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Biomedical subjects

R C Semelka

Publications and source records attributed to R C Semelka.

At least 91 records · Page 5Linked to original sources
PubMed1996

MRI of acute cholecystitis: comparison with the normal gallbladder and other entities.

Our purpose was to prospectively compare MRI findings with histopathologic findings in the evaluation of suspected acute cholecystitis. Fourteen patients with clinically suspected acute cholecystitis were entered into the study. MR sequences included T1-weighted fat-suppression and breath-hold spoiled gradient echo (SGE) before and after intravenous gadolinium chelate administration. Percent contrast enhancement (%CE) of the gallbladder wall and gallbladder wall thickness (WT) were measured and liver enhancement patterns determined prospectively on MR images. Correlation was obtained with pathological findings at cholecytectomy in all patients. In a second phase of the study MR images on 10 additional subjects who underwent MR examination for reasons other than hepatobiliary disease were analyzed to determine normal values for %CE and gallbladder wall thickness. Mean %CE was 124.0% in patients with acute cholecystitis (10 patients), 58.0% in patients with chronic cholecystitis (2 patients), and 73.0% in patients with gallbladder malignancy (2 patients). Mean gallbladder WT was 6.1 mm in acute cholecystitis, 4.5 mm in chronic cholecystitis, and 6.0 mm in malignant disease. There was a significant difference in %CE between acute and chronic cholecystitis (p = 0.03); no other significant differences in %CE or WT were observed among the patients with gallbladder disease. Patients without biliary disease had %CE of 37.3% and WT of 2.9 mm, which were both significantly less (p < 0.001) than in patients with acute cholecystitis. Transient enhancement of pericholecystic hepatic parenchyma on immediate postgadolinium SGE images was seen in 7 of 10 patients with acute cholecystitis, and not observed in other patients. Patients with acute cholecystitis had increased %CE and WT on MR images that were significantly greater than normal and %CE that was significantly greater than in patients with chronic cholecystitis. Transient increased pericholecystic hepatic enhancement was observed in 70% of acute cholecystitis patients and in no other patient groups.

Acute Disease↗
PubMed1996

Hepatic angiomyolipoma with minimal fat content: MR demonstration.

Hepatic angiomyolipoma is a rare entity. In this report, we describe the unusual MR findings of an angiomyolipoma with minimal fat content with histopathology correlation. This tumor had signal intensity features on various MR sequences including intense heterogeneous enhancement on immediate postgadolinium spoiled gradient echo images that resembled the appearance of a well-differentiated primary hepatocellular carcinoma. Angiomyolipoma with minimal fat content should be considered in the differential diagnosis of tumors with early diffuse heterogeneous enhancement on contrast enhanced images.

Adipose Tissue↗
PubMed1996

Dark ring sign: finding in patients with fungal liver lesions and transfusional hemosiderosis undergoing treatment with antifungal antibiotics.

OBJECTIVE: To describe the MR appearance of necrotizing fungal granulomas occurring in the liver of leukemic patients with hepatosplenic fungal disease and transfusional hemosiderosis on antifungal antibiotics. SUBJECTS AND METHODS: Four patients with acute myelogenous leukemia (n = 2) or acute lymphocytic leukemia (n = 2) who developed hepatosplenic fungal disease, and were treated with antifungal medication, underwent MRI examination on a 1.5 T MR imager. MR images were prospectively evaluated and correlated with liver biopsy (three patients), and clinical picture (one patient). RESULTS: Multiple liver lesions measuring approximately 1 cm in diameter were identified in all patients. Lesions possessed a distinctive MR appearance: central mild hyperintensity with a peripheral ring of very low signal intensity on precontrast T1- and T2-weighted images. The central region of the lesions enhanced following gadolinium administration with the peripheral ring remaining low in signal intensity. CONCLUSION: Necrotizing fungal granulomas in the liver of patients with transfusional hemosiderosis on treatment with antifungal antibiotics have a distinctive appearance of moderate high signal intensity center on T1- and T2-weighted and postgadolinium MR images with a peripheral rim of low signal intensity. This appearance reflects the presence of iron-laden macrophages in the periphery of granulomas and may be expected in processes that initiate an immune response involving aggregation of macrophages in the liver of patients with transfusional iron overload.

