What do we do?
The majority of radiotherapy treatments involve the use of x-rays or electrons (small charged particles). Sophisticated equipment is used to produce these radiation beams and the range of treatment units at the Norfolk and Norwich University Hospital includes several low and high energy ‘linear accelerators’. All Radiotherapy equipment is maintained by qualified electronics and mechanical engineers. This maintenance process is more than simply electronic repair. Each treatment unit is designed to include complex control mechanisms to assure the user of the quality and quantity of radiation emitted. A regular series of tests and measurements is carried out on all equipment, careful records are maintained and the performance of each treatment unit is confirmed prior to its use.
Maintaining equipment of such complexity is again a multi-disciplinary task. It is essential that the users of each unit, the therapy radiographers, feed back any problems with machine performance so that immediate evaluation work can be carried out. Engineering staff then work in close collaboration with Clinical Scientists to ensure that all radiation parameters are correctly set before the machine is used to treat patients.
Each patient receiving radiotherapy treatments is given independent consideration by a Radiation Oncologist and a radiation treatment strategy is determined that will maximise the radiation dose to the target volume and minimise the radiation damage to surrounding body tissues. In many cases, complex computer programmes are used to predict radiation dose patterns that would result from the various treatment options. Dosimetrists are therapy radiographers who have received extensive, specialist training in the use of such computer programmes. It is essential that as the various options are explored, the physical principles underlying the radiation dose calculations are fully understood. It is also essential that patient comfort and the practicalities of treatment set-up are given thorough consideration.
Dosimetrists are supported by Radiotherapy Physics staff, high-lighting the multi-disciplinary nature of the work. Trained Radiation Physicists (Clinical Scientists) are available to assist with scientific and advanced computing issues. Dosimetrists also work very closely with Mould Room staff (see below) to ensure that patients, where necessary, can be immobilized comfortably in the required treatment position.
Close links between computer planning and simulator planning in the Radiotherapy Department are essential and the Dosimetrists work in both of these areas. They also attend the treatment units, where necessary, to help to ensure consistency between the planning and treatment stages. Although the Dosimetrists are strictly part of the Radiotherapy Department, the work they do remains an integral part of Radiotherapy Physics. They therefore provide a vital link between the two departments.
The majority of Radiotherapy treatments require high doses of ionising radiation to be administered to the patient. With such high doses, the margin between successful clinical outcome and tissue damage can be small. It is therefore essential that when a radiation dose is prescribed by a Radiation Oncologist, the precise required dose is delivered to the patient. One of the key roles of the Clinical Scientists working in Radiotherapy Physics is to accurately calibrate the radiotherapy treatment machines. Therapy Radiographers, operating the treatment equipment, must have confidence that correct machine settings result in the correct radiation dose.
Radiation dosimetry is a complex field requiring an in-depth knowledge of the interaction characteristics of ionising radiation. Many theoretical concepts and individually measured factors are incorporated into the final dose settings on each treatment machine.
The Radiotherapy Physics Department has participated fully in national audit programmes, designed to confirm the accuracy of dosimetry work. Audit is seen as an invaluable tool in the assurance of quality.
Our department uses diode detectors for in-vivo dosimetry to confirm the correct dose is delivered to every external beam photon radiotherapy patient, this includes IMRT and RapidArc patients. Our department is currently commissioning transit dosimetry which uses the EPID on-board imager to measure dose from treatment beam after it has travelled through the patient.
Brachytherapy is the use of small radioactive sources implanted directly into or close to a tumour to cause maximum effect and minimal damage to healthy tissues around the tumour. At NNUH this type of treatment is carried out using a high dose-rate afterloading machine which contains a source of radioactive iridium which is approx 5mm long and 0.5mm in diameter. Applicators are first inserted into the patient and then connected to the afterloader so that the iridium source can travel into the applicator under computer control, and step through pre-programmed dwell positions to build up the radiation dose required. Clinical Scientists are responsible for calibrating and programming the source to ensure that the correct dose is delivered in the correct place.
The department introduced CT based planning in 2008 and MRI based planning with Ring applicator in 2010 for patients undergoing high dose rate brachytherapy for cancer of the cervix. In 2012 the brachytherapy service has moved to a paperless system and interstitial needles have been commissioned for use with the Ring applicators to treat cervical cancer with parametrial spread.
Despite their therapeutic value, the potential hazards of dealing with ionizing radiations should never be underestimated. A key role of the Radiotherapy Physics Department is to provide advice to staff and patients about the risks and safe use of ionizing radiations. Instructions and procedures are prepared to be fully compatible with national and international guidelines. New radiation areas within the hospital, such as treatment rooms and radionuclide storage facilities must be carefully planned and regularly monitored. Careful control is kept of all radioactive materials kept on hospital premises.
All Radiotherapy Physics staff are trained in radiation protection issues, Clinical Scientists are trained to post-graduate level in radiation physics.
Radiotherapy Physics Projects
Radiotherapy is a rapidly developing field and a key role of all Radiotherapy Physics staff, Clinical Scientists in particular, is to keep up to date with recent changes in technology and scientific practice and to assist with local implementation of change.
Recently completed development projects include:
- Transit EPID Dosimetry (TED)
- Commissioning of Superficial unit
- SmartAdapt (deformable registration) commissioning for prostate re-plan assessment
Current development projects include:
- Evidence Based Patient QA
- Upgrade of our Radiotherapy Management and Treatment planning system to Aria 13.7
- Refurbishment of HDR Brachytherapy suite to allow development of HDR Prostate treatments
- RapidArc for other body sites apart from prostate/pelvis and lung SABR
- Deep Inspiration Breath hold (DIBH) techniques for breast treatment
In order to minimise the potential harmful effects of radiation treatments, great care is taken to minimise the size of the radiation beams used and geometric accuracy is therefore paramount. Many patients will require high precision immobilization casts (treatment shells) to reduce movement during treatments. In addition, Radiation Oncologists may require certain body tissues to be individually shielded. Manufacture of these immobilization and shielding devices is the responsibility of the Radiotherapy Physics Mould Room Technicians. These staff are fully trained in mechanical engineering principles but their work with patients necessitates additional skills in patient care. Mould Room staff work closely with the Dosimetrists and the Radiographers working on the treatment units to ensure that the required patient position is achieved.
In addition to manufacturing tasks, Mould Room staff have the general responsibility for geometric accuracy on the treatment units and treatment simulators. This involves careful set up and quality assurance of the lasers used as a guide to patient alignment and the light field used to identify the expected orientation of the radiation beams.
The Radiotherapy department contains a large amount of highly complex equipment. Many of these require constant monitoring and preventative maintenance. Our Electronic Engineers are highly trained in keeping equipment at the peak of performance for the purpose of safety and efficiency. Should a piece of equipment fail, it is imperative that it is working again as soon as possible in order to reduce delays to patients. Our Engineers work closely with the other staff in Radiotherapy Physics and Radiotherapy as well as with external manufacturers.
As IT infrastucture has grown increasingly complex over the last few years the Department now employs its own IT support engineer. A member of the Trust IT team, Paul is embedded within the Radiotherapy Physics team providing on the spot IT fault finding and trouble shooting to ensure patient treatment is maintained at all times even in the event of a Trust network failure.