On the Use of Optically Stimulated Luminescent Dosimeter for Surface Dose Measurement during Radiotherapy

This study was carried out to investigate the suitability of using the optically stimulated luminescence dosimeter (OSLD) in measuring surface dose during radiotherapy. The water equivalent depth (WED) of the OSLD was first determined by comparing the surface dose measured using the OSLD with the percentage depth dose at the buildup region measured using a Markus ionization chamber. Surface doses were measured on a solid water phantom using the OSLD and compared against the Markus ionization chamber and Gafchromic EBT3 film measurements. The effect of incident beam angles on surface dose was also studied. The OSLD was subsequently used to measure surface dose during tangential breast radiotherapy treatments in a phantom study and in the clinical measurement of 10 patients. Surface dose to the treated breast or chest wall, and on the contralateral breast were measured. The WED of the OSLD was found to be at 0.4 mm. For surface dose measurement on a solid water phantom, the Markus ionization chamber measured 15.95% for 6 MV photon beam and 12.64% for 10 MV photon beam followed by EBT3 film (23.79% and 17.14%) and OSLD (37.77% and 25.38%). Surface dose increased with the increase of the incident beam angle. For phantom and patient breast surface dose measurement, the response of the OSLD was higher than EBT3 film. The in-vivo measurements were also compared with the treatment planning system predicted dose. The OSLD measured higher dose values compared to dose at the surface (Hp(0.0)) by a factor of 2.37 for 6 MV and 2.01 for 10 MV photon beams, respectively. The measurement of absorbed dose at the skin depth of 0.4 mm by the OSLD can still be a useful tool to assess radiation effects on the skin dermis layer. This knowledge can be used to prevent and manage potential acute skin reaction and late skin toxicity from radiotherapy treatments.     

A multicenter study of radiation doses to the eye lenses of medical staff performing non-vascular imaging and interventional radiology procedures in Japan

PurposeThis study aimed to measure the eye lens doses received by physicians and other medical staff participating in non-vascular imaging and interventional radiology procedures in Japan.Material and methodsFrom October 2014 to March 2017, 34 physicians and 29 other medical staff engaged in non-vascular imaging and interventional radiology procedures at 18 Japanese medical facilities. These professionals wore radioprotective lead glasses equipped with small, optically stimulated luminescence dosimeters and additional personal dosimeters at the neck during a 1-month monitoring period. The H_p(3) and the H_p(10) and H_p(0.07) were obtained from these devices, respectively. The monthly H_p(3), H_p(10), and H_p(0.07) for each physician and other medical staff member were then rescaled to a 12-month period to enable comparisons with the revised occupational equivalent dose limit for the eye lens.ResultsAmong physicians, the average annual H_p(3) values measured by the small luminescence dosimeters on radioprotective glasses were 25.5 ± 38.3 mSv/y (range: 0.4–166.8 mSv/y) and 9.3 ± 16.6 mSv/y (range: 0.3–82.4 mSv/y) on the left and right sides, respectively. The corresponding values for other medical staff were 3.7 ± 3.1 mSv/y (range: 0.4–10.4 mSv/y) and 3.2 ± 2.7 mSv/y (range: 0.5–11.5 mSv/y), respectively.ConclusionsThe eye lens doses incurred by physicians and other medical staff who engaged in non-vascular imaging and interventional radiology procedures in Japan were provided. Physicians should wear radioprotective glasses and use additional radioprotective devices to reduce the amount of eye lens doses they receive.     

Eye lens and thyroid gland radiation exposure for patients undergoing brain computed tomography examination

This study aims to estimate the effective radiation dose and organ dose from head CT procedures. It was conducted in three main private hospitals in Khartoum State-Sudan, using Toshiba machines with 64 slices. The total number of patients included in this study was 142 patients (82 males and 60 females). The effective dose and organ dose were calculated by CT Expo software. The effective dose slightly varied among patients according to gender and age. The effective dose for female patients (5.99 mSv) was higher than that for male patients (5.84 mSv), and the pediatric dose (5.46 mSv) was lower than the adults’ dose (5.94 mSv).The dose for eye lens was found lower for male patients (89.117 mSv) than the dose for female patients (94.62) mSv). According to patients’ age: the dose received by the lens of the eye was much lower in pediatric (79.93 mSv) than the adults (92.41 mSv). The dose for thyroid in female patients (33.52 mSv) was higher than the male patients (28 mSv). The pediatric dose (28.34 mSv) was lower than the adults’ dose (30.64 mSv).Departmental imaging protocol and lack of training among hospital staff are expected to be responsible for these variations. Therefore, this study recommends that the CT technologists be trained on suitable strategies to achieve dose optimization. Moreover, patients’ doses must be monitored regularly.     

