Justification of CT for Individual Health Assessment of Asymptomatic Persons: A World Health Organization Consultation.

An international expert consultation was convened by the World Health Organization (WHO). The purpose of the meeting was to review the use of CT in examining asymptomatic people. This is often referred to as individual health assessment (IHA). IHA was identified as a global phenomenon unenthusiastically tolerated, and not actively promoted, structured, or regulated in most countries. This paper identifies the state of the art for IHA and some considerations in relation to its justification, in different regions of the world. The outcomes reached include the following: questions around terminology and culture of IHA practice; review of IHA in some countries, regions, and international bodies; dilemmas for participants in IHA; risk communication, education, and training for professions and public; the desirability of guidelines and clinical audit; social, ethical, public health, and resource considerations; and a framework for IHA and regulatory considerations. Three subcategories of examination for asymptomatic individuals were identified: formal screening programs; examinations for which the evidence base or risk profile is incomplete; and opportunistic examinations with little or no evidence or risk profile to suggest they have any merit. The latter challenges the justification principle of radiation protection. In addition, the issue of the costs, direct and indirect, associated with false positives and/or equivocal/incidental findings were highlighted. These and other considerations make it difficult to view some IHA as a bona fide medical activity. To allow it to be viewed as such requires that it be conducted within a robust clinical governance framework that includes regulatory dimensions.

Radiation doses to Norwegian heart-transplanted patients undergoing annual coronary angiography.

Heart-transplanted patients in Norway undergo annual coronary angiography (CA). The aims of this study were to establish a conversion factor between dose-area product and effective dose for these examinations and to use this to evaluate the accumulated radiation dose and risks associated with annual CA. An experienced cardiac interventionist performed a simulated examination on an Alderson phantom loaded with thermoluminescence dosemeters. The simulated CA examination yielded a dose-area product of 17 Gy cm(2) and an effective dose of 3.4 mSv: the conversion factor between dose-area product and effective dose was 0.20 mSv Gy cm(-2). Dose-area product values from 200 heart-transplanted patients that had undergone 906 CA examinations between 2001 and 2008 were retrieved from the institutional database. Mean dose-area product from annual CA was 25 Gy cm(2), ranging from 2 to 140 Gy cm(2). Mean number of CA procedure was 8 (range, 1-23). Mean accumulated effective dose for Norwegian heart-transplanted patients between 2001 and 2008 was 34 mSv (range, 5-113 mSv). Doses and radiation risks for heart-transplanted patients are generally low, because most heart transplantations are performed on middle-aged patients with limited life expectancy. Special concern should however be taken to reduce doses for young heart-transplanted patients who are committed to lifelong follow-up of their transplanted heart.

Radiation doses to children with shunt-treated hydrocephalus.

BACKGROUND: Children with shunt-treated hydrocephalus are still followed routinely with frequent head CT scans. OBJECTIVE: To estimate the effective dose, brain and lens doses from these examinations during childhood, and to assess dose variation per examination. MATERIALS AND METHODS: All children born between 1983 and 1995 and treated for hydrocephalus between 1983 and 2002 were included. We retrospectively registered the number of examinations and the applied scan parameters. The effective dose was calculated using mean conversion factors from the CT dose index measured free in air, while doses to the lens and brain were estimated using tabulated CT dose index values measured in a head phantom. RESULTS: A total of 687 CT examinations were performed in 67 children. The mean effective dose, lens dose and brain dose to children over 6 months of age were 1.2 mSv, 52 mGy and 33 mGy, respectively, and the corresponding doses to younger children were 3.2 mSv, 60 mGy and 48 mGy. The effective dose per CT examination varied by a factor of 64. CONCLUSION: None of the children was exposed to doses known to cause deterministic effects. However, since the threshold for radiation-induced damage is not known with certainty, alternative modalities such as US and MRI should be used whenever possible.