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Biomedical subjects

T F Hany

Publications and source records attributed to T F Hany.

12 recordsLinked to original sources
PubMed1998

[Clinical use of contrast-enhanced MR angiography].

Compared to other non-invasive MR-angiography techniques, contrast-enhanced MR angiography is a robust imaging technique in the assessment of the arterial vascular system. This is due to the use of three-dimensional data acquisition, non-nephrotoxic paramagnetic contrast and short acquisition times. Clinical applications include the evaluation of the thoracic and abdominal arterial vessels. With the refinement of this technique also small peripheral arteries of the extremities can be imaged and an entire non-invasive diagnostic work-up of the peripheral arteries will be possible.

Contrast Media↗
PubMed1998

MR-based assessment of vascular morphology and function.

Initially, time-of-flight angiography found its way into clinical routine for imaging vascular morphology. In conjunction with phase-contrast imaging, functional and morphological assessment of vascular pathology became possible. The flow dependence and associated artifacts inherent to these techniques have restricted the clinical use of these magnetic resonance angiography (MRA) techniques to the extra- and intracranial arterial, as well as the systemic and portal, venous systems. With the advent of high-performance gradient systems a new, promising MRA strategy has been developed: contrast-enhanced 3D MR angiography. It is based on the combination of rapid 3D imaging and the T1-shortening effect of intravenously infused paramagnetic contrast. This review provides a technical overview and critically discusses the clinical application for the different MRA techniques regarding morphological as well as functional assessment of the vascular system.

Adult↗
PubMed1998

Dynamic MR defecography with a superconducting, open-configuration MR system.

PURPOSE: To evaluate dynamic magnetic resonance (MR) defecography performed with a superconducting, open-configuration system in diagnosis of defecation disorders. MATERIALS AND METHODS: Five healthy volunteers and 15 patients with defecation disorders were studied with MR defecography performed with a superconducting, open-configuration system; the patients also underwent fluoroscopic defecography. Before MR imaging, the rectum was filled with 300 mL of mashed potatoes mixed with 1.5 mL of gadopentetate dimeglumine. T1-weighted gradient-echo images were acquired every 2 seconds in the midsagittal plane with the patient at rest, at maximal contraction of the anal sphincter, during straining, and during defecation. RESULTS: MR defecography permitted analysis of the anorectal angle, anal canal, puborectal muscle, and descent of the pelvic floor. Owing to the high signal intensity of the intraluminal contrast material, the rectal walls were well demonstrated on the MR images, permitting visualization of intussusception and rectocele. Concomitant demonstration of structures surrounding the anorectal canal was helpful in assessment of spastic pelvic floor syndrome and descending perineum syndrome. MR defecography was superior to fluoroscopic defecography and allowed detection of all clinically relevant pathologic conditions except for one. CONCLUSION: Dynamic MR defecography is an attractive alternative for evaluation of defecation disorders.

Aged↗
PubMed1998

Diagnostic impact of four postprocessing techniques in evaluating contrast-enhanced three-dimensional MR angiography.

OBJECTIVE: The purpose of this study was to determine the added diagnostic value of various three-dimensional (3D) data viewing techniques when analyzing contrast-enhanced 3D MR angiography. MATERIALS AND METHODS: Twenty patients (mean age, 62 years) with symptomatic peripheral vascular disease were assessed with breath-hold, contrast-enhanced 3D MR angiography and catheter angiography, which served as the standard of reference. After an initial interpretation of the 3D MR angiographic data sets based only on standardized maximum intensity projections (MIP), the diagnostic gain of the stepwise addition of interactive multiplanar reformations, shaded-surface displays (SSD), and virtual intraarterial endoscopy (VIE) images was calculated. Time required for each step of postprocessing was measured. RESULTS: Pathologic changes were revealed by catheter angiography in 60 vascular segments (50 severe stenoses, seven aneurysms, and three occlusions). The average postprocessing times were MIP, 8 min (range, 5-12 min); multiplanar reformations, 9 min (range, 3-11 min); SSD, 15 min (range, 8-25 min); and VIE, 40 min (range, 18-63 min). Addition of multiplanar reformations to MIPs resulted in the greatest gain of diagnostic accuracy, from 92% to 96%, and diagnostic confidence. When analysis was based on all four techniques, receiver operating characteristic curve analysis revealed only minimal improvements in diagnostic confidence, whereas diagnostic accuracy remained unchanged at 96%. CONCLUSION: Accurate and time-effective analysis of contrast-enhanced 3D MR angiography should be based on MIP algorithms and multiplanar reformations. Additional evaluation with VIE or SSD techniques is time-consuming and provides little diagnostic gain.

