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M Reiser

Publications and source records attributed to M Reiser.

At least 397 records · Page 22Linked to original sources
PubMed1997

[Three-dimensional thickness and volume measurements of the knee joint cartilage by MR tomography: reproducibility in volunteers].

OBJECTIVE: To determine the reproducibility of three-dimensional volume and thickness measurements of the knee joint cartilage with MRI in volunteers. METHODS: The knees of 7 healthy individuals (ages 23 to 58 yrs.) were sagittally imaged with a resolution of 2 x 0.31 x 0.31 mm3, using a fat-suppressed FLASH-3 D sequence. The knee was repositioned in between replicate acquisitions, 6 data sets being obtained in each case. After semiautomatic segmentation and three-dimensional reconstruction of the cartilage, the thickness was determined independent of the original section orientation. The coefficient of variation for repeated volume measurements and the deviations of the maximal cartilage thickness values were calculated subsequently. RESULTS: The mean variation of the cartilage volumes of the replicate measurements was 1.4% (+/- 0.8%) in the patella, 1.7% (+/- 1.5%) in the femur, 3.0% (+/- 1.2%) in the medial tibial plateau and 3.5% (+/- 2.0%) in the lateral tibial plateau. The comparison of the distribution patterns of cartilage thickness yielded a high degree of agreement. Only in rare cases deviations of more than 0.5 mm were observed. CONCLUSIONS: The results show that the presented method for determining the quantitative distribution of articular cartilage yields a high degree of precision. It offers new possibilities in screening risk groups, monitoring the course of degenerative joint disease and the investigation of functional adaptation of the cartilage to mechanical loading.

Adult↗
PubMed1997

Attenuation characteristics and application of gadolinium-DTPA in fast helical computed tomography.

RATIONALE AND OBJECTIVES: The computed tomography (CT) attenuation characteristics of gadolinium (Gd)-DTPA have been analyzed both in vitro and in vivo to evaluate the possibility of its substitution for iodine in patients with contraindications for iodine utilization. METHODS: In vitro attenuation values of Gd-DTPA were measured relative to those of iodine under variation of concentration, voltage, preattenuation, and beam hardening. In vivo iodine attenuation values were obtained for different injection rates (3.0 mL/second and 4.5 mL/second) to calculate the attenuation values of 0.5 molar Gd-DTPA to be expected in vivo by the help of the previously obtained attenuation-concentration curves. Subsequently, CT enhancement after an injection of 0.3 mmol/kg body weight Gd-DTPA was evaluated in five patients with contraindications for iodine administration. RESULTS: The injection of a 0.7 molar Gd-DTPA solution at a flow rate of 4.5 mL/second was calculated to be equivalent to that of 2.36 molar iodine at a flow rate of 3 mL/ second. Sufficient enhancement for diagnosis of dissections/ aneurysms of arterial vessels could be achieved. Both arterial and venous cervical or thoracic vessels could be enhanced to 100 Hounsfield units with a bolus injection. In contrast to the thyroid gland, the parenchyma of the liver and the kidney was not sufficiently enhanced. CONCLUSIONS: Gadolinium-DTPA is more effective than iodine in x-ray attenuation; however, its present concentration of 0.5 molar and permitted dose of 0.3 mmol/kg body weight are insufficient to provide parenchymal enhancement with CT. The visualization of arterial vessels appears possible with gadolinium enhanced CT but requires optimal timing and fast scanning capabilities.

Aortic Dissection↗
PubMed1997

Pathologic conditions in the small bowel: findings at fat-suppressed gadolinium-enhanced MR imaging with an optimized suspension of oral magnetic particles.

Depiction of small-bowel pathologic conditions was optimized with use of a negative luminal contrast agent, spectral fat suppression, and gadolinium enhancement in an excised gut phantom. The method was applied in nine patients in conjunction with standard enteroclysis examinations. Bulk susceptibility effects of oral magnetic particles were canceled with use of a diamagnetic methylcellulose suspension. In the ileum, fat suppression and contrast between bowel wall and lumen was judged good or excellent in eight and nine patients, respectively. In eight of nine patients, additional mesenteric findings were depicted.

Administration, Oral↗
PubMed1997

Functional MRI mapping of occipital and frontal cortical activity during voluntary and imagined saccades.

