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Biomedical subjects

R Vosshenrich

Publications and source records attributed to R Vosshenrich.

At least 37 records · Page 2Linked to original sources
PubMed1999

Hepatic blood supply: comparison of optimized dual phase contrast-enhanced three-dimensional MR angiography and digital subtraction angiography.

PURPOSE: To optimize and determine the value of dual-phase contrast material-enhanced three-dimensional (3D) magnetic resonance (MR) angiography for preoperative evaluation of the blood supply to the liver. MATERIALS AND METHODS: Dual phase 3D MR angiography of the hepatic arteries and portal vein was performed in 140 patients. In 80 patients, the value of fat saturation, digital image subtraction, an anticholinergic agent, and a high-caloric meal were evaluated. In the next 60 patients, MR angiographic and digital subtraction angiographic (DSA) image quality and diagnostic value were compared. RESULTS: Fat-saturated images were of significantly better quality (P < .01) than non-fat-saturated images. Digital image subtraction was useful in only 23 of 40 patients. The injection of an anticholinergic agent was superfluous, whereas administration of a high-caloric meal helped in demonstration of the superior mesenteric artery and portal vein. Classification on MR angiograms of the arterial blood supply was correct in 57 of 60 patients. All arterial and portal venous lesions were seen on MR angiograms, and MR angiograms had a significantly higher subjective image-quality ranking than did DSA images in the evaluation of the portal vein (P < .05). CONCLUSION: Fat saturation and use of a high-caloric meal improve the results of MR angiography of hepatic vessels. MR angiography was comparable to DSA for evaluation of the arterial system and was superior for demonstration of the portal vein; therefore, MR angiography could replace intraarterial DSA.

Angiography, Digital Subtraction↗
PubMed1998

Electrocardiograph-triggered two-dimensional time-of-flight versus optimized contrast-enhanced three-dimensional MR angiography of the peripheral arteries.

We determined whether the accuracy of magnetic resonance angiography (MRA) in the peripheral run-off vessels can be improved by using contrast-enhanced (CE) three-dimensional (3D) technique in comparison to electrocardiograph (ECG)-triggered two-dimensional (2D) time-of-flight (TOF) technique. In a prospective study 20 patients with occlusions of the pelvic and/or femoral arteries underwent a CE 3D MRA (repetition time (TR): 5 ms, (TE) echo time: 2 ms, flip angle (FA): 30 degrees ) and an ECG-triggered 2D time-of-flight (TOF) technique (TR: 408 resp. 608 ms, TE: 7 ms, FA: 70 degrees) of the run-off vessels on a 1.5 T MR system. Each patient received a contrast material volume of 0.15 mmol/kg of body weight of gadolinium (Gd)/DTPA using an automatic injector. The tube system to the patient was flushed by 50 mL of a saline solution applied with the same injection rate as the contrast material administration. The start of the 3D MR sequence was tailored individually to the applied contrast material after determination of circulation times by a prior bolus. All patients underwent each conventional or digital arteriography for comparison, as well. The visualization of the run-off vessels was ranked on a scale of 0-3 (0 = poor, 1 = fair, 2 = good, 3 = excellent) by three blinded reviewers. They also graded the vascular segments as either occluded or significantly altered (>50% reduction in diameter) or free of significant stenosis. CE 3D MRA was significantly faster in imaging the run-off vessels in comparison to the ECG-triggered 2D TOF technique. All 160 vascular segments were visualized with the 3D method, whereas only 142/160 segments were seen with 2D technique. The resulting image quality ranking of all vascular segments was significantly higher (p < 0.05) using CE 3D MRA (2.8) than with the 2D TOF technique (2.4). The detection of the stenoses was possible with both techniques. The grading of seven of seven stenoses was correct with 3D method and in five of seven cases with the 2D TOF technique. All vessel occlusions were detected by using both techniques. Small collaterals were visualized in more detail with the CE 3D MR angiography. These data demonstrate an improvement in image quality and accuracy of MRA of the peripheral arteries using a CE 3D technique in comparison to an ECG-triggered 2D TOF sequence.

Contrast Media↗
PubMed1998

[Contrast media-enhanced 3D MR angiography of the peripheral vessels using a "tracking technique": preliminary results].

