Multidetector CT in children: current concepts and dose reduction strategies

Abstract

The recent technical development of multidetector CT (MDCT) has contributed to a substantial increase in its diagnostic applications and accuracy in children. A major drawback of MDCT is the use of ionising radiation with the risk of inducing secondary cancer. Therefore, justification and optimisation of paediatric MDCT is of great importance in order to minimise these risks ("as low as reasonably achievable" principle). This review will focus on all technical and non-technical aspects relevant for paediatric MDCT optimisation and includes guidelines for radiation dose level-based CT protocols.

Fig. 1

Illustration of the fixation of a baby using a vacuum pillow (reproduced with permission from the parents)

Fig. 2

Illustration of the combined ATCM technique for CT of the abdomen. The scanogram shows the calculated variation of the mA per body part, in the frontal (green) as well as the lateral (yellow) projection (Sure Exposure 3D, Toshiba Medical Systems, Otawara, Japan)

Fig. 3

Overbeaming. The X-ray bundle consists of the umbra (dark grey) and penumbra (middle grey), caused by the diverging bundle. In MDCT the penumbra is excluded from detection by the detector array in order to achieve a uniform illumination of the detectors (overbeaming)

Fig. 4

Overranging. In MDCT one section width is automatically added to the planned scan length, so image scan length is slightly longer. Furthermore, at the beginning and end of the imaged scan length an extra rotation is added, necessary for image reconstruction and resulting in a longer exposed scan length. The definition of overranging is either the difference between user planned and total exposed scan length (def 1) or the difference between total imaged and exposed scan length (def 2) (reproduced with permission from [65])

Fig. 5

Illustration of the increase in DLP (%, vertical axis) in relation to the bundle width (mm, horizontal axis) caused by overbeaming (OB) and overranging (OR) in MDCT. a For long scan lengths the DLP slightly changes for a bundle width >10 mm. b For short scan lengths (around 10 cm, children) a bundle width of 10–20 mm is the most optimal in terms of radiation dose (adapted from [66], with permission)