaluation of acute cases. CT also provides information that is useful in deciding between surgery and medical management. However, the more precise anatomic depiction of MR and its sensitivity to parenchymal abnormalities make MR the key to correct prognosis in patients with subacute or chronic injury.

Although iophendylate (Pantopaque) has been largely replaced by water soluble agents for myelography, retained intracranial or intraspinal Pantopaque remains a common occurrence. Pantopaque has signal characteristics similar to fat with both short T1 and T2 relaxation times. In vitro measurements revealed T1 = 170 ms and T2 = 27 ms. Spine radiography is recommended in patients with a history of previous myelography and magnetic resonance abnormalities similar to fat.

Magnetic resonance (MR) imaging distinguished hepatitis from fatty liver and cirrhosis in a woman with a history of alcohol abuse. Anatomic and physiologic manifestations of portal hypertension were also demonstrated by MR.

Fifty-nine cases in which surface coil MR imaging of the orbit was performed were reviewed. MR imaging was performed with spin-echo techniques at 1.5 T with both short repetition time/echo time (TR/TE) and long TR/TE sequences in all cases. In all patients short TR/TE images were obtained with small-diameter surface coils; long TR/TE images were usually obtained with a standard head coil. Surface coil MR appears to be an important adjunct in state-of-the-art orbital imaging. Orbital MR imaging may be most useful, providing information not available on computed tomography (CT), in identifying lesions in the orbital apex, superior orbital fissure, and optic canal; differentiating inflammatory pseudotumor from malignancy in clinically similar patients; characterizing lesions containing hemorrhage or other paramagnetic material; defining the posterior extent of optic pathway gliomas; and detecting abnormal flow in intraorbital vascular structures. CT seems to be superior to MR imaging in the evaluation of small perioptic meningiomas, especially those that are calcified.

A ring of enhancement immediately posterior to the optic chiasm has been observed on postcontrast, thin section, axial CT. This ring represents enhancement of the infundibular recess' wall and does not have any pathologic significance. Magnetic resonance confirmed this anatomic interpretation.

The NMR and CT findings in 22 patients with primary brain stem tumors were compared to determine the value of each study in identifying, and delineating the extent and relationships of the tumor to brain anatomy. NMR was found to be distinctly superior to CT in showing involvement of the medulla and upper cervical cord. NMR eliminates the need for intrathecal enhanced metrizamide CT, and in the future should be the only initial diagnostic test needed for the evaluation of intrinsic brain stem tumors.

A case of superficial siderosis of the central nervous system secondary to bleeding from an ependymoma is presented. High-field magnetic resonance imaging showed marginal hypointensity of the cervical cord, medulla oblongata, pons, mesencephalon, anterior cerebellar and basal cerebral surfaces, and cranial nerves (II, V, VIII). These findings were evident in the T2 weighted images.

Twelve patients with 15 separate, spontaneously hemorrhagic, intracranial malignant lesions (seven primary gliomas, eight metastatic lesions) were examined with spin-echo magnetic resonance imaging at 1.5 T, and with computed tomography. The signal intensity patterns of these lesions, as seen on both short repetition time (TR)/short echo time (TE) and long-TR/long-TE spin-echo pulse sequences, were compared with the previously described appearance at 1.5 T of non-neoplastic intracerebral hematomas. The images of hemorrhagic intracranial malignancies showed notable signal heterogeneity, often with identifiable nonhemorrhagic tissue corresponding to tumor; diminished, irregular, or absent hemosiderin deposition; delayed hematoma evolution; and pronounced or persistent edema, compared with non-neoplastic hematomas. The demonstration of these characteristics in the appropriate clinical setting may suggest malignancy as the cause of an intracranial hematoma.

