|Year : 2017 | Volume
| Issue : 1 | Page : 118-121
Evaluation of the effect of temperature variation on response of PRESAGE® dosimeter
Bagher Farhood1, Davood Khezerloo1, Tohid Morteza Zadeh1, Hassan Ali Nedaie1, Daryoosh Hamrahi2, Najimeh Khezerloo3
1 Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
2 Sadra Radiotherapy Center, Qom, Iran
3 Department of Radiology, Imam Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
|Date of Web Publication||16-May-2017|
Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran
Source of Support: None, Conflict of Interest: None
Introduction: Many factors, such as PRESAGE ® composition, dose rate, energy, and type of radiation, temperature, etc., may effect on PRESAGE ® dosimeter response. The aim of this study was investigating the effect of temperature variation on response of PRESAGE ® solid dosimeter.
Materials and Methods: In this study, a PRESAGE ® solid detector was fabricated. Ninety-four percent weight polyurethane, 5% weight carbon tetrachloride, and 1% weight leucomalachite green were used. Radiological and physical characteristics of PRESAGEs ®, such as mass density, electron density, and effective number atomic were obtained and compared with water. Response of PRESAGE ® dosimeter in temperatures −4, 10, 25, 35, 45, 55, 65, 75, 85, and 90°C was evaluated. In addition, the absorption peak at various temperatures was investigated.
Results: The results showed that the absorption peak at different temperatures was in the range of 630–635 nm. For temperatures below 75°C, the results indicated that temperature variation has no effect on the response of PRESAGE ® dosimeter whereas at the temperatures >75°C, temperature variation has an effect on PRESAGE ® dosimeter response.
Conclusion: The finding showed that temperature changes have not impact on the absorption peak. In addition, the results related to the effect of temperature variation on the response of PRESAGE ® dosimeter showed that in the range of clinical applications (temperatures below 75°C), temperature variation has no effect on PRESAGE ® dosimeter response.
Keywords: Dosimetry, PRESAGE®, radiation, temperature, three-dimensional dosimetry
|How to cite this article:|
Farhood B, Khezerloo D, Zadeh TM, Nedaie HA, Hamrahi D, Khezerloo N. Evaluation of the effect of temperature variation on response of PRESAGE® dosimeter. J Can Res Ther 2017;13:118-21
|How to cite this URL:|
Farhood B, Khezerloo D, Zadeh TM, Nedaie HA, Hamrahi D, Khezerloo N. Evaluation of the effect of temperature variation on response of PRESAGE® dosimeter. J Can Res Ther [serial online] 2017 [cited 2019 Nov 21];13:118-21. Available from: http://www.cancerjournal.net/text.asp?2017/13/1/118/199389
| > Introduction|| |
Radiation oncology has been quickly improved by the application of new techniques and equipment of radiotherapy. These techniques are based on the modalities of delivering high doses inside small treatment volumes, with variable dose rates that finally lead to the obtaining the homogeneous favorable dose distribution in the target with maximum spare of the normal tissues.,, Although conventional dosimeters, such as ionization chambers, diode, and thermoluminescent detector, measure absolute dose with great precision, but because of their large sensitive volume, the measurement of dose accuracy in a small field undergoing a high-dose rate and dose gradient underestimates the dose.,, Studies related to the invention of a three-dimensional (3-D) dosimetry method for complex treatments ultimately led to applying of the gel dosimeters. The history of using the gel in dosimetry can be dated back to 1950 when Day and Stein indicated a color change in Folin's Phenol under radiation exposures., In 1958, Hoecker and Watkins showed that ionizing radiation induced the polymerization of monomers and it can be as a process for dosimetry. Because of limitations in the first and second generations of gel dosimeters, a third type of plastic dosimeter was proposed. In 2004, Adamovics and Maryanski introduced a transparent and solid dosimeter for 3-D dosimetry. This plastic dosimeter called “PRESAGE” demonstrates a radiochromic response by ionizing radiation. Some special inherent properties of this PRESAGE ® dosimeter capable it as an attractive candidate for replacement of previous gels. For example, it is a transparent solid plastic dosimeter; therefore, it can be manufactured in any favorable shape without any container, in addition to if optical computed tomography is chosen as the reading system of the PRESAGE ®, its response will be more accurate because of the lack of a container wall. One of the disadvantages of polymer and ferric gels is the diffusion of radiated part in gel matrix, so spatial resolution of dosimeter reduces. However, PRESAGE ® did not show any diffusion at all. PRESAGE ® is also tissue equivalent in megavoltage energies, it is not sensitive to oxygen and its response is independent of the room temperature, wide range of energies, and dose rates. Polyurethanes (PUs) can be polymerized at a relatively low temperature (80°C) which minimizes undesired thermal oxidation reactions.
