MR imaging of the dilated biliary tract

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.     

Pyogenic liver abscess: contrast-enhanced MR imaging in rats

MR imaging was used to evaluate experimentally induced pyogenic liver abscesses in an animal model. Rats were examined before and after IV administration of either gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA), ferrite particles, or both contrast agents together. Pyogenic liver abscesses appeared hypointense on T1-weighted images and hyperintense on T2-weighted images. Bolus administration of Gd-DTPA using a fast spin-echo sequence with repetition time of 250 msec and echo time of 20 msec (SE 250/20) showed transient selective enhancement of normal hepatic tissue and increased lesion conspicuity, quantitatively assessed by the contrast-to-noise ratio, which increased from -35.7 to -59.0. Delayed leakage of Gd-DTPA into the abscess center partially obscured small lesions at 30-60 min. Ferrite particles reduced the signal intensity of normal liver, and the abscess then appeared homogenously hyperintense. Applying the SE 500/32 sequence, the contrast-to-noise ratio increased from -1.2 to +74.0. Coordinated administration of both contrast agents showed a further increase in contrast to +94.0, with a hyperintense abscess rim surrounded by hypointense liver. Gd-DTPA increases abscess-liver contrast by rim enhancement of the abscess wall, and ferrite increases the abscess-liver contrast by selectively decreasing the signal intensity of surrounding normal liver. As a result of increased contrast-to-noise ratio, both contrast agents, alone or in combination, increase the conspicuity of hepatic abscesses.     

MRI of the spleen: normal appearance and findings in sickle-cell anemia

The MRI appearance and characteristics of the normal and diseased spleen were prospectively evaluated using spin-echo imaging with a superconducting magnet operating at 0.35 T. Sixty normal patients and 13 patients with sickle-cell anemia involving the spleen were studied. The normal spleen was isointense or slightly more intense than liver at a repetition time of 0.5 sec. At a longer repetition time (TR 2.0 sec), the normal spleen was usually more intense than liver, becoming markedly hyperintense compared to liver on relatively T2-weighted images (TR 2.0 sec, TE 56 msec). All patients with sickle-cell anemia showed abnormally diminished signal intensity of the spleen.     

Avascular necrosis of the femoral head: morphologic assessment by MR imaging, with CT correlation

To better understand the morphologic appearance of avascular necrosis (AVN) of the femoral head on magnetic resonance (MR) images (1.5 T) and computed tomographic (CT) scans, the records of 21 lesions were reviewed retrospectively. All MR imaging studies included T1-weighted images (T1WI) (repetition times [TR] of 400-1,000 msec, and echo times [TE] of 20-25 msec), and 15 included T2-weighted images (T2WI) (TR = 2,000-2,500 msec; TE = 60-80 msec). MR signal features of the lesions were compared with features on the corresponding CT scans. Abnormalities in the superoanterior aspect of the femoral head were noted on both image types in all 21 lesions but were more obvious on MR images in two. A characteristic margin of peripheral sclerosis seen on CT scans in 95% (20 of 21) of lesions corresponded to a line of low intensity on MR images. Fractures complicating AVN were seen in eight lesions at CT scanning. On T1WI, fractures were not clearly delineated. On T2WI, fractures were of high intensity but were depicted less clearly than on CT scans. Central signal intensity of the lesions on T1WI correlated with the presence or absence of fracture: 88% (seven of eight) of the lesions with fractures appeared less intense than fat, compared with only 8% (one of 13) of lesions without fractures (P less than .005). While MR imaging is a sensitive method for early diagnosis of AVN, CT scanning can more accurately identify fractures and is thus important for staging.     

