Introduction
Despite the small but definite risk to patients' health, investigations involving radiation are an accepted and fundamental part of medical practice. In the United Kingdom an estimated 100-250 deaths occur each year from cancers directly related to medical exposure to radiation.1 In March 2000, the UK secretary of state issued new regulations that emphasised the importance and dangers of radiation.2,3
We investigated the level of knowledge doctors have concerning radiation doses received by patients when they undergo commonly requested radiological investigations.
Participants, methods, and results
We compiled a questionnaire listing the most commonly requested radiological investigations. Participants were asked to identify the average dose of radiation received when a person underwent a standard chest x ray. This was then used to represent a single dose of radiation, and doctors were asked to estimate the equivalent doses of radiation for various radiological investigations (table).
Table 1.
Equivalent number of doses of radiation for most commonly requested investigations. Dose for chest x ray used as single unit dose of radiation. Figures are numbers (percentage) of doctors with correct answer for each investigation
| Radiological investigation | Equivalent No of chest x rays | No of correct answers (n=130) |
|---|---|---|
| Abdominal x ray | 75 | 2 (1.5) |
| Lumbar spine x ray | 120 | 3 (2) |
| Thoracic spine x ray | 50 | 4 (3) |
| Barium swallow | 100 | 6 (5) |
| Peroperative cholangiogram | 65 | 3 (2) |
| Fixation of fractured neck of femur | 45 | 10 (8) |
| Ultrasound of abdomen | 0 | 124 (95) |
| CT of abdomen | 400 | 8 (6) |
| Spiral CT of abdomen | 300 | 9 (7) |
| MRI of abdomen | 0 | 119 (92) |
| MRI of knee | 0 | 119 (92) |
| MRI of spine | 0 | 119 (92) |
| Leg arteriogram | 400 | 0 |
| Renal arteriogram | 80 | 1 (1) |
| Thyroid isotope scan | 50 | 8 (6) |
| White cell scan | 150 | 2 (1.5) |
CT=computed tomography; MRI=magnetic resonance imaging.
We asked a convenience sample of 130 doctors at all different grades from two separate hospitals (South Wales and Oxford) to take part in the study and interviewed each doctor on a one to one basis. All doctors agreed to complete the questionnaire. There was no negative marking. We accepted a deviation of 20% above and below the correct value (wider variations were allowed for those procedures for which the radiation dose can vary enormously). Correct answers to the questions were derived from information available on the internet4 and counter checked with the Royal College of Radiologists.5
We interviewed 40 senior house officers, 40 specialist registrars, 40 consultants, and 10 consultant radiologists. None of them knew the approximate dose of radiation received by a patient during a chest x ray or even the measurement in units of radiation (0.02 mSv). The minimum score was 0% and the maximum score was 59%. Five doctors (4%) gave no correct answers. The estimated doses of radiation were much lower than the correct doses. For example, a patient undergoing an arteriogram of the leg would receive 400 times the radiation of a chest x ray, but the average mean answer was 26 times—that is, doctors were submitting their patients to a radiation dose that was 16 times larger than they thought it was. The average mean dose of irradiation was six times the quantity estimated by the doctor.
Overall, 97% of the answers were underestimates of the actual dose; six (5%) doctors did not realise that ultrasound does not use ionising radiation; and 11 (8%) did not realise that magnetic resonance imaging does not use ionising radiation.
Comment
In a convenience sample of doctors few had any knowledge about the level of radiation that their patients were exposed to during radiological investigations. Most patients entering hospital will have at least one x ray investigation and usually many more subsequent x rays. It is well known to both the lay public and to medical professionals that although radiological investigations are valuable, they represent a small but definite potential risk to health through exposure to ionising radiation.
The interviewed doctors came from two hospitals in two different regions. Therefore our results may not apply throughout the United Kingdom, but it does seem that most doctors have no idea as to the amount of radiation received by patients undergoing commonly requested investigations, despite them all having undertaken the radiation protection course. This lack of awareness of the degree of exposure to ionising radiation becomes particularly pertinent when we consider the number of patients who receive inappropriate or repeat examinations.
Contributors: SS, AR, and MS questioned the selection of doctors on a one to one basis in the South Wales and Oxford region. SS, MHL, RBG, and KGT wrote and contributed to the final version of the paper. KGT is the guarantor.
Funding: None.
Competing interests: None declared.
References
- 1.Royal College of Radiologists and National Radiological Protection Board. Patient dose reduction in diagnostic radiology. Documents of the National Radiological Protection Board 1990;1:No 3.
- 2.The Ionising Radiation (Medical Exposure) Regulations 2000. www.doh.gov.uk/irmer.htm (accessed 14 Oct 2002).
- 3.Statutory instrument 2000 number 1059. The Ionising Radiation (Medical Exposure) Regulations 2000. www.legislation.hmso.gov.uk/si/si2000/20001059.htm (accessed 14 Oct 2002).
- 4.Health Physics Society. www.hps.org/publicinformation/asktheexperts.cfm (accessed 12 Nov 2001).
- 5.Royal College of Radiologists. Making the best use of department of clinical radiology: guidelines for doctors. 4th ed. London: Royal College of Radiologists, 1998.