Validation of lung stereotactic ablative body radiotherapy (SABR) treatments with flattening filter free (FFF) beams

Validation of lung stereotactic ablative body radiotherapy (SABR) treatments with flattening filter free (FFF) beams

Abstracts / Physica Medica 32 (2016) 284–339 INTERFRACTIONAL SETUP CORRECTIONS USING HEXAPOD ROBOTIC COUCH FOR VMAT HEAD AND NECK TREATMENTS E.M. Amb...

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Abstracts / Physica Medica 32 (2016) 284–339

INTERFRACTIONAL SETUP CORRECTIONS USING HEXAPOD ROBOTIC COUCH FOR VMAT HEAD AND NECK TREATMENTS E.M. Ambroa Rey *, R. Gómez Pardos, D. Navarro Giménez, A. Ramirez Muñoz, M. Colomer Truyols Medical Physics Unit, Radiation Oncology Department, Consorci Sanitari de Terrassa, Barcelona, Spain ⇑ Corresponding author. Introduction. Inaccurate alignment of the radiation beam with the patient can lead to critical organs to receive an unwanted high dose or the tumor to receive a reduced dose producing a loss in tumor control. Purpose. To establish the interfractional setup error, for VMAT head and neck patients, using a kilovoltage cone beam CT (CBCT) and a robotic treatment couch (Hexapod) for accurate patient positioning in six degrees of freedom. Materials and methods. A total of 315 fractions from 10 H&N patients were evaluated. The Hexapod corrected the misalignments and a pre-treatment CBCT verification was obtained. For each patient the daily variations of the three principal axes (X, Y and Z) and three rotational movements (pitch, roll, and yaw) were extracted. The following parameters were calculated: the mean of the setup corrections (M), the standard deviation (random error) and the standard deviation of all the means measured for each patient (systematic error). Results. The overall mean displacements are (0.0, 0.5, 0.3) mm for the translations and (0.60, 0.45, 0.11) degrees for the rotations. The random errors are (2.2, 2.3, 2.6) mm and (1.29, 1.35, 1.28) degrees. The systematic errors are (1.7, 1.6, 2.0) mm and (0.86, 1.01, 0.98) degrees. Conclusion. The M values were equal or less than 0.5 mm for the translational axes. We obtained relatively larger random errors than systematic errors in both translational and rotational movements. This result agrees with the literature for head and neck displacements. Disclosure. None declared. http://dx.doi.org/10.1016/j.ejmp.2016.07.110

VALIDATION OF LUNG STEREOTACTIC ABLATIVE BODY RADIOTHERAPY (SABR) TREATMENTS WITH FLATTENING FILTER FREE (FFF) BEAMS Ioannis Floros *, Anna Bangiri, Greg Jolliffe, Jonathan Littler, Elizabeth Harron, Angela Mckenna, Keith Langmack Nottingham University Hospitals NHS Trust, United Kingdom Corresponding author.



Introduction. To commission and dosimetrically validate MONACO TPS for lung SABR treatments using FFF beams. Materials and methods. EBT3 films were used and the region of interest was the Field Edge Area (FEA): 20–80% of dose maximum. The film was placed in water and lung phantom and three field sizes were used. Profiles were measured from the film and the FEA was calculated and compared to that from the TPS. Clinical plans were created using three fractionation regimes (54Gy/3#, 55Gy/5#, 60Gy/8#) for each of four patients. Each plan was delivered twice on the Quasar phantom, with a breathing trace and statically, and on the Delta4 phantom. Results. The profile differences between films and Monaco TPS were primarily within 1mm for all field sizes and at all depths.

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The largest difference in lung was 0.7, 1.2 and 1.0 mm in the crossline direction for 10  10, 5  5, and 2  2 cm2 respectively. The respective differences in the inline direction were 2.2, 1.2 and 1.0 mm. The FEA calculated with Monaco was overall broader than that measured. All the delivered plans had a gamma pass rate better than 98.3% (3 mm/3%)on the Delta4. The Quasar results had a mean absolute dose difference of 1.1% (S.D. 0.7) and 1.3% (S.D. 0.9) for the static and the breathing traces respectively. Conclusion. The excellent agreement with EBT3 indicates that Monaco satisfactorily predicts profiles in lung. The differences observed could be due to partial volume effect. FFF Lung SABR treatments were fully verified and excellent agreement was found with the Quasar and the Delta4 for all clinical plans. http://dx.doi.org/10.1016/j.ejmp.2016.07.111

PATIENT EFFECTIVE DOSE DURING PACEMAKER IMPLANTATION AT A FLAT PANEL AND IMAGE INTENSIFIER ANGIOGRAPHY SYSTEM E. Vlastou a,*, J. Antonakos a, E. Simeonidou b, P. Flevari b, D. Leftheriotis b, S. Deftereos b, E. Efstathopoulos a a

2nd Department of Radiology, University of Athens, Greece Unit of Interventional Cardiology, 2nd Department of Cardiology, University of Athens, Greece ⇑ Corresponding author. b

Introduction. Pacemaker implantation is a minimally invasive technique performed under fluoroscopic guidance. Purpose. This study aims to compare effective dose (ED) delivered to patients at pacemaker implantation procedures by two angiographic systems of different image capture technology; one with flat panel detector (FPD) and one with image intensifier (II). Materials and methods. A retrospective analysis of 62 procedures performed at Attikon University Hospital of Athens has been conducted. Data concerning dose area product (DAP), fluoroscopy time and patient’s weight and height have been collected. The ED has been calculated, multiplying DAP with a conversion factor of 0.2 mSv/(Gy⁄ cm2) and the results have been divided in categories accordingly to patients’ BMI and fluoroscopy time. Results. ED, presented as median and range values, for normal, over weighted and obese patients that have been operated under a FPD X-ray system, in a fluoro time less than five minutes was 0.49 mSv (0.09–1.1 mSv), 0.67 mSv (0.4–1.2 mSv) and 1.18 mSv (1–1.3 mSv) respectively. The corresponding values for an II system were 0.50 mSv (0.5–0.8 mSv), 2.49 mSv (1.86–3.58 mSv) and 1.70 mSv (0.8–3.3 mSv). For fluoro time greater than five minutes in FPD imaging, ED for the three BMI categories was 1.57 mSv (0.7–3.7 mSv), 0.74 mSv (0.45–1.26 mSv) and 2.93 mSv (1.78– 3.45 mSv), while for the II angiography system ED was 12.29 mSv (1.88–49.27 mSv), 28.36 mSv (6.27–15.43 mSv) and 35.27 mSv (5.84–158,73 mSv). Conclusion. Obtained results indicate statistically significant higher radiation burden associated with II system compared to FPD system used for pacemaker’s implantations (p < 0.05). Disclosure. All authors confirm that none relationship may bias this presentation. http://dx.doi.org/10.1016/j.ejmp.2016.07.112