Biomedical subjects

R C Semelka

Publications and source records attributed to R C Semelka.

At least 127 records · Page 7Linked to original sources

PubMed1992

Spleen: dynamic enhancement patterns on gradient-echo MR images enhanced with gadopentetate dimeglumine.

To examine the pattern of immediate enhancement with gadopentetate dimeglumine on dynamic magnetic resonance (MR) images of the spleen, this study was divided into two parts: In the first part, the authors retrospectively reviewed the dynamic MR images obtained with a fast low-angle shot (FLASH) sequence in the abdomen immediately after injection of gadopentetate dimeglumine in 137 patients. In the second part, dynamic gadolinium-enhanced FLASH images were prospectively compared with contrast material-enhanced computed tomographic (CT) scans in 17 patients with focal splenic lesions discovered on CT scans. In the first part, 108 patients (79%) had an arciform pattern of contrast enhancement; 22 patients (16%), a uniform pattern of high signal intensity; and seven patients (5%), a uniform pattern of low signal intensity. Most patients had arciform enhancement of the spleen; uniform enhancement occurred in some patients with underlying malignant or inflammatory disease. In the second part, all focal lesions seen on CT scans were seen on dynamic MR images (75 lesions), significantly more than were seen on FLASH images (15 lesions) (P < .001).

Adolescent↗

PubMed1991

Combined gadolinium-enhanced and fat-saturation MR imaging of renal masses.

Combined gadopentetate dimeglumine enhancement and fat-saturation (FS) spin-echo (SE) magnetic resonance (MR) imaging for the detection and characterization of renal masses was evaluated in 43 patients with a total of 71 lesions (28 solid masses and 43 cysts). SE MR sequences compared were the following: short repetition time (TR)/echo time (TE), conventional SE, short TR/TE FS SE, long TR/TE conventional SE, gadolinium-enhanced short TR/TE conventional SE, and gadolinium-enhanced short TR/TE FS SE techniques. MR findings were compared with findings of contrast-enhanced computed tomography (CT) and with pathologic findings in all patients. The sensitivities for detection of renal masses with gadolinium-enhanced FS (71 of 71 lesions) and with gadolinium-enhanced short TR/TE conventional (65 of 71 lesions) SE sequences were significantly (P less than .01) greater than with any unenhanced (short TR/TE conventional [40 of 71 lesions], or long TR/TE [39 of 71 lesions]) SE sequence. Lesion characterization was also best with the gadolinium-enhanced FS SE sequence (65 of 71 lesions correctly classified). When combined pre- and postcontrast short TR/TE FS SE images were analyzed with both qualitative (visual) and quantitative (region-of-interest measurements) assessment, lesion characterization improved even further (70 of 71 lesions were correctly characterized). All lesions detected with CT were visualized with the gadolinium-enhanced FS SE MR sequence, which in addition depicted seven cysts and two small renal cell carcinomas. In summary, the use of gadopentetate dimeglumine, especially when combined with the FS technique, was superior to unenhanced MR imaging for detection and characterization of renal lesions.

Carcinoma, Renal Cell↗

PubMed1991

Normal and diffusely abnormal myocardium in humans: functional and metabolic characterization with P-31 MR spectroscopy and cine MR imaging.

The current study tested the concept that cine magnetic resonance (MR) imaging and phosphorus-31 MR spectroscopy might be used to provide a comprehensive evaluation of the functional and metabolic status of the myocardium in humans. Thirteen patients with congestive cardiomyopathy and eight healthy volunteers were imaged at 1.5 T with the one-dimensional chemical shift imaging technique for localization of P-31 MR spectroscopy and an electrocardiographically referenced gradient refocused sequence for imaging of the heart. Prominent peaks in the PDE and PME regions were observed in cardiomyopathic patients, but only the former peak was measured. The PCr/beta-ATP peak ratio was not significantly lower in cardiomyopathic patients compared with healthy subjects (1.51 +/- 0.08 vs 1.54 +/- 0.04). The ratios of PDE/PCr (0.80 +/- 0.07 vs 0.54 +/- 0.10) (P less than or equal to .01) and PDE/beta-ATP (1.19 +/- 0.10 vs 0.84 +/- 0.08) (P less than or equal to .05) were significantly higher in patients with dilated cardiomyopathy compared with healthy volunteers. Left ventricular systolic wall thickening was significantly lower and left ventricular peak and end-systolic wall stress and mass were significantly higher in cardiomyopathic patients compared with healthy volunteers. Thus, localized, gated P-31 MR spectroscopy combined with cine MR imaging allowed identification of both abnormal myocardial phosphate metabolism and abnormal ventricular function. While this study suggests that increased myocardial PDEs may be a marker for abnormal myocardium, the sensitivity and specificity of this marker need to be further evaluated.