Acute Disease↗
PubMed1996

Preoperative evaluation of intersex patients with pelvic magnetic resonance imaging in search of Y chromosome-bearing gonadal tissue.

OBJECTIVE: To illustrate the utility of preoperative magnetic resonance imaging in the evaluation of intersex patients who require gonadectomy. DESIGN: Case reports of two phenotypic females having karyotypes containing a Y chromosome whose preoperative evaluation included pelvic magnetic resonance imaging. SETTING: Tertiary academic referral center. MAIN OUTCOME MEASURE: Pelvic magnetic resonance imaging for gonadal localization. RESULTS: Preoperative evaluation with magnetic resonance imaging correctly identified the most appropriate surgical approach to gonadectomy. CONCLUSIONS: Pelvic magnetic resonance imaging can be useful in the preoperative evaluation of intersex patients having nonpalpable Y chromosome-bearing gonadal tissue.

Adolescent↗
PubMed1996

Comparison of gadolinium chelates with manganese-DPDP for liver lesion detection and characterization: preliminary results.

Nonspecific extracellular gadolinium chelate (NEGd) was prospectively compared with managanese (Mn)-DPDP (Mn) for the detection and characterization of focal liver lesions of various histology. Seventeen patients with known or suspected focal liver lesions underwent NEGd and Mn-enhanced studies at 1.5 T. Study findings were correlated with histology (five patients), computed tomography (CT) examinations (17 patients), and 4- to 13-month imaging follow-up by CT and/or MR (five patients). NEGd studies were performed as serial postcontrast spoiled gradient echo (SGE) sequences, and Mn studies were performed as SGE sequences 15 and 30 min postocontrast and T1-weighted, fat-suppressed spin echo at 16 min. NEGd and Mn images were prospectively interpreted in a separate blinded fashion. Lesion detection and characterization were determined. NEGd and Mn-enhanced images demonstrated 61 and 49 lesions, respectively (p = .1, NS). A total of 60 and 33 lesions were characterized on NEGd and Mn images, respectively, which was significantly different (p = .008). No differences were observed for the detection and characterization of liver metastases; whereas there was a trend for superior detection and characterization for hepatocellular carcinoma with NEGA.

Adult↗
PubMed1996

MR findings of intestinal graft-versus-host disease.

Graft-versus-host disease (GVHD) occurs as a complication of allogenic bone marrow transplantation (BMT). The disease is characterized by skin rash, jaundice, mucosal inflammation, and diarrhea. In this report, we describe magnetic resonance (MR) findings of intestinal GVHD, which is correlated with endoscopic biopsy. MR findings demonstrated generalized increased bowel wall thickness associated with substantial bowel wall enhancement with gadolinium chelate.

Bone Marrow Transplantation↗
PubMed1996

MR imaging of the gallbladder.

Implementation of fast T1- and T2-weighted sequences on state-of-the-art magnetic resonance (MR) imagers increases the potential of MR imaging for examining the gallbladder and permits imaging of both cooperative and acutely ill patients with fewer artifacts. Comprehensive evaluation of gallbladder and biliary tract disease is feasible on new generation MR scanners using MR cholangiographic techniques in combination with tissue imaging sequences (spoiled gradient-echo and fat-suppressed spoiled gradient-echo) and dynamic intravenous gadolinium-chelate administration. Inflammatory and neoplastic diseases of the gallbladder are well shown with these techniques.

Artifacts↗
PubMed1996

Renal lymphoma: demonstration by MR imaging.

OBJECTIVE: The objective of this study was to demonstrate the spectrum of appearances of renal lymphoma using current MR techniques including gadolinium enhancement. MATERIALS AND METHODS: Twelve patients with renal lymphoma were examined by MR imaging on a 1.5-T scanner. MR examinations included T2-weighted, breath-hold T1-weighted spoiled gradient-echo, and T1-weighted fat-suppressed spin-echo imaging before and after gadolinium administration. Tumor morphology, signal intensity, and enhancement features were evaluated. RESULTS: Three types of renal involvement were observed: large paraaortic retroperitoneal masses with extension into the renal hilum, the subcapsular space, or both (nine patients); unilateral diffuse infiltration of the renal parenchyma (one patient); and focal rounded intraparenchymal masses (two patients). Untreated lymphoma (10 patients) was slightly hypointense relative to the renal cortex on T1-weighted images and was heterogenous and slightly hypointense or isointense on T2-weighted images. Enhancement of lymphomatous tissue was mildly heterogenous and was minimal on early images after gadolinium enhancement and remained minimal on late contrast-enhanced images in most tumor masses. No central necrosis of tumor was identified, and no renal vein thrombus was present. Five patients with lymphoma that presented as a large paraaortic mass showed diminished renal cortical perfusion of the involved kidney. All of these patients also had tumor extension into the renal hilum. CONCLUSION: Three types of renal involvement with lymphoma were observed. The most common appearance was a large retroperitoneal mass that invaded the kidney. Tumors had low to intermediate signal intensity on T1- and T2-weighted images and had diffuse heterogenous enhancement that was less than that of renal parenchyma.

