Jenifer Willmann Siegelman MD, MPH, Presenter: Nothing to Disclose

Holly Lincoln MA, Abstract Co-Author: Nothing to Disclose

Dustin A. Gress MS, Abstract Co-Author: Nothing to Disclose

Choonsik Lee PhD, Abstract Co-Author: Nothing to Disclose

Daniel Valentino PhD, Abstract Co-Author: Vice President, Landauer, Inc Board Member, Medical Vision Systems, LLC Advisory Board, iCRco, Inc

Alphonso Magri PhD, Abstract Co-Author: Nothing to Disclose

Mark Patrick Supanich PhD, Abstract Co-Author: Research Grant, Siemens AG

Definition of quantifiable effect on lens dose in low CTDIvol range,can inform priority setting in the protocol optimization process, and aid risk communication in medical decision making.

Definition of quantifiable effects on organ dose can inform decision in the protocol optimization process.Nearly optimized sinus CT protocols, in a multi-vendor environment, with and without iterative reconstruction, resulted in an average CTDIvol value that was one-fifth of the 50th percentile of ACR Dose Index Registry. This work aims to quantify how Sinus CT protocol optimization efforts impact organ dose to the eye lens, through direct measurement and Monte Carlo simulation, while considering ICRP threshold.

Scan parameters and average CTDIvol from the three scanners in one community health system were compiled using commercial software (Radimetrics Inc,Toronto,ON) (Scanner A: 100 kVp, 50 mAs; Scanner A: 120 kVp, 50 mAs; Scanner B: 120 kVp, 70 mAs; Scanner C: 100 kVp 70 mAs: no gantry tilt, length 13 cm). Lens dose was calculated via Monte Carlo radiation transport coupled with an adult computational human phantom with a realistic eye model including globe, lens, and orbit assessing direct dose as well as scatter. Direct measurement of air kerma was performed for each protocol using dosimeters including commercially available optically stimulated luminescence (OSL) strips (Landauer) calibrated at a mean energy of 65 kVp as well as a 0.6 cc ion chamber (Radcal) calibrated for diagnostic scanning placed on the eyelid of the Rando phantom (Alderson, Stamford, CT).With these diagnostic scans, performed at CTDIvol = 5.3-12.1 mGy, the estimated absorbed dose to the lens of the eye based on phantom simulation ranged from 4.2 - 9.6 mGy. The measured air kerma to the “lens” surrogate 0.6cc ion chamber more closely paralleled the CTDIvol for the scanner with values from 5.2 -12.2 mGy. Strip dosimeters resulted in a measured peak dose of 5.4 to 17.6 mGy.

Diagnostic quality Sinus CT, performed at techniques less than 1/5 of the median CTDIvol reported in the ACR Dose Index Registry result in lens doses which are well below the threshold for tissue damage according to the ICRP.

Siegelman, J, Lincoln, H, Gress, D, Lee, C, Valentino, D, Magri, A, Supanich, M, Comparison of the Organ Dose to the Lens of the Eye to ICRP Threshold Values for Cataract Formation in the Sinus MDCT Protocol Optimization Process.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13027213.html