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Biomedical subjects

R C Semelka

Publications and source records attributed to R C Semelka.

At least 109 records · Page 6Linked to original sources
PubMed1994

Comparison of magnetic resonance imaging and endoscopy in distinguishing the type and severity of inflammatory bowel disease.

Twenty consecutive patients with first-time presentation of suspected inflammatory bowel disease underwent both endoscopy with biopsy and magnetic resonance imaging (MRI) within a 3-day period; the relative abilities of endoscopy and MRI to distinguish ulcerative colitis (UC) from Crohn's disease (CD) and to determine the severity of the disease process were compared. In 18 of 20 patients, a diagnosis of UC or CD could be made on histological specimens. MRI correctly diagnosed 17 of these 18 patients using T1-weighted fat-suppressed spin echo and gadolinium enhancement. Endoscopy correctly diagnosed 15 patients. Overall, MRI was not significantly better (p > 0.05) than endoscopy in distinguishing UC from CD. MRI correctly graded the severity of inflammatory changes in 13 of 20 patients, and endoscopy did so in 11 of 20. MRI and endoscopy findings were within one grade of histology findings in seven patients each. No significant difference (p > 0.05) was found between MRI and endoscopy in the ability to estimate the severity of the disease (as determined from biopsies). Bowel wall thickness measured on MR images demonstrated good correlation with percentage of contrast enhancement: r = 0.61; p = 0.003. In sum, magnetic resonance imaging was shown to be comparable with endoscopy in differentiating UC from CD and in gauging the severity of disease. Transmural assessment, sagittal imaging, and the lack of invasiveness were attractive features of MRI.

Adult↗
PubMed1994

Renal corticomedullary differentiation: observation in patients with differing serum creatinine levels.

PURPOSE: To evaluate renal corticomedullary differentiation (CMD) in patients with differing serum creatinine (sCr) levels. MATERIALS AND METHODS: Ten patients with normal sCr levels (0.9-1.3 mg/dL [80-115 mumol/L]), 14 with mildly elevated levels (1.5-2.9 mg/dL [133-256 mumol/L]), and 15 with elevated levels (> 3.0 mg/dL [265 mumol/L]) were examined with unenhanced T1-weighted fat-suppressed spin-echo (T1FS) and immediate gadolinium-enhanced gradient-echo (Gd-GRE) imaging. RESULTS: Patients with normal sCr levels had CMD on T1FS and Gd-GRE images. Among patients with mildly elevated levels, seven did and seven did not have CMD on T1FS images; all had CMD on Gd-GRE images. Patients with elevated levels had no CMD on T1FS images; 13 had CMD on Gd-GRE images. Two patients with levels above 10.0 mg/dL (884 mumol/L) had no CMD on Gd-GRE images. CONCLUSION: Independent of the cause of elevated sCr level, levels above 3.0 mg/dL result in loss of CMD on T1FS images, while levels above 10.0 mg/dL result in loss of CMD on Gd-GRE images.

Adolescent↗
PubMed1994

Adenomyosis: prospective comparison of MR imaging and transvaginal sonography.

PURPOSE: To prospectively compare conventional spin-echo magnetic resonance (MR) imaging and transvaginal sonography for the diagnosis of adenomyosis. MATERIALS AND METHODS: Twenty women with clinically suspected adenomyosis underwent MR imaging and transvaginal sonography performed within 3 months of each other. Pathologic proof was obtained in all cases. RESULTS: Seventeen patients were proved to have adenomyosis. The correct diagnosis was achieved with MR imaging in 15 of 17 cases. One false-positive and two false-negative diagnoses were made with MR imaging. With transvaginal sonography, nine of 17 cases of adenomyosis were correctly diagnosed. One false-positive and eight false-negative diagnoses occurred. The most frequent cause of false-negative diagnoses with transvaginal sonography was the misinterpretation of adenomyosis as leiomyomas (seven cases). CONCLUSION: MR imaging is significantly better (P < .02) than transvaginal sonography in the diagnosis of adenomyosis.

Adult↗
PubMed1994

Hypervascular malignant liver lesions: comparison of various MR imaging pulse sequences and dynamic CT.

