Radiochromic Film Research Articles

Dosimetric comparison and evaluation of two computational algorithms in VMAT treatment plans.

This study aimed to assess the accuracy and dosimetric impact of the Acuros XB (AXB) algorithm compared to the Anisotropic Analytical Algorithm (AAA) in two situations. First, simple phantom geometries were set and analyzed; moreover, volumetric modulated arc therapy (VMAT) clinical plans for Head & Neck and lung cases were calculated and compared. First, a phantom study was performed to compare the algorithms with radiochromic EBT3 film doses using one PMMA slab phantom and two others containing foam or air gap. Subsequently, a clinical study was conducted, including 20 Head & Neck and 15 lung cases irradiated with the VMAT technique. The treatment plans calculated by AXB and AAA were evaluated in terms of planning target volume (PTV) coverage (V95% ), dose received by relevant organs at risk (OARs), and the impact of using AXB with a grid size of 1mm. Finally, patient-specific quality assurance (PSQA) was performed and compared for 17 treatment plans. Phantom dose calculations showed a better agreement of AXB with the film measurements. In the clinical study, AXB plans exhibited lower Conformity Index and PTV V95% , higher maximum PTV dose, and lower mean and minimum PTV doses for all anatomical sites. The most notable differences were detected in regions of intense heterogeneity. AXB predicted lower doses for the OARs, while the calculation time with a grid size of 1mm was remarkably higher. Regarding PSQA, although AAA was found to exhibit slightly higher gamma passing rates, the difference did not affect the AXB treatment plan quality. AXB demonstrated higher accuracy than AAA in dose calculations of both phantom and clinical conditions, specifically in interface regions, making it suitable for sites with large heterogeneities. Hence, such dosimetric differences between the two algorithms should always be considered in clinical practice.

Organ dose in CT: Comparison between measurements and computational methods

PurposeThis study aims to compare two methods for the organ dose evaluation in computed tomography (CT) in the head- and thorax regions: an experimental method, using radiochromic films, and a computational one, using a commercial software. MethodsGafchromic® XR-QA2 and EBT-3 were characterized in terms of energetic, angular, and irradiation configurations dependence. Two free-in-air irradiation calibration configurations were employed using a CT scanner: with the sensitive surface of the film orthogonal (OC) and parallel (PC) to the beam axis. Different dose–response curves were obtained by varying the irradiation configurations and the beam quality (BQ). Subsequently, films were irradiated within an anthropomorphic phantom using CT-thorax and -head protocols, and the organ dose values obtained were compared with those provided by the commercial software. ResultsAt different configurations, an unchanged dose response was achieved with EBT-3, while a dose response of 15% was obtained with XR-QA2. By varying BQ, XR-QA2 showed a different response below 10%, while EBT-3 showed a variation below 5% for dose values >20 mGy. For films irradiation angle equal to 90°, the normalized to 0° relative response was 41% for the XR-QA2 model and 83% for the EBT-3 one. Organ dose values obtained with EBT-3 for both configurations and with XR-QA2 for OC were in agreement with the DW values, showing percentage discrepancies of less than 25%. ConclusionsThe obtained results showed the potential of EBT-3 in CT patient dosimetry since the lower angular dependence, compared to XR-QA2, compensates for low sensitivity in the diagnostic dose range.

An open-source development based on photogrammetry for a real-time IORT treatment planning system

PurposeThis study presents a treatment planning system for intraoperative low-energy photon radiotherapy based on photogrammetry from real images of the surgical site taken in the operating room. Material and methodsThe study population comprised 15 patients with soft-tissue sarcoma. The system obtains the images of the area to be irradiated with a smartphone or tablet, so that the absorbed doses in the tissue can be calculated from the reconstruction without the need for computed tomography.The system was commissioned using 3D printing of the reconstructions of the tumor beds. The absorbed doses at various points were verified using radiochromic films that were suitably calibrated for the corresponding energy and beam quality. ResultsThe average reconstruction time of the 3D model from the video sequence in the 15 patients was 229,6±7,0 s. The entire procedure, including video capture, reconstruction, planning, and dose calculation was 520,6±39,9 s. Absorbed doses were measured on the 3D printed model with radiochromic film, the differences between these measurements and those calculated by the treatment planning system were 1.4% at the applicator surface, 2.6% at 1 cm, 3.9% at 2 cm and 6.2% at 3 cm. ConclusionsThe study shows a photogrammetry-based low-energy photon IORT planning system, capable of obtaining real-time images inside the operating room, immediately after removal of the tumor and immediately before irradiation. The system was commissioned with radiochromic films measurements in 3D-printed model.

