Search PubMed⌕ Search

Biomedical subjects

M Reiser

Publications and source records attributed to M Reiser.

At least 469 records · Page 26Linked to original sources
PubMed1995

[Magnetic resonance tomography in trauma of the knee joint].

Technical improvements of MRI have significantly improved the visualization of joints. New sequences and experience with MRI has lead to increased sensitivity and specificity of internal joint lesions. For the first time, contusions of the subchondral bone which are prognostically significant for the developing of chondral lesions can be identified. To date, no other tests are available to identify such lesions. This review article outlines the current value of MRI for evaluating post-traumatic knee joint injuries.

Bone Marrow↗
PubMed1995

[Turbo-spin-echo MR imaging of the brain at 0.5 T].

Turbo-spin-echo (TSE) imaging is a fast technique, which provides true spin-echo contrast in a definitely shorter scan time than conventional spin-echo (SE). Clinical studies at 1.5 T show that TSE is a valuable alternative to SE and will ultimately replace time-consuming T2-weighted SE imaging for examinations of the brain and brainstem. Besides the reduction of scan time, TSE is less sensitive to motion artefacts. A slight decrease of susceptibility effects of 1.5 T can be a disadvantage in the detection of old haemorrhagic lesions and calcifications. In these cases the gradient-echo sequence will remain the most sensitive. TSE allows a greater flexibility of examination strategies, including several orientations, strongly T2-weighted images and high spatial resolution (HR) MRI. HR MRI using thin slices (1-3 mm), a small field of view and a 512 image matrix yields detailed information about small anatomical regions (e.g. the pituitary fossa, cavernous sinus, internal auditory canal and brainstem) and permits the delineation of specific cranial nerves. In this study TSE was utilized at 0.5 T field strength in order to assess whether the advantages of TSE hold for midfield systems. Preliminary results in imaging of the brain and brainstem are very promising.

Adolescent↗
PubMed1995

[Knee joint cartilage in magnetic resonance tomography. MR chondrovolumetry (MR-CVM) using fat-suppressed FLASH 3D sequence].

UNLABELLED: The objective of this study was to optimize the demonstration of articular cartilage with magnetic resonance tomography (MRT) and to assess its accuracy in determining the articular cartilage volume of the knee joint. METHODS: A fat-suppressed FLASH-3D sequence was optimized on healthy volunteers. A fresh cardaveric knee joint was removed from a 82-year-old man and immediately imaged without being frozen or fixed. MRT was carried out at 1.5 T and 25 mT/m (Vision, Siemens, Erlangen, Germany) with a conventional CP knee coil. Sagittal and transverse sections were acquired perpendicular to the articular surfaces, and then, parallel to these imaging planes, anatomical sections were obtained with a diamond band saw. The volumes of the patellar, tibial and femoral cartilages were determined from both the images and the sections, using an image analysing system. RESULTS: Signal intensities and contrast-to-noise ratios depend on the parameters used. The highest contrast between the cartilage and the periarticular tissues was obtained at a flip angle of 30 degrees (TR = 60 ms, TE = 11 ms). However, a flip angle of 60 degrees was judged to provide optimal subjective image quality. Using these parameters, the deviations between the radiological and the anatomical cartilage volumes were -4.7% in the patella, -3.1% in the tibial plateau and -4.2% in the femur. CONCLUSIONS: The volumes of the knee-joint cartilages may be accurately determined with MRT if an appropriate pulse sequence is chosen. From a clinical point of view the differences between MR images and anatomical sections can be considered negligible. These differences may be explained on the basis that MRT delineates uncalcified cartilage only and that the calcified layer is demonstrated as part of the subchondral bone plate. However, close correlation of the thicknesses of the uncalcified and the calcified layer has been reported in the literature, so the relative distribution of articular cartilage should be accurately reflected in MR images.

Aged↗
PubMed1995

[Reducing radiation dosage with modern DSA equipment].

PURPOSE: In angiographic and interventional procedures the often long fluoroscopy times add a great deal to the total patient dose. The new Multistar T.O.P. (Siemens) is equipped with various features for dose reduction. In this study pulsed fluoroscopy was tested versus standard continuous fluoroscopy and supervisions. MATERIALS AND METHODS: Fluoroscopy with 3, 7.5, and 15 pulses/s in the Multistar T.O.P. were compared to standard fluoroscopy and to reduced-dose supervision in a human pelvic phantom. The skin entry dose and pelvic dose were continuously registered. RESULTS: The supervision mode used 58% of the dose used in continuous fluoroscopy. Pulsed fluoroscopy with 15 pulses/s required 54%, 7.5 pulses/s 27% and 3 pulses/s. These provide adequate image quality with only 10% of the standard dose. CONCLUSIONS: It was possible to save up to 90% of the fluoroscopy dose in interventions and angiographies when using the new pulsed fluoromodes available in the Multistar T.O.P.

