Radiation dose optimization for computed tomography of the head in pediatric population – An experimental phantom study

There is an increase in pediatric Computed Tomography (CT) imaging with advancement in technology but CT radiation dose produces significant adverse effects. The objective of this experimental phantom study is to develop an age-based low-dose pediatric CT head protocol.

Polymethyl methacrylate (PMMA) pediatric head mimicking phantom scanning was performed on a CT scanner using various combinations of tube voltage (kV) and product of tube current and exposure time (mAs) setting. Images were reconstructed by iterative reconstruction iDose4 level 1-5.  Quantitative assessment of image quality (IQ) was done by calculating Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR), and Image Noise (IN). Radiation dose indices (RDI) were measured by recording Volumetric CT Dose Index (CTDIv) and Dose length product (DLP). Figure of Merit (FOM) was calculated to study overall effects between IQ and RDI. IQ and RDI obtained using different exposure settings were compared.

Optimized age-based low-dose protocols were developed based on IQ analysis and RDI. For pediatric CT head, with age less than one year kV and mAs of 80 and 150 and for one–five years age kV and mAs of 100 and 200 with iDose4 level-3 was found to be optimum low dose protocol.

The experimental phantom study concluded that with use of low kVp and mAs, radiation dose was reduced to 62% for less than 1-year age group and 51% for 1-5 year age group and also with use of iterative reconstruction technique iDose4 level-3 diagnostic image quality was maintained.