###### Abstract  
The International Commission on Radiological Protection has lowered the annual equivalent eye-lens dose to 20 mSv. Although occupational exposure can be high in nuclear medicine (NM) departments, few studies have been conducted regarding eye-lens exposure among NM staff. This study aimed to estimate the annual lens doses of staff in an NM department and identify factors contributing to lens exposure. Four nurses and six radiographers performing positron emission tomography (PET) examinations and four radiographers performing radioisotope (RI) examinations (excluding PET) were recruited for this study. A lens dosimeter was attached near the left eye to measure the 3-mm-dose equivalent; a personal dosimeter was attached to the left side of the neck to measure the 1-cm- and 70-um-dose equivalents. Measurements were acquired over six months, and the cumulative lens dose was doubled to derive the annual dose. Correlations between the lens and personal-dosimeter doses, between the lens dose and the numbers of procedures, and between the lens dose and the amounts of PET drugs (radiopharmaceutical) injected were examined. [PERSON]'s signed-rank test was used to compare lens and personal-dosimeter doses. The estimated annual doses were 0.93 \(\pm\) 0.13 mSv for PET nurses, 0.71 \(\pm\) 0.41 mSv for PET radiographers, and 1.10 \(\pm\) 0.53 mSv for RI radiographers. For PET nurses, but not for PET or RI radiographers, there was a positive correlation between the numbers of procedures and lens doses and between amounts injected and lens doses. There was a significant difference between the lens and personal-dosimeter doses of PET nurses. The use of protective measures, such as shielding, should prevent NM staff from receiving lens doses > 20 mSv/year. However, depending on the height of the protective shield, PET nurses may be unable to assess the lens dose accurately using personal dosimeters. radiation protection and safety; nuclear medicine; positron emission tomography (PET); radioisotope (RI) examination; single-photon emission computed tomography (SPECT); eye-lens dose; nurse; occupational radiation exposure; radiographer; disaster medicine +
Footnote †: journal: Medical  
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workers [1; 2]. The International Commission on Radiological Protection (ICRP) issued a statement regarding tissue reactions in 2011, which led to a review of lens-dose limits in many countries. The ICRP established a mean annual lens-dose occupational exposure limit of 20 mSv over a five-year period, and the dose also should not exceed 50 mSv in any single year; the previous limit was 150 mSv/year [3]. Many studies have been conducted regarding lens exposure in medical personnel [4; 5; 6; 7; 8; 9; 10; 11; 12]. For instance, one study found that some physicians exceeded the annual lens dose of 20 mSv [13], while another demonstrated how protective equipment, such as eyewear, could effectively reduce lens exposure [14]. In International Atomic Energy Agency Tecdoc Series No. 1731 [14], a risk of significant lens exposure is acknowledged for staff involved in fluoroscopic interventional radiology (IVR), nuclear medicine (NM; particularly when using beta radiation sources), brachytherapy, computed tomography-guided puncture procedures, and cyclotrons. The likelihood that the lens-dose limit will be exceeded is particularly high for fluoroscopic IVR [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]. Lens exposure has also been reported in fluoroscopies, such as endoscopic retrograde cholangiocarcinoma-creatography (ERCP) and respiratory endoscopy, as well as in CT-guided puncture procedures and brachytherapy [11; 26; 27]. However, few studies have evaluated lens exposure during NM examinations, although such examinations carry a high risk of occupational exposure. Moreover, among radiology technologists (RTs) who have performed at least one NM examination, there is an increased risk of cataracts [28].