Routine Dosimeter Research Articles

Dose measurement using a leuco crystal violet film system with high sensitivity for food irradiation applications

Radiation dosimetry is of paramount importance to achieve the desired objectives in radiation processing of food. The low dose range of 0.1–1 kGy is very important for selected food irradiation applications. Inexpensive and easy to handle routine dosimeters that operate in this range are thus highly desirable. To this end, a leuco crystal violet dye based radiochromic film was developed incorporating 2,2,2-trichloroethanol as sensitizer. This system exhibits a linear dynamic response in the 0.1–1 kGy dose range. The sensitivity of the films to spectroscopic readout was found to be ∼146 kGy−1 mm−1 which is higher than that of any previously reported leuco crystal violet film dosimeter. The limit of detection, limit of quantification, and prediction error were determined to be 0.050 kGy, 0.077 kGy, and ±0.47%, respectively. The response of the film was also assessed using two image analysis methods – the conventional single channel approach and a novel double channel approach. A prediction error of less than ±1.0% was obtained for the latter. The results demonstrate for the first time that the dose response of leuco crystal violet based systems can be studied by inexpensive desktop scanner based colour analysis.

Dose rate mapping of an industrial 60Co irradiator using an online photodiode-based dosimetry system

In this work, a housemade dosimetry system based on a thin photodiode is applied for online mapping of dose rates, between 2.6 and 37.7 Gy/h, delivered by a Panoramic 60Co industrial facility. The operational principle of the dosimeter relies on the real-time acquisition of the induced currents from the irradiated diode operating in the short-circuit mode without externally applied voltage. The radial mapping of the radiation field is performed by rotating the diode around the central axis of the panoramic irradiator, covering 360° at intervals of 18°. The results are benchmarked with alanine dosimeters, Monte Carlo simulations, and reference dose rates retrieved from the facility calibration. The overall consistency of the whole data complies with the maximum response variation (8%, k = 2) recommended by the International Standard Protocols for routine dosimeters in radiation processing dosimetry. It reveals that the photodiode-dosimetry system is a reliable alternative to map dose rate fields and the effectiveness of Monte Carlo simulations as a predictive tool for dose rate measurements in an irradiator.

Assessment of Radiation Safety Training, Practices and Knowledge amongst Canadian Orthopaedic Resident Training Programs

Objective: There is ample literature demonstrating significant health risks associated with radiation exposure, yet there is no standardized radiation safety training for Canadian orthopaedic surgery residents. This is the first national survey investigating the prevalence of radiation safety training and radiation safety practices in Canadian orthopaedic residency programs. Methods: A nationaln online survey was distributed to orthopaedic residents currently enrolled in a Canadian program from all post-graduate (PGY) levels who were fluent in English or French with a medical doctorate or equivalent training. Fellows, international elective or observer ship students were excluded. Results: Overall response rate across Canada was 41% (n=116). Most respondents (94%, n=102) were concerned about the negative effects of radiation, yet only 11% (n=12) felt confident with their radiation safety knowledge. Of the residents who felt confident in their knowledge, only 42% (n=5) answered all three radiation safety screening questions correctly. Overall, 58% (n=66) of respondents had undergone some form of radiation safety training. Compliance with protective lead was high (92%, n=93) when available, but 82% (n=92) of respondents cited issues accessing properly fitting lead. Only 18% (n=20) of orthopaedic residents reported routinely wearing dosimeters. Conclusion: Limited access to properly fitting protective lead, poor radiation safety knowledge, and lack of routine radiation monitoring could be placing residents at risk for poor health outcomes in the future. These results provide impetus for orthopaedic residency programs across Canada to implement higher safety standards in the form of standardized radiation safety training, routine dosimeter use, improved lead availability, and continued abidance to radiation safety protocols.

