Vault Retrofit and Re-Engineering for Varian Truebeam V3 In a Bunker Originally Designed for Clinac Dhx
Abstract
Purpose
To retrofit a 2009-era Clinac DHX bunker at Square Cancer Centre, Dhaka, for Varian TrueBeam V3 (10 MV-FFF) without structural demolition, enabling SRS/SBRT capabilities while establishing a replicable model for similar upgrades.
Methods
Following treatment cessation (November 9, 2024), Varian teams and contractors dismantled the Clinac DHX under RSO supervision. Infrastructure upgrades included: 20mm borated polyethylene (BP) door replacement, 30mm BP scatter wall addition, electrical/mechanical systems, 100kVA UPS, and isolated grounding. Original concrete walls remained intact. TrueBeam V3 commissioning followed IAEA TRS-398 protocols, measuring TPR20,10 and PDD10 for 6MV, 6MV-FFF, 10MV, and 10MV-FFF beams with kQ, kTP, kpol, and ks corrections. Radiation surveys verified regulatory compliance (Winston-Lutz, Picket-Fence, IMRT/VMAT tests; gamma indices >95% at 3%/3mm). SSDL validated beam calibration; BAEC audited and licensed the facility. Commissioning and documentation required 4 weeks; staff received 4-day on-site training.
Results
Successful retrofit achieved without concrete demolition. At 1000 Gy/week (10 MV FFF), door measurements showed: neutron dose 0.38 µSv/h, photon dose 3.91 µSv/h, and electron dose 2.95 Bq/cm²—all <5% of NSRC-1997/IAEA limits. All beam energies met clinical specifications with proper quality metrics.
Conclusion
Strategic BP shielding enables cost-effective Clinac DHX-to-TrueBeam V3 retrofit, expanding global access to precision radiotherapy. This approach provides resource-limited centers a viable pathway to modernize infrastructure while maintaining regulatory compliance and treatment continuity.