Yongkan Ki

Sang-Il Pak, Dong Woon Kim, Hojeong Lee, Kyeonghyo Lee, Ji Hyeon Joo, Dongchan Kim, Donghyun Kim, Jiho Nam, Dahl Park, Wontaek Kim, Yongkan Ki. Progress in Medical Physics 2026;37:108-16. https://doi.org/10.14316/pmp.2026.37.3.108

Background: This study evaluates relapse patterns and treatment outcomes in oral cavity carcinoma (OCC) patients treated with flap‐sparing radiotherapy (RT). Methods: Patients treated with surgery and immediate free‐flap reconstruction followed by RT due to OCC between 2018 and 2024 were analyzed retrospectively. During target volume delineation, the high‐risk clinical target volume (CTV) was the native tissue‐flap interface with an additional isotropic margin of 10 mm. We estimated the cumulative incidence and geometric patterns of local failures. Results: Thirty‐four patients matched the inclusion criteria. Median follow‐up was 44 months. Three patients experienced local recurrences. Two relapses occurred at the native tissue‐flap junction, with no intraflap failure. Three cases of Grade 3 acute oral mucositis, two cases of late Grade 3 dysphagia, and two cases of osteoradionecrosis of the jaw were observed. Clinically significant flap‐related complication was not reported. Conclusion: No intra‐flap local recurrence was observed after flap‐sparing RT. The entire flap does not need to be intentionally covered in the CTV. Further investigation of planning optimization for the reconstructed flap is needed.

Background/Objectives: The safety of hypofractionated postmastectomy radiotherapy (HF-PMRT) in patients undergoing implant-based breast reconstruction remains uncertain because of concerns regarding radiation-related reconstructive complications. We conducted a systematic review and meta-analysis to compare reconstruction-related complications following HF-PMRT versus conventionally fractionated (CF) PMRT. Methods: PubMed, Cochrane Library, and EMBASE databases were searched through August 2025 following PRISMA guidelines. Studies comparing HF-PMRT with CF-PMRT in patients undergoing implant-based breast reconstruction were included. Outcomes were capsular contracture, implant or tissue expander removal, infection, and wound dehiscence. Risk of bias was assessed using RoB 2 and ROBINS-I tools. Odds ratios (ORs) with 95% confidence intervals (CIs) were pooled using the Mantel–Haenszel method. Subgroup analyses were performed by reconstruction stage (tissue expander vs. permanent implant). Results: Seven studies (n = 2200 patients; 1153 HF, 1047 CF) were analyzed, comprising two randomized controlled trials and five retrospective cohort studies. HF-PMRT was associated with a significantly lower risk of capsular contracture (OR 0.65, 95% CI 0.47–0.92) and wound dehiscence (OR 0.39, 95% CI 0.16–0.94) than CF-PMRT. Implant or tissue expander removal (OR 0.90, 95% CI 0.67–1.22) or infection (OR 0.98, 95% CI 0.67–1.44) did not differ. In subgroup analyses, reduction in capsular contracture was most evident when PMRT was delivered during the tissue expansion phase. Conclusions: These findings suggest that moderate hypofractionation is a reasonable fractionation option for implant-based breast reconstruction, with no evidence of increased reconstructive complications, although the certainty of evidence was limited, and prospective validation is warranted.

This study aimed to evaluate the dosimetric performance and robustness of volumetric modulated arc therapy (VMAT) planning techniques-planning target volume with internal margin (INT), auto flash (AF), and virtual bolus (VB)-under simulated geometric changes during whole-breast radiotherapy. Nine patients with left-sided breast cancer were included. Three planning techniques were compared: INT with a 5-mm skin-sparing internal margin, AF with a 1-cm automatic skin flash margin, and VB with a 5-mm optimization bolus applied only during the planning. Respiratory motion was simulated by shifting the plan center (± 3 mm and ± 5 mm) and recalculating the dose distributions. Under static conditions, all plans provided adequate target coverage, with planning target volume (PTV) V95% values of 96.45% (INT), 97.35% (AF), and 98.19% (VB). Under breast swelling of up to 5 mm, AF maintained the most stable coverage (PTV V95% = 99.10%), outperforming VB (95.02%) and INT (92.31%) (p < 0.001). In simulated incomplete inspiration (5 mm), VB showed superior robustness, achieving a PTV V95% of 90.46% compared with AF (85.30%) and INT (85.08%) (p = 0.008). AF met the ideal criteria in all cases under swelling conditions, whereas the VB was more effective against suboptimal respiration. In VMAT breast radiation therapy (RT), the conventional INT approach was the least robust against variations, and additional techniques are required. AF effectively compensates for breast swelling, whereas VB preserves the target coverage under insufficient breath-hold conditions. Surface-guided radiation therapy (SGRT) and visual guidance are recommended to ensure accurate treatment.

