Normoxic Polymer Gel Research Articles

Characterization of the chemical and structural modifications induced by X rays on the HEMA based polymer gel

The use of polymer gels in the radiation dosimetry field is rapidly increasing due to the possibility of 3 dimensional (3D) dosimetry. The aim of this study is to produce a new polymer gel with high dose sensitivity. This involved the production of polymer gel compositions containing different percentages of 2-hydroxyethyl methacrylate (HEMA) monomer and Di(ethylene glycol) dimethacrylate (DEGDMA) and 1-Vinyl-2-pyrrolidinone (VP) crosslinkers and these gels were irradiated with radiation dose between 0.5 Gy to 11 Gy, using 6 MV X-ray energy of the medical linear accelerator. The degree of polymerization was assessed by using magnetic resonance imaging (MRI) based on the R2-dose response. Then, Fourier Transform Infrared Spectroscopy (FTIR) analysis and Scanning Electron Microscope (SEM) images of the gels were taken. Polymer gels consisting of DEGDMA as crosslinker and Tetrakis (Hydroxymethyl) phosphonium chloride (THPC) as antioxidant were found to have a potential for use in radiation therapy dosimeter. The concentration of HEMA showing the most effective dose response was identified as 12 wt%. It was found that HEMA polymer gels containing DEGDMA crosslinker provide a better dose response than HEMA and HEMA-VP normoxic polymer gels.

On the comparison of two NIPAM gel dosimeters with high resolution 3D MRI sequences

Polymer gel dosimeters allow the measurement of a dose distribution in 3 dimensions. Irradiation induces polymerization reactions in the long chains of the gel molecules, which is characterized by a change in the transverse relaxation time T2. Gel dosimetry is mainly advantageous for its high resolution, but can also be expensive. The main goal of this project is to compare two normoxic polymer gel recipes made with NIPAM as monomer. The analysis is based on the quality of the images obtained for a fixed MRI scan time and a comparative cost of analysis of each 1L phantom. The ΔT2 maps are obtained by scanning the gels before and after irradiation with 3D sequences and the DESPOT2 technique is used to reconstruct the T2 maps. The phantoms were irradiated with 8 photon beams of 6 MV with a fixed 250 MU, 4 at two opposite sides of the jar (AP-PA configuration), to obtain 4 dose distributions of 4.7 Gy, 8.9 Gy, 13.2 Gy and 17.3 Gy. The SNR is then determined in the ΔT2 maps in function of the dose step and the concentration of NIPAM in the phantom. The first gel phantom is made with 15% NIPAM and has a total cost of $1561.65, including products and MRI scan costs. The SNR obtained for the 4 dose steps are 10.02, 31.18, 45.12 and 37.54. The contrast between the T2 before and after the irradiation in the 4 regions of dose are 0.45, 0.66, 0.78 and 0.85. The second phantom contained 5% NIPAM, cost 1186.85$ and the SNR obtained are 16.80, 27.08, 30.11 and 26.17 and the ΔT2 are of 0.61, 0.75, 0.79 and 0.77 for the 4 dose steps respectively. The comparison of the two recipes has shown that the increase of NIPAM concentration does not allow a significant increase in image quality for MRI. The recipe with 5% of NIPAM has a lower dynamic range but a better sensitivity at lower dose and is less expensive than the one with 15% of NIPAM. The results also show that by increasing the NIPAM concentration 3-fold, the cost of a 1L phantom increases by 30%.

Investigating the Sensitivity of New Formulation MAGAT and NIPAM Polymer Gels in the Radiation Therapy Dosimetry.

