Film Dosimeters Research Articles

Validation of spine SBRT using a 3D printed Anthropomorphic phantom

A segment of a spine was 3D-printed based on real patient anatomy, using metal-doped high density plastic to radiographically mimic bone. This spine was submerged in a water tank to create an anthropomorphic phantom. The spine print incorporated a slot for Gafchromic EBT3 film dosimeters and fiducials for alignment of measured and calculated dose distributions. Spine SBRT treatment plans were generated for both 6 MV and 10FFF energies based on oncologist-drawn contours transferred from real anatomy. Plans were delivered under image guidance using our clinical procedures, to evaluate the dosimetric accuracy of our planning system in high density inhomogeneities and the geometric accuracy of delivery. Results show that the Acuros XB algorithm (dose-to-water) agrees well with film measurements throughout the measured region, including within the bone substitute material. Alignment of the steep dose gradients in planned and measured doses was within 0.5 mm in the ANT-POST direction and within 0.9 mm in the SUP-INF direction, both within machine tolerances. Our results give us confidence in our ability to plan and accurately deliver spinal SBRT treatments.

Depth dose curve and surface dose measurement with a μm thin dosimetric layer

In a former work inorganic phosphor particles NaYF4:Yb3+, Er3+ were found to exhibit a radiation dose dependency of their luminescence decay time upon near-infrared excitation. This material is now presented in the form of an ultra-thin dosimeter to measure depth dose curves. They were derived by electron beam irradiation of 1.6 μm thin dosimeters through a stepped stack of absorber polymer films followed by optical decay time evaluation. The suitability of the phosphor dosimeters for depth curve measurement is proven by good agreement in normalized dose results with film dosimeter (Risø B3 strips) after medium-energy electron-beam irradiation. But the approach qualifies especially for use at low-energies, where original measurement results from as close as 3–4 μm (water equivalent) from the surface are obtained for 80, 140 and 200 keV e-beam irradiations. They align well with results from Monte Carlo simulations. Thus, an approach is proposed for discussion which may allow the experimental evaluation of the first μm of depth dose curves after low-energy electron beam irradiation.

Radiation Induced Decoloration of Reactive Dye in PVA Films for Film Dosimetry

The investigation of film dosimeters made from polyvinyl alcohol (PVA) films dyed with methyl orange (MO) to enable their use in high dose radiation processing applications was studied. The dosimetric change in these films at pre and post irradiation was studied spectrophotometrically. Radiolytic bleaching was observed in PVA aided films exposed with Cs137 γ-source in dose range of 100-200kGy. The effects of pH, dye concentration and film thickness on the radiation response of the film dosimeters were discussed. The stability of MO-PVA films before and after exposure of radiation was also examined at ambient temperature and was found to be higher for long times at pre and post irradiation stages.

Health Risks of Low Dose Of Ionizing Radiation Among Health Care Providers at ain Shams University Hospitals

Abstract Introduction Ionizing radiation (IR) is an occupational hazard that can induce many health risks on exposed health care workers (HCWs). However, the health risks of low dose (below 100mSv) are controversial due to a lack of direct evidence on human. Aim of work To identify the health risks of exposure to low dose of ionizing radiation and its effect on general health status and to assess oxidative stress status of health care workers (HCWs) exposed to IR at Ain Shams University hospitals. Materials and methods A comparative cross-sectional study was conducted including 50 HCWs from different departments of Ain Shams University hospitals: exposed group (exposed to IR for at least I year) (No = 25) and matched unexposed control group (No = 25). Both groups were interviewed using a structured questionnaire. Assessment of health care workers' oxidative stress status was done for both groups by measure level of plasma malondialdehyde (MDA) level as biomarker for lipid peroxidation. Complete blood count was done for both groups. Recording readings of personal exposure to IR by badge film dosimeter after approval from workplace authority was also done. Results Regarding general health status and wellbeing of workers, most of exposed group had perception of average health status, while most of unexposed group had perception of good health status. A significantly higher sickness absenteeism during the last 6 months was found among the exposed group and a significant adverse health effects, were recorded among exposed group compared to control group as hair fall, musculoskeletal pain, pain in upper abdomen, constipation, decreased visual acuity, in addition to easily agitated. During the last 30 days exposed group had significantly higher frequencies of GIT disturbances and common cold or infections in comparison to unexposed group. The results showed that IR exposed group had the more oxidative stress status (higher level of plasma MDA) than unexposed group with significant difference (p value =0.014). Results showed also that the Mean Corpuscular Hemoglobin (MCH), Absolute lymphocyte and monocyte counts were significantly lower while relative basophile % was significantly higher among exposed group in comparison to unexposed group (although all parameters were within normal range in both groups). Conclusion Exposure to IR -even in small dose- may lead to significant health complains (adverse health effects), increase oxidative stress status and may affect general health status among exposed group compared to the non-exposed one. Recommendations Personal monitoring for ionizing radiation, periodic medical examination, and increasing level of protection for exposed workers are of utmost importance.

