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Biomedical subjects

R C Semelka

Publications and source records attributed to R C Semelka.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

Ampullary carcinoma: demonstration by current MR techniques.

The objective of this study was to demonstrate the appearance of ampullary carcinoma using current MR techniques, including fat suppression, gadolinium enhancement, and MR cholangiography. Nine patients with ampullary carcinoma were examined by MRI at 1.5 T. MR examinations included T1-weighted spoiled gradient echo, T1-weighted fat-suppressed, and immediate postgadolinium spoiled gradient echo images for all patients and MR cholangiography for three patients. The imaging features of ampullary carcinomas, including tumor size and morphology, signal intensity, and enhancement characteristics, were determined. Ampullary carcinomas shown on MR images ranged in size from 1.5 to 5.5 cm. Tumors were low in signal intensity on precontrast T1-weighted spoiled gradient echo and T1-weighted fat-suppressed images relative to normal pancreatic tissue and enhanced less than normal pancreas on immediate postgadolinium spoiled gradient echo images. Tumor conspicuity was greatest on immediate postgadolinium spoiled gradient echo images. MR cholangiography demonstrated high grade obstruction of the common bile duct and mild dilatation of the pancreatic duct at the level of the ampulla with abrupt termination of the ducts in two untreated patients and moderate dilatation of the common bile duct in one patient who had a biliary stent. Ampullary carcinomas can be demonstrated on MR images as small masses arising at the ampulla. Tumors are well defined on immediate postgadolinium spoiled gradient echo images.

Adenocarcinoma↗
PubMedDate not supplied

Renal cell cancer: incidence of hemorrhage on MR images in patients with chronic renal insufficiency.

This study describes the occurrence of hemorrhage in renal cancer in patients with chronic renal insufficiency as shown on MR images. Thirteen consecutive patients with chronic renal insufficiency who had histologically proven renal cancer and underwent MRI at 1.5 T were entered in the study. MR examinations included spoiled gradient echo (SGE) and T1-weighted fat-suppressed imaging pre- and postgadolinium administration. All renal cancers were well shown on MR images and were most clearly depicted on postgadolinium T1-weighted fat-suppressed images. Tumors in 12 of 13 patients had regions of high signal intensity on precontrast T1-weighted images. Histology demonstrated intratumoral hemorrhage in all 12 of these patients. Four hemorrhagic tumors were largely cystic on imaging studies. One of these cancers altered in appearance from largely cystic with extensive hemorrhage to largely solid with substantial enhancement after a 2.5-year interval. Renal cancers demonstrated minimal enhancement (11 patients) on early postgadolinium images and were minimally enhanced on delayed images in 10 of 13 tumors. Two renal cancers demonstrated intense enhancement. Renal cancers are well shown on MR images in patients with chronic renal insufficiency. Because of the common occurrence of hemorrhage into renal cancers in patients with renal insufficiency, caution should be exercised when evaluating hemorrhagic cystic lesions in these patients.

Adult↗
PubMedDate not supplied

Immediate postgadolinium spoiled gradient-echo MRI for evaluating the abdominal aorta in the setting of abdominal MR examination.

To assess the reproducibility and image quality of immediate postgadolinium chelate spoiled gradient-echo MRI in demonstrating disease of the abdominal aorta. All patients (27 patients: 21 men, 6 women) with substantial disease of the abdominal aorta, who underwent abdominal MR examinations at 1.5 T between 1991 and 1995, were entered in the study. Patients were referred for evaluation of suspected aortic disease (14 patients) or other abdominal diseases (13 patients). Three experienced investigators manually measured luminal and external aortic wall diameters and rated image quality, definition of inner and outer walls, extent of disease, and presence of other abdominal abnormalities, in an independent fashion. A cardiovascular surgeon then rated all studies to determine whether clinical management could be based on the MR findings alone. There was 98 to 99% agreement in measurements of luminal and external wall diameter between the three investigators. Overall image quality was rated as good in 77.8 to 88.9% of patients. A total of 31 additional nonaortic abdominal abnormalities were detected by all observers. The cardiovascular surgeon rated 25 of 27 studies as adequate to determine clinical management based on MR findings alone. Immediate postgadolinium spoiled gradient-echo MRI is a reproducible technique for the demonstration of abdominal aortic disease and possesses good image quality. Advantages of this technique include simultaneous evaluation of other nonvascular diseases of the abdomen, short examination time, and easy implementation as part of routine abdominal MRI scanning protocol.

