PT - JOURNAL ARTICLE AU - Smith, Mark AU - Myers, Erin TI - <strong>Comparison of Dosimetry from Direct Ion Storage (DIS) and Optically Stimulated Luminescence (OSL) Dosimeters</strong> DP - 2023 Jun 01 TA - Journal of Nuclear Medicine PG - P59--P59 VI - 64 IP - supplement 1 4099 - http://jnm.snmjournals.org/content/64/supplement_1/P59.short 4100 - http://jnm.snmjournals.org/content/64/supplement_1/P59.full SO - J Nucl Med2023 Jun 01; 64 AB - P59 Introduction: Measurements from personal dosimeters are important for assessing radiation risk in the nuclear medicine clinic. OSL and TLD dosimeters typically are returned to the vendor for dose readout and result reporting may take several weeks. Dosimeters using Direct Ion Storage (DIS) technology offer the potential for onsite readout at the push of a button through a Bluetooth or other electronic interface. This enables immediate feedback on events or practices that may cause increased radiation dose. It is crucial that dose estimates from dosimeters using different technologies be comparable, particularly if different types are in use at the same institution. The purpose of this study was to compare dose readings of DIS and OSL dosimeters from a single vendor (Mirion Technologies) in a controlled setting using Tc-99m and F-18.Methods: Fixtures were constructed to mount DIS (Instadose+) and OSL (APex; BeO substrate) dosimeters at fixed distances from a radioactive source of Tc-99m or F-18. The dosimeters were arranged on arcs of radius 50 cm or 100 cm, with the radioactivity in a syringe at the center of the arc. Five DIS and five OSL dosimeters were placed in alternating positions along each arc. The dosimeters and activity were placed on the patient bed of a PET/CT scanner. Measurements were performed first at a distance of 100 cm, then the dosimeter fixture was changed and measurements were made with different dosimeters at a distance of 50 cm. For the Tc-99m experiments, the source activity was 106.4 mCi at the start of the 100 cm measurement period that lasted 121 min and 83.7 mCi at the start of the 50 cm measurement period of 137 min. For the F-18 experiments, the source activity was 12.9 mCi at the start of the 100 cm measurement period of 150 min and 5.0 mCi at the start of the 50 cm measurement period of 167 min. The DIS dosimeters were read out after the Tc-99m experiments and were used again for the F-18 experiments on the following day. Each OSL dosimeter was used just once and was returned to the vendor for dose readout. Analytic calculations of expected doses were made. The doses from the DIS and OSL badges were compared with each other and with the analytic predictions.Results: For Tc-99m at 50 cm the doses (mean±sd) were DIS 54.0±3.5 mrem and OSL 34.0±5.1 mrem (p&lt;0.001). The ratio of the means (DIS/OSL) was 1.59. For Tc-99m at 100 cm the doses were DIS 13.7±1.5 mrem and the only OSL dose above the minimum reportable dose threshold of 10 mrem was 15 mrem. The ratio of the mean DIS dose to the OSL dose was 0.91. For F-18 at 50 cm the doses were DIS 22.8±1.0 mrem and OSL 13.6±4.0 mrem (p=0.006). The ratio of the means (DIS/OSL) was 1.67. For F-18 at 100 cm the doses were DIS 14.3±1.3 mrem and OSL 15.5±0.7 mrem (p=NS). The ratio of the means (DIS/OSL) was 0.92. The higher DIS/OSL ratios at 50 cm for both Tc-99m and F-18 may be due to different dosimeter sensitivity to lower energy scattered photons from the PET scanner bed or backscatter from the scanner. With respect to the analytic dose predictions, the observed DIS values at 50 cm averaged 1.40 (Tc-99m) and 1.21 (F-18) times the predicted values and at 100 cm averaged 1.25 (Tc-99m) and 1.25 (F-18) times the predicted values. The observed OSL values at 50 cm averaged 0.88 (Tc-99m) and 0.72 (F-18) times the predicted values and at 100 cm averaged 1.37 (Tc-99m) and 1.36 (F-18) times the predicted values. Analysis was complicated by the fact that some measured doses were below the minimum reportable dose threshold of 10 mrem and by reading issues with some of the DIS dosimeters.Conclusions: Agreement between DIS and OSL dosimetry for Tc-99m and F-18 was better at 100 cm (average DIS/OSL dose ratio 0.92) than at 50 cm (average DIS/OSL dose ratio 1.63). The greater discrepancy at 50 cm may be due to a sensitivity difference for low energy scattered photons and further investigation is planned. Institutions should compare dosimeter performance if different dosimeter types are used in the same setting.