Radioprotection of eye lens using protective material in neuro cone-beam computed tomography: Estimation of dose reduction rate and image quality

PurposeIn cerebral angiography, for diagnosis and interventional neuroradiology, cone-beam computed tomography (CBCT) scan is frequently performed for evaluating brain parenchyma, cerebral hemorrhage, and cerebral infarction. However, the patient’s eye lens is more frequently exposed to excessive doses in these scans than in the previous angiography and interventional neuroradiology (INR) procedures. Hence, radioprotection for the lenses is needed. This study selects the most suitable eye lens protection material for CBCT from among nine materials by evaluating the dose reduction rate and image quality.MethodsTo determine the dose reduction rate, the lens doses were measured using an anthropomorphic head phantom and a real-time dosimeter. For image quality assessment, the artifact index was calculated based on the pixel value and image noise within various regions of interest in a water phantom.ResultsThe protective materials exhibited dose reduction; however, streak artifacts were observed near the materials. The dose reduction rate and the degree of the artifact varied significantly depending on the protective material. The dose reduction rates were 14.6%, 14.2%, and 26.0% when bismuth shield: normal (bismuth shield in the shape of an eye mask), bismuth shield: separate (two separate bismuth shields), and lead goggles were used, respectively. The “separate” bismuth shield was found to be effective in dose reduction without lowering the image quality.ConclusionWe found that bismuth shields and lead goggles are suitable protective devices for the optimal reduction of lens doses.     

Addressing the efficiency of X-ray protective eyewear: Proposal for the introduction of a new comprehensive parameter,the Eye Protection Effectiveness (EPE)

Radioprotection of the eye lens of medical staff involved in Surgical procedures is a subject of international debates since ICRP recommended, on 2011, a lower equivalent dose limit for the lens of the eye. In this work we address the effectiveness of different models of X-ray protective eyewear by relating actual dosimetry measurements to an ad hoc developed mathematical model, in order to disentangle the contribution of geometrical factors and shield capabilities. Phantom irradiation was carried out in fixed exposure conditions in angiographic room: we found that measured Dose Reduction Factors (DRF) strongly depend on the ergonomics of the investigated eyewear. Actually a very poor DRF was observed in the case of a glass model in spite of its high nominal attenuation, whereas a protective tool with low shielding capabilities such a visor resulted much more effective as a consequence of is shape (i.e. extended geometric protection of the eye lens). Our work highlights the need of the introduction of a specific parameter to quantify the effectiveness of the protection tools and able to predict their DRF by taking into account the geometry of the clinical condition of exposure. Aiming at making steps forward the standardization of the guidelines concerning the features of eye protective tools, we developed a simple mathematical model describing the eye lens irradiation geometry which allows the introduction, for each eyewear, of a comprehensive parameter, the Eye Protection Effectiveness (EPE), that, for any defined clinical irradiation condition and glass shielding capabilities and shape, defines the overall effective X-ray protection of the eyewear.     

Eye lens dose correlations with personal dose equivalent and patient exposure in paediatric interventional cardiology performed with a fluoroscopic biplane system

PurposeTo analyse the correlations between the eye lens dose estimates performed with dosimeters placed next to the eyes of paediatric interventional cardiologists working with a biplane system, the personal dose equivalent measured on the thorax and the patient dose.MethodsThe eye lens dose was estimated in terms of H_p(0.07) on a monthly basis, placing optically stimulated luminescence dosimeters (OSLDs) on goggles. The H_p(0.07) personal dose equivalent was measured over aprons with whole-body OSLDs. Data on patient dose as recorded by the kerma-area product (P_KA) were collected using an automatic dose management system. The 2 paediatric cardiologists working in the facility were involved in the study, and 222 interventions in a 1-year period were evaluated. The ceiling-suspended screen was often disregarded during interventions.ResultsThe annual eye lens doses estimated on goggles were 4.13 ± 0.93 and 4.98 ± 1.28 mSv. Over the aprons, the doses obtained were 10.83 ± 0.99 and 11.97 ± 1.44 mSv. The correlation between the goggles and the apron dose was R² = 0.89, with a ratio of 0.38. The correlation with the patient dose was R² = 0.40, with a ratio of 1.79 μSv Gy⁻¹ cm⁻². The dose per procedure obtained over the aprons was 102 ± 16 μSv, and on goggles 40 ± 9 μSv. The eye lens dose normalized to P_KA was 2.21 ± 0.58 μSv Gy⁻¹ cm⁻².ConclusionsMeasurements of personal dose equivalent over the paediatric cardiologist’s apron are useful to estimate eye lens dose levels if no radiation protection devices are typically used.     

