Published papers

© 2018 Wolters Kluwer Health, Inc. All rights reserved. A 53-year-old woman with metastatic esthesioneuroblastoma was referred for FDG PET/CT imaging. FDG PET/CT showed symmetrical uptake in bilaterally enlarged adrenal glands, in addition to abnormal uptake in bone and lymph node metastases. 111In-pentetreotide scintigraphy was further performed and revealed the lack of adrenal uptake. The patient's serum adrenocorticotropic hormone (ACTH) level was extremely high, suggesting that hyperplastic condition in the adrenal glands due to ACTH stimulation from the metastatic esthesioneuroblastoma was responsible for increased FDG uptake. The combination of FDG PET and 111In-pentetreotide scintigraphy was useful for the pathophysiological evaluation of ACTH-secreting esthesioneuroblastoma.

© 2019, The Author(s). Background: Evidence has shown the clinical usefulness of measuring the metastatic tumor burden of bone for prognostic assessment especially in prostate cancer; quantitative evaluation by dedicated SPECT is difficult due to the lack of attenuation correction (AC) method. We developed a novel method for attenuation correction using bone SPECT emission data (bone SPECT-based segmented attenuation correction; B-SAC) where emission data were virtually segmented into three tissues (i.e., bone, soft tissue, and air). Then, the pixel values in SPECT were replaced by 50 for the virtual soft tissue, and − 1000 for the virtual air. The replaced pixel values for the virtual bone were based on the averaged CT values of the normal vertebrae (B-SACN) or the metastatic bones (B-SACM). Subsequently, the processed SPECT data (i.e., SPECT value) were supposed to realize CT data (i.e., CT value) that were used for B-SAC. The standardized uptake values (SUVs) of 112 metastatic bone tumors in 15 patients with prostate cancer were compared between CTAC with scatter correction (SC) and resolution recovery (RR) and the following reconstruction conditions: B-SACN (+)SC(+)RR(+), B-SACM (+)SC(+)RR(+), uniform AC(UAC)(+)SC(+)RR(+), AC(−)SC(+)RR(+), and no correction (NC). Results: The SUVs in the five reconstruction conditions were all correlated with those in CTAC(+)SC(+)RR(+) (p < 0.01), and the correlations between B-SACN or B-SACM and CTAC images were excellent (r > 0.94). Bland-Altman analysis showed that the mean SUV differences between CTAC (+)SC(+)RR(+) and the other five reconstructions were 0.85 ± 2.25 for B-SACN (+)SC(+)RR(+), 1.61 ± 2.36 for B-SACM (+)SC(+)RR(+), 1.54 ± 3.84 for UAC(+)SC(+)RR(+), − 3.12 ± 4.97 for AC(−)SC(+)RR(+), and − 5.96 ± 4.59 for NC. Compared to CTAC(+)SC(+)RR(+), B-SACN (+)SC(+)RR(+) showed a slight but constant overestimation (approximately 17%) of the metastatic tumor burden of bone when the same threshold of metabolic tumor volume was used. Conclusions: The results of this preliminary study suggest the potential for B-SAC to improve the quantitation of bone metastases in bone SPECT when X-ray CT or transmission CT data are not available. Considering the small but unignorable differences of lesional SUVs between CTAC and B-SAC, SUVs obtained with the current version of B-SAC seem difficult to be directly compared with those obtained with CTAC.