Adult↗
PubMed1996

Contrast-enhanced MR imaging of the pancreas.

Recent MR techniques such as breath-hold imaging, fat suppression, and dynamic imaging after intravenous administration of gadolinium chelates have reduced artifacts in the abdomen, resulting in an increased role of MR imaging in the evaluation of pancreatic disease. The extracellular contrast agent gadolinium chelate has been shown to enhance normal pancreatic tissue in a homogeneous fashion. Contrast between normal pancreatic tissue and tumor tissue on T1-weighted images may be improved after administration of gadolinium. Because of the lesser vascularization of pancreatic ductal cancers as compared to the normal glandular tissue, the differences in signal intensity are often greatest in the capillary phase immediately after contrast administration. In addition, the hypervascular nature of islet cell tumors, results in good definition of primary tumor and liver metastases on immediate post-gadolinium images.

Contrast Media↗
PubMed1995

Pelvic magnetic resonance imaging in the evaluation of uterine torsion.

BACKGROUND: Uterine torsion is defined as the rotation of more than 45 degrees around the long axis of the uterus. An uncommon but potentially fatal event, uterine torsion is rarely diagnosed until the time of surgery. With magnetic resonance imaging (MRI), however, an accurate diagnosis of uterine torsion may now be made preoperatively. CASE: We describe a patient with uterine torsion in whom the correct diagnosis was made prenatally with the use of MRI, by the demonstration of an X-shaped configuration of the upper vagina. CONCLUSION: Distinctive features suggestive of uterine torsion were demonstrated by MRI and enabled an accurate preoperative diagnosis. To our knowledge, this is the first reported case of uterine torsion diagnosed on MRI.

Adult↗
PubMed1995

Anatomic changes in the pelvis after uncomplicated vaginal delivery: evaluation with serial MR imaging.

PURPOSE: To demonstrate the normal involution process of the post-partum pelvis with serial magnetic resonance (MR) imaging. MATERIALS AND METHODS: MR imaging was performed in 14 women after uncomplicated vaginal delivery. Six women underwent serial MR examinations at less than 30 hours and at 1 week, 2 weeks, 6 weeks, and 6 months after delivery; eight women were examined only within 30 hours of delivery. The dimensions and signal intensity of the uterus and cervix and the appearance of other pelvic structures were evaluated. RESULTS: The mean length of the uterine corpus was 13.8 cm within 30 hours of delivery and 5.0 cm at 6 months. The mean length of the cervix was 5.6 cm within 30 hours of delivery and 2.9 cm at 6 months. The junctional zone was not visible before 2 weeks; however, it was visible in all cases at 6 months. The outer cervical stroma had high signal intensity less than 30 hours after delivery and intermediate signal intensity thereafter. The inner cervical stroma was visible as a low-signal-intensity stripe on all images. CONCLUSION: Knowledge of the normal MR appearance of the involuting postpartum pelvis provides a baseline for interpretation of MR images obtained during this period.

Adult↗
PubMed1995

MR imaging of the gastrointestinal tract.

The use of T1-weighted sequences with reduced artifacts such as breath-hold gradient echo and fat-suppressed spin echo imaging has rendered MR imaging an effective technique for the evaluation of bowel disease. Various malignancies are depicted on MR images with diagnostic information comparable to CT images; concurrent evaluation for liver metastases are better performed by MR imaging. The high sensitivity for uptake of intravenous gadolinium suggests that MR imaging may play an important role in the evaluation of inflammatory bowel disease.