Occupational radiation dose of personnel involved in sentinel node biopsy procedure

IntroductionSentinel node biopsy is a procedure used for axillary nodal staging in breast cancer surgery. The process uses radioactive ^99mTc isotope for mapping the sentinel node(s) and all the staff involved in the procedure is potentially exposed to ionizing radiation. The colloid for radiolabelling (antimone-sulphide) with ^99mTc isotope (half-life 6 h) is injected into the patient breast. The injection has activity of 18.5 MBq. The surgeon removes the primary tumor and detects active lymph nodes with gamma detection unit. The tumor as well as the active nodal tissue is transferred to pathologist for the definitive findings. The aim of the study was to measure dose equivalents to extremities and whole body for all staff and suggest practice improvement in order to minimize exposure risk.Materials and methodsThe measurements of the following operational quantities were performed: Hp(10) personal dose equivalent to whole body and Hp(0.07) to extremities for staff as well as ambiental dose for operating theatre and during injection.Hp(0.07) were measured at surgeon’s finger by ring thermoluminescent dosimeter (TLD) type MTS-N, and reader RADOS RE2000. Surgeon and nurse were wearing TLD personal dosimeter at the chest level. Anesthesiologist and anesthetist were wearing electronic personal dosimeters, while pathologist was wearing ring TLD while manipulating tissue samples.Electronic dosimeters used were manufactured by Polimaster, type PM1610.All TLD and electronic dosimeters data were reported, including background radiation. Background radiation was also monitored separately. Personal TLDs are standard for this type of personal monitoring, provided by accredited laboratory.Measurements of ambiental dose in workplaces of other staff involved around the patient was performed before the surgery took place, by calibrated survey meters manufactured by Atomtex, type 1667.The study involved two surgeons and one pathologist, two anesthesiologists and three anesthetists during two months period.Results and discussionThe doses received by all staff are evaluated using passive and active personal dosimeters and ambiental dose monitors and practice was improved based on results collected. Average annual whole body dose for all staff involved in the procedure was less than 0.8 mSv. Extremity dose equivalents to surgeon and pathologist were far below the limits set for professionally exposed (surgeon) and for public (pathologist).ConclusionsAlthough has proven to be very safe for all staff, additional measures for radiation protection, in accordance to ALARA principle (As Low As Reasonably Achievable) should be conducted. The recommendations for practice improvement with respect to radiation protection were issued.     

Dose profiles for lung and breast regions at prospective and retrospective CT coronary angiography using optically stimulated luminescence dosimeters on a 64-detector CT scanner

PurposeThe purpose of our study was to acquire dose profiles at critical organs of lung and breast regions using optically stimulated luminescence (OSL) dosimeters; assess the actual radiation dose delivered at retrospective and prospective computed tomography coronary angiography (CTCA).Materials and methodsUsing a chest CT phantom we applied a prospectively-gated step-and-shoot- and a retrospectively-gated helical mode on a 64-detector row CT scanner. Retrospective scan mode was used with and without electrocardiogram (ECG) based tube current modulation. OSL dosimeters were used to measure dose profiles. In the both scan modes we acquired dose profiles and determined the mean and maximum dose in left lung and in left breast regions.ResultsIn prospective mode, the mean dose was 21.53 mGy in left lung- and 23.59 mGy in left breast region. With respect to the retrospective mode, the mean dose with tube current modulation was 38.63 mGy for left lung- and 46.02 mGy for left breast region, i.e. 0.56 and 0.55 times lower than the mean dose without modulation.ConclusionThe OSL dosimeter is useful for measurement of the actual radiation dose along z-axis at lung and breast regions in the prospective and the retrospective CTCA.     