Fast kilovoltage (kVp)-switching technology cannot obtain conventional 120 kVp images; thus, 70 keV virtual monochromatic spectral computed tomography (CT) images (VMSI) are generally used. The contrast-to-noise ratio (CNR) is used to evaluate the image quality of VMSI; however, CNR does not include frequency characteristics. The present study aimed to investigate the evaluation methods of VMSI considering frequency characteristics by comparing the image quality of 70 keV VMSI with that of conventional 120 kVp images. The evaluated object contrasts were 70 and 300 Hounsfield units (HU). Scans used two radiation dose levels: low (LD) and standard (SD). The volume CT dose index of LD and SD was 4.8- and 12 mGy, respectively. Images were reconstructed by filtered back projection, evaluating CNR, noise power spectrum (NPS), task transfer function (TTF), and system performance (SP) function calculated as TTF / NPS. The total NPS values (spatial frequency range: 0.2 ~ 0.4 mm ) of 70 keV VMSI were higher than those of 120 kVp images. The spatial frequency TTF values that reached 10% (f ) of the 70 keV VMSI changed based on object contrast. For the low-contrast condition, a lower f was observed with 70 keV VMSI. The CNR of 70 keV VMSI was comparable to that of 120 kVp images in low- and high-contrast conditions. However, for 70 keV VMSI, SP of low-contrast was low, and SP of high-contrast was high, compared with those of 120 kVp images. This study suggested that only CNR was not sufficient to evaluate the image quality of VMSI; thus, evaluation methods considering frequency characteristics should be used. 2 −1 10% 10%

Background: The effectiveness of facial massage is often explained by the resulting increases in the blood and lymphatic flow. However, it is difficult to explain the lifting effect on the cheeks. The aim of this study was to analyze facial mobility to further current understanding of the effectiveness of facial massage. Materials and Methods: Two kinds of analytical methods were designed using a cadaveric head as well as advanced computed tomography (CT). The cadaveric face was divided into three sections, and three different colors of ink were injected into each section. It was kept in a supine position for 24 hours, and the ink distribution was observed. Upright and supine CT examinations were performed on six healthy adult volunteers. The images of both were superimposed by a three-dimensional image analysis system, and changes in facial contours were analyzed. Results: The three colors of ink spread craniocaudally and were distributed differently from the gravitational vector. When both CT images were superimposed, two distinct lines were formed, which represented overlapping of the facial contours due to the two different CT images. These lines were found to correspond to the border of each color of the ink. Conclusion: Focusing on the mobility of the face, the soft tissue of the face had vertical mobility, and it was speculated that this mobility is involved in the effectiveness of facial massage. Our results could provide useful information for cosmetic treatment and contribute to the collection of scientific knowledge for anti-aging medicine.

Objective: To report the clinical and imaging characteristics of BCG-osteomyelitis, and compare them with those of pyogenic osteomyelitis. Materials and methods: Clinical and imaging findings were retrospectively evaluated in 14 children with BCG osteomyelitis, including 3 with Mendelian susceptibility to mycobacterial diseases (MSMD), and in 40 children with pyogenic osteomyelitis, using Fisher exact and Mann-Whitney U tests. Results: BCG-osteomyelitis was an indolent inflammatory disease of young children (mean age 15.5 months). Immunocompetent patients came to medical attention over months after vaccination, while patients with MSMD much earlier (the average time lapse: 13.7 vs. 5.0 months). The former manifested with a slowly progressive, painless mass with only mildly increased acute-phase reactants, while the latter started with lymphadenitis with significant inflammatory reactions and later developed osteomyelitis. These clinical scenarios contrasted with acute febrile illness in pyogenic osteomyelitis. The imaging findings were identical in both immunocompetent and MSMD groups; however, the former showed monoostotic involvement, while the latter polyostotic affliction. The typical imaging finding of BCG-osteomyelitis comprises a large intraosseous abscess with modest reactive edema commonly associated with transphyseal extension from the metaphysis to the epiphysis, contrasting with the manifestation of pyogenic osteomyelitis; size of abscess (p=0.028), pattern of abscess extension (p<0.001), and extent of surrounding edema (p<0.001). Conclusions: BCG-osteomyelitis should be suspected in children under 2 years of age with insidious osteomyelitis, accompanied with characteristic imaging findings. Polyostotic BCG osteomyelitis is highly suggestive of MSMD. Awareness of the distinctive features of BCG-osteomyelitis enables the early diagnosis and timely therapeutic intervention.