Low field strength (0.12 Tesla resistive) and high field strength (1.0, 1.4, or 1.5 Tesla superconductive) magnetic resonance imagers were compared for their ability to detect central nervous system lesions. Sixteen adult patients with known lesions and three normal volunteers were studied. Contrast-enhanced computed tomography was used as the standard. The data demonstrate that imaging at high magnetic field strength is superior to low field strength imaging for the detection and delineation of lesions. This finding can be explained by the superior signal-to-noise ratio achievable at the higher magnetic field strengths. High field MR imaging was also found to outperform CT in demonstrating anatomic details and relationships. It is predicted that the use of low saturation (e.g., long TR spin echo technique) will make the gain in contrast-to-noise ratio even more significant.

Two patients with surgically and angiographically proved partially thrombosed giant aneurysms of the middle cerebral artery were studied with computed tomography (CT) and magnetic resonance (MR) imaging. MR and histopathologic findings were correlated. The central location of methemoglobin, with its high intensity (surrounding the patent lumen, seen as signal void), in giant aneurysms is directly opposite the initial peripheral appearance of methemoglobin in extra-aneurysmal intracerebral hematomas. More peripherally, the thrombosed portion of the lumen is layered with intensities that represent stages of clot (methemoglobin and hemosiderin). Three characteristics enable differentiation of giant aneurysms from intracerebral hematoma: signal void in residual patent lumen; laminated, staged thrombus with intervening layers of hemosiderin and methemoglobin that is initially centrally, rather than only peripherally, located; and signal void in the vessel from which the aneurysm arises. Hemorrhage from prior bleeding can be readily identified and separated from perianeurysmal edema on MR images. MR appears to be a specific, noninvasive method for diagnosing partially thrombosed giant intracranial aneurysms and is superior to CT and angiography in characterizing these lesions.

Over a 6-month period, 157 patients, 89 of whom had central nervous system tumors, were examined on a prototype 0.12 T resistive nuclear magnetic resonance (NMR) imaging unit. All of the patients had computed tomography (CT), which was used as a standard to which the NMR findings were compared. Studies were done primarily by saturation-recovery technique with short repetition times. The signal intensity with saturation-recovery technique did not allow differentiation among most tumor types. Location, extent, and morphology helped to some extent in attempts at differentiation. In the multiplanar mode, NMR compared favorably to CT with regard to lesion detection. Limited early experience suggests that NMR also may detect some lesions when the CT is negative and may detect additional lesions when one or more are present. The NMR examination was well tolerated by selected patients.

Thirteen orbital lesions in 12 patients were evaluated with both conventional spin-echo magnetic resonance (MR) imaging and phase-dependent proton spectroscopic imaging. This technique, which makes use of small differences in the resonant frequencies of water and fat protons, provides excellent high-resolution images with simultaneous chemical shift information. In this method, there is 180 degrees opposition of phase between fat protons and water protons at the time of the gradient echo, resulting in signal cancellation in voxels containing equal signals from fat and water. In this preliminary series, advantages of spectroscopic images in orbital lesions included better lesion delineation, with superior anatomic definition of orbital apex involvement; more specific characterization of high-intensity hemorrhage with a single pulse sequence; elimination of potential confusion from chemical shift misregistration artifact; further clarification of possible intravascular flow abnormalities; and improved apparent intralesional contrast.

Appropriate spin-echo (SE) pulse sequence parameters generate magnetic resonance (MR) images with very high gray matter/white matter contrast in neonates and young infants. In these young patients, long SE sequences with a repetition time of 3,000-3,500 msec and multiple echoes with the longest echo time of 120-160 msec are employed to yield high-contrast images. A high-contrast MR image of a 1-month-old infant is presented.

Six patients with pituitary abnormalities and three normal volunteers were evaluated by high field superconductive (1.0, 1.4, or 1.5 Tesla) magnetic resonance (MR) imaging, low field resistive (0.12 Tesla) MR imaging, and contrast-enhanced, high-resolution CT. Four macroadenomas, one microadenoma, and one empty sella were demonstrated. Their morphology and anatomic relationship to the visual pathway and the internal carotid and anterior cerebral arteries were best demonstrated by high field MR imaging. The low field resistive MR studies were least effective in showing the lesions.

