Dianna M. Ehrhart Bardo MD, Presenter: Consultant, Koninklijke Philips Electronics NV Speakers Bureau, Koninklijke Philips Electronics NV, Author, Thieme Medical Publishers, Inc

Jeffrey Harold Yanof PhD, Abstract Co-Author: Nothing to Disclose

Donna M. Stevens MS, Abstract Co-Author: Nothing to Disclose

Efrat Shefer PhD, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Galit Kafri PhD, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

Jens Wiegert PhD, Abstract Co-Author: Employee, Koninklijke Philips Electronics NV

This study aims to investigate PSDE which considers individual body habitus, attenuation /absorption characteristics of tissue and material included in pediatric CT using a Monte-Carlo simulation tool. Another aim is to devise a method to determine CT dose from scatter radiation and the proportion of scatter to displayed CTDIvol. Measures of all components of CT radiation; direct beam, over-ranging, and scatter are made with improved accuracy to produce a PDSE dose profile and compared to SSDE and CTDIvol.  

IRB approval was granted to review 15 pediatric CT & CTA exams, 8 male, 7 female, ages 6 days to 15 years. HU of each image voxel was used to categorize tissues into 6 material classes based on physical composition and chemical stoichiometry. PSDEs were computed from voxelized CTDMs using the Monte-Carlo method, integrating dose or energy in individual patients, taking into account tissue density. A Student’s paired T-test was used to compare the mean values of CTDIvol-normalized PSDE and SSDE for chest and abdomen regions. Display of radiation dose in CTDMs is designed to visually indicate areas of greater and lesser dose on a color scale, with scatter dose displayed separately and in total.  

CTDMs show that dose generally increases with decreasing patient size. The general trend of average normalized dose vs. patient size tends to agree with the SSDE. The calculated PSDE dose profile is greater in smaller diameter patients. Patient specific dose profiles of PSDE vary along the z-axis indicating variation of dose throughout the irradiated volume which depends on effective diameter, tissue type and position within the irradiation field. PSDE values for infant chest/cardiac CTA exams were greater than CTDI-normalized SSDE. In older/larger patients, increased diameter, which increases attenuation of x-rays, skews the PSDE less than the SSDE.  

PSDE provides an accurate and individualized measure of radiation dose imparted during CT scan. CTDMs depict dose distribution within each slice. CTDMs and PSDE enable understanding of dose in different tissues, using varied scan protocols and are especially important in understanding imparted CT dose in infants.

The importance of accurate, patient specific dose estimation and reporting in the youngest and smallest patients is most vital. In children, the accurate estimation and calculation of dose in clinica

Bardo, D, Yanof, J, Stevens, D, Shefer, E, Kafri, G, Wiegert, J, Patient-Specific CT Dose Maps (CTDM) and Patient-Specific Dose Estimates (PSDE) for Pediatric CT: Preliminary Results in Comparison with the CTDIvol and Size Specific Dose Estimate (SSDE).  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13028761.html