Characterization of the nanoDot OSLD dosimeter in CT

Abstract

Correction factors for the measurement of air kerma were generally small for CT dosimetry, although angular effects, and particularly effects due to changes in beam quality, could be more substantial. In particular, it would likely be necessary to account for variations in CT scan parameters and measurement location when performing CT dosimetry using OSLD.

Characterization of nanoDot optically stimulated luminescence detectors and high‐sensitivity MCP‐N thermoluminescent detectors in the 40–300 kVp energy range

“…The cumulative dose of 450 cGy also exceeds the 82 mGy investigated by Al‐Senan . This is broadly consistent with similar studies in the megavoltage range, which suggests that response supralinearity only becomes a concern at very high (20–60 Gy) cumulative doses …”

“…and , the OSLDs exhibited no noticeable change in response through a total of 44 optical bleaching cycles and a cumulative dose of 450 cGy. Although some investigators have assessed optical bleaching over relatively few exposure cycles, we show that the OSLD measured corrected counts are reproducible within ≤1.5% over a very large number of exposure cycles, with no systematical increase in response with cumulative dose. This is a noteworthy result, because a rise of 2.5% over only 8 cycles of 100 cGy each (800 cGy total) had been previously reported by Mrčela et al …”

“…However, we know from Scarboro et al. that the nanoDot OSLD energy response for a single beam quality may vary by up to 25% for a single diagnostic CT beam quality, based on the exact position of the OSLD inside the phantom . This implies that OSLDs used in kilovoltage x‐ray applications are extremely sensitive not only to the exact beam quality but also to other geometric factors affecting the spectrum at the effective point of measurement.…”

“…Solid‐state detectors, such as thermoluminescent detectors (TLDs) and optically stimulated luminescent detectors (OSLDs), are commonly used to measure radiation doses in a wide variety of situations. These include in vivo patient dose estimates in radiation therapy, diagnostic mammography, and computed tomography (CT) imaging . OSLDs are increasingly favored over TLDs because they offer significant advantages in cost‐effectiveness and relative ease of use …”

Physical validation of a Monte Carlo‐based, phantom‐derived approach to computed tomography organ dosimetry under tube current modulation

“…It is believed that the number of dosimeters used per organ based on its axial and z‐extent justifies using averaged point doses to estimate the true organ dose. It should also be noted that previous work has shown minimal angular dependence for these particular OSL dosimeters when used for in‐phantom CT dosimetry, especially at deeper depths in tissue …”