Medical Physics Department

The accurate delivery of the correct radiation dose is vitally important in radiotherapy; too small a dose and cancerous cells may survive, too large and healthy organs may be damaged. 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. 

Treatment planning is where 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.  

Using 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 high quality treatment.  

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. 

The imaging equipment supported includes CT scanners, angiography X-ray systems, mammography units plus digital radiography and dental X-ray equipment. Services provided include commissioning and radiation safety testing, support to clinical users for optimization, pre-purchase advice for new imaging equipment, patient dosimetry audit and dose calculation.  We are also experts for radiation risk assessments, the planning of new radiation facilities, personnel dosimetry, radiation emergency planning, critical examinations and regulatory compliance audit for radiation services. Teaching and training on radiation protection and safety is also provided. 

We undertake performance testing of UV treatment systems and provide advice on safety and staff protection. For laser systems used for medical purposes, we can advise on the suitability of new facilities and support the development of safety procedures and documentation as well as provide training.  

The team provides numerous services related to MRI including:  

• MR Quality control - Quarterly tests are performed the MRI scanners to ensure the quality of the imaging systems is within tolerances suggested by acceptance, manufacturer and MHRA reports.  

• Environmental and site safety - Annual safety audit and monthly checks are performed to ensure safety and environmental conditions comply with the MHRA guidelines.  

The team works alongside clinical colleagues to support the introduction of new techniques or deliver quality improvements. Areas of interest within the group include CT imaging for radiology and radiotherapy, paediatric radiography, advanced MR quality control techniques, improvement of MR sequences in the presence of complex clinical conditions, MR patient safety for non-classified implants . Work is often presented at national conferences or published in scientific journals.  

We provide accredited professional training for clinical scientists and technologists in diagnostic radiology and radiation protection.

Glomerular Filtration Rate (GFR) - This test is designed to measure the Glomerular Filtration Rate (GFR) which indicates how well the kidneys filter and remove unwanted substances from the blood. Patients are injected with 99mTc-DTPA, which is cleared from the blood via the glomeruli within the kidneys. Blood samples are collected 2 and 4 hours later and the level of 99mTc-DTPA remaining is measured using a gamma counter.  

SeHCAT- These studies will provide information regarding the function of the gastro-intestinal system, by imaging the abdominal area following the administration of 75Se-tauroselcholic acid (SeHCAT). SeHCAT capsules are used to study the behaviour of bile acids in the digestive system. 

Patients are given a SeHCAT capsule which behaves in a similar manner to bile acid already present within the body. Images are acquired 3 hours later and the following week using a gamma camera to asses the retention of 75Se.   

Thyrotoxicosis (or hyperthyroidism) is an over functioning thyroid. This can be treated with radioiodine (radioactive 131Iodine (131I)) which, after entering the bloodstream through ingestion, targets only the thyroid cells in the body. This form of radiation treatment can be referred to as “radioiodine therapy”. At QAH, thyrotoxicosis will be treated with a course of antithyroid drug (ATD), such as Carbimazole or Propylthiouracil (PTU). For patients that have suffered a relapse and have already undergone ATD therapy, radioiodine therapy is provided. The aim of the radioiodine therapy is to return the thyroid to a euthyroid (normal) state, although the thyroid activity may go under (hypothyroid) or remain above (hyperthyroid) the euthyroid state. If you remain hyperthyroid, another radioiodine therapy may be subscribed, if you become hypothyroid you may have to take Thyroxine (T4) for the rest of your life. 

Different forms of Thyroid Cancer (e.g. Papillary and Follicular) can be treated with radioiodine (radioactive 131Iodine (131I)) which, after entering the bloodstream through ingestion, targets only the thyroid cells in the body. This form of radiation treatment can be referred to as “radioiodine therapy”. At QAH, differentiated thyroid cancers are initially treated by total or near total thyroidectomy surgery followed up with radioiodine therapy used as an adjuvant treatment. The radioiodine therapy is to improve the outcome of the overall treatment and so decrease the chances of a relapse in thyroid cancer. If relapse does occur, radioiodine therapy will be used as the primary treatment of the residual/recurrent thyroid tissues and cells. 

