Onboard cone‐beam CT‐based replan evaluation for head and neck proton therapy

Abstract

Quality assurance computed tomography (QACT) is the current clinical practice in proton therapy to evaluate the needs for replan. QACT could falsely indicate replan because of setup issues that would be solved on the treatment machine. Deforming the treatment planning CT (TPCT) to the pretreatment CBCT may eliminate this issue. We investigated the performance of replan evaluation based on deformed TPCT (TPCTdir) for proton head and neck (H&N) therapy. Methods and materials: Twenty-eight H&N datasets along with pretreatment CBCT and QACT were used to validate the method. The changes in body volume were analyzed between the no-replan and replan groups. The dose on the TPCTdir, the deformed QACT (QACTdir), and the QACT were calculated by applying the clinical plans to these image sets. Dosimetric parameters' changes, including ΔD95, ΔDmean, and ΔD1 for the clinical target volumes (CTVs) were calculated. Receiver operating characteristic curves for replan evaluation based on ΔD95 on QACT and TPCTdir were calculated, using ΔD95 on QACTdir as the reference. A threshold for replan based on ΔD95 on TPCTdir is proposed. The specificities for the proposed method were calculated. Results: The changes in the body contour were 95.8 ± 83.8 cc versus 305.0 ± 235.0 cc (p < 0.01) for the no-replan and replan groups, respectively. The ΔD95, ΔDmean, and ΔD1 are all comparable for all the evaluations. The differences between TPCTdir and QACTdir evaluations were 0.30% ± 0.86%, 0.00 ± 0.22 Gy, and −0.17 ± 0.61 Gy for CTV ΔD95, ΔDmean, and ΔD1, respectively. The corresponding differences between the QACT and QACTdir were 0.12% ± 1.1%, 0.02 ± 0.32 Gy, and −0.01 ± 0.71 Gy. CTV ΔD95 > 2.6% in TPCTdir was chosen as the threshold to trigger QACT/replan. The corresponding specificity was 94% and 98% for the clinical practice and the proposed method, respectively. Conclusions:The replan evaluation based on TPCTdir provides better specificity than that based on the QACT.

An optimized framework for cone‐beam computed tomography‐based online evaluation for proton therapy

“…In most cases, the anatomy depicted in these images closely resembles that of the pretreatment CBCT images. However, inherent setup uncertainties during the QACT scan can introduce some mismatches between the QACT and CBCT images 14 . To mitigate this, deformable registration (DIR) is employed to align the QACT with the CBCT, resulting in the creation of the deformed QACT (dQACT).…”

“…The reference images were acquired from the same‐day QACT scans. Then, QACT images were deformed to cCBCT to obtain deformed QACT (dQACT) 14 using the built‐in function of RayStation. We compared the dose distributions obtained by Monte Carlo calculation using dQACT and sCT images, cCBCT and vCT.…”

“…However, inherent setup uncertainties during the QACT scan can introduce some mismatches between the QACT and CBCT images. 14 To mitigate this, deformable registration (DIR) is employed to align the QACT with the CBCT, resulting in the creation of the deformed QACT (dQACT). Previous literature has demonstrated that DIR offers the best possible means to minimize mismatches between the QACT and CBCT.…”

Dosimetric impact of adaptive proton therapy in head and neck cancer – A review

“…Consequently, not all HNC patients require APT during IMPT and the dosimetric benefits found in this review may overestimate the general benefit of APT. While Deiter et al [25] found that 63 % of the HNC patients needed IMPT replanning, Stanforth et al [30] found that approximately 30 % of their HNC cohort were replanned during IMPT. In accordance with this review, they found that in most cases one plan adaptation was sufficient to restore target coverage, and in some cases two plan adaptations were necessary.…”

Deep learning-based Fast Volumetric Image Generation for Image-guided Proton FLASH Radiotherapy

“…In contrast, the current proton on-board CBCT 35 requires approximately 35 and 60 seconds for full-fan and half-fan scans. InverseNet3D is currently implemented in the framework.…”