Performance of a newly designed end‐to‐end phantom compatible with magnetic resonance‐guided radiotherapy systems

In this study, we report on our proposed phantom based on the new end-to-end (E2E) methodology and its results. In addition, we verify whether the proposed phantom can replace conventional phantoms. The hexagonal-shaped newly designed phantom has pockets on each side for a film dosimeter of size 80×90mm2 , which is easily removable, considering the 60 Co penumbra. The new phantom comprises water, shell, and auxiliary shell phantoms. The shell and auxiliary shell materials are Solid Water HE. A mock tumor (aluminum oxide) was attached by a single prop in the water phantom and placed at the center of the new phantom. The results of a conventional E2E test were compared with those of the novel E2E test using the newly designed phantom. The irradiated film dosimeter in the novel E2E test was scanned in a flatbed scanner and analyzed using an in-house software developed with MATLAB. The irradiated field center, laser center, and mock tumor center were calculated. In the novel image-matching E2E (IM-E2E) test, image matching is performed by aligning the laser center with ruled lines. In the novel irradiation-field E2E (IF-E2E) test, the displacement of the irradiation-field center was defined as its distance from the laser center. In the composite E2E test, the overall displacement, which included the accuracy of the irradiated field and image matching, was defined as the distance between the irradiated field center and mock tumor center. In addition, using the newly designed phantom, the overall irradiation accuracy of the machine was evaluated by calculating the three-dimensional (3D) center of the irradiated field, phantom, and laser. The composite E2E test could be performed using the newly designed phantom only. In the IM-E2E test, the results of the conventional and novel IM-E2E tests were significantly different in each direction (left-right direction: p-value<<0.05, anterior-posterior direction: p-value=0.002, and superior-inferior direction: p-value=0.002). The displacement directions were the same in both the conventional and novel IM-E2E tests. In the analysis of the IF-E2E test, no significant difference was evident between the results in each direction. Moreover, the displacement directions were the same in the conventional and novel IF-E2E tests, except for the left-right lateral direction of head three. In addition, the 3D analysis results of the novel IF-E2E test were less than 1mm in all directions. In the analysis of the composite E2E test, the maximum displacement was 1.4mm in all directions. In addition, almost all results of 3D analysis for the composite E2E test were less than 1mm in all directions. The newly designed E2E phantom simplifies the E2E test for MRIdian, and is a possible alternative to the conventional E2E test. Furthermore, we can perform the previously unfeasible composite E2E tests that include the entire treatment process.

Development, Characterization and Valuable Use of Novel Dosimeter Film Based on PVA Polymer Doped Nitro Blue Tetrazolium Dye and AgNO3 for the Accurate Detection of Low X-ray Doses.

Currently, the uncontrolled exposure of individuals to X-rays during medical examinations represents a substantial danger that threatens both medical professionals and patients. Therefore, radiation dosimetry for low X-ray doses is a very important control of radiation practice in medical diagnostic radiology. In line with this, the current study proposes a valuable dosimeter-based PVA thin film doubly doped with silver nitrate salt and nitro blue tetrazolium dye. The nanocomposite film was prepared via a simple casting method and the different processing parameters were optimized. The performance of radiation detection was evaluated according to optical, chromic, chemical and structural changes after exposure to variable low X-ray doses (0, 2, 4, 10 and 20 mGy). The different film labels exhibited an excellent stability behavior in dark and light upon 30 days of storage. The UV-Vis spectrophotometric study showed a gradual increase in the maximum absorbance as a function of the dose and the corresponding response curve confirmed this linear variation (R = 0.998). A clear structural modification was recorded via X-ray diffraction (XRD) analysis revealing the increase in crystallinity with the level of the dose received by the nanocomposite films. Microscopic surface analysis via SEM assessments revealed a significant morphological change in PVA/Ag+/NBT films exposed to increased radiation doses and typical dendrites growing in needle- or tree-like microstructures appeared with a high X-ray dose. Finally, the nanocomposite films before and after irradiation were evaluated via a spectrocolorimetric study and the different CIELab coordinates, the color difference, as well as the color strength, showed a linear correlation with the intensity of the applied dose. This new dosimeter design could, therefore, provide a promising and efficient alternative for prompt and accurate detection of low X-rays doses in diagnostic radiology.