The 3-D matrix of PRESAGE ® dosimeter is PU, which is widely applied in medical equipment, adhesive, construction of coating equipment, and sealant. Furthermore, the dose recorder part of this dosimeter is a kind of leuco dye as leucomalachite green (LMG) and a free radical initiator (RI) such as carbon tetrachloride (CCl4) or chloroform.
For clinical applications of such a dosimetric system, it is essential to evaluate the dosimeter response under various physical conditions. Many factors, such as PRESAGE ® composition, energy and type of radiation, temperature during response evaluation, dose rate, time since irradiation to response evaluation may influence on PRESAGE ® dosimeter response and therefore must be evaluated. For further evaluation of the basic chemical and physical properties, it is necessary to investigate the individual impact of factors which may effect on PRESAGE ® dosimeter response.
As mentioned, changing the temperature may have be an impact on dosimeter response. For Fricke-based gel dosimeter, Davies and Baldock  assessed the effect of the temperature on the dose response of the Fricke–gelatin–xylenol orange gel dosimeter. They concluded that there is no temperature effect on the dose response during measurement in the range 16–25°C. For polymer-based gels, the temperature is an important environmental parameter during polymerization because it may have notable influence on the polymerization process. For example, Spevacek et al. evaluated the effect of temperature on polymer gel dosimeter nuclear magnetic resonance response. They showed that the relaxation rate for the irradiated dosimeter can be represent as a function of dose and temperature. In addition, they concluded that the temperature dependence has an exponential behavior.
For PRESAGE ®, the studies showed that there are contradictory results on temperature dependence of dosimeter response. Adamovics and Maryanski  concluded that heating dosimeter has no significant impact on the dosimeter response to radiation. In the other study, Skyt et al. showed that when variation of the irradiation temperature, significant change in OD of the PRESAGE™ cuvettes occurs. The importance of this subject and contradictory results in the literature were chief motivations for this study to investigating the effect of temperature variation on response of PRESAGE ® dosimeter.
| > Materials and Methods|| |
In this study, a PRESAGE ® solid detector with tissue equivalent properties as well as high sensitive and high stability on postirradiation was fabricated. The main components of PRESAGE ® were PU, CCl4 as free RI, and LMG as dose reporter part. The weight fraction of PU was selected in 94% of the total weight of PRESAGE ®, which is prepared by a combination of one equivalent of polyol (Crystal Clear 206, PART B) with two equivalent of a prepolymer (Crystal Clear 206, made by Smooth-On Inc., PART A). For the dose reporter, 1% LMG was thoroughly dissolved in 5% CCl4 and then added to part B, then the blend was added to the part A and was thoroughly mixed to obtain a homogenous solution. Finally, it was poured in cuvettes and then stored at 60 psi for 72 h. All process was performed in semi-dark condition and at room temperature (22–25°C). It is notable that effective atomic number was calculated by Mayneord formula:
To evaluation of temperate effect on polymerization of PRESAGE ® or color change of it, 30 cuvettes were divided into eight groups with temperatures of − 4, 10, 25, 35, 45, 55, 65, 75, 85, and 90°C. To reach given temperature in the context of PRESAGE ®, each group put in water bath [Figure 1] that raised its temperature already about 15 min. Consequently, optical characterizations of PRESAGE ® were obtained by investigating the absorption spectrum with Cecil CE 7250 spectrophotometer (England) in the wavelength range of 400–800 nm.
