IADR Abstract Archives
Dosimetry and image quality of low-dose NewTom VGi CBCT protocol
Objectives: Continuing concern with x-ray risk has prompted development of dose-reducing options for CBCT imaging. A new low-dose protocol (ECO) is evaluated for the NewTom VGi.
Methods: Effective doses resulting from various combinations of field size, Standard and ECO exposure protocols, and child or adult anthropomorphic phantoms (CIRS Inc., Norfolk, VA) using the NewTom VGi CBCT unit (QR, s.l.r. Verona, IT) were measured with Optical Stimulated Dosimetry (Nanodot, Landauer, Inc., Glenwood, IL) using previously validated protocols (Ludlow et al. Dentomaxillofac Radiol. 2014;44:20140197). An image quality phantom (DVT_QUART, Zorneding, Germany) was used to measure Contrast to Noise Ratio (CNR) and 10% modulation transfer function (MTF). Figure of Merit (FOM) was calculated as CNR2 ÷ effective dose for a quantitative measure of image quality and dose efficiency for Standard and Low Dose protocol options. Data were analyzed with a matched pair analysis.
Results: Table 1. NewTom VGi effective doses by phantom type, protocol and field of view
Child effective doses averaged 85% greater than adult doses for both standard and ECO protocols.
Paired comparisons of CNR (p=0.46) and MTF (p=0.20) showed no statistically significant difference between protocols while FOM was marginally significant (p=0.0538).
Conclusions: Use of the Low-Dose protocol resulted in an average 34% exposure reduction when compared to Standard exposures. Significant dose reductions may be achieved without a proportionate loss of image quality. Reductions in image quality may be acceptable for certain diagnostic tasks. Further research to determine quality thresholds for specific diagnostic tasks is needed.
Methods: Effective doses resulting from various combinations of field size, Standard and ECO exposure protocols, and child or adult anthropomorphic phantoms (CIRS Inc., Norfolk, VA) using the NewTom VGi CBCT unit (QR, s.l.r. Verona, IT) were measured with Optical Stimulated Dosimetry (Nanodot, Landauer, Inc., Glenwood, IL) using previously validated protocols (Ludlow et al. Dentomaxillofac Radiol. 2014;44:20140197). An image quality phantom (DVT_QUART, Zorneding, Germany) was used to measure Contrast to Noise Ratio (CNR) and 10% modulation transfer function (MTF). Figure of Merit (FOM) was calculated as CNR2 ÷ effective dose for a quantitative measure of image quality and dose efficiency for Standard and Low Dose protocol options. Data were analyzed with a matched pair analysis.
Results: Table 1. NewTom VGi effective doses by phantom type, protocol and field of view
Child effective doses averaged 85% greater than adult doses for both standard and ECO protocols.
Paired comparisons of CNR (p=0.46) and MTF (p=0.20) showed no statistically significant difference between protocols while FOM was marginally significant (p=0.0538).
Conclusions: Use of the Low-Dose protocol resulted in an average 34% exposure reduction when compared to Standard exposures. Significant dose reductions may be achieved without a proportionate loss of image quality. Reductions in image quality may be acceptable for certain diagnostic tasks. Further research to determine quality thresholds for specific diagnostic tasks is needed.