Characterization of a thin photodiode as a routine dosimeter for low-dose radiation processing applications

The characterization of a dosimetry system based on a commercial PIN photodiode as a routine dosimeter in a 60Co industrial facility is reported. The main parameters of the dose rate response (repeatability, reproducibility, and angular dependence) and the dose response (dependence on both dose rate and accumulated dose) are investigated. The results obtained, within a dose rate range of 3.7–52.8 Gy/h and doses up to 200 Gy, fully adhere to the standard protocols established for radiation processing dosimetry. The diode performance as a routine dosimeter is validated by the good overall agreement with radiochromic films and alanine dosimetry.

Performance Characterization of Dosimeters Based on Radiation-Hard Silicon Diodes in Gamma Radiation Processing

The dosimetric response of silicon diodes produced with distinct engineering technologies, Magnetic Czochralski (MCz), and standard Float Zone (Fz), has been investigated, aiming at their use for online dosimeters in gamma radiation processing applications. The p+-n-n+ junction diodes, 300 µm thick with an active area of 25 mm2, are operated as online radiation dosimeters in the short-circuit current mode. In this case, the key dosimetric quantity is the dose rate, which is correlated with the output current from the diode subjected to radiation. Thus, the dose is obtained offline by the integration of the corresponding current signal. The irradiations are performed with an industrial Gammacell 60Co facility at 2.3–2.44 kGy/h covering doses up to 275 kGy. Under continuous irradiation, both diodes delivered current signals whose intensities decreased with accumulated doses. Mitigation of this decay has been accomplished by pre-irradiating the devices to 700 kGy. Polynomial functions best represent the dose responses for either pristine or preirradiated diodes. The relevant dosimetric parameters as response stability, charge sensitivity, and repeatability of current signals (<5%) reveal the better performance of the MCz diode. It is important to note that the whole dataset fully complies with the international standard protocols for routine dosimeters in radiation processing dosimetry. Regarding radiation damage, which in unbiased diodes manifests primarily in the decay of current sensitivity, the results also showed greater tolerance of the MCz diode. Based on these studies, large availability, and better cost-effectiveness, it is possible to endorse the potential use of MCz devices as online routine dosimeters in radiation processing applications. However, the data reproducibility with the accumulated dose, the dose lifespan, and the effect of the irradiation conditions (e.g., temperature, relative humidity, and dose fractionating) remain to be investigated. Works in this direction are currently in progress.

Development of fluorescein-based dosimeter for radiation processing applications

Dosimetry forms an inseparable part of radiation processing. Many dosimeters are available to cover wide range of doses used in radiation processing. These include the Fricke, ceric-cerous, alanine ESR Alanine (Electron Spin Resonance Technique), dichromate, and radiochromic films. Low-dose radiation processing applications (<2 kGy) such as insect disinfestation, shelf-life extension, and sprout inhibition use imported dosimeters. At present, radiochromic films/waveguides are used for low-dose applications; however, the dosimeters are costly and subject to sanctions and supply restrictions from country of origin. The present work discusses the development of system that can be used as a routine dosimeter for radiation processing facilities in the dose range of 200–2500 Gy. Iodine is generated by the action of radiolysis products of water on iodide and iodate present. Generated iodine halogenates fluorescein to erythrosine with the help of bicarbonate. Increase in absorbance due to the formation of erythrosine can be related to the absorbed dose and used in routine dosimetric applications. As the change is radiochromic, it advantageously provides a visual indication of dose received.

Intercomparison of Gamma Cell 220 Irradiator Facilities and Dr. Mirzan T Razzak Gamma Irradiators Using Harwell Dosimeters