Development and Dosimetric Characterization of a Customizable Shield for Subtotal Skin Electron Beam Therapy

Purpose: Subtotal skin electron beam therapy may be an option for patients with cutaneous lymphoma receiving radiation therapy to treat large areas of their skin but may benefit from sparing specific areas that may have had previous radiation therapy, are of specific cosmetic concern, and/or show no evidence of disease. We report here on the design, implementation, and dosimetric characteristics of a reusable and transparent customizable shield for use with the large fields used to deliver total skin electron beam therapy at extended distance with a conventional linear accelerator. A shield was designed and manufactured consisting of acrylic blocks that can be mounted on a steel frame to allow patient-specific shielding. The dosimetry of the device was measured using radiochromic film. The shield is easy to use and well-tolerated for patient treatment, providing minimal electron transmission through the shield with a sharp penumbra at the field edge, with no increase in x-ray dose. We report on the dosimetry of a commercial device that has been used to treat more than 30 patients to date. The customizable shield is well suited to providing patient-specific shielding for subtotal skin electron beam therapy.

Development of a 3D printing process of bolus using BolusCM material for radiotherapy with electrons

This work presents the optimized parameters of 3D printing for print bolus using BolusCM material. Printing parameters were selected of the homogeneity and absence of air gaps. The dosimetric features of printed bolus were measured with a plane-parallel ionization chamber and EBT3 radiochromic film. Measured features were compared with those estimated with Monte Carlo methods. BolusCM shows good characteristics to be used as bolus material in radiotherapy with electrons, where the printing process allows personalizing the bolus in function of patient characteristics. The material low-cost, the 3D printing and the dosimetric features are few of the advantages of using BolusCM material in radiotherapy with electrons in skin cancer treatment.

Comparing brass mesh to tissue equivalent bolus materials for volumetric modulated arc therapy chest wall irradiation.

To compare the superficial dose when using brass mesh bolus (BMB), no bolus, or 3mm tissue-equivalent bolus with a pseudo-flash volumetric modulated arc therapy (VMAT) breast treatment planning technique. Two different beam arrangements for right-sided irradiation and one beam arrangement for bilateral irradiation were planned on an inhomogeneous thorax phantom in accordance with our clinical practice for VMAT postmastectomy radiotherapy (PMRT). Plans were optimized using pseudo-flash and representative critical organ optimization structures were used to shape the dose. Plans were delivered without bolus, with 3mm tissue-equivalent bolus (TEB), or with one-layer BMB. Optically stimulated luminescence dosimeter (OSLD) and radiochromic film measurements were taken and analyzed to determine the superficial dose in each case and the relative enhancement from the no bolus delivery. Superficial dose measured with OSLDs was found to be 76.4±4.5%, 103.0±6.1%, and 98.1±5.8% of prescription for no physical bolus (NB), TEB, and BMB, respectively. Superficial dose was observed to increase from lateral to medial points when measured with film. However, the relative increase in superficial dose from NB was consistent across the profile with an increase of 43±2.1% and 34±3.3% of prescription for TEB and BMB, respectively. The results are in good agreement with expectations from the literature and the experience with tangential radiotherapy. Three millimeter TEB and one-layer BMB were shown to provide similar enhancement to the superficial dose compared to delivery without bolus. BMB, which does not significantly affect dose at depth and is more conformal to the patient surface, is an acceptable alternative to 3mm TEB for chest wall PMRT patients treated with pseudo-flash PMRT.