Adenosine Triphosphate↗

PubMed1991

T1-weighted sequences for MR imaging of the liver: comparison of three techniques for single-breath, whole-volume acquisition at 1.0 and 1.5 T.

The authors compared three T1-weighted magnetic resonance imaging techniques that acquire images encompassing the entire liver in one breath hold. Twenty healthy volunteers were imaged--10 at 1.0 T and 10 at 1.5 T--and the results compared with those of regular short repetition time/echo time spin-echo imaging. Rapid acquisition spin echo was resistant to artifacts and had good image quality but had the lowest liver signal-to-noise (S/N) and spleen-liver signal-difference-to-noise (SD/N) values. Fast low-angle shot (FLASH) had the highest S/N and SD/N, very good image quality, and only mild artifacts. TurboFLASH had good S/N and SD/N, but reduced matrix size decreased image quality. All three sequences had better SD/N than regular spin echo, and FLASH and TurboFLASH had higher S/N. On the basis of this study, the FLASH sequence appears the most attractive for T1-weighted breath-hold imaging.

Adult↗

PubMed1991

Carcinoma of the uterus: use of gadopentetate dimeglumine in MR imaging.

This prospective study assessed the role of gadopentetate dimeglumine-enhanced magnetic resonance imaging in the detection and staging of carcinomas of the endometrium and cervix. Surgical-pathologic findings were used as the standard of reference. In the evaluation of endometrial carcinoma, contrast-enhanced imaging improved tumor detection and differentiation between viable tumor and retained debris. Use of contrast material significantly improved the staging accuracy. The ability to assess the depth of myometrial invasion was also improved. In the evaluation of cervical carcinoma, assessment of tumor location and size did not improve following contrast enhancement. Use of gadopentetate dimeglumine resulted in overestimation of stromal, parametrial, vaginal, and/or bladder wall invasion in eight patients. However, evaluation of intratumoral architecture and large lesions was easier with contrast-enhanced imaging. When only stage II and higher disease was analyzed, use of contrast material improved the evaluation of disease extent. The authors conclude that gadolinium enhancement adds to the accuracy of evaluation of endometrial carcinoma but is useful in only advanced cases of cervical carcinoma.

Adenocarcinoma↗

PubMed1991

Pancreatic disease: prospective comparison of CT, ERCP, and 1.5-T MR imaging with dynamic gadolinium enhancement and fat suppression.

New magnetic resonance (MR) imaging techniques possess features desirable for imaging the pancreas. Computed tomography (CT) and endoscopic retrograde cholangiopancreatography (ERCP) were prospectively compared with breath-hold fast low-angle shot (FLASH) and fat-suppressed spin-echo techniques before and after enhancement with gadopentetate dimeglumine. Thirty-five patients underwent ERCP, CT, and/or MR imaging studies within a 1-month period. Correlation with surgical findings, histologic findings, or clinical and/or imaging follow-up was obtained in all cases. Quantitative measurements of pancreas, pancreas minus pancreatic lesion, and pancreas minus fat signal-to-noise ratios (SNRs) were performed on MR images. The highest measurements of pancreas minus pancreatic tumor SNR were on gadolinium-enhanced, fat-suppressed images (8.9 +/- 3.4). The 1-second postcontrast FLASH images most reliably showed enhancement of normal pancreatic tissue. Nonenhanced FLASH images depicted peripancreatic fluid and inflammatory changes most successfully. The findings from this study suggest MR imaging is effective for imaging inflammatory and neoplastic pancreatic disease and may be superior to CT.

Adult↗

PubMed1991

Functional description of the left ventricle in patients with volume overload, pressure overload, and myocardial disease using cine magnetic resonance imaging.