Occupational radiation exposure in vascular interventional radiology: A complete evaluation of different body regions

PurposeTo perform a complete evaluation on radiation doses, received by primary and assistant medical staff, while performing different vascular interventional radiology procedures.Materials and methodsWe evaluated dose received in different body regions during three categories of vascular procedures: lower limb angiography (Angiography), lower limb percutaneous transluminal angioplasty (Angioplasty) and stent graft placement for abdominal aortic aneurysm treatment (A. A. A. Treatment). We positioned the dosimeters near the eye lens, thyroid, chest, abdomen, hands, and feet of the interventional physicians. Equivalent dose was compared with annual dose limits for workers in order to determine the maximum number of procedures per year that each physician could perform. We assessed 90 procedures.ResultsWe found the highest equivalent doses in the A. A. A. Treatment, in which 90% of the evaluations indicated at least one region receiving more than 1 mSv per procedure. Angioplasty was the only procedural modality that provided statistically different doses for different professionals, which is an important aspect on regards to radiological protection strategies. In comparison with the dose limits, the most critical region in all procedures was the eye lens.ConclusionsSince each body region of the interventionist is exposed to different radiation levels, dose distribution measurements are essential for radiological protection strategies. These results indicate that dosimeters placed in abdomen instead of chest may represent more accurately the whole body doses received by the medical staff. Additional dosimeters and a stationary shield for the eye lens are strongly recommended.     

Étude dosimétrique de préparations de médicaments radiopharmaceutiques au 68Ga

AimProduction of ⁶⁸Ga-radiopharmaceuticals is a rapidly growing field in France. However, operators may already be involved in other radiopharmaceutical activities. It is thus necessary to know the exposure of this new activity.Material and methodsFor passive dosimetry, a radiophotoluminescent (RPL) dosimeter, a thermoluminescent (TLD) chip, 2 TLD rings and a passive dosimeter for crystalline were used. For active dosimetry, an extremity dosimeter and a whole body dosimeter were used. This study was performed during semi-automatized production of ⁶⁸Ga-investigational medicinal products. Values were normalized to 500MBq manipulated (median activity using a 1850MBq ⁶⁸Ga-generator), 60 radiosynthesis (maximum enrollment ability of our center) and 2 operators. A LB123 proportional counter was used for quantification of external exposition to 10MBq ⁶⁸Ge and internal exposition by inhalation was theoretically assessed. ⁶⁸Ga emission attenuation by collective protection equipments was also discussed.ResultsConsidering passive dosimetry, the equivalent dose to extremities was 21.75 ± 0.34 mSv, the whole-body effective dose was 0.189 ± 0.011 mSv and the dose to crystalline was 0.925 ± 0.009 mSv. Considering active dosimetry, the equivalent dose to extremities was 8,75 ± 0.12 mSv and the whole-body effective dose was 0,088 ± 0.009 mSv. Total exposure to ⁶⁸Ge was 1.75 μSv.ConclusionIn our hands, ⁶⁸Ga is a directly transposable activity in radiopharmacies already equipped for ¹⁸F because of a dosimetry complying with regulatory limits and suitable radiation protection of collective equipments.     

The influence of operator position,height and body orientation on eye lens dose in interventional radiology and cardiology: Monte Carlo simulations versus realistic clinical measurements

ObjectiveThis paper aims to provide some practical recommendations to reduce eye lens dose for workers exposed to X-rays in interventional cardiology and radiology and also to propose an eye lens correction factor when lead glasses are used.MethodsMonte Carlo simulations are used to study the variation of eye lens exposure with operator position, height and body orientation with respect to the patient and the X-ray tube. The paper also looks into the efficiency of wraparound lead glasses using simulations. Computation results are compared with experimental measurements performed in Spanish hospitals using eye lens dosemeters as well as with data from available literature.ResultsSimulations showed that left eye exposure is generally higher than the right eye, when the operator stands on the right side of the patient. Operator height can induce a strong dose decrease by up to a factor of 2 for the left eye for 10-cm-taller operators. Body rotation of the operator away from the tube by 45°–60° reduces eye exposure by a factor of 2. The calculation-based correction factor of 0.3 for wraparound type lead glasses was found to agree reasonably well with experimental data.ConclusionsSimple precautions, such as the positioning of the image screen away from the X-ray source, lead to a significant reduction of the eye lens dose. Measurements and simulations performed in this work also show that a general eye lens correction factor of 0.5 can be used when lead glasses are worn regardless of operator position, height and body orientation.     

