Biomedical subjects

R C Semelka

Publications and source records attributed to R C Semelka.

At least 145 records · Page 8Linked to original sources

PubMedDate not supplied

T2-weighted MR imaging of focal hepatic lesions: comparison of various RARE and fat-suppressed spin-echo sequences.

The authors prospectively compared four T2-weighted magnetic resonance (MR) sequences, including high-resolution 512 x 512 (matrix size) RARE (rapid acquisition with relaxation enhancement), 256 x 256 RARE, 128 x 256 breath-hold RARE, and 192 x 256 fat-suppressed spin-echo (T2FS) sequences, in the evaluation of 16 patients with focal hepatic masses. MR images were evaluated by quantitative lesion-liver signal difference-to-noise ratios (SDNRs) and subjective evaluation of image artifact and image quality. No significant differences were observed between RARE sequences in SDNR values. The T2FS sequence had a significantly higher SDNR than the 512 x 512 RARE sequence (24.6 +/- 15.0 vs 14.5 +/- 9.7) (P = .008). Image quality was rated highest for the 512 x 512 RARE and T2FS sequences (P = .006). The inherent advantage of high spatial resolution suggests that the 512 x 512 RARE sequence may be of value in detecting hepatic lesions.

Artifacts↗

PubMedDate not supplied

Evaluation of adrenal masses with gadolinium enhancement and fat-suppressed MR imaging.

A study was undertaken to determine the ability to characterize benign and malignant masses with unenhanced and contrast material-enhanced fast low-angle shot and fat-suppressed spin-echo magnetic resonance (MR) imaging. Thirty patients with adrenal masses detected at computed tomography (CT) underwent MR imaging within 14 days after CT. CT and MR images were interpreted in a prospective, blinded fashion. Sixteen patients had 20 benign adrenal masses, and 14 patients had 18 malignant masses. Quantitative measurements included percentage of contrast enhancement on immediate postcontrast dynamic images and periphery--center signal-to-noise ratio (S/N) on gadolinium-enhanced fat-suppressed images. Qualitative evaluation included determination of the regularity of lesion margins, homogeneity of signal intensity, and local extension. MR imaging depicted all adrenal masses discovered at CT examinations. Lesions ranged in diameter from 1 to 15 (mean, 4.4) cm. No significant difference was observed in percentage of contrast enhancement between benign (90.5% +/- 59.0 [standard deviation]) and malignant (110.5% +/- 116.4) masses. A difference was observed between periphery--center S/N for benign (-.05 +/- 1.5) and malignant (7.7 +/- 9.8) masses; overlap between the two, however, occurred. Qualitative evaluation allowed correct characterization of 32 of 38 masses, comparing favorably with CT, which allowed characterization of 30 lesions.

Adenoma↗

PubMedDate not supplied

Renal cancer staging: comparison of contrast-enhanced CT and gadolinium-enhanced fat-suppressed spin-echo and gradient-echo MR imaging.

Fifty-three consecutive patients with 61 solid or complex non-fat-containing renal masses compatible with renal cancer were examined with contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging with pre- and postcontrast FLASH (fast low-angle shot) and fat-suppressed spin-echo sequences. CT and MR imaging were performed within a 1-month interval. CT and MR images were prospectively interpreted. Tumor detection and staging were determined in all patients. CT and MR imaging enabled detection of 54 and 58 of 61 renal tumors, respectively. CT and MR imaging showed 34 and 35 of 38 histologically proved renal tumors, respectively, in 31 patients. Tumor size on CT and MR images demonstrated good correlation and correlated well with the size of pathologic specimens of 34 of 38 resected tumors detected with CT and MR imaging (r = .99). Of the 31 tumors in 31 patients who underwent surgical resection, 24 were correctly staged with CT and 29 with MR imaging. CT and MR imaging both enabled correct staging of four of five additional tumors with biopsy proof of tumor stage. A moderate difference in staging was observed between CT and MR imaging (P = .05). CT showed 13 and MR imaging 15 of 15 tumor thrombi. CT and MR imaging both showed 11 of 11 cases of adenopathy. The results suggest that MR imaging is moderately better than CT for the detection and staging of renal cancer.

