Dosimetric and radiobiological comparison of Cyberknife and Tomotherapy in stereotactic body radiotherapy for localized prostate cancer.

BACKGROUND AND PURPOSE: As recent studies have suggested relatively low α/ß for prostate cancer, the interest in hypofractionated stereotactic body radiotherapy (SBRT) for prostate cancer is rising. The aim of this study is to compare dosimetric results of Cyberknife (CK) with Tomotherapy (HT) in SBRT for localized prostate cancer. Furthermore, the radiobiologic consequences of heterogeneous dose distribution are also analyzed. MATERIAL AND METHOD: A total of 12 cases of localized prostate cancer previously treated with SBRT were collected. Treatments had been planned and delivered using CK. Then HT plans were generated for comparison afterwards. The prescribed dose was 37.5Gy in 5 fractions. Dosimetric indices for target volumes and organs at risk (OAR) were compared. For radiobiological evaluation, generalized equivalent uniform dose (gEUD) and normal tissue complication probability (NTCP) were calculated and compared. RESULT: Both CK and HT achieved target coverage while meeting OAR constraints adequately. HT plans resulted in better dose homogeneity (Homogeneity index: 1.04±0.01 vs. 1.21±0.01; p = 0.0022), target coverage (97.74±0.86% vs. 96.56±1.17%; p = 0.0076) and conformity (new vonformity index: 1.16±0.05 vs. 1.21±0.04; p = 0.0096). HT was shown to predict lower late rectal toxicity as compared to CK. Integral dose to body was also significantly lower in HT plans (46.59±6.44 Gy'L vs 57.05±11.68 Gy'L; p = 0.0029). CONCLUSION: Based on physical dosimetry and radiobiologic considerations, HT may have advantages over CK, specifically in rectal sparing which could translate into clinical benefit of decreased late toxicities.

Retrospective Analysis for Dose Reduction to Organs at Risk with New Personalized Breast Holder (PERSBRA) in Left Breast IMRT.

This study evaluated dose differences in normal organs at risk, such as the lungs, heart, left anterior descending artery (LAD), right coronary artery, left ventricle, and right breast under personalized breast holder (PERSBRA), when using intensity-modulated radiation therapy (IMRT). This study evaluated the radiation protection offered by PERSBRA in left breast cancer radiation therapy. Here, we retrospectively collected data from 24 patients with left breast cancer who underwent breast-conserving surgery as well as IMRT radiotherapy. We compared the dose differences in target coverage and organs at risk with and without PERSBRA. For target coverage, tumor prescribed dose 95% coverage, conformity index, and homogeneity index were evaluated. For organs at risk, we compared the mean heart dose, mean left ventricle dose, LAD maximum and mean dose, mean left lung receiving 20 Gy, 10 Gy, and 5 Gy of left lung volume, maximum and mean coronary artery of the right, maximum of right breast, and mean dose. Good target coverage was achieved with and without PERSBRA. When PERSBRA was used with IMRT, the mean dose of the heart decreased by 42%, the maximum dose of LAD decreased by 26.4%, and the mean dose of LAD decreased by 47.0%. The mean dose of the left ventricle decreased by 54.1%, the volume (V20) of the left lung that received 20 Gy decreased by 22.8%, the volume (V10) of the left lung that received 10 Gy decreased by 19.8%, the volume (V5) of the left lung that received 5 Gy decreased by 15.7%, and the mean dose of the left lung decreased by 23.3%. Using PERSBRA with IMRT greatly decreases the dose to organs at risk (left lung, heart, left ventricle, and LAD). This study found that PERSBRA with IMRT can achieve results similar to deep inspiration breath-hold radiotherapy (DIBH) in terms of reducing the heart radiation dose and the risk of developing heart disease in patients with left breast cancer who cannot undergo DIBH.

Skin Surface Dose for Whole Breast Radiotherapy Using Personalized Breast Holder: Comparison with Various Radiotherapy Techniques and Clinical Experiences.

PURPOSE: Breast immobilization with personalized breast holder (PERSBRA) is a promising approach for normal organ protection during whole breast radiotherapy. The aim of this study is to evaluate the skin surface dose for breast radiotherapy with PERSBRA using different radiotherapy techniques. MATERIALS AND METHODS: We designed PERSBRA with three different mesh sizes (large, fine and solid) and applied them on an anthropomorphic(Rando) phantom. Treatment planning was generated using hybrid, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques to deliver a prescribed dose of 5000 cGy in 25 fractions accordingly. Dose measurement with EBT3 film and TLD were taken on Rando phantom without PERSBRA, large mesh, fine mesh and solid PERSBRA for (a) tumor doses, (b) surface doses for medial field and lateral field irradiation undergoing hybrid, IMRT, VMAT techniques. RESULTS: The tumor dose deviation was less than five percent between the measured doses of the EBT3 film and the TLD among the different techniques. The application of a PERSBRA was associated with a higher dose of the skin surface. A large mesh size of PERSBRA was associated with a lower surface dose. The findings were consistent among hybrid, IMRT, or VMAT techniques. CONCLUSIONS: Breast immobilization with PERSBRA can reduce heart toxicity but leads to a build-up of skin surface doses, which can be improved with a larger mesh design for common radiotherapy techniques.

