Optically Stimulated Luminescence Dosimeters Research Articles

A practical method for the reuse of nanoDot OSLDs and predicting sensitivities up to at least 7000cGy.

Optically stimulated luminescence dosimeter (OSLDs) are often used to make in vivo dose measurements. Most users calibrate the OSLDs using the software provided by the vendor which typically is intended for doses up to about 300cGy with an uncertainty of ±5.5%. OSLDs that reach that dose are then discarded, and new ones are purchased and calibrated. A method has been developed for reusing OSLDs and predicting dose sensitivity up to at least 7000cGy. The nanoDot OSLDs used in this study were routinely used to do in vivo measurements for TBI patients. Instead of using the calibration program provided by the vendor, each nanoDot was bleached to about 100 counts (~0.1cGy), then calibrated with 50cGy to produce a sensitivity specific to each nanoDot prior to the patient measurement. NanoDots were read in the hardware mode and the sensitivity factor was applied manually to subsequent patient in-vivo TBI measurements. This was followed by bleaching prior to the next use. The changes of nanoDot sensitivity relative to accumulated dose were analyzed among nine nanoDots. In addition, a method to predict a nanoDot's sensitivity was investigated which aims to reduce the number of sensitivity calibrations while retaining dosimetric accuracy. Individual per-use nanodot calibrations were performed up to 7000cGy for 37 clinical TBI patients. Among the nine nanoDots analyzed in this paper, the sensitivity vs accumulated dose decreased linearly up to about 3000cGy, with linear fitting curve R2 values above 0.93. After 3000cGy of accumulated dose, the sensitivity started to plateau and tended to increase by 6000cGy, with 2nd order polynomial curve R2 values above 0.94. With this finding, an efficient and accurate method to predict nanoDots' sensitivities was developed. With the method applied to the nine OSLDs, a total of 127 sensitivities were predicted and retrospectively compared with measured sensitivities. The predicted sensitivities agreed with measured sensitivities within ±4.0% with an average of -0.8%. This study is the first to demonstrate the reuse of nanoDot OSLDs on numerous patients with accumulated dose up to 7000cGy. Our nanoDot re-usage methodology is accurate, cost-saving and feasible. A time-saving method is also provided that allows a user to reuse a nanoDot with sensitivities predicted with better accuracy than the 5.5% value provided by the conventional batch calibration method.

Dosimetric measurement of testicular dose for colorectal cancer using optically-stimulated luminescent dosimeters in radiotherapy

In radiotherapy for colorectal cancer, control of the testicular dose in young patients is important, as exposure of the testis could lead to temporary or permanent infertility. Although the testis is located out of the treatment field in patients receiving radiotherapy, it is inevitably exposed to scattered radiation resulting from the interaction between primary beams and patients and collimators. In this study, dosimeters were used to measure the testicular dose with and without testicular shielding to verify the effect of shielding. Anthropomorphic phantoms representing a human were used to estimate the doses absorbed in testicular and whole-body studies. The anthropomorphic phantom was irradiated according to the treatment protocol for colorectal cancer. Measurements were made using optically-stimulated luminescent dosimeters (OSLDs), composed of carbon-doped aluminum oxide, with characteristics suitable for radiotherapy dosimetry studies. A set of OSLDs was placed on a testicular phantom, attached to the lower edge of the pelvis of the anthropomorphic phantom. Dosimeters were also placed surround a testicular shielding to estimate the scattered dose. The testicular dose was 60–85 cGy when a dose of 4500 cGy was delivered to the whole pelvic area, while the dose was reduced to 34–50 cGy when testicular shielding was used. In addition, the increase in the surrounding scattered dose due to the testicular shielding was not significant.

