Improved setup and positioning accuracy using a three‐point customized cushion/mask/bite‐block immobilization system for stereotactic reirradiation of head and neck cancer

Abstract

The purpose of this study was to investigate the setup and positioning uncertainty of a custom cushion/mask/bite‐block (CMB) immobilization system and determine PTV margin for image‐guided head and neck stereotactic ablative radiotherapy (HN‐SABR). We analyzed 105 treatment sessions among 21 patients treated with HN‐SABR for recurrent head and neck cancers using a custom CMB immobilization system. Initial patient setup was performed using the ExacTrac infrared (IR) tracking system and initial setup errors were based on comparison of ExacTrac IR tracking system to corrected online ExacTrac X‐rays images registered to treatment plans. Residual setup errors were determined using repeat verification X‐ray. The online ExacTrac corrections were compared to cone‐beam CT (CBCT) before treatment to assess agreement. Intrafractional positioning errors were determined using prebeam X‐rays. The systematic and random errors were analyzed. The initial translational setup errors were −0.8±1.3 mm, −0.8±1.6 mm, and 0.3±1.9 mm in AP, CC, and LR directions, respectively, with a three‐dimensional (3D) vector of 2.7±1.4 mm. The initial rotational errors were up to 2.4° if 6D couch is not available. CBCT agreed with ExacTrac X‐ray images to within 2 mm and 2.5°. The intrafractional uncertainties were 0.1±0.6 mm, 0.1±0.6 mm, and 0.2±0.5 mm in AP, CC, and LR directions, respectively, and 0.0∘±0.5°, 0.0∘±0.6°, and −0.1∘±0.4∘ in yaw, roll, and pitch direction, respectively. The translational vector was 0.9±0.6 mm. The calculated PTV margins normalmPTVfalse(90,95false) were within 1.6 mm when using image guidance for online setup correction. The use of image guidance for online setup correction, in combination with our customized CMB device, highly restricted target motion during treatments and provided robust immobilization to ensure minimum dose of 95% to target volume with 2.0 mm PTV margin for HN‐SABR.PACS number(s): 87.55.ne

Delineation of the primary tumour Clinical Target Volumes (CTV-P) in laryngeal, hypopharyngeal, oropharyngeal and oral cavity squamous cell carcinoma: AIRO, CACA, DAHANCA, EORTC, GEORCC, GORTEC, HKNPCSG, HNCIG, IAG-KHT, LPRHHT, NCIC CTG, NCRI, NRG Oncology, PHNS, SBRT, SOMERA, SRO, SSHNO, TROG consensus guidelines

“…In the future, it is likely that the use of robust planning will directly integrate the organ motion and/or set-up uncertainty in the dose distribution planning [38]. The use of daily imaging may reduce such margin, but a CTV-to-PTV margin below 2 mm is not recommended [39].…”

Clinical outcomes after local field conformal reirradiation of patients with retropharyngeal nodal metastasis

“…[4][5][6] The HN-SBRT treatment was delivered using the Varian TrueBeam STx system (Varian Medical Systems, Palo Alto, CA) with high definition (2.5 mm) leaflets and planned using the 2-3 arc VMAT technique with patients immobilized in a custom biteblock-mask-cushion system with image-guided on-line setup correction, as previously described. [7][8][9] The HN-SBRT was delivered in 5 fractions every other day over 2 weeks.…”

Treatment-Plan Comparison of Three Advanced Radiation Treatment Modalities for Fractionated Stereotactic Radiotherapy to the Head and Neck

“…If we had, the repositioning check tool would have been used before each treatment to correct interfractional setup error. Thus use of our current thermoplastic head and neck immobilization system with LINAC-or IMPT-based FSRS may have involved setup differences [36]. Further comparisons of the two systems are needed with regard to intrafractional translational and rotational restriction of patients, particularly for skull base targets, which are often adjacent to the neuro-optic apparatus.…”