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.

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: 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: 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.