Objectives and Background: The objective of this study was to investigate the image quality-improving and heart rate-lowering effects of landiolol hydrochloride (a short-acting β1-adrenergic receptor blocker) on coronary computed tomography angiography (CCTA). During CCTA, β-adrenergic receptor blockers have been commonly used to lower heart rate and improve image quality. Methods: A total of 258 subjects suspected of having ischemic cardiac disease and requiring CCTA were randomized to either a landiolol hydrochloride 0.125 mg/kg group or placebo group to study the efficacy and safety of landiolol hydrochloride in a multicenter, double-blind, randomized parallel study. The primary endpoint was the diagnosable proportion (proportion of subjects whose coronary stenosis was diagnosable). Results: The diagnosable proportions about the reconstruction images at mid-diastole were 68.2 and 38.2 % in the landiolol hydrochloride and placebo group, respectively, indicating significant superiority of landiolol hydrochloride over placebo (p < 0.0001). The diagnosable proportions about the optimal reconstruction images were 81.4 and 54.2 % in the landiolol hydrochloride and placebo group, respectively, indicating significant superiority of landiolol hydrochloride over placebo (p < 0.0001). The mean heart rate-lowering effect was first observed soon after administration of landiolol hydrochloride, was most marked at 3-5 min, and disappeared 30 min after completion of administration. The mean heart rate-lowering proportion at that time was -19.1 ± 8.1 % and -5.9 ± 9.7 % in the landiolol hydrochloride and placebo groups, respectively, showing a significantly higher proportion in the landiolol hydrochloride group. Conclusions: Landiolol hydrochloride was confirmed to significantly and rapidly lower heart rate after intravenous injection, suggesting that it is a safe and useful agent for improving the image quality of CCTA. © 2013 The Author(s).

Background: To externally validate the prognostic impact of preoperative neutrophil–lymphocyte ratio (pre-NLR) in patients with upper tract urothelial carcinoma (UTUC) following radical nephroureterectomy (RNU).Methods: A total of 665 patients from 12 institutions were included. The median follow-up was 28 months. Associations between pre-NLR level and outcome were assessed using multivariate analysis. A pre-NLR level of >3.0 was defined as elevated.Results: Pre-NLR levels were elevated in 184 patients (27.7 %), and pre-NLR elevation was significantly associated with worse pathological features such as tumor grade 3, advanced pT stage, positive lymphovascular invasion (LVI), and lymph node involvement in RNU specimens. The 5-year recurrence-free and cancer-specific survival rates were 57.0 % (p < 0.001) and 60.2 % (p < 0.001), respectively, in patients with elevated pre-NLR, and 69.2 and 77.3 %, respectively, in their counterparts. Multivariate analysis showed that elevated pre-NLR was an independent risk factor for predicting subsequent disease recurrence (p = 0.037; hazard ratio (HR) 1.38) and cancer-specific mortality (p = 0.036;, HR 1.47), although the addition of pre-NLR slightly improved the accuracies of the base model for predicting both disease recurrence and cancer-specific mortality to 79.8 % (p = 0.041) and 83.0 % (p = 0.039), respectively (gain in predictive accuracy: 0.2 and 0.1 %, respectively).Conclusion: This multi-institutional study revealed that elevated pre-NLR was significantly associated with worse pathological features such as tumor grade 3, advanced pT stage, positive LVI, and lymph node involvement in RNU specimens, and elevated pre-NLR was an independent risk factor of disease recurrence and cancer-specific mortality in UTUC patients treated with RNU.