PURPOSE: To compare the appearance of hypervascular liver lesions on gadolinium-enhanced fast low-angle shot (FLASH) imaging with T2-weighted fat-suppressed spin-echo imaging, dynamic nonequilibrium-phase FLASH imaging, and dynamic nonequilibrium-phase iodine-enhanced computed tomography (CT) and to characterize the appearance of lesions on serial postgadolinium FLASH images. MATERIALS AND METHODS: Twenty-nine patients with hypervascular malignant liver lesions were examined with dynamic contrast-enhanced CT and magnetic resonance (MR) imaging within a 1-month interval. MR sequences included T2-weighted fat-suppression, precontrast FLASH, and postgadolinium FLASH at 1 second (sinusoid phase), 45 seconds (nonequilibrium phase), and 10 minutes. RESULTS: More than five lesions were detected in 12 patients with CT, 15 patients with T2-weighted fat-suppression imaging, 16 with sinusoid-phase FLASH imaging, and 11 with nonequilibrium-phase FLASH imaging. In six patients, a statistically significant (P = .03) increase in the number of lesions detected, by category, was observed on sinusoid-phase FLASH images compared with CT images. CONCLUSION: Sinusoid-phase FLASH imaging is superior to nonequilibrium-phase imaging with MR or CT for the demonstration of hypervascular malignant lesions.

Adolescent↗
PubMed1994

Hepatic hemangiomas: a multi-institutional study of appearance on T2-weighted and serial gadolinium-enhanced gradient-echo MR images.

PURPOSE: To define the appearance of hepatic hemangiomas on T2-weighted and serial gadolinium-enhanced gradient-echo magnetic resonance (MR) images. MATERIALS AND METHODS: In four university hospitals, with 1.0- or 1.5-T MR imaging, T2-weighted and T1-weighted gradient-echo images were obtained in 66 adult patients before and at 1, 45, and 90 seconds and 10 minutes after injection of a gadolinium chelate. Hemangiomas were categorized as small (< 1.5-cm-diameter), medium (1.5-5.0-cm), and large (> 5.0-cm) tumors. RESULTS: In all, 154 hemangiomas were depicted (81 small, 56 medium, and 17 large tumors). All 154 lesions were hyperintense on T2-weighted images. Three patterns of contrast enhancement were observed: (a) uniform enhancement at 1 second (35 of 81 small lesions and no medium or large lesions), (b) peripheral nodular enhancement progressing centripetally to uniform enhancement (75 of all 154 lesions), and (c) peripheral nodular enhancement with persistent hypointensity centrally (44 of all 154 lesions, including 16 of 17 large lesions). CONCLUSION: Three patterns of enhancement of hemangiomas were observed. High signal intensity on T2-weighted images provided complementary information.

Adult↗
PubMed1994

Bladder tumor staging: comparison of contrast-enhanced CT, T1- and T2-weighted MR imaging, dynamic gadolinium-enhanced imaging, and late gadolinium-enhanced imaging.

PURPOSE: To evaluate the accuracy of contrast material-enhanced computed tomography (CT), unenhanced T1- and T2-weighted magnetic resonance (MR) imaging, and dynamic gadolinium-enhanced spoiled gradient-echo MR imaging in the staging of bladder cancer. MATERIALS AND METHODS: Thirty-six patients with histologically proved bladder cancer were prospectively examined with CT and MR imaging before tumor resection. Images were evaluated in a blinded fashion. RESULTS: All methods depicted tumors comparably well. Staging was correct in 16 of 29 patients (55%) with CT and 27 of 36 patients (75%) overall with MR imaging. Overstaging was the most common error, and both CT and MR imaging were more accurate for higher-staged tumors. CONCLUSION: CT and MR imaging perform well in the detection of tumors but are less accurate in staging. Dynamic gadolinium-enhanced MR imaging is better than other techniques, but the difference is not statistically significant.

Carcinoma, Transitional Cell↗
PubMed1994

Contrast-enhanced magnetic resonance imaging of the abdomen.