Angiography, Digital Subtraction↗
PubMed1995

[Diagnosis of the site and extent of breast carcinoma].

The value of X-ray-mammography, ultrasound, and MRI are compared with regard to their results in localization, differential diagnosis, and staging of carcinomas of the breast. For microcalcifications that are only imaged by mammography, X-ray is superior to the other imaging modalities and remains method of choice. Ultrasound is the most useful to differentiate cystic and solid lesions. The value of MRI is not yet proved sufficiently except in conservative and plastic surgery of breast carcinoma.

Biopsy↗
PubMed1995

[Intra-arterial treatment of therapy-resistant residual tumors of the pelvis].

PURPOSE: Evaluation of intraarterial cancer treatment in recurrent pelvic tumors, which were resistent to other treatment modalities. PATIENTS AND METHODS: Ninety-seven patients suffering from pelvic recurrences originating from bladder (n = 40), rectum (n = 19), cervix (n = 21) oder other organs (n = 17) were treated by intraarterial chemotherapy (111 times) or transcatheter embolisation (52 times). RESULTS: Less than 20% of our patients had remission of the tumor burden but tumor symptoms (especially pain and bleeding) could be controlled in 35 to 87% of the patients. The main complication was a muscle necrosis after intraarterial chemotherapy because of recurrent bladder cancer. CONCLUSION: Intraarterial cancertherapy is a useful procedure for symptomatic treatment of tumor symptoms especially in case of bleeding. Local tumor control can only be achived in a minority of the patients.

Adult↗
PubMed1995

[Quantitative computerized tomography of the lung--respiration controlled diagnosis of diffuse lung diseases].

STUDY OBJECTIVE: Computed tomography provides measurements of lung attenuation which reflect changes in the air to tissue ratio and can thereby be employed for diagnosis of diffuse lung disease. In this prospective study, we quantitatively analyzed lung density by high resolution computed tomography (HRCT) in 26 healthy volunteers, 15 patients with chronic obstructive pulmonary disease (COPD), and 15 patients with idiopathic lung fibrosis (IPF). The procedure was standardized by examination of 3 scans at the carina +/- 5 cm and by defining inflation levels by %VC using an on-line hand held spirometer. RESULTS: Performance of HRCT at 50% VC provides not only significant and distinguishable group data, but is the easiest to carry out for dyspneic patients. The mean lung density at 50% VC for healthy subjects was -820 +/- 4.2 (mean +/- SEM) Hounsfield units (HU). It was significantly lower (p < 0.01) in COPD patients (-865 +/- 9.2 HU), and considerably higher (-697 +/- 17.8 HU, p < 0.001) in the IPF group. At an inflation level of 20% VC, mean lung density values were similarly distributed, at significantly lower values relative to those at 50% VC, but the procedure was more difficult to perform for patients with dyspnea. In contrast, at 80% VC, lung density values for the COPD and control groups were not significantly different (p = 0.08). The sensitivity to detect COPD was improved by selecting HRCT values lower than -900 HU, which represent the part of the lung with an increased air/tissue ratio. For IPF patients an increase of lung density values above -699 HU was characteristic, indicating a decrease of the air/tissue relationship. CONCLUSION: From our data we propose to perform quantitative HRCT measurements at 50% VC. Diagnosis of diffuse lung disease can be further improved by consideration of specific CT -value intervals. Spirometrically controlled quantitative HRCT is a clinically meaningful tool for the assessment of diffuse parenchymal lung disease.

Adult↗
PubMed1995

[Echo-planar imaging of the brain].

