A hybrid quality assurance framework for total marrow and lymphoid irradiation: Integrating independent 3D dose...

To evaluate a comprehensive quality assurance (QA) strategy for total marrow and lymphoid irradiation (TMLI) integrating independent 3D dose calculation (Plan QA) with measurement-based verification. This retrospective study analyzed 40 TMLI plans designed on helical tomotherapy. The hybrid framework employed Plan QA for independent whole-body 3D dose verification and a 2D ionization chamber array for local thoracoabdominal verification. Gamma analysis was performed under multiple criteria. Relationships between verification passing rates and plan complexity parameters were investigated using logistic regression and receiver operating characteristic (ROC) curves to identify independent risk factors and predictive thresholds. Plan QA demonstrated excellent dosimetric agreement with the treatment planning system, with no significant difference in mean target doses. ROC analysis identified the 2 mm/1% gamma criterion as the optimal metric for Plan QA to screen high-risk plans, establishing an action threshold of 92.0%. For measurement verification, outcomes were significantly influenced by multileaf collimator (MLC) motion parameters. The percentage of leaves reaching maximum open time (%Max LOT) and mean leaf open time (Mean LOT) were identified as independent risk factors for delivery failure. Predictive safety thresholds were established: %Max LOT less than 12.70% and Mean LOT less than 225.1 ms. This study validates a hybrid QA paradigm for TMLI. Plan QA ensures whole-body calculation accuracy and risk screening, while measurement monitors delivery precision. By establishing actionable MLC parameter thresholds, this system supports a transition from detection-based to predictive risk management in complex radiotherapy.