The aim of this work was to evaluate dose response of fluoroscopic EPID for transit dosimetry applications. Properties studied included warm up time, build-up thickness evaluation, dose history, linearity, stability, and short and long-term reproducibility of EPID response, as well as field size dependence.

Pixel value matrices of electronic portal images in DICOM format were analysed in central and 8 off axis points using customised written codes in Matlab. In order to do this, nine 26×26 pixel matrices were selected as regions of interest, the regions represented by these arrays were 1×1 and 0·65×0·65 cm2 at the EPID and isocentre level, respectively.

Necessary warm up time for stable operation of EPID is 30 minutes, and there is no need for extra build-up layer to increase the dose response. Linearity tests indicate charged coupled device camera of EPID saturates at 50 cGy level, and does not have linear relationship with dose. Reproducibility and stability of the measurements were excellent and the detector showed same signal with a maximum deviation of <0·3% both in short and long terms. Results of dosimetric evaluation have shown the TheraView fluoroscopic EPID can be used for transit dosimetry purposes.

It is well established that patients with bone metastases get good pain relief from radiotherapy. The aim of treatment is to achieve maximum pain relief with minimum morbidity. Accuracy and reproducibility of the patient’s position are fundamental to the successful delivery of radiation therapy. It has been recognised for many years, that the accuracy of patient positioning will improve the success of radiation treatment. A previous study carried out in the department showed that the use of only a single tattoo for the set-up of palliative patients resulted in poor accuracy. The aim of this study was to assess if the addition of extra skin marks improved the set-up accuracy of palliative patients being treated for spine and bone metastases. A protocol was implemented detailing the extra skin marks to be used. Daily portal images were acquired and analysed retrospectively using anatomy matching. The results obtained were then compared with those of the previous study. The use of extra skin marks resulted in a total of 45% of images within 5 mm tolerance compared with 36% of images in patients treated with a single centre tattoo. Also, the number of images with deviations greater than 15 mm was reduced by more than 50% with the addition of extra skin marks. This study has shown that extra skin marks do increase the set-up accuracy in palliative patients treated for spine and bone metastases. Therefore, the practice of using extra skin marks has become standard protocol for all palliative patients within the department.

This article reviews portal imaging undertaken for prostate cancer with the intention of developing an imaging protocol for this category of patient. It explores the online and offline approaches of electronic portal imaging, when intervention for field placement errors (FPE) should take place and who actually makes this decision. The choice of reference image is discussed and the questions the use of re-simulation. This paper concludes that it is necessary to image for three fractions in the first week in order to highlight systematic errors, that an electronic portal imager is cost effective in time and money, and that radiographers should review images and make the decisions upon intervention strategies. Images will be reviewed via a quantitative template method rather than via a qualitative “eyeball” method.

There is a large evidence base around prostate cancer. Most of this concentrates on which stages of the disease to treat with which modality. The purpose of this study is to try and determine from the literature an evidence based radiotherapy treatment technique. The evidence is examined on prostate and patient motion, the effect of bladder and rectum filling, patient positioning and error detection with portal imaging. The technique derived is patient supine or prone with empty bladder and bowel. A simple leg immobilisation device is recommended, with set-up to couch height. The required margins are 13.2 mm laterally, 18 mm anterior-posteriorly and 21.3 mm cranio-caudally using a three-dimensional margin recipe. It is shown that an intensive portal imaging routine is required to demonstrate that systematic set-up errors are below 5 mm.

This article reviews the development and potential impact of Digitally Reconstructed Radiographs (DRR's) in the planning and verification of radiotherapy treatments. It explores the requirements for the creation of usable DRR's their integration into current verification methods and it highlights some of the factors that may influence the routine use of DRR's. Continuing developments in radiotherapy techniques demand increasingly accurate verification methods. DRR's provide an efficient and effective representation of planned treatments for comparison with both simulator and portal images, encompassing the digital imaging technology which is the future of radiotherapy treatment verification.