Carcinoma, Renal Cell↗

PubMedDate not supplied

Malignant lesions of the liver identified on T1- but not T2-weighted MR images at 1.5 T.

The authors reviewed their 2 1/2-year experience with a magnetic resonance (MR) imaging protocol for a 1.5-T MR imager that included T2-weighted fat-suppressed spin-echo, T1-weighted breath-hold gradient-echo, and serial dynamic gadolinium-enhanced T1-weighted gradient-echo imaging to identify histologic types of malignant liver lesions more apparent on T1- than on T2-weighted images. MR images of 212 consecutive patients with malignant liver lesions were reviewed. T2-weighted, T1-weighted, and dynamic contrast-enhanced T1-weighted images were examined separately in a blinded fashion. Seven patients demonstrated liver lesions (lymphoma [two patients] and carcinoid, hepatocellular carcinoma, colon adenocarcinoma, transitional cell carcinoma, and melanoma [one patient each]) on T1-weighted images that were inconspicuous on T2-weighted images. In all cases, the lesions were most conspicuous on T1-weighted images obtained immediately after administration of contrast agent. Histologic confirmation was present for all seven patients. The consistent feature among these lesions was that they were hypovascular, due either to a fibrous stroma or to dense monoclonal cellularity. These results suggest that in some patients with hypovascular primary neoplasms, the lesions may be identified only on T1-weighted images, and that immediate postcontrast T1-weighted images are of particular value in demonstrating lesions.

Adult↗

PubMedDate not supplied

Solitary hepatic metastasis: comparison of dynamic contrast-enhanced CT and MR imaging with fat-suppressed T2-weighted, breath-hold T1-weighted FLASH, and dynamic gadolinium-enhanced FLASH sequences.

Twenty consecutive cancer patients with a solitary hepatic metastasis detected with dynamic contrast-material-enhanced computed tomography (CT) who were considered for hepatic resection underwent magnetic resonance (MR) imaging within 18 days after CT. Histologic confirmation was obtained in all lesions. CT depicted 20 solitary lesions. MR imaging showed a solitary lesion in 14 patients, two lesions in three patients, and more than two lesions in three patients, for a total of 37 lesions. Twenty-three lesions less than 2 cm in diameter were missed with CT, and six lesions less than 1.3 cm in diameter were missed with MR imaging. MR imaging was superior to CT in the detection of hepatic metastases on a patient-by-patient basis (P < .01). The results suggest that MR imaging is superior to dynamic contrast-enhanced CT for the detection of hepatic metastases.

Colorectal Neoplasms↗

PubMedDate not supplied

Nodular sarcoidosis of the liver and spleen: appearance on MR images.

Small nodular lesions in the liver and spleen have been reported as an infrequent manifestation of sarcoidosis. Five patients with this appearance on either dynamic contrast material-enhanced computed tomographic (CT) or ultrasound scans underwent magnetic resonance (MR) imaging with and without dynamic gadolinium enhancement. The lesions were relatively uniform in size, ranging from 0.5 to 1.5 cm. On CT scans, they were hypoattenuating relative to surrounding parenchyma. On MR images, the lesions were hypointense relative to background parenchyma with all sequences. No substantial enhancement was observed in the lesions, although lesion conspicuity decreased over time on serial postcontrast images. Lesion conspicuity was greatest on either T2-weighted fat-suppressed (T2FS) images or early-phase dynamic contrast-enhanced images. Abdominal adenopathy was seen in three of the five patients and was hyperintense relative to liver on T2FS images in two and intermediate in intensity in one patient.

Adult↗

PubMedDate not supplied

Comparison of breath-hold T1-weighted MR sequences for imaging of the liver.