The use of intravenous gadolinium chelates in imaging of the abdomen is helpful in the detection and characterization of disease entities. It is well recognized that magnetic resonance (MR) imaging is more sensitive to the presence or absence of gadolinium chelates than computed tomography is to iodine. By exploiting this strength of gadolinium and MR sequences that reduce artifacts, the usefulness of abdominal MR examinations can be maximized. As a nonspecific extracellular contrast agent, the enhancement of gadolinium chelates reflect blood delivery (capillary phase imaging), capillary permeability (interstitial enhancement), and venous drainage (late interstitial/washout enhancement). In general terms, MR evaluation of abdominal organs is benefited by imaging in both capillary and interstitial phases of enhancement since these separate phases reflect different physiological aspects of disease processes. In this review, optimized investigation using intravenous gadolinium chelates is described for diseases of the kidney, gastrointestinal tract, liver, gallbladder, pancreas, spleen, and adrenal glands. The use of newer intravenous and oral contrast agents, particularly relating to the investigation of bowel and liver diseases, is also discussed.

Abdomen↗
PubMed1993

Liver lesion detection: comparison between excitation-spoiling fat suppression and regular spin-echo at 1.5T.

The role of excitation-spoiling fat suppression (fatsat) imaging in the detection of liver lesions was assessed comparing short TR/TE and lont TR/TE spin-echo (SE) sequences with and without excitation-spoiling fat suppression in 25 patients at 1.5T. The study included patients with liver metastases (n = 21), primary liver cancer (n = 3), and hepatic adenoma (n = 1). Liver lesion detection and lesion-liver signal-to-noise ratios (SNR) were determined for the various imaging sequences in a prospective fashion. Liver lesion-liver SNR were highest for long TR/TE (2000-2500/70-80) fatsat images (12.7 +/- 4.8) compared to long TR/TE regular SE (2000-2500/70-80) images (8.8 +/- 5.6) [(p = ns) (not significant)], short TR/TE (200-400/15-20) fatsat images (-6.2 +/- 4.8) (p = 0.05), and short TR/TE regular SE images (-4.9 +/- 3.2) (p < 0.01). Lesion detection was greatest for long TR/TE fatsat (86) followed by long TR/TE regular SE (78) (p = 0.05), short TR/TE fatsat (65) (p < 0.01), and short TR/TE regular SE (60) (p < 0.01). The results of this study suggest that excitation-spoiling fat suppression may improve liver lesion detection and conspicuity.

Adolescent↗
PubMed1993

Magnetic resonance imaging in inflammatory bowel disease.

Magnetic resonance (MR) images were acquired in 28 consecutive inflammatory bowel disease (IBD) patients undergoing medical treatment. The protocol employed included i.v. gadopentatate dimeglumine, pre- and post-contrast breath-hold Fast Low Angle Shot (FLASH), and fat-suppressed spin echo imaging. The percent contrast enhancement (% CE) of the fat-suppressed images was compared with severity of inflammation based on endoscopic and/or surgical findings. The %CE of the contrast-enhanced images was 169% +/- 63 in cases of severe inflammation (n = 16), 97% +/- 38 in moderate inflammation (n = 8), and 49% +/- 26 in mild inflammation (n = 4). Significant correlations were found between the clinicopathologic findings and (a) % CE, r = 0.74 (p = 0.0001); (b) length of affected bowel segment, r = 0.49 (p = 0.007); and (c) bowel wall thickness, r = 0.42 (p = 0.02). In a subsequent comparison, %CE was correlated with length of affected bowel and bowel wall thickness. The best correlation was bowel wall thickness, r = 0.53 (p < 0.004). Good correlation was found between MR findings and pathology/histology findings in the determination of bowel wall thickness, length of diseased bowel, and severity of inflammation in 10 patients who underwent bowel resection. The results of this study show that MR images demonstrate the extent and severity of inflammatory changes in the GI tract, which correlate with endoscopic and histological findings.

Adult↗
PubMed1993

MRI in the diagnosis of Crohn's disease in two pregnant women.

Two pregnant women considered symptomatic for inflammatory bowel disease were referred for magnetic resonance imaging (MRI) for assistance in establishing a diagnosis. Breath-hold gradient echo and contrast-enhanced T1-weighted fat-suppressed spin echo sequences were used. The MR appearance of the terminal ileum was consistent with Crohn's disease in both patients. The diagnosis of Crohn's disease was subsequently confirmed histologically. MRI is a safe, noninvasive modality that may be useful in confirming a suspected diagnosis of inflammatory bowel disease, especially in patients who cannot be evaluated with standard techniques.

Adult↗
PubMed1993

Magnetic resonance imaging evaluation of the local extent of colorectal mass lesions.

