A practical approach to the first iteration in the optimization of radiation dose and image quality in CT: estimates of the collective dose savings achieved

Abstract

CT is a diagnostic imaging modality giving higher patient dose in comparison with other radiological procedures. It contributed an estimated 20% to the collective effective dose to the UK population from medical X-rays in 1990, rising to an estimated 40% in 1999. Tremendous national effort has been expended in reducing patient doses from other radiological procedures with considerable success, but much of the collective dose reduction achieved has been offset by a corresponding increase in the collective dose from CT. Over a period of about 2 years, following the installation of a helical CT scanner, CT scan parameters in this hospital have been adjusted with the aim of working towards optimization of image quality and patient dose. A 33% reduction in annual collective effective dose has been achieved, from about 16.5 manSv to 11 manSv. However, despite this dose reduction, the annual collective effective dose to our sub-population is 2.8 times the value 9 years ago. The increase is almost entirely the result of an increased application of CT; 6149 examinations per annum in 1999 compared with 2210 in 1991. The crucial importance of reducing patient doses from this modality is discussed. Indicative effective doses and image noise values are presented for examination protocols approaching optimization.

Comparison of Different Body Size Parameters for Individual Dose Adaptation in Body CT of Adults

“…For comparison, an x-ray attenuation-based estimate was calculated from the topogram (topogrambased estimate [E topo ]). 2 These body size parameters were correlated with the D w (water-equivalent diameter). D w is used to summarize the individual x-ray attenuation properties of the scanned body region by means of a single number and thus may be useful for adaptation of individual CT dose.…”

“…Water is a major component of body tissues (21), and the x-ray attenuation coefficient for water is approximately 2 The E topo for a water-equivalent diameter (D w ) was calculated by using a simple equation, derived as follows: The posteroanterior topograms acquired with the CT system used in this study present air with a pixel value of Ϫ1000 arbitrary units. Parts of the body are presented with higher pixel values depending on the total x-ray attenuation along the line of projection through the body.…”

Survey of computed tomography techniques and absorbed dose in Italian hospitals: a comparison between two methods to estimate the dose–length product and the effective dose and to verify fulfilment of the diagnostic reference levels

“…As a result, proper management of patient doses and adherence to the European Guidelines on Quality Criteria in Computed Tomography have become an important aspect of clinical practice [6][7][8][9][10][11].…”

A method for benchmarking CT scanners

“…Extensive studies of radiation dose to patients and other studies on image quality assessment have been performed [3][4][5][6][7][8][9][10][11][12] . These studies resulted in useful recommendations on ways to reduce patient dose while maintaining radiologically acceptable image quality.…”