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Capillaries are the most basic and important blood vessel of the circulatory systems. The evaluation of the blood flow may contribute to many studies in future. We evaluated the capillary blood flow change of lower limb muscle over time before and after the exercise used by magnetic resonance imaging-intravoxel incoherent motion (MRI-IVIM) obtained perfusion information. Furthermore, we examined an association between the muscle pain after the exercise and the diffusion weighted image (DWI) indexes. DWI was imaged using multi-b values for a thigh and calf muscles. MRI was performed just after an exercise test, 3, 6, and 24 hours later, and the IVIM index and diffusion index were calculated. Furthermore, we interviewed the degree of the muscle ache 24 hours later. As a result, pseudo diffusion coefficient (D*) and f value as IVIM index increased after-exercise as compared with pre-exercise and decreased in 3 hours later. A similar tendency was found in the apparent diffusion coefficient and the diffusion coefficient as diffusion index. Furthermore, all indexes increased in after exercise from before exercise and decreased with time passed and increased again 24 hours later. In conclusion, IVIM could obtain capillary blood flow information, and it was suggested to contribute for sports medicine in future.

SummaryApparent diffusion coefficient (ADC) values calculated from diffusion-weighted magnetic resonance imaging (DW-MRI) can be used for differentiation of tumors. Clinically, ADC values are used for monitoring treatment response after chemotherapy or radiation. However, it is reported that the threshold of the ADC value differs among institutions. In addition, there are reports regarding the change factor of the ADC value. Slice thickness may induce error in the ADC value by the influence of the partial volume effect in thicker objects, and by the influence of signal-to-noise ratio (SNR) in thinner objects. Therefore, in this study, the effect of slice thickness was examined. The signal body of spherical high-diffusion coefficients of 6, 7.9, and 9.3 mm in diameter was fixed in the lowcircumference material of the diffusion coefficient. These phantoms were imaged using DW imaging (DWI) of 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 15, and 20 mm slice thickness using the multi-b values. In addition, different SNR were imaged by changing field-of-view and the number of additions. ADC was calculated by DWI of the different b values. As a result, slice thickness showed a peak at 50-65% of the diameter of the signal body. Furthermore, ADC values fluctuated in the slice thickness in front of the peak with a change in SNR. In conclusion, the ADC value was most accurate at a setting of 50-65% of slice thickness for the object diameter.

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Recently, many imaging methods are developed in magnetic resonance imaging and in particular, the release of the 3D acquisition method is remarkable. The image distortion often becomes the problem by the gradient echo method and the echo planar imaging (EPI) -based method, but the image distortion of the 3D acquisition is not established. A purpose of this study is to examine the utility of the novel evaluation method of the image distortion for the 3D acquisition image. The spin echo image was used as a criteria image, and EPI was used as a target image for 3D acquisition imaging. Image J was used for the image processing. The value that divided the volume of the different shape of criteria image and the target image by the volume of the criteria image was defined as a distortion rate. Hence, we refer this method to the volume method. It is reported that the distortion rate of the EPI is proportional to a rectangle rate of rectangular field of view (RFOV). The distortion rate of the volume method for 50-100% of rectangle ratio was compared with the theoretical value. In addition, the dependence by the threshold of the binarization was considered. Furthermore, the comparison with the NEMA (National Electrical Manufacturers Association) method was carried out. As a result, the distortion rate decreased according to a rectangular rate of RFOV by the volume method, and the numerical value was equal with a theoretical value. In addition, the distortion rate did not have the effect by the thresholding of binarizing. The volume method had less error of measurement than the NEMA method.