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Biomedical subjects

K G Bis

Publications and source records attributed to K G Bis.

At least 19 recordsLinked to original sources
PubMed2001

Carotid MR angiography: phase II study of safety and efficacy for MS-325.

PURPOSE: To evaluate the safety and efficacy of MS-325 in patients suspected of having carotid arterial disease. MATERIALS AND METHODS: Fifty carotid arteries in 26 patients were imaged with three-dimensional spoiled gradient-recalled-echo magnetic resonance (MR) angiography at 5 and 50 minutes after injection of MS-325. MS-325 was administered intravenously as a single dose of 0.01, 0.03, or 0.05 mmol per kilogram of body weight as determined with a dose randomization scheme for four, nine, and 13 patients, respectively. Safety, including clinical laboratory changes and electrocardiographic monitoring, was assessed until approximately 3 days after injection. Conventional contrast agent-enhanced angiography was used as the standard of reference. Independent readers blinded to the dose interpreted the MR angiographic and conventional images. Images were assessed for location and extent of carotid arterial stenosis. RESULTS: There were no severe or serious adverse events. For the determination of clinically significant stenosis (>70%) on the 5-minute images, sensitivity, specificity, and accuracy (P =.07, three-way comparison) were 100%, 100%, and 100%; 63%, 100%, and 88%; and 40%, 75%, and 55% at 0.01, 0.03, and 0.05 mmol/kg, respectively. Sensitivity and specificity for images at 50 minutes after MS-325 administration showed the same trends as the 5-minute images. CONCLUSION: Overall accuracy for MS-325-enhanced carotid MR angiography performed during steady-state conditions of circulating contrast agent approximately 5 minutes after injection was high (88%-100%) at 0.03 and 0.01 mmol/kg. MS-325 was well tolerated at all evaluated doses.

Carotid Stenosis↗
PubMed2000

Contrast-enhanced breath-hold three-dimensional magnetic resonance angiography in the evaluation of renal arteries: optimization of technique and pitfalls.

The authors describe the optimization of a contrast-enhanced, breath-held, three-dimensional magnetic resonance angiography (CE-BH-3DMRA) technique in the assessment of the renal arteries and compare its utility with conventional x-ray angiography (XRA). Signal optimization using specific pulse sequence parameters was based on the patient's circulatory conditions, injection rate, and pulse sequence timing. Fifty-one patients (27 M, 24 F; mean age 69.7 years) were evaluated with CE-BH-3DMRA and XRA. All patients had an MR angiogram 3 months either before or after XRA. A test bolus study was performed for accurate assessment of transit time in each patient. A total of 51 patients (115 vessels) were studied in which the sensitivity and specificity for all renal artery stenoses including the proximal and mid-renal arterial segments were 96% and 92%, respectively. In-stent stenosis could only be diagnosed by quantifying flow beyond the stent using an additional triggered phase contrast cine pulse sequence. A total of 11 accessory renal arteries were correctly identified. In addition, fibromuscular dysplasia in two patients and stents in three patients were correctly identified on MRA. J. Magn. Reson. Imaging 2000;12:912-923.

Adult↗
PubMed1999

Dynamic contrast-enhanced 3D breath hold MRA using a multiple variable orientation slab acquisition.

With the conventional 3D MR angiographic sequences, it is difficult to prescribe multiple phases in different orientations, though multiple phases may be prescribed in the same orientation as the initial scan. Magnetic resonance angiography (MRA) was performed in which three slabs were prescribed in different orientations and were acquired in a sequential measurement. A fixed delay of 8 s between the slabs was used to prepare patients to hold their breath for subsequent measurements. All subjects tolerated the entire breath hold examination. The results were easily reproducible and yielded high-resolution 3-dimensional images in various planes.

Aortic Diseases↗
PubMed1999

Breath-hold 3D MR angiography of the renal vasculature using a contrast-enhanced multiecho gradient-echo technique.

