MR imaging findings in recurrent pyogenic cholangitis.
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Adult↗
Biomedical subjects
D G Mitchell
Publications and source records attributed to D G Mitchell.
Progressive viral-induced cirrhosis: serial MR imaging findings and clinical correlation.
PURPOSE: To determine which magnetic resonance (MR) imaging findings of cirrhosis change as disease severity progresses. MATERIALS AND METHODS: Seventy-six abdominal MR imaging studies in 38 patients (two per patient) with Child-Pugh grade A cirrhosis were retrospectively reviewed. All patients were followed up clinically and with MR imaging for 12 months or longer. MR images were used to determine volume indexes of the spleen and of each liver segment, as well as changes in hepatic contour, iron or fat deposition, and presence of varices and collateral vessels. RESULTS: During follow-up in patients with progressive cirrhosis (n = 13), the volume indexes of the anterior, posterior, and medial segments of the liver decreased significantly (P = .011, .013, .002, respectively), and the number of varices and collateral vessels increased significantly (P = .018). In patients with stable cirrhosis (n = 25), the volume indexes of the spleen, caudate lobe, and lateral segment increased significantly (P = .032, .018, .003, respectively). The atrophic index was significantly greater in progressive cirrhosis than in stable cirrhosis (P = .009). CONCLUSION: Progressive atrophy of the right hepatic lobe and the medial segment correlated with progression of clinical severity of cirrhosis, whereas increasing size of the caudate lobe and the lateral segment correlated with stability.
Adult↗
Hepatocellular carcinoma in North America: a multiinstitutional study of appearance on T1-weighted, T2-weighted, and serial gadolinium-enhanced gradient-echo images.
OBJECTIVE: The purpose of this study was to define the common appearances of hepatocellular carcinoma (HCC) in patients in North America by analyzing T1-weighted, T2-weighted, and serial gadolinium-enhanced gradient-echo images interpreted by radiologists at multiple institutions in North America. MATERIALS AND METHODS: One hundred thirteen consecutive patients with HCC from eight institutions were included in this retrospective case series. Inclusion criteria included MR imaging examinations performed on 1.5-T MR imagers using T1-weighted breath-hold spoiled gradient-echo images, T2-weighted images, and serial gadolinium-enhanced spoiled gradient-echo images. Diagnosis was established by histology in all patients. Images were analyzed retrospectively for lesion count, lesion diameter as less than or equal to 1.5 cm and greater than 1.5 cm, and signal intensity, by individual experienced radiologists at each institution. RESULTS: We found 354 HCC lesions in the 113 patients. Tumors were solitary in 63 patients, multifocal in 45 patients, and diffuse in five patients. Lesion appearance on combined T1-weighted, T2-weighted, and immediate gadolinium-enhanced spoiled gradient-echo images was as follows: 102 lesions (29%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited diffuse heterogeneous enhancement; 52 lesions (15%) were isointense on both T1- and T2-weighted images and exhibited diffuse homogeneous enhancement (all of these lesions measured < or = 1.5 cm in diameter); 50 lesions (14%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited diffuse homogeneous enhancement; 33 lesions (9%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited predominantly peripheral rim enhancement; and 27 lesions (8%) were hypointense on T1-weighted images, were isointense on T2-weighted images, and exhibited diffuse homogeneous enhancement. The remaining 90 lesions showed less common patterns. The appearance of HCCs greater than 1.5 cm and of HCCs less than or equal to 1.5 cm was significantly different (p = .001). The appearance of histologically proven HCCs is separately described. CONCLUSION: The combination of hypointensity on T1-weighted images, hyperintensity on T2-weighted images, and diffuse heterogeneous enhancement was the most common appearance of HCC on MR images in a multiinstitutional patient population in North America. Small HCCs measuring less than or equal to 1.5 cm were frequently isointense on both T1-weighted and T2-weighted images and may be detected on immediate gadolinium-enhanced images only as diffuse homogeneously enhancing lesions.
Adolescent↗
Contrast enhancement for the abdomen and pelvis.
A "quadraphasic" imaging technique is described for imaging malignancies of the abdomen (liver, kidneys and pancreas). With this technique images are acquired during four different phases relative to the administration of contrast agent: pre-contrast (baseline), during the capillary (arterial, pre-sinusoidal) phase, during the portal (sinusoidal) phase, and during the extracellular (delayed) phase. A brief summary of the kinds of malignancy that are best imaged during each of these phases is presented. Finally, comments are presented on the use of gadolinium-based contrast media for imaging tissues of the pelvis.
Abdomen↗
Focal hepatic lymphoma: magnetic resonance demonstration using current techniques including gadolinium enhancement.
