大野 良治

PURPOSE: Since the clinical application of computed tomography (CT), cardiac and respiratory motion artifacts have caused decreased image quality and reduced detection or quantitative or qualitative evaluation of lung parenchymal or vascular abnormalities on chest CT with lung window settings in patients with pulmonary diseases. Recently, a deep learning (DL)-based motion correction algorithm (CLEAR Motion) has been developed and clinically used for chest CT. We hypothesized that CLEAR Motion can significantly reduce motion artifacts on chest CT examinations relative to conventional chest CT images reconstructed without CLEAR Motion. The purpose of this study was to determine the utility of CLEAR Motion for image quality improvement in chest CT with lung window settings in patients with various pulmonary diseases. MATERIALS AND METHODS: Fifty-six consecutive patients with various thoracic diseases underwent non-electrocardiogram-gated chest helical CT examination using a 320-detector row CT and underwent reconstruction using the conventional reconstruction method and CLEAR Motion. To compare the quantitative image quality, the cardio-pulmonary edge distance (CPED) and slope (CPES) were measured on each CT scan in the axial plane. Comparing cardiac motion reduction capability, overall image quality, cardiac motion artifact, and region conspicuity were visually assessed in the lung window setting on the axial, coronal, and sagittal planes. The paired t-test and Wilcoxon signed-rank test were then performed. RESULTS: The CPEDs and CPESs of the entire lung and left lung on CT with CLEAR Motion were significantly superior to those of CT without CLEAR Motion (p < 0.001). The overall image quality, cardiac motion artifact, and region conspicuity on CT with CLEAR Motion were significantly higher than those without CLEAR Motion on each plane (p < 0.001). CONCLUSION: The DL-based motion correction algorithm named as 'CLEAR Motion' has a potential to improve image quality on chest CT with lung window setting in patients with pulmonary diseases.

PURPOSE: To evaluate whether reverse encoding distortion correction (RDC) improves image quality and maintains apparent diffusion coefficient (ADC) measurements in diffusion-weighted imaging (DWI) on female pelvic MRI using a 1.5-T in in vitro and in vivo studies. METHODS: This retrospective, institutional review board-approved study included both in vitro and in vivo analyses of 31 women (mean age, 41 ± 15 years; range, 24-80 years) who underwent pelvic MRI between January and March 2022. T2-weighted image (T2WI) and DWI with and without RDC were acquired, and ADC maps were generated. Quantitative metrics included SNR, contrast-to-noise ratio (CNR), ADC values, and deformation ratio (DR), defined as the proportional area discrepancy between DWI and T2WI for the uterine corpus, cervix, ovary, and lesions. Qualitative assessments-overall image quality (OIQ), deformation severity (DS), and diagnostic confidence level (DCL)-were independently scored by 2 blinded radiologists using 5-point scales. RESULTS: In vitro SNR and ADC values showed no significant differences between DWI with and without RDC, with strong correlations to reference measurements (ρ = 0.99, P < 0.001). In vivo, SNR, CNR, and ADC values of the myometrium, cervix, and ovary did not differ significantly between 2 methods (P > 0.05). DRs were significantly lower in DWI with RDC than in DWI without RDC (P ≤ 0.0003). ADC values showed strong correlations between DWI with and without RDC on uterine corpus, cervix, ovary and lesions (ρ = 0.82-0.90, P < 0.001). Qualitative scores improved with RDC: higher OIQ (P = 0.0004), lower DS (P = 0.0004), and higher DCL (P = 0.03). Interobserver agreement ranged from substantial to almost perfect (κ = 0.78-0.97). CONCLUSION: RDC improves image quality and reduces image distortion in DWI on female pelvic MRI at a 1.5-T, while maintaining ADC measurements in in vitro and in vivo settings.

PURPOSE: The present study directly compared the quantitative capabilities of regional perfusion and pulmonary functional change assessments among electrocardiography (ECG)- and photoplethysmography (PPG)-monitored phase-resolved functional lung (PREFUL) MRI and dynamic contrast-enhanced (CE) perfusion MRI in thoracic oncologic patients. METHODS: Seventeen thoracic oncologic patients prospectively underwent ECG- and PPG-monitored PREFUL MRI, dynamic CE-perfusion MRI, and pulmonary function tests. ECG- and PPG-monitored perfusion-weighted PREFUL MRI (PW-MRI) and quantitative perfusion maps from dynamic CE-perfusion MRI were generated. Regional perfusions were determined using ROI measurements. For each patient, the overall perfusion from each method was determined as the average ROI measurement value. To determine the relationship between regional perfusion among all methods, Pearson's correlations were performed. Tukey's honest significant difference test was performed to compare regional perfusion among ventral, middle, and dorsal slice positions on ECG- and PPG-monitored PW-MRI and quantitative perfusion maps. To assess the pulmonary functional loss evaluation capability of each MRI method, each overall perfusion was correlated with %VC and %FEV1 using Pearson's correlation. RESULTS: The correlation of regional perfusion between ECG- and PPG-monitored PW-MRI was significant and good (r = 0.79, P < 0.0001). However, the correlations between ECG- or PPG-monitored PW-MRI and quantitative perfusion maps were assessed as significant and fair (ECG: r = 0.4, P < 0.0001; PPG: r = 0.36, P < 0.0001). ECG- and PPG-monitored PW-MRI demonstrated significantly higher perfusion than the quantitative perfusion map (P < 0.0001). Furthermore, ECG-and PPG-monitored PW-MRI and quantitative perfusion maps had significant and moderate correlations (%VC: 0.60 ≤ r ≤ 0.63, P < 0.05; %FEV1: 0.52 ≤ r ≤ 0.69, P < 0.05). CONCLUSION: ECG- and PPG-monitored PREFUL MRI had similar potential to dynamic CE-perfusion MRI for quantitatively assessing regional perfusion and pulmonary functional changes in thoracic oncologic patients. Furthermore, PPG-monitored PREFUL MRI showed little difference in regional perfusion evaluation compared with ECG-monitored PREFUL MRI and the potential to play a complementary role in this setting.