[Investigating the Usefulness of Breath-holding Instructions by Change in the Room Light for the Hearing Impaired].

PURPOSE: In imaging examinations of patients with hearing impairment, poor image quality due to poor respiratory arrest is a problem directly related to diagnostic imaging. Although there have been studies of non-sound instructions, there have been few quantitative studies using changes in brightness. The purpose of this study was to investigate whether changes in room brightness can be used as a respiratory cessation indicator. METHODS: Fourteen patients were imaged using the 2D FIESTA and LAVA-Flex methods on an MRI system under free respiration, voice-guided cessation of respiration (voice instruction), and room brightness change (light/dark instruction), and compared. RESULTS: The positional fluctuation of the top of the liver by the 2D FIESTA method showed a large positional fluctuation under free breathing, while the positional fluctuation was small under voice instruction and light/dark instruction. The images obtained by the LAVA-Flex method was significantly degraded by motion artifacts under free breathing, whereas there were fewer motion artifacts under voice instruction and light/dark instruction, and the two were the same with no significant difference in visual evaluation. CONCLUSION: The visual cessation of respiration instruction by changing the brightness of the room is as effective as the audible cessation of respiration instruction, suggesting that it can be applied clinically.

Quantitative measurements of emphysema in ultra-high resolution computed tomography using model-based iterative reconstruction in comparison to that using hybrid iterative reconstruction.

The percentage of low attenuation volume ratio (LAVR), which is measured using computed tomography (CT), is an index of the severity of emphysema. For LAVR evaluation, ultra-high-resolution (U-HR) CT images are useful. To improve the image quality of U-HRCT, iterative reconstruction is used. There are two types of iterative reconstruction: hybrid iterative reconstruction (HIR) and model-based iterative reconstruction (MBIR). In this study, we physically and clinically evaluated U-HR images reconstructed with HIR and MBIR, and demonstrated the usefulness of U-HR images with MBIR for quantitative measurements of emphysema. Both images were reconstructed with a slice thickness of 0.25 mm and an image matrix size of 1024 × 1024 pixels. For physical evaluation, the modulation transfer function (MTF) and noise power spectrum (NPS) of HIR and MBIR were compared. For clinical evaluation, LAVR calculated from HIR and MBIR were compared using the Wilcoxon matched-pairs signed-rank test. In addition, the correlation between LAVR and forced expiratory volume in one second (FEV1%) was evaluated using the Spearman rank correlation test. The MTFs of HIR and MBIR were comparable. The NPS of MBIR was lower than that of HIR. The mean LAVR values calculated from HIR and MBIR were 19.5 ± 12.6% and 20.4 ± 11.7%, respectively (p = 0.84). The correlation coefficients between LAVR and FEV1% that were taken from HIR and MBIR were 0.64 and 0.74, respectively (p < 0.01). MBIR is more useful than HIR for the quantitative measurements of emphysema with U-HR images.

Evaluation of the homogeneity of native T1 myocardial mapping using the polarity corrected inversion time preparation method in a myocardial phantom and healthy volunteers.

Myocardial T1 mapping is a useful technique for the diagnosis of diffuse fibrosis. Although modified look-locker inversion recovery is a widely used T1 mapping method, variation in T1 values has been reported. Non-uniform T1 maps may hinder differentiation between healthy and diseased myocardial tissue. The purpose of this study was to investigate the uniformity of T1 mapping using polarity corrected inversion time preparation (PC TI prep) in a myocardial phantom and healthy volunteers. The myocardial phantom was scanned between polyvinyl alcohol (PVA) and air. T1 values were measured using inversion recovery fast spin-echo (IR-FSE) and PC TI prep in areas adjacent to PVA and air. For the volunteer study, the short-axis plane was imaged using the PC TI prep to compare T1 values in the myocardium of the septal and lateral walls. The T1 value of the phantom using the IR-FSE was not significantly different in the area between PVA and air, whereas the T1 value using the PC TI prep in the air area was significantly lower than that in the PVA area. T1 mapping of the healthy myocardium exhibited no significant difference between the septal and lateral walls. The T1 value using the PC TI prep in the air area was 6.3% lower than that using IR-FSE. In this study, T1 mapping using the PC TI prep exhibited high uniformity of T1 values.