Physical wedge as a tool for radiochromic film calibration

Reliable calibration is one of the major challenges in using radiochromic films (RCF) for radiation dosimetry. In this study the feasibility of using dose gradients produced by a physical wedge (PW) for RCF calibration was investigated. The aim was to establish an efficient and reproducible method for calibrating RCF using a PW. Film strips were used to capture the wedge dose profile for five different exposures and the acquired scans were processed to generate corresponding net optical density wedge profiles. The proposed method was compared to the benchmark calibration, following the guidelines for precise calibration using uniform dose fields. The results of the benchmark comparison presented in this paper showed that using a single film strip for measuring wedge dose profile is sufficient for estimating a reliable calibration curve within the recorded dose range. Furthermore, the PW calibration can be extrapolated or extended by using multiple gradients for the optimal coverage of the desired calibration dose range. The method outlined in this paper can be readily replicated using the equipment and expertise commonly found in a radiotherapy center. Once the dose profile and central axis attenuation coefficient of the PW are determined, they can serve as a reference for a variety of calibrations using different types and batches of film. This investigation demonstrated that the calibration curves obtained with the presented PW calibration method are within the bounds of the measurement uncertainty evaluated for the conventional uniform dose field calibration method.

Characterization of a new radiochromic film (LD-V1) using mammographic beam qualities

PurposeRadiochromic film (RCF) is a detector that can obtain a two-dimensional dose distribution with high resolution; it is widely used in medical and industrial fields. Several types of RCFs exist based on their application. The type of RCF mainly used for mammography dose assessment has been discontinued; however, a new type of RCF (LD-V1) has been distributed as a successor. Since the medical use of LD-V1 has rarely been studied, we investigated the response characteristics of LD-V1 in mammography. MethodsMeasurements were performed using Mo/Mo and Rh/Ag on a Senographe Pristina mammography device (GE, Fairfield, CT, USA). The reference air kerma was measured using a parallel-plate ionization chamber (PPIC) (C-MA, Applied Engineering Inc, Tokyo, Japan). Pieces of LD-V1 film model were irradiated at the same position where the reference air kerma in air was measured by the PPIC. Irradiation was performed using the time scale method based on the load on the equipment. Two methods of irradiation were considered: placing the detector in air and on the phantom. The LD-V1 was scanned five times at 72 dpi in RGB (48 bit) mode using a flatbed scanner (ES-G11000, Seiko Epson Corp, Nagano, Japan) 24 h following irradiation. The response ratio of the reference air kerma and the air kerma obtained from the LD-V1 were compared and examined for each beam quality and air kerma range. Results and discussionWhen the beam quality was altered, the response ratio varied from 0.8 to 1.2 with respect to the measurement value of the PPIC; however, some outliers were observed. Response ratios were highly variable in the low-dose range; however, as the air kerma increased, the ratios approached 1. Thus, LD-V1 does not need calibration for each beam quality used in mammography. LD-V1 enables air kerma evaluation by creating air kerma response curves under certain X-ray conditions used in mammography. ConclusionWe suggest that the dose range be limited to 12 mGy or more to keep the response variation with beam qualities below ±20%. If further measurement is required for reducing the response variation, the dose range should be shifted to a higher dose range.

Review of nanomaterial advances for ionizing radiation dosimetry.

There are a wide range of applications with ionizing radiation and a common theme throughout these is that accurate dosimetry is usually required, although many newer demands are provided by improved features in higher range, multi-spectral and particle type detected. Today, the array of dosimeters includes both offline and online tools, such as gel dosimeters, thermoluminescence (TL), scintillators, optically stimulated luminescence (OSL), radiochromic polymeric films, gels, ionization chambers, colorimetry, and electron spin resonance (ESR) measurement systems. Several future nanocomposite features and interpretation of their substantial behaviors are discussed that can lead to improvements in specific features, such as (1) lower sensitivity range, (2) less saturation at high range, (3) overall increased dynamic range, (4) superior linearity, (5) linear energy transfer and energy independence, (6) lower cost, (7) higher ease of use, and (8) improved tissue equivalence. Nanophase versions of TL and ESR dosimeters and scintillators each have potential for higher range of linearity, sometimes due to superior charge transfer to the trapping center. Both OSL and ESR detection of nanomaterials can have increased dose sensitivity because of their higher readout sensitivity with nanoscale sensing. New nanocrystalline scintillators, such as perovskite, have fundamentally important advantages in sensitivity and purposeful design for key new applications. Nanoparticle plasmon coupled sensors doped within a lower Zeff material have been an effective way to achieve enhanced sensitivity of many dosimetry systems while still achieving tissue equivalency. These nanomaterial processing techniques and unique combinations of them are key steps that lead to the advanced features. Each must be realized through industrial production and quality control with packaging into dosimetry systems that maximize stability and reproducibility. Ultimately, recommendations for future work in this field of radiation dosimetry were summarized throughout the review.