To evaluation of the effect of heat and ionization radiation simultaneously in the response of PRESAGE ®, the other eight groups of PRESAGEs ® reached until the given temperature, immediately (in 20 min) delivered 4 gray (Gy) dose for each group separately with 6 MV Siemens accelerator ((Siemens AG, Erlangen, Germany)) in source to surface distance = 100 cm and 2 cm depth, finally, the absorbance of cuvettes obtain with spectrophotometer in the maximum absorbance wavelength.
| > Results and Discussion|| |
Clear and pure PRESAGE ® dosimeter was fabricated. [Figure 2] illustrates visual appearance of PRESAGE ® as well as [Table 1] listed physical properties of PRESAGE ® dosimeter.
[Figure 3] illustrates the absorbance spectrum of PRESAGEs ® in three different temperatures −4, 35, and 85°C. It is clearly observed that the absorption peak at different temperatures was in the range of 630–635 nm. Our results were consistent with other study. Guo et al. evaluated characterization of PRESAGE ® dosimeter. They indicated that the maximum OD change induced by radiation occurs at the red wavelength (about 633 nm). In the other study, khezerloo et al. investigated dosimetric properties of new formulation of PRESAGE ® with tin organometal catalyst. Their results showed that the absorption peak at various doses is in the range of 627–635 nm.
Solid and dashed lines in [Figure 4] depict the changing the PRESAGE ® optical density without or with 4 Gy dose at various temperatures, respectively. The results show that at temperatures below 75°C, temperature variation has no effect on PRESAGE ® dosimeter response while at the temperatures >75°C, temperature variation has an effect on PRESAGE ® dosimeter response. Adamovics and Maryanski  investigated the impact of heating the dosimeter before irradiation. In their study, for 3 h before irradiation, two dosimeters were heated to 50°C and compared with samples which were at room temperature (22°C). Then, dosimeters to doses of 20 and 40 Gy were irradiated. Their results showed that such a heating treatment has no significant effect on the dosimeter response to radiation. Guo et al. evaluated the temperature sensitivity of the radiochromic response by measuring the OD change of cuvettes irradiated to 12 Gy dose. Various evaluated temperatures in their study were 6, 10, 15, 20, and 28°C. Then, OD changes were measured by the spectrophotometer at the wavelength of 633 nm for cuvettes irradiated at various temperatures. They concluded that the dose response of PRESAGE ® dosimeter is sensitive to temperature as irradiation at higher temperature induces larger OD change. Their reason for this conclusion was that probably the radiochromic components of PRESAGE ® dosimeter at higher temperature are more active; therefore, it can create more OD change on irradiation. In addition, they showed that the temperature sensitivity of the dosimeter around room temperature (22°C) can be changed approximately about 1.7% OD variation per degree. Our results were consistent with their studies. In addition, Skyt et al. assessed the effect of storage and irradiation temperature on dose response of PRESAGE ® dosimeter. Their results showed that significant change in OD of the PRESAGE™ cuvettes when variation of the irradiation temperature with a factor two increase in ΔOD from 5°C to 30°C. Our results were inconsistent with their study.
|Figure 4: Variation of optical density with heat only (solid line) and heat + irradiation (dashed line)|
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| > Conclusion|| |
In this study, the impact of temperature variation on dose response of PRESAGE ® dosimeter was investigated. In addition, the impact of temperature associated with radiation on the response of the dosimeter was also assessed. Temperatures evaluated were − 4, 10, 25, 35, 45, 55, 65, 75, 85, and 90°C. The results indicated that changing the temperature has not impact on the absorption peak, so absorbance peak for various temperatures was in the range of 630–635 nm. The results related to investigate the effect of temperature variation on dose response of PRESAGE ® dosimeter showed that at temperatures below 75°C, temperature variation has no effect on PRESAGE ® dosimeter response while at the temperatures >75°C, temperature variation has an effect on PRESAGE ® dosimeter response.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]