This study examined the variation of dose-volume histogram (DVH) data sourced from multiple radiotherapy treatment planning systems (TPSs). Treatment plan exports were obtained from 33 Australian and New Zealand centres during a dosimetry study. Plan information, including DVH data, was exported from the TPS at each centre and reviewed in a digital review system (SWAN). The review system was then used to produce an independent calculation of DVH information for each delineated structure. The relationships between DVHs extracted from each TPS and independently calculated were examined, particularly in terms of the influence of CT scan slice and pixel widths, the resolution of dose calculation grids and the TPS manufacturer. Calculation of total volume and DVH data was consistent between SWAN and each TPS, with the small discrepancies found tending to increase with decreasing structure size. This was significantly influenced by the TPS model used to derive the data. For target structures covered with relatively uniform dose distributions, there was a significant difference between the minimum dose in each TPS-exported DVH and that calculated independently.

Immobilization casts are used to reduce patient movement during the radiotherapy of head and neck and brain malignancies. Polyethylene-based casts are produced by first taking a Plaster of Paris 'negative' impression of the patient. A 'positive' mould is then made, which is used to vacuum form an immobilization cast. Taking the 'negative' cast can be messy, stressful for patients and labour intensive. Recently, lightweight hand-held laser surface scanners have become available. These allow an accurate 3-D representation of objects to be generated non-invasively. This technology has now been applied to the production of casts for radiotherapy. Each patient's face and head is digitized using the Polhemus FastSCAN (Polhemus, Colchester, VT, USA) scanner. The electronic data are transferred to a computer numerical controlled mill, where a positive impression is machined. The feasibility of the process was examined, the labour required and radiation therapists' satisfaction with aspects of the produced masks assessed. The scanner-based method of mask production was found to be simple, accurate and non-invasive. There was a reduction in radiation therapist labour required. Masks produced with the scanner-based method were reported to result in improved mask fitting, daily reproducibility, patient immobilization and patient comfort.

Accurate and reproducible patient positioning is fundamental to the success of fractionated radiotherapy. Poor patient positioning could result in geographic misses. We have recently reported on an improved method of customized face mask production using laser surface scanning. In this report, we sought to identify and develop a method to routinely make customized neck supports for patients prescribed radiotherapy to the brain or head and neck regions. We identified a potentially suitable product--sealed packs containing two liquids that produce expanding polyurethane foam when mixed--and developed a method for their use. The neck supports are inexpensive and simple to produce (taking less than 5 min of radiation therapist labour). We assessed the customized neck supports in several ways. The effect on setup accuracy was assessed by comparing two consecutive cohorts of patients. Statistically significant differences favouring the customized neck supports included a reduced total displacement error (mean 3.4 vs. 2.1 mm) and a reduced left-right setup error (mean 1.8 vs. 1.1 mm). This is consistent with the greater support provided by the customized neck supports. This method could easily be undertaken by other departments.