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