We investigated the activation of frontal and occipital cortical areas in 14 normal volunteers during voluntary saccades in light or dark and during imagined saccades using functional magnetic resonance imaging (FMRI) with electro-oculogram monitoring. Voluntary saccades in light or dark and imagined saccades led to a significant activation (p < 0.005) of the precentral and posterior medial frontal gyrus (frontal eye field). The medial part of the superior frontal gyrus (supplementary eye field) also showed significant activity during voluntary saccades in all subjects, but only in four subjects during imagined saccades. In addition to frontal activity we found an activated primary visual cortex during voluntary saccades, both in light and in dark. In contrast to executed saccades, imagined eye movements revealed to occipital response under either condition. Our FMRI study supports the concept of frontal eye fields during voluntary saccades and demonstrates that occipital areas are associated with the generation of voluntary eye movements. However, the primary visual cortex is not active when eye movement is only imagined.

Adult↗
PubMed1997

A phase-II study with idarubicin, ifosfamide and VP-16 (IIVP-16) in patients with refractory or relapsed aggressive and high grade non-Hodgkin's lymphoma.

We report a phase-II study of idarubicin, ifosphamide and etoposide (IIVP-16) in heavily pretreated patients with relapsed or refractory aggressive non-Hodgkin's lymphoma. The IIVP-16 regimen consisted of idarubicin (10 mg/m2 i.v. days 1 + 2 or days 1 + 8), ifosfamide (1000 mg/m2 i.v. days 1-5) and VP-16 (150 mg/m2 i.v. days 103). 40 patients were enrolled. Of 38 evaluable patients, 26 had centroblastic subtype, followed by lymphoblastic (6), immunoblastic (2), and other entities (4). 18 patients were primary resistant; 14 patients had early relapse (CR less than 12 months) and 8 patients late relapse (CR longer than 12 months). The median number of different prior chemotherapy regimens was 2 (range 1 to 6). 20 patients had received additional radiotherapy. The response-rate was 47.4% including 8 CR (21.1%) and 10 PR (26.3%). IIVP-16 was more effective in patients with relapsed disease when compared with patients with primary resistant disease (response rate 65% vs. 27.8%, p < 0.025). Leukopenia and thrombocytopenia were the major toxicities occurring in 73/107 (68.2%) and 57/107 (53.3%) of cycles (WHO grade IV). IIVP-16 is an effective regimen particularly in patients with unfavorable relapsed NHL.

Adult↗
PubMed1997

Hybrid rendering of multidimensional image data.

The most important rendering methods applied in medical imaging are surface and volume rendering techniques. Each approach has its own advantages and limitations: Fast surface-oriented methods are able to support real-time interaction and manipulation. The underlying representation, however, is dependent on intensive image processing to extract the object surfaces. In contrast, volume visualization is not necessarily based on extensive image processing and interpretation. No data reduction to geometric primitives, such as polygons, is required. Therefore, the process of volume rendering is currently not operating in real time. In order to provide the radiological diagnosis with additional information as well as to enable simulation and preoperative treatment planning we developed a new hybrid rendering method which combines the advantages of surface and volume presentation, and minimizes the limitations of these approaches. We developed a common data representation method for both techniques. A preprocessing module enables the construction of a data volume by interpolation as well as the calculation of object surfaces by semiautomatic image interpretation and surface construction. The hybrid rendering system is based on transparency and texture mapping features. It is embedded in a user-friendly open system which enables the support of new application fields such as virtual reality and stereolithography. The efficiency of our new method is described for 3-D subtraction angiography and the visualization of morpho-functional relationships.

Computer Graphics↗
PubMed1997

[A comparison of ultrafast computed tomography, magnetic resonance angiography and selective angiography for the detection of coronary bypass patency].

PURPOSE: Validation of ultrafast-CT and MR-angiography (MRA) in comparison with angiography for detection of early postsurgical arterial and venous coronary artery bypass graft (CABG) patency. METHODS: 21 patients with a total of 55 CABG (34 venous and 21 arterial) were studied with angiography, ultrafast-CT (EBT), and MRA. RESULTS: With EBT, patency of 43/45 angiographically patent CABG could be correctly assessed (sensitivity: 96%). With MRA 26 CABG (17 venous and 9 arterial) were identified as patent (sensitivity: 67%). It was not possible to quantify proximal stenosis of three grafts (> 40%) and to evaluate the distal bypass anastomosis with both EBT and MRA. CONCLUSIONS: Ultrafast-CT is a promising minimal invasive screening method for the evaluation of venous and arterial CABG patency. The diagnostic significance of MRA is remarkably reduced.