Radiation dose in repeated CT guided radiofrequency ablations

ObjectiveTo calculate the cumulative effective and skin doses in patients that underwent repeated CT guided radiofrequency ablations (RFA).Materials and methodsFrom all patients that had undergone RFA during a five years period those which had three or more RFAs were selected. Using the CT images DICOM data, the dose length product (DLP), effective dose (E), skin dose profiles as well as the peak skin dose (PSD) were calculated, using appropriate methods and software developed for this purpose. For each patient, cumulative DLP and E were also calculated from the sum of the respective figures of each individual procedure. To calculate PSD, the skin dose profiles of each procedure were overlaid on the same Z-axis scale using anatomical landmarks for reference and the skin doses to each point were summed up.ResultsFive patients were studied; four had undergone 3 RFAs and one 10 RFAs. Cumulative DLP, E and PSD ranges were 5.6–22.3 Gy cm, 0.08–0.36 Sv and 0.8–3.4 Gy, respectively. Median E and PSD values per RFA were 35 mSv and 0.4 Gy, respectively. For comparison purposes it must be noted that in this CT department a routine abdomen-pelvis scan results to an E of about 10 mSv.ConclusionsPatients that undergo repeated RFAs are exposed to considerably high radiation exposure levels. When these patients are in the final stage of malignant diseases, stochastic effects may not be of major concern. However, optimization of the exposure factors and monitoring of these patients to avoid skin injuries are required.     

A Monte Carlo simulation for the estimation of patient dose in rest and stress cardiac computed tomography with a 320-detector row CT scanner

PurposeTo estimate organ dose and effective dose for patients for cardiac CT as applied in an international multicenter study (CORE320) with a 320-Detector row CT scanner using Monte Carlo (MC) simulations and voxelized phantoms. The effect of positioning of the arms, off-centering the patient and heart rate on patient dose was analyzed.MethodsA MC code was tailored to simulate the geometry and characteristics of the CT scanner. The phantoms representing the adult reference male and female were implemented according to ICRP 110. Effective dose and organ doses were obtained for CT acquisition protocols for calcium scoring, coronary angiography and myocardial perfusion.ResultsFor low heart rate, the normalized effective dose (E) for cardiac CT was higher for female (5.6 mSv/100 mAs) compared to male (2.2 mSv/100 mAs) due to the contribution of female breast tissue. Averaged E for female and male was 11.3 mSv for the comprehensive cardiac protocol consisting of calcium scoring (1.9 mSv); coronary angiography including rest cardiac perfusion (5.1 mSv) and stress cardiac perfusion (4.3 mSv). These values almost doubled at higher heart rates (20.1 mSv). Excluding the arms increased effective dose by 6–8%, centering the patient showed no significant effect. The k-factor (0.028 mSv/mGy.cm) derived from this study leads to effective doses up to 2–3 times higher than the values obtained using now outdated methodologies.ConclusionMC modeling of cardiac CT examinations on realistic voxelized phantoms allowed us to assess patient doses accurately and we derived k-factors that are well above those published previously.     

Wrist dosimeter in nuclear medicine – An alternative for the ring dosimeter?

PurposeIndividual dosimetry is undoubtedly one of the best methods of assessing the exposure of personnel to ionizing radiation, however in case of nuclear medicine, the method applied to measure the dose does not always present a picture of the worker’s actual exposure. The highly non-homogeneous dose distribution on the hand means that the ring dosimeter, routinely used to measure the Hp(0.07), provides only approximate dose values received by fingertips, the body part most exposed to ionizing radiation. This paper is an attempt to answer the question whether the wrist dosimeter used as a replacement for the ring dosimeter is able to provide information on doses for the most exposed fragments of the hand of an employee during handling procedures with the use of radiopharmaceuticals.MaterialsThroughout measurements performed in five nuclear medicine facilities, high-sensitivity thermoluminescent detectors were used.ResultsCorrection coefficients have been determined, which constitute an amendment to be made to move from the dose recorded by the wrist dosimeter to the doses received by the most exposed hand fragments. The fingertips received on average 25 times higher doses, compared to the values recorded by the wrist dosimeter.ConclusionsA wrist dosimeter can be used to measure the Hp(0.07) in nuclear medicine, including as a gauge of the most exposed parts of the hand – the fingertips. However, the applicability of correction coefficients makes it necessary to ensure a stable position of the wrist dosimeter during routine procedures.     