A new diagnostic method of spondylodiscitis. Magnetic resonance imaging

Twenty four patients who were hospitalized for a suspicion of spondylodiscitis were prospectively evaluated with magnetic resonance imaging (MRI), radiology and radionuclide studies. Fifteen patients had an infectious spondylodiscitis, four had a vertebral degenerative disease, four had a rheumaticus spondylodiscitis, one had a chemical spondylodiscitis. The microbiological examinations and the clinical development bore the diagnosis out. Seven patients underwent Indium 111 scanning. The results of this scanning were correlated with MRI results. The MRI was performed with a 0.35 T whole body superconducting unit using spin echo technique. All patients were studied in the sagittal plane with two pulse sequences and more often with a surface-coil: TR 500 msec./TE 28 msec. and TR 2,000 msec./TE 60 msec. In all cases of true infectious spondylodiscitis the MRI results finding were characteristics. On the image obtained with the TR 500 msec./TE 28 msec., there was a confluent decreased signal intensity from the vertebral bodies and the intervertebral disk space. On the image obtained with TR 2,000 msec./TE 60 msec. there was an increased signal intensity from the vertebral bodies and the intervertebral disk space. The other spondylodiscitis have given a different MRI imaging, it was a confluent decreased signal intensity from the vertebral bodies and the intervertebral disk space on the twice pulse sequences. different images were obtained during the evolution of the infectious: first we observed a modification of the vertebral signal then the typical image that we described then a normal signal of the vertebral bodies with a pathological signal from the intervertebral disk space at last a degenerative intervertebral disk.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of severity of experimental pulmonary edema with magnetic resonance imaging. Effect of relaxation enhancement by Gd-DTPA

This study was done to demonstrate the capability of magnetic resonance imaging (MRI), using a spin-echo technique to detect permeability pulmonary edema in vivo, to correlate the signal intensity to the water content of the lung, and to assess the influence of administration of gadolinium-DTPA upon this relationship. Pulmonary edema was induced in 28 rats by intravenous injection of oleic acid (0.05-0.1 cc/kg). This was detected in all animals on images obtained with a repetition time (TR) of 2.0 seconds and echo times (TE) of 28 or 56 msec as increased signal intensity. Compared with control animals, the intensity was increased primarily in the dependent and peripheral portions of the lung. There was a significant linear relationship between the mean signal intensity, obtained from the area of both lungs within one slice, and the water content of both lungs (r = .94). Intravenous administration of gadolinium (Gd)-DTPA, 5 minutes prior to imaging, produced an easily observable increase in signal intensity on images of short TR (0.5 second) in the edematous lung tissue. However, these values did not exceed the intensities obtained without Gd-DTPA, if a long TR (2.0 seconds) was used for imaging. Thus, MRI has the capability for quantitating the severity of oleic acid-induced pulmonary edema. Gd-DTPA distributes rapidly into permeability pulmonary edema. It allows improved sensitivity at shorter pulse sequence repetition times and thus may diminish imaging time.     

Magnetic resonance imaging of retroperitoneal lymphadenopathy

A prospective study was performed to determine the value of magnetic resonance imaging (MRI) in the detection of retroperitoneal lymphadenopathy. Fifty patients with known malignancy, who demonstrated enlarged lymph nodes on computed tomography (CT), were entered into the study. The best visualization of retroperitoneal lymphadenopathy was found with a multislice spin-echo pulse sequence having a repetition time of 2000 msec, and echo delay of 30 msec. Nodes had a signal intensity lower than fat and greater than muscle with this pulse sequence. More than 90% of the lymphadenopathies as shown by CT could be demonstrated by MRI. Due to the flow-void phenomenon, blood vessels did not have any signal and were easily visualized without the use of intravenous contrast medium. Sagittal and coronal images added to an appreciation of the size of nodes and the extent of retroperitoneal lymphadenopathy. Ten normal volunteers were also imaged by MRI and their retroperitoneal nodes were well demonstrated.     

Cerebrospinal fluid-iophendylate contrast on gradient-echo MR images

The effect on the signal intensities of cerebrospinal fluid (CSF) and iophendylate (Pantopaque) and on CSF-iophendylate contrast was studied in vitro with a small-nutation-angle (alpha) gradient refocused magnetic resonance (MR) imaging technique (GRASS) as alpha, repetition time (TR), and echo time (TE) were varied. CSF signal intensity was consistently greater than that of iophendylate. Therefore, retained intraspinal iophendylate may be considered in the differential diagnosis of focal areas of low signal intensity at the periphery of the spinal canal on GRASS images. At constant TE and TR, an increase in alpha from 6 degrees to 45 degrees increased the signal intensities of CSF and iophendylate but decreased CSF-iophendylate contrast. At constant alpha and TR, an increase in TE from 13 to 28 msec decreased the signal intensities of CSF and iophendylate but increased contrast. At constant alpha and TE, an increase in TR from 50 to 400 msec increased the signal intensities of CSF and iophendylate, as well as contrast. Clinical examples of the contrast behavior of retained intraspinal iophendylate on both spin-echo and GRASS images corroborate the experimental findings. Retained intraspinal iophendylate may mimic the appearance of intra-or extra-dural lesions, magnetic susceptibility artifact, and flow on gradient-echo MR images of the spine.     