Intracranial brain abscess was produced in three monkeys by embolization of a small pledget of polyvinyl alcohol (PVA) soaked in a broth of Staphylococcus aureus. Imaging of the chronic stable abscess was performed on the General Electric 8800 CT unit (Milwaukee, Wis.) and a 1.4 T superconducting small bore imaging system. Magnetic resonance imaging included saturation recovery, inversion recovery, and spin echo techniques. MR imaging was also performed after paramagnetic enhancement using gadolinium-DPTA (Gd-DTPA). Our results show that paramagnetic enhancement with T1-weighted imaging adds specificity and enables rapid assessment of abnormalities of the blood-brain barrier. T2-weighted imaging without paramagnetic enhancement was very sensitive in defining areas of abnormality in the brain but in our experiment lacked specificity. T2-weighted imaging with Gd-DTPA demonstrated no obvious change in the appearance of the lesion. The combination of T1-weighted Gd-DTPA and T2-weighted imaging appeared complementary in our experiment, and these images correlated well with the pathologic findings.

Nuclear magnetic resonance (NMR) imaging of intraabdominal vascular anatomy and the effect of various lesions on retroperitoneal and splanchnic vessels was assessed in 67 patients and volunteers using a superconducting magnet (0.35 tesla) and the spin-echo imaging techniques. Because of the low signal generated by flowing blood in most images, blood vessels, including intraparenchymal vessels, were well demonstrated. Clear delineation of the splenic vein facilitated visualization of the normal pancreas and pancreatic masses. Variation in the size and shape of the inferior vena cava and portal venous system reflected constricting and mass lesions. Preliminary observations from this initial experience suggest conspicuity of splanchnic vessels out of proportion to the current spatial resolution of NMR imaging due to the marked natural contrast between flowing blood and solid organs.

Eleven patients with pancreatic islet cell tumors smaller than 2.5 cm were examined by use of computed tomography (CT) and new scanning protocol. Seven of 11 tumors were localized and CT accurately assessed multiple lesions, retroperitoneal invasion, or liver metastases when present. CT is now the initial imaging procedure of choice for diagnosis and staging of islet cell tumors. Nuclear magnetic resonance can distinguish islet cell tumors from normal retroperitoneal structures and appears to be a promising new pancreatic imaging modality.

The T2 and pseudodensity (proportional to proton density) of intracranial hemorrhages and normal white matter were calculated. The mean T2 (+/- standard deviation) was 120 +/- 62 for hemorrhage and 61 +/- 11 for white matter. Pseudodensity values were normalized to a white matter value of 1, and the value for hemorrhage was 1.56 +/- 0.28. These values were used to determine which components of hemorrhage-white matter contrast are due to T1, T2, and density. The results indicate that on spin-echo (SE) images obtained with a long repetition time (TR)/short echo time (TE) (2,500/0-20 [TR msec/TE msec]), the contrast is mainly due to density differences, with a modest T2 contribution on 20-msec-TE images and nearly no T1 component. At 600/0-20, the contrast continues to be largely determined by density differences, again with a modest T2 component on 20-msec-TE images. If the T1 of hemorrhage is extremely short, the T1 component of contrast on 600/0-20 SE images will be somewhat greater than the density component. Because contrast on short TR/short TE images may be largely or entirely determined by pseudodensity or T2, it is inaccurate to refer to 600/20 images as "T1-weighted". The assumption that high signal intensity at this sequence implies a "short T1" will lead to misleading conclusions.

Experimental animals that had been given excess iron in their diet were studied by magnetic resonance (MR) imaging in vivo and by magnetic resonance (MR) spectroscopy in vitro. Hepatic iron overload in patients with transfusional iron excess was studied by MR imaging, and isolated iron protein fractions were studied in vitro by MR spectroscopy. The spin echo image intensity of livers with iron overload was decreased because of the extreme decreases in T2 compared with normal; T1 was decreased only moderately. The relaxation rates 1/T2 and 1/T1 both showed a linear relationship to hepatic iron levels. Ferritin solutions showed moderate decreases in T2 and mild decreases in T1. The T2 relaxivity of ferritin, which is due to the iron core rather than the apoferritin protein shell, does not appear sufficient to account for the extreme decrease in T2 observed in hepatic iron overload. Low molecular weight cytosol iron is present in lower concentrations than ferritin but potentially has much greater relaxivity and may contribute to the MR findings. These techniques may be useful in other studies of iron metabolism.