Aged↗
PubMedDate not supplied

Liver lesion detection, characterization, and effect on patient management: comparison of single-phase spiral CT and current MR techniques.

This study compares liver lesion detection, characterization, and effect on patient management between single-phase spiral CT and MRI using spoiled gradient echo (SGE), T2-weighted fat-suppressed spin echo, and serial post gadolinium SGE. All patients with suspected liver lesions who underwent spiral CT and MRI within a 1-month period between January 1993 and September 1996 were included in the study. Spiral CT and MRI were interpreted prospectively in a blinded fashion by separate individual experienced investigators, and lesion detection and characterization were determined. Confirmation was obtained by surgery (6 patients), biopsy (18 patients), imaging follow-up (36 patients), or combined reading of all imaging studies and clinical follow-up (29 patients). Effect on patient management was determined by combined chart review and interview of the patients' physicians and by retrospective clinical assessment performed by a surgical oncologist and medical oncologist separately. Eighty-nine patients were included in the study. Regarding true positive lesion detection, 295 and 519 lesions were detected on spiral CT and MR images, respectively, which was significantly different on a patient-by-patient basis (P < .001). More lesions were detected on MR than on spiral CT in 44 of 89 patients (49.4%), and 11 of these 44 patients had lesions shown on MRI in whom no lesions were apparent on CT images. No patients had true positive lesions shown on spiral CT that were not shown on MRI. Regarding lesion characterization, 129 and 466 lesions were characterized on spiral CT and MRI images, respectively, which was significantly different on a patient-by-patient basis (P < .001). More lesions were characterized on MR than CT images in 67 patients (75.3%). Regarding effect on patient management, chart review with physician interview demonstrated that findings on MRI provided information that altered patient management as compared with findings on spiral CT in 57 patients. Retrospective clinical evaluation by the surgical and medical oncologist showed that MRI was considered to have a greater effect on patient management than spiral CT in 58 and 55 patients, respectively. Comparing current MRI technique to single-phase spiral CT, MRI detected more lesions in 49.4% and characterized more lesions in 75.3% of patients investigated for focal liver disease. MRI had a greater effect on patient management in each of the three methods than single-phase spiral CT in more than 61% of patients.

Adolescent↗
PubMedDate not supplied

Malignant hepatic tumors: changes on MRI after hepatic arterial chemoembolization--preliminary findings.

This study describes the MR appearances of malignant hypervascular liver lesions pre- and post-hepatic-arterial chemoembolization, with correlation to serial imaging and clinical responses. Eight patients with malignant hypervascular liver lesions underwent pretreatment and posttreatment MR examination on a 1.5-T MR imager. MR sequences included T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed spin echo or turbo spin echo, and dynamic gadolinium-enhanced SGE images. All patients underwent pretreatment, initial posttreatment, and subsequent posttreatment MR studies. The histology of primary tumors included various types of hepatocellular carcinoma (HCC) (four patients: fibrolamellar HCC [one patient], HCC [two patients], mixed HCC/cholangiocarcinoma [one patient]) and liver metastases (four patients: untyped islet cell tumor [two patients], gastrinoma [one patient], carcinoid [one patient]). Response to chemoembolization was determined by three assessments: MR response, serial imaging response, and clinical response. The appearance of MR response to chemoembolization was determined based on the correlation with clinical and serial imaging response. The MR response of lesions that showed good clinical response included: increase in signal intensity on T1-weighted images (three patients), decrease in signal intensity on T2-weighted images (three patients), and negligible or minimal enhancement on immediate postgadolinium images (four patients) after chemoembolization. The most marked change in lesion appearance was observed in lesions < or = 1 cm, which had intense homogeneous enhancement on pretreatment MR studies and negligible enhancement on initial posttreatment MR examinations. MR response of lesions that showed moderate clinical response demonstrated a variety of lesion appearances from substantial change to minimal change. MR response of lesions that showed poor clinical response demonstrated no change in lesion appearances compared with the pretreatment MR study. Our results demonstrated change in appearance of liver lesions between pre- and post-hepatic-arterial chemoembolization MR studies. MR response correlated with response determined by serial imaging studies and clinical findings.

