A Feasibility Study for in vivo Dosimetry Procedure in Routine Clinical Practice

Maria D. Falco, Stefano Giancaterino, Andrea De Nicola, Nico Adorante, Ramon Gimenez De Lorenzo, Monica Di Tommaso, Annamaria Vinciguerra, Marianna Trignani, Francesca Perrotti, Albina Allajbej, Andrea Fidanzio, Francesca Greco, Mattia Grusio, Domenico Genovesi, Angelo Piermattei

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Purpose: The aim of the in vivo dosimetry, during the fractionated radiation therapy, is the verification of the correct dose delivery to patient. Nowadays, in vivo dosimetry procedures for photon beams are based on the use of the electronic portal imaging device and dedicated software to elaborate electronic portal imaging device images. Methods: In total, 8474 in vivo dosimetry tests were carried out for 386 patients treated with 3-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and volumetric modulated arc therapy techniques, using the SOFTDISO. SOFTDISO is a dedicated software that uses electronic portal imaging device images in order to (1) calculate the R index, that is, the ratio between daily reconstructed dose and the planned one at isocenter and (2) perform a gamma-like analysis between the signals, S, of a reference electronic portal imaging device image and that obtained in a daily fraction. It supplies 2 indexes, the percentage gamma% of points with gamma < 1 and the mean gamma value, gamma(mean). In gamma-like analysis, the pass criteria for the signals agreement Delta S% and distance to agreement Delta d have been selected based on the clinical experience and technology used. The adopted tolerance levels for the 3 indexes were fixed in 0.95 <= R <= 1.05, gamma% >= 90%, and gamma(mean) <= 0.5. Results: The results of R ratio, gamma-like, and a visual inspection of these data reported on a monitor screen permitted to individuate 2 classes of errors (1) class 1 that included errors due to inadequate standard quality controls and (2) class 2, due to patient morphological changes. Depending on the technique and anatomical site, a maximum of 18% of tests had at least 1 index out of tolerance; once removed the causes of class-1 errors, almost all patients (except patients with 4 lung and 2 breast cancer treated with 3-dimensional conformal radiotherapy) presented mean indexes values (<(R)over bar>, (gamma) over bar%, and (gamma) over bar (mean)) within tolerance at the end of treatment course. Class-2 errors were found in some patients. Conclusions: The in vivo dosimetry procedure with SOFTDISO resulted easily implementable, able to individuate errors with a limited workload.
Original languageEnglish
Pages (from-to)NIL_1-NIL_8
JournalTECHNOLOGY IN CANCER RESEARCH &amp; TREATMENT
Volume17
DOIs
Publication statusPublished - 2018

Keywords

  • 3-DCRT
  • EPID imaging
  • IMRT
  • VMAT
  • gamma-like analysis
  • in vivo dosimetry

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