EPID-based in-vivo dosimetry using Dosimetry Check™: overview and clinical experience in a five year study including breast, lung, prostate and head and neck cancer patients

William H. Nailon*, Daniel Welsh, Kim McDonald, Donna Burns, Julie Forsyth, Gillian Cooke, Francisco Cutanda, Linda J. Carruthers, Duncan B. McLaren, Josep Puxeu Vaqué, Terence Kehoe, Sankar Andiappa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Background: Independent verification of the dose delivered by complex radiotherapy can be performed by electronic portal imaging device (EPID) dosimetry. This paper presents five-year EPID in vivo dosimetry (IVD) data obtained using the Dosimetry Check (DC) software on a large cohort including breast, lung, prostate, and head and neck (H&N) cancer patients. Material and Methods: The difference between in vivo dose measurements obtained by DC and point doses calculated by the Eclipse treatment planning system was obtained on 3795 radiotherapy patients treated with volumetric modulated arc therapy (VMAT) (n=842) and three-dimensional conformal radiotherapy (3DCRT) (n=2953) at 6, 10 and 15MV. In cases where the dose difference exceeded ±10% further inspection and additional phantom measurements were performed. Results: The mean and standard deviation (μ±σ) of the percentage difference in dose obtained by DC and calculated by Eclipse in VMAT was: 0.19±3.89% in brain, 1.54±4.87% in H&N and 1.23±4.61% in prostate cancer. In 3DCRT this was 1.79±3.51% in brain, -2.95±5.67% in breast, -1.43±4.38% in bladder, 1.66±4.77% in H&N, 2.60±5.35% in lung and -3.62±4.00% in prostate cancer. A total of 153 plans exceeded the ±10% alert criteria, which included: 88 breast plans accounting for 7.9% of all breast treatments; 28 H&N plans accounting for 4.4% of all H&N treatments; and 12 prostate plans accounting for 3.5% of all prostate treatments. All deviations were found to be as a result of patient-related anatomical deviations and not from procedural errors. Conclusions: This preliminary data show that EPID-based IVD with DC may not only be useful in detecting errors but has the potential to be used to establish site-specific dose action levels. The approach is straightforward and has been implemented as a radiographer-led service with no disruption to the patient and no impact on treatment time.
Original languageEnglish
Pages (from-to)6-16
Number of pages11
JournalJournal of Applied Clinical Medical Physics
Volume20
Issue number1
Early online date7 Dec 2018
DOIs
Publication statusPublished - 15 Jan 2019

Keywords / Materials (for Non-textual outputs)

  • dose verification
  • EPID dosimetry
  • in vivo dosimetry
  • transit dosimetry

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