哈尔滨市某三级医院介入人员外照射个人剂量现况调查研究

目的:了解哈尔滨市某三级医院介入人员外照射个人剂量现况和本院辐射防护情况,以期为本院介入防护策略提供一定的科学依据。方法:按照《中华人民共和国国家职业卫生标准》(GBZ128-2016)版本要求,在2016年7月8号～2017年7月8号期间,采用双剂量计监测目标人群年外照射个人剂量,x2检验和logistic回归分析介入人员外照射个人剂量的影响因素。结果:年外照射最小个人剂量为0.08mSv,最大个人剂量为3.60mSv,平均个人剂量为0.23mSv,x2检验表明科室(x~2=50.420,P0.001)、职业类别(x~2=32.992,P0.001)、职称(x~2=33.806,P0.001)和学历(x2=9.289,P0.05)有统计学意义;logistic回归分析均表明,职称、工作年限、职业类别进入方程,但只有职称(Wals=4.896,P0.05)和职业类别(Wals=8.424,P0.05)有统计学意义,医务人员职称和职业类别(Wals=8.424,P0.05)是影响个人外照射剂量的因素。结论:本院总体外照射防护措施得当,本院从事介入工作的相关医务人员中,高级职称医务人员外照射个人剂量低于中、低级职称医务人员;技师外照射个人剂量高于护士和医生。根据本研究结果,在医院的外照射防护中应采取一些措施,比如合理分配工作,避免同一工种医务人员长时间暴露于介入相关外照射,避免中低级职称医生长时间接触介入相关外照射,加强医务人员防护意识,适当调整工作岗位,适时进行防护培训。     

A strategy to determine off-axis dosimetric leaf gap using OSLD and EPID

BackgroundThe aim of the study was to investigate the dosimetric feasibility of using optically stimulated luminescence dosimeters (OSLD) and an electronic portal imaging device (EPID) for central axis (CA X) and off-axis (OAX) dosimetric leaf gap (DLG) measurement.Materials and methodsThe Clinac 2100C/D linear accelerator equipped with Millennium-120 multileaf collimator (MLC) and EPID was utilized for this study. The DLG values at CA X and ± 1 cm OAX (1 cm superior and inferior to the CA X position, respectively along the plane perpendicular to MLC motion) were measured using OSLD (DLG_OSLD) and validated using ionization chamber dosimetry (DLG_ICD). The two-dimensional DLG map (2D DLG_EPID) was derived from the portal images of the DLG plan using a custom-developed software application that incorporated sliding aperture-specific correction factors.ResultsDLG_OSLD and DLG_ICD, though measured with diverse setup in different media, showed similar variation both at CA X and ± 1 cm OAX positions. The corresponding DLG_EPID values derived using aperture specific corrections were found to be in agreement with DLG_OSLD and DLG_ICD. The 2D DLG_EPID map provides insight into the varying patterns of the DLG with respect to each leaf pair at any position across the exposed field.ConclusionsCommensurate results of DLG_OSLD with DLG_ICD values have proven the efficacy of OSLD as an appropriate dosimeter for DLG measurement. The 2D DLG_{EP ID} map opens a potential pathway to accurately model the rounded-leaf end transmission with discrete leaf-specific DLG values for commissioning of a modern treatment planning system.     

Monte Carlo simulation of eye lens dose reduction from CT scan using organ based tube current modulation

PurposeTo investigate lens dose reduction with organ based tube current modulation (TCM) using the Monte Carlo method.MethodsTo calculate lens dose with organ based TCM, 36 pairs of X-ray sources with bowtie filters were placed around the patient head using a projection angle interval of 10° for one rotation of Computed Tomography (CT). Each projection was simulated respectively. Both voxelized and stylized eye models and Chinese reference male phantoms were used in the simulation, and tube voltages 80, 100, 120 and 140 kVp were used.ResultsDose differences between two eye models were less than 20%, but large variations were observed among dose results from different projections of all tube voltages investigated. Dose results from 0° (AP) directions were 60 times greater than those from 180° (PA) directions, which enables organ based TCM reduce lens doses by more than 47%.ConclusionsOrgan based TCM may be used to reduce lens doses. Stylized eye models are more anatomically realistic compared with voxelized eye models and are more reliable for dose evaluation.     