Three rapid T1-weighted gradient-echo techniques for imaging of the liver were compared: fast low-angle shot (FLASH) and section-selective (SSTF) and non-section-selective (NSTF) inversion-recovery TurboFLASH. Ten healthy volunteers were imaged at 1.5 T, with breath-hold images acquired in the transaxial and coronal planes and non-breath-hold images in the transaxial plane. Breath-hold images were evaluated quantitatively and qualitatively, and non-breath-hold images were evaluated qualitatively. FLASH images had significantly higher (P < .001) spleen-liver signal difference-to-noise ratios (SD/Ns) than NSTF and SSTF images. Liver signal-to-noise ratios (S/Ns) were significantly higher (P < .001) on FLASH images than on NSTF and SSTF images. With breath hold, FLASH images were rated as having the highest quality in the axial plane, followed by NSTF and SSTF images. In the coronal plane, NSTF images were rated as having the highest quality. For images acquired during patient respiration, NSTF images had the highest quality and showed the least degradation. The results suggest that FLASH images have the highest SD/N and S/N for liver imaging and have the highest quality in the axial plane. In patients who cannot suspend respiration. NSTF images may be least affected by breathing artifact and provide reasonable image quality.

Adult↗

PubMedDate not supplied

Adrenocortical carcinoma: MR imaging appearance with current techniques.

The purpose of the study was to define the magnetic resonance (MR) imaging appearance of adrenocortical carcinoma (ACC) with current MR techniques. Eight patients with ACC underwent high-field-strength MR imaging with the following sequences: axial T1-weighted gradient echo, fat-suppressed T1-weighted spin echo, fat-suppressed T2-weighted spin echo, and gadolinium-enhanced T1-weighted gradient echo and fat-suppressed T1-weighted spin echo. Postcontrast images were also acquired in the sagittal (six patients) and coronal (three patients) planes. Out-of-phase gradient-echo images were obtained in two patients. Lesion morphology, signal intensity features, and presence of metastatic disease were retrospectively evaluated. MR imaging features of ACC included internal hemorrhage (seven of eight patients), central necrosis (seven of eight), and peripheral enhancing nodules (seven of eight). Out-of-phase images in two of two patients demonstrated signal loss compared with in-phase images, which may be a common feature of these tumors. Liver metastases were present in four patients. Consistent MR features of ACC are identified.

Adrenal Cortex Neoplasms↗

PubMedDate not supplied

Endometriosis: appearance and detection with conventional and contrast-enhanced fat-suppressed spin-echo techniques.

Suspected pelvic endometriosis was prospectively evaluated in 31 women with T1- and T2-weighted conventional spin-echo (CSE) magnetic resonance imaging alone and in combination with T1-weighted fat-suppressed (T1FS) and gadolinium-enhanced T1FS (Gd-T1FS) spin-echo techniques. Images were grouped for interpretation and comparison as follows: (a) CSE alone, (b) CSE/T1FS, and (c) CSE/T1FS/Gd-T1FS. All patients underwent surgery within 3 months of imaging, and 21 patients were found to have endometriosis: 59 endometriomas (26 large and 33 small) and 51 sites of implants were seen. With CSE images, 23 large and six small endometriomas were detected. With CSE/T1FS images, 25 large and 14 small endometriomas were identified. With CSE/T1FS/Gd-T1FS images, 24 large and 14 small endometriomas were detected and ill-defined areas of enhancement were noted in 22 sites throughout the pelvis. These corresponded to endometriotic implants seen at surgery in 14 sites. The sensitivity, specificity, and accuracy, respectively, for the detection of endometriosis were 76%, 60%, and 71% for CSE, 86%, 50%, and 74% for CSE/T1FS, and 81%, 50%, and 71% for CSE/T1FS/Gd-T1FS images. No significant differences (P > .1) between image combinations for correctly identifying patients with and without endometriosis were seen. The difference in sensitivity between CSE and CSE/T1FS and between CSE and CSE/T1FS/Gd-T1FS images for detecting small endometriomas was significant (P = .03).

Adipose Tissue↗

PubMedDate not supplied

Transient increased segmental hepatic enhancement distal to portal vein obstruction on dynamic gadolinium-enhanced gradient echo MR images.

