Unnecessary radiation exposure from medical imaging in the rheumatology patient

Our responsibility to change The clinical and scientific benefits of imaging in contemporary medicine are well established, and the rheumatology patient is no exception. If ordered prudently, with full awareness of the risks, the benefits of imaging procedures supersede the risks. For example, in SSc, identification of diagnosis, disease severity and prognosis is best achieved when clinical judgement is integrated with imaging assessment of lung fibrosis (chest CT), pulmonary hypertension (cardiac catheterization), lung inflammation (gallium scintigraphy), coronary anatomy (64-slice cardiac multi-detector CT) and myocardial ischaemia (cardiac stress perfusion scintigraphy) [1]. However, the test warranty expires after 1 year and such imaging can potentially be repeated at yearly intervals over the lifetime of the patient. Following the definition of the American College of Cardiology Foundation, an appropriate imaging study is one in which the expected incremental information, combined with clinical judgement, exceeds any expected negative consequences by a sufficiently wide margin [2]. Negative consequences include the risks of the procedure itself (i.e. radiation or contrast exposure) and the downstream impact of poor performance [i.e. delay in diagnosis (false negative) or inappropriate imaging diagnosis (false positives)]. In practice, 20–40% of all imaging tests may be inappropriate [3], implying potential harm without benefit for many patients undergoing imaging and leading to excessive delays for other patients needing examinations. This places an exorbitant cost on society, with no clinical improvement and possibly even a reduction in care quality [3]. On the other hand, radiation-free techniques may also have risks and substantial limitations. For instance, easy access to US technology can, in itself, actually become a problem in clinical practice. Even though an echo scan is simple to obtain, skill in interpretation cannot be acquired in a few days or weeks and since the technique is highly operator dependent, its interpretation is mostly visual and subjective. Even the ordering pattern of such a test may be distorted by financial incentives because it can be performed in a physician’s office. In the absence of a strict system of licensing and quality control, this may cause an epidemic of self-referral and inappropriate testing [4, 5]. In addition, all imaging techniques (ionizing and non-ionizing) are often overused for consecutive follow-up examinations. European Union medical imaging guidelines list investigating too often and repeating investigations that have already been done as two of the top six reasons of inappropriate imaging examinations [3]. None of the imaging examinations are free, and they imply a financial and safety cost [6]. For a resting cardiac imaging test, taking the average cost (not charge) of an echocardiogram as equal to 1 (as a cost comparator), the cost of a CT or SPECT is ∼3-fold, MRI 6-fold, PET 14-fold and cardiac catheterization 20-fold [6]. Non-invasive imaging techniques are also not without risk. Risks can be acute (linked to stress in the case of stress imaging), subacute (linked to contrast use) and long term (linked to radiation). The order of magnitude of the risks of several imaging techniques (or associated procedures, such as stress or contrast administration) is shown in Fig. 1, and may range between 1–10% (contrast-induced nephropathy) and 0.1–0.3% (severe reaction during stress administration). Although very rare, life-threatening reactions have also been observed with contrast echocardiography (up to myocardial infarction and ventricular fibrillation) and paramagnetic contrast inducing systemic nephrogenic fibrosis in patients with pre-existing renal failure. Last, but not least, long-term effects linked to use of ionizing techniques have also been recognized as a relevant source of risk, which should be considered in the risk–benefit balance when evaluating the test’s appropriateness [2, 3, 6]. On the x-axis, three different types of imaging risk, due to stress administration, contrast injection and radiation exposure. On the y-axis, the magnitude of associated risks. Dob: dobutamine stress; dip: dipyridamole stress; exe: exercise stress. Unfortunately, extensive recent data show substantial unawareness of radiological doses and risks, not only for patients, but also for prescribing and practising doctors [7]. It is, therefore, important to have a clear awareness of the doses of individual radiological examinations commonly used in rheumatology practice, and of their corresponding risks [8]. At the individual level, the effective dose is expressed in milliSievert (mSv). This provides an estimate of the whole-body dose and is a measure of the biological effects. One mSv corresponds to the dose equivalent of 50 chest X-rays (single postero-anterior projection = 0.02 mSv). The typical effective dose of several common diagnostic procedures frequently ordered in rheumatology patients is detailed in Table 1 [3, 9]. Doses are linearly related to the corresponding additional attributable lifetime risk of cancer per examination [7, 8]. These risks are age and gender averaged. In the individual patient, the risk is 37% higher in women than men, 3- to 4-fold higher in children than in adults and reduced by one-half in elderly subjects [8]. As an example, the attributable cancer risk for a cardiac multi-detector CT with a dose equivalent to ∼750 chest X-rays, gives a lifetime extra risk of one cancer in every 750 of exposed adult males, one in 500 of exposed adult females and one in 100 of female children <1 year of age [8]. The radiologic risk is cumulative in nature with every exam adding dose and therefore risk. Estimated radiation dose for common imaging examinations AHA 2009: American Heart Association statement 2009 [9]; EC imaging guidelines 2001: European Commission Imaging Guidelines 2001 [3]. aUnits are median (range). Estimated radiation dose for common imaging examinations AHA 2009: American Heart Association statement 2009 [9]; EC imaging guidelines 2001: European Commission Imaging Guidelines 2001 [3]. aUnits are median (range). Access to multiple imaging tools allows doctors to minimize the contraindications and limitations of each technique and tailor the best (most effective) test to individual patients. The best choice should consider the test with the lowest cost (for any given accuracy) and, most importantly, the test with the lowest acute, chronic and long-term risks. There should be special regard for the radiation issue. European Union guidelines state that ‘for instance, because MRI does not use ionizing radiation, MRI should be preferred when both CT and MRI would provide similar information and when both are available’ [3]. Ionizing imaging procedures should be conducted only when there is appropriate justification for ordering and performing each procedure, with careful optimization of the radiation dose during each procedure [3]. Our rheumatology patients, often young at disease onset and female, are therefore especially sensitive to radiation damage. The chronic nature of most rheumatic diseases also makes our patients more vulnerable to the cumulative effects of serial testing, as we monitor the course of disease and response to therapy. Our imaging often focuses on the chest, and the female breast is a highly radiosensitive organ. The radiation issue is relevant, not only for the individual patient [7, 8], but also to society [10, 11]. Small individual risks multiplied by millions of examinations become a significant population risk. The next challenge is to maintain the high levels of information achieved with modern diagnostic imaging, with a preference for the use of less risky techniques, e.g. chest sonography instead of CT for lung fibrosis; transthoracic resting and stress echocardiography instead of cardiac catheterization for pulmonary hypertension; MRI instead of radiology for gastrointestinal tract and skeletal systemic involvement. It is a challenging opportunity for the rheumatology community to play a proactive role in implementing in clinical practice the recent landmark recommendations of the US Food and Drug Administration [12], aimed at optimizing patient exposure to radiation from medical imaging exams, thereby reducing related risks while maximizing the benefits of these studies: ‘each patient should get the right imaging exam, at the right time, with the right radiation dose’ [12]. Disclosure statement: The authors have declared no conflicts of interest.