PURPOSE: A single bolus contrast-enhanced (CE) 3D MR angiography (MRA) of the peripheral vessels was evaluated using a combination of two surface coils with manual incrementation of the patient table. METHODS: Fifteen patients with peripheral arterial occlusive disease were examined using an ultrafast CE 3D MRA (TR/ TE/FA 5 ms/2 ms/30 degrees). For imaging of the vessels from the distal aorta to the arteries of the lower limbs a combination of a body-array coil and a flexible extremity coil was applied. A coil-interface was designed for a connection of the two coils. The examinations were performed after a single bolus of 0.15 mmol Gd-DTPA/kg. The tracking technique included a manual incrementation of the patient table and the coil-interface had to be switched from the body-array coil to the flexible extremity coil. For acquisition delay measurement of the MR sequence the individual transit times of the contrast material were detected by using a test bolus. RESULTS: CE 3D MRA was technically successful in 14/15 cases. In one case two vascular segments were not imaged. The qualitative evaluation of all vascular segments documented a high quality without any significant differences between the proximal and the distal arteries (p < 0.05). All hemodynamically significant stenoses (n = 15) and all vessel occlusions (n = 36) were detected. CONCLUSION: The single bolus CE 3D MRA using a tracking technique is a favourable method in the evaluation of patients with peripheral arterial occlusive disease.

Arterial Occlusive Diseases↗
PubMed1998

[Determination of contour clarity in contrast-enhanced MR angiography: definition and clinical evaluation exemplified by ECG-triggered imaging of the thoracic aorta].

PURPOSE: The sharpness of the vessel contour in 3D contrast-enhanced MR angiography is defined by particular measurements of the signal intensity. To evaluate the facilities of an ECG-triggered data acquisition to optimize the MRA image quality of the thoracic aorta. METHOD: In phantom studies the sharpness of the vessel contour was defined as the distance of the extraluminal signal-minimum to the extraluminal maximum. Afterwards 30 examinations of the thoracic aorta with and without the use of an ECG-triggering were evaluated with regard to the sharpness of the vessel outline. RESULTS: The presented definition of the signal intensity is suitable for objective measurements of the vessel outline. At the level of the ascending aorta, ECG-triggered data acquisition increased the image quality significantly. CONCLUSIONS: An easy, practicable definition enables measurements of the sharpness of the vessel outline. ECG-triggered data acquisition is recommended for optimal visualization, especially of the ascending aorta.

Aorta, Thoracic↗
PubMed1998

Differences in injection rates on contrast-enhanced breath-hold three-dimensional MR angiography.

OBJECTIVE: The aim of the study was to evaluate the optimization of injection rates with an automatic power injector versus manual injection for contrast-enhanced breath-hold three-dimensional (3D) MR angiography of the abdominal aorta and its branches. SUBJECTS AND METHODS: In a prospective study, 50 patients underwent breath-hold 3D MR angiography (5/2 [TR/TE]; flip angle, 30 degrees) of the abdominal vessels on a 1.5-T system. Each patient received 0.15 mmol/kg of gadopentetate dimeglumine. All patients were randomly assigned to one of five equally sized groups. The contrast bolus was injected manually in group 1, always by the same investigator, who tried to perform a steady injection rate of 2 ml/sec. An automatic injector was used in groups 2-5 with injection flow rates of 0.5 ml/sec, 2 ml/sec, 4 ml/sec, and 6 ml/sec. The start of the MR sequence was tailored individually to the applied volume of contrast material after determination of circulation times by a test bolus. We measured the signal-to-noise and contrast-to-noise ratios as well as the relative vascular enhancement. The visualization of different abdominal vessel segments was independently ranked on a scale of 1-5 (1 = not visible; 5 = excellent visualization) by three reviewers who were unaware of the applied contrast material injection rate. RESULTS: The signal-to-noise and contrast-to-noise ratios of groups 3 and 4 (2 ml/sec and 4 ml/sec, respectively) were significantly (p < .05) higher than the ratios of groups 1, 2, and 5. The average relative vascular enhancement of groups 3 and 4 was significantly higher (p < .05) than the enhancement of all other groups. The contrast bolus applied with a faster injection rate (group 5) did not cover large parts of the K-space, resulting in increased blurring of the vessel contours. The subjective evaluation of large and small diameter vessels showed significantly better results in groups 3 and 4 than in groups 1, 2, and 5. CONCLUSION: The use of an automatic MR power injector proved superior to manual injection of contrast material. The optimal injection rate was 2 ml/sec for 3D breath-hold MR angiography of the abdominal vessels.