The purpose of the present study was to demonstrate the frequency of occurrence of transient increased segmental hepatic enhancement distal to portal vein obstruction in patients with a lobar (main branch) portal vein obstruction. MR images of all patients with main and lobar branch portal vein obstruction examined by dynamic gadolinium enhanced gradient echo MR images between December 1990 and July 1994 were reviewed retrospectively. All studies included T2-weighted imaging, T1-weighted spoiled gradient echo 'fast low angle shot ([FLASH])', and postgadolinium enhanced FLASH imaging at 1, 45, and 90 sec and 10 min. Fourteen patients were identified with portal vein obstruction which included: six with main portal and right and left branch occlusion, six with right lobar, and two with left lobar. In the six patients with main portal vein obstruction, enhancement on 1-sec postgadolinium FLASH images was homogenous (three patients), diffusely heterogeneous (two patients), or peripherally hyperintense (one patient). In eight of eight patients with isolated obstruction of the right or left lobar portal vein, transient-increased segmental enhancement distal to portal vein occlusion was observed on immediate postcontrast images. Relatively high signal intensity of the involved segments was present on 1-sec images and liver parenchymal enhancement became more homogeneous by 45 to 90 sec in all cases. In conclusion, transient-increased segmental enhancement occurred in eight of eight patients with isolated right or left portal vein occlusion. We postulate that this effect occurs due to increased hepatic arterial blood flow in the presence of portal vein obstruction.

Adult↗

PubMedDate not supplied

Inflammatory pseudotumor of the liver: appearance on contrast enhanced helical CT and dynamic MR images.

The dynamic pre- and post-contrast MRI and helical CT imaging findings in a patient with inflammatory pseudotumor of the liver are described. On immediate post gadolinium spoiled gradient echo images multiple, ill defined, irregular, and intensely enhancing lesions were seen. Rapid washout of contrast was noted. Periportal involvement was also shown on T2-weighted fat suppressed images. Lesions showed greater conspicuity on MRI than CT. MRI findings in this rare entity led to performance of a diagnostic open surgical biopsy.

Adolescent↗

PubMedDate not supplied

Malignant liver lesions: comparison of spiral CT arterial portography and MR imaging for diagnostic accuracy, cost, and effect on patient management.

We compared two imaging techniques, spiral CT arterial portography (CTAP) and MR imaging, for diagnostic accuracy, procedural cost, and effect on management of 26 patients referred for hepatic surgery for suspected limited malignant liver disease. CTAP and MR imaging were done within a 1-week period (19 within 24 hours); the results of the studies were interpreted prospectively by separate reviewers. Surgical data were evaluated in conjunction with imaging data in 10 patients. Lesion detection and segmental involvement were determined and sensitivity and specificity were calculated. Procedural cost was determined from hospital billing codes. Effect on patient management was determined by the referring oncologic surgeon. CTAP and MR imaging showed 185 and 176 true-positive malignant lesions, 15 and zero false-positive malignant lesions, zero and 18 true-negative malignant lesions, and 13 and 22 false-negative malignant lesions, respectively. CTAP and MR imaging showed 107 and 105 true-positive segments, 11 and zero false-positive segments, 80 and 91 true-negative segments, and four and six false-negative segments, respectively. There was a significant difference in specificity of segmental involvement between MR imaging (1.0 +/- 0) compared with CTAP (0.88 +/- 0.05), P = .03. Total procedural cost was $3,499 for CTAP and $1,224 for MR imaging. CTAP findings did not change patient management over MR imaging findings in any patient, whereas MR imaging findings resulted in a change in patient management over CTAP findings in seven patients (P = .015). The results of our study suggest that MR imaging has higher diagnostic accuracy and greater effect on patient management than CTAP does and is 64% less expensive.

Adult↗

PubMedDate not supplied

MR findings in diffuse renal parenchymal disease.

