Purpose: To determine the precision and accuracy of CTDI100 measurements made using commercially available optically stimulated luminescent (OSL) dosimeters (Landaur, Inc.) as beam width, tube potential, and attenuating material were varied. Methods: One hundred forty OSL dosimeters were individually exposed to a single axial CT scan, either in air, a 16-cm (head), or 32-cm (body) CTDI phantom at both center and peripheral positions. Scans were performed using nominal total beam widths of 3.6, 6, 19.2, and 28.8 mm at 120 kV and 28.8 mm at 80 kV. Five measurements were made for each of 28 parameter combinations. Measurements were made under the same conditions using a 100-mm long CTDI ion chamber. Exposed OSL dosimeters were returned to the manufacturer, who reported dose to air (in mGy) as a function of distance along the probe, integrated dose, and CTDI100. Results: The mean precision averaged over 28 datasets containing five measurements each was 1.4 ± 0.6, range 0.6-2.7 for OSL and 0.08 ± 0.06, range 0.02-0.3 for ion chamber. The root mean square (RMS) percent differences between OSL and ion chamber CTDI 100 values were 13.8, 6.4, and 8.7 for in-Air, head, and body measurements, respectively, with an overall RMS percent difference of 10.1. OSL underestimated CTDI100 relative to the ion chamber 2128 times (75). After manual correction of the 80 kV measurements, the RMS percent differences between OSL and ion chamber measurements were 9.9 and 10.0 for 80 and 120 kV, respectively. Conclusions: Measurements of CTDI100 with commercially available CT OSL dosimeters had a percent standard deviation of 1.4. After energy-dependent correction factors were applied, the RMS percent difference in the measured CTDI100 values was about 10, with a tendency of OSL to underestimate CTDI relative to the ion chamber. Unlike ion chamber methods, however, OSL dosimeters allow measurement of the radiation dose profile.
- CT dose index
- computed tomography (CT)
- optically stimulated luminescence
- radiation dose profile
- radiation dosimetry
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging