the clinical findings. Treatment on imaging findings alone can be detrimental to athletes’ health as well as their careers (3).

Suitability, timing and accuracy of the investigation Using the appropriate modality and timing investigations well are important for getting the most out of imaging. For example, radiograph images have sensitivities as low as 15% for stress injuries to bone; and radioisotope bone scans are more sensitive for detecting stress fractures but have low specificity and poor resolution. On the other hand, magnetic resonance imaging (MRI) is extremely sensitive to oedema and is the modality of choice but it needs to be used appropriately (3–5). In a patient with pain that is suspicious for stress injury, the initial imaging should be with radiography, but with a low threshold for proceeding on to MRI or scintigraphy. Influencing management Imaging should be used either as a means to obtain further information or as a problem-solving tool. Its influence on management is important when requesting the examination because multiple investigations can confuse the diagnosis and may result in inappropriate – even ineffectual – treatment of the athlete. Imaging always works best when it addresses a distinct clinical question such as: “Is there a muscle tear?” or “Is there tendonopathy?”.

Communicating clinical details The request for an imaging investigation should include relevant clinical findings and a list of the differential diagnoses. It is also helpful if you state a specific question to be answered; this removes any ambiguity and allows the findings to be interpreted properly. The request also allows the radiologist to identify the most appropriate modality for imaging (3,6).

Quality of the examination A low-quality examination may not provide all the clinical information that is necessary for answering the diagnostic question and may, in fact, lead to further confusion. This is why it is important to obtain the best quality investigations possible.

Developing close working relationships with the investigators It is important to develop close working relationships with the investigators when interpreting investigations. Often what is not said may give some clue to understanding the diagnosis. A close working relationship between the referrer and the radiologist also helps to clear up any ambiguity in the request and report, so maximising the benefit gained by the patient from imaging.

Explaining the investigation to the patient Communicating clearly to patients the techniques used during imaging as well as the findings and potential management implications can improve their compliance. As image-guided therapies have become more widely used, patients need to be made aware of the procedures involved (3). Referrers should try to familiarise themselves with the various imaging techniques as much as possible.

IONISING RADIATION AND RISKS It is very important to appreciate that some radiological

8

TABLE 1: TYPICAL EFFECTIVE DOSES OF RADIATION DURING DIAGNOSTIC MEDICAL EXPOSURE (8)

Diagnostic procedure

Typical effective Equivalent no. dose (mSv)

Radiographic examinations Limbs and joints

(except the hip) Chest (single PA film) Skull

Thoracic spine Lumbar spine Hip

Pelvis

Abdomen CT head CT chest

CT abdomen or pelvis <0.01

0.02 0.06 0.7 1.0

0.4 0.7 0.7 2.0 8.0 10.0

Radionuclide studies Bone (technetium-99m) 4.0 PET head (F-18 FDG)

5.0 <0.5 1 3

35 50 20 35 35

100

400 500

200 250

of chest x-rays

Approximate equivalent period of natural

background radiation* <1.5 days

3 days 9 days

4 months 5 months 2 months 4 months 4 months 10 months 3.6 years 4.5 years

1.8 years 2.3 years

*UK average background radiation is 2.2 mSv per year; regional averages are 1.5–7.5 mSv per year.

Abbreviations: FDG, fluorodeoxyglucose; PA, posterior–anterior; PET, positron emission tomography.

imaging techniques employ ionising radiation and therefore they carry inherent risks of radiation exposure (6,7). Table 1 shows the typical radiation doses used in various radiographic and radionuclide investigations. Suffice to say, such investigations should involve as little ionising radiation as possible while preserving clinically efficacy.

INDICATIONS FOR IMAGING The main indications (1,2) for imaging are: n For a clinical diagnosis that is uncertain and management may be affected by the findings. n When a systemic or sinister abnormalities needs to be excluded (“red flag” signs). n If the extent of an injury and its associated complications need to be fully investigated. n When there has been a failure of treatment and the reason is not obvious. n For medicolegal reasons to document the disease and its progress or resolution.

MODALITIES OF IMAGING

A number of different imaging modalities can be used to diagnose injuries. These are plain radiographs, ultrasound (US),

SUBSPECIALTY IN MUSCULOSKELETAL RADIOLOGY

SPORTS IMAGING HAS NOW BECOME A DESIGNATED

sportEX medicine 2010;43(Jan):7-10