Aorta, Abdominal↗
PubMed1998

[Case report of a large lipomatous soft tissue tumor].

A case of diffuse infiltrating lipomatosis is reported. This entity represents a particular type of lipoma. It can be distinguished from other fatty tumors by its localisation, extent, therapeutic procedure, and prognosis. Magnetic resonance imaging (MRI) enables the differentiation from lipomatosis pelvis and malignant tumors as well. Histopathological examination, however, is necessary to exclude liposarcoma. Further growth or recurrence of diffuse infiltrating lipomatosis can be detected by MRI follow-up examinations.

Buttocks↗
PubMed1998

Arthroscintigraphy in suspected rotator cuff rupture.

AIM: In order to evaluate the diagnostic efficiency of arthroscintigraphy in suspected rotator cuff ruptures this new imaging procedure was performed 20 times in 17 patients with clinical signs of a rotator cuff lesion. The scintigraphic results were compared with sonography (n = 20), contrast arthrography (n = 20) and arthroscopy (n = 10) of the shoulder joint. METHODS: After performing a standard bone scintigraphy with intravenous application of 300 MBq 99m-Tc-methylene diphosphonate (MDP) for landmarking of the shoulder region arthroscintigraphy was performed after an intraarticular injection of 99m-Tc microcolloid (ALBU-RES 400 MicroCi/5 ml). The application was performed either in direct combination with contrast arthrography (n = 10) or ultrasound conducted mixed with a local anesthetic (n = 10). Findings at arthroscopical surgery (n = 10) were used as the gold standard. RESULTS: In case of complete rotator cuff rupture (n = 5), arthroscintigraphy and radiographic arthrography were identical in 5/5. In one patient with advanced degenerative alterations of the shoulder joint radiographic arthrography incorrectly showed a complete rupture which was not seen by arthroscintigraphy and endoscopy. In 3 patients with incomplete rupture, 2/3 results were consistent. A difference was seen in one patient with a rotator cuff, that has been already revised in the past and that suffered of capsulitis and calcification. CONCLUSION: Arthroscintigraphy is a sensitive technique for detection of rotator cuff ruptures. Because of the lower viscosity of the active compound, small ruptures can be easily detected, offering additional value over radiographic arthrography and ultrasound, especially for evaluation of incomplete cuff ruptures.

Adult↗
PubMed1997

[Contrast medium enhanced MR angiography of peripheral blood vessels].

Currently 2D time-of-flight MR angiography (MRA) is most commonly used for the evaluation of the extremities. The major limitation is their susceptibility to signal loss from intravoxel phase dispersion. This leads to overestimation in the grading of stenoses. Further difficulties are motion artifacts and the limited spatial resolution. Phase-contrast MRA is increasingly used. However, further studies are required to verify its diagnostic potential. MRA technology continues to advance rapidly. Stronger gradient fields, shorter echo times and high resolution surface coils are developed. Contrast medium can be applied under standardized conditions with MR compatible power injectors. In phantom studies, the contrast-enhanced gradient echo sequences show reduced phase dispersion, resulting in an improved grading of stenoses. Initial patient studies underline these findings. Contrast-enhanced MR angiography has the potential to replace invasive arteriography in the evaluation of peripheral arterial vessels in the near future.

Arteriosclerosis↗
PubMed1997

Sexual dysfunction in Peyronie's disease: an analysis of 222 patients without previous local plaque therapy.

PURPOSE: We obtained an objective evaluation of erectile function in patients with Peyronie's disease. MATERIALS AND METHODS: Sexual dysfunction was analyzed in 222 patients with Peyronie's disease without previous local plaque therapy using a standardized protocol. RESULTS: Of the 222 patients 70 (31.5%) complained of not being able to perform intercourse. In 4 men (1.8%) standardized diagnostic procedure demonstrated only a severe angulation making coitus impossible, and in 3 men (1.4%) intercourse became unsatisfactory due to pain. Seven men (3.1%) reported distal penile flaccidity, including 4 in whom dynamic pharmacocavernosometry and pharmacocavernosography revealed veno-occlusive dysfunction. Of 56 men who complained of a complete loss of erection 51 did not respond to intracavernous pharmacological injection with prostaglandin E1, and 27 (48.2%) had abnormal arterial blood flow as shown by duplex sonography of the cavernous arteries, 47 (83.9%) had evidence of veno-occlusive dysfunction based on cavernosometric criteria and 33 (58.9%) also had cavernosographic evidence of the condition. Plaque associated venous drainage was evident in 15 of the 56 impotent patients (26.8%), equivalent to 45.5% of all cases with abnormal cavernosographic findings. CONCLUSIONS: Sexual dysfunction was evaluable in 31.5% of patients, and the main cause of impotence and loss of erection was veno-occlusive dysfunction.