Characterization of a diode dosimeter for UHDR FLASH radiotherapy.

Ultra-high dose rate (UHDR) FLASH beams typically deliver dose at rates of >40 Gy/sec. Characterization of these beams with respect to dose, mean dose rate, and dose per pulse requires dosimeters which exhibit high temporal resolution and fast readout capabilities. A diode EDGE Detector with a newly designed electrometer has been characterized for use in an UHDR electron beam and demonstrated appropriateness for UHDR FLASH radiotherapy dosimetry. Dose linearity, mean dose rate, and dose per pulse dependencies of the EDGE Detector were quantified and compared with dosimeters including a W1 scintillator detector, radiochromic film, and ionization chamber that were irradiated with a 10 MeV UHDR beam. The dose, dose rate, and dose per pulse were controlled via an in-house developed scintillation-based feedback mechanism, repetition rate of the linear accelerator, and source-to-surface distance, respectively. Depth-dose profiles and temporal profiles at individual pulse resolution were compared to the film and scintillation measurements, respectively. The radiation-induced change in response sensitivity was quantified via irradiation of ∼5kGy. The EDGE Detector agreed with film measurements in the measured range with varying dose (up to 70 Gy), dose rate (nearly 200 Gy/s), and dose per pulse (up to 0.63 Gy/pulse) on average to within 2%, 5%, and 1%, respectively. The detector also agreed with W1 scintillation detector on average to within 2% for dose per pulse (up to 0.78 Gy/pulse). The EDGE Detector signal was proportional to ion chamber (IC) measured dose, and mean dose rate in the bremsstrahlung tail to within 0.4% and 0.2% respectively. The EDGE Detector measured percent depth dose (PDD) agreed with film to within 3% and per pulse output agreed with W1 scintillator to within -6% to +5%. The radiation-induced response decrease was 0.4% per kGy. The EDGE Detector demonstrated dose linearity, mean dose rate independence, and dose per pulse independence for UHDR electron beams. It can quantify the beam spatially, and temporally at sub millisecond resolution. It's robustness and individual pulse detectability of treatment deliveries can potentially lead to its implementation for in vivo FLASH dosimetry, and dose monitoring.

Evaluation of a high resolution diode array for CyberKnife quality assurance.

The CyberKnife quality assurance (QA) program relies mainly on the use of radiochromic film (RCF). We aimed at evaluating high-resolution arrays of detectors as an alternative to films for CyberKnife machine QA. This study will test the SRS Mapcheck (Sun Nuclear, Melbourne, Florida, USA) diode array and its own software, which allows three tests of the CyberKnife QA program to be performed. The first one is a geometrical accuracy test based on the delivery of two orthogonal beams (Automated Quality Assurance, AQA). Besides comparing the constancy and repeatability of both methods, known errors will be introduced to check their sensitivity. The second checks the constancy of the iris collimator field sizes (Iris QA). Changes in the field sizes will be introduced to study the array sensitivity. The last test checks the correct positioning of the multileaf collimator (MLC). It will be tested introducing known systematic displacements to whole banks and to single leaves. The results of the RCF and diode array were equivalent (maximum differences of 0.18±0.14mm) for the AQA test, showing the array a higher reproducibility. When known errors were introduced, both methods behaved linearly with similar slopes. Regarding Iris QA, the array measurements are highly linear when changes in the field sizes are introduced. Linear regressions show slopes of 0.96-1.17 with r2 above 0.99 in all field sizes. Diode array seems to detect changes of 0.1mm. In MLC QA, systematic errors of the whole bank of leaves were not detected by the array, while single leaf errors were detected. The diode array is sensitive and accurate in the AQA and Iris QA tests, which give us the possibility of substituting RCF with a diode array. QA would be performed faster than using the film procedure, obtaining reliable results. Regarding the MLC QA, the inability to detect systematic displacements make it difficult to confidently use the detector.

Dosimetry using a radiochromic film and a mammography phantom.