Background: Normoxic polymer gels have been used as a three dimensional (3D) dosimeter in radiation therapy, recently. The sensitivity of these gels is important in dosimetry and their improvement can be also useful.Objective: In this study, different modalities of gel reading were used and the structure of gel changed due to the best improvement of sensitivity. The sensitivities of the new formulation of Methacrylic acid gel (MAGAT) and N-isopropyl acrylamide (NIPAM) polymer gel dosimeters were studied using two different reading methods of magnetic resonance imaging (MRI) and X-ray computed tomography (X-ray CT).Material and Methods: In this experimental study, in addition to making the NIPAM polymer gel dosimeter, a new formulation of normoxic polymer gel dosimeter, which named MAGAT gel, was investigated. The gels were irradiated with 6 MV in low doses, including1, 1.5, 1.75, 2 and 2.5 Gy. MRI and X-ray CT did the reading of gel dosimeters a day after irradiation using an elevated protocol.Results: The dose sensitivities of 0.92 HGy-1 and 0.47 HGy-1 were obtained for new MAGAT and NIPAM polymer gel dosimeters, respectively, based on the X-ray CT reading modality. The use of MRI reading modality and the dose sensitivities were 0.74 S-1Gy-1 and 0.27 S-1Gy-1 for new MAGAT and NIPAM polymer gel dosimeters, respectively.Conclusion: The new formulation of MAGAT polymer gel with a suitable protocol of gel reading has a better response.

Investigation of target dose conformity using normoxic polymer gel dosimetry techniques: A clinical example of 12th thoracic vertebrae SBRT treatment with VMAT

This paper describes the 3D dosimetry verification of a 24Gy in 3 fractions VMAT SBRT treatment delivery to the 12th thoracic vertebrae (T12). With this fractionation regime, the critical isodose value is 17.5Gy to the outer edge of the spinal cord and must not be exceeded. This is a high-risk treatment that could result in severe injury to the patient unless administered precisely. With the use of 3D normoxic polymer gel dosimetry techniques, using MRI readout, a clinical example is presented which shows that the Mid North Coast Cancer Institute’s paraspinal program is capable of delivering complex distributions with high doses to within very tight tolerances. This also demonstrates the strength of normoxic polymer gel as a 3D dosimeter.

Polymer gel containing N,N′-methylene-bis-acrylamide (BIS) as a single monomer for radiotherapy dosimetry

In this study, the first polymer gel that contains N,N′-methylene-bis-acrylamide (BIS) crosslinker without the need of adding another radiosensitive monomer has been introduced as a new low toxic polymer gel dosimeter. Various concentrations (0–0.9 M) of magnesium chloride (MgCl2) were added to BIS gel to improve the dose-response of the gel dosimeter. The gel samples were irradiated in a water phantom to different doses using 6 MV Linac X-ray beams with 200 cGy/min dose rate. The samples were read out using nuclear magnetic resonance (NMR) spectroscopy to measure the relaxation rates (R2) of the scanned samples by a standard Multi-Spin-Echo sequence. The optimum formulation gels were irradiated to different dose-rates (200 and 500 cGy/min) with a fixed radiation-energy of 6 MV, while other samples were irradiated to different radiation-energy (6 and15 MV) with a fixed dose rate of 200 cGy/min to investigate the influence of these important parameters on the performance of gel dosimeters. The dose sensitivity of the composition containing BIS, gelatin and antioxidant agent (BISGAT) polymer gel was very small (0.07 Gy−1s−1) compared to the available normoxic polymer gels such as NIMPAGAT. A significant increase in dose sensitivity (0.33 Gy−1s−1) of BISGAT dosimeter was achieved after adding 0.9 M MgCl2 to the gel which is greater than the standard composition of NIPAMGAT (i.e. BIS and NIPAM monomer) polymer gel with dose sensitivity of 0.16 Gy−1 s−1.The temporal stability of irradiated samples to different doses changed insignificantly (0.07%) in the period up to 6 days. The BISGAT gel with MgCl2 was independent of dose-rate (200 and 500 cGy/min) as well as radiation energy (6 and 15 MV). Additionally, the gel is water equivalent and has theoretical energy-independent response from 0.1 to 20 MeV for the optimum composition. The gel dosimetry accuracy was evaluated in this study by calculating the overall uncertainty and found to be 7.04% (2σ, 95% confidence level).