A newly developed OSL dosimeter based on beryllium oxide: BeO:Na,Dy,Er

This study aims to develop a high sensitivity Optically Stimulated Luminescence (OSL) dosimeter based on tissue-equivalent BeO:Na,Dy,Er ceramic (Zeff = 7.31) using the precipitation method. The material structure was confirmed by performing X-ray diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDS) analyses. Thermoluminescence (TL), OSL, and X-ray luminescence (XL) techniques were used for the investigation of the luminescence properties. BeO:Na,Dy,Er has two TL peaks located at ~170 and 350 °C (at a heating rate of 2 °C/s) found to be associated with the OSL signals using the step annealing procedure. The OSL signals of newly developed BeO:Na,Dy,Er pellets were found highly sensitive to beta radiation and almost linear with a linearity coefficient of 1.03, i.e., described by a relation y=a+bx1.03at a range of 0.1–50 Gy. We investigated that the sensitivity of OSL from BeO:Na,Dy,Er pellets is the same after repeated exposure and reprocessing. Except for instability in short storage times, negligible long-term OSL signal fading was observed for up to three months at ambient temperature, in dark. In XL analyses, a broad band emission from 200 nm to 500 nm was observed at different dopant concentrations. The OSL characteristics of this material were found to be very encouraging and convenient for personal and medical dosimetry applications.

Surface and near-surface dose measurements at beam entry and exit in a 1.5 T MR-Linac using optically stimulated luminescence dosimeters

The objective of this study is to measure surface and near-surface dose at entry and exit surfaces in a 1.5 T MR-Linac (Elekta AB, Stockholm, Sweden) using optically stimulated luminescence dosimeters (OSLDs). OSLDs were expected to be useful for measuring surface dose in a strong magnetic field because they can be taped to undersides to measure exit dose, and their dose response have been shown to be reasonably insensitive to variations in beam angle, beam energy, and magnetic fields.The surface and near-surface dose at the entry and exit of a 20 cm thick solid water phantom was measured with OSLDs for 5 × 5, 10 × 10, and 22 × 22 cm2 field sizes. The solid water phantom was elevated off the couch top to produce an air gap of 3.7 cm so as to observe the electron return effect (ERE) near the beam exit surface. Measurement depths ranged from surface to 15 mm deep from entry and exit surfaces. The phantom dose distribution was also computed in the Monaco (Elekta AB, Stockholm, Sweden) Monte Carlo treatment planning system (TPS).For the 5 × 5, 10 × 10, and 22 × 22 cm2 field sizes the surface dose at depth 0 mm was extrapolated from OSLD measurements to be 10.9%, 12.0%, and 13.5%. The surface entry dose was found to be far less field size-dependent compared to a conventional linac, likely due to a lack of electronic contamination due to the strong magnetic field perpendicular to the beam. The ERE effect was observed in the measurements near the exit surface of the phantom, and was in close agreement with the TPS calculation.

Best practices for radiation safety in radiography departments: Review

This review analyzes radiation exposure risks for healthcare professionals, specifically targeting anesthesia providers and nurses operating in high-radiation settings such as operating rooms and interventional radiology suites. The document outlines sources of radiation exposure, such as mobile radiography, fluoroscopy, and CT scans, emphasizing the cumulative effects of low-dose radiation. Concerns related to radiation exposure in pregnancy are examined, highlighting regulatory guidelines and the necessity of reducing fetal exposure. The review examines factors that affect occupational exposure, distinguishing between modifiable factors, such as procedural techniques and positioning, and non-modifiable factors, including patient size and procedure complexity. The significance of personal dosimeters, such as film badges and optically stimulated luminescent dosimeters (OSLDs), in the monitoring of radiation levels is highlighted, as is the necessity for correct usage and interpretation of dosimeter readings. This paper examines the effects of radiation exposure on nursing and biochemistry, highlighting the necessity for thorough radiation safety training for nurses and the role of biochemists in elucidating cellular responses to radiation and formulating mitigation strategies. The conclusion emphasizes the necessity of proactive monitoring, implementation of effective protective measures, and ongoing education to reduce radiation exposure and protect healthcare workers.

Reduction of Radiation Exposure to Operator with Radiation Protective Device in ERCP Procedure Using Over-coach X-ray TV System

It is important to reduce the dose received by medical staffs. The purpose of this study was to evaluate the effect of protective curtain and the property of small optically stimulated luminescence (OSL) dosimeters used for ambient dose measurement in fluoroscopy. The property of small OSL dosimeters was investigated in terms of uniformity, changing fluoroscopy time and polymethyl methacrylate (PMMA) thickness, and angular dependence. Paper pipes were assembled in glid shape and ambient dose was investigated by using small OSL dosimeters that were put on them with and without protective curtain. Air kerma was investigated by small OSL dosimeters that were put on a head phantom at the position of eyes. Dose response of small OSL dosimeters was independent of fluoroscopy time and PMMA thickness, so it is appropriate to measure ambient dose by small OSL dosimeters. In relation to ambient dose, there was significant difference with and without protective curtain (p<0.001, paired-t-test). These air kerma on the head phantom were reduced to approximately 20% by attaching protective curtain. In order to reduce the dose received by operators, it is desirable to use protective curtain.

