The Role of the Radiographer in Imaging Patients with Hereditary Multiple Exostoses
Peter Machin
Radiographer, University Hospital of North Staffordshire
Many thanks to our Member, Lynda Grisenthwaite, for obtaining the article below. Our thanks go to Peter for taking time out of his busy schedule to write it for us. This article was edited by Dr D. G. Small, BM, BCh, MRCP (UK).
Lateral and AP view of normal wrist
Before discussing the role of the radiographer in the imaging of patients with HME, it is important to understand certain key principles. These include the processes of bone growth, radiation safety concerning x-rays and the systems that are in place to protect the patients from the over exposure to medical radiation.
The Process of Bone Growth
All the bodys long bones (e.g. the humerus in the upper arm, radius and ulna in the lower arm, femur in the upper leg and the tibia and fibula in the lower leg) develop through growth plates at either end of the shaft of the bone. Growth occurs during childhood by the production of bone at the epiphyseal plate, at the side nearest to the shaft of the bone. The growth is not always equal.
An exostosis is a lump on a bone resulting from a disorder of the growth plate, where bone growth occurs sideways instead of along the length of the bone. As the bone lengthens the exostosis remains static, so becoming a bony outgrowth close to the end of the bone. Exostoses commonly occur at the knee, shoulder and wrist. A single exostosis is common, occurring in approximately one in 200 people. Multiple exostoses are a lot rarer. A recent American study claims these affect one in 50,000 people. The condition is usually hereditary, about 90% of cases being inherited from one or other parent, but in 10% there is no familial history of multiple exostoses.
The Use of Ionising Radiation
As you wait outside an x-ray room you may notice the radiation warning lights. These consist of permanently lit yellow lights and red lights that illuminate when an x-ray exposure is being made. These are to alert people that ionising radiation is being utilised, so that they do not enter the room during an exposure and receive an unnecessary dose of radiation.
Every time a person has an x-ray examination, they receive a dose of ionising radiation. However the associated risk is minimal and is outweighed by the need for a diagnosis. This is known as "the benefit risk ratio". Any benefit gained from a medical exposure must outweigh the risk. The risk is that an exposure to medical ionising radiation can cause a change in the body and lead to a possible cancerous formation. This may sound worrying, but there is no need to be concerned, as the radiation dose received by patients during plain x-ray examinations is very small. A person can receive a greater radiation dose on a plane flight to Spain then from an x-ray of the wrist or shoulder. A chest x-ray has a 1 in 1,000,000 chance of producing a possible cancer. Images of the bodies’ extremities - hands, feet, arms, knees, legs and shoulders - carry even less risk.
The world around us contains many sources of naturally occurring radiation. These include:
- Cosmic radiation: entering from outer space and makes up 10% of our total radiation exposure from all sources. The higher you are, the more you receive, hence the radiation dose received on plane flights.
- Radon gas: from the decay of naturally occurring deposits of uranium in the earths crust, such as the decay of granite. This makes up 50% of our total radiation exposure from all sources.
- Product from the ground and building materials: naturally occurring isotopes are present in sand and concrete which decay releasing background radiation.
- Food and drink: found in mineral based products, e.g. spring water, vegetables which take nutrients from the soil, and animals which eat grass containing these isotopes.
People hear the word "radiation" and think of man made disasters such as at Chernobyl and Three Mile Island, where the radiation leaks were massive, compared to the naturally occurring background radiation and medical examination radiation doses.
Hopefully these facts will put your mind at ease about the radiation dose received by patients during medical examinations.
Radiation SafetyThere are regulations in place to stop the over-use and the over-exposure of patients to x-rays. The most recent are the Ionising Radiation (Medical Exposure) Regulations (IR(ME)R) introduced in 2000.The first and most important rule is the justification of the image through the benefit risk principle. The benefit gained from the radiograph must outweigh any possible risk that may result from the received radiation dose. Secondly, x- ray images can only be requested by people who have been medically trained to do so. These include consultants, surgeons, doctors, dentists, clinicians and nurse practitioners. So before a patient even gets to the imaging department for an x-ray, his or her case will have been carefully considered.
Once in the x-ray room, the systems to keep the radiation dose to a minimum continue. Radiographers work to a principle known as ALARP, which stands for “As Low As Reasonably Practicable”, to reduce the risk of medical irradiation. This is achieved by using the correct equipment and technique for the examination, the careful positioning of the area to be imaged (as will be discussed later) and competently trained staff.