Magnetic resonance imaging (MRI) was conducted in 21 patients with known or suspected colorectal mass lesions. Imaging was carried out at 1.5 T using Fast Low Angle Shot (FLASH) and fat-suppressed (T1FS) gadolinium enhanced sequences. The lesions studied included adenocarcinoma (n = 16), lipoma (n = 2), villous adenoma with foci of adenocarcinoma (n = 1), malignant melanoma (n = 1), and rectal lymphoma (n = 1). Correlation was made with surgical findings in 14 patients, 10 of whom had tumors resected. Bowel wall involvement, tumor size, and extension demonstrated on MR images was correlated with histopathology findings. No significant differences were found (p > 0.05) among those parameters when compared to MR information from T1FS images. Lymph nodes were demonstrated on MR images but distinction between benign and malignant nodes could not be made.

Adenocarcinoma↗
PubMed1993

Islet cell tumors: comparison of dynamic contrast-enhanced CT and MR imaging with dynamic gadolinium enhancement and fat suppression.

Ten patients with 11 islet cell tumors underwent dynamic contrast material-enhanced computed tomography (CT) and magnetic resonance (MR) imaging within a 1-month period. MR imaging depicted all 11 tumors, and CT depicted seven of the 11 tumors. CT did not depict four of seven tumors that measured 2.5 cm in diameter or less. Islet cell tumors had low signal intensity on T1-weighted fat-suppressed MR images, and gastrinomas were best shown with this technique. Two of three insulinomas less than 1.5 cm in diameter were best shown on dynamic contrast-enhanced fast low-angle shot (FLASH) images as uniform areas of high signal intensity. Hepatic metastases were seen in five patients and showed peripheral ringlike enhancement best demonstrated on dynamic gadolinium-enhanced FLASH images. Hepatic lesions were most conspicuous on T2-weighted fat-suppressed spin-echo images. MR imaging with dynamic gadolinium enhancement and fat suppression is a promising tool in the investigation of islet cell tumors.

Adenoma, Islet Cell↗
PubMed1993

MR imaging of the pancreas.

Magnetic resonance (MR) imaging sequences that reduce image artifact in upper abdominal examinations herald a role for MR in the investigation of pancreatic disease. Sequences that have been successful in imaging the pancreas are T1-weighted breath-hold gradient-echo imaging, which avoids phase artifact caused by respiration, and T1-weighted fat-suppressed spin-echo imaging, which reduces breathing artifact, removes chemical shift artifact, and improves dynamic range of signal intensities. Breath-hold gradient-echo sequences provide useful diagnostic information when used prior to and immediately following bolus intravenous administration of gadopentetate dimeglumine. This review addresses current clinically important roles for MR imaging and emphasizes the detection of islet cell tumors, non-organ-deforming pancreatic ductal adenocarcinomas, and the distinction between chronic pancreatitis and cancer.

Humans↗
PubMed1992

Bile duct disease: prospective comparison of ERCP, CT, and fat suppression MRI.

The authors compared computed tomography (CT) and endoscopic retrograde cholangiopancreatography (ERCP), techniques commonly used to study the biliary tree, with pre- and post-Gd-DTPA breath-hold fast low angle shot (FLASH) and fat suppressed spin-echo in 28 consecutive patients with bile duct abnormalities detected on ERCP, including 11 patients with malignant disease and 17 patients with benign disease. ERCP, CT, and magnetic resonance (MR) images were prospectively interpreted in a blinded fashion and reviewed by consensus. ERCP characterized all cases of malignant disease by the presence of a narrowed bile duct lumen with irregular margins. CT and MRI detected all cases of malignant disease and characterized nine of 11 as malignant. In seven of these cases, CT and MRI showed thickening of extrahepatic bile duct walls greater than 5 mm. MRI images showed intrahepatic-enhancing periportal tissue in four cases, which was not seen on CT images, and which was biopsy-proven tumor extension. Benign disease was characterized on ERCP images by the demonstration of smooth tapered narrowings in 16 cases, whereas on CT and MR images it was characterized by mild to moderate dilatation of the intrahepatic bile ducts and wall thickness less than 5 mm in 13 cases. Overall ERCP correctly characterized 27 cases as benign or malignant and CT and MRI both characterized 25. The results of this study show a trend that ERCP is superior to CT and MRI for characterizing bile duct disease.

