Author: Sven Ferguson, S. Murty Goddu, Ana Heermann, Taeho Kim, Nels C. Knutson, Hugh HC Lee, Shanti Marasini, Timothy Mitchell, Seungjong Oh, Kevin Renick 👨🔬
Affiliation: Washington University in St. Louis School of Medicine, Washington University School of Medicine in St. Louis, Department of Radiation Oncology, Washington University School of Medicine in St. Louis 🌍
Purpose: In the Gamma Knife stereotactic radiosurgery (GK-SRS), the delineation of organs-at-risks (OARs) was not fully automated. Due to the cumbersome nature of manual OAR contouring, dose evaluation to OARs is often visually estimated without contours. This can increase the risk of accidentally delivering an overdose to OARs, harming patients. Seamless OAR auto-contouring (AC) can improve patient safety and workflow in GK-SRS by leveraging artificial intelligence to generate OARs during the MRI transfer from the scanner to the GK planning system. To assess the benefits of the AC, we retrospectively analyzed planning data along with dosimetric parameters of AC OAR contours.
Methods: In the study, we performed AC on T1-weighted MR images of 520 patients (420 brain metastases, 59 meningioma, and 41 acoustic neuroma cases) under IRB approval. The process generated eight brain OARs (optic chiasm, optic nerves, hippocampi, hypothalamus, pituitary, and brainstem). Dose constraints were evaluated based on AAPM TG-101.
Results: 1) The success rates of AC for the optic chiasm, left optic nerve, right optic nerve, and brainstem were 96.9%, 95.7%, 96.3%, and 96.9%, respectively. The assessment could not be conducted in some cases due to the insufficient quality of the contours or failure of contour generation, indicating a limitation of the applied AC. 2) No instances of dose constraint violations were reported on the optic pathways. 3) In contrast, from the GK-SRS delivered plans, we identified 35 violations out of 504 cases for the brainstem D0.5cc constraint (>10Gy), and 47 cases exceeded the D0.035cc constraint (>15Gy). In all brainstem violation cases, we confirmed the AC-generated brainstem contours overlapped with the clinical target contours.
Conclusion: The seamless AC workflow enhanced patient safety by reducing the risk of overlooking critical structures during treatment planning. It is essential to verify the quality of the generated contours for accurate dosimetric evaluation.