Mannudeep K. S. Kalra MD, Presenter: Medical Advisory Board, General Electric Company Research grant, General Electric Company Faculty, General Electric Company Consultant, Bracco Group

Anders Persson MD, PhD, Abstract Co-Author: Nothing to Disclose

Petter Quick, Abstract Co-Author: Employee, Siemens AG

Michael Sandborg PhD, Abstract Co-Author: Consultant, ContextVision AB, Linköping, Sweden

To minimize radiation dose associated with whole spine CT in children with scoliosis using low kVp, lowest tube current and high pitch and fast table speed.

We performed whole spine CT for scoliosis in 19 children (age range 2-18 years, mean age 13 years, 12 girls, 7 boys) on 128-slice dual source MDCT (128-DSCT, Siemens Definition Flash). All scanning parameters were held constant at 3.0:1 pitch, 128x0.6mm detector collimation, 115.2mm table feed per gantry rotation, 0.28second gantry rotation time, 100kVp, and 1 and 3mm reconstructed sections at 50% overlap using B18f reconstruction kernel. Lowest possible quality reference mAs value (image quality factor for xyz- automatic exposure control or xyz-AEC, CARE Dose 4D) was selected on a per patient basis. Average mAs and projected estimated dose savings with xyz-AEC were recorded. CTDIvol and DLP were recorded. CT numbers and image noise were measured in vertebral bodies and air and signal to noise ratio (SNR) was estimated. Artifacts were graded on 4-point scale (1=no artifacts, 4=severe artifacts). Ability to identify vertebral and pedicular contours, and measure pedicular width and degree of vertebral rotation was graded on 3-point scale (1=reliable, 3=unreliable).

All whole spine CT were deemed as reliable for identifying vertebral and pedicular contours as well as for measuring pedicular width (5.4±0.9mm) and degree of vertebral rotation (19.3±9.3degrees). Mean objective image noise and SNR were 56.5±22.9 and 16.3±9.7, respectively. With a mean quality reference mAs of 13, the scanner employed an average actual effective mAs of 9.5±3.5 (range 6-17mAs) with an estimated radiation dose saving of 42.9±18.6% with xyz-AEC compared with fixed mAs. Mean CTDIvol, DLP and effective doses were 0.4±0.2mGy (0.2-0.7), 20±9mGy.cm (8-41) and 0.3±0.1mSv (0.12-0.61), respectively.

Radiation dose for whole spine CT for evaluation of scoliosis in children can be minimized to less than one-third of a milliSievert while maintaining diagnostic image quality with high pitch-high speed scanning using xyz-AEC and low kVp.

Minimization of CT radiation dose for scoliosis evaluation can be achieved using high beam pitch, lowest possible tube current with xyz-AEC and low tube current on a 128-slice DSCT.

Kalra, M, Persson, A, Quick, P, Sandborg, M, Combination of Low KVp, Lowest Tube Current, High Pitch, and Fast Table Speed for Minimizing Radiation Dose for Whole Spine CT Imaging of Children with Scoliosis.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9013414.html