Optically stimulated luminescence dosimetry performance of novel MgO–La(OH)3 phosphors

The aim of this work was to study the optically stimulated luminescence (OSL) properties of novel MgO co-doped with different lanthanides and lithium ions as well as to evaluate the feasibility of using the mentioned phosphors as OSL dosimeters. In this context, the OSL efficiency corresponding to different stimulation wavelengths and different filters was analyzed for all the samples. The properties of the most efficient material, namely, MgO–La(OH)3, were further studied. Moreover, the repeatability and linearity of the OSL response, the fading of the OSL signal and the minimum detectable dose were investigated. Finally, feasibility of using these compounds in OSL dosimetry was assessed.

AAPM TG 191: Clinical use of luminescent dosimeters: TLDs and OSLDs.

Thermoluminescent dosimeters (TLD) and optically stimulated luminescent dosimeters (OSLD) are practical, accurate, and precise tools for point dosimetry in medical physics applications. The charges of Task Group 191 were to detail the methodologies for practical and optimal luminescence dosimetry in a clinical setting. This includes: (a) to review the variety of TLD/OSLD materials available, including features and limitations of each; (b) to outline the optimal steps to achieve accurate and precise dosimetry with luminescent detectors and to evaluate the uncertainty induced when less rigorous procedures are used; (c) to develop consensus guidelines on the optimal use of luminescent dosimeters for clinical practice; and (d) to develop guidelines for special medically relevant uses of TLDs/OSLDs such as mixed photon/neutron field dosimetry, particle beam dosimetry, and skin dosimetry. While this report provides general guidelines for TLD and OSLD processes, the report provides specific details for TLD-100 and nanoDotTM dosimeters because of their prevalence in clinical practice.

Eye lens dose of medical personnel involved in fluoroscopy and interventional procedures at a Malaysian Hospital

ObjectiveThis study measured the radiation exposure of the eye lens of medical personnel performing fluoroscopy and interventional procedures at the Sarawak General Hospital in Kuching, Sarawak, Malaysia. This study was the first in Malaysia to utilise in vivo radiation measurement relatively near the eye lens. Methods41 medical personnel performing 79 procedures were monitored for their eye lens exposure using the NanoDot™ optically-stimulated luminescence dosimeters (OSLD) taped to the outer canthus of their eyes. The air-kerma area product (KAP), fluoroscopy time (FT) and number of procedure runs were also recorded. ResultsKAP, FT and number of runs were strongly correlated. However, only weak to moderate correlations were observed between these parameters with the measured eye lens doses. The average median equivalent eye lens dose was 0.052 mSv (ranging from 0.0155 to 0.672 mSv). The eye lens doses of primary operators were found to be significantly higher than their assistants due to the closer proximity to the patient and X-ray tube. The left eye lens of the operators received the highest amount of radiation due to their habitual positioning towards the radiation source. ConclusionKAP and FT were not useful in predicting the equivalent eye lens dose exposure in interventional radiological procedures. Direct in vivo measurements were needed to provide a better estimate of the eye lens doses received by medical personnel during these procedures.This study highlights the importance of using direct measurement, such as OSLDs, instead of just indirect factors to monitor dose in the eye lens in radiological procedures.

Radiation Exposition of preparations of radiopharmaceuticals in routinely use, measured with optical-stimulated luminescence (OSL) dosimeters