Dosimetry audits in Taiwan radiotherapy departments.

Objectives: This study examines the practice of the regulation of Standards for Medical Exposure Quality Assurance (SMEQA) in Taiwan based on on-site quality audit for radiation therapy systems from 2016 to 2019. Methods: 81 radiation therapy departments, 141 linacs, 9 γ knife systems, 34 high dose rate brachytherapy systems, 20 Tomotherapys, and 6 Cyberknives were audited yearly. Data collection and analysis for each institute's documents including QA procedure, ion chamber and electrometer calibration reports, and a questionnaire relating to machine type and staffing, were requested first and reviewed by auditors. On-site SMEQA core item measurements, including beam output, beam profile and energy constancy for external beam therapy systems, and the source strength, positioning, and timer accuracy for brachytherapy systems were audited second. More than 300 photon beams and more than 400 electron beams were measured each year. Results: There were approximately 8.9 radiotherapy units per million population, and 1.2 medical physicists per unit in Taiwan. For the output measurements, more than 78 and 75% of the photon beams and electron beams, respectively, from linacs were with deviations within ±1.0%. Photon beams have lower beam quality measurement deviations than electron beams. Including in-plane and cross-plane measurements, more than 90 and 85% photon and electron beams, respectively, were with flatness consistency within 1.0%. All audit measurements were within the SMEQA acceptance criteria. Conclusions: According to SMEQA regulations on-site QA audits were successfully carried out from 2016 to 2019 for all Taiwan radiotherapy units. The measurement results showed high quality machine performance in Taiwan. Advances in knowledge: Dosimetry audits with directly acquired measurement readings have lower uncertainties; allow immediate feedback, discussion, and adjustment in a timely manner. In addition to regulation system establishment and education and training implementation, the machine quality is closely related to machine maintenance implementation.

Continued use of an interactive computer game-based visual perception learning system in children with developmental delay.

This study developed an interactive computer game-based visual perception learning system for special education children with developmental delay. To investigate whether perceived interactivity affects continued use of the system, this study developed a theoretical model of the process in which learners decide whether to continue using an interactive computer game-based visual perception learning system. The technology acceptance model, which considers perceived ease of use, perceived usefulness, and perceived playfulness, was extended by integrating perceived interaction (i.e., learner-instructor interaction and learner-system interaction) and then analyzing the effects of these perceptions on satisfaction and continued use. Data were collected from 150 participants (rehabilitation therapists, medical paraprofessionals, and parents of children with developmental delay) recruited from a single medical center in Taiwan. Structural equation modeling and partial-least-squares techniques were used to evaluate relationships within the model. The modeling results indicated that both perceived ease of use and perceived usefulness were positively associated with both learner-instructor interaction and learner-system interaction. However, perceived playfulness only had a positive association with learner-system interaction and not with learner-instructor interaction. Moreover, satisfaction was positively affected by perceived ease of use, perceived usefulness, and perceived playfulness. Thus, satisfaction positively affects continued use of the system. The data obtained by this study can be applied by researchers, designers of computer game-based learning systems, special education workers, and medical professionals.

Up-regulation of antioxidant enzymes and coenzyme Q(10) in a human oral cancer cell line with acquired bleomycin resistance.

Bleomycin (BLM) is an anti-cancer drug that can induce formation of reactive oxygen species (ROS). To investigate the association between up-regulation of antioxidant enzymes and coenzyme Q(10) (CoQ(10)) in acquired BLM resistance, one BLM-resistant clone, SBLM24 clone, was selected from a human oral cancer cell line, SCC61 clone. The BLM resistance of SBLM24 clone relative to a sub-clone of SCC61b cells was confirmed by analysis of clonogenic ability and cell cycle arrest. CoQ(10) levels and levels of Mn superoxide dismutase, glutathione peroxidase 1, catalase and thioredoxin reductase 1 were augmented in SBLM24 clone although there was also a mild increase in the expression of BLM hydrolase. Suppression of CoQ(10) levels by 4-aminobenzoate sensitized BLM-induced cytotoxicity. The results of suppression on enhanced ROS production by BLM and the cross-resistance to hydrogen peroxide in SBLM24 clone further demonstrated the development of adaptation to oxidative stress during the formation of acquired BLM resistance.