Aged↗
PubMed1997

The relations of regulation and emotionality to resiliency and competent social functioning in elementary school children.

The relations of regulation and emotionality to elementary school children's social functioning were examined. Teachers and peers reported on children's social functioning; 1 parent and teacher rated children on various measures of regulation, resiliency, and emotionality; and a behavioral index of regulation was obtained. The effects of individual differences in attentional regulation on social status and socially appropriate behavior were mediated by resiliency, and dispositional negative emotionality moderated the positive relation between attentional control and resiliency (with this path being stronger for children high in negative emotionality). The effects of behavioral regulation were not mediated by resiliency; however, the relation of behavioral regulation to socially appropriate behavior (but not social status) was moderated by negative emotionality, with effects being significant and higher for children high in negative emotionality.

Adaptation, Psychological↗
PubMed1996

Spirometrically controlled high resolution computed tomography - quantitative assessment of density distribution in patients with diffuse fibrosing alveolitis.

STUDY OBJECTIVE: Lung density assessed by high resolution computed tomography (HRCT) is sufficiently sensitive for the diagnosis of interstitial lung disease, but may be hampered by uneven disease distribution. We determined the mean and subpleural density values in patients with diffuse fibrosing alveolitis (FA) and evaluated the diagnostic accuracy of both parameters, expressed as post-test odds ratios. MATERIALS AND METHODS: Pulmonary HRCT was performed on 21 FA patients and compared to scans of 27 healthy volunteers. The HRCT procedure was standardized by taking 3 scans at the carina +/- 5 cm, and by defining inspiration levels at 50% vital capacity. Mean lung density (MLD) and subpleural lung density (SLD) were calculated for all participants. RESULTS: MLD and SLD values for healthy subjects were significantly higher compared with the patient group. Odds ratios were 7.8:1 and 3.9:1 for SLD and MLD, respectively, demonstrating a superior discrimination power of SLD in the diagnosis of FA. CONCLUSION: Diagnostic accuracy of quantitative HRCT measurements in FA was improved by the separate evaluation of subpleural lung density, which is a better indicator of the presence or absence of lung fibrosis than is mean lung density.

Adult↗
PubMed1996

Pallidal lesions. Structural and functional magnetic resonance imaging.

OBJECTIVE: To study noninvasively the functional anatomy and pathophysiologic characteristics of the globus pallidus external (GPe) and internal (GPi) divisions. DESIGN: Structural and functional neuroimaging using high-resolution magnetic resonance imaging. SETTING: University medical center research facility. SUBJECTS. Seven patients with pallidal lesions, 4 with an akinetic-rigid syndrome and 3 with a dystonic syndrome, and 15 age-matched volunteers. MAIN OUTCOME MEASURES: T2-weighted anatomical magnetic resonance imaging and number of activated voxels in the GP during rapid supination and pronation of the hand. RESULTS: T2-weighted images showed hyperintense bilateral lesions in the GP of all patients. Patients with dystonic syndromes had isolated lesions in the GPi. Patients with signs of akinetic-rigid syndromes showed abnormalities in the GPe or in central portions of the GP (GPc). Patients with lesions in both parts of the GP had akinetic-rigid or dystonic syndromes. All patients showed activation in the areas of the lesions. The number of activated voxels in the GP was significantly smaller (P < .005, Wilcoxon signed rank test) in patients than in control subjects. Activation of the GP was predominantly contralateral to the moving hand. CONCLUSIONS: Lesions in the GPi result in a loss of inhibitory pallidal projections to the thalamus, which may explain the hyperkinetic signs. Lesions in the GPe lead to an increased inhibition of the thalamus, which may explain the hypokinetic signs. Neuronal activation in lesion sites suggests the presence of remaining functionally vital tissue.

Aged↗
PubMed1996

Magnetic resonance chondro-crassometry (MR CCM): a method for accurate determination of articular cartilage thickness?

