MRI safety for leave-on powdered hair thickeners under 1.5-T and 3.0-T MRI: measurement of deflection force, MRI artifact, and evaluation of preexamination screening.

This study aimed to clarify the magnetic resonance imaging (MRI) compatibility of leave-on powdered hair thickeners by evaluating the displacement force and image artifacts of commercially available leave-on powdered hair thickeners on MRI devices and their response to metal and ferromagnetic detectors. Thirteen types of leave-on powdered hair thickeners were studied: nine hair thickener and four foundation types. MRI systems of 1.5 T and 3.0 T were used. Deflection angles and MR image artifacts according to ASTM F2052 and F2119 were evaluated. Handheld metal and ferromagnetic detectors were used to investigate whether hair thickeners could be detected in screening before MRI examinations. The hair thickener type had a deflection angle of 0°, whereas the foundation type had a deflection angle of 90°, indicating a strong physical effect. Significant image artifacts appeared only on the foundation type. The foundation type reacted at distances of less than 10 cm only with a ferromagnetic detector. Foundation-type leave-on powdered hair thickeners containing magnetic substances exhibited strong physical effects and produced significant image artifacts, and those can only be detected by screening with a ferromagnetic detector.

Evaluation of capillary blood volume in the lower limb muscles after exercise by intravoxel incoherent motion.

PURPOSE: The purpose of this study was to evaluate the change in capillary blood volume in the muscles of the lower limbs, before and after exercise, using intravoxel incoherent motion (IVIM). MATERIALS AND METHODS: Diffusion-weighted images were obtained (with 16 b values) from the thigh and leg muscles of 11 subjects. The imaging was obtained before and immediately exercise; additionally, imaging was performed at 3 h, 6 h, and 24 h after exercise, and an IVIM index was calculated. The exercise involved walking up and down a flight of stairs (140 steps) ten times. The IVIM of each time course-before and after the exercise-was compared. In addition, we examined the correlation of IVIM measurements with the degree of the muscle ache that occurred at 24 h following the exercise. RESULTS: The IVIM index significantly increased after exercise compared with that before exercise (P < 0.01). IVIM decreased at 3 h following exercise, but increased again at 24 h. A correlation was found between the IVIM index at 24 h after exercise and the degree of the muscle ache (r = 0.80) CONCLUSIONS: The capillary blood volume significantly increased after exercise when compared to before exercise. The capillary blood volume decreased after exercise at 3 h and 6 h following exercise, but it increased again at 24 h. There was a correlation between the degree of muscle ache and the amount of capillary blood volume measured from the femoral muscle at 24 h after exercise.

[Capillary Blood Flow of Muscle Before and After the Exercise Used by Intravoxel Incoherent Motion].

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.

[The Novel Evaluation Method of Geometric Distortion for 3D-MRI].

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.

[Effect of Slice Thickness for Apparent Diffusion Coefficient Measurement of Mass].

Apparent 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 low-circumference 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.