CT scanning: patterns of use and dose

Abstract

CT scanning is a relatively high-dose procedure. In spite of the use of magnetic resonance imaging, with faster CT scanners and helical techniques CT is becoming more common. There are few data from practice in the United States regarding the age and sex distribution of patients receiving CT scans, what type of scan and how many scans they receive, or how much radiation dose CT scans contribute. We reviewed over 33,700 consecutive CT examinations done at our institution in 1998 and 1999. Information on the types of scans as well as the age and sex distribution of the patients was determined. Between 1990 and 1999, CT examinations in our institution increased from 6.1% to 11.1% of all radiology procedures. Nineteen per cent of all patients seen in our department in the last year had at least one CT scan and more than half had multiple scans on the same day. Thirty-six per cent of all patients had a prior CT examination done on an earlier date. The male/female ratio of patients was 56/44. Studies of children age 0-15 years comprised 11.2% of scans. The highest percentage of scans was done in the 36-50-year-old age group. CT scanning accounted for 67% of the effective dose from diagnostic radiology. In most large hospitals in the United States CT scanning probably accounts for more than 10% of diagnostic radiology examinations and about two-thirds of the radiation dose. Most patients have multiple scan sequences. Studies done on children are probably more common than previously thought.

The Validity of 3dMD Vultus in Predicting Soft Tissue Morphology Following Orthognathic Surgery

“…The original processing time for a full CT scan required up to 9 hours of computer time, but as computer processor speeds have increased and software is refined, processing the large amount of data arriving from the scan has reduced to minutes (Baumrind, 2011;Dawson, 2011). Other advances have included scanners with multiple x-ray emitters and multiple sensors, further reducing the time required for full body scans and the presence of motion artefacts (Mettler et al, 2000).…”

Minimization of radiation exposure due to computed tomography in inflammatory bowel disease

“…CT has been reported to represent 10% of all studies using ionising radiation, while accounting for two-thirds of the overall radiation dose to patients [18]. The three principal ways of reducing the overall radiation dose from CT in the population include limiting the use of CT scanning to those clinical scenarios where the examination is unequivocally indicated and likely to change patient management, the use, where feasible, of alternative imaging modalities such as ultrasonography and MRI which do not result in exposure to ionising radiation, and when CT is indicated, the use of lowdose CT protocols, which utilise all available CT technology developed for radiation dose optimisation, ensuring that a diagnostic quality CT study is acquired at lowest possible radiation exposure [19].…”

Imaging strategies to reduce the risk of radiation in CT studies, including selective substitution with MRI

“…It is important to realize that CT doses are much higher than conventional radiography doses (7,(35)(36)(37)(38), and that the effective dose for a chest CT is approximately 100 -1000 times larger than that for a corresponding chest x-ray examination. Table 1 shows the average effective doses used in 16 common x-ray procedures in 19 western countries, and illustrates that patient doses in CT are much higher than those in most common radiographic examinations (7).…”

“…Furthermore, published frequency data mask the number of times a single patient receives multiple CT examinations (37) and the common practice of multiphase CT scanning, both of which increase the radiation dose (and potential risk) in a cumulative manner (20,39). It has been estimated that 30% of all individuals who undergo CT will be examined at least three times (37).…”

“…CT is responsible for the largest component of medical radiation, which is by far the largest source of man-made exposures of the population (20). Although CT in a typical U.S. hospital represents only ϳ10% of all x-ray imaging, the radiation from CT accounts for up to 67% of all medical radiation (20,37). CT use in the U.S. has been growing rapidly since the mid 1990s, and shows no sign of abating (44).…”