Photoneutron-induced damage reduction for cardiac implantable electronic devices using neutron-shielding sheets in high-energy X-ray radiotherapy: A phantom study.

To evaluate damage reduction in cardiac implantable electronic devices (CIEDs) caused by photoneutrons in high-energy X-ray radiotherapy using a neutron-shielding sheet (NSS). The NSS consists of a bolus with a thickness of 1 or 2cm (Bls1 or Bls2) as a moderator and several absorbers (20%, 50%, or 80% B4C silicone sheet [B4C20, B4C50, or B4C80] or a 40% LiF silicone sheet [LiF40]). First, a linear accelerator (LINAC) with a water-equivalent phantom was modeled in the simulation and measured experimentally. Several NSSs were placed on the phantom, a Eu:LiCaAlF6 scintillator was placed between the phantom and the NSS, and X-rays were irradiated. The relative counts (Cr=counts when placing the NSS or Bls2) were compared between the experiment and simulation. Second, CIED damage was evaluated in the simulation. The relative damage (Dr=damage when placing or not placing the NSS) was compared among all the NSSs. In addition, the γ-ray and leaking X-ray dose from B4C was measured using a dosimetric film. After determining the optimal NSS combination,Dr value analysis was performed by changing the length of one side and the thickness. The Cr values of the simulation and experiment agreed within a 30% percentage difference, except for Bare or LiF40-only. The Dr value was reduced by 43% when Bls2+B4C80 was applied. The photon dose wasless than5cGy/1500 MU. The Dr values were smaller for the smaller lengths of one side of B4C80 and decreased as the M-layer thickness increased. The CIED damage induced by photoneutrons generated by a LINAC was effectively reduced by applying the optimal NSS.

Evaluation of two-dimensional dosimeter based on thallium (I) bromide for measurement of surface dose in radiotherapy

In radiotherapy, side effects can occur on the skin because each patient's skin has a different level of sensitivity to radiation. Therefore, in clinical practice, point dose is measured to verify skin doses, although there is a problem, in that it is difficult to analyse the dose distribution for the body surface area. In this study, we constructed a film dosimeter based on polycrystalline thallium (I) bromide, evaluated its performance, and analysed the electrical properties according to the number of bending cycles to evaluate the mechanical flexibility. Further, an array dosimeter was constructed, and the dose distribution was analysed to evaluate the clinical effectiveness. As a result of the performance evaluation, reproducibility, linearity, and dose-rate dependence all satisfied the evaluation criteria. Percent depth dose showed similar results, and a difference of 0.027 when the slope of the depth in the range of 20–10 cm was compared with that of the thimble chamber. With regard to mechanical flexibility, as the number of bending cycles increased, the sensitivity tended to decrease. The clinical efficacy evaluation showed that the difference in dose distribution between the boundary field and non-field was approximately ≥ 40%, which decreased exponentially as the distance from the boundary field increased. The gap dose distribution showed an average difference of approximately ≥ 47% compared with the beam profile central axis. This suggests the possibility of application as a radiotherapy digital dosimeter, as well as the possibility of analysing the dose distribution on the body surface.

