Patient specific quality assurance: The final safety net in radiotherapy

Radiotherapy methods have improved with time through technological developments, although with increasing complexity. However, radiotherapy quality can vary significantly across clinics. Quality assurance (QA) systems have developed with treatment methods to maintain and improve safety, accuracy and consistency for routine clinical practice and for clinical trials. Patient-specific quality assurance (PSQA) is an essential component of QA for safe and effective radiotherapy, ensuring that the correct dose is delivered to the correct location for each individual patient. PSQA for external beam MV photon treatment is reviewed, specifically considering dosimetric verification of treatment plan delivery and examining its evolution as modern radiotherapy methods have developed. The principal radiotherapy failure modes are summarized, from a risk-based perspective.Current standard PSQA approaches rely primarily on pretreatment detector-based measurements and have limitations in identifying some failure modes, e.g. ignoring inter- and intra-fraction patient variability, or in handling evolving methods such as online adaptive radiotherapy. Other PSQA approaches and workflows have emerged to address the limitations and challenges, including secondary dose calculations, log file based PSQA, and combining complementary methods. Next-generation PSQA is evolving to improve resource-effectiveness via data-driven and risk-based methodologies. Increasingly, PSQA will combine fast dose recalculation and daily log file/image-based 3D dose reconstruction with online/real-time EPID-based in vivo verification measurements. Respectively, these can enable clinically meaningful structure-based evaluation and continuous treatment monitoring with delivery modification where necessary. Automation and AI-driven analytics will support efficiency and scalability. PSQA must keep on adapting as radiotherapy techniques develop, to continue to ensure their quality and consistency.