Abstract
PurposeWe investigated occupational dose to the lens of the eye for CT-assisting personnel for diagnostic purposes using a radio-photoluminescent glass dosimeter (RPLD) and evaluate compliance with the new equivalent dose limit for the lens of the eye (20 mSv/year). Further, we proposed the implementation of “multiple protective measures” and estimated its effect. MethodAn eye lens dosimeter clip was developed specifically to attach RPLDs inside radiation safety glasses in an L-shape. Using a total of six RPLDs attached to the radiation safety glasses, the 3-mm dose-equivalent (Hp(3)) to the lens of the eye for medical staff (n = 11; 6 intensive care physicians, 2 pediatricians, 3 radiological technologists) who assisted patients during CT scan for “diagnostic” purpose (n = 91) was measured. We evaluated the dose reduction efficiencies with radiation safety glasses and bag-valve-mask extension tube. We also estimated the protection efficiency with radiation protection curtain introduced in front of the staff's face via the phantom experiment. ResultsWithout wearing radiation safety glasses, Hp(3) to the lens of the eye was greatest for intensive care physicians (0.49 mSv/procedure; allowing 40 procedures to be performed annually), followed by pediatricians (0.30 mSv/procedure; 66 procedures annually) and radiological technologists (0.28 mSv/procedure; 71 procedures annually). Use of each type of protective tools: radiation safety glasses (0.07-mm-Pb), bag-valve-mask extension tube (20 cm) and radiation protective curtain (0.25-mm-Pb), reduced Hp(3) to the lens of the eye by 51%, 31% and 61%, respectively. ConclusionIntensive care physicians perform most assisted ventilations with the bag-valve-mask during “diagnostic” CT scans, and may exceed the equivalent dose limit for the lens of the eye if radiation safety glasses are not worn. If “multiple protective measures” are implemented, compliance with the equivalent dose limit for the lens of the eye should be achievable without placing significant burdens on physicians or medical institutions.
Highlights
The threshold dose for radiation-induced cataract has been thought to be 5 Gy for acute exposure and 8 Gy for hyperfractionated or prolonged exposure [1]
Many reports have shown that occupational dose to the lens of the eye is significant among physicians involved in clinical radiation care over many hours, such as interventional radiology (IR) of the neurovascular system [6, 7, 8, 9], cardiovascular system [8, 10] or tumor [8, 9, 11], and endoscopic retrograde cholangiopancreatography (ERCP) [8, 12, 13, 14]
Analysis of the dose ratio of the two GD-352M positioned orthogonally in vertical and horizontal directions relative to the ground showed that the vertical-to-horizontal dose ratio was virtually 1.0 for both left and right sides (Table 5)
Summary
The threshold dose for radiation-induced cataract has been thought to be 5 Gy for acute exposure and 8 Gy for hyperfractionated or prolonged exposure [1]. Seoul Statement lowered the threshold dose of cataract to 0.5 Gy and recommended a new equivalent dose limit for the lens of the eye, to specify occupational exposure in planned exposure situations, “For occupational exposure in planned exposure situations the Commission recommends an equivalent dose limit for the lens of the eye of 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv” [5] Since this recommendation, increased interest has been shown in cataracts and occupational dose to the lens of the eye for medical staff in Japan. While reports have already investigated nurses assisting pediatric patients in the CT room during CT scans for “diagnostic” purposes [27] or in phantom experiments [28, 29], no reports have described direct measurement in medical staff assisting adult patients undergoing high-dose imaging procedures
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