The gamma irradiator is a multi-purpose facility that possibly used to preserve food, sterilize medical equipment, and conduct genetic engineering and polymerization processes, during which the absorbed dose of the product is critical. The standardization of product quality assurance was regulated by the IAEA Technical Document Number 409 considering Dosimetry for Food Irradiation and ISO 14470 and 11137-3 on Food Irradiation, as well as the Guidance on Dosimetric Aspects of Development, Validation, and Routine Control, respectively. The absorbed dose was influenced by the movement of the product to the source, its position, the amount of radioactive activity in the facility, and the dose rate in the irradiation room. The dosimeter performance test and quality assurance of the system were conducted using the Facility Intercomparison Technique which tested the dosimeter (measuring instrument) at 2 different facilities to determine the performance of the measuring instrument.. In this study, 2 irradiation facilities were tested using a Harwell routine dosimeter in the dose range of 1 kGy to 30 kGy and 20 dose points. The results showed that the highest deviation reached 19% and 21% at the Gamma Cell 220 and the Dr. Mirzan T Razzak Gamma irradiator facilities. This elevated the performance of the dosimeters to determine the precision accuracy of the dose-measuring instrument.

Poly(vinyl alcohol)/heteropolyacid nanocomposites as new materials for radiochromic dosimetry in radiation processing

AbstractRadiochromic films composed of polymer matrices and organic dyes are widely used for routine dosimetry purposes in operation of various radiation facilities—gamma and X‐ray‐irradiation, electron accelerators, and so on. However, the sensitivity of these films rapidly decreases at doses exceeding 30–50 kGy due to a saturation of their optical response, making them unsuitable for accurate dosimetry in radiation processing of polymers and composites where doses up to 200 kGy are typically employed. To overcome this limitation, the use of inorganic substances as the coloring agents of polymer‐based radiochromic films was proposed in this paper, specifically, heteropolyacidacid H3PW12O40 (tungstophosphoric acid) in the matrix of poly(vinyl alcohol) (PVA). Nanocomposite PVA/H3PW12O40 films were prepared by solution casting and their optical responses toward 60Co gamma radiation and beams of 6 MeV electrons for a dose range of 10–200 kGy were investigated. It was established that upon exposure to gamma rays and electron beams, the films turn blue and a broad absorption band at 750 nm appears in their spectra. Importantly, the radiation‐induced optical absorption increases in a linear fashion up to the dose of 150 kGy and only slightly deviates from linearity at 200 kGy. Moreover, it was found that the PVA/H3PW12O40 films have a long shelf life, are dose‐rate independent within a wide range, and color‐stable after irradiation. All these features make the nanocomposite PVA/H3PW12O40 films promising for use as routine dosimeters and dose labels in a much wider range of high doses as compared to radiochromic films based on organic dyes.

Evaluation of TL and OSL responses of CaF2:Tm for electron beam processing dosimetry

The thermoluminescence (TL) and infrared stimulated luminescence (IRSL) responses of in-house produced CaF2:Tm dosimeters are investigated in this work, envisaging their application in electron beam (EB) radiation processing. The irradiations were performed at an industrial EB accelerator (1.5 MeV) covering a dose rate range of 2–8 kGy/s and dose up to 10 kGy. In general, the TL glow curves display four peaks, termed as peaks 2, 3, 4, and 5, corresponding to temperatures at ~150, 200, 240, and 300 °C, respectively. The intensity of the low-temperature peaks (2 and 3) grows with the dose, while the others remain constant (saturated). Nevertheless, an evident dose effect on the glow curves manifests in decreased peak3/peak2 ratio with increasing doses.The CW-IRSL curves exhibit similar patterns with an initial signal increase, followed by an exponential decay. Instead of the normal monotonic decays, these peak-shaped curves might be due to the charge capture competition between empty shallow traps and recombination centers. Both TL and IRSL intensities increase linearly with doses up to 6 kGy, and for higher doses, they become sub-linear with a saturation trend around 10 kGy. Another common feature of TL/IRSL response is its dose rate dependence, being more sensitive at higher dose rates. Despite being dose-rate dependent, the CaF2:Tm dosimeters might be suitable for EB processing dosimetry. However, for their use as routine dosimeters, relevant dosimetric characteristics, such as fading and response reproducibility, have to be investigated. Work in this direction is underway.