Because of the new regulation of the radiation protection in Germany in 2018 (Strahlenschutzverordnung) it was meaningful to calculate an overview of the radiation exposition of the personal in the radiopharmaceutical "Hotlab". The regulation demands that the radiation exposition must be minimized, documented and reduced to an optimized level. In the Klinik und Poliklinik für Nuklearmedizin at the University Hospital of Dresden measurements were done with optical-stimulated luminescence (OSL) dosimeters. Light protected OSL dosimeters were positioned on the fingertips (thumb, forefinger and middle finger) of both hands and on the forehead. Before use the OSL dosimeters were calibrated. The exposition of the hands was measured at three different days in the preparation lab: 99mTc preparation in the daily routine, syringes application for radiosynoviorthesis (RSO) and 90Y Sirtex particles and for preparation of 177Lu and 68Ga radiopharmaceuticals. A relatively high exposition was seen after 99mTc preparations because of the quantity of preparations and syringes. Handling of syringes for RSO lead to an likewise raised exposition. The radiation exposition at preparation of 177Lu and 68Ga radiopharma-ceuticals depends on handling and use of modules. The exposition of the eye lenses was 0.02 mGy orlower and therefore not critical. But an appropriate radiation protection is necessary and a requirement for the most slightly radiation exposition. An optimized number of personal is necessary for preparation of radiopharmaceuticals in a "Hotlab" in nuclear medical facility. Therefore, the individual radiation exposition will be limited.

Evaluation of scattered radiation from fluoroscopy using small OSL dosimeters.

Recently, there has been a significant amount of interest in studying the importance of radiation doses to the eye lens during endoscopic retrograde cholangiopancreatography (ERCP). A study that focused on measuring the scattered radiation using an ionization chamber survey meter reported that a lead curtain was useful in reducing the scattered radiation. The over-couch X-ray tube system tends to deliver higher doses to the head and neck of the staff involved in the procedure than the under-couch X-ray tube position. In this study, a small optically stimulated luminescence (OSL) dosimeter called the nanoDot was used to evaluate and measure the amount of radiation; this dosimeter was developed by Landauer Ltd. and was specifically designed for point measurements. There are numerous studies that have reported the usefulness of personal OSL dosimeters other than the nanoDot to measure scattered radiation. Here, we evaluated the amount of scattered radiation, along with the degree of reduction achieved with the use of a protective curtain, while employing a personal OSL dosimeter and nanoDot. When the scattered radiation dose was measured using the nanoDot, the maximum recorded value without a protective curtain was 0.363mGy and that with a protective curtain was 0.026mGy, both at the height of 100cm. The maximum reduction rate of scattered radiation while using a protective curtain was approximately 93% and 97% at 100cm and 150cm, respectively. The measured values recorded using both personal OSL dosimeters and nanoDot machine were strongly correlated.

Feasibility of Metal Testicle Shield By 3D Printing for CT Image-Based Treatment Planning

This study aims to evaluate the feasibility of metal testicle shield for 3D CT image-based treatment planning using 3D dose calculation algorithm. The testicle shield was designed in the shape of box to minimize scatter radiation to the testicles and to be available in prone position. The testicle shield have two parts; cover and case. The dimension of case was 9.5 cm (length) × 7.5 cm (width) × 5.5 cm (height) with 2.0 cm thickness. The cover has 9.5 cm (length) × 9 cm (width) with 2.0 cm thickness. The one side of case was open sector to cover the scrotum of patient. A thin layer of silicon coating on inner surface was attached to allow comfortable attachment to the patient and to shield back-scattered electron dose from the shield. Each part was fabricated using 3D printer. The material of testicle shield was titanium which is allowed for the dose calculation using Acuros XB. To avoid metal artifact for CT image, the replica of the metal shield (dummy) was fabricated with a plastic using 3D printer for CT-sim. The rectal cancer patient underwent CT scan with dummy shield. In the treatment planning system (TPS), the dummy testicle shield was contoured, and material of dummy was assigned to titanium. Three-field box (two wedged opposing beams and 3rd beam at 90° with 15 MV) technique was used for treatment plans. The dose calculation was performed using Acuros XB and AAA. The dose distributions were also calculated in EGS4/DOSXYZnrc Monte Carlo (MC) for comparison. Optically stimulated luminescent dosimeter (OSLD) was used to measure dose of inside and outside shield for evaluating shield effect. We compared between OSLD measurement, MC simulation and TPS dose calculation. The inside dose of testicle shield was reduced to 48.1% inside dose by titanium testicle shield. The dose distribution of Acuros XB have good agreement with that of MC. The average difference was 2.1% in dose voxels containing greater than 50% the normalized dose. In contrast, the average difference between AAA and MC was 23.1%. For point dose inside the shield, MC calculation agreed with the OSLD measurements within 3.0%. The difference of MC and AAA are 10% and 30% for outside and inside surface of testicle shield, respectively. The radiation shielding ability of titanium was approximately 10% lower than that of lead. When the material of testicle shield is titanium and the plastic dummy is used for CT-sim, the dose distribution can be calculated using Acuros XB accurately in TPS.

