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A pragmatic approach to determine the optimal kVp in cone beam CT: balancing contrast-to-noise ratio and radiation dose.
- Source :
- Dentomaxillofacial Radiology; 2014, Vol. 43 Issue 5, p1-12, 12p
- Publication Year :
- 2014
-
Abstract
- Objectives: To determine the optimal kVp setting for a particular cone beam CT (CBCT) device by maximizing technical image quality at a fixed radiation dose. Methods: The 3D Accuitomo 170 (J. Morita Mfg. Corp., Kyoto, Japan) CBCT was used. The radiation dose as a function of kVp was measured in a cylindrical polymethyl methacrylate (PMMA) phantom using a small-volume ion chamber. Contrast-to-noise ratio (CNR) was measured using a PMMA phantom containing four materials (air, aluminium, polytetrafluoroethylene and low-density polyethylene), which was scanned using 180 combinations of kVp/mA, ranging from 60/1 to 90/8. The CNR was measured for each material using PMMA as background material. The pure effect of kVp and mAs on the CNR values was analysed. Using a polynomial fit for CNR as a function of mA for each kVp value, the optimal kVp was determined at five dose levels. Results: Absorbed doses ranged between 0.034 mGy mAs<superscript>-1</superscript> (14 x 10 cm, 60kVp) and 0.108 mGy mAs<superscript>-1</superscript> (14 x 10 cm, 90 kVp). The relation between kVp and dose was quasilinear (R² >0 .99). The effect of mA and kVp on CNR could be modelled using a second-degree polynomial. At a fixed dose, there was a tendency for higher CNR values at increasing kVp values, especially at low dose levels. A dose reduction through mA was more efficient than an equivalent reduction through kVp in terms of image quality deterioration. Conclusions: For the investigated CBCT model, the most optimal contrast at a fixed dose was found at the highest available kVp setting. There is great potential for dose reduction through mA with a minimal loss in image quality. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 0250832X
- Volume :
- 43
- Issue :
- 5
- Database :
- Complementary Index
- Journal :
- Dentomaxillofacial Radiology
- Publication Type :
- Academic Journal
- Accession number :
- 97203986
- Full Text :
- https://doi.org/10.1259/dmfr.20140059