OBJECTIVE: Significant evolution of contrast-enhanced MR angiography for evaluating vascular diseases in the abdomen has occurred during the past several years. The state-of-the-art gradient-echo imaging technique employs a short echo time (TE) and a short repetition time (TR) for rapid vascular imaging with contrast-enhanced MR angiography. However, because of the short TR (< or = 3-8 msec), the background stationary tissue becomes saturated, with resultant poor contrast resolution of visceral organs. The authors present a new approach to vascular imaging using a multiecho gradient-echo technique with a TR sufficiently long (41 msec) to image the renal vasculature and parenchyma without background tissue suppression. METHODS: Twenty-four partitions (3D slab thickness = 72 mm) with an in-plane resolution of 224 x 256 were obtained in 21 seconds. Three measurements were performed with an interscan delay of 8 seconds. In the pulse sequence, the partition loop is defined as the innermost loop, in which Kz views are acquired centrically for a fixed Ky, followed by Ky views in a conventional linear or sequential order. The partition encodings are segmented to permit multiple encodings in which two TR loops were used to span a total of 24 echoes with 12 along the positive and 12 along the negative direction in k space. A large bandwidth of 650 Hz/pixel was used to keep the echo train length short, with an echo spacing of 1.86 msec. A frequency-selective fat saturation pulse was placed before slab-selective excitation. The other parameters in the pulse sequence were TR/TE/flip = 41/2.2/45; the field of view was 360 to 390 mm. Maximum intensity projections of each 3D contrast-enhanced measurement were performed. The vascular-to-background contrast, bowel-related magnetic susceptibility artifact, and background stationary signals were subjectively graded. The authors examined the utility of this technique in 16 randomly selected patients (3 normal, 13 abnormal) with varied renal vasculature and parenchymal abnormalities. Results were confirmed with conventional x-ray angiography, surgery, or clinical follow-up. RESULTS: Vascular-to-background contrast was graded as very good (grade III/III) in all cases. The bowel-related magnetic susceptibility artifacts were not considered significant. Background visceral organ soft tissue contrast was not suppressed and was graded as good (grade III/III) in all cases. Eight hemodynamically significant (> 50% diameter) stenoses in seven patients were accurately assessed (one with fibromuscular dysplasia). Three patients with renal masses (two with renal cell carcinoma and one with renal lymphoma) were accurately assessed for arterial anatomy and venous extension. Other renal venous abnormalities seen were retroaortic renal vein (n = 1), chronic occlusion (n = 1), and accessories (total of five) (n = 1). CONCLUSIONS: Rapid breath-hold contrast-enhanced MR angiography of the renal vasculature with a multiecho gradient-echo using a long TR depicted the renal vasculature with high vessel-to-background contrast without significant bowel-related susceptibility artifact and without background visceral organ tissue signal suppression, resulting in high background soft tissue contrast resolution.

Artifacts↗
PubMed1998

Hepatocellular carcinoma in North America: a multiinstitutional study of appearance on T1-weighted, T2-weighted, and serial gadolinium-enhanced gradient-echo images.

OBJECTIVE: The purpose of this study was to define the common appearances of hepatocellular carcinoma (HCC) in patients in North America by analyzing T1-weighted, T2-weighted, and serial gadolinium-enhanced gradient-echo images interpreted by radiologists at multiple institutions in North America. MATERIALS AND METHODS: One hundred thirteen consecutive patients with HCC from eight institutions were included in this retrospective case series. Inclusion criteria included MR imaging examinations performed on 1.5-T MR imagers using T1-weighted breath-hold spoiled gradient-echo images, T2-weighted images, and serial gadolinium-enhanced spoiled gradient-echo images. Diagnosis was established by histology in all patients. Images were analyzed retrospectively for lesion count, lesion diameter as less than or equal to 1.5 cm and greater than 1.5 cm, and signal intensity, by individual experienced radiologists at each institution. RESULTS: We found 354 HCC lesions in the 113 patients. Tumors were solitary in 63 patients, multifocal in 45 patients, and diffuse in five patients. Lesion appearance on combined T1-weighted, T2-weighted, and immediate gadolinium-enhanced spoiled gradient-echo images was as follows: 102 lesions (29%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited diffuse heterogeneous enhancement; 52 lesions (15%) were isointense on both T1- and T2-weighted images and exhibited diffuse homogeneous enhancement (all of these lesions measured < or = 1.5 cm in diameter); 50 lesions (14%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited diffuse homogeneous enhancement; 33 lesions (9%) were hypointense on T1-weighted images, were hyperintense on T2-weighted images, and exhibited predominantly peripheral rim enhancement; and 27 lesions (8%) were hypointense on T1-weighted images, were isointense on T2-weighted images, and exhibited diffuse homogeneous enhancement. The remaining 90 lesions showed less common patterns. The appearance of HCCs greater than 1.5 cm and of HCCs less than or equal to 1.5 cm was significantly different (p = .001). The appearance of histologically proven HCCs is separately described. CONCLUSION: The combination of hypointensity on T1-weighted images, hyperintensity on T2-weighted images, and diffuse heterogeneous enhancement was the most common appearance of HCC on MR images in a multiinstitutional patient population in North America. Small HCCs measuring less than or equal to 1.5 cm were frequently isointense on both T1-weighted and T2-weighted images and may be detected on immediate gadolinium-enhanced images only as diffuse homogeneously enhancing lesions.

