Radiotherapy Equipment in the Department
The Radiotherapy Department has five linear accelerators (Linacs), one treatment simulator, a CT Scanner, a treatment planning system (Eclipse) and virtual simulator (AdvantageSim) for external beam therapy. There is a Varisource high dose rate afterloading machine for brachytherapy and a newly commissioned Xstrahl unit for superficial treatments.
All new equipment purchased, including treatment units and computer systems is tested and commissioned by Radiotherapy Physics staff, prior to its use on patients. Due to the potentially dangerous nature of the radiation used, this commissioning process must be steady and methodical. Routine work in other areas must be continued during commissioning and the additional work required is sometimes undertaken outside normal working hours.
Clinical Scientists are responsible for measuring all the data required at commissioning. This is usually carried out in a large water tank and involves measuring the performance of the machine in all possible modes of use. This data has to be processed and checked before being transferred to the treatment planning computer for use in patient dose calculations for treatment planning. The Clinical Scientists are responsible for the accuracy and applicability of all data used in the Radiotherapy Department.
Specialist Techniques in the Department
In early 2005 the Department started an IMRT (Intensity Modulated radiotherapy) program and this is now routine treatment for those patients who require it. The department uses a dynamic sliding window technique where the blades of the multileaf collimator move whilst the radiation beam is being delivered in order to vary or modulate the radiation across the tumour volume and thus more accurately shape the radiation dose around the tumour. The department was the first in the UK and only the second in the world to commission portal dosimetry as the technique for individual patient quality assurance of IMRT treatments.
RapidArc is a specialist treatment where an IMRT like plan is delivered while the linear accelerator gantry rotates. The treatments are much faster than routine IMRT and can allow more conformal dose distributions than routine IMRT for various treatment sites. RapidArc has been commissioned by Radiotherapy Physics and prostate and lung SABR patients are being treated. RapidArc for lung SABR allows a large dose of radiation to be delivered to a small area while sparing the surrounding tissue and sensitive organs.