1,10-Bis(diphenylamino)-4,6-decadiyne as an active component of a radiochromic film dosimeter

Gamma-irradiation processes are very important tools for minimizing microbial load in dry food, inhibiting the proliferation of T-lymphocytes in blood, and for the sterilization of medical devices. To this end, a composite film dosimeter made of a radiation-sensitive monomer, 1,10-bis(diphenylamino)-4,6-decadiyne (DPD), embedded in poly(vinyl alcohol) was prepared using an automatic film applicator system. This polymeric film undergoes a color change from pale yellow to deep orange upon γ-irradiation due to topochemical polymerization of the DPD monomer. This color change is proportional to the amount of absorbed dose. With increasing absorbed doses, gradual disappearance of the νC≡C Raman band of the C≡C-C≡C chemical groups is observed, and new νC≡C and νC=C bands ascribed to the formation of a polydiacetylene with an enyne structure are detected. The irradiated films exhibited two absorption maxima at 470 and 502 nm as measured by UV-Vis spectrophotometry, and the intensities of these bands increased with increasing absorbed doses. Analysis of these films using a high-resolution flatbed scanner (2400 dpi) showed an increase in optical density with increasing absorbed doses up to 269.1 kGy. Stability studies revealed that the irradiated films underwent an increase in the color intensity by ∼3.1% over 50 days of storage. In addition, relative humidities in the range 0–75.3% had a limited impact on the dose response of the films, with a 4% change in this range. The uncertainty (2σ) on dose measurements using the scanner was 4.46%, demonstrating the effectiveness of this film dosimeter for radiation monitoring up to 296.1 kGy.

Clinical utility of Gafchromic film in an MRI-guided linear accelerator

BackgroundThe purpose of this study is to comprehensively evaluate the suitability of Gafchromic EBT3 and EBT-XD film for dosimetric quality assurance in 0.35 T MR-guided radiotherapy.MethodsA 0.35 T magnetic field strength was utilized to evaluate magnetic field effects on EBT3 and EBT-XD Gafchromic films by studying the effect of film exposure time within the magnetic field using two timing sequences and film not exposed to MR, the effect of magnetic field exposure on the crystalline structure of the film, and the effect of orientation of the film with respect to the bore within the magnetic field. The orientation of the monomer crystal was qualitatively evaluated using scanning electron microscopy (SEM) compared to unirradiated film. Additionally, dosimetric impact was evaluated through measurements of a series of open field irradiations (0.83 × 0.83-cm2 to 19.92 × 19.92-cm2) and patient specific quality assurance measurements. Open fields were compared to planned dose and an independent dosimeter. Film dosimetry was applied to twenty conventional and twenty stereotactic body radiotherapy (SBRT) patient specific quality assurance cases.ResultsNo visual changes in crystal orientation were observed in any evaluated SEM images nor were any optical density differences observed between films irradiated inside or outside the magnetic field for both EBT3 and EBT-XD film. At small field sizes, the average difference along dose profiles measured in film compared to the same points measured using an independent dosimeter and to predicted treatment planning system values was 1.23% and 1.56%, respectively. For large field sizes, the average differences were 1.91% and 1.21%, respectively. In open field tests, the average gamma pass rates were 99.8% and 97.2%, for 3%/3 mm and 3%/1 mm, respectively. The median (interquartile range) 3%/3 mm gamma pass rates in conventional QA cases were 98.4% (96.3 to 99.2%), and 3%/1 mm in SBRT QA cases were 95.8% (95.0 to 97.3%).ConclusionsMR exposure at 0.35 T had negligible effects on EBT3 and EBT-XD Gafchromic film. Dosimetric film results were comparable to planned dose, ion chamber and diode measurements.

Calibration of Gafchromic XR-RV3 film under interventional radiology conditions

Abstract Introduction: The purpose of the study was the calibration of Gafchromic films in clinical interventional radiology conditions and the assessment of the influence of dose range, the shape of the fitting curve, and its practical application. The aim of the work was to show how practically perform calibration in a wide range of doses. Material and methods: Gafchromic XR–RV3 films were included in the study. The calibration was performed for A and B film series separately. Doses from the range of 0 – 8 Gy were used. Film dosimeters were read out in reflective mode with a commercial flatbed scanner. Results: Among various degrees of a polynomial function, the best fit, which fulfilled the chosen criterion of 95% agreement between measured and reconstructed doses and simple equation criterion, was observed for third-degree polynomial. The fitting curve where the dose is the function of optical density (logMPV) was demonstrated to be more precise than the fitting curve based on MPV only. To minimize the difference between dose absorbed by the film and dose reconstructed from the fitting curve below 5% it is necessary to divide the calibration range of 0 – 8 Gy into two subranges for use in interventional radiology. This difference was set at a maximum level of 3.8% and 1.9% for the lowand high-dose range, respectively. Each series of films may have a slightly different calibration curve, especially for the low dose range. A deviation of up to 36% between two batches of Gafchromic film was observed. Conclusions: For the third-degree polynomial fitting function (one of the recommended in the literature) calibration should be done into low and high dose ranges and for each batch separately. A systematic error higher than 20% could be introduced when the fitting curve from one film batch is applied to the other film batch.

