Room: Exhibit Hall | Forum 6
Purpose: To measure and compare radiation dose delivered to phantoms and contrast to noise (CNR) measured in low contrast phantoms using pediatric clinical body CT protocols for MECT(Spectral) and MDCT.
Methods: Various diameter acrylic ACR phantoms (16-32 cm) were scanned on 128-detector MECT(Spectral) and MDCT 256-detector MDCT (IQon Spectral and Brilliance iCT, Philips, Cleveland, OH) using standard clinical body CT protocols (energy range 80-120kVp) MECT and CTDIvol matched clinical body CT protocols (energy 120kVp). Ion chambers (Radcal Corporation, Monrovia, CA) positioned centrally and in superficial burr holes and nanoDot dosimeters (Landauer, Glenwood, IL) were positioned on the surface at the 12,3,6, and 9oâ€™clock position. Three successive scans were performed; measured results were averaged per protocol and phantom size. AAPM low contrast phantoms were scanned using identical clinical brain protocols; contrast-to-noise (CNR) ratios were calculated. Analysis of results included calculation of percent difference between radiation dose and CNR measurements for the IQon verses iCT scanners.
Results: Clinical pediatric brain CT protocols for MDCT and comparable MECT(Spectral) with identical CTDIvol enabled calculation of contrast to noise and signal to noise ratios (Table 1). For all phantom sizes and energy levels the percent difference in dose measured using surface nanoDots and central&peripheral ion-chambers shows between 0.89% greater-11.53% average less dose for MDCT, therefore slightly greater measured dose for MECT. CNR calculations show equal or improved image quality using MECT(Spectral) compared to MDCT.
Conclusion: Dose and image quality equity is possible with MECT(Spectral) and comparable MECT. The slight difference in measured dose for surface and central nanoDots and for central and peripheral ion chambers is well within the standard 20% expected interscan variation and is statistically insignificant. The dose measured using surface nanoDots was greater using MECT, likely due to universal use of 120 kVp energy for all phantom sizes.
Funding Support, Disclosures, and Conflict of Interest: Master Enterprise Agreement - Klininklijke Philips, NV