OBJECTIVES: To compare quantitative and subjective image quality between virtual monochromatic spectral (VMS) and conventional polychromatic 120-kVp imaging performed during the same abdominal computed tomography (CT) examination.MATERIALS AND METHODS: Our institutional review board approved this prospective study; each participant provided written informed consent. 51 patients underwent sequential fast kVp-switching dual-energy (80/140 kVp, volume CT dose index: 12.7 mGy) and single-energy (120-kVp, 12.7 mGy) abdominal enhanced CT over an 8 cm scan length with a random acquisition order and a 4.3-s interval. VMS images with filtered back projection (VMS-FBP) and adaptive statistical iterative reconstruction (so-called hybrid IR) (VMS-ASIR) (at 70 keV), as well as 120-kVp images with FBP (120-kVp-FBP) and ASIR (120-kVp-ASIR), were generated from dual-energy and single-energy CT data, respectively. The objective image noises, signal-to-noise ratios and contrast-to-noise ratios of the liver, kidney, pancreas, spleen, portal vein and aorta, and the lesion-to-liver and lesion-to-kidney contrast-to-noise ratios were measured. Two radiologists independently and blindly assessed the subjective image quality. The results were analyzed using the paired t-test, Wilcoxon signed rank sum test and mixed-effects model with Bonferroni correction.RESULTS: VMS-ASIR images were superior to 120-kVp-FBP, 120-kVp-ASIR and VMS-FBP images for all the quantitative assessments and the subjective overall image quality (all P<0.001), while VMS-FBP images were superior to 120-kVp-FBP and 120-kVp-ASIR images (all P<0.004).CONCLUSIONS: VMS images at 70 keV have a higher image quality than 120-kVp images, regardless of the application of hybrid IR. Hybrid IR can further improve the image quality of VMS imaging.

The purpose of this study was to compare the safety and efficacy of the short-acting β1-receptor blocker, landiolol hydrochloride (0.06 and 0.125-mg/kg), to placebo during coronary computed tomography angiography (CTA) in a phase 2 dose-finding study. A total of 183 patients suspected of having ischemic cardiac disease and scheduled to undergo an invasive coronary angiography were randomized to groups treated with landiolol hydrochloride (0.06 or 0.125-mg/kg) or placebo. The heart rate, safety, and the performance of coronary diagnosis using landiolol hydrochloride were evaluated in a multicenter, doubleblind, randomized, parallel study. The patients' heart rates during the coronary CTA were 67.6 ± 8.7 and 62.6 ± 7.8 beats/min in the 0.06 and 0.125-mg/kg landiolol hydrochloride groups, respectively, both of which were significantly lower than the heat rate of 73.7 ± 11.8 beats/min in the placebo group (P = 0.003 and P<0.001, respectively). No adverse events or reactions occurred at an incidence of 5 % or greater, confirming the safety of landiolol hydrochloride. The proportion of correctly classified patients was significantly higher in the 0.125-mg/kg landiolol hydrochloride group than in the placebo group (73.6 vs. 50.0 %). Landiolol hydrochloride at doses of 0.06 and 0.125-mg/kg significantly decreased the heart rate compared with a placebo. The present findings suggest that landiolol hydrochloride is safe and useful at a dose of 0.125-mg/kg to improve coronary diagnostic performance during coronary CTA. © Springer Science+Business Media Dordrecht 2013.

Background: Acute exacerbation of usual interstitial pneumonia is one of the most life-threatening complications after resection of lung cancer. It is important to detect patients at high risk for acute exacerbation. The purpose of this study was to investigate the incidence of postoperative acute exacerbation and the importance of the finding of honeycombing in predicting the risk of it. Methods: From 992 consecutive pulmonary resections for lung cancer, the background lung was retrospectively assessed histologically. Preoperative chest computed tomographic images of those patients with histologically proven usual interstitial pneumonia were retrospectively reassessed and classified into three groups: typical honeycombing, possible honeycombing, and no honeycombing. Records of patients who experienced postoperative acute exacerbation were extracted from the clinical database, and the correlation between computed tomographic findings and incidence of acute exacerbation was analyzed. Results: Of the 992 lung cancer patients, 12 (1.2%) experienced postoperative acute exacerbation. Usual interstitial pneumonia was histologically confirmed in 249 patients, and 4.8% of them experienced postoperative acute exacerbation. No patient without usual interstitial pneumonia experienced it. Preoperative computed tomographic images were available in 205 of the 249 patients. Postoperative acute exacerbation developed in 13.6% of patients (6 of 44 patients) in the typical honeycombing group, 6.4% of patients (5 of 78 patients) in the possible honeycombing group, and 0% of patients (0 of 83 patients) in the no-honeycombing group. Compared with the no-honeycombing group, the incidence of acute exacerbation in the typical and possible honeycombing groups was significantly higher (p = 0.001, p = 0.025, respectively). Conclusions: Physicians should consider the finding of possible honeycombing, as well as typical honeycombing, a potential risk factor for acute exacerbation after pulmonary resection for lung cancer. © 2012 The Society of Thoracic Surgeons.