In this review, the clinical utility of echoplanar techniques in MRI of the brain is discussed. Comparison of high-resolution EPI with SE/turbo-SE shows high image quality of EPI in the supratentorial brain. In the infratentorial region, however, susceptibility artifacts limit image quality. For the assessment of neuronal brain activation utilizing the intrinsic contrast of blood (BOLD), EPI has definite advantages over other techniques of functional MRI. Due to its superior temporal resolution and multislice capabilities, EPI allows for analysis of complex neuronal activation patterns. Diffusion imaging benefits from the lack of bulk motion artifacts and serves primarily to detect early stroke. Three methods of perfusion imaging (rel. blood volume, rel. blood flow) are discussed: the susceptibility artifact method (T2*), the relaxitivity method (T1), and the signal-labelling technique (STAR). Perfusion imaging may have a clinical impact in the assessment of brain tumors and cerebral ischemia.

Artifacts↗
PubMed1995

[Phased-array superficial coil and breath holding technique in MRI of the liver. Comparison of conventional spin echo sequences with rapid fat suppressing gradient echo and turbo-spin sequences].

PURPOSE: To determine the efficacy of fast MRI techniques using a tailored imaging design (breathhold and array-surface coil), conventional T1-, T2-weighted spin-echo (SE) sequences and breathhold gradient-echo (GRE) T1- and breathhold fast SE T2-weighted images were compared. METHODS: 20 patients with proven focal liver lesions were studied on a 1.5 Tesla system. Conventional SE T1- and T2-weighted imaging, as well as GRE T1- and fast SE T2-weighted imaging was performed. Fast imaging was done during breathhold using an array-surface coil. For all sequences signal-to-noise ratios (S/N) and liver-to-lesion-contrast ratios (L/L) were measured and statistically compared. In addition, two blinded readers qualitatively evaluated all images, using a score system regarding artifacts (breathing, pulsation), number of lesions, and over-all image quality. RESULTS: Regarding image quality parameters, S/N and L/L, there was no significant (p > 0.05) difference between the conventional and fast imaging techniques. However, GRE imaging was superior (84.8%) to conventional imaging for breathing and pulsation artifacts, while fast SE T2 imaging was equal regarding breathing artifacts, but superior (51.5%) regarding pulsation artifacts. The number of detected hepatic lesions was identical in all sequences. CONCLUSION: The fast MRI techniques demonstrated a superiority to conventional imaging regarding image quality and presence of artifacts. Therefore, fast imaging techniques can replace conventional techniques, at least in patients that can sufficiently sustain breathing.

Artifacts↗
PubMed1995

[Fast and ultra-fast sequences in MRI of the pelvis and retroperitoneum].

Fast and ultrafast sequences are crucial prerequisite for optimum diagnostic impact in magnetic resonance (MR) imaging of the pelvis and retroperitoneum. In MR imaging of the pelvis, heavily T2-weighted fast turbo spin echo (TSE) sequences with acquisition times of 2-4 min have widely replaced time-consuming conventional T2-weighted SE sequences due to substantial time savings and better image quality. Fast and ultrafast gradient recalled echo (GRE) sequences are the basis of dynamic contrast-enhanced studies. In MR imaging of the retroperitoneum, fast and ultrafast sequences currently play the most important role as they allow for breath-hold acquisition of a sufficient number of images free of motion artifacts. The current roles of TSE, tubo gradient spin echo (TGSE), GRE and echoplanar imaging (EPI) sequences in MR imaging of the pelvis and retroperitoneum is discussed.

Artifacts↗
PubMed1995

[Use of ultra-fast computerized tomography in diagnosis of coronary heart disease].

Ultrafast or electron beam tomography (EBT) permits acquisition of images in 50-100 ms. An artifact-reduced display of heart and vessel structures as well as calcifications can be achieved. Therefore, EBT can be used for the detection and quantification of coronary artery calcification. Thirty-two patients with known coronary artery disease (CAD) were studied by EBT with and without i.v. contrast enhancement and with conventional coronary angiography. Different scoring systems were applied in order to define the basis to compare the data. The results showed a high EBT sensitivity for detection of coronary artery stenosis of up to 94% but low specificity with a maximum of 75%, depending on the scoring system applied. With EBT, differentiation between significant CAD (> 75%) and low-grade CAD (0-75%) showed significant results. The scoring system is not yet completely satisfactory, and with the integration of other screening tests and continuous development of scoring systems, the significance and reliability of this method in evaluation of CAD are expected to increase.

Aged↗
PubMed1994

Magnetization transfer contrast (MTC) and MTC-subtraction: enhancement of cartilage lesions and intracartilaginous degeneration in vitro.

