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Biomedical subjects

M Reiser

Publications and source records attributed to M Reiser.

At least 505 records · Page 28Linked to original sources
PubMed1994

[Patient monitoring and safety aspects in magnetic resonance imaging examinations].

With the continuously growing number of MRI examinations and the enormously rapid application of new technical developments, patient monitoring and safety aspects become an increasingly important issue. The vendors of MRI systems and the legislation tend to underestimate and ignore these problems. Therefore the institutions which operate MRI units have to find solutions by their own initiative. Not only due to forensic reasons a monitoring concept should be developed with suitable equipment and careful documentation in any institution operating an MRI unit. This article discusses the planning, implementation and conduct of adequate patient monitoring during MRI examinations.

Adult↗
PubMed1994

[Ct-portography in diffuse liver steatosis. Potential for a false-negative assessment].

CT portography is the most sensitive technique currently available for the preoperative diagnosis of liver metastases. We report on a patient with liver steatosis in whom ultrasound examination revealed two liver metastases in the follow up after resection of a papillary carcinoma. The liver metastases could be clearly identified both on plain CT and on enhanced CT with dynamic bolus contrast medium injection. Because of the small difference in attenuation values between liver parenchyma and metastases the two liver metastases had not been recognized on CT portography. When severe and diffuse liver steatosis is present CT portography may fail to detect metastases or small hepatocellular carcinoma.

Adult↗
PubMed1994

Biocompatibility studies of the single-needle technique in plateletpheresis with the Fresenius AS 104 blood cell separator.

To investigate the biocompatibility of the single-needle technique of the Fresenius AS 104 blood cell separator we analyzed coagulation, complement and hemolysis parameters prior to, during and after five thrombocytaphereses. The data were compared with results of the same parameters from identical donors in the dual-needle procedure. The analysis of bilirubin, lactate dehydrogenase, hydroxybutyrate dehydrogenase and haptoglobin showed no relevant hemolysis. However, changes of the concentrations of coagulation factors XII and XI indicated an activation of coagulation. This was confirmed by an increase of the thrombin-antithrombin III complex during apheresis. No significant change in the complement split product content of the samples obtained during apheresis was found. Complement factors, glucose, lactate, leukocytes, morphology score and thrombocytes were measured in platelet concentrates. The comparison of the platelet products showed no significant differences except for leukocyte contamination. Glucose and lactate concentrations were similar in both procedures. Levels of complement activation markers were not statistically different.

Bilirubin↗
PubMed1993

[Modern diagnostics of the breast].

A diagnosis of breast cancer as early as possible is most important for a good prognosis. Among previous imaging modalities (mammography, sonography, DSA, thermography, CT) only mammography was able to prove a significant reduction of mortality, but unfortunately only for women above 50 years of age. Magnetic resonance mammography (MRM) is under technical and clinical evaluation for more than 8 years. Special surface coils and a variety of measurement sequences have been tested. By using "dynamic MRM", i.e., the repetitive imaging of the same slices before and at short time intervals after the injection of contrast medium, a high sensitivity (97.3%) and specificity (96.9%) was found in detecting breast cancers of different histology. In this study especially clinically or mammographically difficult cases were included in order to test the efficacy of dynamic MRM. Breast cancer can be proven or excluded with a very high degree of confidence. Conventional mammography had been yielding a vast number of false positive findings. With MRM, therefore, the number of biopsies can be substantially reduced. The remarkable uniformity of the maximum rate of signal enhancement in carcinomas may be explained by the changed vascularisation of malignant tumours based on early tumour angiogenesis. This change in vascularisation can be detected by combining the use of contrast medium with a high contrast sensitive measurement technique. This method seems to be much more reliable than mammographic or sonographic procedures. MRM needs further technical improvements. Since breast cancer is still the most frequent cause of cancer in women in the Western hemisphere, MRM should be used in all cases where is a discrepancy among radiographic, sonographic or clinical findings. However, MRM examinations should be performed only by experienced examiners, since a variety of pitfalls must be avoided.

Adenofibroma↗
PubMed1993

[Rheumatoid arthritis of the wrist. Dynamic Gd-DTPA enhanced MRT].

21 patients with rheumatoid arthritis of the wrist diagnosed according to the criteria of the American Rheumatism Association were examined by dynamic MRT before and after the i.v. injection of Gd-DTPA (0.1 mmol/kg). The results were correlated with the clinical and radiological findings. The increased signal intensity of the pannus was 1.17 +/- 0.45%/sec and this differed significantly (p < 0.001) from bone marrow (0.16 +/- 0.11%/sec) and from muscle (0.25 +/- 0.16%/sec). Blood sedimentation rate correlated with the gradient of synovial proliferation (p < 0.05). There were no further statistically significant correlations between the clinical, radiological and MRT findings and the change in signal intensity from synovial proliferation as shown by dynamic MRT.

Adult↗
PubMed1993

[Turbo(fast) spin echo at 0.5 T: effect of echo distance and echo number on image contrast].