If you are prescribed radioiodine therapy for the treatment of thyroid cancer, you will be admitted to the designated therapy suite on F5, Oncology ward at QA Hospital. The treatment is given in the form of an iodine capsule which is swallowed. The capsule is smooth and is approximately the size of a Paracetamol. However, if you are unable to swallow capsules, it may be possible to drink the radioiodine in the form of a liquid instead.

When you swallow the capsule, its outer coating dissolves and the radioactive iodine is absorbed into your bloodstream. As the blood circulates around your body, any thyroid cells will readily absorb the radioactive iodine in the same way as non-radioactive iodine is absorbed from the diet. The uptake of iodine in the body is strictly limited to thyroid cells, which means the radiation is targeted to only where it is needed. For several weeks after you swallow the capsule, you will be radioactive. The radioactivity will treat any cancerous thyroid cells remaining in your body. Any radioiodine that is not absorbed by any remaining thyroid cells will pass out of your body through all bodily fluids (predominantly urine).

The regulations governing radiation state that we need to limit the radiation dose received by people who do not need it. Patients are therefore required to remain in therapy suite while Nuclear Medicine Physics staff monitor the residual levels of radioiodine within your body at regular intervals. When they are low enough, you will be allowed to go home. When you leave the hospital, your radiation levels will be a much lower than during your stay. However, there will still be some restrictions that you need to follow including restrictions on the contact and interactions that are had with others. You will be given a written sheet with details of all the restrictions and the Nuclear Medicine Physics staff will advise you in more detail before you leave the ward.

To undergo this treatment, you will be required to go on a low iodine diet for 2 weeks prior to treatment. Also, for 2 hours before and after administration you will not be allowed to consume any food. This is to allow the radioiodine administered to work as effectively as possible. As you will be radioactive, there will be some restrictions that you have to follow upon leaving the ward. These are dependant on the activity that you are prescribed and will be given to you before the treatment date so that you can prepare in advance.

Polycythaemia is a condition where there are too many red blood cells in the blood. One treatment option is an injection of 32Phosphorous (32P) which inhibits the bone marrow’s production of red blood cells. 

89Strontium-chloride (89Sr) is used to relieve bone pain in prostate cancer patients. Areas of bone with metastases contain rapidly dividing cells in comparison to healthy bone and tissue. The 89Sr localises selectively within these areas of bone. It is administered as an injection and delivered to the site where it is needed. The treatment takes effect over a couple of weeks. Pain relief can last from three to six months, although patient responses do vary.  

Treatment with 90Yttrium (90Y) is most beneficial for knee joints with recurrent effusions (fluid collections) which respond temporarily to steroid  injections. It is also a suitable treatment for pigmented villonodular synovitis which is a destructive disease of the synovium (the joint lining). 

The injection is very similar to a steroid injection, but due to the radiation, extra care has to be taken to protect against leaks onto skin  or clothing (staff present will wear protective aprons, shoe covers and gloves). The treatment is delivered as a liquid injection into the  affected joint. 90Y works by treating the inner lining layer of the joint, where the excessive fluid is produced, without causing damage to  outer tissues (the radiation only affects tissues within 3mm of the dose). The effects of the treatment can sometimes be permanent, but  re-growth can occur within weeks, months or even years. In this case it is possible to have further yttrium injections. 

If you have been referred for 90Y treatment, your appointment will be held in the Nuclear Medicine department at QA Hospital. You will not be able  to drive yourself home after the injection, so you will need to arrange to be collected. Loose clothing is advised to allow a splint to be  fitted to your leg. Shorts and skirts are best. The injection will only be given if at least a few drops of fluid can be aspirated from the joint  (ensures the injection is in the right place). A brisk walk in the morning will help a little fluid to collect.

We are currently responsible for the routine quality control procedures that are carried out on all the Gamma Cameras within the department. A number of tests including Centre Of Rotation (COR), uniformity calibration, spatial resolution are performed to assess the suitably of the system for clinical use. 

Breast sentinel lymph node biopsy is a procedure to determine whether breast cancer has spread to lymph nodes. The sentinel node is the first lymph node to receive drainage from the tumour site. Sentinel node biopsy procedures involve an injection of a radioisotope, technetium-99m at the tumour site. The patient is then imaged using a gamma camera to locate the node, and surgery is performed after imaging, using a gamma probe to detect the radioactive node(s).