This study evaluates the MR appearance of the kidney in diffuse renal parenchymal diseases, using precontrast, and immediate and delayed postgadolinium chelate (Gd), spoiled gradient echo (SGE), and pre- and post-Gd, T1-weighted, fat-suppressed spin-echo MR images to determine if characteristic findings exist for various types of renal disease. One hundred twenty-one patients with renal disease underwent MRI. Underlying diagnoses included: (a) glomerular disease (GD), (b) tubulointerstitial disease (TID), (c) microvascular disease (MVD), (d) ischemic nephropathy (INP), (e) obstructive nephropathy (ON), (f) infectious renal disease (IRD), (g) sickle cell disease (SCD), (h) renal cortical necrosis (CN), and (i) renal insufficiency of unknown etiology (UE). MR examinations of 22 patients with normal kidneys (NK) were evaluated as a control group. The presence of corticomedullary differentiation (CMD) demonstrated strong inverse correlation with serum creatinine concentration (SCr) (r = -.568, P < .001). Mean thickness of the renal cortex was 8.4 and 7.8 mm in patients with NK and Gd, respectively. The mean cortical thickness in patients with MVD, TID/Chemo, INP, and ON was 5.2, 5.6, 5.5, and 4.3 mm, respectively, significantly thinner than the renal cortex in the NK and GD groups (P < .01). Irregularity of the renal cortex was more frequent in MVD (60.9%), IRD (62.5%), ON (55.6%), and TID/other (53.8%) than in GD (3.8%) and NK (0%) (P < .01). Diffuse high SI of the entire medulla on delayed postcontrast images was observed in 25 (20.7%) of the patients with renal disease and none of the NK group. Although no pathognomonic features were found, certain findings were observed that may correlate with the etiology of the kidney disease and, therefore, assist in the differential diagnosis of renal parenchymal disease.

Adolescent↗

PubMedDate not supplied

Multilocular cystic nephroma: MR imaging appearance with current techniques, including gadolinium enhancement.

The purpose of the study was to define the MRI appearance of multilocular cystic nephroma (MLCN), using current MR techniques, including gadolinium (Gd)-enhanced sequences. Seven patients with MLCN underwent MR imaging with the following sequences: T1-weighted spin echo with fat suppression (T1FS, five patients), T1-weighted spoiled gradient echo (SGE, seven patients), T2-weighted fast spin echo (two patients), and Gd-enhanced T1FS (seven patients) and SGE (seven patients). MLCN was histologically proven by resection of the mass in six patients and by observation of typical imaging features with stability in appearance over a 6-month period in one patient. Lesion morphology and signal intensity (SI) features were retrospectively evaluated. MRI features of MLCN included a solitary cystic lesion with thin internal septations in six patients and a cluster of closely grouped cysts similar in size in one patient. Individual cystic spaces demonstrated SI, varying from low to high on T1-weighted images in three patients and demonstrated low-to-intermediate SI in four patients. Herniation of the lesions into the renal collecting system and thin enhancing septa were demonstrated in all patients. A complex cystic renal lesion with enhancing septa and herniation into the renal collecting system are the characteristic MR findings of MLCN. The direct multiplanar capability of MR may optimally show the relationship of MLCN to the renal pelvis and, thus, facilitate correct diagnosis.

Adult↗

PubMedDate not supplied

Malignant lesions of the liver with high signal intensity on T1-weighted MR images.

Our purpose was to identify the histologic types of malignant liver lesions with high signal intensity (SI) on T1-weighted images and to describe the MR imaging features. Thirteen patients with malignant liver lesions high in SI on T1-weighted images were studied with a 1.5-T MR imager using pre- and serial postcontrast spoiled gradient-echo (SGE) sequences (all patients), T2-weighted fat-suppressed spin-echo sequences (all patients), precontrast T1-weighted fat-suppressed spin-echo sequences (five studies in five patients), and precontrast out-of-phase SGE sequences (seven studies in six patients). Images were reviewed retrospectively to determine number of lesions; lesion size; SI of lesions on T1-weighted, T2-weighted, and fat-attenuated T1-weighted images; distribution of high SI in lesions on T1-weighted images; and tumor enhancement pattern. Seven patients had multiple tumors high in SI on T1-weighted images and six patients had solitary tumors. Seventy-two lesions were less than 1.5 cm in diameter and 35 lesions were more than 1.5 cm in diameter. Nine patients had solid malignant lesions and four patients had cystic malignant lesions. All tumors more than 1.5 cm in diameter were heterogeneously high in SI on T1-weighted images, and all tumors less than 1.5 cm were completely homogeneous or homogeneous with a small central hypointense focus. All tumors were more conspicuous on T1-weighted fat-attenuated images, both on excitation spoiled fat-suppressed spin-echo or on out-of-phase SGE images with the exception of one fat-containing hepatocellular carcinoma (HCC). In one patient with melanoma metastases and one patient with multiple myeloma nodules, appreciably more lesions were detected on out-of phase SGE images. Causes of hyperintensity were considered to be either fat, melanin central hemorrhage, or high protein content, all of which may be seen in a variety of tumors. Fat-attenuation techniques are helpful in the detection of these lesions.

