An integrated CT-Linac system (Primatom, Siemens, CA), comprising an 82-leaf multi-leaf collimator (MLC) multi-modality linac and spiral CT-on-rails sharing a common treatment couch, was installed at the Northern Centre for Cancer Treatment (NCCT) in 2004. This allows on-treatment verification CT scans to be acquired with the patient in the treatment position.
Installation and commissioning were relatively straightforward, as Primatom is built around familiar established components, however a number of issues were encountered, such as rotational accuracy of the couch, system/laser alignment and collision detection, which required novel approaches. The advantages and disadvantages of using such a system will be discussed.
Primatom has had a positive impact on clinical practice. Pre-existing workflow has been streamlined in a number of areas, allowing a reduction in pre-treatment patient visits and time-saving for various tasks. For example, a 'scan, plan and treat' approach to fast-track palliative treatments has been implemented. Other examples of such improvements will be discussed. Clinical development projects currently ongoing include: accounting for couch attenuation in treatment plans, soft tissue matching, adaptive planning of head and neck patients and online verification of prostate treatments using a dosimetric overlay technique [1].
Staff training and role extension are significant implications of the recent move towards image guided radiotherapy (IGRT) and these pressures are likely to become more widespread as the equipment recommendations of the recent report from the National Radiotherapy Advisory Group (NRAG) [2] are implemented. Rotation of treatment radiographers through NCCT meant a number of key team members required training in on-treatment CT acquisition and the use of virtual simulation software (ProSoma, Medcom, Germany). The resulting group of treatment radiographers have enhanced imaging and anatomical knowledge, beginning a move away from the previously more distinct imaging and treatment roles. It is hoped that this experience will help ease the transition from NCCT to the new Northern Centre for Cancer Care (NCCC) at the Freeman Hospital site later this year.
A second Primatom is currently being commissioned as part of the expanded on-treatment imaging capabilities at NCCC. The new machine will comprise a widebore Siemens Sensation Open CT (up to 82 cm extended field of view) and Siemens Impression IMRT linac with 160 leaf (0.5cm leaf width) MLC.
[1] Smyth G, McCallum HM, Lambert EL and Lawrence GP. A dose distribution overlay technique for image guidance during prostate radiotherapy. British Journal of Radiology, in press.
[2] National Radiotherapy Advisory Group. Radiotherapy: developing a world class service for England. Department of Health, 2007.
Smyth G. CT on a linac: Experience with an integrated linac and CT-on-rails system. Improving Radiotherapy Treatment Accuracy, BIR, London, 23-24th June 2008.
Greg Smyth, NGH Unit, Newcastle upon Tyne. Tel: +44 (0)191-233-6161.
Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK.
Tel: +44 (0)191-233-6161 E-mail: webmaster@rmpd.org.uk Web: http://www.rmpd.org.uk
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