Energy deposition calculation by Monte Carlo simulation in irradiation of electric cables by electron beam

The reason for crosslinking the insulation polymer in wire and cable by radiation is to improve their performance at an elevated temperature, the chemical resistance, toughness and abrasion resistance in use. The quality of products made by radiation processing depends not only on the absorbed dose but also on homogenuity of dose distribution especially in circular objects like cables which have different density in conductor and insulation part, respectively.It is important to optimize crosslinking processes for reducing the operation cost while sustaining suitable quality of the final product. The computer simulation method becomes a very useful tool for optimizing process, providing essential information in a short time and reducing cost comparing with the conventional method based on experimental dosimetry. The application of several Monte Carlo codes for electron and photon transport and the advances in computing systems, make possible to accomplish dosimetry tasks by numerical simulation. With increased computing speed and decreasing hardware cost, it is expected that Monte Carlo based electron dose calculation algorithms will become available for routine electron beam dosimetry. We have developed the EBSCANmc (simulator program) in order to simulate and study the crosslinking of electric cables. EBSCANmc employs the MCNP (Monte Carlo N-Particle) 6.2 code, which is a general purpose Monte Carlo particle transport code. The computer simulation of the dose distributions in electric cables was performed for various process parameters, namely the level of electron beam energy, irradiation positions, the density of cable insulator, and backscattering. The results of computer simulation are compared with experimental data using the CTA film dosimeter.

Radiation hardened H-diamond MOSFET (RADDFET) operating after 1 MGy irradiation

Although the surface conductivity of a hydrogen-terminated diamond (H-diamond) enables production of high-performance field effect transistors (FETs), the total ionizing dose effect is yet to be clarified for H-diamond FETs. We fabricated a RADiation hardened H-terminated Diamond metal–oxide–semiconductor FET (RADDFET) using an oxide gate dielectric deposited at high temperatures. This paper describes its stable operation after 1 MGy irradiation. H-diamond films were prepared using microwave plasma assisted chemical vapor deposition with a p+ layer for reduction of contact resistance. The Al2O3 passivation layer was deposited by atomic layer deposition at 450 °C to achieve operation in high-temperature environment; then a RADDFET was fabricated on them using a Ru electrode. Several current–voltage characteristics were compared before irradiation and after certain dose levels up to 1 MGy. Before they were irradiated in air, the dose rate was measured using a cellulose triacetate film dosimeter. Even after an irradiation level of 1 MGy, the off-current at gate bias voltage (VG) of 3 V was more than six orders of magnitude lower than the on-current at VG of −6 V. Variation of the drain current density (JDS) in the measurements was less than 2%. The threshold voltage shifted approximately 1.7 V with 3 kGy of x ray irradiation, but no marked degradation was confirmed at higher levels. The subthreshold swings were 238, 215, and 264 mV/decade, respectively, after irradiation of 100 kGy, 300 kGy, and 1 MGy. These results indicate that the RADDFET was very stable at higher doses after initial stabilization.

Dose measurements in a thorax phantom at 3DCRT breast radiation therapy.