Novel 3D polymer gel dosimeters based on N-(3-Methoxypropyl)acrylamide (NMPAGAT) for quality assurance in radiation oncology

New anoxic and normoxic polymer gel dosimeters containing different concentrations of N-(3-Methoxypropyl) acrylamide (NMPA) are introduced in this investigation for radiotherapy treatment planning dose validation. NMPA dosimeters were irradiated to 20 Gy using the 10 MV photon beam of a medical linear accelerator under a constant dose rate. The polymerization of NMPA dosimeters occurs and increases monotonically with increasing absorbed dose. Nuclear magnetic resonance (NMR) was used to investigate the degree of polymerization of gels. The dose response in terms of spin–spin relaxation rate (R2) of NMPA dosimeters increased with the addition of glycerol. The influence of the x-ray radiation energy, dose, and dose rate, as well as the stability of the irradiated NMPA gel dosimeters were studied in order to show this preliminary study is indicative of a promising low-toxicity polymer gel dosimeter.

Feasibility Study of Polymer Gel Dosimetry Using a 3D Printed Phantom for Liver Cancer Radiotherapy

In this study, a new three-dimensional (3D) volumetric dosimetry method utilizing gel dosimetry with a patient-specific (PS) 3D-printed phantom was developed. A PS 3D-printed phantom that closely mimics the actual tumor and surrounding tissues was demonstrated using a 3D printer (3Dison Plus, Lokit, Korea). MAGAT normoxic polymer gel was filled in the tumor-shaped cavity of the 3D-printed phantom to represent the real tumor. Seven identical gel samples for dosimetric calibration were irradiated at different doses and scanned using magnetic resonance imaging. A chlorinated polyethylene filament was utilized as the 3D printing material. The two-dimensional gamma passing rates using the film were 96.1% and 84.3% for the 3%/3 mm and the 2%/1 mm dose accuracy/distance-to agreement criteria, respectively. The radiation dose-R2 (relaxation rate) calibration, with a coefficient of determination (R2) of 0.997, was applied for the absolute dose calibration. The overall gross tumor volume shape and the dose distribution of the gel measurement agreed reasonably well with the plan results. The 3D gamma passing rate was 91.2% for the 3%/3 mm criteria and decreased to 82.3% for the 2%/1 mm criterion. Our results suggest that polymer gel dosimetry with the 3D-printed phantom allows direct validation of the 3D dose distribution.

Basic Properties of a New Polymer Gel for 3D-Dosimetry at High Dose-Rates Typical for FFF Irradiation Based on Dithiothreitol and Methacrylic Acid (MAGADIT): Sensitivity, Range, Reproducibility, Accuracy, Dose Rate Effect and Impact of Oxygen Scavenger.

The photon induced radical-initiated polymerization in polymer gels can be used for high-resolution tissue equivalent dosimeters in quality control of radiation therapy. The dose (D) distribution in radiation therapy can be measured as a change of the physical measurement parameter T2 using T2-weighted magnetic resonance imaging. The detection by T2 is relying on the local change of the molecular mobility due to local polymerization initiated by radicals generated by the ionizing radiation. The dosimetric signals R2 = 1/T2 of many of the current polymer gels are dose-rate dependent, which reduces the reliability of the gel for clinical use. A novel gel dosimeter, based on methacrylic acid, gelatin and the newly added dithiothreitol (MAGADIT) as an oxygen-scavenger was analyzed for basic properties, such as sensitivity, reproducibility, accuracy and dose-rate dependence. Dithiothreitol features no toxic classification with a difference to THPC and offers a stronger negative redox-potential than ascorbic acid. Polymer gels with three different concentration levels of dithiothreitol were irradiated with a preclinical research X-ray unit and MR-scanned (T2) for quantitative dosimetry after calibration. The polymer gel with the lowest concentration of the oxygen scavenger was about factor 3 more sensitive to dose as compared to the gel with the highest concentration. The dose sensitivity (α = ∆R2/∆D) of MAGADIT gels was significantly dependent on the applied dose rate (≈48% reduction between = 0.6 Gy/min and = 4 Gy/min). However, this undesirable dose-rate effect reduced between 4–8 Gy/min (≈23%) and almost disappeared in the high dose-rate range (8 ≤12 Gy/min) used in flattening-filter-free (FFF) irradiations. The dose response varied for different samples within one manufacturing batch within 3%–6% (reproducibility). The accuracy ranged between 3.5% and 7.9%. The impact of the dose rate on the spatial integrity is demonstrated in the example of a linear accelerator (LINAC) small sized 5 × 10 mm2 10 MV photon field. For MAGADIT the maximum shift in the flanks in this field is limited to about 0.8 mm at a FFF dose rate of 15 Gy/min. Dose rate sensitive polymer gels likely perform better at high dose rates; MAGADIT exhibits a slightly improved performance compared to the reference normoxic polymer gel methacrylic and ascorbic acid in gelatin initiated by copper (MAGIC) using ascorbic acid.