Magnetic resonance imaging of cavernous hemangioma of the liver: tissue-specific characterization

Twenty-one patients with hepatic hemangioma, five with hepatic cysts, and 25 with primary or metastatic cancer involving the liver were studied by magnetic resonance imaging (MRI). Benign lesions (hemangiomas, cysts) were diagnosed noninvasively by CT, radionuclide studies, and/or sonography and confirmed by follow-up examinations more than 1 year later. Malignant lesions were confirmed by liver biopsy in every case. Identical multisection/multiecho techniques were used in all patients to obtain T1-and T2-weighted spin-echo (SE) and inversion-recovery (IR) images. MRI detected more hemangiomas than any other imaging technique. Of 30 hemangiomas, 25 were spherical or ovoid with a homogeneous appearance and smooth, well defined margins. Cancer tended to have a heterogeneous appearance and poorly defined margins. On T2-weighted SE images obtained with 2000 msec TR and 60, 120, or 180 msec TE, hemangiomas had significantly greater contrast-to-noise ratios (C/N) than liver cancer (p less than 0.001). The SE 2000/120 sequence provided the single most useful image for distinguishing hemangiomas from cancers. When morphologic criteria are used in conjunction with measured C/N, MRI correctly distinguished cavernous hemangiomas from liver cancer with 90% sensitivity, 92% specificity, and an overall accuracy of 90%. Cysts had a low signal intensity on SE 500/30 images and could often be distinguished from hemangiomas and cancers that were nearly isointense relative to liver. IR images were sensitive for lesion detection but provided no tissue-specific information. The data indicate that T2-weighted SE imaging may become the procedure of choice for distinguishing cavernous hemangioma from liver cancer.     

Adnexal structures: MR imaging

Magnetic resonance (MR) images of the pelvis in 63 women (40 healthy and 23 with various adnexal diseases) were assessed retrospectively. When imaged with contiguous sections without gaps, adnexa were demonstrated bilaterally in 13 of the 15 healthy women of reproductive age, but in only seven of the 15 healthy postmenopausal women. Normal adnexa demonstrated low to medium signal intensity on images obtained with short repetition time (TR) (0.5 sec) and echo delay time (TE) (28 or 30 msec). Their signal intensity approached that of fat on images with a long TR (2.0 sec) and TE (56 or 60 msec). The adnexal origin of the pelvic masses was correctly identified in every case. Lesions containing fluid with little or no protein, fat, or blood content (simple fluid) had characteristically long T1 and T2 relaxation times and low signal intensity on images obtained with a short TR (0.5 sec) and TE (28 or 30 msec); they could be readily differentiated from all the other types of lesions.     

Inverted papilloma: evaluation with MR imaging.

The authors examined the magnetic resonance (MR) appearance of inverted papillomas to determine if this histologically benign lesion could be distinguished from malignancies of the sinonasal cavity. MR images in 10 patients with histologically proved inverted papilloma were retrospectively reviewed. The signal intensity of inverted papillomas on short repetition time (TR) images was iso- to slightly hypertintense to muscle in all 10 patients. Inverted papillomas had intermediate signal intensity on the long TR/echo time (TE) images. The tumors were iso- or slightly hypointense to fat on long TR/short TE images. In the seven patients who received gadopentetate dimeglumine, all inverted papillomas showed solid inhomogeneous enhancement. A review of eight sinonasal malignancies showed no distinctive signal intensity or enhancement characteristics to help differentiate inverted papillomas from various malignant tumors. The authors conclude that there is no signature MR appearance for the benign inverted papilloma. The main utility of MR imaging is in defining the extent of the lesion.     

Amebic liver abscess: MR imaging

Hepatic magnetic resonance (MR) imaging was performed in 12 patients with 13 amebic liver abscesses. While no specific image or intensity pattern was noted, most lesions were round or oval with smooth, well-defined margins; had decreased signal intensity compared with that of liver parenchyma on T1-weighted images and increased signal intensity on T2-weighted images; and had prominent, often multiple rims of variable signal intensity. Signal homogeneity within the abscess was present more often on T1- than on T2-weighted images. Diaphragmatic disruption was seen in two cases on coronal MR images. An amebic empyema was differentiable from sympathetic pleural effusions by its hyperintensity on both T1- and T2-weighted images. In patients who also underwent computed tomography (CT) or ultrasonography (US), no lesion was missed with any modality, and except for shape, no consistent features were found among images obtained with the different modalities. The data suggest that CT, US, and MR imaging are comparably effective in the detection of amebic abscess.     

