Abstract:
Objective: The point dose and volume CT dosimetry index (CTDI
vol) at different X-ray energies were measured using the Raysafe-X2 air ionization chamber (referred to as “RX2”), the Piranha CT dose profiler semiconductor ionization chamber (referred to as “CDP”), and the
30013 Farmer air ionization chamber (referred to as “PT3”), in order to explore the effect of X-ray energy on the radiation dose evaluation by different dose meters. Methods : The tube voltage settings for each layer were as follows: single energy mode included 80 kV, 90 kV, 100 kV, 120 kV, 140 kV, and 150 kV (Sn); dual energy mode included 70/150 kV (Sn), 80/150 kV (Sn), 90/150 kV (Sn), 100/150 kV (Sn), and 80/140 kV. The tube current was manually adjusted to ensure that the CTDI
vol for each group was approximately 20 mGy, and the displayed CTDI
vol and DLP were recorded. Point dose values were measured at the center, 0-point, 3-point, 6-point, and 9-point positions of the 32 cm phantom using CDP and PT3. The actual CTDI
vol was measured and calculated using RX2, CDP, and PT3. Results: (1) Point Dose:①in single energy mode (except for Sn150 kV), CDP measured higher point doses at the center compared to PT3. At low energies, the point dose measured by CDP at non-center positions was 75% higher than that of PT3, while at high energies, 88% of the point doses measured by PT3 were higher than those measured by CDP. ②In dual energy mode (except for 90+Sn150 kV), CDP measured higher point doses at the center compared to PT3. However, except for 80+140 kV, PT3 measured higher point doses than CDP at non-center positions. (2) As for CTDI
vol, the measured values were as follows: RX2 measured (18.89 ± 0.38) mGy, CDP measured 18.31 (19.25, 20.84) mGy, and PT3 measured (20.35 ± 0.38) mGy. Except when CDP was used at 150 kV (Sn), the CTDI
vol measured by all three dose meters for other X-ray energies ranged between 16 mGy and 24 mGy. Conclusion: Different dosimeters exhibit varying responses to X-ray energy. Therefore, selecting an appropriate dosimeter is crucial depending on the measurement conditions and objectives.