Analysis of Predictive Factors for Lung Injury after Forward-Planned Intensity-Modulated Radiotherapy in Whole Breast Irradiation / 한국유방암학회지

PURPOSE: This study was performed to assess frequency, timings of occurrence, and predictors of radiologic lung damage (RLD) after forward-planned intensity-modulated radiotherapy (FIMRT) for whole breast irradiation. METHODS: We retrospectively reviewed medical records of 157 breast cancer patients and each of their serial chest computed tomography (CT) taken 4, 10, 16, and 22 months after completion of breast radiotherapy (RT). FIMRT was administered to whole breast only (n=152), or whole breast and supraclavicular regions (n=5). Dosimetric parameters, such as mean lung dose and lung volume receiving more than 10 to 50 Gy (V10-V50), and clinical parameters were analyzed in relation to radiologic lung damage. RESULTS: In total, 104 patients (66.2%) developed RLD after whole breast FIMRT. Among the cases of RLD, 84.7% were detected at 4 months, and 15.3% at 10 months after completion of RT. More patients of 47 or younger were found to have RLD at 10 months after RT than patients older than the age (11.7% vs. 2.9%, p=0.01). In univariate and multivariate analyses, age >47 and V40 >7.2% were significant predictors for higher risk of RLD. CONCLUSION: RLD were not infrequently detected in follow-up CT after whole breast FIMRT. More detected cases of RLD among younger patients are believed to have developed at later points after RT than those of older patients. Age and V40 were significant predictors for RLD after whole breast intensity-modulated radiotherapy.

Development of Respiratory Training System Using Individual Characteristic Guiding Waveform / 의학물리

The purpose of this study was to develop the respiratory training system using individual characteristic guiding waveform to reduce the impact of respiratory motion that causes artifact in radiotherapy. In order to evaluate the improvement of respiratory regularity, 5 volunteers were included and their respiratory signals were acquired using the in-house developed belt-type sensor. Respiratory training system needs 10 free breathing cycles of each volunteer to make individual characteristic guiding waveform based on Fourier series and it guides patient's next breathing. For each volunteer, free breathing and guided breathing which uses individual characteristic guiding waveform were performed to acquire the respiratory cycles for 3 min. The root mean square error (RMSE) was computed to analyze improvement of respiratory regularity in period and displacement. It was found that respiratory regularity was improved by using respiratory training system. RMSE of guided breathing decreased up to 40% in displacement and 76% in period compared with free breathing. In conclusion, since the guiding waveform was easy to follow for the volunteers, the respiratory regularity was significantly improved by using in-house developed respiratory training system. So it would be helpful to improve accuracy and efficiency during 4D-RT, 4D-CT.

Development of Respiratory Signal Analysis Program for Accurate Phase Reassignment in 4D CT Reconstruction / 의학물리

Patient's respiration can have an effect on movement of tumor range and peripheral organs. Therefore, the respiratory signal was acquired by relation between external markers and movement of patient's abdomen during radiational therapy in order to minimize the effect of respiration. Based on this technique, many studies of rational therapy to irradiate at particular part of stable respiratory signals have executed and they have been clinically applied. Nevertheless, the phase-based method is preferred to the amplitude-based method for the rational therapy related to respiration. Because stabilization of the respiratory signal are limited. In this study, a in-house respiratory signal analysis program was developed for the phase reassignment and the analysis of the irregular respiratory signals. Various irregular respiratory patterns was obtained from clinical experimental volunteers. After then, the in-house program analyzed the factors affecting to phase assignment which is directly related to irradiated sector. Subsequently, accuracy of phase assignment was improved with removement of irregular signals by self-developed algorithm. This study is considered to be useful for not only image reconstruction and elevation of irradiating accuracy through phase assignment of RPM system but also analysis of respiratory signals. Moreover, development of 4D CT image is planed with phantom researches or clinical experiments based on this program.