Radiographers aim to keep the radiation dose to a minimum. This is achieved in several ways:
- Collimation (restriction) of the x-ray beam to minimise the irradiated area of the patient. This area is identified by a projected light on the patients’ skin.
- Exposure: the correct exposure to obtain the optimum image whilst keeping the radiation dose to a minimum.
- Accurate positioning of the area under investigation to obtain the correct image first time. This reduces the need for repeating an x-ray which would increase the radiation dose.
- Blocking x-rays with lead shields, in order to protect sensitive areas of the patient such as the reproductive system.
Radiographers have to train for three years, splitting the time between studying at university and undertaking practical work in imaging departments. The qualification gained is a BSc (Hons) degree in diagnostic radiography. After qualification, radiographers have to register with the Health Professions Council (HPC). The HPC sets national standards that seek to protect the general public by ensuring that its members are safe and effective in their practice. Radiographers must be registered to be able to practice and work with the general public. Membership of the HPC has to be renewed every 2 years. To maintain their registration, radiographers must continue to develop their skills, knowledge and radiographic techniques. This is known as Continual Professional Development (CPD). Failure to do this will result in being struck off.
As with all medical staff, radiographers are subject to Criminal Record Board (CRB) checks to establish that they have no previous criminal convictions. If they commit any crime against a person such as assault or a criminal offence such as drink driving or fraud they will be struck off immediately and not permitted to practice.
The X-Ray Image and Medico-Legal DetailsAs patients are called into the x-ray room by the radiographers or imaging department assistants (IDA’s), they need to be positively identified by confirming the patient’s name, date of birth, address and postcode and/or hospital unit number. This is to reduce the risk of x-raying the wrong patient. The radiographer will also confirm with you the area which they are about to x-ray. This is to ensure that they gain informed consent from the patient prior to undertaking the examination.
Exostoses can be seen on radiographs (x-ray images). The x-ray outlines of bone are usually smooth. Multiple exostoses can be seen as a rough bony outgrowth just below the head of the bones. X-rays are used by orthopaedic surgeons to assess the condition of the bone and to guide any surgical treatment that may be required. Images are often required from different angles, usually at 90 degrees to each other. These are typically an antero-posterior (AP) projection, imaged with the x-ray tube in front of the patient, and a lateral projection, with the x-ray tube to the patient's side.
It is the responsibility of the radiographer to acquire the best quality of images for the consultants and surgeons. Images also need to be correct anatomically and show sufficient detail. For example, when x-raying a knee, the AP projection has to include the lower third of the femur and the upper third of the tibia and fibula and the patella (kneecap) positioned centrally between the femoral condyles. To achieve this the whole of the patients leg needs to be turned inwards. The lateral projection can be achieved either by turning the patient onto their affected side or by padding the knee up and using a horizontal x-ray beam. The lateral knee image should show the medial (inside) and lateral (outside) condyles of the femur superimposed. A anatomical marker, the metal letter R or L, should be seen on all images. This is placed on the x-ray cassette, to confirm that the correct side of the patient has been imaged.
AP and lateral views of normal knee
Once the x-ray has been taken, it needs to have the patients name, date of birth, hospital unit number, the time and date the x-ray was taken and the hospital where the examination took place recorded on the image. In conventional radiographical systems, these details are on an identification card and are photographed onto the x-ray film. In digital systems, the details are input into a computer and transferred onto the film prior to taking the x-ray. It is absolutely vital to ensure that the correct patients’ details are on the correct image!
The job of the radiographer is varied and interesting. Many types of medical investigations are conducted throughout the working day. The orthopaedic work of imaging patients with fractures and possible HME is just one facet of a radiographer's career. The training undertaken is extensive, with post graduate study required to specialise in areas such as CT, MRI, Ultrasound and Interventional radiography. Above all, radiographers have to ensure a high quality of work, including patient care, comfort and safety, and gaining optimum image quality by positioning the patient and using the correct exposure. The images must also include the correct patient details and anatomical marker. Maintaining a safe and clean working environment is paramount, as is reducing the radiation dose to the patients.
I hope this brief explanation of the role of the radiographer has given some insight into the varied and interesting tasks that must be carried out when x-raying patients with HME.