Adolescent↗
PubMedDate not supplied

Sequential use of ferumoxide particles and gadolinium chelate for the evaluation of focal liver lesions on MRI.

This study describes the sequential use of ferumoxide (superparamagnetic iron oxide) particles and nonspecific extracellular gadolinium chelate (Gd) for evaluation of focal liver lesions on MRI to evaluate order of contrast administration and imaging effect of the first contrast agent on sequences acquired after the second contrast agent. Thirteen patients underwent MR examinations that included ferumoxide and Gd. The order and timing of administration were as follows: separate sessions (three patients; Gd study 4-19 days before ferumoxide study), same session, Gd first (seven patients; Gd study 1-2 hours before ferumoxide study), and same session, ferumoxide first (three patients; ferumoxide administered less than 1 hour before Gd study). Postcontrast sequences were reviewed in a randomized, blinded fashion by two separate investigators. Determination was made regarding whether (a) the presence of the first agent administered could be detected on sequences obtained after the second agent and (b) the presence of the first agent interfered with the image quality of those sequences. No evidence for the presence of Gd was appreciated by either observer on postferumoxide sequences acquired in separate session studies. In same session, Gd first studies, the presence of Gd was observed in six of seven patients on T1-weighted spoiled gradient-echo (SGE) images obtained after ferumoxide administration. The presence of Gd was not apparent in seven of seven patients on T2-weighted fat-suppressed images obtained after ferumoxide. In same session, ferumoxide first studies, the presence of ferumoxide was appreciated on post-Gd sequences in two of three patients. The presence of ferumoxide did not appreciably diminish image quality on those sequences. Exact agreement was achieved by the independent investigators. Our results suggest that Gd and ferumoxide can be administered sequentially within one study session without substantial loss of diagnostic information obtained on sequences performed after administration of the second contrast agent. Administrating Gd first resulted in less of an effect of the visualization of the first agent on sequences acquired after the second agent.

Adult↗
PubMedDate not supplied

MRI evaluation of acute renal trauma.

We describe the MR findings in a patient with acute renal injury after blunt abdominal trauma associated with perinephric hematoma and urinoma. Both CT and MR findings are described. Active urine extravasation into a perinephric urinoma is demonstrated by serial post-contrast imaging with CT and MRI showing progressively increased attenuation/signal intensity fluid in communication with the collecting system, commencing 2 minutes after contrast administration.

Abdominal Injuries↗
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Multiple pulmonary aneurysms secondary to Hughes-Stovin syndrome: demonstration by MR angiography.

We report a case of a 41-year-old patient with multiple pulmonary aneurysms secondary to Hughes-Stovin syndrome. Conventional pulmonary angiography could not be performed, because thrombus in both the inferior and superior vena cavae prevented catheter passage. Contrast-enhanced three-dimensional (3D) MR angiography (MRA) showed two segmental pulmonary aneurysms in the right lung. The affected segments of the lung were resected successfully, predicated on the MRA findings.

Adult↗
PubMedDate not supplied

Dynamic contrast-enhanced MR imaging of fibrolamellar hepatocellular carcinoma.

The magnetic resonance (MR) appearance of fibrolamellar hepatocellular carcinoma (FL-HCC) on T1- and T2-weighted and dynamic serial postgadolinium-DTPA images is reported. Both tumors were large (> 7 cm in shortest dimension) and had central regions of low signal intensity on T1- and T2-weighted images. Diffuse heterogeneous enhancement of the tumors occurred on immediate postcontrast images. Lesions became more homogeneous in enhancement over time, but lack of enhancement of central portions of the tumor persisted. Although persistent lack of enhancement of the tumor scar on late postcontrast MR images may be characteristic of FL-HCC compared with delayed enhancement in focal nodular hyperplasia, the potential similarities between these tumors is stressed.