The anthropomorphic and anthropometric phantom developed by the research group NRI (Núcleo de Radiações Ionizantes) can reproduce the effects of the interactions of radiation occurring in the human body. The whole internal radiation transport phenomena can be depicted by film dosimeters in breast RT. Our goal was to provide a dosimetric comparison of a radiation therapy (RT) plan in a 4MV 3D-conformal RT (4MV-3DCR T) and experimental data measured in a breast phantom. The RT modality was two parallel opposing fields for the left breast with a prescribed dose of 2.0 Gy in 25 fractions. The therapy planning system (TPS) was performed on CA T3D software. The dose readings at points of interest (POI) pre-established in TPS were recorded. An anthropometric thorax-phantom with removal breast was used. EBT2 radiochromic films were inserted into the ipisilateral breast, contralateral breast, lungs, heart and skin. The irradiation was carried out on 4/80 Varian linear accelerator at 4MV. The mean dose at the OAR's presented statistically significant differences (p < 0.001) of 34.24%, 37.96% and 63.47% for ipsilateral lung, contralateral lung, and heart, respectively. The films placed at the skin-surface interface in the ipsilateral breast also showed statistically significant differences (p < 0.001) of 16.43%, -10.16%, -14.79% and 15.67% in the four quadrants, respectively. In contrast, the PTV dosimeters, representative of the left breast volume, encompassed by the electronic equilibrium, presented a non-significant difference with TPS, p = 0.20 and p = 0.90. There was a non-significant difference of doses in PTV with electronic equilibrium; although no match is achieved outside electronic equilibrium.

‘End to end’ dosimetry audit for HDR brachytherapy

Purpose: A dosimetric audit of Ir-192 high dose rate (HDR) brachytherapy remote afterloading units was carried out in 2019. All six brachytherapy departments on the island of Ireland participated in an end-to-end test and in a review of local HDR dosimetry procedures. Materials and methods: A 3D-printed customised phantom was created to position the following detectors at known distances from the HDR source: a Farmer ionization chamber, GafChromic film and thermoluminescent dosimeters (TLDs). Dedicated HDR applicator needles were used to position an Ir-192 source at 2 cm distance from these detectors. The end-to-end dosimetry audit pathway was performed at each host site and included the stages of imaging, applicator reconstruction, treatment planning and delivery. Deviations between planned and measured dose distributions were quantified using gamma analysis methods. Local procedures were also discussed between auditors and hosts.

Diacetylene-Based Colorimetric Radiation Sensors for the Detection and Measurement of γ Radiation during Blood Irradiation.

Blood and its cellular components are irradiated by ionizing radiation before transfusion to prevent the proliferation of viable T lymphocytes which cause transfusion associated-graft versus host disease. The immunodeficient patients undergoing chemotherapy for various malignancies are at risk of this disease. The international guidelines for blood transfusion recommend a minimum radiation exposure of 25 Gray (Gy) to the midplane of the blood bag, while a minimum dose of 15 Gy and a maximum dose of 50 Gy should be given to each portion of the blood bag. Therefore, precise dosimetry of the blood irradiator is essential to ensure the adequate irradiation of the blood components. The paper presents the fabrication of diacetylene-based colorimetric film dosimeters for the verification of irradiated doses. The diacetylene analogues are synthesized by tailoring them with different amide-based headgroups followed by their coating to develop colorimetric film dosimeters. Among all the synthesized diacetylene analogues, aminofluorene-substituted diacetylene exhibits the most significant color transition from white to blue color at a minimum γ radiation dose of 5 Gy. The quantitative study of color change is performed by the digitization of the scanned images of film dosimeters. The digital image processing of the developed film dosimeters facilitates rapid dose measurement which enables their facile implementation and promising application in routine blood irradiator dosimetry.

Methyl thymol blue solution and film dosimeter for high dose measurements

A novel radio-chromic solutions and polyvinyl alcohol (PVA) films with different concentrations of methyl thymol blue (MTB) dye have been investigated and studied for high dose applications. The MTB dosimeters were exposed to irradiation using gamma ray 60Co source from 2.5 to 50 kGy for film, and from 0.10 to 2.5 kGy for solutions. The radio-chromic dosimeters were investigated using ultraviolet visible (UV–Vis) spectrophotometry. The effect of MTB dye concentration, relative humidity, and stability of the dosimeters were investigated. The results show that the dose response sensitivity of the dosimeters improved significantly with increasing the absorbed dose and MTB dye concentrations. The un-irradiated and irradiated dosimeters show a perfect stability for one week. Hence, these films can be used as dosimeters in industrial radiation processing. The study shows that the useful dose range is in the range of 2.5–20 kGy and 0.1–1.2 kGy, for film and solution dosimeters, respectively.