Estimation of organ absorbed dose in pediatric chest X-ray examination: A phantom study

Children have a greater risk of developing lifetime cancer and other biological effects from ionizing radiation exposure than adults. The aim of this study was to measure the absorbed dose received by lungs and heart in pediatric chest X-ray examination using nanoDot optically stimulated luminescent dosimeter (OSLD). The X-ray system, Siemens Multix Top was used. A pediatric phantom developed by using beeswax and polyurethane foam was exposed at 50 kVp, 52 kVp, 55 kVp, 57 kVp and 60 kVp, with fixed tube current-exposure time (3 mAs), which is normally used in pediatric clinical chest X-ray examinations. The nanoDot OSLDs were placed in different parts in the thorax of the phantom according to the position of organs in the chest area, which are lungs and heart. For lungs, absorbed dose measurement nanoDot OSLDs were placed in the apex and base at three different depths. The phantom was exposed three times for each kVp value, and the absorbed doses were measured in mGy. The findings show that the measured absorbed dose to the heart increased with the increase in kVp. Overall, a 22% increase in absorbed dose to heart and a 29% increase in lungs with the increase in kVp was recorded. In addition, absorbed dose to the base of left and right lungs was recorded higher up to 9% as compared to the apex of lungs. In conclusion, the absorbed dosage increases with exposure, while the absorbed dose decreases with depth. It is necessary for the radiographer to select an appropriate exposure setting based on the physical characteristics of the pediatric patient.

Fabrication of anthropomorphic thyroid-neck phantom for dosimetry study in nuclear medicine.

The aim of this study was to fabricate an anthropomorphic thyroid-neck phantom for dosimetry study in nuclear medicine. The main structures of the anthropomorphic phantom comprise of neck, thyroid, trachea, oesophagus, cervical bone and spinal canal. Several slots for Optically Stimulated Luminescent Dosimeter (OSLD) for each organ was also fabricated to measure the absorbed dose received by thyroid and other organs at risk. The phantom was made from paraffin wax and sodium chloride (NaCl) compounds. The fabricated anthropomorphic phantom was then tested by administrating 99mTc with an activity of 0.3 mCi and 2.0 mCi in thyroid and neck phantoms respectively. The phantom was scanned for 30 min with diagnostic thyroid imaging of SPECT to observe the distribution of 99mTc. A comparison analysis between mass attenuation coefficient of samples and mass attenuation coefficient of human tissue obtained from ICRU report-44 was performed to validate the mass attenuation coefficient of samples obtained in this study. Relative percentage differences of mass attenuation coefficients of samples obtained from experimental and XCOM stimulation values were evaluated respectively. The absorbed dose to thyroid and other organs at risk was evaluated from OSLDs at 6 h (first half life), 12 h (second half life) and 24 h (fourth half-life) after the injection of 99mTc.

Effectiveness of Al2O3:C OSL dosimeter towards entrance surface dose measurement in common X-ray diagnostics

We report the successful use of nanoDots Optically Stimulated Luminescence Dosimeters (OSLDs) for the determination of the entrance surface dose (ESD) in common X-ray diagnostics. ESD evaluation is made on six radiographic projections including abdomen (AP and LAT), chest (AP and PA), skull (AP), and thoracic spine (AP). Indirect and direct ESD measurements have been performed with and without whole-body anthropomorphic phantom using GE radiography system installed at the Diagnostic Imaging Laboratory, Universiti Kebangsaan Malaysia (UKM), wherein the International Atomic Energy Agency protocol (IAEA TRS-457) has been followed. The CALDose_X 5.0 software is used to calculate ESDs in these projections. The mean ESDs obtained with indirect measurements for AP abdomen, LAT abdomen, AP chest, PA chest, AP thoracic spine, and AP skull projections are 4.8, 8.3, 0.7, 0.2, 7.2, and 3.7 mGy respectively, and with direct measurements, the respective mean ESDs are 4.3, 8.3, 0.7, 0.3, 6.8, and 2.8 mGy. The values obtained by CALDose_X calculations are 8.3, NA, 1.1, 0.7, 8.8, and 4.5 mGy, respectively. Significant variations ranging from 18% to 59% are observed between measured and calculated ESDs, which are attributed to the difference in phantom size and field size. The overall uncertainty for direct measurements has a maximum of ±0.86 mGy compared to ±0.47 mGy for indirect measurement. Measured ESDs are within the IAEA and European Commission (EC) DRLs range, while calculated ESDs are slightly above the measured values. It is concluded that the use of nanoDots OSLD is beneficial for ESD measurement in routine X-ray examinations.