Adenocarcinoma↗

PubMedDate not supplied

Pancreatic masses with inconclusive findings on spiral CT: is there a role for MRI?

This prospective study evaluates the ability of MRI using T1-weighted fat-suppressed spin-echo (T1FS) and dynamic gadolinium chelate (Gd) enhanced spoiled-gradient echo (SGE) to detect the presence of pancreatic tumor in patients in whom spiral CT findings are inconclusive. Sixteen consecutive patients who underwent spiral CT and had findings that were considered inconclusive for pancreatic tumor underwent MR within 2 weeks of CT. Spiral CT and MR images were interpreted in prospective fashion by separate individual investigators blinded to the results of the other imaging modality. CT was performed on a spiral CT scanner. MRI was performed on on a 1.5-T MR machine. Imaging sequences included T1FS pre-Gd and post-Gd and SGE pre-Gd and immediately post-Gd. Data were analyzed using receiver operating characteristic (ROC) analysis. Confirmation was obtained by pancreatic biopsy (n = 4), surgical resection (n = 1), and clinical imaging (n = 4) or clinical follow-up (n = 7). MRI was superior to spiral CT (P = .027) in this selected patient group at detecting or excluding pancreatic tumor by ROC analysis, with areas under the curve of .982 and .764, respectively, which was significant (P = .041). The greatest advantage of MRI was in patients in whom spiral CT demonstrated enlargement of the pancreatic head without clear definition of tumor, which was significant (P = .033). In 10 patients with this CT appearance, MRI demonstrated a high confidence for presence of tumor in four and a high confidence of absence in six. Association of imaging findings with patient diagnosis was significant for MRI (P = .001) but not significant for CT (P = .148). The results of our study suggest that MRI may add significant diagnostic information in patients in whom spiral CT is inconclusive for the presence of pancreatic tumor. The greatest advantage of MRI was in the evaluation of patients in whom spiral CT findings revealed an indeterminate enlarged pancreatic head.

Adolescent↗

PubMedDate not supplied

HASTE MR imaging: description of technique and preliminary results in the abdomen.

HASTE (Half fourier Single-shot Turbo spin-Echo) is a single-section T2-weighted sequence that acquires images in less than 1 second. Images are breathing independent and possess a variety of other features useful for imaging the abdomen. The design of this technique is described. Clinical studies of 38 consecutive patients were performed using this technique. HASTE images were considered good in 28 and fair in 10 patients, including five patients who could not suspend respiration. Definition of liver and bowel was particularly clear.

Abdomen↗

PubMedDate not supplied

Small bowel neoplastic disease: demonstration by MRI.

This study demonstrates the appearance of small bowel tumors on MR images. Sixteen patients with tumors involving small bowel were studied by MRI. All tumors were proven with histopathology. Eleven patients had primary tumors of the small bowel, which included the following: four carcinoid tumors, three adenocarcinomas, two lymphomas, one leiomyosarcoma, and one leiomyoma. Five patients had recurrent or metastatic disease to small bowel: two patients had colon cancer, one patient had pancreatic cancer, one patient had uterine leiomyosarcoma, and one patient had chloroma (leukemia). MR examination included breath-hold T1-weighted spoiled gradient echo (all patients), immediate postgadolinium-spoiled gradient echo (10 patients), and 2 to 4 minutes postgadolinium T1-weighted, fat-suppressed images (all patients). Tumor size, local extent, signal intensity, and enhancement features of tumor and adjacent tissue were determined. Tumor ranged in diameter from 1 to 9 cm (mean, 4.0 cm). Tumors had similar signal intensity to normal small bowel on precontrast images. Fourteen malignant tumors showed heterogeneous enhancement greater than adjacent bowel on gadolinium-enhanced images. Tumor local extent was best shown on precontrast-spoiled gradient-echo images and postgadolinium T1-weighted fat-suppressed images. Image quality was most consistent on breath-hold images. The results of this study show that small bowel tumors are demonstrable on MR images. Precontrast breath-hold T1-weighted spoiled gradient-echo images and gadolinium-enhanced fat suppressed images demonstrate tumor extent most reliably.

Adult↗