BJRD15819 1..8

25 years ago, on a Friday evening at 9 pm, the emergency department (ED) was full of patients with a wide range of clinical problems. Their investigations included plain radiographs, but no other imaging was included until the next working day. At present, many patients are receiving advanced imaging such as ultrasound, CT and MRI, often delivered out of hours—an obvious advance for patients or sometimes an unnecessary development? In this article, we will consider how to assess patient benefits and whether increased use of advanced imaging is an overall advance for patients. We will address the general implications for healthcare services which come with greater use of advanced imaging. We will then address the effect of advanced imaging on individual fictional ED patients with a variety of complaints. GENERAL CONSIDERATIONS The use of advanced imaging for emergency department (ED) patients has taken off in the past 15 years, from 1998 to 2007, the use of CT or MRI for injured patients increased three fold in the USA, without an increase in the number of diagnosis of life-threatening conditions (such as skull fracture or cervical spine injury) or admission rates. For other ED presentations (such as headache and chest pain), a similar increase in CT use has been demonstrated, rising by a factor of almost five times between 1995 and 2007, with no evidence that this increased use is levelling off (Figure 1). This represents both increased use of scanning for the same indications (i.e. a lower “threshold”) and an increasing number of reasons to use advanced imaging. There are multiple factors which have both pulled and pushed the increased use of advanced imaging in the ED. Technology has been a “pull” factor for ultrasound, CT and MRI. Ultrasound machines have become smaller, more portable and with greater image quality, leading ED physicians to routinely use ultrasound at the bedside. Indeed, competence in basic ultrasound is a core training requirement for ED registrars in the UK with clearly defined measures of competency. similarly, in Australia, the use of ultrasound is regulated by Medicare reimbursement, and there are stringent training requirements. However, despite this, the use of ultrasound by non-radiologists without high standards of prescriptive training is increasing. CT in particular has improved in both image quality and scanner efficiency, leading to CT replacing plain films and conventional catheter angiography. Plain films are also being supplemented with MRI: the development of low-field peripheral MRI scanners has made it possible to perform dedicated musculoskeletal imaging for acute injuries. Ultrasound, CT and to a lesser extent MRI scanners have become increasingly available, and CT in particular has a greater proximity to EDs, allowing clinicians to easily access rapid, minimally invasive, high-resolution imaging which is reproducible. Other technological developments such as teleradiology and voice recognition enable a timely and accurate diagnosis to be communicated promptly to guide clinicians to appropriate treatment. Factors which “push” the clinician towards more advanced imaging include the introduction of the “four hour” ED rule (in the UK and Australia) as well as the type of hospital setting. Academic or urban centres demonstrate higher use of advanced imaging perhaps because patients are more likely to see a training grade doctor. Patient expectation and fear of malpractice litigation are other likely precipitators. In 1984, missed appendicitis was the most frequently successful malpractice claim against Emergency Physicians study; since then, the use of advanced imaging for suspected appendicitis has become almost routine (see fuller discussion later). Increased use of advanced imaging does have disadvantages. Cost is a consideration. At our institutions (three Academic Hospital Centres in the UK and Australia), the costs are as follows: abdominal X-ray (AXR), mean £31 ($47); ultrasound, mean £53 ($81); abdominopelvic CT, mean £196 ($ 298); and one-part MRI, mean £209 ($317). The mean cost of one night’s patient stay on a standard medical ward is £673 (US$1021) across our institutions, whereas the cost of an outpatient’s visit is £136 ($206). The cost to a patient is also important and requires a complex cost benefit calculation taking into account many variables including disruption of work and other responsibilities. An important, but easy to overlook, consequence is that increased use of advanced imaging has been shown to increase length of visit to the ED, leading to ED crowding and potentially indirectly increasing the risk of medical error. At the very least, this requires re-organization of ED services to accommodate patients awaiting imaging results with implications for healthcare planning and resource allocation, whether in private care, an insured system or in a public hospital. Other disadvantages of advanced imaging include the effects of the risk of ionizing radiation (IR) from CT, which is particularly important in young patients. 1–2% of all cancers in the UK and USA may be associated with exposure to IR from CT which is one of the largest sources of radiation exposure overall. The effective doses of radiation from CT of the body range from 10 to 23mSv (highest in trauma) compared with an annual background radiation dose of 3mSv. On an individual level, 10-mSV CT in a 25-year-old patient is associated with a risk of induced cancer of 1 in 900 individuals and a risk of fatal cancer in 1 in 1800 individuals. Increasingly, it is recognized that Figure 1. Exponential growth in advanced imaging use. Graph illustrates percentages of emergency department (ED) visits involving CT from 1995 to 2007. Data points indicate national estimates of percentages of ED visits involving CT based on the sample data. Solid line 5 exponential model based on the data. Error bars 5 95% confidence intervals. Reproduced from Larson et al with permission from The Radiological Society of North America. Table 1. Final diagnoses assigned by expert panel Final diagnoses in 1021 patients Number (%)