A feasibility and pilot study of the clinical efficacy of a custom designed handgrip device to improve patient immobilisation for the external beam radiotherapy of oesophageal cancers

Abstract

The primary aim of radiotherapy is to eradicate tumour cells within the clinical target volume (CTV), at the same time while sparing surrounding organs at risk (OAR) which is often accomplished by conforming to the treatment fields, i.e. target volume and by using appropriate margins for accounting the treatment uncertainties. Furthermore, for accurate radiation dose delivery, perfect immobilisation is required to keep the patient within the same position at each treatment fraction. There has always been a need for perfect immobilisation which should provide minimal patient movement, patient comfort, reproducible patient positioning during radiotherapy and be less expensive. The main objective of the present study was to design, fabricate and evaluate a handgrip board immobilisation device for the thorax region to boost the efficiency of the external beam radiotherapy in oesophageal cancer patients and evaluate the set-up error. Our indigenously fabricated handgrip baseboard device is made of poly-methyl methacrylate (PMMA), which consists of the main baseboard with an adjustable central T-bar and separate right and left single hand poles. In the present study, fifteen patients with oesophageal tumours were included. Patients were positioned using the indigenously fabricated handgrip immobilisation device; portal images were performed prior to the treatment and matched with the digitally reconstructed radiographs (DRR). The population systematic (Σ) and random (σ) patient set-up errors were calculated along the direc­tions of Anterior-Posterior (AP), Medial-Lateral (ML) and Superior-Inferior (SI). The values for the planning target volume (PTV) margins were calculated using ICRU 62, Van Herk’s and Stroom’s formulae. The population systematic (Σ) errors of AP, ML and SI were 0.12, 0.20 and 0.20 cm, respectively while the population random (σ) errors of AP, ML, SI were 0.17, 0.31 and 0.17 cm, respectively. The PTV margins were calculated according to ICRU 62, Van Herk’s, and Stroom’s and it was observed in the range of 0.2–0.7 cm in the three acquisition directions. The use of a handgrip immobilisation device allowed for relatively small set-up errors and ensured the patient’s comfort. Also, the technique showed satisfactory accuracy and reproducibility.