MR imaging of brain abscesses

The MR images and CT scans of 14 patients with surgically verified pyogenic cerebral abscesses were reviewed. The MR findings correlated well with those seen on CT and were believed to be sufficiently characteristic to allow early and accurate diagnosis with MR alone. These features include (1) peripheral edema producing mild hypointensity on short TR/short TE and marked hyperintensity on long TR/intermediate to long TE scans; (2) central necrosis with abscess fluid hypointense relative to white matter and hyperintense relative to CSF on short TR/short TE scans and hyperintense relative to gray matter on long TR/intermediate to long TE scans (the fluid had concentric zones of varying intensity in seven cases, a finding not previously identified in other lesions); (3) extraparenchymal spread (intraventricular or subarachnoid), which was detected more easily on MR than on CT and was manifested by increased intensity relative to normal CSF on both short TR/short TE and long TR/intermediate TE scans; and (4) visualization of the abscess capsule, which was iso- to mildly hyperintense relative to brain on short TR/short TE scans and iso- to hypointense relative to white matter on long TR/intermediate to long TE scans. On the long TR scans, the relative hypointensity of the rim allowed for visualization of the typical morphologic features of the capsule, which in turn aided in differentiation of abscesses from other lesions (as it does on CT). To investigate the cause of the capsular intensity, pathologic studies of the capsules were reviewed when available (10 cases). Fibrosis was identified in all mature abscess capsules, but the combination of the intensities seen on short TR/short TE and long TR/intermediate to long TE scans as well as the temporal changes in intensity were believed to be incompatible with fibrosis as a cause of the capsular changes. Intensity patterns were suggestive of hemorrhage, but neither acute nor chronic hemorrhage was identified on routine H and E stains, while iron stain revealed scant hemorrhage in only two of the eight patients in whom these stains were used. We believe the capsular intensity (in particular the hypointense rims on long TR scans) may reflect paramagnetic T1, and to a greater extent T2, shortening, possibly due to the presence of heterogeneously distributed free radicals that are products of the respiratory burst produced by actively phagocytosing macrophages in the capsule wall. Distinctive MR features of pyogenic abscesses should afford early and accurate diagnosis.     

MR imaging of intracranial metastatic melanoma

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.     

Use of cerebrospinal fluid gating to improve T2-weighted images. Part I. The spinal cord

Ungated and gated magnetic resonance images of the spinal cord acquired with the use of long repetition times (TRs) and long echo-delay times (TEs) were compared in 21 studies performed on a 1.5-T system. Both normal and abnormal spinal cord conditions were compared. All images were acquired in an identical fashion except that ungated studies had TRs of 2,000 or 2,500 msec, whereas in gated studies, TR was determined by the patient's heart rate. The effective TR of images gated to the cerebrospinal fluid (CSF) fell primarily in the range of 1,500-1,800 msec. Gating was accomplished using a peripheral pulse. Three image parameters were assessed: signal-to-noise ratio, object contrast, and resolving power. For each parameter, in both normal and abnormal spinal cords, the CSF-gated studies proved superior by eliminating spatially mismapped signal intensity from pulsatile CSF.     

CT and MR imaging findings of xanthogranulomatous cholecystitis: correlation with pathologic findings

The aim of this study was to evaluate CT and MRI findings in xanthogranulomatous cholecystitis (XGC) and to correlate the imaging findings with various pathologic parameters. The study included 13 patients with histopathologically confirmed XGC. The CT (n=13) and MRI (n=5) obtained in these patients were evaluated retrospectively. On CT, low-attenuation areas in the wall of XGC correlated with foam and inflammatory cells or necrosis and/or abscess in XGC. Areas of iso- to slightly high signal intensity on T2-weighted images, showing slight enhancement at early phase and strong enhancement at last phase on dynamic study, corresponded with areas of abundant xanthogranulomas. Areas with very high signal intensity on T2-weighted images without enhancement corresponded with necrosis and/or abscesses. Luminal surface enhancement (LSE) of gallbladder wall represented preservation of the epithelial layer. The early-enhanced areas of the liver bed on dynamic CT and MR images corresponded with accumulation of inflammatory cells and abundant fibrosis. Our results indicate that CT and MRI findings correlate well with the histopathologic findings of XGC.     

