The OBI is a digital imaging device mounted on the treatment machine via robotically controlled arms that operate along three axes of motion. No other imaging device for radiotherapy has this range of motion. This allows the imager to be positioned optimally for the best possible view of the tumour and surrounding anatomy. The device produces high-resolution images of the tumour, and it can track tumour motion to provide doctors with a clear indication of exactly how a tumour will move during treatment due to normal breathing and other physiological processes.

Prior to the advent of IGRT and tools like the OBI and RPM gating, radiation oncologists had to contend with variations in patient positioning and with respiratory motion by treating a larger margin of healthy tissue around the tumour. IGRT is expected to enable doctors to minimise the volume of healthy tissue exposed to the treatment beam.

As well as these key IGRT solutions, the clinic’s radio-oncology department also implemented an entirely paperless and filmless working environment, utilising a dedicated radio-oncology management system, offering verification and recording as well as image management functionality. It incorporates an additional electronic patient chart that is totally customisable and allows a seamless data transfer, and is linked to all the hospital and institute systems. As a result, all patient data including images can be retrieved at every workstation.

Aarau has treated about 300 patients to date using the OBI, primarily for breast and prostate cancer, in the thorax region used in conjunction with gating. Indeed, Aarau is the only clinic doing gating in Switzerland. It is treating breasts (left and right side), and is also treating every lung cancer with gating and using the fluoroscopic pre-treatment setup verification on the OBI. For the very first time, this modality enables the physician to look into the patient and to analyse the target volume movement prior to treatment. The assumptions based on the 4- D-CT scan information can therefore be verified in realtime with regard to possible changes in breathing pattern, i.e. due to treatment-induced tumour regression.

At present, 45 patients are being treated per day, 15 of them with gating. Cone beam CT (CBCT) has been used for about 50 patients who have undergone a CBCT scan but at the moment more experience with the image quality is needed, with exploration of the possibilities of what it is capable of before it is incorporated into routine clinical use. Initial problems with its stability have been solved and it has already been used for treatment planning. Comparisons have been conducted between diagnostic CT scans and CBCT scans to the same patient and the relative dose distribution is approximately the same.

The fluoroscopic mode offers the first chance to really look into the patient and analyse whether the movement of the target for the gating threshold is really correct. It allows for decreasing the margin, which obviously benefits patients, and it reduces side effects. Every breast is being treated with a form of IMRT called e-compensation, which has enabled a reduction of the dose maximum from 125% to just 105%; using this, the skin reactions are dramatically decreased and the side effects are much better, bringing down the dose to the heart to zero in some cases. By using these imaging and treatment techniques, the patients’ experience is far better.