Human articular cartilage from 16 cadaveric or amputated knees was studied using standard magnetic resonance imaging (MRI), on-resonance magnetization transfer contrast (MTC) and MTC-subtraction MRI. Results were compared with subsequent macroscopic and histopathological findings. MTC-subtraction and T2-weighted spin-echo images visualized cartilaginous surface defects with high sensitivity and specificity. MTC and T2-weighted spin-echo images revealed intra-cartilaginous signal loss without surface defects in 80% of the cases, corresponding to an increased collagen concentration. It is concluded that MTC is sensitive to early cartilage degeneration and MTC-subtraction can be helpful in detecting cartilage defects.

Adult↗
PubMed1994

The morphology of articular cartilage assessed by magnetic resonance imaging (MRI). Reproducibility and anatomical correlation.

Quantitative assessment of cartilage volume and thickness in a formalin-alcohol fixed specimen of a human patella was conducted with magnetic resonance imaging (MRI), as it is still unclear whether the morphology of normal and damaged cartilage can be accurately demonstrated with this technique. MR imaging was carried out at 1.0 T (section thickness 2 mm, in-plane-resolution 0.39-0.58 mm) with the following pulse sequences: 1) T1-weighted spin-echo, 2) 3D-MPRAGE, 3) 3D-FISP, 4) 3D-MTC-FISP, 5) 3D-DESS, 6) 3D-FLASH. Following imaging, the patella was sectioned perpendicular to the articular surface at intervals of 2 mm with a diamond band-saw. The volume of its cartilage was determined from the anatomical sections and the MR images, using a Vidas IPS 10 image analysing system (Kontron). Measurements were carried out with and without the low-signal layer in the transitional zone between the articular cartilage and the subchondral bone. If the low-signal layer was included, the volume was overestimated with MRI by 16 to 19%. Without the low-signal layer the volumes were less than those determined from the anatomical sections: T1-SE-18.2%, MPRAGE -22.6%, FISP -17.1%, MTC-FISP -9.5%, DESS -9.3% and FLASH -6.1%. The coefficient of variation for a 6-fold determination of the volume amounted to between 6.2% (T1-SE) and 2.6% (FLASH). The FLASH sequence allowed the most valid and reproducible assessment of the cartilage morphology. The remaining difference from the real volume of the cartilage may be due to the fact that the calcified zone of the cartilage is not delineated by MRI.

Aged↗
PubMed1994

Musculoskeletal MR imaging: turbo (fast) spin-echo versus conventional spin-echo and gradient-echo imaging at 0.5 tesla.

The value of T2-weighted fast spin-echo imaging of the musculoskeletal system was assessed in 22 patients with various neoplastic, inflammatory, and traumatic disorders. Images were acquired with high echo number (i.e., echo train length) fast spin-echo (FSE; TR 2000 ms, effective TE 100 ms, echo number 13, linear k-space ordering), conventional spin-echo (SE; TR 2000 ms, TE 100 ms) and gradient-echo (GRE) sequences (TR 600 ms, TE 34 ms, flip angle 25 degrees). Signal intensities, signal-to-noise ratios, contrast, contrast-to-noise ratios, lesion conspicuousness, detail perceptibility, and sensitivity towards image artifacts were compared. The high signal intensity of fat on FSE images resulted in a slightly inferior lesion-to-fat contrast on FSE images. However, on the basis of lesion conspicuity, FSE is able to replace time-consuming conventional T2-weighted SE imaging in musculoskeletal MRI. In contrast, GRE images frequently showed superior lesion conspicuity. One minor disadvantage of FSE in our study was the frequent deterioration of image quality by blurring, black band, and rippling artifacts. Some of these artifacts, however, can be prevented using short echo trains and/or short echo spacings.

Adolescent↗
PubMed1994

Intracerebroventricular but not intraperitoneal administration of aluminum attenuates vasopressin-enhanced retrieval of a passive avoidance task in rats.

We studied the influence of single intracerebroventricular (ICV) and intraperitoneal (IP) injections of the neurotoxin aluminum on the retrieval of a passive avoidance task in rats and on the vasopressin-evoked improvement of the recall of the task. It was found that ICV administration of the metal alone strongly decreases the retention time of a passive avoidance task, whereas IP application of aluminum prolongs it. Vasopressin given ICV and IP leads to an enhancement of retrieval (prolongation of the retention time). Vasopressin in combination with aluminum does not improve the recall of the task when both substances are given ICV. Intraperitoneal injection of the neuropeptide together with the metal improves the recall of the task. Our data point to the crucial importance of the route of application of aluminum for behavioral studies.

Aluminum↗