Diksha Gandhi, Presenter: Research funded, General Electric Company

Dominic Crotty PhD, Abstract Co-Author: Employee, General Electric Company

Grant M. Stevens PhD, Abstract Co-Author: Employee, General Electric Company

Taly Gilat Schmidt PhD, Abstract Co-Author: Research funded, General Electric Company

The purpose of this study was to quantify dose and noise performance of organ-dose-based tube current modulation (ODM) through experimental studies with an anthropomorphic phantom and simulations with a phantom library. 

ODM reduces tube current for anterior source positions, without increasing current for posterior positions. Axial CT scans at 120 kV were performed on head and chest phantoms (Rando Alderson Research Laboratories, Stanford, CA) on an ODM-equipped scanner (Optima CT660, GE Healthcare, Chalfont St Giles, England). Dosimeters quantified dose to breast, lung, heart, spine, eye lens and brain regions (mobile MOSFET Dosimetry System, Best Medical, Ottawa, Canada) for ODM, automA (z modulation), and smartmA (angular and z modulation) settings. Noise standard deviation was calculated in brain and chest regions of reconstructed images. To study a variety of patient sizes, Monte Carlo simulations, validated with experimental data, were performed on 28 voxelized head phantoms and 10 chest phantoms. Organ dose and reconstructed noise standard deviation were compared for all phantoms. Image quality assessment is currently underway using a task-dependent signal detectability metric. 

ODM reduced dose at all dosimeters with respect to smartmA, with dose changes of -31.3% (breast), -20.7% (lung), -24.4% (heart), -5.9% (spine), -18.7% (eye), and -10.5% (brain). Simulations indicated average dose changes of -33.4% (breast), -20.2% (lung), -18.6% (spine), -20.0% (eye) and -7.2% (brain). ODM reduced dose to the brain and lung tissue, however these tissues would experience up to 15.2% and 13.1% dose increase respectively at noise standard deviation equal to smartmA. ODM reduced dose to the eye lens in 22 of 28 phantoms (-1.2% to -12.4%), had no change in dose for two phantoms, and increased dose for three phantoms (0.7% to 2.3% ) with respect to smartmA at equal noise standard deviation. All phantoms demonstrated breast dose reduction (-2.1% to -27.6%) at equal noise standard deviation.

Experimental and simulation studies over a range of patient sizes indicate that ODM has the potential to reduce dose to sensitive organs by 5 - 38% with a limited increase in image noise. 

Organ-based tube current modulation has the potential to reduce the dose to radiosensitive tissues with limited degradation in noise standard deviation. 

Gandhi, D, Crotty, D, Stevens, G, Schmidt, T, Radiation Dose and Image Quality Performance of Organ-based Tube Current Modulation for Head and Chest CT Scans.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014331.html