SGRT impact on 2D transit in-vivo dosimetry for breast cancer patients
Cristina Anson Marcos,
Spain
PD-0806
Abstract
SGRT impact on 2D transit in-vivo dosimetry for breast cancer patients
Authors: Cristina Anson1, Nuria Jornet1, Pedro Gallego1, Jaime Pérez-Alija1, Artur Latorre-Musoll1, Nagore García1, Helena Vivancos1, Marta Barceló1, Agustín Ruiz1, Fátima Leo1, Pablo Carrasco1
1Hospital de la Santa Creu i Sant Pau, Medical Physics, Barcelona, Spain
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Purpose or Objective
Surface-based image guided radiotherapy (SGRT)
allows patient positioning and intrafractional motion monitoring. The aim of
this study is to report the impact of introducing SGRT for breast cancer
patients on the results of 2D transit in-vivo dosimetry (iVD).
Material and Methods
In our centre there are one Clinac and three TrueBeam
units, one of which provided with the optical SGRT system Align-RT (Vision-RT).
The SGRT system is used for patient positioning using the postural video
license, taking special attention to arms position as well as the affected breast.
During the sessions of patients treated on the machine with SGRT capatilibty,
to control intrafraction positioning differences, beam is used with a tolerance
deviation of 5 mm in each radial direction and 3º for the three angular
directions using Align-RT region of interest (breast).
A total of 72 breast cancer patients were enrolled,
50% of them were treated in the unit with SGRT system (W SGRT) and the other
50% in the rest of the units from our centre (WO SGRT). For both groups transit
EPID-based iVD was performed once a week when IGRT orthogonal kV-MV images were
also acquired. EPID images were analysed automaticallly by PerFraction platform
(SunNuclear) using local gamma criteria 5%,7mm, 5%5mm and 3%3mm and 30%
threshold.
Results
A total of
1601 images from 276 fractions were available. Figure 1 shows iVD results for both
groups. In-vivo dosimetry gamma rates were higher
using SGRT for all the three gamma criteria evaluated. The results given by the
percentage of points passing the gamma criteria in quartiles Q1, Q2 (median)
and Q3 are respectively:
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5%,7mm gamma: 95.1%, 97.8%, 99.2% for W SGRT and 93.2%, 97.7%, 98.8% for
WO SGRT
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5%5mm gamma: 93.5%, 96.4% and 98.4% for W SGRT and 88.5%, 95.7%, 97.9%
for WO SGRT.
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3%,3mm gamma: 78.9%, 85.9% and 92.5% for W SGRT and 74.0%, 84.2% and
88.9% for WO SGRT.
Conclusion
Real-time monitoring of patient surface and beam
control during the whole treatment session accounts for higher in-vivo
dosimetry gamma rates obtained using SGRT. This highlights an increase in
treatment accuracy.