Mammography is one of the most effective diagnostic methods for the early detection of breast cancer; however, it poses the risk of radiation exposure. To date, mammography dosimetry has been performed according to the mean glandular dose; however, the actual exposure in the breast has not been assessed. Here, we have measured dose distributions and depth doses using both radiochromic films and mammographic phantoms, and a three-dimensional intra-mammary dose assessment was conducted. The absorbed dose distribution at the surface was markedly higher on the chest wall side but lower on the nipple side. The absorbed doses in the depth direction exponentially decreased. The glandular tissue near the surface may be irradiated with an absorbed dose of 7.0mGy or higher. Since LD-V1 could be placed inside the phantom, the absorbed dose inside the breast could also be evaluated in three dimensions.

Clinical Characterization of a Table Mounted Range Shifter Board for Synchrotron-Based Intensity Modulated Proton Therapy for Pediatric Craniospinal Irradiation.

Purpose: To report our design, manufacturing, commissioning and initial clinical experience with a table-mounted range shifter board (RSB) intended to replace the machine-mounted range shifter (MRS) in a synchrotron-based pencil beam scanning (PBS) system to reduce penumbra and normal tissue dose for image-guided pediatric craniospinal irradiation (CSI). Methods: A custom RSB was designed and manufactured from a 3.5 cm thick slab of polymethyl methacrylate (PMMA) to be placed directly under patients, on top of our existing couch top. The relative linear stopping power (RLSP) of the RSB was measured using a multi-layer ionization chamber, and output constancy was measured using an ion chamber. End-to-end tests were performed using the MRS and RSB approaches using an anthropomorphic phantom and radiochromic film measurements. Cone beam CT (CBCT) and 2D planar kV X-ray image quality were compared with and without the RSB present using image quality phantoms. CSI plans were produced using MRS and RSB approaches for two retrospective pediatric patients, and the resultant normal tissue doses were compared. Results: The RLSP of the RSB was found to be 1.163 and provided computed penumbra of 6.9 mm in the phantom compared to 11.8 mm using the MRS. Phantom measurements using the RSB demonstrated errors in output constancy, range, and penumbra of 0.3%, -0.8%, and 0.6 mm, respectively. The RSB reduced mean kidney and lung dose compared to the MRS by 57.7% and 46.3%, respectively. The RSB decreased mean CBCT image intensities by 86.8 HU but did not significantly impact CBCT or kV spatial resolution providing acceptable image quality for patient setup. Conclusions: A custom RSB for pediatric proton CSI was designed, manufactured, modeled in our TPS, and found to significantly reduce lateral proton beam penumbra compared to a standard MRS while maintaining CBCT and kV image-quality and is in routine use at our center.

A radichromic dye of tris-(4-aminophenyl)methane incorporated into polymeric films for radiation dose monitoring

With the goal of developing new dyed film dosimeters for radiation technology applications, radiochromic films based on tris(4-aminophenyl)methane, a radiation-sensitive dye, have been studied for dose monitoring in the dose range of 0.5–25 kGy. A chlorine-containing material, hexachloroethane, was incorporated into these films to improve their radiation sensitivity. In addition, a UV-absorber of tinuvin-P were employed to protect these films from the influence of light during storage and measurements. Subjecting these films to γ-irradiation induces a significant magenta color characterized by an absorption band at 553 nm. The intensity of this band increases linearly as the absorbed dose increases up to 25 kGy and 10 kGy for compositions without and with HCE, respectively. The radiation sensitivity of the films incorporating 5.0 phr HCE is ∼2.4 times greater than that of films without HCE. The irradiated dyed films remain stable at 6 °C over two months in the dark. The responses of films are relatively independent of relative humidity in the 53–75% range and temperature in the 8–34 °C range. However, the films’ response is temperature dependent above 34 °C, thus it is advisable to calibrate these films under actual used conditions. The estimated absorbed doses using these films have an uncertainty (2σ) of 6.63%. In conclusion, the prepared dyed films may be good candidates for use as chemical dosimeters or indicators for applications involving radiation processing, such as food irradiation and medical sterilization.

Evaluation of dose perturbations around iodine-125 seed sources in supplemental external beam prostate radiotherapy.

