Development of an FDA CT Organ Dose Handbook

1. Development of an FDA CT Organ Dose Handbook Thalia T. Mills, Ph. D. thalia.mills@fda.hhs.gov 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 ImPACT dosimetry calculator (2006) Part of the FDA organ dose handbook program1

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

4. Feasibility of scanner-independent organ doses

5. GE 9800; 16 cm Siemens DRH; 16 cm Philips LX; 16 cm GE 9800; 32 cm Siemens DRH; 32 cm Philips LX; 32 cm Organ doses for ORNL series of pediatric phantoms4 Normalized lung dose for scanning the pediatric trunk. For the 0-10 year old phantoms, data are normalized to CTDI100values corresponding to both the 16-cm and 32-cm diameter phantoms. For the 32-cm dosimetry phantom, CTDInorm= 0.85 CTDI100,c+ 0.15 CTDI100,p. For the 16-cm phantom, the normalization value used was CTDIw. 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 Hospital5 • Johns Hopkins University6 3. FDA/CRCPD Nationwide Evaluation of X-ray Trends data for ~15 most common CT exams (2005-2006 survey) 4. AAPM Working Group on Standardization of CT Nomenclature and Protocols

7. Notes 1http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm117898.htm 2The 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.] 3The 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, 1816-1825.)] 4Organ 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 http://www.msct.eu/PDF_FILES/EC%20CA%20Report%20D5%20-%20Dosimetry.pdf. 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-8381. Oak Ridge National Laboratory. 5http://www.rhodeislandhospital.org/rih/services/diagimag/ct/tech/ 6http://ctisus.com/