A method for the assessment of articular cartilage thickness based on MRI is presented and its accuracy and reproducibility tested. Six specimens of human patellae were imaged, using a fat-suppressed FLASH 3D sequence, and sectioned with a high-precision band saw. The regional distribution of articular cartilage thickness was determined from the MR images and from the anatomical sections (intervals of 0.5 mm). With image analysis 50-90% of the image points were found to lie within exactly the same thickness interval in corresponding patterns, and less than 17% deviated more than 0.5 mm. More than 85% of all pixels were reproducible with MRI after new positioning of the joint. No influence of the read-out direction and no important differences between areas of thin and thick cartilage could be detected. The authors conclude that MR chondro-crassometry can provide accurate and reproducible information on cartilage thickness.

Adult↗
PubMed1996

Determination of knee joint cartilage thickness using three-dimensional magnetic resonance chondro-crassometry (3D MR-CCM).

The objective of this article was to analyze the accuracy and precision with which the quantitative distribution of articular cartilage can be determined in the knee joint using MRI. A three-dimensional (3D) technique that accounts for the out-of-plane deviation of the interface normal in strongly curved joint surfaces (3D MR-CCM) has been developed for cartilage thickness measurements. Eight cadaveric knee-joint specimens and six volunteers were imaged using a fat-suppressed gradient-echo sequence at a resolution of 2 x 0.31 x 0.31 mm3. Cartilage volumes and topographical thickness maps were obtained and compared with those derived from anatomical sections by image analysis. The deviation of the MR volumes from those of the sections was 1-12%, the coefficient of variation after repositioning ranged from 2.9% (patella) to 8.2% (lateral tibial plateau). Between 60% and 80% of all image points could be attributed to identical thickness intervals, less than 20% deviating by more than 0.5 mm. The intraobserver and interobserver reproducibilities were very high in both the specimens and the volunteers. In the knee joint, 3D reconstructions of the cartilages, and measurements that take into account the out-of-plane deviation of the interface normals (3D MR-CCM), are required.

Adult↗
PubMed1996

Time-dependent changes of insufficiency fractures of the sacrum: intraosseous vacuum phenomenon as an early sign.

Sacral insufficiency fractures develop over a period of time and show time-dependent changes. We report on 15 CT examinations of 5 patients with early-stage insufficiency fractures of the sacrum. In 4 patients only irregular sclerosis without distinct fracture lines was present in 7 of 8 fractures. Of these 4 patients; 3 exhibited intraosseous gas inclusions in a ventral part of a lateral mass; 5 of 8 fractures disclosed a ventral cortical break. When distinct fracture lines had developed in 1 patient, intraosseous vacuum phenomenon had disappeared. Fracture lines evolve over weeks to months and show central bone absorption. The fractures can heal as demonstrated in 4 of 6 fractures in 3 patients, can persist over 1 year without significant changes or can progress to pseudoarthrosis with bone destruction similar to neuropathic joint disease. Intraosseous vacuum phenomena can persist to this stage. Intraosseous vacuum phenomenon is recognized as a potential finding in the early stage of sacral insufficiency fracture, which also is true for irregular sclerosis and ventral cortical disruption.

Follow-Up Studies↗
PubMed1996

Breathhold imaging of the upper abdomen using a circular polarized-array coil: comparison with standard body coil imaging.

Current studies emphasize the use of array coils to decrease noise and increase the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). We applied T1-weighted and T2-weighted standard nonbreathhold spin echo (SE) sequences and T1-weighted FLASH, TurboFLASH, T2-weighted spin-echo time (TSE), and heavily T2-weighted half Fourier acquisition single-shot TSE (HASTE) sequences during breathhold for abdominal imaging in 15 normal volunteers. The breathhold scans were performed using both a standard coil and a circular polarized array coil. We analyzed the signal intensity (SI), SNR, and CNR of abdominal organs in all sequences. SNRs increased in all cases by an overall factor of approximately 3 due to an 8% increase in overall SIs and a 50% decrease in noise when applying the array coil. Although the array-coil FLASH sequence performed at least as well as the respective SE sequence, the SNRs of the array-coil TurboFLASH, TSE breathhold, and HASTE sequences were generally lower. We conclude that array-coil imaging significantly improves fast imaging of the abdomen.

Abdomen↗