Geometric and dosimetric accuracy and imaging dose of the real-time tumour tracking system of a gimbal mounted linac. Issue 5 (July 2015)

• Record Type: Journal Article
• Authors: Garibaldi, Cristina; Russo, Stefania; Ciardo, Delia; Comi, Stefania; Seregni, Matteo; Fassi, Aurora; Piperno, Gaia; Ferrari, Annamaria; Pansini, Floriana; Bazani, Alessia; Ricotti, Rosalinda; Jereczek-Fossa, Barbara Alicja; Baroni, Guido; Orecchia, Roberto
• Is Part Of: Physica medica. Volume 31:Issue 5(2015)
• Page Start: 501
• Page End: 509
• Publication Date: 2015-07
• Subjects: Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2015.04.001
• Languages: English
• ISSNs: 1120-1797

Abstract

<abstract xml:lang="en" abstract-type="author" id="abs0010"> <title id="sectitle0010">Abstract</title> <sec> <title id="sectitle0015">Purpose</title> <p id="abspara0010">To suggest a comprehensive testing scheme to evaluate the geometric and dosimetric accuracy and the imaging dose of the VERO dynamic tumour tracking (DTT) for its clinical implementation.</p> </sec> <sec> <title id="sectitle0020">Methods</title> <p id="abspara0015">Geometric accuracy was evaluated for gantry 0° and 90° in terms of prediction (E<sub>P</sub>), mechanical (E<sub>M</sub>) and tracking (E<sub>T</sub>) errors for sinusoidal patterns with 10 and 20 mm amplitudes, 2–6 s periods and phase shift up to 1 s and for 3 patient patterns. The automatic 4D model update was investigated simulating changes in the breathing pattern during treatment.</p> <p id="abspara0020">Dosimetric accuracy was evaluated with gafchromic films irradiated in static and moving phantom with and without DTT. The entrance skin dose (ESD) was assessed using a solid state detector and gafchromic films.</p> </sec> <sec> <title id="sectitle0025">Results</title> <p id="abspara0025">The RMS of E<sub>P</sub>, E<sub>M</sub>, and E<sub>T</sub> were up to 0.8, 0.5 and 0.9 mm for all non phased-shifted motion patterns while for the phased-shifted ones, E<sub>P</sub> and E<sub>T</sub> increased to 2.2 and 2.6 mm. Up to 4 updates are necessary to restore a good correlation model, according to type of change.</p> <p id="abspara0030">For 100 kVp and 1 mA s X-ray beam, the ESD per portal due to 20 s fluoroscopy was 16.6 mGy, while treatment verification at a frequency of 1 Hz contributed with 4.2 mGy/min.</p> </sec> <sec> <title id="sectitle0030">Conclusions</title> <p id="abspara0035">The proposed testing scheme highlighted that the VERO DTT system tracks a moving target with high accuracy. The automatic update of the 4D model is a powerful tool to guarantee the accuracy of tracking without increasing the imaging dose.</p> </sec> </abstract>