While magnetic resonance imaging (MRI) is not a screening examination in the search for metastatic disease, it has already demonstrated its value when performed as a carefully directed study to detect focal hepatic lesions. In the past 18 months we have encountered nine patients (six men, three women--ages 14-66) with a variety of primary tumors (renal cell carcinoma, two; colon carcinoma, two; hepatocellular carcinoma, two; pancreatic carcinoma, one; pheochromocytoma, one; rhabdomyosarcoma, one) whose MR scans revealed hepatic metastases after normal or nondiagnostic computed tomographic (CT) scans. The lesions were most clearly demonstrated using spin echo (SE) technique with recovery times (TR) of 2.0 seconds and delay times (TE) of 56 msec; metastases usually imaged with greater signal intensity than surrounding liver parenchyma. Lesions were solitary in three patients, multiple in six, and were found in all hepatic lobes without any specific location predominating. Pathologic confirmations of MR diagnoses were available in six of nine patients. In two patients, CT scans were of poor technical quality because streak artifacts from surgical clips obscured portions of the liver. In one patient iodinated contrast medium could not be given. In the remaining six patients CT scan quality was acceptable. This report is not a comparison study of the two modalities. We simply present nine patients in whom metastases were not detected by CT for various reasons but were found by MRI using SE technique.

Twenty-five newly diagnosed intracranial meningiomas were evaluated with magnetic resonance (MR) imaging at 1.5 T, and findings were correlated with those of computed tomography (CT), angiography, and tumor histology. Meningiomas were generally hypointense on T1-weighted images and hyperintense on T2-weighted images relative to cerebral white matter. In comparison with the cortex, they were hypointense or isointense on T1-weighted images and isointense or hyperintense on T2-weighted images. A heterogeneous texture produced by tumor vascularity, calcifications, cystic foci, or an intrinsic speckled or mottled pattern was observed in all but the smallest lesions. An interface between meningioma and brain was uniformly present and consisted of a cerebro-spinal fluid cleft, vascular rim, or dural margin. Large meningiomas were associated with arcuate displacement and compression of adjacent gyri. MR imaging was superior to CT in defining extracerebral tumor location, tumor vascularity, arterial encasement, and venous sinus invasion. No correlation was found between the appearance on MR images and the pathologic classification.

One hundred and forty patients with cerebral neoplasms were examined in a 0.12-Tesla prototype resistive NMR proton imaging device by partial saturation technique. NMR was superior to CT in tumor and edema localization and equal to CT in tumor and edema detection. NMR, however, was not able to clearly separate tumor from edema, a separation that contrast enhanced CT achieved.

A simple method to test new gadolinium complexes potentially useful as enhancement agents for magnetic resonance imaging was developed. Healthy rats underwent scintigraphy with two potential hepatobiliary agents, diethyl IDA and diisopropyl IDA complexed with gadolinium-153. Control products included 153Gd DTPA, 153GdCl3 and technetium-99m diethyl IDA. As shown scintigraphically, 153Gd IDA complexes were partially excreted by urinary and hepatobiliary excretion early after administration. These findings paralleled significant reduction in 1H T1 values of excised livers. However, these agents exhibited prolonged 153Gd whole-body retention. The prolonged tissue distribution of 153Gd activity in animals given 153Gd diethyl IDA did not differ significantly from that observed in animals given GdCl3, and could be attributed to chemical instability or reticuloendothelial uptake. The scintigraphic method permits screening of gadolinium complexes in animals by showing mass balance, kinetics, distribution, and effective stability. Biologic effects of tracer or pharmacologic levels can be compared with those of carrier-free and carrier-added pharmaceuticals.