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. Pancreatic hamartoma is a rare benign tumor. Its preoperative diagnosis is challenging. We present a case of pancreatic hamartoma whose radiological-pathological correlation was evaluated in detail. A 53-year-old man was referred to our institution for diagnosis and treatment. Contrast-enhanced computed tomography (CT) and magnetic resonance image revealed a 3.5 cm long tumor arising from the head of the pancreas with cystic and solid components, the latter of which was gradually and inhomogeneously enhanced in the delayed phase. Fluorodeoxyglucose (FDG) positron emission tomography/CT revealed slight FDG uptake in the solid component. Histologically, a number of pancreatic lobule-like structures, which were mainly composed of aggregates of small ducts embedded in concentric fibrous stroma with no apparent islets or peripheral nerves, were observed in the solid component, whereas multiple dilated ducts were seen in the cystic region. The solid component also contained a narrow area of edematous fibrous stroma with low vessel density, which corresponded with the unenhanced part in the inhomogeneously enhanced solid component. There was no remarkable cytological atypia throughout the mass. A pathological diagnosis of pancreatic hamartoma was made. The radiological findings agree well with the pathological findings. When a pancreatic tumor is of the solid type, preoperatively diagnosing it as pancreatic hamartoma is not possible. However, when a pancreatic tumor with cystic and solid components is inhomogeneously enhanced in contrast-enhanced studies, a diagnosis of pancreatic hamartoma can be considered.

© 2019 Elsevier Inc. Background: The flow dynamics of the intracranial venous channels are fundamentally important for understanding intracranial physiology and pathophysiology. However, the method clinically applicable to the evaluation of the flow dynamics of the intracranial venous system has not been well described in the reported data. We have developed a new method to evaluate intracranial venous flow direction and velocity using 4-dimensional (4D) computed tomography angiography (CTA). The aim of the present study was to verify the accuracy and validity of 4D-CTA in a clinical setting. Methods: We retrospectively analyzed 97 veins from 26 patients (16 cases of arteriovenous shunt disease, 9 intracranial tumor cases, and 1 cerebral aneurysm case) who had undergone both 4D-CTA and conventional digital subtraction angiography (DSA). Using 4D-CTA, we analyzed the time-density curve with gamma distribution extrapolation and obtained the direction of the flow and flow velocity of each vein. The direction of the flow in 4D-CTA was also collated with that obtained using conventional DSA to verify the experimental method. Results: The direction of the flow determined by 4D-CTA was consistent with that of conventional DSA in 94.8% of cases. The average venous flow velocity was 64.3 mm/second and 81.8 mm/second, respectively, in the antegrade and retrograde channels affected by arteriovenous shunts. Conclusions: The present flow analysis using 4D-CTA enabled us to evaluate the direction and velocity of intracranial venous flow. Other than some limitations, the presented method is reliable and its potential for application in clinical settings is promising.