Dosimetric impact of placement errors in optically stimulated luminescent in vivo dosimetry in radiotherapy.

IntroductionStudies have suggested that optically stimulated luminescent dosimeters (OSLDs) can be used for in vivo dosimetry of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT). Clinical uncertainties such as placement error have not been thoroughly investigated. The purpose of this work was to measure OSLD placement error in a clinical sample and analyze its dosimetric impact.Methods and materialsThe analysis consisted of three parts: first, quantification of placement error in a clinical sample of 128 patients yielding 293 cone-beam CT (CBCT) with visible OSLDs registered to the treatment plan; Second, correlation of placement error and clinical OSLD measurements; third, simulation of dosimeter placement in the treatment plan and correlation of recalculated dose with placement error.ResultsIn the first analysis, average placement error was 9.7 ± 9.5 mm. In the second analysis, placement error and measured-to-planned dose agreement yielded no correlation (R2 = 0.02) for a subsample of 77 CBCTs of 55 head-and-neck patients. Average placement error was 7.0 ± 6.0 mm. Several factors, including image-guided shifts, introduced uncharacterized uncertainty to the measured-to-planned dose agreement. The third analysis isolated placement error from these other effects. Average dosimetric error was −2.4 ± 19.3%. Simulated dosimetric impact was weakly correlated with placement error (R2 = 0.39). Removing outliers reduced the average dosimetric error to −2.1 ± 10.9%, marginally improving the correlation (R2 = 0.44).ConclusionPlacement error can substantially impact measured-to-planned dose agreement of OSLDs in high gradient regions, demonstrating the criticality of accurate dosimeter placement for IMRT and VMAT treatments.

Response of a nanoDot OSLD system in megavoltage photon beams

PurposeThe aim of this study was to investigate the response of a nanoDot optically stimulated luminescence dosimeter (OSLD) system in megavoltage photon beams. MethodsThe nanoDot response was compared with the ionization chamber measurements for 4–18-MV photons in a plastic water phantom. The response was also calculated by the Monte Carlo method. In addition, the perturbation correction factor, PQ, in the nanoDot cavity was calculated according to the Burlin’s cavity theory. The angular dependence of the nanoDot was evaluated using a spherical phantom. ResultsThe calculated and measured nanoDot responses at a 10-cm depth and 10 × 10-cm2 field were in agreement within 1% for 4–18-MV. The response increased by 3% at a 20 × 20-cm2 field for the lower energy of 4 MV; however, it was constant within ±1% for 6–18 MV. The response was in a range from 1.0 to 0.99 for mean photon energy of more than 1.0 MeV but it increased with less than the 1.0 MeV. PQ for the nanoDot cavity was approximately constant at 0.96–0.97 for greater than and equal to 10 MV. The angular dependence decreased by 5% and 3% for 6 and 15 MV, respectively. ConclusionsThe nanoDot was energy-independent in megavoltage photon beams.

A skin dose prediction model based on in vivo dosimetry and ultrasound skin bridge measurements during intraoperative breast radiation therapy

