Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Purpose: Diagnostic reference levels (DRLs) are defined as fluoroscopic dose rate measurements that are used for patient dose management in angiography. It is recommended that DRLs be measured at least once a year. This study aimed to evaluate the long-term fluctuations of fluoroscopic dose rate in an angiography system.

Methods: An unconnected X-ray output analyzer was used to measure the fluoroscopic dose rate (air kerma rate) at the patient's entrance reference point for a specific angiography system. The target period was from 2015 to 2022, and four measurements per year were made. First, the fluoroscopic dose rate was measured, and the average value and standard deviation for the target period were calculated. Next, the uncertainty of the measured values and the coefficient of variation were calculated. Finally, we calculated the fluoroscopic dose rate measurement error.

Results: The average±standard deviation of the fluoroscopic dose rate was 353.29±9.11 µGy/s. The maximum uncertainty and coefficient of variation for each year were 5.41 µGy/s and 0.03, respectively. The maximum measurement error was 4.67%, where the mean measured value was taken as the true value.

Conclusion: The fluctuation in the measured value of the fluoroscopic dose rate by an angiography system for 8 years is within ±5%, indicating stable X-ray output.

Purpose: Root Cause Analysis (RCA) of reported incident reports can lead to measures to prevent the recurrence of accidents. The purpose of this study is to clarify the relationship between the occurrence of cases, causal factors, contributing factors, and the experience years of the reporters classified into three groups: less than 2 years, 3 to less than 5 years, and more than 5 years, for incident reports subject to RCA.

Methods: From April 2018 to March 2023, a chi-square test was conducted between each item extracted from 239 cases subject to RCA and the experience years of the reporters, with a significance level of less than 5% considered significant.

Results: Regarding the occurrence cases, radiological technologists with longer experience had more misidentified a patient and fewer errors in imaging conditions and range, while radiological technologists with 3 to less than 5 years of experience had more errors in imaging conditions (p<0.001). In terms of occurrence factors, radiological technologists with 3 to less than 5 years of experience had more cases of insufficient confirmation (p<0.05). For contributing factors, there was no significant difference between the experience year groups (p=0.19), with "Impatience" being the most common factor.

Conclusion: This survey suggested that in incident reports of radiological technologists, "Impatience" is a contributing factor that can occur regardless of years of experience.

Purpose: Using a magnetic resonance (MR) image generation technique with deep learning, we elucidated whether changing the training data patterns affected image generation accuracy.

Methods: The pix2pix training model generated T1-weighted images from T2-weighted images or FLAIR images. Head MR images obtained at our hospital were used in this study. We prepared 300 cases for each model and four training data patterns for each model (a: 150 cases for one MR system, b: 300 cases for one MR system, c: 150 cases and augmentation data for one MR system, and d: 300 cases for two MR systems). The extension data were images of 150 cases rotated in the XY plane. The similarity between the images generated by the training and evaluation data in each group was evaluated using the peak signal-to-noise ratio (PSNR) and structural similarity (SSIM).

Results: For both MR systems, the PSNR and SSIM were higher for training dataset b than training dataset a. The PSNR and SSIM were lower for training dataset d.

Conclusion: MR image generation accuracy varied among training data patterns.

Purpose: Cerebral CT perfusion (CTP) summary maps classify the ischemic core, penumbra, and normal tissue from traditional parametric maps, which is a criterion for indicating thrombectomy. Since perfusion maps change when the CTP radiation dose is reduced, summary maps also might change. This study aimed to assess the noise characteristics of a summary map in simulation experiments.

Methods: We added various amounts of noise to a digital phantom and clinical CTPs, used Vitrea (Canon Medical Systems, Tochigi, Japan) to perform perfusion analysis, and assessed the relationship between the noise and cerebral blood volume (CBV), time to maximum (Tmax), and ischemic core and penumbra volumes.

Results: As the noise increased, the obtained CBV increased, the obtained Tmax shortened, and the obtained ischemic core and penumbra volumes decreased, which depended on the tissue's CBV and Tmax.

Conclusion: Under low-dose conditions, the ischemic core and penumbra volumes decreased, so the criteria for thrombectomy may differ from those for standard doses.

Purpose: In DRLs 2020, the entrance surface air kerma (Ka,e) was set to 17 mGy/min as the reference dose rate in fluoroscopy. But, Ka,e in fluoroscopy for different regions and Ka,e in exposure was not set. A multicenter survey was conducted to evaluate Ka,e by each area.