Adult↗
PubMed1997

[Results of a contrast-medium supported 3D MR-angiography in respiratory arrest following optimization of contrast medium bolus].

PURPOSE: Reduction of the contrast material volume by optimised bolus administration during a breath-hold 3D MR angiography and its clinical value. MATERIALS AND METHODS: Breath-hold ultrafast 3D gadolinium-enhanced MR angiography (TR 5 ms, TE 2 ms, FA 20 degrees) of the thoracic and abdominal aorta was performed in 50 patients and correlated with an i.a. DSA. 25 patients (group 1) were examined with a contrast material volume of 40 ml Gd-DTPA and three successive acquisitions at fixed intervals (25, 53 and 81 s) after start of the contrast material injection. Another group of 25 patients (group 2) received only 20 ml Gd-DTPA and the start of the MR acquisition was determined individually by prior evaluation of the contrast material transit times after injection of a test bolus. The signal-to-noise (S/N) and contrast-to-noise (C/N) ratios were compared and a subjective image quality rating (0-3) by three reviewers was achieved in both groups. RESULTS: A total of 37 vascular pathologies were correctly detected by MR angiography compared to i.a. DSA. The grading of stenoses was overestimated in some cases. The S/N and C/N were higher in group 2 (63.2 and 50.1) than in group 1 (58.0 and 38.9). The subjective ratings also showed better results in group 2 (2.76) than in group 1 (2.20). CONCLUSION: The ultrafast gadolinium-enhanced 3D MR angiography allowed a reliable visualisation of the thoracic and abdominal aorta and its branches in a single breath-hold. An optimised examination with a reduced contrast material volume can be achieved by an individual adaptation of the MR acquisition to contrast material administration after measurement of the contrast material transit times.

Aged↗
PubMed1997

[MR angiography of the pelvic-leg blood vessels: current status and perspectives].

Currently 2D time-of-flight (TOF) MR angiography (MRA) is most commonly used for the evaluation of the extremities. The major limitation of all MRA techniques is their susceptibility to signal loss from intra-voxel phase dispersion. This leads to an overestimated grading of the stenosis. Further difficulties are motion artifacts and the limited spatial resolution. Therefore, MRA alone cannot be used routinely as a preoperative diagnostic procedure in patients with peripheral arterial disease. The postoperative examination of patients with vascular bypasses, however, seems to be a practical application of this technique. It is also possible to use MRA to image the lower limbs after percutaneous interventional angioplasty. The application of 2D-ECG-triggered sequences or the current fast technique of contrast-enhanced 3D-TOF MRA might play a role in combination with surface coils for future examinations of peripheral arterial disease.

Arterial Occlusive Diseases↗
PubMed1996

[2-D-time-of-flight MR angiography of the peripheral blood vessels. Experimental and clinical studies on value of this method in arterial occlusive diseases].

PURPOSE: A retrospective study was performed in 70 patients with peripheral vascular disease who underwent MR angiography of the lower extremity. MATERIAL AND METHODS: MR angiography was performed with a 2-D-TOF sequence including a travelling presaturation to suppress the venous signal. Postprocessing images were obtained with the MIP algorithm. The MRA results were compared with conventional or digital angiography in all patients. RESULTS: Only 19 stenoses out of 31 which showed a degree of stenosis between 30 and 99% could be visualised by MR angiography. 9 stenoses were correctly classified by MRA. In 9 cases the degree of stenosis was overestimated, in one case it was underestimated. All 56 occlusions were correctly detected. 12 severe stenoses diagnosed with conventional angiography were graded as occlusions with MR angiography. CONCLUSIONS: MR angiography cannot be accepted in preoperative staging of patients with peripheral vascular disease. The postoperative examination seems to be a practical noninvasive alternative.

Algorithms↗
PubMed1996

[MRI-controlled intervention in suspected lesions of the breast].

