The Radiotherapy Physics Section of the Medical Physics Department provides a range of clinical scientific and technical services, equipment commissioning, development, research, radiation protection and Medical Physics Expert advice, associated with the therapeutic use of ionizing radiation, in close collaboration with the Portsmouth Oncology Centre.
The department’s routine work is primarily divided into three areas:
Non-routine work includes:
The Radiotherapy Physics Section is accredited by BSi to the ISO9001 quality standard, and provides training of Medical Technical Officers and Clinical Scientists (IPEM part 1 and 2 training scheme).
Head of Radiotherapy Physics: Dr Tony Palmer PhD BSc MSc FIPEM CSci
Contact: Medical Physics Dept secretary 02392 286000 ext. 3706
Graphical Representation of treatment with Electrons
The accurate delivery of the correct radiation dose is of vital importance in radiotherapy; too small a dose and cancerous cells may survive, too large and healthy organs may be damaged. One is not able to buy a meter “off the shelf” for radiotherapy, instead dosimeters must be accurately calibrated in-house in each treatment beam in use, in collaboration with the National Physical Laboratory. Radiotherapy equipment is highly complex and a comprehensive schedule of quality control and dosimetry checks is undertaken to ensure high quality treatment is delivered.
“Quality control” protocols for radiotherapy equipment are part of the quality assurance program. The term ‘quality control’ is defined as a regulatory process through which the actual performance of equipment is measured and compared with existing standards or reference values, together with the actions necessary to be taken in order to keep or regain conformity with these standards. The question of what constitutes acceptable quality may be guided by national or international standards, or may be left to the professional judgment of the senior physics staff involved.
Using the most modern 3D computer systems we provide clinical radiotherapy treatment planning that is individually optimized for each patient, in order to deliver radiation only where it is required. Independent verification software and calculation checks prior to treatment, and electronic imaging and dosimetry during treatment ensure a high quality of treatment delivery. Treatment planning for external beam radiotherapy using photons and electrons, and brachytherapy using sealed radioactive material such as I125 seeds for prostate implantation is undertaken. The service also manufacturers patient-specific devices including radiation beam shaping and immobilization equipment.
Treatment planning is the process whereby the prescription of the clinician becomes a set of treatment instructions together with the distribution of dose in the patient. For external beam therapy, the target volume is specified by the clinician on films, CT scans or the patient’s contour. The planning technician or clinical scientist determines the optimum treatment configuration to irradiate the target volume to the specified dose within any constraints specified by the clinician. This might include avoiding some parts of the body, or minimising the dose to certain organs. The resulting dose distribution is produced, and an unambiguous set of treatment instructions is prepared for the radiographers.