PurposeUsing in vivo measurements from optically stimulated luminescence dosimeters (OSLDs) to develop and validate a prediction model for estimating the skin dose received by patients undergoing breast intraoperative radiation therapy (IORT). Methods and MaterialsIORT was performed using INTRABEAM-600 with spherical applicators placed in the lumpectomy cavity. Ultrasound skin bridge measurements were used to determine the applicator-to-skin distance, with OSLDs placed to measure the skin surface dose at the corresponding points. The OSLD response was calibrated for the 50 kVp INTRABEAM-600 output. Models were fit to describe the dose fall-off with increasing applicator-to-skin distance and the best fitting model was chosen for estimating skin dose. ResultsTwenty four patients with 25 lumpectomy cavities were included, and the average skin dose recorded was 1.18 Gy ± 0.88 Gy, ranging from 0.17 Gy to 4.77 Gy, with an average applicator-to-skin distance of 19.9 mm ± 5.1 mm. An exponential-plateau model was found to best describe the dose fall-off with a root-mean-square error of 0.73. This model was then validated prospectively using skin dose measurements from five consecutive patients. Validation measurements were well within the 95% prediction limits of the model, with a root-mean-square error of 0.52, showing that the prediction model accurately estimates skin dose using ultrasound skin bridge measurements. ConclusionsThis prediction model constitutes a useful tool for estimating the skin dose received during breast lumpectomy IORT. The model and accompanying 95% confidence intervals can be used to establish a minimum allowable skin bridge distance, effectively limiting the maximum allowable skin dose.

Occupational radiation dose during fluoroscopy guided interventional procedures at Institut Kanser Negara

Fluoroscopy-guided interventional (FGI) tends to involve long-term procedures that increase the fluoroscopy time and the dose area product (DAP). Therefore, radiation protection is a major concern for interventional radiology staff. This study signifies the occupational and the radiation doses for interventional radiology staff, in particular, non-physician in order to clarify the current dose level for radiographers and nurses. The occupational doses were compared among interventional radiology staff in Institut Kanser Negara (IKN), Putrajaya, Malaysia where 230 patients underwent FGI procedures were observed in one-year. The occupational doses of interventional radiologist (IR), medical officer (MO), radiographer and nurse were recorded using two optically stimulated luminescence dosimeter (OSLD), one worn over and one under their protective aprons. The occupational dose (effective dose) indicated that the IR, MO, radiographer and nurse with double OSLDs were 9.82, 7.91, 6.42 and 6.02 mSv, respectively. The effective dose of IR, MO, radiographer and nurse were 7.63, 7.91, 6.42, 5.66 mSv, respectively using a single OSLD. It has shown a statistically significant difference in the effective dose of double worn OSLDs and one OSLD of (p < 0.05) for interventional radiology staff. In both methods, IR > MO > radiographer > nurse was the highest effective dose in the interventional radiology staff. However, the occupational dose of single OSLD was found to be lower than double OSLDs. It is highly recommended that interventional radiology staff to use double OSLDs during the FGI procedures in order to determine the occupational dose accurately.

Characterization of a non-contact imaging scintillator-based dosimetry system for total skin electron therapy

Surface dosimetry is required for ensuring effective administration of total skin electron therapy (TSET); however, its use is often reduced due to the time consuming and complex nature of acquisition. A new surface dose imaging technique was characterized in this study and found to provide accurate, rapid and remote measurement of surface doses without the need for post-exposure processing.Disc-shaped plastic scintillators (1 mm thick × 15 mm ) were chosen as optimal-sized samples and designed to attach to a flat-faced phantom for irradiation using electron beams. Scintillator dosimeter response to radiation damage, dose rate, and temperature were studied. The effect of varying scintillator diameter and thickness on light output was evaluated. Furthermore, the scintillator emission spectra and impact of dosimeter thickness on surface dose were also quantified. Since the scintillators were custom-machined, dosimeter-to-dosimeter variation was tested. Scintillator surface dose measurements were compared to those obtained by optically stimulated luminescence dosimeters (OSLD).Light output from scintillator dosimeters evaluated in this study was insensitive to radiation damage, temperature, and dose rate. Maximum wavelength of emission was found to be 422 nm. Dose reported by scintillators was linearly related to that from OSLDs. Build-up from placement of scintillators and OSLDs had a similar effect on surface dose (4.9% increase). Variation among scintillator dosimeters was found to be 0.3 ± 0.2%. Scintillator light output increased linearly with dosimeter thickness (~1.9 × /mm). All dosimeter diameters tested were able to accurately measure surface dose.Scintillator dosimeters can potentially improve surface dosimetry-associated workflow for TSET in the radiation oncology clinic. Since scintillator data output can be automatically recorded to a patient medical record, the chances of human error in reading out and recording surface dose are minimized.