Muscle magnetic resonance imaging shows distinct diagnostic patterns in Welander and tibial muscular dystrophy.

OBJECTIVES: This is a report on a retrospective muscle magnetic resonance imaging (MRI) study on 11 patients affected by Welander distal myopathy (WDM) and 22 patients with tibial muscular dystrophy (TMD) carried out in order to define the pattern and characteristics of muscle involvement. RESULTS: WDM patients showed involvement of gastrocnemius, soleus, tibial anterior (TA) and extensor digitorum longus (EDL), as well as hamstrings and hip adductor muscles. TMD patients showed involvement of the TA and EDL muscles, and in some patients also hamstring and posterior compartment muscles of the legs. Some patients showed asymmetry of muscle involvement. CONCLUSION: We conclude that muscle MRI examination proved to be very useful in the determination of the exact pattern of muscle involvement in WDM and TMD. Clinical testing using the Medical Research Council scale is not sensitive enough to establish the pattern of muscle involvement in focal muscle diseases.

191Os/191mIr-generator for studying arterial blood flow in experimental animal models.

Iridium-191m (191mIr, t1/2 = 4.96 sec), an ultra-short lived tracer, has turned out to be suitable for gamma imaging. It can be obtained in high yields from an 191Os/191mIr-generator with a low 191Os breakthrough. In this study the blood flow in the carotid and kidney arteries was studied in rabbits by radionuclide arteriograms. In addition, the whole body retention and biodistribution of 191Os was studied in rats. 191mIr was obtained from an activated carbon system, in a modification of the procedure described in the literature. The kidney regions (study I) of rabbits were imaged dynamically (5 frames/second) for up to 40 seconds, and the investigations were repeated 4-7 times in the same animal. Similarly, the carotid arteries were studied (study II) and from the curves flow parameters were calculated. In order to study the 191Os breakthrough two groups of rats (n = 5) were sacrificed one day and four days after injecting five diagnostic doses into the tail vein (study III). In study III the Os-retention was highest in the kidneys and spleen, followed by the muscles and liver: 0.11-0.12% ID/g tissues were obtained at 1 day and 0.10-0.13% ID/g at 4 days, respectively. These values indicate that the breakthrough values are by no means toxic and that investigations can be repeated immediately with a negligible radiation exposure. The investigations performed with the same animals (I-II) could be easily repeated and were reproducible. All of this indicates that 191mIr is suitable for radionuclide angiography and the generator system is simple and safe to use (191Os is beta-emitter).(ABSTRACT TRUNCATED AT 250 WORDS)

T1 rho dispersion imaging of diseased muscle tissue.

T1 rho dispersion, or the frequency dependence of T1 relaxation in the rotating frame, was used for in vivo muscle tissue characterization in 13 patients with primary skeletal muscle disease and in eight normal subjects for comparison. T1 rho dispersion measurements represent a new approach to magnetic resonance tissue characterization, possibly reflecting the macromolecular constituents of tissue. A definite, statistically significant, difference was found between the relative T1 rho dispersion values of normal and diseased muscle tissue. T1 rho dispersion measurements and images may increase the accuracy of identification of diseased muscles. Early identification of affected muscles is important for accurate diagnosis by muscle biopsy.

The effect of digital unsharp-mask filtering on the signal-to-noise ratio in computed radiography.

The effect of image processing in computed radiography (CR) has been analyzed in many ROC studies. The results have not shown great diagnostic improvements, except in some special occasions. The theoretical effect of image enhancement on the signal-to-noise ratio in CR images has so far not been assessed. Concerning the previous results, the changes induced in the signal-to-noise ratio by digital image processing are certainly of interest. We calculated the signal-to-noise ratio in various conditions according to the principles of the Rose model, using the computerized image data of storage phosphor radiography. Seventy-seven computed radiographs processed by Gaussian unsharp-mask filtering using different kernel widths were analyzed. The signal-to-noise ratio was reduced in all images by more than 40% when the smallest kernels were used, and increased slowly towards the original value with greater kernel sizes. In no conditions did the ratio exceed the original one. The results show that although edges and signal contrast can be enhanced by unsharp-mask filtering, this happens at the cost of increased noise. This might at least in part explain why image processing does not significantly improve the diagnostic information content of a computed radiograph.

The effect of scatter reduction on the signal-to-noise ratio in computed radiography.

Signal-to-noise ratio (SNR) in computed radiography (CR) was assessed by using the computerized image data from storage phosphor radiographs in a modification of the Rose model. A multiple pencil-beam (MPB) imaging device, a conventional 1:12 grid, and an air gap of 90 cm were compared in terms of improvement of the signal-to-noise ratio caused by the reduction of scatter. The MPB device showed better SNRs by a factor of 1.25 compared to the grid and air gap which were approximately equal to each other. This is related to its superiority in scatter control, which has also been shown previously. Air gap screening has not been very popular because of geometrical problems, but in scatter reduction it is still comparable to today's grid technology. The optimization of image information content in CR is briefly discussed.

Acute rhabdomyolysis: evaluation with magnetic resonance imaging compared with computed tomography and ultrasonography.

Fifteen patients with acute rhabdomyolysis were evaluated with low field magnetic resonance (MR) imaging and the results compared with those obtained using computed tomography (CT) and ultrasonography (US). With MR imaging, abnormal muscles with areas of increased signal intensity were seen in every patient, which probably reflects increased water content or increased mobility of water molecules caused by inflammatory reaction and oedema in the injured and necrotic muscles. Computed tomography without intravenous contrast medium demonstrated abnormal muscles in most patients examined with this modality. The CT findings consisted of areas of focal hypodensity in muscles. With US, abnormal muscles were seen in less than half of the patients studied. The normal structure of striated muscle was focally disturbed and areas of both decreased and increased echogenicity were found. Magnetic resonance imaging had a higher sensitivity in the detection of abnormal muscles than CT or US (100%, 62% and 42%, respectively). The findings of all these modalities are non-specific, but together with the clinical and laboratory data they confirm the diagnosis of rhabdomyolysis. The information gained from imaging studies is useful in the assessment of the extent and distribution of rhabdomyolysis. The precise identification of affected muscle compartments by MR imaging is valuable when surgical fasciotomy is considered for treatment; the procedure can then be appropriately directed to the compartments with clearly abnormal muscles.

Improvement of x-ray intensifying screen efficiency by special design of the screen.

An investigation of light diffusion in x-ray intensifying screens and the prospects for improvement by confining light spread with a special structure are reported. Light diffusion in CaWO4 screens was studied theoretically using computer simulation. The proportion and spatial distribution of light emerging from different depths in the screen were calculated. The introduction of narrow gaps in the screens made it possible to improve these proportions and distributions. The gaps improved the line spread functions, the screen efficiencies, and the average contribution of the absorbed quanta to the light output.