The magnetic resonance (MR) examinations of 18 patients with dilated bile ducts were reviewed retrospectively to determine the capability of MR to demonstrate biliary dilatation, assess MR appearance of the dilated biliary tract using spin-echo techniques, and define the optimal MR imaging parameters (repetition time [TR] and echo time [TE]) for its demonstration. On images with short TR (0.5 sec) and TE (28 msec), the dilated intrahepatic and intrapancreatic bile ducts usually had lower signal intensity compared with the surrounding liver or pancreas; on images with long TR (2.0 sec) and TE (56 msec), they had higher signal intensity. Because of the observed variation in percentage of contrast between dilated bile ducts and surrounding liver and pancreas, two imaging sequences are recommended to obtain reliable demonstration of dilated intrahepatic and intrapancreatic bile ducts. The dilated common bile duct at the level of the hepatic hilus is best seen with a short TR and TE.

A retrospective comparison was made of the capability of magnetic resonance (MR) imaging and CT to display and characterize pathologic abdominal fluid collections. Fluid collections in 41 patients were analyzed: ascites (seven patients), hematoma (five), pancreatic pseudocyst (four), biloma (two), abscess (four), simple renal cyst (nine), hemorrhagic renal cyst (two), hydronephrosis (four), hemonephrosis (two), and cystic metastases (two). Most fluid collections were equally demonstrated by the two modalities. Walls around fluid collections were better demonstrated CT. Six fluid collections appeared heterogeneous on MR but were homogeneous or nearly so on CT.

Ten patients with intracerebral metastases from malignant melanoma were evaluated with magnetic resonance (MR) imaging performed at 1.5 T using spin-echo techniques. On the basis of histopathologic findings in three of 10 cases and CT appearances in all 10 cases, three patterns were identified on analysis of MR signal intensities in both short repetition time/echo time (TR/TE) and long TR/TE spin-echo scans. In comparison to normal cortex, nonhemorrhagic melanotic melanoma appeared markedly hyperintense on short TR/TE images and isointense, mildly hypointense on long TR/TE images. Nonhemorrhagic, amelanotic melanoma appeared isointense or mildly hypointense on short TR/TE and isointense or mildly hyperintense on long TR/TE images. Hemorrhagic melanoma varied in appearance, depending on the stage of hemorrhage. Melanotic, nonhemorrhagic melanoma can be distinguished from early and late subacute hemorrhage by its signal intensity on long TR/TE images. Spin-echo MR appears to be the method of choice for diagnosing melanotic metastases.

Magnetic resonance (MR) imaging, proton MR spectroscopy, and biochemical analysis were performed to investigate MR signal intensity (SI) differences between concentrated and dilute gallbladder bile of seven fasting and five sincalide-treated dogs. MR images revealed high SI from bile of fasting dogs and low to medium SI in sincalide-treated dogs when spin-echo (SE) pulse sequences with repetition rates of 0.5 and 2.0 sec were used. Proton MR spectra were similar for fasting and sincalide-treated dogs. In fasting dogs, water content in the bile was slightly lower, and cholesterol, phospholipid, and bile acid concentrations were higher. More than 90% of proton signals in all Fourier transform free induction decay spectra emanated from water molecules, and no lipid proton resonances were detected in Fourier transform SE spectra after tau delays of 7 msec. These results indicate that the differences in SI are caused by alterations in relaxation times of water protons, possibly resulting from the interactions of water protons and macromolecules.

Gadolinium-DTPA, a paramagnetic contrast agent that distributes throughout the body in a manner similar to diatrizoate, was intravenously administered to a monkey with a hematogenously induced experimental intracranial abscess. Contrast enhanced computed tomography (CT) and gadolinium enhanced saturation-recovery nuclear magnetic resonance (NMR) were both performed immediately and repeated after a 30 min delay. The NMR images revealed marked ring enhancement at a time when CT showed a nodule. Both imaging modalities were analyzed with respect to the pathological specimen. Gadolinium-DTPA may be an effective agent for imaging alterations of the blood-brain barrier.