Digestive System↗
PubMed1995

Magnetic resonance imaging of the liver.

A variety of diffuse and focal disease processes affect the liver. MRI is likely the imaging modality of choice for investigation of patients suspected of having diffuse disease such as cirrhosis, hemochromatosis, or fatty infiltration. MRI is extremely effective at detecting and characterizing focal hepatic lesions. In particular, patients suspected of possessing hemangiomas, hepatocellular carcinoma, or hypervascular liver metastases are better evaluated by MRI than other imaging modalities. Immediate post gadolinium spoiled gradient echo and T2-weighted fat suppressed spin echo are very effective at lesion detection, whereas serial post gadolinium spoiled gradient echo is essential for lesion characterization. New fast T2-weighted sequences and tissue specific contrast agents may further increase the role of liver MRI by shortening exam time and increasing sensitivity and specificity, respectively.

Contrast Media↗
PubMed1995

Magnetic resonance imaging of the spleen and pancreas.

MRI of the spleen and pancreas requires specialized sequences which diminish artifacts in the upper abdomen. High temporal resolution sequences (e.g., spoiled gradient echo) acquired immediately after intravenous Gd-DTPA administration are necessary for imaging both the spleen and pancreas. In evaluating the spleen, early post Gd-DTPA images are essential as many focal disease processes (e.g., lymphomatous deposits or metastases) equilibrate rapidly (< 2 min) with splenic parenchyma. Complete pancreatic examination also requires the use of T1-weighted fat suppressed spin echo. T2-weighted images provide complementary information in a number of settings, in particular in the evaluation of islet cell tumors. Pancreatic ductal carcinoma is low signal on T1-weighted images and enhances in a diminished fashion on immediate post Gd-DTPA images. These tumors are well differentiated from focal chronic pancreatitis and islet celltumors based on their appearances on combined T1, T2-weighted and immediate post Gd-DTPA enhanced images.

Contrast Media↗
PubMed1995

Magnetic resonance imaging of the adrenal gland and kidney.

MR is able to detect and characterize the majority of disease entities which affect the adrenal glands and kidneys. In the evaluation of the adrenal glands in-phase and out-of-phase T1-weighted imaging may be the most effective noninvasive method to distinguish benign adenomas from malignant masses. T2-weighted images are sensitive and relatively specific for the investigation of pheochromocytoma. Although MRI is excellent at evaluating the kidneys, the lower cost and good image quality of CT render it the primary diagnostic tool for renal imaging. The major current applications for MRI of the kidneys include evaluation of patients with allergy to iodinated contrast, renal failure, and the characterization of complicated renal lesions. Evaluation of venous thrombus in the context of renal cancer is likely also a useful role for MRI.

Adrenal Gland Diseases↗
PubMed1995

Crohn's disease. Pilot study comparing MRI of the abdomen with clinical evaluation.

Fourteen patients underwent magnetic resonance imaging (MRI) examination (16 studies) and clinical evaluation concurrently. MRI studies included gadolinium enhancement and TI-weighted fat-suppressed spin echo. Separate investigators determined the severity of disease on MR images and on clinical evaluation in a blinded fashion. MRI studies were evaluated for percentage of mural contrast enhancement, wall thickness, and length of diseased bowel. An MR product was generated using these parameters. Clinical evaluation used the Crohn's Disease Activity Index (CDAI) and modified Index of the International Organization for the Study of Inflammatory Bowel Disease (IOIBD). Linear correlation was found between the MR product and clinical indexes of disease activity. The correlation between MR product and the modified IOIBD index was statistically significant (R(2) = 0.633, p = 0.0012). The correlation of MR product and CDAI was less close (R(2) = 0.274, p = 0.0373). Among individual MR parameters, length of diseased bowel showed the greatest correlation with CDAI (R(2) = 0.537, p = 0.012). Percentage contrast enhancement and bowel wall thickness showed significant correlation to the modified IOIBD index (R(2) = 0.739, p = 0.021) but not to the CDAI (R(2) = 0.004, p = 0.825). The results of this study show that the product of mural contrast enhancement, wall thickness, and length of diseased bowel correlated with clinical indexes of disease activity in Crohn's disease. Our findings suggest that MRI may be useful in evaluating the severity of Crohn's disease and may provide information complementary to clinical evaluation.

Adult↗