Adult↗
PubMed1997

[Value of contrast-enhanced 3D magnetic resonance angiography of the renal arteries].

PURPOSE: To determine the value of gadolinium-enhanced, three-dimensional breath-hold Magnetic Resonance Angiography (MRA) in the assessment of the aorta and renal arteries in comparison to conventional arteriography (CA). PATIENTS AND METHODS: 49 patients were evaluated with both CA and 3D MRA. 0.3 mmol/kg BW gadolinium-DTPA was administered intravenously in a bolus, using an automated injector. A test bolus method was used for timing of the bolus and beginning of the data acquisition. The intraarterial CA was used as the gold standard. RESULTS: MRA-based assessment of renal artery stenosis was identical with CA in 31 of 45 stenoses (68.8%). Sensitivity and specificity for assessment of renal arterial disease by MRA were 84% and 96%; for clinically relevant lesions they amounted to 90% and 98%. CONCLUSION: The presented contrast-enhanced 3D MRA technique allows for the reliable assessment of renal arterial morphology and pathology.

Adult↗
PubMed1997

[Ultrafast contrast-enhanced 3D MR angiography of the aorta and renal arteries in apnea].

PURPOSE: To determine the value of ultrafast, gadolinium-enhanced, three-dimensional breathhold magnetic resonance angiography (MRA) in the assessment of the aorta and renal arteries in comparison to conventional arteriography (CA). PATIENTS AND METHODS: 49 patients (31 m, 18 f) were evaluated with both CA and 3D MRA. The 3D MRA data set consisted of 44 continuous sections, acquired in apnoea (23-28 s) using the following parameters: TR/TE 3.9/1.5 ms, flip angle 40 degrees, 3/4 k-space acquisition. 0.3 mmol/kg BW gadolinium-DTPA were administered intravenously in a bolus, using an automated injector. A test bolus method was used for timing of the bolus and beginning of the data acquisition. Intraarterial CA was used as the gold standard in 47 patients; in two patients the intraoperative findings were employed as the standard of reference. CA and MRA were interpreted separately by two different radiologists, who were blinded to the results of the other examiner. RESULTS: All 11 accessory renal arteries were visualised on MRA. MRA-based assessment of renal artery stenosis was identical with CA in 31 of 41 (75%) stenoses, Sensitivity and specificity values for assessment of renal arterial disease were 84.4% and 96.1%, for haemodynamically significant lesions they amounted to 90% and 98.9%, respectively. CONCLUSION: The presented ultrafast contrast-enhanced 3D MRA technique allows for the reliable assessment of aortic and renal arterial morphology and pathology.

Adult↗
PubMed1997

Evaluation of the aortoiliac and renal arteries: comparison of breath-hold, contrast-enhanced, three-dimensional MR angiography with conventional catheter angiography.

PURPOSE: To determine the diagnostic accuracy of breath-hold, contrast material-enhanced, three-dimensional (3D) magnetic resonance (MR) angiography in the assessment of the aortoiliac inflow tract and renal arteries with conventional catheter angiography as the standard of reference. MATERIALS AND METHODS: In 39 patients with symptomatic peripheral vascular disease, both catheter and contrast-enhanced, 3D MR angiography were performed. In a prospective blinded analysis, each vascular segment (23 segments per arterial tree) was evaluated for the presence of obstructive stenosis, graded as mild (<50%), severe (50%-99%), or occlusion (100%), as well as for aneurysmal disease. RESULTS: Obstructive (n = 2) and aneurysmatic aortic (n = 6) lesions and 10 of 11 accessory renal arteries were identified and graded correctly with MR angiography. For detection of hemodynamically significant stenotic lesions (>50%) or occlusions with MR angiography, sensitivity and specificity, respectively, were 93% and 98% for the renal arteries, 96% and 100% for the common iliac arteries, 93% and 93% for the external iliac arteries, and 96% and 94% for the internal iliac arteries. CONCLUSION: The diagnostic performance of contrast-enhanced 3D MR angiography is comparable with that of catheter angiography and thus may contribute to assessment of the aorta, the renal arteries, and the pelvic arterial system in patients with peripheral vascular disease before they undergo therapy.