High field magnetic resonance (MR) imaging enables us to demonstrate the evolution of cerebral venous thrombosis. Initially, absence of a flow void and collateral venous channels are seen on T1 weighted images (WI). On T2WI thrombus appears hypointense. Hyperintensity is noted in an intermediate stage of thrombosis first on T1WI and later on T2WI. In the late stages recanalization of the vessel occurs with reappearance of the flow void. These findings are specific for venous thrombosis. High field MR may be the imaging modality of choice in the diagnosis of venous thrombosis.

Eleven patients with sickle cell disease and neurological symptoms underwent MRI examination. Cerebral infarcts of two types were found, those in the vascular distribution of the middle cerebral artery and those in the deep white matter. In the patient whose hydration and whose oxygenation of erythrocytes has been treated, MRI offers diagnostic advantages over arteriography and CT.

The effect of periportal collagen deposition on magnetic resonance images and T1 and T2 relaxation times was studied in the rat. Hepatic cirrhosis was induced in 29 rats by chronic intraperitoneal thioacetamide injections. Another 14 rats in which liver abnormalities did not develop were used as controls. The rats were imaged using a small-bore resistive magnet. Histologic correlations and hydroxyproline measurements were performed to document the changes in periportal collagen deposition. The T1 and T2 relaxation times, determined both in vivo and in vitro with spectroscopy, were compared between the normal group and the group with moderate to severe histologic evidence of cirrhosis. The deposition of two to four times the normal amount of collagen in the liver did not affect the T1 or T2 relaxation time. Relatively pure periportal collagen fibrosis does not appear to affect the magnetic resonance image or T1 or T2 relaxation times of the rat liver.

Magnetic resonance (MR) images of the lumbar spine from 150 patients were retrospectively reviewed. In 14 of these patients, at 18 disk levels, a vacuum phenomenon (VP) had been identified on plain radiographs and/or computed tomographic scans. The MR imaging appearance of these gas collections in 17 disks was an area without signal, best seen on spin-echo sequences with short repetition time and echo time in the sagittal view. MR imaging precisely located the VP in the anulus fibrosus, the nucleus pulposus, and Schmorl nodes. In all but one case, degeneration of the disk was complete and associated with adjacent changes in vertebral bone. Pitfalls of MR imaging detection of VP included chemical shift artifact, calcifications, and tears without gas in the disk.

High-field MRI is capable of differentiating acute, subacute, and chronic hemorrhagic cortical infarctions. In eight of nine patients, hemorrhage occurred in a vascular watershed zone. Acute hemorrhagic cortical infarction produces mild cortical low intensity on T2-weighted images outlined by subcortical edema (high intensity) and isointensity with normal cortex on T1-weighted images. Subacute hemorrhagic cortical infarction shows cortical high intensity first on T1-weighted images and later on T2-weighted images; it is also associated with subcortical edema. In the chronic stage, there is a marked persistent cortical low intensity on T2-weighted images. This is most prominent in the deeply infolded cortical gyri. The low intensity noted in acute and chronic hemorrhagic cortical infarction with T2 weighting appears to be related to two separate underlying histochemical states. The characteristic cortical low intensity observed on T2-weighted images in acute and chronic hemorrhagic cortical infarction is proportional to the square of the magnetic field strength.

Nine lesions, four ocular (three melanomas, one hemangioma) and five orbital (two perioptic meningiomas, one hemangioma, one pseudotumor, one mucocele), were evaluated by magnetic resonance surface coil imaging at 1.5 T. Small ocular lesions with 3.9-4.5-mm-elevation were demonstrated. The use of two different pulse sequences resulted in separation of melanoma from adjacent retinal detachment. Contrast obtained between orbital lesions and the adjacent normal structures was better than that demonstrated with high-resolution computed tomography.