Sequential MRI and CT monitoring in cryosurgery--an experimental study in rats

Cryosurgery is one of treatments of cancer, such as carcinomas of the face, oral cavity, prostate, breast, rectum and liver. But the method of cryosurgery seemed to be not yet completely established. The most important problem in this procedure is to define the extent of the cryolesion. But the trial with MRI and CT has not been reported. The purpose of this study is to investigate whether the image diagnosis such as Magnetic Resonance (MR) and CT is useful for the determination of the region during and after cryosurgery. The animal experiments were performed using 13 Wistar rats with inoculated Walker 256 cancer on both sides of femoral regions subcutaneously in the concentration of 1 million cells. After 7 days, cryosurgery was done by contacting for 15 sec with the absorbent cotton ball dipped in liquid nitrogen to the surface of right femoral tumor 3 to 6 times. The left side of tumor was intact. MRI was performed with a 0.1 Tesla ASAHI MR Mark-J and CT images were obtained using GE 9800. From the freezing to thawing, LF image (Low Flip Angle gradient echo image of Tr = 100 msec, Te = 18 msec, 60 degrees of flip angle) of MR and plain CT were taken every one minute. After thawing is over, SE image of Tr = 1500 msec, Te = 90 msec, IR images of Tr = 1200 msec, Td = 400 msec, and plain and contrast enhanced CT were carried out. Two and 7 days after cryosurgery, LF, SE and IR images of MR and CT with and without contrast medium were obtained with corresponding pathological examinations. The frozen cryolesion was of no signal intensity on the LF MR image and hypodensity on plain CT. Identification of cryolesion became possible during the cryosurgery. The cryolesion immediately after thawing showed higher intensity on the SE and LF images and hypodensity on enhanced CT. Therefore, the extent of cryosurgery can be diagnosed easily by these methods during and immediately after cryosurgery. In the follow-up studies after cryosurgery, the histological changes such as necrosis or tissue reaction were well represented by MRI and enhanced CT, but insufficiently by plain CT. From these experimental results, it may be concluded that MRI and CT are useful for monitoring the process of cryosurgery during and after the procedure.     

Urinary bladder MR imaging. Part I. Normal and benign conditions

The normal urinary bladder and several benign entities of the bladder were examined in 50 patients by magnetic resonance (MR) imaging. Specific features assessed included appearance of the bladder wall, optimal repetition (TR) and echo delay (TE) parameters for bladder-wall demonstration, and differentiation among various benign abnormalities, including bladder-wall hypertrophy, inflammation, and mucosal congestion, on MR images. The bladder wall in the 30 healthy subjects was best displayed using a TR = 2 sec, TE = 56 msec image, which gave 60% contrast between the bladder wall and urine and 48% contrast between the bladder wall and fat. Demonstration of bladder-wall hypertrophy required similar imaging; bladder distention was necessary to demonstrate the thickness of the bladder wall. Congestion and inflammation were best demonstrated on TR = 2 sec, TE = 56 msec images, which gave 45% contrast. Normal and/or hypertrophic bladder wall were distinguished from inflammation and congestion on the basis of signal intensity variations and/or T1 and T2 relaxation parameters.     

Primary malignant fibrous histiocytoma of the chest wall: CT and MR appearance

PURPOSE: The purpose of this work is to describe the CT and MR appearance of primary malignant fibrous histiocytoma (MFH) of the chest wall. METHOD: Eleven men and eight women (45-76 years old) with primary MFH of the chest wall who underwent both CT and MRI were enrolled, and the imaging interpretation was retrospectively compared to the pathologic specimen. RESULTS: All tumors were inhomogeneous in appearance on CT scans. All tumors showed high signal intensity on T2-weighted images. On T1-weighted MR images, tumors displayed inhomogeneous isosignal intensity in 15 cases (79%) and low signal intensity in 5 (21%) compared with the surrounding muscle. Tumors exhibited inhomogeneous enhancement in all except three localized tumors on enhanced CT and MRI. Invasion of intercostal muscle was noted on MR images in 18 patients (95%) and on CT in 11 patients (58%). CONCLUSION: There might be various radiologic appearances of MFH. However, CT and MRI are able to demonstrate the exact localization and disease extent of MFH arising in the chest wall.     

Central nervous system magnetic resonance imaging findings in neuro-Beh?et syndrome

In a patient with neuro-Beh?et (N-B) syndrome, MRI images obtained with TR 2000 msec, and TE 80 msec showed an increased signal intensity in the brain stem corresponding to the neurological symptoms. In N-B syndrome, the brain stem has been documented as a main site of the lesion, and MRI shows promise as a useful technique in the diagnosis of this disease.