Cine magnetic resonance imaging (MRI) is a three-dimensional imaging technique with sufficient temporal resolution to provide quantitation of left ventricular (LV) dimensions and function. It can be used to describe the three-dimensional geometrical and functional characteristics of various cardiac disease states. Accordingly, the purpose of the study was to noninvasively characterize LV function with cine MRI using LV mass, systolic wall stress, ejection fraction, and fractional wall thickening, and to compare these functional determinants among three major cardiac disease states. Patients were selected from echocardiographic criteria and specific history of disease and divided into the following groups: compensated moderate to severe aortic regurgitation; compensated LV hypertrophy caused by systemic hypertension; and dilated congestive cardiomyopathy. Normal subjects without evidence of heart disease were studied for comparison. Cine MRI was performed at 1.5 Tesla in the short-axis plane. Wall stress was calculated from MRI, along with blood pressure recordings and carotid pulse tracings, according to the Laplacian expression. The end-diastolic volume to LV mass ratio distinguished between concentric and eccentric LV hypertrophy. Peak-systolic wall stress was increased in volume overload lesions and myocardial disease and significantly different (P less than .01) compared with pressure overload lesions and normal subjects. Ejection fraction was significantly decreased (P less than .01) in myocardial disease compared with volume and pressure overload lesions and normal subjects. Among these disease states, LV mass was not different but was significantly higher in all (P less than .01) compared with normal subjects. Fractional wall thickening was increased in pressure overload lesions. Thus, the increase in LV mass in volume overload lesions and primary myocardial disease is not adequate to prevent an increase in wall stress, whereas LV mass increased sufficiently in pressure overload lesions to normalize systolic wall stress. Cine MRI can be used to noninvasively describe the three-dimensional geometry and functional state of the heart in various pathological conditions and might be used to monitor therapeutic effects.

Adult↗

PubMed1990

Interstudy reproducibility of dimensional and functional measurements between cine magnetic resonance studies in the morphologically abnormal left ventricle.

The validity of geometric formulas to derive mass and volumes in the morphologically abnormal left ventricle is problematic. Imaging techniques that are tomographic and therefore inherently three-dimensional should be more reliable and reproducible between studies in such ventricles. Determination of reproducibility between studies is essential to define the limits of an imaging technique for evaluating the response to therapy. Sequential cine magnetic resonance (MR) studies were performed on patients with dilated cardiomyopathy (n = 11) and left ventricular hypertrophy (n = 8) within a short interval in order to assess interstudy reproducibility. Left ventricular mass, volumes, ejection fraction, and end-systolic wall stress were determined by two independent observers. Between studies, left ventricular mass was highly reproducible for hypertrophied and dilated ventricles, with percent variability less than 6%. Ejection fraction and end-diastolic volume showed close reproducibility between studies, with percent variability less than 5% End-systolic volume varied by 4.3% and 4.5% in dilated cardiomyopathy and 8.4% and 7.2% in left ventricular hypertrophy for the two observers. End-systolic wall stress, which is derived from multiple measurements, varied the greatest, with percent variability of 17.2% and 15.7% in dilated cardiomyopathy and 14.8% and 13% in left ventricular hypertrophy, respectively. The results of this study demonstrate that mass, volume, and functional measurements are reproducible in morphologically abnormal ventricles.

Adult↗

PubMed1990

Normal left ventricular dimensions and function: interstudy reproducibility of measurements with cine MR imaging.

The authors evaluated the reproducibility of measurements of ventricular dimensions obtained with cine magnetic resonance (MR) imaging performed on two occasions in 11 healthy subjects. Two reviewers analyzed the studies in a blinded fashion to determine interobserver and interstudy variability of measurements of left ventricular (LV) mass, volume, ejection fraction, and systolic wall stress. LV mass showed good reproducibility between studies, with 3.6% and 3.8% variability for LV end-systolic mass for the two observers. LV end-diastolic volume varied by 5.2% and 3.9%, and LV end-systolic volume, by 9.7% and 0.9%. Variability for LV ejection fraction was 5.0% and 4.9%. The largest interstudy variability was end-systolic wall stress, 11.1% and 13.5%, which was due mostly to changes in arterial pressure between the two studies. It is concluded that anatomic and functional measurements from cine MR images are reproducible between studies. The small interstudy variability is likely related to the fact the measurements are derived directly from cine MR images that encompass the entire heart rather than depend on measurements of only sample images and the use of geometric models.

Adult↗

PubMed1990

Obstructive nephropathy: evaluation with dynamic Gd-DTPA-enhanced MR imaging.

The potential of dynamic gadolinium diethylenetriaminepentaacetic acid (DTPA)-enhanced magnetic resonance (MR) imaging for the examination of obstructive nephropathy was analyzed in 27 subjects (five healthy subjects, seven patients with dilated nonobstructed kidneys, six patients with acute obstruction, and nine patients with chronic obstruction) with use of a 1.5-T magnet. Morphologic findings were compared with quantitative analysis of temporal changes in signal intensity. Dynamic postcontrast images of the normal kidney demonstrated four phases of enhancement; cortical enhancement phase, early tubular phase, ductal phase, and excretory phase. The pattern of enhancement in dilated nonobstructed kidneys was similar to that in normal kidneys. In acutely obstructed kidneys, cortical enhancement was similar to that in normal kidneys (17% increase), but medullary enhancement was higher than normal, resulting in diminished corticomedullary differentiation. The early tubular phase was prolonged (until 2.5 minutes after injection), with delayed appearance of the ductal and excretory phases. In chronically obstructed kidneys, the increase in cortical intensity was less than that in normal kidneys (13% increase). The early tubular phase was prolonged, and the ductal phase was diminished or absent.

