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(-1) (14 × 10 cm, 60 kVp) and 0.108 mGy mAs(-1) (14 × 10 cm, 90 kVp). The relation between kVp and dose was quasilinear (R(2) > 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.
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(-1) (14 × 10 cm, 60 kVp) and 0.108 mGy mAs(-1) (14 × 10 cm, 90 kVp). The relation between kVp and dose was quasilinear (R(2) > 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.
Authors: R Pauwels; C Theodorakou; A Walker; H Bosmans; R Jacobs; K Horner; R Bogaerts Journal: Dentomaxillofac Radiol Date: 2012-06-29 Impact factor: 2.419
Authors: R Pauwels; O Nackaerts; N Bellaiche; H Stamatakis; K Tsiklakis; A Walker; H Bosmans; R Bogaerts; R Jacobs; K Horner Journal: Br J Radiol Date: 2013-01 Impact factor: 3.039