Background: Deep-inspiration breath-hold (DIBH) is a helpful technique during radiation therapy (RT) for breast cancer that can protect vital organs and deliver a more accurate treatment dose to the target. A laser sensor-based position monitoring system is developed to measure the absolute position of an object and achieve high accuracy and reproducibility during ...

Background/Objectives: Fluoroscopy has been widely adopted in interventional pulmonology, as it facilitates real-time visualization of the bronchoscope, endobronchial ultrasound, and biopsy tools during procedures. The purpose of this study was to evaluate the effectiveness of radiation shields in minimizing scattered X-ray dose to the bronchoscopist in a phantom study and to determine the dose of scattered X-ray dose to medical staff with radiation shields in clinical application. Methods: An anthropomorphic torso phantom was positioned on the fluoroscopic table between the C-arm X-ray tube and the image detector to mimic bronchoscopic operations. Upper and lower body lead shields were used to examine the effectiveness of radiation shielding. Scatter radiation rates were assessed at a first operator location using real-time dosimeters with and without protective devices. In clinical application, the scattered X-ray dose of the first operator and main assistant was measured using wearable radiation dosimeters during 20 procedures. Results: In the phantom study, scattered radiation without shielding was 266.34 ± 8.86 μSv/h (glabella), 483.90 ± 8.01 μSv/h (upper thorax), 143.97 ± 8.20 μSv/h (hypogastrium), and 7.22 ± 0.28 μSv/h (ankle). The combination of upper and lower body lead shields reduced the scattered X-ray dose by 98.7%, 98.3%, 66.2%, and 79.9% at these levels, respectively. In clinical application, mean scattered X-ray dose rates were 0.14 ± 0.05 μSv/procedure (eye), 0.46 ± 0.51 μSv/procedure (chest), 0.67 ± 0.50 μSv/procedure (hypogastrium), and 1.57 ± 2.84 μSv/procedure (assistant’s wrist). Conclusions: The combination of radiation shields significantly reduced the scattered X-ray dose at the operator site in the phantom study. The scattered X-ray dose to medical staff during bronchoscopy can be kept at a low level with the aid of a shielding system.

Hojeong Lee, Dong Woon Kim, Ji Hyeon Joo, Yongkan Ki, Wontaek Kim, Dahl Park, Jiho Nam, Dong Hyeon Kim, Hosang Jeon. Progress in Medical Physics 2024;35:52-7. https://doi.org/10.14316/pmp.2024.35.2.52

Background: Modern radiotherapeutic techniques, such as intensity‐modulated radiation therapy or stereotactic body radiotherapy, require high‐dose delivery precision. However, the precise localization of tumors during patient respiration remains a challenge. Therefore, it is essential to investigate effective methods for monitoring respiration to minimize potential complications. Despite several systems currently in clinical use, there are drawbacks, including the complexity of the setup, the discomfort to the patient, and the high cost.Purpose: This study investigated the feasibility of using a novel pressure sensor array (PSA) as a tool to monitor respiration during radiotherapy treatments. The PSA was positioned between the treatment couch and the back of the patient lying on it and was intended to overcome some limitations of current methods. The main objectives included assessing the PSA's capability in monitoring respiratory behavior and to investigate prospective applications that extend beyond respiratory monitoring.Methods: A PSA with 31 pressure‐sensing elements was used in 12 volunteers. The participants were instructed to breathe naturally while lying on a couch without any audio or visual guidance. The performance of the PSA was compared to that of a camera‐based respiratory monitoring system (RPM, Varian, USA), which served as a reference. Several metrics, including pressure distribution, weight sensitivity, and correlations between PSA and RPM signals, were analyzed. The PSA's capacity to provide information on potential applications related to patient stability was also investigated.Results: The linear relationship between the weight applied to the PSA and its output was demonstrated in this study, confirming its sensitivity to pressure changes. A comparison of PSA and RPM curves revealed a high correlation coefficient of 0.9391 on average, indicating consistent respiratory cycles. The PSA also effectively measured the weight distribution at the volunteer's back in real‐time, which allows for monitoring the patient's movements during the radiotherapy.Conclusion: PSA is a promising candidate for effective respiratory monitoring during radiotherapy treatments. Its performance is comparable to the established RPM system, and its additional capabilities suggest its multifaceted utility. This paper shows the potential use of PSA for patient monitoring in radiotherapy and suggests possibilities for further research, including performance comparisons with other existing systems and real‐patient applications with respiratory training.