Acute Disease↗

PubMed1990

Fat-saturation MR imaging of the upper abdomen.

The fat-saturation (fatsat) MR technique decreases the signal intensity of fat, thereby enhancing the definition of upper abdominal organs and reducing artifacts while maintaining the T1 and T2 information available on spin-echo sequences. To evaluate the potential of fatsat in examining the abdomen, we conducted a prospective study involving 30 subjects, including four normal volunteers, 18 patients investigated for liver disease, and eight patients studied for miscellaneous abdominal disease. Short TR, 300-600/15-20 (TR/TE), and long TR, 2000-2500/20-30, 70-80, spin-echo images with and without fatsat were compared. The images were evaluated both qualitatively and quantitatively. Qualitative assessment was made with receiver-operating-characteristic (ROC) curve analysis of the confidence level of observers to detect the presence of disease, comparing fatsat with standard spin-echo sequences. ROC analysis showed greater interpreter confidence and accuracy for fatsat sequences than for standard spin-echo sequences. The measured signal-difference-to-noise (SD/N) ratio comparing upper abdominal organs with surrounding tissue revealed the highest values for short TR/TE regular spin echo, followed by short TR/TE fatsat. The highest SD/N ratio for hepatic masses was with long TR/TE fatsat followed by short TR/TE fatsat. The results of this study suggest that the fatsat technique may improve abdominal MR imaging.

Abdomen↗

PubMed1987

Percutaneous drainage of an infected mediastinal pseudocyst.

Extension of pancreatic pseudocysts into the mediastinum is a rare but recognized condition. We report an example of a complicated pseudocyst with mediastinal extension, internal hemorrhage, and infection, which was successfully drained percutaneously through the abdomen.

Abscess↗

PubMed1987

Changes in diagnostic investigation and improved detection of colon cancer, Manitoba 1964-1984.

Detection of colon cancer has improved in Manitoba over the last 20 years with decreases in diagnostic delay and failure. Between 1981 and 1984 diagnostic delay, resulting from initial false-negative examinations, occurred in 5.7% of patients. Diagnostic failure, because all investigations were negative in patients found to have cancer of the colon within one year, was 0.66%, compared with 9.5% and 5.8% respectively between 1964 and 1969. In the intervening time double-contrast barium examinations and colonoscopy were introduced and became more widely used, with a corresponding decline in single-contrast examinations. The mortality rate in the general population was unchanged despite an increased incidence, while 1980 survival rates suggested that women cancer patients were living longer than previously as well as longer than their male counterparts.

Aged↗

PubMedDate not supplied

Bowel disease: prospective comparison of CT and 1.5-T pre- and postcontrast MR imaging with T1-weighted fat-suppressed and breath-hold FLASH sequences.

The potential of new high-field-strength magnetic resonance (MR) imaging sequences to evaluate bowel disease was investigated and compared with computed tomographic (CT) studies. Thirty-two patients were studied, 14 with known or suspected gastrointestinal tumors and 18 with known or suspected bowel inflammatory conditions. T1-weighted fat-suppressed spin-echo and breath-hold FLASH (fast low-angle shot) images were obtained before and after intravenous injection of 0.1 mmol/kg gadopentetate dimeglumine. Pathologic confirmation was obtained by biopsy (n = 18), surgical excision (n = 8), or endoscopy (n = 6). CT and MR images were analyzed separately in a prospective fashion and reviewed by consensus. Information from CT and MR images was comparable in cases of confirmed bowel neoplasia. CT scans had better spatial resolution, while fat-suppressed gadolinium-enhanced MR images had better contrast resolution. In the 18 cases of bowel inflammation, CT scans showed concentric wall thickening in 16, while MR images showed concentric wall thickening in 14 and increased contrast enhancement in 17. Contrast enhancement was better appreciated on fat-suppressed images than on FLASH images. The results suggest that MR imaging may play a role in the evaluation of bowel disease.

Adipose Tissue↗

PubMedDate not supplied

Detection of acute and treated lesions of hepatosplenic candidiasis: comparison of dynamic contrast-enhanced CT and MR imaging.