Signal intensities, signal-to-noise ratios (S/N), and contrast-to-noise ratios (C/N) in dependence on the echo distance and echo number of the new turbo (fast) spin-echo technique are analysed by phantom, volunteer and patient measurements. With increasing echo number (3 to 15 echoes), signal intensities increase (25 to 50%), S/N varies between different tissues, and C/N of fat to water decreases (70%). A high echo number, although it shortens the imaging time, is thus not always the best choice since the fat/water contrast is lost. However, a high fat/water contrast is advantageous for several MR applications.

Arthritis, Rheumatoid↗
PubMed1993

[Magnetic resonance tomography with fast spin-echo sequences--the results in the ENT area].

UNLABELLED: The use of T2-weighted spin-echo sequences is mandatory for identifying tumours in the ENT region and for differential diagnosis of pathological findings. A highly promising alternative to time-consuming conventional SE sequences is now available in the fast-spin-echo sequences (FSE). FSE was compared with the conventional SE (CSE) basing on 100 assessments of examinations of 20 patients. RESULTS: Conventional SE = TR/TE = 1800/90 ms with one average (NEX), FSE = TR/TE = 3200/120 ms with 4 averages (NEX). Measurement time CSE 6:59 min, FSE 3:12 min. Analysis was performed in analogy to on ROC analysis by 5 radiologists as a blind study. The anatomic differentiation and contrast performance were compared as well as the differentiation and definition of lesion and lymphatic node and a subjective overall assessment. Differentiation of pathological findings was the same with both sequences. FSE was superior to CSE in the visualisation of normal tissue, lymph nodes and also in the subjective overall assessment. The following criteria were employed in the subjective overall valuation: sum total of impressions gathered from contrast behaviour or performance, susceptibility to artifacts, and signal-to-noise ratio. Due to the definitely improved parameters of image quality and the markedly reduced scanning time--which is reduced to 50%--FSE will replace the conventional spin-echo sequence in routine diagnostics.

Artifacts↗
PubMed1993

[Differentiating between tumor and implant material in the postoperative sella using MRT].

MRT criteria have been developed to distinguish between tumour and implant material following examination of 50 patients who had transsphenoidal hypophysectomies for tumours. Judgements were based on the postoperative hormonal status and the operation notes. Following contrast injection of Gd-DTPA and using T1 weighted spin-echo sequences, implant material appeared as sandwich-like, linear or circular structures. Residual recurrent tumour produced homogenous or non-homogenous aspects without marginal enhancement in 84% of cases. Postoperative displacement of the infundibulum to the opposite side was observed in 73% of patients with tumour remnants. Sensitivity of MRT was 70%, specificity 95%. There was a positive predictive value of 94% and a negative predictive value of 72% with an accuracy of 81%. This provides assistance in differentiating between tumour remnants and implant material. MRT is recommended as a method of examination for hypophyseal tumours to evaluate the success of surgery and where there is clinical doubt concerning residual or recurrent tumour.

Adenoma↗
PubMed1993

[Initial results of in vivo 31P-NMR spectroscopy of the spleen in patients with splenomegaly].

In-vivo 31P-NMR spectroscopy of the spleen was carried out in 15 patients with splenomegaly from various causes (Hodgkin's disease, non-Hodgkin lymphoma, polycythaemia vera, chronic lymphatic leukaemia, chronic myeloid leukaemia). Volume selection was with the ISIS technique, voxel size was between 3 x 5 x 5 and 8 x 6 x 7 cm3. There was a markedly elevated (PM+Pi)/beta-NTP quotient (mean 3.41 with a standard deviation of 0.37) (p < 0.001) and raised PDE/beta/NTP quotient as compared with 8 normals, who showed an (PME+Pi)/beta-NTP quotient of 2.32 and a PDE/beta/NTP quotient of 1.11. These raised quotients were interpreted as indicating increased membrane phospholipid metabolism due to increased cell turnover. The data suggest there may be some clinical value in performing 31P-NMR spectroscopy for defining splenic involvement in myeloproliferative diseases but further confirmatory studies will be necessary.

Adult↗
PubMed1993

[Magnetic resonance tomography using the fast STIR technique: optimization and a comparison with other sequences in a 0.5-Tesla system].

One disadvantage of the STIR sequence in MRI is its long acquisition time. A TR shortening for acceleration requires shortening of the inversion time depending upon the field strength. We optimized this "fast-STIR" technique at 0.5 T using calculations, phantom, volunteer, and patient measurements. This optimization procedure is transferable to other field strengths. The resulting sequence takes 4.5 minutes, fat is visualised signal-free. In the second part of our study we compared quantitatively and qualitatively the signal intensities, contrast, and sensitivity towards artifacts of this sequence with that of conventional SE and GRE sequences in 21 patients with neoplastic, inflammatory and traumatic disorders of the musculoskeletal system. The fast-STIR sequence showed similar or better lesion contrast as SE in 100% and as GRE in 88%. Decreased spatial resolution and higher sensitivity towards pulsatile artifacts of the fast-STIR sequence were only minor drawbacks.

