1 Development of an FDA CT Organ Dose Handbook Thalia T. Mills, Ph. D. FDA Commissioner’s Fellowship project with Dr. Stanley Stern MITA CT Stakeholders Meeting 11/29/2010 (at RSNA 2010)

2 CT handbook: end products 1. Excel spreadsheet where organ doses are computed based on the following input: Age (0, 1, 5, 10, 15, Adult) Anatomical range on phantom Normalization factor (CTDI-based) 2. Table of physical extent (in z-direction) for all organs in each phantom (from the ORNL series) 3. For common exams, tabulations of organ doses based on typical protocol parameters Part of the FDA organ dose handbook program 1 ImPACT dosimetry calculator (2006)

3 Three major challenges in handbook development 1.Scanner-independent doses 2.Pediatric doses (limited data) 3.Common exams ↔ Parameters relevant to dose

4 Normalization FactorNRPB Mean CoV (%) Turner et al. 3 Mean CoV (%) None3132 CTDI norm = 0.85 CTDI 100,c CTDI 100,p CTDI w = 1/3 CTDI 100,c + 2/3 CTDI 100,p Feasibility of scanner-independent organ doses

5 Organ doses for ORNL series of pediatric phantoms 4 Normalized lung dose for scanning the pediatric trunk. For the 0-10 year old phantoms, data are normalized to CTDI 100 values corresponding to both the 16-cm and 32-cm diameter phantoms. For the 32-cm dosimetry phantom, CTDI norm = 0.85 CTDI 100,c CTDI 100,p. For the 16-cm phantom, the normalization value used was CTDI w. GE 9800; 16 cm Siemens DRH; 16 cm Philips LX; 16 cm GE 9800; 32 cm Siemens DRH; 32 cm Philips LX; 32 cm Conclusion: Using a normalization factor based on the 32-cm phantom results in unacceptable variation for the smaller phantoms.

6 Parameterizing common clinical protocols Sources of data 1. Literature compilations: Kalra, M. K., Saini, S., and Rubin, G. D., eds. (2006). MDCT: From protocols to practice. New York: Springer. Silverman, P. M., ed. (2002). Multislice computed tomography: a practical approach to clinical protocols. Philadelphia: Lippincott Williams and Wilkins. 2. Protocols from individual facilities: M.D. Anderson Cancer Center (thanks to Dr. Dianna Cody) Duke demographical data on pediatric protocols (thanks to Dr. Donald Frush) Rhode Island Hospital 5 Johns Hopkins University 6 3. FDA/CRCPD Nationwide Evaluation of X-ray Trends data for ~15 most common CT exams ( survey) 4. AAPM Working Group on Standardization of CT Nomenclature and Protocols

7 Notes 1 Rays/ucm htm Rays/ucm htm 2 The NRPB-250 data are for a trunk exam on the adult ORNL phantom averaged over 25 organs for 17 single-slice scanner data sets. [Reference: Jones, D. G., and Shrimpton, P. C. (1993). Normalised organ doses for x-ray computed tomography calculated using Monte Carlo techniques. Document NRPB-SR250. Chilton, UK: National Radiological Protection Board.] 3 The Turner et al. data are for a full-body exam on the adult female “Irene” phantom averaged over 25 organs for 4 modern multi-slice scanners. [Reference: Turner, A. C. et al. (2010). The feasibility of a scanner-independent technique to estimate organ dose from MDCT scans: using CTDIvol to account for differences between scanners. Medical Physics, 37, )] 4 Organ doses for pediatric patients (neonate, 1 year, 5 years, 10 years, 15 years) for 3 different scanners were provided by Jan Jansen and Paul Shrimpton from U.K.’s Health Protection Agency. These data were previously published in part in: Shrimpton, P. C. (2004). Assessment of patient dose in CT, NRPB-PE/1/2004. Chilton, U. K.:National Radiological Protection Board. Retrieved from The phantoms are documented in: Christy, M., and Eckerman, K. F. (1987). Specific Absorbed Fractions of Energy at Various Ages from Internal Photon Sources. ORNL/TM Oak Ridge National Laboratory