Adolescent↗
PubMed1997

Mesenteric circulation: three-dimensional MR angiography with a gadolinium-enhanced multiecho gradient-echo technique.

To evaluate the mesenteric circulation with magnetic resonance (MR) angiography, the authors examined 16 individuals (12 patients, four volunteers) with a gadolinium-enhanced, breath-hold, fat-saturated, multiecho, three-dimensional, gradient-echo sequence. Twenty examinations were performed. Grades of 3 or 4 (on a five-point scale [4 = best seen, 0 = not seen]) were applicable to 17 (85%) of 20 MR angiograms obtained in superior mesenteric artery trunks, 15 (75%) in celiac arteries, five (25%) in inferior mesenteric arteries; 15 (75%) of first-order branching, 12 (60%) of second-order branching, and 10 (50%) of third-order branching; 17 (85%) in superior mesenteric veins; and 17 (85%) in portal veins. MR angiography with this technique depicted the mesenteric arterial and venous circulation and the portal vein with excellent resolution in a short time.

Adult↗
PubMed1997

Contrast-enhanced breath-hold MR angiography for evaluating patency of coronary artery bypass grafts.

OBJECTIVE: The purpose of this study was to evaluate the ability of contrast-enhanced breath-hold MR angiography to reveal patency of coronary artery bypass grafts (CABGs). SUBJECTS AND METHODS: We evaluated 45 grafts (29 saphenous vein bypass grafts, 12 left internal mammary artery grafts, and four right internal mammary artery grafts) for occlusion or patency. Fifteen patients who had undergone CABG surgery underwent three-dimensional breath-hold ECG-triggered contrast-enhanced MR angiography at 1.5-T and conventional coronary angiography imaging within 24 hr of each other. MR angiograms were evaluated independently by two radiologists. Agreement between MR angiography and coronary angiography (the reference standard) was measured using Cohen's kappa statistic. RESULTS: One saphenous vein bypass graft was revealed as occluded by coronary angiography but was shown as patent by MR angiography and was excluded from statistical analysis. MR angiography was in agreement with coronary angiography in 42 of 44 grafts (kappa = 90: p < .001; sensitivity, 93%; specificity, 97%). CONCLUSION: Contrast-enhanced breath-hold MR angiography is a promising, rapid, and useful diagnostic technique for detecting graft patency in patients who have undergone CABG surgery.

Adult↗
PubMed1997

MR cholangiopancreatography (MRCP).

Magnetic resonance cholangiopancreatography (MRCP) is an evolving new technique for noninvasive imaging of diseases of the biliary tree and pancreatic duct. The advantage of this method is that one can obtain maximum intensity projection (MIP) images of the pancreatico-biliary system similar to those obtained with endoscopic retrograde cholangiopancreatography (ERCP) without the need of administration of intravenous or oral contrast. Heavily T2-weighted sequences are used that render the bile and the intraductal pancreatic fluid bright against a dark background.

Bile Ducts↗
PubMed1994

Penetrating atherosclerotic ulcers of the aorta.

PURPOSE: This study investigates the natural history and optimal imaging modality of penetrating atherosclerotic ulcers of the aorta. METHODS: We reviewed our experience with 29 penetrating ulcers in 18 patients. Computed tomography (17 patients), magnetic resonance imaging (nine patients), and aortography (five patients) were used for diagnosis and follow-up. Patients were typically elderly (average age 74 years) and had hypertension and coronary artery disease. Ulcers were most common in the distal descending thoracic aorta (31%) and were characterized by a discrete ulcer crater (100%) and thickened aortic wall (89%). Modes of presentation included chest or back pain in four patients, distal embolization in two patients, and abnormal chest radiography results in one; the remaining were incidental findings. RESULTS: Follow-up was available in ten patients with 17 ulcers from 1 to 7 years. Recurrent pain occurred in two patients, recurrent embolization occurred in one patient, and seven patients remained symptom free. Progression to saccular pseudoaneurysm occurred in five ulcers, and fusiform aneurysm occurred in two ulcers. Two ulcers were associated with an increase in aortic diameter, and nine ulcers did not change. There were no cases of aortic dissection or rupture in the follow-up period. There were no deaths and only one patient underwent resection. CONCLUSION: The natural history of penetrating atherosclerotic ulcers is one of progressive aortic enlargement, with saccular and fusiform aneurysms the result if follow-up is sufficient. Aortic dissection, aortic rupture, and embolization can also occur but are less common. Contrast-enhanced computed tomography is the primary imaging modality.

