## 4 Discussion  
It is important to evaluate the dose of radiation that medical workers receive, particularly to their eyes [41; 42; 43; 44; 45; 46; 47; 48; 49; 50]. Many studies have been conducted on medical occupational radiation dose evaluation and protection, including by our research group [51; 52; 53; 54; 55; 56; 57; 58; 59; 60]. However, no study to date has specifically investigated occupational radiation doses to the eyes in physicians performing \({}^{198}\)Au permanent grain brachytherapy. In this study, we measured this to be -0.1 mSv/procedure at most, implying that such physicians' exposure will probably not exceed the regulatory eye dose limit. However, we believe that this dose cannot be ignored because physician exposure may exceed the limit if numerous procedures are performed with inadequate radioprotection. Interventional radiology (IVR) procedures are often associated with increased fluoroscopy time; consequently, they may expose IVR physicians to radiation-induced injuries. The eye dose per procedure for a \({}^{198}\)Au brachytherapy physician was somewhat higher than that for an IVR physician [61; 62]. However, IVR physicians may face a higher risk of radiation exposure because they typically perform a greater number of procedures. Note that in this study, the physician loaded the needles while using an additional lead shielding device. Without it, the eye dose might have exceeded the limit; therefore, we strongly recommend that \({}^{198}\)Au brachytherapy physicians use an additional lead shielding device while loading needles. Thus, educating the brachytherapy staff about radiation  
Figure 16: Relationship between physician’s right-hand dose and total radiation activity at implantation during \({}^{198}\)Au grain brachytherapy. Figure 17: Relationship between physician’s right-hand dose and left-eye dose (DOSIRIS(tm)) during \({}^{198}\)Au grain brachytherapy. protection is important. The procedures in this study were performed by a highly experienced brachytherapy physician and show how the right training of workers is important, as suggested in many ICRP publications [34; 63; 64; 65; 66]. Regarding the IVR staff, particularly physicians, the left eye typically receives a higher radiation dose than the right one [62; 67]. However, we found that the eye radiation dose was similar in both eyes for the physician administering \({}^{198}\)Au grain brachytherapy, with a strong correlation between left- and right-eye doses. Therefore, wearing an eye dosimeter on either side is sufficient for \({}^{198}\)Au grain brachytherapy physicians. Estimation of the occupational radiation dose to the eye often involves using a neck badge [68; 69]. In IVR, a relation between the neck badge dose and the eye dosimeter dose has been reported, and these doses are somewhat correlated [68; 70]. In this study, although there was a trend toward a correlation between the neck and the eye doses (Figures 10 and 11), the association was not statistically significant. Therefore, the neck dose during brachytherapy treatment may be not a good indicator of the physician's eye dose. We also found that the eye dose tended to be underestimated using a neck dosimeter; in many instances, the neck badge failed to detect any radiation during \({}^{198}\)Au grain brachytherapy. The neck dosimeters measured very low levels, probably at the limit of reliable measures. This finding may be due to the fact that the neck badge was further from the source than the eye dosimeter, although we did not measure the distance between the eye and the neck dosimeters. Thus, estimating the eye dose in relation to the neck badge dose may be challenging for \({}^{198}\)Au brachytherapy physicians. Therefore, we recommend that \({}^{198}\)Au brachytherapy physicians wear an eye dosimeter (such as DOSIRIS) on either side of their head for an accurate assessment of the eye radiation dose. We found a correlation between physician's eye dose and total radiation activity (r = 0.65).