Computer Tomography-Based Target Volume Delineation and Clinical Outcomes of Low-Dose Radiation Therapy for Knee Osteoarthritis

Purpose: Low-dose radiation therapy is a noninvasive and cost-effective treatment modality used to alleviate pain and improve joint function in patients with knee osteoarthritis. However, standardized guidelines for computed tomography (CT)-based target delineation remain limited. This study aims to evaluate the feasibility and safety of low-dose radiation therapy using a CT-based, anatomy-guided clinical target volume that incorporates both bony and soft tissue structures. Methods and Materials: We conducted a retrospective analysis of patients with knee osteoarthritis who received low-dose radiation therapy at our institution. The clinical target volume was delineated on simulation CT to encompass the entire knee joint. Patients received a total dose of 3 Gy, delivered in 6 fractions of 0.5 Gy each on nonconsecutive days. Pain was assessed using a 10-point visual analog scale (VAS) before treatment initiation and upon completion. At a minimum follow-up of 2 months, no acute toxicities of grade ≥2 were observed. In a representative case, CT-based delineation enabled inclusion of suprapatellar recess effusion extending beyond conventional field margins, illustrating the potential for improved anatomical coverage. Conclusions: CT-based, anatomy-guided clinical target volume delineation for low-dose radiation therapy in knee osteoarthritis is feasible and safe, with significant pain reduction observed. This approach provides a reproducible framework that may better reflect patient-specific disease extent compared with conventional field-based techniques. Further prospective studies are warranted to validate its clinical impact.