Browsing by Author "Vieira, Sandra"
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- Calypso’s array attenuationPublication . Silva, Célia; Mateus, Dalila; Vieira, Sandra; Rodrigues, Milton; Eiras, Margarida; Greco, CarloIntroduction: The Calypso 4D Localization System gives the possibility to track the tumour during treatment, with no additional ionising radiation delivered. To monitor the patient continuously an array is positioned above the patient during the treatment. We intend to study, for various gantry angles, the attenuation effect of the array for 6- and 10 MV and flattening filter free (FFF) 6- and FFF 10 MV photon beams. Materials and methods: Measurements were performed using an ion chamber placed in a slab phantom positioned at the linac isocenter for 6 MV, 10 MV, FFF 6 MV and FFF 10 MV photon beams. Measurements were performed with and without array above the phantom for 0°, 10°, 20°, 40° and 50° beam angle for a True Beam STx linac, for 5×5 and 10×10 and 15×15 cm2 field size beams to evaluate the attenuation of the array. A VMAT treatment plan was measured using an ArcCheck with and without the array in the beam path. Results and discussion: Attenuation measured values were up to 3%. Attenuation values were between 1 and 2% with the exception of the 30°–50° gantry angles which were up to 3.3%. The ratio values calculated in the ArcCheck for relative dose and absolute dose 10 were both 1·00. Conclusion: Attenuation of the treatment beam by the Calypso array is within acceptable limits.
- Calypso® 4D localization system: a reviewPublication . Silva, Célia; Mateus, Dalila; Eiras, Margarida; Vieira, SandraPurpose: Calypso® 4D Localization System is a system based on electromagnetic transponders detection enabling precise 3D localization and continuous tracking of tumour target. This review intended to provide information in order to (1) show how Calypso® 4D Localization System works, (2) to present advantages and disadvantages of this system, (3) to gather information from several clinical studies and, finally, (4) to refer Calypso® System as a tool in dynamic multileaf collimator studies for target motion compensation. Methods: A structured search was carried out on the B-On platform. The keywords used in this research were ‘Calypso’, ‘Transponder’, ‘Electromagnetic Localization’, ‘Electromagnetic Tracking’, ‘Target Localization’, ‘Intrafraction Motion’ and ‘DMLC’. Review: Treatment the implanted transponders are excited by an electromagnetic field and resonate back. These frequencies are detected and Calypso® software calculates the position of the transponders. If the movement detected is larger than the limits previously defined, irradiation can be stopped. The system has been proven to be submillimetre accurate. Discussion: Calypso® System has been presented as an accurate tool in prostate radiotherapy treatments. The application of this system to other clinical sites is being developed. Conclusion: The Calypso® System allows real-time localization and monitoring of the target, without additional ionising radiation administration. It has been a very useful tool in prostate cancer treatment.
- Radiotherapy couches: is kevlar an obstacle? Attenuation study of three different tabletopsPublication . Silva, Célia; Mateus, Dalila; Vieira, Sandra; Rodrigues, Milton; Eiras, Margarida; Greco, CarloIntroduction: Treatment tabletops are usually made of carbon fibre due to its high mechanical strength and rigidity, low specific density, extremely light and regularly considered radio translucent. Our clinic acquired a Calypso 4D Localization System where electromagnetic (EM) frequencies to detect implanted transponders in the patient are used. Carbon fibre is an electrical conductive material which interferes with EM frequencies. Therefore, in order to be able to use the Calypso System the carbon fibre tabletop in the treatment room must be replaced. It is our goal to determine the attenuation of the new, non-carbon fibre, tabletop in treatment delivery. Materials and Methods: Measurements were performed using an ionisation chamber inserted in a slab phantom positioned at the isocenter for 6, 10 MV, 6 and 10 flattening filter-free (FFF) MV photon beams. These measurements were performed with and without tabletop for 0°, 30° and 60° beam angle for a True Beam STx linac, for 5×5 cm2 and 10×10 cm2 field size beams. The attenuation was calculated for each measurement for each tabletop. Results: At 0° incidence on the Exact IGRT Couch, the measured attenuation for 10×10 cm2 was 2·8 and 2·1% for 6 and 10 MV beams, respectively. For the same field size was measured 3·3 and 2·6% attenuation for 6 and 10 FFF MV beams, respectively. At the same incidence and regarding the other tabletops, the calculated attenuation is lower. For 10×10 cm2 field, there is 2·0, 1·4, 2·1 and 2·6% attenuation for 6, 10 MV, 6 and 10 FFF MV energy beams on the kVueTM Universal Couch. For the KvueTM Calypso® Couch 10×10 cm2 irradiation field, the measurements were 1·6, 1·3, 1·9 and 1·5%, respectively. This tendency is observed for all gantry angles. Discussion: The attenuation outputs were definitely higher for the Varian Exact IGRT Couch when compared with the kVue tabletops. The attenuation measurements for the kVue tabletops were closer to each other. Nevertheless kVueTM Calypso® Varian tabletop showed smaller mean attenuation of the beams than kVueTM Universal Tip Insert for all measurements. Conclusions: There was no loss in treatment quality administration due to beam attenuation in the tabletop when tabletops were exchanged because of Calypso system integration. There is no need to change between kVue tabletops whenever there is a regular treatment or a Calypso System guided treatment.