46 cc. Smaller volumes showed a decrease of 23%. No evidence of substantial random fiducial marker migration was found. The COM displacement vector was 1.0 ± 3.5 mm. Both findings suggest that the gold markers positions were representative for the lump cavity position. Surgical clips showed the same behaviour. In the EPID images correlation between the bony and fiducial landmarks was poor in the cranial-caudal direction (R2=0.3). Correlation in the other directions was reasonable (R2 = 0.6). 15.18. Daily dose variation during prone breast helical tomotherapy for large- breast patients: planned dose verses actual delivered dose Presenter: Wai Man Lee, Department of Radiotherapy, Hong Kong Sanatorium and Hospital Authors: Wai Man LEE, George CHIU, Winky Wing Ki FUNG Introduction: Conventional supine radiotherapy for large-breast patients often faces difficulties in dosimetry as the breast is enfolding around heart and ipsilateral lung, resulting in worse dose homogeneities. The underlying skin folds also give worse skin reactions. Other concerning factors e.g. the necessarily large target area due to large breast size, daily setup variabilities and respiratory motion also lead to a larger planning target volume (PTV), hence increasing doses to contralateral breast, lungs and heart. Positioning improvement can be done by alternative immobilization method, i.e. patient to lie prone on a dedicated prone setup device. Since the breast target is hanging down away from the chest, lung doses can be reduced with improved dose homogeneity within the breast tissues. Also, adverse skin reactions can be reduced by minimizing skin folds. However in prone position, heart gets closer to the chest wall, thus becoming disadvantageous in cases which PTV involves deep-lying breast tissues. Setup accuracy may also be lowered due to patient discomfort. In helical tomotherapy, the highly conformal intensity modulation allows optimal dose escalation in PTV and better sparing to organs at risk (OARs). Pretreatment megavoltage computed tomographic (MVCT) scan allows position verification and with the accurate CT number obtained, recalculation of actual delivered dose becomes feasible. In order to investigate the effect of setup errors on actual delivered dose in prone breast treatments using helical tomotherapy, this study was conducted to determine the daily deviations between the planned and actual doses to the PTV and OARs in large-breast patients. Methods: Data from 249 out of 250 fractions in 10 patients, prescribed 50Gy to 95%PTV, were used. With daily MVCT, actual dose per fraction was recalculated. Daily actual and planned doses to specific DVH points were recorded and compared by paired t-test. Results: The mean 95%PTV actual dose was less than planned. Concerned OARs DVH points showed decreased mean actual doses except heart. PTV and OARs DVH points showed small absolute dose or volume differences (<0.2Gy;<1%) yet statistically significant (p<0.05). Statistically different daily planned and actual doses implied suboptimal prone setup accuracy. Higher mean actual dose to heart implied less-favored sparing. Yet, results might not do clinical significance as absolute dose differences were small. 15.19. Investigating the potential use of MR-simulator in motion management of liver radiotherapy Presenter: Jacky Tsz Lung Wong, Hong Kong Sanatorium Hospital Authors: Jacky Wong, George Chiu & Imen Ku Introduction: Liver is located directly inferior to the diaphragm and its position is strongly influenced by breathing. The motion of liver tumor has been studied and was reported to be from 5 to 50 mm depending on the location of the tumor in relation to the diaphragm. Other than geometrical variation, the liver tumor can also be deformed as a result from the breathing motion intra and inter-fractionally. Furthermore, for the tumors in liver, the extent of motion depends on individual position within liver,degree of disease, size of tumor, and surgical history. Therefore, accurate target localization is one of the largest challenges in radiotherapy in liver. The GE MR-simulator (Optima MR450w 1.5T) is a clinical MR system featured by its wide bore and larger field of view, a detachable flattop couch enable transporting patient without repositioning. All these features allow the use of actual treatment setup during MR imaging, which is the same as CT-sim, thus it is called MR-simulator. MR has superior spatial resolution and is excellent in soft tissue imaging. Liver is a soft tissue structure in which its tumor can be difficult to delineate in traditional planning CT scan. With the use of the MR simulator, patients can be reproduced in the same treatment position for optimal image registration and tumor motion tracking during the course of radiotherapy. As it does not involve radiation, repeated MR scan inter-fractionally can be performed to manage the motion of the liver tumor throughout the entire treatment duration. This study aims to investigate the motion of the liver tumor can be managed by the use of rapid MR cine scan in MR simulator. Methods: Two patients with liver tumor were studied. They were instructed to maintain regular free breathing during the whole scan in the same treatment position. Rapid 2D sagittal and coronal cine MRI through the centre of the tumor were acquired. Results: This initial result on liver tumor motion has demonstrated the tumor moves in 3 dimensional in relation to time. With the use of rapid MR scan, the motion of the liver tumor can be tracked in continuous breathing cycle. This is more favourable when compared with 4DCT which only captured the motion in several breathing cycle. The use of MR in motion management of liver does not involve radiation and are safe to use in repeated motion management monitoring especially in liver tumor cases. 15.20. Randomized controlled trial of the effects of the efeedback on breast cancer patients knowledge of radiotherapy (RT) Presenter: Mervi Siekkinen, University of Turku, Finland Authors: Mervi Siekkinen, S Pyrhönen, H Leino-Kilpi Introduction: The patient education providing knowledge of radiotherapy (RT) is an important part in quality of care at RT centre. However, breast cancer (BC) patients have reported to unmet knowledge expectations. Due to their interest in health information seeking through internet there is a challenge to develop effective electronic (e-) patient education. An evaluation was done to measure the effect of the e-feedback knowledge of RT intervention (e-Re-Know) on knowledge of RT process, possible side effects, side effect self-care and lifestyles and RT patients. The e-Re-Know delivered pre RT via e-mail was aim to improve knowledge of RT and support patients to be empowered. Methods: A randomized controlled study was used. BC patients (n=126) in RT were assigned into intervention (e-Re-Know and standard education) and control (standard education) group. The outcome was knowledge level measured before and 3 months after RT period. Results: The increase in knowledge level was significantly higher in the intervention than in the control group after adjustment for baseline knowledge level. The e-Re-Know delivered pre RT was effective on knowledge for breast cancer patients; and consequently on quality of care in RT. Patients benefited mainly of the knowledge of side effects self-care. In future, the women with breast cancer should use the e-Re-Know for adjusting in their everyday life not only during but also after treatments. 15.21. How can the radiation therapist support cancer patients undergoing head and neck radiotherapy? Presenter: Helen Egestad, UiT, The Artic University og Norway Author: Helen Egestad Introduction: Head and neck cancer patients experience a high level of emotional distress in the radiation treatment period. They are already in a vulnerable situation when they enter the radiation therapy department, and therapy can induce further fears, including concerns about the efficacy of treatment, about side-effects, dysfunction and accuracy. Several studies have shown that patients undergoing radiation therapy have fears, anxieties, and stress related to the therapy, but few studies have investigated living with head and neck cancer during radiotherapy from the patients’ perspective. Studies have rarely focused on the whole experience of radiation treatment. Head and neck cancer patients' radiation treatment is complex. The illness and the treatment have an enormous impact on the patients’ daily living. It is important to gain more knowledge about patients’ experiences when they undergo radiation treatment. Head and neck cancer patients have daily visits in 5-7 weeks in the radiation department. Qualitative studies have shown that the radiation therapist can reduce patients’ distress when they give information and express understanding. But there is a lack of research that describes what the radiation therapists exactly do when they meet the patients leading to the patient's stress decreases. The aim of this study was to describe what radiation therapists do and say in order to help patients through the radiation treatment period.
ISRRT | Book Of Abstracts
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