Quantification of narrow band UVB radiation doses in phototherapy using diacetylene based film dosimeters

Narrow band ultraviolet B (NB UVB) radiation doses are administered during phototherapy for various dermatological ailments. Precise quantification of these doses is vital because the absorbed irradiation can cause adverse photochemical reactions which can lead to potential phototherapeutic side effects. The paper presents development of diacetylene based dosimeter for the determination of therapeutic NB UVB doses during phototherapy. The amide terminated diacetylene analogues have been synthesized by tailoring them with different functional groups. The synthesized diacetylene monomers have been introduced in a polyvinyl alcohol binder solution to obtain a film dosimeter. The influence of different headgroups on the colorimetric response to UV radiation has been studied. Among all the synthesized diacetylene analogues, the naphthylamine substituted diacetylene exhibited excellent color transition from white to blue color at 100 mJ cm−2 NB UVB radiation dose. The developed amide films can be easily pasted on multiple sites of the patient’s skin to monitor doses during phototherapy simultaneously at different anatomical regions. The digital image processing of the scanned images of the irradiated films facilitates rapid dose measurement which enables facile implementation of the developed film dosimeters and promising application in routine clinical dosimetry.

End-to-end dosimetric audit: A novel procedure developed for Irish HDR brachytherapy centres.

A dosimetric audit of Ir-192 high dose rate (HDR) brachytherapy remote after-loading units was carried out in 2019. All six brachytherapy departments on the island of Ireland participated in an end-to-end test and in a review of local HDR dosimetry procedures. A 3D-printed customised phantom was created to position the following detectors at known distances from the HDR source: a Farmer ionization chamber, GafChromic film and thermoluminescent dosimeters (TLDs). Dedicated HDR applicator needles were used to position an Ir-192 source at 2cm distance from these detectors. The end-to-end dosimetry audit pathway was performed at each host site and included the stages of imaging, applicator reconstruction, treatment planning and delivery. Deviations between planned and measured dose distributions were quantified using gamma analysis methods. Local procedures were also discussed between auditors and hosts. The mean difference between Reference Air Kerma Rate (RAKR) measured during the audit and RAKR specified by the vendor source certificate was 1.3%. The results of end-to-end tests showed a mean difference between calculated and measured dose of 2.5% with TLDs and less than 0.5% with Farmer chamber measurements. GafChromic films showed a mean gamma passing rates of >95% for plastic and metal applicators with 2%/1 mm global tolerance criteria. The results of this audit indicate dosimetric consistency between centres. The 'end to end' dosimetry audit methodology for HDR brachytherapy has been successfully implemented in a multicentre environment, which included different models of Ir-192 sources and different treatment planning systems. The ability to create a 3D-printed water-equivalent phantom customised to accurately position all three detector types simultaneously at controlled distances from the Ir-192 source under evaluation gives good reproducibility for end-to-end methodology.

Application of Patient-Customized Cast Type M3 Wax Bolus using a 3D printing for Photon Beam Radiation Therapy in Patients with Scalp Malignant Tumor

Introduction: We investigated the usefulness of patient-customized cast type M3 wax bolus (MWB) in radiation therapy in scalp malignant tumor patients by 3D conformal radiation therapy (3D CRT) and intensity-modulated radiation therapy (IMRT). Material and Methods: A helmet-type polylactic acid (PLA) hollow model was fabricated using a 3D Printing, and the molten MWB was poured into the mold and allowed to harden. Subsequently, a solid MWB head cast was obtained by removing the PLA. The radiation volume was verified using a metal oxide semiconductor field-effect transistor (MOSFET) dosimeter and EBT3 film. Results: Radiation dose verification was performed at the anterior, right, and left angles of planning tumor volume. The error rate demonstrated a maximum value of 5.5% and an average of 3.3% using the MOSFET dosimeter, and a maximum value of 7.0% and an average of 5.4% applying the EBT3 film. The homogeneity indices of the treatment plans were obtained as 0.09 and 0.12 using 3D CRT and IMRT, respectively. Moreover, the conformity number of the treatment plans was reported as 0.79 using 3D CRT and 0.81 applying IMRT. Conclusion: The density of the MWB head cast was 1.05 g/cm3 which is closer to that of the equivalent tissue than the existing helmet type bolus material. In addition, it reduces the processing time and associated pain during custom manufacturing and has little air gaps. Therefore, it can be considered an effective method for the treatment of patients with scalp malignant tumors.