Investigation of the dose enhancement effect due to gold nanoparticles at 18 MV radiotherapy using MAGIC-f and Monte Carlo methods Thoraco-Lumbar spinal cord fMRI in 3T Magnetic field

Introduction: Normoxic MAGIC-f polymer gels are established dosimeters used for three dimensional dos uantifications in radiotherapy. The high atomic number nanoparticles such as gold are nov adiosensitizers used to enhance doses delivered to tumors. The aim of this study was t vestigate the effect of gold nanoparticles (GNPs) in enhancing percentage depth doses (PDD ithin the MAGIC-f gel exposed to linac high energy photon beams (18MV). Materials and methods: The MAGIC-f gel was fabricated based on its standard composition with some modifications an oured into falcon tubes. The PDDs in the tubes containing the gel were calculated using a commo onte Carlo code (MCNPX) followed by experimental verifications. Then, the GNPs with a verage diameter of 15 nm and a concentration of 0.1 mM were embedded in the gel, poured int milar falcon tubes and irradiated to 18 MV beams of a Varian 2100 linac. Finally, simila xperimental and Monte Carlo (MC) calculations were conducted to determine the effect of usin e GNPs on some dosimetric parameters of interest. Results: The results of experimental measurements and simulated MC calculations showed a dos nhancement factor (DEF) of 1.12±0.07 and 1.13±0.06 respectively due to the use of the GNP hen exposed to 18 MV linac energies. Conclusion: The results indicated that the fabricated MAGIC-f gel could be recommended as a suitable tool fo ree dimensional dosimetric investigations at high energy radiotherapy procedures wherein th NPs are used.

UV-Visible Spectrophotometer Analysis on Polymerization of 2-Hydroxyethyl Methacrylate

Polymer gel has been used as a dosimeter to determine spatial dose distributions by radiotherapy equipment. This study studies the absorption peak in the UV-visible (UV-vis) spectrophotometer as the relative intensity of polymerization. Theoretically, high intensity of polymerization results in high absorbance. The size of gold nanoparticles (GNPs) and dose of irradiation are expected to affect polymerization. Normoxic polymer gel samples using 2-Hydroxyethyl methacrylate (HEMA) as the monomer were prepared with different sizes of GNPs in order to study the effect of GNPs with ascorbic acid acting as the oxygen scavenger. Linear accelerator (LINAC) was the source of high irradiation x-ray energy as it is one of the most widely used radiotherapy equipment. Diagnostic x-ray unit acted as the low energy sources. One crucial factor in fabricating the sample is the environment temperature. Radiation induced polymer gel is environmentally sensitive where low temperature environment (

Dose integration and dose rate characteristics of a NiPAM polymer gel MRI dosimeter system

The normoxic polymer gel dosimeter based on N-isopropyl acrylamide (NiPAM) is a promising full 3D-dosimeter with high spatial resolution and near tissue equivalency. NiPAM gel samples were irradiated to different doses using a linear accelerator. The absorbed dose was evaluated using MRI and statistical significance of the analysed data was calculated. The analysis was carried out using an in-house developed software. It was found that the gel dosimeter responded linearly to the absorbed dose. The gel exhibited a dose rate dependence, as well as a dependence on the sequential beam irradiation scheme. A higher dose rate, as well as a higher dose per sequential beam, resulted in a lower dose response.