Comparative study of two azo dyes using Triphenyl-Tetrazolium Chloride (TTC) on gamma irradiation induced film dosimeter

The change in optical properties on exposure to radiation has been studied for polyvinyl alcohol, 2, 3, 5-triphenyl tetrazolium chloride salt dyed films. The comparative results between the two different dyes namely methyl orange and di-methyl yellow have been studied for the change in color for the application of dosimeter. The film samples exposed at different doses from 0 to 30 kGy by exposing gamma rays using 60Cobalt gamma source at 0.95 kGy/hour. The visual color change from yellow to red for films containing methyl orange dye whereas change in color from greenish-yellow to red for films containing di-methyl yellow dye have been observed after gamma irradiation and confirmed using various characterization techniques. Colorimetric analysis shows differentiation between the visual color change by comparing colorimetric coordinates like L* a* and b* to each other. Whereas the change in absorption band by UV–Visible spectrophotometer shows an increase in the absorption with an increase in the doses. The FT-IR analysis reveals the change in structural groups. The reproducibility and post-stability studies established and further considered to be used as a routine dosimeter.

Definite comparison of resazurin film with FWT film in monitoring the absorbed irradiation dose and it is possibility of using as a label- dosimeter

A comparison study between the PH indicator Resazurin, (hydroxy phenoxazin) dye incorporated in poly vinyl alcohol with the most famous routine dosimeter used in commercial irradiation processes, FWT-60-00, (hexa hydroxyl ethyl pararosaniline nitrile) in determining the absorbed dose was carried out to achieve a new dosimeter simulate accuracy of the FWT film used in irradiation processes up to 5 kGy. Many characteristics for the new film was studied such as the response with and without chloral hydrate as an additive substance, the dose rate effect, the effect of humidity during irradiation, pre and post irradiation stability in different environments, the uncertainty measurements and cost price were studied. On the other hand, the film has a label characters beyond 5kGy, ascertained through color change from deep violet into orange color upon irradiation till a complete fading for orange color at approximately 60 kGy. The new prepared resazurin film may be nominate to be excellent routine dosimeter beside its labelling characterization.

Dosimetric characterization of LiMgPO4:Tb,B phosphor for its application in food irradiation

Optically stimulated luminescence (OSL) intensity versus dose response of indigenously developed LiMgPO4:Tb,B (LMP) disks is linear in the range of 1 mGy–1 kGy. Currently, no other synthetic OSL phosphor is available, which covers such a large dose range. In order to assess the feasibility of using the phosphor in low-dose food irradiation dosimetry (up to 1 kGy), dosimetric characterization of LMP-based OSL dosimeter was carried out under both, gamma and electron beam irradiation. The doses estimated by LMP and routine dosimeters match well in the field trials. Hence, this phosphor has the potential to be used in phytosanitary application using radiation, where delivered doses are of the order of 0.01–1 kGy. Practical applications Food irradiation dosimetry, in India, is being carried out using chemical dosimeters such as Fricke, Ceric-cerous sulphate, and Alanine-electron paramagnetic resonance. The former two are liquid dosimeters kept in glass tubes and therefore need to be handled delicately during irradiation. The complex chemical preparation, sensitive to environmental conditions (temperature, humidity, etc.) and temperature changes, sensitive to UV radiation and the high sensitivity to impurities make these dosimetry systems inconvenient for routine applications. The OSL intensity versus dose response of indigenously developed LiMgPO4:Tb,B (LMP) has been observed to be linear up to 1 kGy. Apart from good dosimetric qualities, other qualities of the dosimeter system are quick readout, ease of handling, automated readout mechanisms, and integrity in harsh environments. The above-discussed attributes make LMP-based OSL dosimeter a potential candidate to carry out dosimetry during phytosanitary application of radiation in low-dose range (0.01–1 kGy). This range includes irradiation of mangoes, onions, potatoes, etc.