Dynamic contrast-enhanced computed tomography (CT) was compared with 1.5-T magnetic resonance (MR) imaging with FLASH (fast low-angle shot), gadolinium-enhanced FLASH (Gd-FLASH), and T2-weighted fat-suppression (T2FS) sequences in 11 patients with hematologic malignancies, five with biopsy-confirmed hepatosplenic candidiasis treated with antifungal chemotherapy and six with a clinical history suggestive of acute hepatosplenic candidiasis. CT and MR images were separately interpreted in a prospective fashion. MR imaging showed lesions compatible with candidiasis in the liver in six patients, the spleen in five, and the kidneys in one. CT showed candidiasis-compatible lesions in the liver in three patients and the spleen in one; no renal lesions were shown. Differences between acute and treated candidal lesions were observed. Gd-FLASH images showed the most liver lesions (n = 106), followed by FLASH (n = 85), T2FS (n = 20), and CT (n = 18). MR imaging performed better than CT in distinguishing candidal hepatic lesions from recurrent lymphoblastic lymphoma in one patient and from hepatic infarcts in another. The results suggest that MR imaging may be superior to CT in detecting lesions of hepatosplenic candidiasis.

Acute Disease↗

PubMedDate not supplied

Cardiac masses: signal intensity features on spin-echo, gradient-echo, gadolinium-enhanced spin-echo, and TurboFLASH images.

Fifteen patients with cardiac or paracardiac masses underwent magnetic resonance (MR) imaging with spin-echo (n = 15), cine gradient-echo (n = 15), gadopentetate dimeglumine-enhanced spin-echo (n = 15), and TurboFLASH (fast low-angle shot) (n = 7) sequences. All masses had either histologic confirmation (n = 11) or confirmation with other imaging modalities (n = 4). Myxomas (n = 6) were characterized by an intermediate signal intensity (SI) on spin-echo (n = 6) and low SI on cine gradient-echo (n = 6) images and moderately high-SI contrast enhancement (n = 5). Percent contrast enhancement for myxomas was 57% +/- 11%. Thrombus (n = 4) had intermediate (n = 3) or high (n = 1) SI on spin-echo images and low (n = 2) or intermediate (n = 2) SI on gradient-echo images and did not show substantial contrast enhancement. Postcontrast first-pass TurboFLASH images were useful by clearly demonstrating the nonenhancing mass lesion in a high-SI blood pool. Other cardiac and paracardiac tumors (n = 5) showed variable pre- and postcontrast spin-echo SI; however, no other tumor showed low SI on cine gradient-echo images.

Adult↗

PubMedDate not supplied

Chronic pancreatitis: MR imaging features before and after administration of gadopentetate dimeglumine.

Magnetic resonance (MR) imaging was performed in patients with a history (> 1 year) of inflammatory pancreatic disease. Calcification was seen at recent computed tomographic examinations in 13 patients and was not seen in nine patients. On fat-suppressed spin-echo images, the signal-to-noise ratio of the pancreas was significantly lower (P < .001) in patients with pancreatic calcification (18.2 +/- 2.5 vs 38.1 +/- 6.1). On fast low-angle shot images, the percentage of contrast enhancement was also significantly lower (P < .001) in patients with calcification (26.1% +/- 5.8 vs 78.7% +/- 15.9). The results suggest that MR imaging may be useful in evaluating patients with a long history of pancreatic disease for the presence of irreversible disease.

Calcinosis↗

PubMedDate not supplied

Primary ovarian cancer: prospective comparison of contrast-enhanced CT and pre-and postcontrast, fat-suppressed MR imaging, with histologic correlation.

Sixteen patients with clinically suspected malignant ovarian disease underwent contrast agent-enhanced computed tomography (CT) and magnetic resonance (MR) imaging in a prospective comparative study. MR imaging included fat-suppressed spin-echo and breath-hold FLASH (fast low-angle shot) before and after intravenous injection of gadopentetate dimeglumine. Histologic confirmation was obtained at laparotomy (n = 13) and biopsy (n = 3). Thirteen patients had histologically proven primary ovarian cancer. MR images showed the internal architecture of ovarian tumors better than CT in nine patients and equivalently in seven. MR images showed the relationship between ovarian tumors and adjacent pelvic structures (uterus [n = 9], sigmoid colon [n = 7], bladder [n = 7], and rectum [n = 3]) better than CT in nine patients and equivalently in seven. Intraabdominal extent of disease was better defined on MR than on CT images in nine patients, equivalently in six, and worse in one. Peritoneal metastases 1-2 cm in diameter were detected on MR images and missed on CT scans in six patients. In only one case did this result in a staging error with CT. The results suggest that MR imaging is at least equivalent and may be superior to CT in the evaluation of ovarian malignancy.

Abdominal Neoplasms↗