© 2020 Society for Vascular Surgery Objective: Although the development of lymphatic collaterals is expected following lymphedema, little is known about the anatomic details of such compensatory pathways or their association with symptoms. Magnetic resonance lymphangiography (MRL) has been shown to be superior to lymphoscintigraphy and indocyanine green lymphography in visualizing lymphatics. This study aimed to analyze MRL images of lower limbs to elucidate the patterns of lymphatic collateral formation and their association with the clinical stages of lymphedema. Methods: We enrolled 56 consecutive patients (112 lower limbs) with lymphedema who underwent MRL. Two radiologists performed a consensus reading of MRL images for the presence or absence of collateral lymphatic pathways, and the results were compared with the clinical stages. Furthermore, the frequency of abnormal MRL findings in 43 asymptomatic lower limbs of patients with unilateral lymphedema was analyzed and compared with that in the 69 symptomatic lower limbs of the patients. The imaging findings were also compared with the cause of lymphedema. Results: All three collateral pathways (anterolateral, deep, and posteromedial lymphatics) were visualized at a higher (P <.05) frequency in stage II than in stage 0 lower limbs. The frequency of visualization of the three collaterals was significantly higher in symptomatic (stages I-III) lower limbs than in asymptomatic (stage 0) lower limbs. Most (76.8%) of the symptomatic limbs exhibited at least one of these collaterals, and the frequency was significantly higher than in the asymptomatic limbs (P <.001). Most (81.4%) of the asymptomatic (stage 0) lower limbs had at least one abnormal finding in terms of lymphatic circulation, although this proportion was significantly lower compared with the symptomatic limbs (98.6%). The collaterals tended to appear less frequently in primary lymphedema than in secondary lymphedema, reaching statistical significance in the posteromedial lymphatics. Conclusions: These results suggested that the two superficial lymphatic groups and the deep lymphatic system act as major collaterals of the lower limbs in patients with lymphedema. Furthermore, MRL of most patients with unilateral lymphedema demonstrated abnormal findings, including collateral formation, not only in the affected lower limb but also in the asymptomatic lower limb. In primary lymphedema, the collaterals may appear less frequently than in secondary lymphedema. Collaterals should be taken into consideration in planning the site of lymphaticovenous anastomosis and assessing disease progression. MRL can visualize preclinical alterations in lymphatic flow and compensatory pathways; therefore, we expect that it will be useful for the early diagnosis of lymphedema.

Purpose: We aimed to evaluate the diagnostic performances of quantitative indices obtained from dopamine transporter (DAT) single-photon emission computed tomography (SPECT) and I-metaiodobenzylguanidine (MIBG) scintigraphy for Parkinsonian syndromes (PS) using the classification and regression tree (CART) analysis. Methods: We retrospectively enrolled 216 patients with or without PS, including 80 without PS (NPS) and 136 with PS [90 Parkinson’s disease (PD), 21 dementia with Lewy bodies (DLB), 16 progressive supranuclear palsy (PSP), and 9 multiple system atrophy (MSA). The striatal binding ratio (SBR), putamen-to-caudate ratio (PCR), and asymmetry index (AI) were calculated using DAT SPECT. The heart-to-mediastinum uptake ratio (H/M) based on the early (H/M [Early]) and delayed (H/M [Delay]) images and cardiac washout rate (WR) were calculated from MIBG scintigraphy. The CART analysis was used to establish a diagnostic decision tree model for differentiating PS based on these quantitative indices. Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 87.5, 96.3, 93.3, 92.9, and 93.1 for NPS; 91.1, 78.6, 75.2, 92.5, and 83.8 for PD; 57.1, 95.9, 60.0, 95.4, and 92.1 for DLB; and 50.0, 98.0, 66.7, 96.1, and 94.4 for PSP, respectively. The PCR, WR, H/M (Delay), and SBR indices played important roles in the optimal decision tree model, and their feature importance was 0.61, 0.22, 0.11, and 0.05, respectively. Conclusion: The quantitative indices showed high diagnostic performances in differentiating NPS, PD, DLB, and PSP, but not MSA. Our findings provide useful guidance on how to apply these quantitative indices in clinical practice. 123

Lymphatic malformations that occur in the head and neck are often difficult to treat. Sclerotherapy using polidocanol, which has little tissue damage, can be treated with minimal dysfunction and complications. In particular, it is considered an effective treatment for superficial lesions that bleed from the mucosal surface. In this study, we performed sclerotherapy using polidocanol for a 17-year-old woman with lymphatic malformations with blood containing lymphorrhea in the pharynx and larynx. A total of 3 sclerotherapy treatments were performed, and lesion reduction and bloody lymphorrhea control were observed. At 1 year after treatment, the course of treatment was good with no re-enlargement of the lesions.