This study demonstrates the appearance of focal hepatic lymphoma using current magnetic resonance techniques including gadolinium enhancement. Fifteen patients with hepatic lymphoma were imaged at 1.5T. T1-weighted, T2-weighted, immediate, and 5-10-min delayed T1-weighted spoiled gradient echo images were acquired in all patients. Determination was made of lesion size, number, morphology, and signal intensity of lesions on all sequences. Seven patients had solitary lesions and 8 patients had multiple lesions. Focal lesions of hepatic lymphoma ranged in size from 5 mm to 15 cm. They were well defined masses with mild to moderate low signal intensity relative to liver on T1-weighted images. Lymphoma lesions in 6 patients were moderately high in signal intensity on T2-weighted images compared with liver (Type I lesions), and enhancement of lesions was intense on early post-gadolinium images in 5 of these patients. Lymphoma lesions in 6 patients were mildly hypointense to mildly hyperintense on T2-weighted images compared to liver (Type II lesions), and lesions in 5 of these patients enhanced minimally on the early post-gadolinium spoiled gradient echo images. The remaining 3 patients had received chemotherapy before the magnetic resonance examination, and the imaging findings varied reflecting presumed differences in treatment responses. Transient ill defined perilesional enhancement on immediate post-gadolinium spoiled gradient echo images was observed in 9 patients including patients with either type of lesion. Focal lesions of hepatic lymphoma are usually low in signal intensity on T1-weighted images but have variable signal intensity on T2-weighted images. In general, lesions that are mildly hypointense to minimally hyperintense in signal intensity on T2-weighted images enhance minimally, and lesions moderately high in signal intensity of T2-weighted images enhance intensely. Transient increased perilesional enhancement is common.
Adult↗
Median nerve hamartoma: MR imaging using chemical shift techniques.
Magnetic resonance imaging findings of median nerve hamartoma are presented in three patients with palpable wrist masses and median neuropathy. Fat-suppressed T1-weighted images demonstrated adipose tissue separating the neural and fibrous tissue bundles in two of three patients, which results in the distinctive appearance of these tumors on magnetic resonance imaging. Fibrous tissue appeared as enhancing longitudinal bundles within the tumor on gadolinium enhanced fat-suppressed T1-weighted images.
Adult↗
Correction to a previously published case: recurrence of invasive adrenocortical tumor after excision of atypical adenoma.
A 74-year-old woman had hyperaldosteronemia and an adrenal adenoma that showed no evidence of lipid on in-phase and opposed-phase gradient-echo magnetic resonance (MR) images. MR images obtained 4 years after resection of the mass showed large masses of invasive tumor in the resection site, with small foci of lipid, and biopsy results confirmed the presence of an adrenocortical tumor.
Adrenal Cortex Neoplasms↗
Liver metastases: improved detection with dynamic gadolinium-enhanced MR imaging?
PURPOSE: To compare dynamic gadolinium-enhanced with unenhanced magnetic resonance (MR) imaging in detection of liver metastases. MATERIALS AND METHODS: Two groups of patients were prospectively examined with unenhanced and dynamic gadolinium-enhanced MR imaging. The first group (n = 48) had proved liver metastases; the second group (n = 49) did not. One set of unenhanced and one set of gadolinium-enhanced MR images were selected per patient. Three independent, blinded readers assessed the images for presence, number, location, and conspicuity of lesions. Data were analyzed with receiver operating characteristic curves, and contrast-to-noise ratios were calculated for the images. RESULTS: There was no statistically significant difference between the use of unenhanced and gadolinium-enhanced MR images in the differentiation of patients with from patients without metastases. The numbers of false-positive and false-negative diagnoses of individual lesions were higher (not statistically significant) with dynamic MR images than with unenhanced MR images. At dynamic MR imaging, contrast-to-noise ratio was highest in the early phase (30 seconds after injection of the contrast agent) but was not significantly different from the contrast-to noise ratio of the T2-weighted images. CONCLUSION: Dynamic gadolinium-enhanced MR imaging showed no improvement over unenhanced MR imaging in detectability of liver metastases.
Adult↗
Gallbladder disease: appearance of associated transient increased attenuation in the liver at biphasic, contrast-enhanced dynamic CT.
