[Effect of Imaging Parameters for High-resolution Diffusion-weighted Imaging on Signal-to-noise Ratio and ADC in Prostate Examination].

Readout-segmented echo-planar imaging (readout segmentation of long variable echo trains [RESOLVE]) can be set to higher resolution than single-shot echo planar imaging, but there is concern that the signal-to-noise ratio (SNR) is low. The purpose was to examine the effect of imaging parameters (repetition time: TR, number of excitations: NEX) for RESOLVE on SNR and apparent diffusion coefficient (ADC) value in 1.5 T MRI, assuming a prostate examination. We imaged eight healthy male volunteers at a b value of 800 s/mm2. SNR and ADC value were calculated by setting the ROI in the transition zone (TZ) and the peripheral zone (PZ) of the prostate. Then, 3 radiologists visually evaluated the graininess. In TZ, there was no significant difference in SNR with changing TR. In PZ, SNR increased with increasing TR. In PZ, median SNR was 8.1 [6.9-9.3] at TR=11000 ms and NEX=2. On the other hand, at TR=5000 ms and NEX=3,4, median SNRs were 8.5 [7.5-9.3] and 9.8 [8.8-11.2]. Moreover, NEX=5 with median SNR of 11.1 [10.7-11.7] was significant (p<0.008). Setting more NEX was more effective in increasing SNR. In addition, visual evaluation showed similar results. The ADC value in TZ was around 1404×10-6 mm2/s, and the ADC value in PZ was around 1469×10-6 mm2/s. There were no significant differences under each condition. In conclusion, NEX is more effective than TR for improving SNR both quantitatively and visually in PZ.

[Comparison of Detectability for the New Image Processing and Conventional Image Processing by ROC Analysis: A Phantom Study of Chest Radiography].

The purpose of this study is to compare the detectability of diseases the new image processing and the conventional image processing by receiver operating characteristic (ROC) analysis and to show the usefulness of the new image processing. Radiographs with and without nodular cancer models in the chest phantom were used for observation samples. Totally 200 radiographs were evaluated by 10 radiological technologists (each readers had over 20 years or under 4 years of experience). The mean area under the curve (AUC) calculated from the over 20 years group was 0.754 for the new processing and 0.771 for the conventional processing (p value=0.651, 95% confidence interval=-0.084/0.049 (lower bound/upper bound)). On the other hand, the average AUC calculated from under 4 years group was 0.819 for the new processing and 0.678 for the conventional processing (p value= 0.041, 95% confidence interval=0.019/0.262 (lower bound/upper bound)). New image processing provides high detectability in less than 4 years group compared to conventional processing.

Treatment response of ethyl pyruvate in a mouse model of chronic obstructive pulmonary disease studied by hyperpolarized 129 Xe MRI.

PURPOSE: The purpose of this work was to investigate disease progression and treatment response in a murine model of chronic obstructive pulmonary disease (COPD) using a preclinical hyperpolarized 129 Xe (HPXe) magnetic resonance imaging (MRI) strategy. METHODS: COPD phenotypes were induced in 32 mice by 10 weeks of exposure to cigarette smoke (CS) and lipopolysaccharide (LPS). Efficacy of ethyl pyruvate (EP), an anti-inflammatory drug, was investigated by administering EP to 16 of the 32 mice after 6 weeks of CS and LPS exposure. HPXe MRI was performed to monitor changes in pulmonary function during disease progression and pharmacological therapy. RESULTS: HPXe metrics of fractional ventilation and gas-exchange function were significantly reduced after 6 weeks of CS and LPS exposure compared to sham-instilled mice administered with saline (P < 0.05). After this observation, EP administration was started in 16 of the 32 mice and continued for 4 weeks. EP was found to improve HPXe MRI metrics to a similar level as in sham-instilled mice (P < 0.01). Histological analysis showed significant alveolar tissue destruction in the COPD group, but relatively normal alveolar structure in the EP and sham-instilled groups. CONCLUSION: This study demonstrates the potential efficacy of EP for COPD therapy, as assessed by a noninvasive, translatable 129 Xe MRI procedure. Magn Reson Med 78:721-729, 2017. © 2016 International Society for Magnetic Resonance in Medicine.