Adult↗
PubMed1992

Breath-hold T2-weighted sequences of the liver: a comparison of four techniques at 1.0 and 1.5 T.

T2-weighted images are considered the most sensitive for lesion detection at high field; however, long imaging time is problematic. Accordingly, the authors compared four breath-hold T2 or T2* weighted sequences comprising T2*-weighted FLASH, T2*-weighted PSIF, T2-weighted rapid spin echo (RASE), and T2-weighted Turbo-FLASH (Turbo) in 20 different healthy volunteers, 10 at 1.0 T and 10 at 1.5 T with reference to regular T2-weighted spin echo. Images were evaluated quantitatively by liver signal to noise (S/N) and spleen-liver signal difference to noise (SD/N) ratios and qualitatively for presence of artifacts and image quality. Data were evaluated for 1.0 T and 1.5 T separately and combined. In the combined evaluation, T2*-FLASH had good S/N (23.1 + 5.1) but low SD/N (2.9 + 1.7) and suffered from susceptibility artifacts. T2* PSIF had good S/N (28.1 + 10.0) and moderate SD/N (6.0 + 2.4), but occasionally had heterogeneous signal intensity. Flow signal void was an attractive feature. T2 RASE had very low S/N (4.4 + 1.9) and low SD/N (2.3 + 1.1) and suffered from flow artifacts. T2-Turbo had good S/N (24.6 + 8.6) and SD/N (8.9 + 2.5). Flow signal void was present, but small matrix size decreased image quality. The results of our study suggest that T2*-PSIF and T2-Turbo have good S/N and SD/N and fair image quality which may be clinically useful for breath-hold T2-weighted sequences of the liver.

Adult↗
PubMed1992

Renal lesions: controlled comparison between CT and 1.5-T MR imaging with nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold FLASH techniques.

Nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold fast low-angle shot (FLASH) magnetic resonance (MR) imaging techniques were compared with iodine contrast material-enhanced computed tomography (CT) for the detection and characterization of renal masses. MR studies included T1-weighted fat-suppressed spin-echo (T1FS) and FLASH images followed by rapid injection of gadopentetate dimeglumine and a repeated FLASH image obtained at 1 second, a T1FS image at 30 seconds, and a FLASH image at 10 minutes. Of 38 patients, 17 had renal cysts, 18 had solid tumors, two had cortical scarring, and one had a hypertrophied column of Bertin. With contrast-enhanced T1FS, contrast-enhanced FLASH, and CT images, 114, 110, and 109 lesions, respectively, were detected. With MR imaging and CT, cysts smaller than 5 mm in diameter and solid tumors as small as 1 cm in diameter were detected. With combined contrast-enhanced FLASH and T1FS images, 112 lesions were correctly characterized as cystic or solid; with nonenhanced T1FS images, 110; with nonenhanced FLASH images, 107; and with nonenhanced CT, 103.

Contrast Media↗
PubMed1992

Focal liver disease: comparison of dynamic contrast-enhanced CT and T2-weighted fat-suppressed, FLASH, and dynamic gadolinium-enhanced MR imaging at 1.5 T.

Dynamic contrast medium-enhanced computed tomography (CT), T2-weighted fat-suppressed spin-echo (T2FS) magnetic resonance (MR) imaging, and breath-hold T1-weighted fast low-angle shot (FLASH) MR imaging before and after dynamic gadopentetate dimeglumine injection were compared in 73 patients with clinically suspected liver disease. Observer confidence for presence of focal lesions was determined by using receiver operating characteristic analysis. For all MR images, hepatic lesion-liver signal-to-noise ratios were evaluated qualitatively. and resolution and presence of artifacts were evaluated qualitatively. Lesion detection was greatest with T2FS (n = 272) and enhanced FLASH (n = 244) and was statistically greater with both of these than with CT (n = 220) and FLASH (n = 219) (P less than .03). Correct lesion characterization was greatest with enhanced FLASH (n = 236) (P less than .01), followed by CT (n = 199), FLASH (n = 164), and T2FS (n = 144). Enhanced FLASH was particularly successful in characterization of 5-mm- to 1.5-cm-diameter lesions as cystic or solid.

Adenoma↗