PURPOSE: To evaluate the frequency, location, and appearance of transient increased attenuation in the liver during arterial-phase helical or incremental computed tomography (CT) in patients with gallbladder disease without hepatic extension. MATERIALS AND METHODS: Findings in dynamic CT examinations in 31 patients with surgically proved gallbladder disease not extending into the liver and in 31 control patients without gallbladder disease were retrospectively reviewed and correlated with findings in other imaging examinations. RESULTS: Areas of transient increased hepatic attenuation (n = 27) were identified in 22 of 31 patients with gallbladder disease and in only one of 31 control patients. The difference in these findings was statistically significant (P < .001). In the 27 areas of transient increased hepatic attenuation, these findings were categorized as curvilinear or nodular attenuation adjacent to the gallbladder fossa in 13 (48%), segmental or subsegmental attenuation in segment IV and/or V in seven (26%), lobar attenuation in the left lobe (segments II-IV) in four (15%), and nodular attenuation seen as an early enhancing "pseudolesion" in segment IV in three (11%). Hepatic angiography performed in 10 of the 22 patients showed early depiction of the dilated cystic vein (n = 8) and direct communication with the portal branches (n = 2). CONCLUSION: Transient increased attenuation in the liver had a variable appearance at dynamic arterial-phase CT in most patients with gallbladder disease. This attenuation was most likely due to increased blood flow from the hepatobiliary system.
Adult↗
Hepatic lesions: discrimination of nonsolid, benign lesions from solid, malignant lesions with heavily T2-weighted fast spin-echo MR imaging.
PURPOSE: To determine whether the combined use of heavily and moderately T2-weighted fast spin-echo magnetic resonance (MR) images improves differentiation of non-solid, benign hepatic lesions from solid malignancies. MATERIALS AND METHODS: Three radiologists reviewed moderately (n = 133) and heavily (n = 133) T2-weighted and multiphasic dynamic contrast material-enhanced (n = 93) MR images in 133 patients with proved focal hepatic lesions (95 benign, 38 malignant). The radiologists used a five-point scale to rate their confidence in determination of malignancy. RESULTS: All three reviewers were statistically significantly better able to differentiate small (diameter less than 3 cm; n = 84) benignancies from small malignancies with the combination of moderately and heavily T2-weighted images (area under the receiver operating characteristic curve, 0.99 for each reader) than with moderately T2-weighted images alone (area, 0.88-0.90; P < .05). Confident diagnoses were rendered in 69 (82%) patients, with 100% accuracy for the combined use of moderately and heavily T2-weighted images. For larger lesions (diameter 3 cm or larger; n = 49), accurate differentiation was possible with moderately T2-weighted images alone. Additional use of multiphasic images did not improve the sensitivity, specificity, or accuracy of image interpretation. CONCLUSION: The combined use of moderately and heavily T2-weighted fast spin-echo MR images improves differentiation of small benign hepatic lesions from small malignant lesions.
Adult↗
Lipid in renal clear cell carcinoma: detection on opposed-phase gradient-echo MR images.
PURPOSE: To determine if comparison of in-phase and opposed-phase gradient-echo magnetic resonance (MR) images enables detection of lipid in renal clear cell carcinoma. MATERIALS AND METHODS: A retrospective search of MR and pathologic records identified 43 patients with biopsy-proved renal masses who underwent in-phase and opposed-phase MR imaging. Thirty-three patients had renal cell carcinoma (27 with clear cell carcinoma), and 10 patients had other renal tumors. With MR images, a region-of-interest measurement of signal intensity of the renal mass was divided by that of reference tissue. In each patient, a ratio of these region-of-interest measurements on the opposed-phase images to those on the in-phase images was calculated and termed the opposed-phase/in-phase signal intensity ratio (OIR). RESULTS: The mean OIR of clear cell carcinomas was significantly different from that of other renal masses (P < .0002); in 16 (59%) of 27 patients with clear cell carcinoma, the OIR was less than 2 standard deviations below the mean OIR of other masses. In cases of clear cell carcinoma, focal signal intensity on opposed-phase images was less than that on in-phase images. CONCLUSION: On opposed-phase images, some clear cell carcinomas show relative focal and diffuse loss of signal intensity. In renal masses, this signal intensity loss-which is consistent with lipid-does not necessarily indicate angiomyolipoma.
Adenocarcinoma, Clear Cell↗
Imaging of congenital abnormalities of the portal venous system.
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Adult↗
MR imaging of acquired abnormalities of the spleen.
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Adult↗
Compensated cirrhosis due to viral hepatitis: using MR imaging to predict clinical progression.
OBJECTIVE: The goal of our study was to determine the relative value of multiple MR features in predicting clinical progression of disease in patients with compensated cirrhosis. MATERIALS AND METHODS: The MR examinations of 23 patients with compensated cirrhosis (Child A) were retrospectively reviewed independently by two radiologists and correlated with clinical progression after follow-up of all patients for more than 12 months each (12-87 months: average, 39 months) by the same experienced hepatologist. Clinical progression was defined as an increase of the Child grade or the Pugh score by at least two points (5- to 15-point scale). In the initial MR study of each patient, the following MR findings were assessed by each radiologist independently: volume indexes of the spleen and each segment of the liver (based on three-axis measurements), nodular surface, regenerative nodules, ascites, iron or fat deposition, and varices or collaterals. RESULTS: The volume index of the spleen was the most accurate predictor of clinical progression (p = .001), the next most accurate was the number of sites of varices or collaterals (p = .002), and the third most accurate was the ratio of caudate lobe to right lobe volume index (p = .02). Other MR findings failed to correlate with clinical progression. CONCLUSION: As revealed on MR imaging, the volume index of the spleen, the severity of varices, and the volume index ratio of caudate lobe to right lobe can be used to help predict clinical progression of disease in patients with compensated cirrhosis.