Biliary stricture is a serious postoperative complication of liver transplantation. We report the case of a 2-year-old boy with severe biliary anastomotic stricture after left lobe living donor liver transplantation. As cannulation from the occluded B3 into the jejunum was impossible using the conventional technique, a gunsight approach was utilized. By puncturing balloons dilated at the occluded site of B3 and the proximal end of the non-occlusive B2, a tract between B3 and B2 was created, and the catheter was finally successfully inserted from B3 into the jejunum through the dilated tract and B2. The gunsight approach is an option for severe biliary strictures when the conventional approach proves impossible.

Purpose: To investigate safety management at Japanese facilities performing human MRI studies.Methods: All Japanese facilities performing human MRI studies were invited to participate in a comprehensive survey that evaluated their MRI safety management. The survey used a questionnaire prepared with the cooperation of the Safety Committee of the Japanese Society for Magnetic Resonance in Medicine. The survey addressed items pertaining to the overall MRI safety management, questions on the occurrence of incidents, and questions specific to facility and MRI scanner or examination. The survey covered the period from October 2017 to September 2018. Automated machine learning was used to identify factors associated with major incidents.Results: Of 5914 facilities, 2015 (34%) responded to the questionnaire. There was a wide variation in the rate of compliance with MRI safety management items among the participating facilities. Among the facilities responding to this questionnaire, 5% reported major incidents and 27% reported minor incidents related to MRI studies. Most major incidents involved the administration of contrast agents. The most influential factor in major incidents was the total number of MRI studies performed at the facility; this number was significantly correlated with the risk of major incidents (P < 0.0001).Conclusion: There were large variations in the safety standards applied at Japanese facilities performing clinical MRI studies. The total number of MRI studies performed at a facility affected the number of major incidents.

This study aims to develop and assess a new automated processing technique in MR elastography (MRE), namely coherent-wave auto-selection (CHASE). CHASE enables automatic selection of the region of interest (ROI) for stiffness measurement by extraction of the coherent wave region (CHASE ROI), and it improves the reconstruction of stiffness by a directional filter oriented along the main wave in each pixel (CHASE filtering). In this study, MRE of a phantom and of the liver of four healthy volunteers was performed. To investigate the potential of CHASE, this study assessed the CHASE according to three indices through the phantom study: 1) agreement on the ROI settings between CHASE and expert observers, 2) noise dependency, and 3) effect of the CHASE on stiffness variability within the CHASE ROI. The agreements on the ROI settings were analyzed by Cohen's kappa coefficient (κ). The noise dependency was analyzed by the mean absolute percentage errors (MAPEs) within the ROI between low (20%–80% amplitudes) and high vibration amplitudes (100% amplitude). The stiffness variability was assessed by standard deviation (SD) within the ROI. In the volunteer study, agreements on the ROI settings (or stiffness value) and stiffness variability within the CHASE ROI were assessed using κ-value (or intraclass correlation coefficient: ICC) and coefficient of variation, respectively. The results showed close agreement on the ROI settings and stiffness (κ-value: greater than 0.61 in both the phantom and volunteer studies, ICC: 0.97 in the volunteer study). The MAPEs within the CHASE ROI were much smaller than those in the whole region of the phantom (CHASE ROI vs. the whole region at 20% amplitude: 10.3% vs. 50.8%). Moreover, in both the phantom and volunteer studies, the stiffness variation within the CHASE ROI was smaller in the elastogram processed with CHASE filtering than in the unprocessed one. Our results demonstrated that the CHASE has high robustness against noise and the potential to provide ROI settings for stiffness measurement comparable to expert observers, as well as improve the reconstruction of stiffness.