Delineation of the gastrointestinal tract in magnetic resonance imaging (MRI) remains a problem. Ferric ammonium citrate is paramagnetic, producing a high MRI signal intensity by virtue of its spin-lattice (T1) relaxation rate enhancement properties. Water is diamagnetic, producing a low MRI signal intensity, especially with short TR and TE times. To compare efficacy for gastrointestinal contrast alteration, ferric ammonium citrate was administered to 18 patients and water was given to 10 patients. Spin-echo imaging at 0.35T was performed after administration of these agents. Ferric ammonium citrate produced high signal intensity within the esophagus, stomach, duodenum, and small intestine that aided in the differentiation of the gastrointestinal tract from adjacent tumors, vessels, and viscera. Delineation of the gut wall was superior using ferric ammonium citrate compared to that produced by water. Delineation of the margins of the pancreas, liver, and kidney from adjacent gastrointestinal tract was also better with ferric ammonium citrate. Optimal distinction between bowel and fat was better with water. Longer TE times (75 to 200 ms) may allow improved contrast between gut and intrabdominal fat using ferric ammonium citrate.

Twenty intracranial hematomas between 1 day and over 1 year old were imaged using magnetic resonance at 1.5 T, with T1- and T2-weighted spin-echo pulse sequences. Characteristic intensity patterns were observed in the evolution of the hematomas, which could be staged as acute (less than 1 week old), subacute (greater than 1 week and less than 1 month old), or chronic (greater than 1 month old). Acute hematomas were characterized by central hypointensity on T2-weighted images (WIs). Subacute hematomas had peripheral hyperintensity on T1-WIs and then on T2-WIs. This hyperintensity proceeded to fill in the hematoma in the chronic stage. In subacute and chronic hematomas, there was hypointensity on T2-WIs in the immediately adjacent part of the brain. On T2-WIs of acute and subacute hematomas, the nearby white matter was characterized by hyperintensity, consistent with edema. A different mechanism is proposed for each of the three characteristic intensity patterns. Two of these mechanisms increase in proportion to the square of the magnetic field magnitude.

The effect of pancreatitis on magnetic resonance T1 and T2 relaxation times was evaluated in two different models of acute pancreatitis in the rat. Acute edematous pancreatitis was induced by repetitive intraperitoneal injections of the cholecystokinin-analogue caerulein; acute hemorrhage pancreatitis was induced by retrograde infusion of the bile salt sodium taurocholate into the pancreatic duct. T1 and T2 relaxation times were obtained in vitro from fresh pancreatic specimens at 37 degrees C with a 0.25 resistive spectrometer. In both edematous and hemorrhagic pancreatitis, significant prolongation of T1 and T2 was noted as early as 1.5 hours after the initiation of pancreatitis when compared with normal rat pancreas. Maximal prolongation occurred at 7 hours in the caerulein model with T1 of 966 +/- 46 msec (mean +/- SEM) (normal + 278 +/- 12 msec) and T2 of 75.9 +/- 2.9 msec (normal = 32.8 +/- 3.3 msec), and after 6 hours in the bile salt model with T1 of 798 +/- 40 msec and T2 of 92.5 +/- 3.3 msec. After the time point of maximal prolongation, T1 and T2 gradually decreased toward the normal values. The prolongation of T1 and T2 paralleled each other throughout the time course of pancreatitis in both models. The prolongation of both relaxation times correlated closely with pancreatic weight, water content, and amylase concentration in serum and ascites. The present determination of T1 and T2 relaxation times by in vitro spectrometry suggests that magnetic resonance imaging has the potential for detecting early pathologic changes in acute pancreatitis and thus may be helpful for an early clinical diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)

We report a case of multiple aneurysms with subarachnoid hemorrhage in which CT was inconclusive as to the source of bleeding and in which the angiographic criteria were misleading. Magnetic resonance demonstrated a focal subarachnoid hematoma adjacent to the ruptured aneurysm.

Gliomatosis cerebri is a rare condition characterized by diffuse overgrowth of large portions of the brain and spinal cord by glial cells in varying stages of differentiation. The tumor process is primarily an infiltrative, rather than a destructive one. Hence, pre-operative diagnosis by traditional imaging studies, including computed tomography (CT), has been difficult. Magnetic resonance imaging (MRI), with its unique sensitivity for cerebral pathology, is an ideal modality for demonstrating this lesion. We present three cases of gliomatosis cerebri in which high-field MRI clearly delineates the extent of the pathologic process.