A new less toxic polymer gel dosimeter: Radiological characteristics and dosimetry properties

PurposeA new polymer gel dosimeter recipe was investigated that may be more suitable for widespread applications than polyacrylamide gel dosimeters, since the extremely toxic acrylamide has been replaced with the less harmful monomer 2-Acrylamido 2-Methyl Propane Sulfonic acid (AMPS).MethodsThe new formulation was named PAMPSGAT. The MRI response (R2) of the dosimeters was analyzed for conditions of varying dose, dose rate, and temperature during scanning. Radiological properties of the PAMPSGAT polymer gel dosimeter were investigated.ResultsThe dose-response (R2) of AMPS/Bis appears to be linear over a dose range 10–40 Gy. The percentage of difference between the R2 values for imaging at 15 °C and MRI room temperature is about 4.6% for vial with 40 Gy absorbed dose which decreased to less than 1% for imaging at 20 °C. The percentage difference of Zeff of PAMPSGAT gel and soft tissue was less than 1% in the practical energy range (100 KeV–100 MeV). The electron density of the PAMPSGAT polymer gel was 2.9% higher than that of muscle. Results showed that the sensitivity of PAMPSGAT polymer gel dosimeter irradiated by ⁶⁰Co (energy = 1.25 MeV) is about 27.7% higher than that of irradiated using a 6 MeV Linac system.ConclusionsTemperature during MRI scanning has a small effect on the R2 response of the PAMPSGAT polymer gel dosimeter. Results confirmed tissue equivalency of the PAMPSGAT polymer gel dosimeter in most practical energy range. The PAMPSGAT polymer gel dosimeter response depends on energy and dose rate.     

Eye lens exposure to medical staff during endoscopic retrograde cholangiopancreatography

The paper presents a study of the radiation doses to eye lens of medical staff during endoscopic retrograde cholangiopancreatography (ERCP) procedures performed in a busy gastroenterology department. For each procedure the dose equivalent to the eye, exposure time, dose rate, Kerma Area Product and fluoroscopy time were recorded. Measurements were performed for a period of two months in four main positions of the operating staff, and then extrapolated to estimate annual doses. The fluoroscopy time per ERCP procedure varied between 1.0 min and 28.8 min, with a mean value of 4.6 min. The calculated mean eye dose per procedure varied between 34.9 μSv and 93.3 μSv. The results demonstrated that if eye protection is not used, annual doses to the eye lens of the gastroenterologist performing the procedure and the anesthesiologist can exceed the dose limit of 20 mSv per year.     

Epidemiological studies of cataract risk at low to moderate radiation doses: (not) seeing is believing

The prevailing belief for some decades has been that human radiation-related cataract occurs only after relatively high doses; for instance, the ICRP estimates that brief exposures of at least 0.5-2 Sv are required to cause detectable lens opacities and 5 Sv for vision-impairing cataracts. For protracted exposures, the ICRP estimates the corresponding dose thresholds as 5 Sv and 8 Sv, respectively. However, several studies, especially in the last decade, indicate that radiation-associated opacities occur at much lower doses. Several studies suggest that medical or environmental radiation exposure to the lens confers risk of opacities at doses well under 1 Sv. Among Japanese A-bomb survivors, risks for cataracts necessitating lens surgery were seen at doses under 1 Gy. The confidence interval on the A-bomb dose threshold for cataract surgery prevalence indicated that the data are compatible with a dose threshold ranging from none up to only 0.8 Gy, similar to the dose threshold for minor opacities seen among Chernobyl clean-up workers with primarily protracted exposures. Findings from various studies indicate that radiation risk estimates are probably not due to confounding by other cataract risk factors and that risk is seen after both childhood and adult exposures. The recent data are instigating reassessments of guidelines by various radiation protection bodies regarding permissible levels of radiation to the eye. Among the future epidemiological research directions, the most important research need is for adequate studies of vision-impairing cataract after protracted radiation exposure.