PURPOSE: To evaluate two different systems for magnetic resonance (MR) imaging-guided breast interventions. MATERIALS AND METHODS: 41 patients with 41 lesions detected exclusively with contrast-enhanced MR imaging underwent 68 interventional procedures (27 needle biopsies and 41 preoperative wire localisations) with two different systems. An add-on device for surface coils was used in 39 cases, and a dedicated single breast biopsy coil was used in 29. For needle biopsies, material was aspirated with nonmagnetic 19.5 gauge needles. For preoperative localisations, nonmagnetic wires were used. RESULTS: Surgical excision verified the cytological findings in 23 of the 27 cases sampled for biopsy. Cytological diagnosis was impossible in three cases. One technical failure occurred with the biopsy coil. Open biopsy performed after MR imaging-guided localisation successfully removed 38 of the 41 lesions. One missed carcinoma was found at repeat localisation and removed. Two technical failures occurred with the biopsy coil. In these cases, the lesions were close to the chest wall. CONCLUSIONS: Both systems are suitable for MR-guided fine-needle biopsy and preoperative localisation of breast lesions seen exclusively on MR images.

Biopsy, Needle↗
PubMed1996

Measurements of magnetism-related forces and torque moments affecting medical instruments, implants, and foreign objects during magnetic resonance imaging at all degrees of freedom.

We designed a novel force/torque moment transducer with six degrees of freedom. This new sensor is used for measuring the forces and torque moments exerted by static magnetic resonance imaging (MRI) fields on various medical implants, instruments, and ballistic shell fragments. To determine the location of strongest effect the inhomogeneity of the magnetic field between the entrance of the MRI-tube (portal), and the imaging section was measured. Force and torque moments of a sample of 45 objects were measured at two positions, at the portal, and in the center of the imaging section. We classified the objects regarding to the magnetism-related forces measured in the homogeneous part of the MRI tube. About one-third of the objects was non- or weakly magnetic, one-third moderately, and the last third was strongly magnetic. Forces within the inhomogeneous area of the magnetic field at the entrance part of the tube were up to half a magnitude larger than forces inside the homogeneous imaging section. Here the greatest potential risks to patients might occur.

Biophysical Phenomena↗
PubMed1996

MR arthrography in the diagnosis of rotator cuff tears. Standard spin-echo alone or with fat suppression?

PURPOSE: To examine the value of fat-suppressed images in MR arthrography of the shoulder in patients with rotator cuff tears. MATERIAL AND METHODS: MR arthrography was performed in 25 patients (9 women, 16 men) ranging from 19 to 64 years. Standard T1-weighted spin-echo images (sSE) and fat-suppressed images (FS) were obtained after intraarticular injection of contrast material. The MR studies were analyzed according to contrast, image quality and conspicuity of pathology. A diagnosis was established without knowledge of the conventional arthrographic findings on the basis of sSE versus FS techniques. RESULTS: The contrast between the intraarticular fluid and the adjacent structures in FS images was increased compared to sSE images in all patients. The conspicuity of anatomical structures was improved in 8 patients. Without fat suppression, 2 false-negative and one false-positive full-thickness tears were diagnosed. With the FS technique, 14 full-thickness tears and 4 partial-thickness tears of the cuff were correctly classified. CONCLUSION: The results suggest that, if MR arthrography is chosen for a diagnosis of rotator cuff disorders, a fat suppression sequence should be included.

Adult↗
PubMed1996

[Contrast medium assisted dynamic MR-mammography after diagnostic and therapeutic interventions on the breast].

In a retrospective study, the authors evaluated the signal behavior of 150 patients after intervention in the breast (40 fine-needle biopsies, 10 core biopsies, 50 open biopsies, 50 tumor-ectomies with additional irradiation therapy). The MR imaging was performed on 1.5-Tesla whole-body scanners using T1-WI GRE sequences in 2D FLASH technique before and 5 times after i.v. application of 0.1 mmol gadopentetate-dimeglumine per kg body weight. There was no signal enhancement after fine-needle biopsy. Hematoma due to core biopsy caused signal increase in every 5th patient. Enhancement after open biopsy was no more visible 6 months postoperatively. 12 months after tumorectomy and radiation therapy, most patients showed no more signal enhancement. In conclusion, MR mammography can be performed after fine-needle biopsy without problems. In case of core biopsy, hematoma should be excluded by sonography before. MR mammography should not be performed within 6 months after open biopsy, or within 12 months after tumorectomy and radiation therapy.

Biopsy↗