Methods: Ka,e for each area was analyzed for 79 facilities attending this survey (274 machines and 461 protocols). When the protocols were changed by the difference in disease, angiography, or IVR, the difference rate of Ka,e was evaluated. Ka,e before and after modifying the incident air kerma at the patient entrance reference point (Ka,r) and air kerma area product (P_KA) difference rate were calculated when protocols were changed, considering the DRLs 2020.

Results: There were dose differences in Ka,e by each area. Compared to DRLs 2020, 36 protocols from 13 facilities modified their protocols, all of which reduced Ka,e.

Conclusion: Although reducing Ka,e does not necessarily reduce Ka,r, and P_KA, comparison of Ka,e by each area is expected to optimize medical exposure protection, including evaluation of quality control.

Purpose: To investigate the effect of different source dwell positions on dose distribution in the treatment of cervical cancer with brachytherapy.

Methods: Treatment planning data for cervical cancer patients were used. Treatment plans were created at 1 mm intervals, varying up to 5 mm. For intracavitary brachytherapy and intracavitary and interstitial brachytherapy, the following dose parameters were evaluated: 90% high-risk clinical target volume (HR-CTV D_90%), rectum 2 cm³ dose (Rectum D_{2 cc}), small intestine 2 cm³ dose (Small D_{2 cc}), sigmoid colon 2 cm³ dose (Sigmoid D_{2 cc}), bladder 2 cm³ dose (Bladder D_{2 cc}), point A dose.

Results: In intracavitary brachytherapy, the HR-CTV D_90%, Rectum D_{2 cc}, Small D_{2 cc}, and Sigmoid D_{2 cc} doses increased as the source dwell position changed in the direction. On the other hand, the dose of Bladder D_{2 cc} increased when the source position changed in the outward direction. The same trend was observed in the case of intracavitary and interstitial brachytherapy.

Conclusion: It was shown that a 1 mm change in the source dwell position can affect the dose by up to 2% or more. The accuracy of the source dwell position is very important and should be checked before using the device.

Purpose: We investigated whether peripheral pulse synchronization (PPUS) can be an alternate method for electrocardiographic synchronization (ECGS) in measuring myocardial T1 values in cardiac magnetic resonance imaging (CMRI).

Methods: T1 map imaging was performed on 49 patients undergoing CMRI using the 5s (3s) 3s modified Look-Locker inversion recovery (MOLLI) method for both ECGS and PPUS. The short-axis images of basal, mid, and apical segments were obtained. The T1 map images were analyzed using an image processing system, and T1 values were obtained for each cardiac segment. To assess the degree of agreement between T1 values obtained from ECGS and PPUS, the Bland-Altman analysis and the estimating intraclass correlation coefficient (ICC) were performed for the average T1 value of the entire myocardium and T1 values of each cardiac segment. Also, to evaluate whether PPUS imaging is possible in the diastole phase, we measured the length of systole in the electrocardiogram and the length of transmission (R-R') from R in the electrocardiogram to R (R') in the pulse waveform.

Results: From the comparison of T1 values, a good agreement of ICC was confirmed between the ECGS and PPUS (whole myocardium: 0.97, apical: 0.93, mid: 0.98, and basal: 0.97). The results of the Bland-Altman analysis also indicated good agreement. Moreover, it was shown that the heart was imaged in the diastole phase even with the default scan parameters of PPUS.

Conclusion: Our results indicated that PPUS can be an alternate method for ECGS.

Purpose: In this study, we evaluated image quality and radiation dose reduction when a Copper (Cu) filter was added to hip joint X-ray imaging.

Methods: We measured effective energy without (0 mm) and with (0.1/0.2 mm) Cu-added filter at 70 kV, and we calculated soft tissue-bone contrast and signal-difference-to-noise-ratio (SDNR) under constant entrance surface dose. After that, we estimated the dose reduction rate.

Results: The effective energy was 32.07 keV for 0 mm Cu, 37.59 keV for 0.1 mm Cu, and 40.91 keV for 0.2 mm Cu. As the thickness of the Cu-added filter was increased, contrast decreased, but SDNR increased. The dose reduction rate in bone calculated measuring SDNR was 34% for 0.1 mm Cu and 47% for 0.2 mm Cu in max.

Conclusion: It was suggested that adding Cu filter to hip-joint X-ray imaging could reduce entrance surface dose while maintaining the image quality based on SDNR.