Adolescent↗
PubMedDate not supplied

Transitional cell carcinoma of the upper urinary tract: staging by MRI.

BACKGROUND: This study evaluates the ability of MRI to stage transitional cell carcinoma of the upper urinary tract. METHODS: Nine patients who had transitional cell carcinoma of the upper urinary tract detected by other imaging modalities underwent MRI examination at 1.5 T. Imaging included pre- and postgadolinium-DTPA T1-weighted images (9 patients) pre- and postgadolinium chelate T1-weighted fat-suppressed spin echo (7 patients). Postcontrast images were acquired prior to the presence of gadolinium within the collecting system (< 2 min postcontrast), intermediate (2.5-8 min), and late (> 10 min) postcontrast. Images were prospectively interpreted and lesion staging was determined. Correlation with histopathology was obtained in all cases. RESULTS: Transitional cell cancers were demonstrated in 9/9 patients, and tumors ranged in size from 2 to 8 cm (mean = 3.8 cm) in one dimension. Correct tumor staging was performed in 8/9 patients. The staging error in one case occurred because direct tumor extension into the renal parenchyma was not detected. CONCLUSIONS: The results of this preliminary study show that MRI stages transitional cell cancers relatively well; however, MRI is not able to detect superficial invasion of renal parenchyma.

Aged↗
PubMedDate not supplied

Ciliated hepatic foregut cysts: US, CT, and contrast-enhanced MR imaging.

Hepatic foregut cysts are uncommon lesions of the liver. In this report we prospectively examined two patients by means of computed tomography (CT), ultrasound, and contrast-enhanced magnetic resonance imaging. Ciliated hepatic foregut cysts were subsequently demonstrated in both patients following CT-guided biopsy. Magnetic resonance imaging was found to be useful in differentiating these cysts from other lesions.

Aged↗
PubMedDate not supplied

Aneurysm of the inferior vena cava: case report.

Venous aneurysms are uncommon. Despite their infrequency, venous aneurysms can present with significant clinical complications such as thrombosis, pulmonary embolism, and death. In this report, we present the case of a thrombosed inferior vena cava aneurysm discovered in a 16-year-old male who had deep vein thrombosis of the right lower extremity. Thrombosis of the inferior vena cava is uncommon in the pediatric population. Therefore, congenital abnormalities such as an inferior vena cava aneurysm should be considered when evaluating pediatric patients who present with deep vein thrombosis.

Adolescent↗
PubMedDate not supplied

Correlation of perfusion abnormalities on CTAP and immediate postintravenous gadolinium-enhanced gradient echo MRI.

BACKGROUND: The purpose of this study was to evaluate patients with wedge-shaped perfusion defects seen on spiral CT arterial portography for the presence of transient increased wedge-shaped enhancement on dynamic gadolinium-enhanced gradient echo MR images. METHODS: Nineteen patients underwent CTAP and MRI within a 2-week interval. All patients with wedge-shaped perfusion defects on CT arterial portography were evaluated in a separate review session for the presence of transient increased segmental hepatic enhancement on dynamic gadolinium-enhanced spoiled gradient echo (SGE) MR images. RESULTS: Eight patients were identified to have subsegmental, segmental, or lobar wedge-shaped perfusion defects by CT arterial portography. In 8/8 patients, there was transient wedge-shaped increased hepatic enhancement on MR images which corresponded to the perfusion defects identified on CT arterial portography. Transient increased enhancement on MR images was observed on immediate postgadolinium images as high-signal intensity of the involved subsegment, segment, or lobe. This relatively high-signal area faded to near isointensity in all cases on images obtained at 45 s. CONCLUSION: Wedge-shaped perfusion defects demonstrated by CT arterial portography corresponded to wedge-shaped increased hepatic enhancement following gadolinium administration on SGE MR images.