Angiography, Digital Subtraction↗
PubMedDate not supplied

Optimization of contrast timing for breath-hold three-dimensional MR angiography.

The purpose of this study was to determine the influence of various factors (age, weight, breathing, saline flush) on the contrast kinetics of a test bolus injection for the purpose of calculating the scan delay for optimized contrast-enhanced three-dimensional MR angiography. Initially, the test bolus administration was optimized by evaluating the influence of breathing (breathing versus breath-hold) and the administration of a saline flush after the contrast injection (no flush versus flush) on the kinetics of a 4-ml Gd-DTPA test bolus injection in three healthy volunteers. Subsequently, in 33 patients referred for three-dimensional MR angiography of the renal arteries, test bolus kinetics were correlated to age, weight, and heart rate. In addition, the image quality of the three-dimensional MR angiograms was assessed on a four-point scale with regard to vessel visibility. The administration of a saline flush after the contrast injection significantly shortened the first appearance time (14 versus 16 seconds, P < .05), as well as the time to maximal signal intensity (SI) (6 versus 10 seconds, P < .05) and increased both maximum (67 versus 151 seconds, P < .05) and the SI slope (6.4 versus 20.5 seconds, P < .05). Breath-holding was shown to have no significant affect on the test bolus kinetics. No correlation was found between physiologic parameters and test bolus kinetics in the patient group. Image quality was graded as sufficient for diagnostic purposes in 32 of 33 patients. The contrast travel time from injection site to the vascular system under consideration cannot be predicted based on physiologic parameters. This time interval can be reliably and accurately determined by a test bolus injection of a small volume of contrast agent followed by a saline flush during normal breathing.

Adult↗
PubMedDate not supplied

Value of image subtraction in 3D gadolinium-enhanced MR angiography of the renal arteries.

The objective of this study was to evaluate quantitatively and qualitatively the effect of image subtraction on the image quality of three-dimensional (3D) gadolinium-enhanced MR angiograms of the renal arteries. Breath-hold 3D gadolinium MR angiography (MRA) as well as conventional contrast angiography of the renal arteries was performed on 20 patients with suspected renovascular hypertension. MR angiograms were acquired before and during dynamic infusion of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). Contrast-enhanced images were compared with images that had undergone voxel-by-voxel signal intensity subtraction of contrast-enhanced data from precontrast data. One false positive finding for significant renal artery stenosis was recorded with MRA using conventional angiography as the gold standard. Image subtraction did not alter the diagnosis at MRA in any case. The mean contrast-to-noise ratio (CNR) was significantly higher (P < .05) on the subtraction MR angiograms compared to the nonsubtracted MR angiograms. There was no significant difference in the signal-to-noise ratio (SNR). Qualitative analysis revealed a significant improvement in image quality after image subtraction with respect to visualization of the distal renal arteries. In conclusion, image subtraction improves the quality of renal MRA in terms of both CNR and visualization of the distal renal arteries.

Adult↗
PubMedDate not supplied

Postprocessing techniques for gadolinium-enhanced three-dimensional MR angiography.

Contrast material-enhanced three-dimensional (3D) magnetic resonance (MR) angiography is rapidly gaining acceptance as a versatile noninvasive alternative to conventional angiography. The technique has proved useful in the visualization and assessment of complex pathologic entities in the thoracic and abdominal aorta, renal arteries, pelvic arterial system, and pulmonary arteries. Several postprocessing techniques are available for reformation of the imaging data, including maximum intensity projection (MIP), surface rendering, and virtual intraluminal endoscopy (VIE). MIP and subvolume MIP reconstructions can be produced quickly and are useful for demonstration and archiving purposes. Because of its unique ability to display vessels without overlap, surface rendering is especially useful in depicting diseases that influence either the outer shape of the vessels or their topographic arrangement. VIE allows assessment of the inside of the vascular wall and is helpful in detecting wall-bound thrombus and evaluating the degree of stenosis. Most clinically relevant questions (eg, presence of pulmonary embolism, aortic aneurysm, renal artery stenosis) can be fully answered if analysis is based on MIP and thin multiplanar reformations of contrast-enhanced 3D MR angiograms. In some cases, the use of additional postprocessing techniques enhances diagnostic confidence.

Aorta↗