Adult↗
Chondromalacia patellae: an in vitro study. Comparison of MR criteria with histologic and macroscopic findings.
OBJECTIVE: To develop MR criteria for grades of chondromalacia patellae and to assess the accuracy of these grades. DESIGN: Fat-suppressed T2-weighted double-echo, fat-suppressed T2-weighted fast spin echo, fat-suppressed T1-weighted, and gradient echo sequences were performed at 1.5 T for the evaluation of chondromalacia. A total of 1000 MR, 200 histologic, and 200 surface locations were graded for chondromalacia and statistically compared. RESULTS: Compared with gross inspection as well as with histology the most accurate sequences were fat-suppressed T2-weighted conventional spin echo and fat suppressed T2-weighted fast spin echo, although the T1-weighted and proton density images also correlated well. The most accurate MR criteria applied to the severe grades of chondromalacia, with less accurate results for lesser grades. CONCLUSIONS: This study demonstrates that fat-suppressed routine T2-weighted and fast spin echo T2-weighted sequences seem to be more accurate than proton density, T1-weighted, and gradient echo sequences in grading chondromalacia. Good histologic and macroscopic correlation was seen in more severe grades of chondromalacia, but problems remain for the early grades in all sequences studied.
Cadaver↗
Evaluation of the solid hepatic mass.
With the expanding use of abdominal imaging studies, evaluation of solid hepatic masses has become a common clinical challenge. In this review, the clinicopathologic characteristics of the most common causes of solid hepatic masses have been discussed. As the case scenarios demonstrate, the appropriate selection of imaging techniques and proper management of an individual patient depend on the clinical context. Often, complementary radiologic studies are necessary to narrow the differential diagnosis. Percutaneous biopsy or surgery is frequently required to confirm the diagnosis and to exclude malignancy definitively. The evaluation and management of solid hepatic masses is a cooperative venture that requires a multidisciplinary approach.
Adult↗
Breast MR imaging for cancer detection and implant evaluation: potential pitfalls.
Magnetic resonance (MR) imaging of the breast is currently used for evaluation of both parenchymal disease and silicone gel implants. MR imaging has the potential to address questions raised or unanswered with traditional diagnostic imaging methods. However, lesion specificity and cancer sensitivity depend on multiple technical factors (i.e., imaging parameters and contrast agent delivery) and biologic factors (i.e., the menstrual status of the patient and the vascularity of the lesion). Although diagnostic criteria for parenchymal disease have been reported, overlap of malignant and benign enhancement profiles occurs. The accuracy of implant evaluation depends on the imaging parameters and knowledge of the implant type and surgical history. In addition, individual investigative imaging methods are diverse, causing difficulty in protocol development for the practicing radiologist. An awareness of the problematic factors in breast MR imaging will improve diagnostic accuracy and allow understanding of the limitations of the modality and individual patient examinations.
Breast Implants↗
Fatty tissue on opposed-phase MR images: paradoxical suppression of signal intensity by paramagnetic contrast agents.
PURPOSE: To evaluate paradoxically decreased signal intensity on gadolinium-enhanced opposed-phase magnetic resonance (MR) images of fatty tissues. MATERIALS AND METHODS: Unenhanced and gadolinium-enhanced axial, opposed-phase, gradient-echo images were analyzed visually and with region-of-interest measurements. Tissues measured included adipose tissue (n = 10), angiomyolipomas (n = 8), and vertebral hemangiomas (n = 7). Additionally, a phantom of mayonnaise, soybean oil, agarose, and water (63% lipid signal) with variable concentrations of gadolinium chelate was imaged with similar technique. RESULTS: After administration of gadolinium chelate, signal intensity reduction averaged 18% for adipose tissue, 34% (72-48 units) for predominately fatty angiomyolipomas, and 39% (85-52 units) for vertebral hemangiomas. Imaging of the phantom showed a maximum of 79% reduction in signal intensity with gadolinium chelate (227-47 units). DISCUSSION: Gadolinium-enhanced opposed-phase images depict a significant loss in signal intensity in tissues with MR signal predominately from lipid. Gadolinium chelate increases the signal of water within fatty tissues, which increases the amount of lipid signal suppression due to destructive interference between water and lipid proton magnetizations.
Adipose Tissue↗