Dosimetric characterization of novel polycarbonate/porphyrin film dosimeters for high dose dosimetry: study on complexation effect

Abstract Two novel radiochromic films with 20 μm thickness were made from casting of solutions of polycarbonate (PC) containing 0.5 wt.% tetra phenyl porphyrin (TPPH2) and 5,10,15,20-tetraphenyl-21H,23H-porphine iron(III) chloride (Fe-TPP). Dosimetric characterization of the films as routine dosimeters were studied by spectrophotometric method. On subjecting TPPH2/PC and Fe-TPP/PC film dosimeters to gamma radiation, radiolytic bleaching of films was observed. The effects of metal-complexation on the radiation response of the film dosimeters were studied under 60Co γ-rays exposure in dose range of 0–100 kGy. The results were also compared with the PC/TPPF20 (PC/tetrakis (pentafluorophenyl) porphyrin) dosimeter to evaluate the substituent effect (role of fluorine groups). Experimental parameters including humidity, temperature and pre-irradiation (shelf-life) and post-irradiation storage in dark and in indirect sunlight were examined. The maximum absorbance of Soret band of dyes had meaningful shifts and reduction which arose from complexation and substituents. The dyed films characteristics were found to be stable enough in media with high degrees of temperature and humidity. The results indicate that the radiation-induced decoloration of TPPH2/PC and Fe-TPP/PC films can be reliably tuned and used in high dose dosimetry.

Fabrication of a flexible polycarbonate/porphyrin film dosimeter for high dose dosimetry

Abstract Dyed polycarbonate (PC) Radiochromic films with 20 μm thickness were prepared by casting of organic solution of PC containing 0.5 wt.% tetrakis (pentafluorophenyl) porphyrin (TPPF20) on a glass petri dish. Characterization of the film as a routine dosimeter was studied. On subjecting PC/TPPF20 film dosimeter to gamma radiation, a gradual decrease in the color of films was observed. The sensitivity of these films and the linearity of dose-response curves were studied under 60Co γ-rays expose in dose range of 0–100 kGy. The results were compared with the commercial and non-commercial dosimeters. Experimental parameters including humidity, temperature and pre-irradiation (shelf-life) and post-irradiation storage in dark and in indirect sunlight were examined. The maximum absorbance of soret band of TPPF20 had a bathochromic shift and appeared at 414 nm which remained intact in the investigated dose range. The dyed films characteristics were found to be stable enough in media with high degrees of temperature and humidity. The results indicate that radiation induced decoloration of PC/TPPF20 films can be reliably used in high dose dosimetry.

A methodology to split the total cumulative Hp(10) dose into the Hp(10)i doses received during various procedures performed by interventional cardiologist

The methodology describing how to split the cumulative Hp(10) dose of interventional cardiologists into Hp(10)i doses received during procedures of various types based on procedure-specific ELDO coefficients and Hp(3) doses per procedure is presented. The appropriate equations for Hp(10)i (Hp(10) for procedure type i), depending on the number of various procedure types (i = 1 … 4) performed by a particular physician, are derived. The methodology can be applied to whole-body doses measured on the lead apron and therefore can be used for optimisation of work practices in those catheterisation labs where routine dosimeter is worn above the apron.

The effectiveness of lead glasses in reducing the doses to eye lenses during cardiac implantation procedures performed using x-ray tubes above the patient table

The dose reduction factors (DRF) for different types of lead glasses and C-arm units with x-ray tubes placed above the patient table were calculated from the results of measurements by loose thermoluminescent dosimeters (TLDs) and EYE-D dosimeters using a Rando phantom. The DRF values were analysed for different positions of routine dosimeters worn outside lead eyewear and confronted with DRFs calculated as the ratio of the dose equivalent to the eye measured with and without the eyewear. Moreover, for eye lens dosimeters designed to be worn behind lead glasses, multiplicative factors for various positions of dosimeter were derived in order to account for the differences between the doses measured on the inner side of the glasses and the dose equivalent to the eye lens.The DRFs calculated for the position of a routine dosimeter worn outside lead glasses on the band near the left eye lens are 5.6 and 5.7 for goggles and metallic glasses, respectively, while the DRFs calculated as the ratio of doses to the eyes measured with and without the eyewear are 10.2 and 9.9, respectively.Therefore, for dosimeters routinely used outside lead eyewear, the DRF calculated for the position of the dosimeter should be used. Otherwise, we can anticipate an almost two-fold underestimation of the doses. When the dosimeter is worn behind lead glasses, up to two-fold differences between the dose equivalent to the eye lens and the dose measured at the inner side of the glasses were observed depending on the dosimeter position.