Aged↗
PubMed1993

Carcinoma of the cervix: predictive value of clinical and magnetic resonance (MR) imaging assessment of prognostic factors.

PURPOSE: This retrospective study assesses the predictive value of magnetic resonance imaging (MRI) to identify high risk cervical cancer patients. METHODS AND MATERIALS: The MRI evaluation of morphologic risk factors in patients with invasive cervical carcinoma treated with definitive radiation therapy were correlated with clinical factors and with complete tumor regression (CTR) at 6 months, tumor local control (TLC), and patient outcome at 12 months after irradiation. Sixty-six patients, median age 44.5 years, with bulky Stage I or greater disease were included in the study. RESULTS: In univariate analysis, clinical International Federation of Gynecology and Obstetrics (FIGO) stage had significant correlation with patient outcome, but it correlated poorly with complete tumor regression and tumor local control. In contrast, MRI stage showed significant correlation with complete tumor regression, tumor local control, and disease-free survival at 12 months. When each stage was analyzed separately, the greatest difference was demonstrated between clinical and MRI assignment of stage Ib disease. MRI Stage Ib disease significantly correlated with all three categories analyzed, while clinical Stage Ib did not. Superiority of MRI assessment of low stage disease was also evident in the detection of lymph node metastasis. Significant risk for nodal metastasis was related to tumor size greater than 4 cm, invasion of the parametria and urinary bladder, and stage of the disease. CONCLUSION: The multivariate analysis demonstrated that the most related variables in order of significance were the presence of juxta-regional and paraaortic lymph nodes, patient age, tumor size, and MRI tumor stage. This study demonstrates the value of MR imaging as an adjunct to clinical assessment of bulky invasive cervical cancer, rendering more complete assessment of morphologic risk factors important in patient prognosis.

Adult↗
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↗
PubMed1990

Accuracy of ultrasonic bladder volume measurement in children.

The accuracy of ultrasonography in assessing the bladder volume in 13 children with normal bladder contours was determined using the formula D x H x W (depth x height x width) with a mean error of 15.7%. This formula tends to overestimate the bladder volume in these patients. Multiplication by a correction factor of 0.9 yields a mean error of 11.5%. The accuracy of this evaluation is not dependent upon the bladder volume as the mean error was the same in those children whose bladder volume was either less than or greater than 150 cc. In addition, the accuracy of ultrasonography in assessing bladder volume was evaluated in 7 patients with an abnormal bladder contour (trabeculation, diverticula, etc.); mean error was 14.7%. In these 7 patients there was no predictable under or overestimation of bladder volume. In the children with abnormal bladder contours on ultrasound, the correction factor of 0.9 should not be used, as it does not add to the accuracy of the procedure in any individual patient. This technique is still valuable, however, in children with an abnormal bladder for it allows estimation of the extent of emptying without invasive catheterization.

Adolescent↗
PubMed1990

Surface coil FLASH magnetic resonance imaging of the fasting and secretin-stimulated pancreas.

The purpose of this study is to investigate the response of the pancreas to secretin stimulation using magnetic resonance imaging (MRI). Using the Siemens 1.0 T Magnetom and a Helmholtz surface coil, single breath FLASH-MRI of the normal fasting pancreas was performed in the prone position, both before and after a 20-minute period after intravenous (IV) bolus injection of secretin (2 cu/kg). T2*-weighted fast low-angle shot sequences (TR = 150 mseconds; TE = 30 mseconds; flip angle = 10 degrees; matrix = 256 X 256; acquisitions = 2) demonstrated an immediate response manifested by a significant distension of the duodenum with fluid secreted by the pancreas, as well as a gradual decline of the pancreas/muscle signal intensity (SI) ratio over time. Twenty minutes after secretin administration, the mean percent decrease of the pancreas/muscle SI ratio in six volunteers was 11.6 +/- 6.4 (1-STD). This is statistically significant (P less than .003) given a mean percent increase of the pancreas/muscle SI ratio of 1.6 +/- 4.8 (1-STD) in five volunteers 20 minutes after bolus injection of saline (control). Although significant duodenal distension is easily demonstrated after secretin administration, the decrease of the relative pancreatic SI over time is visually subtle. Further work is needed to enhance imaging of the physiologic response of the pancreas using even more rapid imaging techniques.

Adult↗