Achilles Tendon↗
PubMed1993

[Metabolic studies of the calf musculature with 31P-MR spectroscopy in arterial obstructive disease before and after lumbar sympatholysis].

In 9 patients with arterial occlusive disease of grade IV according to Fontaine, energy metabolism was measured in the calf muscle during rest, before and after lumbar sympatholysis, by means of 31phosphorus MR spectroscopy. The concentration of inorganic phosphate (Pi) and phosphocreatine (PCr) relative to high energy phosphates, as well as the pH value in muscle cells were assessed, and the quotient Pi/PCr was calculated for estimation of energy reserves. Before sympatholysis, normal concentrations of the energy suppliers ATP and PCr were unexpectedly found in combination with reduced cellular energy reserves. After lumbar sympatholysis, in most cases no significant changes of muscle energy metabolism were detected. Independent of the muscle energy supply, a slight increase in energy supply without returning to normal values was found in only three patients. In most patients the clinical symptoms had improved at least to some extent.

Adult↗
PubMed1993

Triple-dose versus standard-dose gadopentetate dimeglumine: a randomized study in 199 patients.

To investigate the safety, patient tolerance, and efficacy with 0.3 mmol/kg gadopentetate dimeglumine in magnetic resonance (MR) imaging of the central nervous system (CNS), a phase 3 trial was conducted in 199 patients with suspected CNS lesions. Patients received either 0.1 or 0.3 mmol/kg gadopentate dimeglumine (injection time, 15 seconds and 45 seconds, respectively). T1- and T2-weighted spin-echo sequences were performed at either 0.5 T or 1.5 T. In 80 patients with enhancing brain lesions, contrast-to-noise ratios (C/Ns) were calculated, and lesion-to-brain contrast was evaluated visually. Six patients (6%) in each dose group reported adverse events. Eight adverse events occurred with 0.1 mmol/kg and seven with 0.3 mmol/kg. Vital signs and laboratory values did not change significantly. C/N (P < .05) and visual assessment ratings were higher with 0.3 mmol/kg than with 0.1 mmol/kg. According to these preliminary results, 0.3 mmol/kg gadopentetate dimeglumine is safe and well tolerated when administered at approximately 1 mL/sec.

Adult↗
PubMed1993

Cardiac abnormalities: assessment with T2-weighted turbo spin-echo MR imaging with electrocardiogram gating at 0.5 T.

PURPOSE: To evaluate the cardiovascular system with magnetic resonance (MR) imaging performed with the turbo spin-echo (TSE) method and electrocardiogram (ECG) gating. MATERIALS AND METHODS: ECG-gated T2-weighted TSE images were obtained in 52 patients with 68 pathologic conditions (intracardiac [n = 18], myocardial [n = 23], pericardial [n = 6], paracardial [n = 10], or aortic [n = 11] disease) and 10 healthy subjects. In healthy subjects, TSE parameters were tested and optimized, and signal-to-noise ratios (S/Ns) and contrast-to-noise ratios (C/Ns) were determined. Delineation of the endo-, epi-, and pericardial borders and signal intensity characteristics of myocardium, fat, pericardium, blood flow, tumors, and clots were assessed. RESULTS: The TSE method provided good-quality T2-weighted images with sharp edge definition in a short imaging time. Increasing the turbo factor reduced motion artifacts and preserved the S/N and C/N. TSE images also helped in diagnosis of tumors, pleural effusions, inflammatory changes, and intravascular clots. CONCLUSION: TSE MR imaging is a feasible alternative to time-consuming conventional SE MR imaging, reduces motion artifact, and may help in evaluation of the cardiovascular system.

Adipose Tissue↗
PubMed1993

Expression levels of the thyrotropin receptor gene in autoimmune thyroid disease: coregulation with parameters of thyroid function and inverse relation to major histocompatibility complex classes I and II.

Using a human TSH receptor (TSH-R) cDNA probe, we investigated TSH-R transcript levels in 13 human thyroid fragments by Northern blot analysis; 7 Graves' disease, 2 Hashimoto's disease, 3 endemic goiter, and 1 healthy thyroid gland were studied. TSH-R expression levels were variable, but displayed a close correlation to the expression of thyroid peroxidase (r = 0.703; P < 0.05), thyroglobulin (r = 0.817; P < 0.01), and the nuclear oncogene c-fos (r = 0.935; P < 0.001), but not c-myc. Overall, TSH-R transcript levels were low or absent in those thyroids in which expression of the major histocompatibility complex class I or II (MHC I or II) was high, thus establishing an inverse relation (MHC I, r = -0.791; P < 0.01; MHC II, r = -0.784; P < 0.01). In situ hybridization showed that apart from lymphocytes, thyroid cells themselves were the source of MHC II transcripts. gamma-Interferon expression was only detectable in 1 Hashimoto's goiter. Our findings suggest that next to lymphocyte infiltration, active regulatory events in the thyrocyte are responsible for the inverse relation between functional parameters (TSH-R, thyroid peroxidase, thyroglobulin, and c-fos) and immunological markers (MHC I and II).

Adolescent↗