Using polycarbonate dyed with dansyl chloride for dosimetry in radiation processing

Abstract Preparation and characteristics evaluation of the polycarbonate films 20 μm in thickness containing Dansyl chloride as a routine dosimeter in radiation processing facilities were studied. The sensitivity of these films and the linearity of dose-response curves were investigated under 60Co γ-rays in a dose range of 0–100 kGy, and the obtained results were compared with the commercial CTA and FWT film dosimeters. The results show that the maximum absorbance appeared at 370 nm in all the investigated dose range. The dyed films were found to be stable enough in mediums with high degrees of humidity and temperature, to be reliably used in radio-applications. The effects of pre-irradiation (shelf-life) and post-irradiation storage in dark and in indirect sunlight were also discussed. The films which were made displayed stable characteristics when stored in dark, within 1% at 25 ℃, 3 months after irradiation.

Calibrations of Red Perspex PMMA dosimeter in terms of absorbed dose to water for routine dosimetry at CDTN gamma irradiation laboratory

This paper presents results of polymethylmethacrylate (PMMA) dosimeters calibrations that are used as routine dosimeters in CDTN Gamma Irradiation Laboratory. The study was carried out within the framework of the Facility Quality Assurance Program with the purpose of determining the accuracy of the dosimeters used. The dosimeter irradiations were made in a Gamma Irradiator at Nuclear Technology Development Center (CDTN), an R&D Institute connected to the National Nuclear Energy Commission (CNEN), Brazil. The value for estimate of the expanded uncertainty achieved is typical of a routine dosimetry system.

Effect of gamma-irradiation on the colorimetric properties of epoxy-resin films: Potential use in dosimetric application

The present paper reports the results of the colorimetric study of gamma-irradiated epoxy-resin films. Epoxy-resin samples were irradiated by gamma-rays with doses varying from 1 to 50kGy. Color changes of epoxy-resin were observed and studied by the measurements of the variation of the L∗, a∗, b∗ as function of dose and post-irradiation time. Where L∗ is a measure of the magnitude of brightness from black to white, parameter a∗ describe the relative amounts of red and green, and parameter b∗ describes the relative amounts of yellow and blue color. Color changes (ΔE) were also calculated. They indicated a marked dependence of the absorbed doses showing the optical activation of the color centers. It was found that color changes (ΔE) due to absorbed dose increase from 6 to 50. Color change showed a low variability which did not exceed 3% for the measurements carried out between 1 and 72h. The obtained results revealed that epoxy-resin films can be used as a new routine dosimeter or irradiation indicator in dose range 1–50kGy.

An Approach for Using of Poly Glycolic Acid (PGA) in Reference Standard Dosimetry: PGA/ESR Dosimetry System Response Curve and Post Irradiation Stability

Reference Standard Dosimeters are used to calibrate radiation environments and routine dosimeters. It can also be used in routine dosimetry applications for radiation processing where higher quality dosimetry measurements are required. Electron Spin Resonance (ESR) is a well-established Reference Standard Dosimetry system in industrial applications of ionising radiation, and its use is also proposed in radiation therapy and accident dosimetry. In the present experimental work, PGA solid state dosimeter (SSD) has been investigated using ESR spectroscopy to study the gamma radiation response of this material and to evaluate its dosimetric characteristics: dose response, room temperature fading, heat treatment effect during post-irradiation storage. Results obtained up to now confirm that PGA seems to be suitable material for ESR dosimetry applications.