3D-printed eye lens dosemeter holder for use in interventional radiology and interventional cardiology

Highlights

• An inexpensive and comfortable eye lens dosimeter holder can be 3D printed.

• The 3D-printed holder fits a Panasonic TL single dosimeter element.

• Holders with Li₂B₄O₇ TLD are suitable for Hp(3) measurements in IR and IC.

• Properties of the ABS plastic are not affected by radiation in low range.

Abstract

Mandatory eye lens monitoring for exposed workers who are liable to receive an equivalent dose to the lens of the eye higher than 15 mSv in one year, required by the new European Basic Safety Standard 2013/59 and the recommendation given by the International Commission on Radiological Protection to lower the annual dose limit for the lens of the eye to 20 mSv, have put dosimetry services using Panasonic dosemeters in a difficult position. There are no commercially available eye lens dosemeter holders to fit Panasonic TLD pellets. Therefore, we designed and 3D printed inexpensive, splash proof, reusable and comfortable holders to fit a Panasonic ⁿLi₂ⁿB₄O₇:Cu pellet. The eye lens dosemeter consists of an acrylonitrile butadiene styrene (ABS) plastic holder with a slot for a TLD pellet. The slot with the TLD pellet is covered by a heat-shrink tube and shortly heated with hot air to shrink wrap. Results of combined energy/angular response measurements, for all photon radiation qualities used, relative to N-100 at 0° as the reference energy, were within IEC 62387:2012 limits. Additionally, electron spin resonance spectroscopy was used to test the effect of irradiation to the degradation properties of the plastic ABS holder. The dosemeter is to be worn fixed to a headband, close to the eye, on the left side of the head or in the middle of the forehead.

Introduction

The lens of the eye is one of the most radiosensitive organs in the body (Ainsbury et al., 2009). Cataracts are a condition in which eye lens opacity occurs and has been documented as an ocular complication associated with exposure to ionising radiation (Chodick et al., 2008). Besides ionizing radiation, there are many risk factors for cataracts such as age, exposure to sunlight, alcohol and nicotine consumption, diabetes and use of corticosteroids (Ainsbury et al., 2009). The research in the first decade of this century has indicated that radiation-associated opacities of the lens of the eye occur at lower doses than previously stated (Ainsbury et al., 2009; Shore et al., 2010). In light of new research data, the International Commission on Radiological Protection (ICRP) has reduced the annual dose limit for the equivalent dose to the lens of the eye from 150 mSv to 20 mSv (20 mSv/y, averaged over 5 years, with no single year exceeding 50 mSv) (ICRP, 2011, 2012). The International Atomic Energy Agency (IAEA) also recommends to monitor the eye lens dose for exposed workers who work in non-uniform radiation fields (IAEA, 2014). Occupational exposures to the lens of the eye may occur in nuclear power plants, research or industrial facilities and medicine (Hoedlmoser et.al. 2019 and the references cited therein). During interventional radiology (IR) and interventional cardiology (IC) procedures, the medical staff and the patients experience prolonged exposure to non-uniform radiation fields. In such procedures, physicians and other medical personnel remain close to patients and are exposed to high levels of scattered radiation up to several hours a day (Vano et al., 2009, 2010). Some of the highest occupational doses in medicine are received by physicians (interventional radiologists and cardiologists) performing fluoroscopically guided interventions (Vano et al., 2010). In the ICRP Publication 139 (ICRP, 2018), it was suggested that in IR or IC practices when protective glasses are not worn, the use of collar dosemeter placed over the protective apron on the side adjacent to the x-ray tube is only an indicator of the eye dose. Therefore, it is recommended to improve the accuracy of the measurement by wearing an eye dosemeter adjacent to the most exposed eye. A number of studies (Efstathopoulos et al., 2011; Ishii et al., 2019; Principi et al., 2014; Vanhavere et al., 2012) have investigated the position where an eye dosemeter should be worn, in situations when no eye protection (protective glasses, ceiling-suspended screens, etc.) is used. The evaluated positions were the left eyebrow ridge or the middle of the forehead. The overall conclusion is that the optimum position strongly depends on the procedure and practice of the operator. A recently published study (Ishii et al., 2019) suggested that the placement of the dosemeter on the left side of the head, near the eye, provides good estimates for physicians, and the forehead position is more suitable to monitoring nurses. Furthermore, the new European Basic Safety Standard 2013/59 (European Comission, 2014) requires mandatory eye lens monitoring for exposed workers liable to receive an equivalent dose for the lens of the eye higher than 15 mSv in one year. The aforementioned requirements and recommendations have put dosimetry services using Panasonic dosemeters in a difficult position. There were and there still are no commercially available inexpensive eye lens dosemeter holders that could fit a single Panasonic thermoluminescent dosemeter (TLD) pellet. Panasonic single TLD pellets are comprising a thin layer of Li₂B₄O₇:Cu crystals, a highly sensitive TL material with an effective atomic number Z_eff = 7.3 very close to that of soft biological tissue (Z_eff = 7.4) (Yamamoto et al., 1982; Prokić, 2002). There is one model recently developed by Dosilab AG, Switzerland, described in the literature (Hoedlmoser et al., 2019), but it requires the use of an ultrasonic welding device to seal the dosemeter, which is not affordable for small dosimetry services, and the holder is not reusable. Therefore, we designed and 3D printed an inexpensive, splash proof and reusable holder to fit Panasonic Li₂B₄O₇:Cu and other manufacturers’ single dosemeter elements. 3D printing technology has rapidly advanced and has entered into various fields due to developments in technology and affordable prices. In medicine, 3D printing of personalized medical devices, implants and external prostheses has been applied and finds many applications in medical imaging (Squelch, 2018). The main aim of this study was to investigate the adequacy of such in-house produced dosemeters to perform reliable Hp(3) measurements for photon fields. In order to examine the possible effect of irradiation on the degradation process in the acrylonitrile butadiene styrene (ABS) plastic holders, electron spin resonance (ESR) spectroscopy has been used as it is a widespread and well established technique for the study of intrinsic properties of polymers, as well radiation-induced changes, especially in cases when the sensitivity of other analytical methods is not sufficient (IAEA, 2016; Naveed et al., 2018).