Energy dependence and angular dependence of an optically stimulated luminescence dosimeter in the mammography energy range

Abstract

This study aimed to investigate the energy dependence and the angular dependence of commercially available optically stimulated luminescence (OSL) point dosimeters in the mammography energy range. The energy dependence was evaluated to calculate calibration factors (CFs). The half‐value layer range was 0.31–0.60 mmAl (Mo/Mo 22–28 kV, Mo/Rh 28–32 kV, and W/Rh 30–34 kV at 2‐kV intervals). Mo/Rh 28 kV was the reference condition. Angular dependence was tested by rotating the X‐ray tube from −90° to 90° in 30° increments, and signal counts from angled nanoDots were normalized to the 0° signal counts. Angular dependence was compared with three tube voltage and target/filter combinations (Mo/Mo 26 kV, Mo/Rh 28 kV and W/Rh 32 kV). The CFs of energy dependence were 0.94–1.06. In Mo/Mo 26–28 kV and Mo/Rh 28–32 kV, the range of CF was 0.99–1.01, which was very similar. For angular dependence, the most deteriorated normalized values (Mo/Mo, 0.37; Mo/Rh, 0.43; and W/Rh, 0.58) were observed when the X‐ray tube was rotated at a 90° angle, compared to 0°. The most angular dependences of ± 30°, 60°, and 90° decreased by approximately 4%, 14%, and 63% respectively. The mean deteriorated measurement 30° intervals from 0° to ± 30° was 2%, from ± 30° to ± 60° was 8%, and from ± 60° to ± 90° was 40%. The range of energy dependence in typical mammography energy range was not as much as that in general radiography and computed tomography. For accurate measurement using nanoDot, the tilt needs to be under 30°.

Assessment of scatter radiation dose and absorbed doses in eye lens and thyroid gland during digital breast tomosynthesis

“…We show that the nanoDot response to scatter radiation had a maximum variation of 33% compared to the ionization chamber. This may be explained by the energy dependence of the nanoDot in the energy range utilized during mammography; this value has been reported as 10% in the study by Kawaguchi et al, 12 whereas it was 50% in the study by Okazaki et al 14 acquisition; these are almost ten times higher than those measured in our study (29.7 μGy in CM and 47.7 μGy in TM). Procedural variations can account for this difference as the other studies used a female voxel phantom, a computational phantom based on segmented images of a 43-year-old patient, and assumed an AGD of 2 mGy for a W/Rh 28 kV x-ray spectrum for the imaged breast.…”

“…McKeever et al 10 have reported that OSLDs are capable of measuring doses as low as 10 μGy, linear response among commercially available OSLDs starts at approximately 50 μGy. In addition, previous studies 11,12 have demonstrated the feasibility of using commercial OSLDs in the mammography energy range by adding a correction factor.…”

The measurement of entrance surface dose using optically stimulated luminescence dosimeters for determining average glandular dose in digital breast tomosynthesis: Measurement and simulation study

“…9 An accumulated dose measurement with multiple exposures using OSLD could be applied at a low dose level, such as entrance surface dose (ESD) for mammography, 10 with a reliability response of ±0.6% compared to a single exposure. The study by Kawaguchi et al 12 showed that the energy dependence of the OSLD; Al 2 O 3 :C (nanoDot) was less than 5.0% for the mammography energy range of 24-35 kV, which was consistent with Alothmany et al 11 who also reported the energy dependence was less than 5.0% in the 25-32 kV range. However, Kawaguchi et al 12 reported that the angular dependence of the nanoDots was lower than 4.0% for the X-ray tube rotated in the range of ±30 • , whereas those of 10.0% for Alothmany et al Rocha et al 13 used the nanoDots and PTW QC dosimeter to measure the radiation dose for FFDM with 27 kV Mo/Mo target/filter combination.…”

“…The study by Kawaguchi et al 12 showed that the energy dependence of the OSLD; Al 2 O 3 :C (nanoDot) was less than 5.0% for the mammography energy range of 24-35 kV, which was consistent with Alothmany et al 11 who also reported the energy dependence was less than 5.0% in the 25-32 kV range. However, Kawaguchi et al 12 reported that the angular dependence of the nanoDots was lower than 4.0% for the X-ray tube rotated in the range of ±30 • , whereas those of 10.0% for Alothmany et al Rocha et al 13 used the nanoDots and PTW QC dosimeter to measure the radiation dose for FFDM with 27 kV Mo/Mo target/filter combination. They found discrepancies between the nanoDots and PTW QC dosimeter of 0.5% and 0.6% in ESD and AGD, respectively.…”

Anisotropy of the Absorption of the Photon Ionizing Radiation by YAlO3: Mn Dosimetric Detector

“…Their sensitive element usually has got the form of the plate, so, if the radiation has got the predominant direction of propagation, the energy absorbed by the detector depends on the spatial orientation of the detector plate relative to radiation flow direction. This peculiarity causes the additional dose measurement error known as an angular or directional dependence of dose value [3][4][5] which, in general, depends on the irradiation source properties (shape, dimensions, energy etc.) as well as detector (shape, dimensions and attenuation coefficient of the material).…”