6 MV Photon Beam Induced UV/VIS Absorption of Hema Polymer Gel

The aim of this study was to evaluate properties of normoxic polymer gel 2-Hydroxyethyl methacrylate monomer (HEMAG) as a point dosimeter by using optical properties evaluation techniques. HEMAG were prepared from seven different radiation dose within five different depths of HEMAG dosimeters. These HEMAG dosimeters were irradiated by linear accelerator with 6 MV photon beams. The absorption spectra were measured by using a UV-visible spectrophotometer in the wavelength range from 300 to 800 nm. Then, the data was analysed to determine the optical energy band gap (Eg) and Urbach’s energy (ΔE). The result showed that Eg and ΔE were dependent on radiation dose and percentage of depth dose (PDD). In additional, Eg with indirect transition of HEMAG decreased as radiation dose increased and increased with traversing of depth. ΔE of HEMAG increased as the dose increased and decreased with traversing depth of monomer. There was a shift in the Eg values towards lower energy as the dose increased and led to a shift of the ΔE value towards the higher energy with increasing dose. This observation supported the increase of structured disorder of the polymer with increasing radiation dose, which resulted in the lower energy transitions that was feasible and reduced the values of Eg. In conclusion, HEMAG has a potential to be used as a dosimeter at low radiation dose in the clinical radiotherapy.

New normoxic N-(Hydroxymethyl)acrylamide based polymer gel for 3D dosimetry in radiation therapy

A novel composition of normoxic polymer gel dosimeters based on radiation-induced polymerization of N-(Hydroxymethyl)acrylamide (NHMA) is introduced in this study for 3D dosimetry for Quality Assurance (QA) in radiation therapy. Dosimeters were irradiated by 6, 10 and 18MV photon beams of a medical linear accelerator at various dose rates to doses of up to 20Gy. The dose response of polymer gel dosimeters was studied using nuclear magnetic resonance (NMR) spin-spin relaxation rate (R2) of hydrogen protons within the water molecule. Also, we measured gel response using absorption spectroscopy and found that this novel gel can be successfully utilized for both MRI- and OCT- (Optical Computed Tomography) based 3D dosimetry. We investigated dosimetric properties of six different compositions of the new NHMA-based gel in terms of dose rate, radiation beam quality and stability of dose-dependent polymerization after irradiation. We found no significant effects of these parameters on the novel gel dosimeter performance in both relaxation rate and absorbance measurements.

SU‐F‐T‐159: Monte Carlo Simulation Studies of Three‐Dimensional Dose Distribution for Polymer Gel Dosimeter and Radiochromic Gel Dosimeter in a Proton Beam

Purpose:The purpose of this simulation study is to evaluate the proton detectability of gel dosimeters, and estimate the three‐dimensional dose distribution of protons in the radiochromic gel and polymer gel dosimeter compared with the dose distribution in water.Methods:The commercial composition ratios of normoxic polymer gel and LCV micelle radiochromic gel were included in this simulation study. The densities of polymer and radiochromic gel were 1.024 and 1.005 g/cm3, respectively. The 50, 80 and 140 MeV proton beam energies were selected. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiation transport code (MCNPX 2.7.0, Los Alamos Laboratory). The water equivalent depth profiles and the dose distributions of two gel dosimeters were compared for the water.Results:In case of irradiating 50, 80 and 140 MeV proton beam to water phantom, the reference Bragg‐peak depths are represented at 2.22, 5.18 and 13.98 cm, respectively. The difference in the water equivalent depth is represented to about 0.17 and 0.37 cm in the radiochromic gel and polymer gel dosimeter, respectively. The proton absorbed doses in the radiochromic gel dosimeter are calculated to 2.41, 3.92 and 6.90 Gy with increment of incident proton energies. In the polymer gel dosimeter, the absorbed doses are calculated to 2.37, 3.85 and 6.78 Gy with increment of incident proton energies. The relative absorbed dose in radiochromic gel (about 0.47 %) is similar to that of water than the relative absorbed dose of polymer gel (about 2.26 %). In evaluating the proton dose distribution, we found that the dose distribution of both gel dosimeters matched that of water in most cases.Conclusion:As the dosimetry device, the radiochromic gel dosimeter has the potential particle detectability and is feasible to use for quality assurance of proton beam therapy beam.

