Feasibility of patient specific quality assurance for proton therapy based on independent dose calculation and predicted outcomes

Abstract

Patient specific quality assurance (PSQA) is required to verify the treatment delivery and the dose calculation by the treatment planning system (TPS). The objective of this work is to demonstrate the feasibility to substitute resource consuming measurement based PSQA (PSQA M ) by independent dose recalculations (PSQA IDC ), and that PSQA IDC results may be interpreted in a clinically relevant manner using normal tissue complication probability (NTCP) and tumor control probability (TCP) models. Methods and materials: A platform for the automatic execution of the two following PSQA IDC workflows was implemented: (i) using the TPS generated plan and (ii) using treatment delivery log files (log-plan). 30 head and neck cancer (HNC) patients were retrospectively investigated. PSQA M results were compared with those from the two PSQA IDC workflows. TCP/NTCP variations between PSQA IDC and the initial TPS dose distributions were investigated. Additionally, for two example patients that showed low passing PSQA M results, eight error scenarios were simulated and verified via measurements and log-plan based calculations. For all error scenarios DTCP/NTCP values between the nominal and the log-plan dose were assessed. Results: Results of PSQA M and PSQA IDC from both implemented workflows agree within 2.7% in terms of gamma pass ratios. The verification of simulated error scenarios shows comparable trends between PSQA M and PSQA IDC . Based on the 30 investigated HNC patients, PSQA IDC observed dose deviations translate into a minor variation in NTCP values. As expected, TCP is critically related to observed dose deviations. Conclusions: We demonstrated a feasibility to substitute PSQA M with PSQA IDC . In addition, we showed that PSQA IDC results can be interpreted in clinically more relevant manner, for instance using TCP/NTCP.

The GATE-RTion/IDEAL Independent Dose Calculation System for Light Ion Beam Therapy

“…IDC tolerance levels should be related to Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) [37]. A first attempt in this direction was provided in [11], but with another initial purpose in the framework of Model-Based approaches, to confirm the decision-making process for patient selection, when NTCP models are used as a basis. If NTCP models are not available (or not calibrated for the clinics), the review of DVHs and clinical goals is actually a practical alternative to evaluate IDC-based PSQA outcome in a more clinically relevant manner.…”

“…the recomputation of a plan exported by the TPS using an IDC system, only allows to check TPS dose computation errors, but cannot detect beam delivery failures or data transfer corruption. For this reason, several groups have worked on the combination of IDC systems with machine steering files and/or treatment log-files [7][8][9][10][11]. With respect to LIBT, for ions heavier than protons, much less literature is available.…”

Executive Summary of Clinical and Technical Guidelines for Esophageal Cancer Proton Beam Therapy From the Particle Therapy Co-Operative Group Thoracic and Gastrointestinal Subcommittees

“…Efforts such as those described by Meijers et al. basing patient specific quality assurance on independent dose calculation and predicted outcomes should find broader application in the future ( 61 ).…”

A critical review of the practices of proton daily quality assurance programs

“…Although comprehensive QA guidelines for radiotherapy should also include patient-specific QA (PSQA), TG-224 focuses on periodic machine QA exclusively. However, there are many publications that describe PSQA in PT for the interested reader (61)(62)(63). TG-224 identifies the proton beam parameters that are typically checked and contains 4 tables listing the recommended QA procedures for daily, weekly, monthly, and annual QA.…”