Aged↗
PubMedDate not supplied

Renal abscesses: appearance on gadolinium-enhanced magnetic resonance images.

PURPOSE: To determine the appearance of renal abscesses on gadolinium-enhanced magnetic resonance (MR) images, we reviewed 12 MR studies of eight patients with renal abscesses. These findings were compared with findings on other imaging modalities. METHODS: Eight patients underwent 12 MR studies at 1.5 T, including T1-weighted gradient echo and fat-suppressed spin echo pre- and post-Gd-DTPA enhancement. Two radiologists retrospectively reviewed the MR images and compared MR findings to the findings on contrast-enhanced computed tomography (CECT) in five patients, noncontrast computed tomography (NCCT) in two patients, and ultrasound in all patients. RESULTS: On contrast-enhanced MR images, renal abscesses were clearly depicted as heterogeneously low-signal-intensity lesions. Four patients had solitary abscesses, and four had multiple abscesses. Prominent perinephric inflammatory stranding was observed in six patients and was best shown on gadolinium-enhanced T1 fat-suppressed images. CECT findings were comparable to contrast-enhanced MR images, although contrast resolution was less on CECT images in all cases. Renal abscesses were poorly shown on NCCT and ultrasound images. CONCLUSION: Renal abscesses are clearly shown on gadolinium-enhanced MR images as low-signal-intensity lesions associated with prominent perinephric inflammatory strands. In this study, NCCT and ultrasound studies are poor at defining abscesses. Despite lesser contrast resolution of CECT versus MRI, the findings in cases of renal abscesses are similar. In patients with elevated serum creatinine, iodine contrast allergy, or the need for serial exams, MRI may be the best imaging technique to evaluate renal abscesses.

Abscess↗
PubMedDate not supplied

Pelvic fistulas: appearances on MR images.

BACKGROUND: This multi-institutional study examines appearances of pelvic fistulas on magnetic resonance (MR) images. METHODS: MR images of 46 patients with documented fistulas from five teaching hospitals were retrospectively reviewed. All patients underwent T1-weighted (T1WI), T2-weighted (T2WI), and intravenous gadolinium chelate-enhanced T1-weighted (Gd-T1WI) images. Imaging sequences were separately and then collectively reviewed. The following determinations were made: fistula detection, fistula morphology and signal intensity, and the presence of associated abnormalities. Fistulas were classified into two categories: (1) fistulas that communicate with the bladder and (2) fistulas that do not communicate with the bladder. Fistulas within these two groups were subclassified further. The presence of fistulas was documented by surgery (five patients), endoscopy (six patients), fistulogram (20 patients), or physical exam (15 patients). RESULTS: Among the 46 patients, 53 fistulas were documented by means other than MR. Overall T1WI, T2W1 and Gd-T1WI images demonstrated 23, 31, and 39 of 53 fistulas, respectively. Gd-T1W1 detected significantly more fistulas than T1W1 (p < 0.05). Bladder fistulas were better shown on Gd-T1WI (8/15 fistulas) than on T1WI and T2WI (2/15 and 3/15) (p < 0. 05). Nonbladder fistulas were demonstrated by T1WI, T2WI, and Gd-T1WI images in 21, 28, and 31 of 38 fistulas, respectively. Among all fistulas, perianal fistulas (a subcategory of nonbladder fistula) had the highest detection by T1WI, T2WI, and Gd-T1WI in 19, 20 and 22 of 23 fistulas, respectively. On T1WI, 19 of 23 detected fistulas were low in signal intensity. On T2WI, 28 of 39 detected fistulas were high in signal intensity. On Gd-T1WI images, 29 of 40 fistulas were low in signal intensity, with enhanced tract wall. CONCLUSION: Bladder fistulas were best shown on Gd-T1WI, which was significantly greater than on T1WI or T2WI. Nonbladder fistulas were comparably shown by all techniques, with all performing modestly well. Perianal fistulas were shown equally well by all MR sequences and were the fistulas demonstrated with the highest sensitivity on MR images.

Adolescent↗