8th Baltic Congress of Radiology

Nuclear Medicine

oral abstract

In daily practice, nuclear medicine personnel is responsible for positioning and supervising patients during image acquisition, preparation and administration of radiopharmaceuticals, which leads to higher doses of the whole body Hp(10) and extremity Hp(0.07). For the monitoring of Hp(10) passive dosimeters are used. However, for the more detail assessment for the radiation exposure dose received during different processes active personal dosimeters (APD) should be used. For the monitoring of extremity Hp(0.07) doses in our hospital is performed by wearing a passive ring dosimeter on the base of the middle finger of the dominant hand. However, the dose distribution over the hand is inhomogeneous and the Hp(0.07) doses obtained by the ring dosimeter can be significantly lower compared to other hand parts, especially fingertips, as the tips of the hand are the closest to radioisotope during preparation and injection of radiopharmaceuticals. The aim of this study was to evaluate and assess whole body with APD and hand doses in different points for radiology technologists of the Nuclear Medicine Department of Vilnius University Hospital Santaros Klinikos (VUHSK) working with 99mTc-labelled radiopharmaceuticals and with an automatic IRIDE (Comecer, Italy) 18F-FDG injection system.

For Hp(10) nuclear medicine personnel radiation exposure data was measured with APD POLIMASTER PM1610B-01 (Geiger-Muller tube detector) and Thermo Scintific EPD TruDose (PIN Silicon Diode detector). APDs were calibrated and verified once per year by the Vilnius Metrology Centre or with onsite intercomparison measurements. Together with APD worn at the waist level, the personnel constantly wear passive dosimeters in order to measure personal dose equivalent Hp(10) (chest area) and Hp(0.07) (finger) for individual monitoring. Passive dosimeters are read every three months by accredited laboratory. For detail Hp(0.07) assessment, calibrated thermoluminescent dosimeters (TLD-100 (LiF:Mg, Ti)) chips were used for the measurements of hand doses and were read by RIALTO TLD (Ne Technology) reader. In order to prevent TLDs from contamination and to ensure disinfection, all dosimeters were put in plastic envelopes and further on attached to both hands on the palm side at 15 locations (on fingertips, palm and wrist of each hand and at a typical monitoring position (base of the middle finger of the dominant hand)) under the disposable gloves. For Hp(10) daily work tasks of nuclear medicine personnel directly involved with radiation sources were distinguished for administration radiopharmaceuticals, quality control and assurance and performing of scan. For Hp(0.07) working process was split into three steps: to measure workflow in a hot lab, to administer 99mTc- labelled radiopharmaceuticals to patients, and to administer 18F-FDG in injection room with the automatic injection system IRIDE. Each NM worker working with 99mTc and 18F wore dosimeters from 5 to 6 working days. The measured doses were normalized per manipulated activity (mSv/GBq).

The mean doses to the radiology technologist (RT) per patient working with PET/CT for administration of radiopharmaceuticals were 1.72±0.33 µSv and 1.16±0.11 µSv (depending on the injection system), for the RT per patient for scanning was 0.52±0.07 µSv. Working in the hot laboratory with 99mTc the mean dose per one working day was 3.1±1.29 µSv, for SPECT procedures 4.57±2.5 µSv, respectively. During work in a hot laboratory with 99mTc, the most exposed parts were the tips of the thumb, index finger and middle finger of the right (dominant) hand and resulted in the average doses of 0.73±0.22, 0.52±0.21, 0.76±0.21 mSv/GBq, respectively. During injection of 99mTc- labelled radiopharmaceuticals, the most exposed parts were the tips of the index finger of the left (non-dominant) hand and the thumb and middle finger of the right (dominant) hand, with the average doses being 93.8±17.3, 88.3±20.4 and 81.7±31.1 µSv/GBq, respectively. In both cases, the lowest doses were registered by the TLD-100 chips placed on the wrists. During 18F-FDG administration to patients using IRIDE system, the most exposed parts were the right hand thumb tip, index finger and middle finger, and resulted in average doses of 39.0±15.0; 38.7±15.2; 38.4±12.3 µSv/GBq, respectively. Also, the maximum fingertip doses were 1.3-2.4 times higher compared with the doses from typical monitoring position (base of the middle finger of the dominant hand).

Continuous monitoring with APD allowed for a quick response when the daily measured dose suddenly increased, in which case the circumstances were clarified and additional instructions were provided. Proper design of the nuclear medicine division, continuous monitoring of staff doses with APDs supplied with alarm, assessment of unexpected daily doses are all effective measures for exposure control. Personnel qualifications, training and gained experience as well as a right work distribution between personnel and radiation safety culture are also important for dose optimization and a smooth work process. It was found that the most exposed parts of the hand during work with 18F and 99mTc radioisotopes are fingertips of the thumb, index finger and middle finger. What is more, the maximum fingertip doses were 1.3-2.4 times higher compared with the doses from typical monitoring position in Lithuania (base of the middle finger of the dominant hand). Also, there was a tendency that the highest doses were observed for the dominant hand during preparation of 99mTc- labelled radiopharmaceuticals in a hot laboratory and the lowest doses – during the work with an automatic IRIDE 18F-FDG injection system. Lower doses found for hands during administration of 18F-FDG shows the advantages of automated injection/infusion systems, thus implementation of automatic infusion/injection in hospitals could be an expedient way to optimize Hp(10) and Hp(0.07) doses to nuclear medicine workers. For future monitoring perspectives, more accurate passive and active dosimeters should be used in daily clinical work.

Nuclear medicine personnel is responsible for positioning patients during image acquisition, preparation and administration of radiopharmaceuticals, which leads to higher doses of the whole body Hp(10) and extremity Hp(0.07). The aim of this study was to evaluate and assess exposure doses with active personal dosimeters and TLD dosimeters for different processes and activities in nuclear medicine division. The doses to the radiology technologists per patients nad µSv/GBq were evaluated.

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