MO‐B‐BRB‐02: 3D Dosimetry in the Clinic: IMRT Technique Validation in Sweden

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

MO‐B‐BRB‐00: Three Dimensional Dosimetry

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

MO‐B‐BRB‐04: 3D Dosimetry in End‐To‐End Dosimetry QA

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

MO‐B‐BRB‐03: 3D Dosimetry in the Clinic: Validating Special Techniques

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

MO‐B‐BRB‐01: 3D Dosimetry in the Clinic: Background and Motivation

Full three‐dimensional (3D) dosimetry using volumetric chemical dosimeters probed by 3D imaging systems has long been a promising technique for the radiation therapy clinic, since it provides a unique methodology for dose measurements in the volume irradiated using complex conformal delivery techniques such as IMRT and VMAT. To date true 3D dosimetry is still not widely practiced in the community; it has been confined to centres of specialized expertise especially for quality assurance or commissioning roles where other dosimetry techniques are difficult to implement. The potential for improved clinical applicability has been advanced considerably in the last decade by the development of improved 3D dosimeters (e.g., radiochromic plastics, radiochromic gel dosimeters and normoxic polymer gel systems) and by improved readout protocols using optical computed tomography or magnetic resonance imaging.In this session, established users of some current 3D chemical dosimeters will briefly review the current status of 3D dosimetry, describe several dosimeters and their appropriate imaging for dose readout, present workflow procedures required for good dosimetry, and analyze some limitations for applications in select settings. We will review the application of 3D dosimetry to various clinical situations describing how 3D approaches can complement other dose delivery validation approaches already available in the clinic. The applications presented will be selected to inform attendees of the unique features provided by full 3D techniques. Learning Objectives: L. John Schreiner: Background and Motivation Understand recent developments enabling clinically practical 3D dosimetry, Appreciate 3D dosimetry workflow and dosimetry procedures, and Observe select examples from the clinic. Sofie Ceberg: Application to dynamic radiotherapy Observe full dosimetry under dynamic radiotherapy during respiratory motion, and Understand how the measurement of high resolution dose data in an irradiated volume can help understand interplay effects during TomoTherapy or VMAT. Titania Juang: Special techniques in the clinic and research Understand the potential for 3D dosimetry in validating dose accumulation in deformable systems, and Observe the benefits of high resolution measurements for precision therapy in SRS and in MicroSBRT for small animal irradiators Geoffrey S. Ibbott: 3D Dosimetry in end‐to‐end dosimetry QA Understand the potential for 3D dosimetry for end‐to‐end radiation therapy process validation in the in‐house and external credentialing setting.Canadian Institutes of Health Research; L. Schreiner, Modus QA, London, ON, Canada; T. Juang, NIH R01CA100835

SU‐E‐T‐753: Three‐Dimensional Dose Distributions of Incident Proton Particle in the Polymer Gel Dosimeter and the Radiochromic Gel Dosimeter: A Simulation Study with MCNP Code

Purpose:The purpose of this study is to estimate the three‐dimensional dose distributions in the polymer and the radiochromic gel dosimeter, and to identify the detectability of both gel dosimeters by comparing with the water phantom in case of irradiating the proton particles.Methods:The normoxic polymer gel and the LCV micelle radiochromic gel were used in this study. The densities of polymer and the radiochromic gel dosimeter were 1.024 and 1.005 g/cm3, respectively. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiation transport code (MCNPX, Los Alamos National Laboratory). The shape of phantom irradiated by proton particles was a hexahedron with the dimension of 12.4 × 12.4 × 15.0 cm3. The energies of proton beam were 50, 80, and 140 MeV energies were directed to top of the surface of phantom. The cross‐sectional view of proton dose distribution in both gel dosimeters was estimated with the water phantom and evaluated by the gamma evaluation method. In addition, the absorbed dose(Gy) was also calculated for evaluating the proton detectability.Results:The evaluation results show that dose distributions in both gel dosimeters at intermediated section and Bragg‐peak region are similar with that of the water phantom. At entrance section, however, inconsistencies of dose distribution are represented, compared with water. The relative absorbed doses in radiochromic and polymer gel dosimeter were represented to be 0.47 % and 2.26 % difference, respectively. These results show that the radiochromic gel dosimeter was better matched than the water phantom in the absorbed dose evaluation.Conclusion:The polymer and the radiochromic gel dosimeter show similar characteristics in dose distributions for the proton beams at intermediate section and Bragg‐peak region. Moreover the calculated absorbed dose in both gel dosimeters represents similar tendency by comparing with that in water phantom.