We investigated dose perturbations caused by 125I seeds in patients undergoing supplemental external beam radiotherapy (EBRT) for prostate cancer. We examined two types of nonradioactive seed models: model 6711 and model STM1251. All experiments were performed using a water-equivalent phantom. Radiochromic film was used to measure the dose distributions adjacent to the seeds upstream and downstream of the external beam source. Single and clusters of multiple seeds were placed in slots in a solid water (SW) slab to measure dose perturbations with separate versus dense seed placement at beam energies of 6 or 10 MV. Monte Carlo simulations (MCSs) were also performed to include the theoretical basis against film dosimetry. Distinct patterns of dose enhancement (buildup [BU]) were upstream, and dose reduction (builddown [BD]) were downstream of the radiation source. Model 6711 with lower photon beam energies produced larger dose perturbations of BU and BD than the model STM1251. The results showed the same tendency with different seed placements and beam energies. However, these differences were not observed in the rotational irradiation measurement, which replicated a clinical plan. Dose perturbations around seeds result in dose enhancement and dose reduction with varying impact depending on the photon beam energy and seed type. This has the potential to cancel out these perturbations using multiple beam direction fields.

A tomographic reconstruction algorithm for cross-sectional imaging of IMRT beams from six projections

Objective. Patient-specific Quality Assurance (QA) measurements are of key importance in radiotherapy for safe and efficient treatment delivery and allow early detection of clinically relevant errors. Such QA processes remain challenging to implement for complex Intensity Modulated Radiation Therapy (IMRT) radiotherapy fields delivered using a multileaf collimator (MLC) which often feature small open segments and raise QA issues similar to those encountered in small field dosimetry. Recently, detectors based on long scintillating fibers have been proposed to measure a few parallel projections of the irradiation field with good performance for small field dosimetry. The purpose of this work is to develop and validate a novel approach to reconstruct MLC-shaped small irradiation fields from six projections. Approach. The proposed field reconstruction method uses a limited number of geometric parameters to model the irradiation field. These parameters are iteratively estimated with a steepest descent algorithm. The reconstruction method was first validated on simulated data. Real data were measured with a water-equivalent slab phantom equipped with a detector made of 6 scintillating-fiber ribbons placed at 1 m from the source. A radiochromic film was used to acquire a reference measurement of a first dose distribution in the slab phantom at the same source-to-detector distance and the treatment planning system (TPS) provided the reference for another dose distribution. In addition, simulated errors introduced on the delivered dose, field location and field shape were used to evaluate the ability of the proposed method to efficiently identify a deviation between the planned and delivered treatments. Main results. For a first small IMRT segment, 3%/3 mm, 2%/2 mm and 2%/1 mm gamma analysis conducted between the reconstructed dose distribution and the dose measured with radiochromic film exhibited pass rates of 100%, 99.9% and 95.7%, respectively. For a second and smaller IMRT segment, the same gamma analysis performed between the reconstructed dose distribution and the reference provided by the TPS showed pass rates of 100%, 99.4% and 92.6% for the 3%/3 mm, 2%/2 mm and 2%/1 mm gamma criteria, respectively. Gamma analysis of the simulated treatment delivery errors showed the ability of the reconstruction algorithm to detect a 3% deviation between the planned and delivered doses, as well as shifts lower than 7 mm and 3 mm when considering an individual leaf and a whole field shift, respectively. Significance. The proposed method allows accurate tomographic reconstruction of IMRT segments by processing projections measured with six scintillating-fiber ribbons and is suitable for water-equivalent real-time small IMRT segments QA.

Clinical Linear Accelerator-Based Electron FLASH: Pathway for Practical Translation to FLASH Clinical Trials

Ultrahigh-dose-rate (UHDR) radiation therapy (RT) has produced the FLASH effect in preclinical models: reduced toxicity with comparable tumor control compared with conventional-dose-rate RT. Early clinical trials focused on UHDR RT feasibility using specialized devices. We explore the technical feasibility of practical electron UHDR RT on a standard clinical linear accelerator (LINAC). We tuned the program board of a decommissioned electron energy for UHDR electron delivery on a clinical LINAC without hardware modification. Pulse delivery was controlled using the respiratory gating interface. A short source-to-surface distance (SSD) electron setup with a standard scattering foil was configured and tested on an anthropomorphic phantom using circular blocks with 3- to 20-cm field sizes. Dosimetry was evaluated using radiochromic film and an ion chamber profiler. UHDR open-field mean dose rates at 100, 80, 70, and 59 cm SSD were 36.82, 59.52, 82.01, and 112.83 Gy/s, respectively. At 80 cm SSD, mean dose rate was ∼60 Gy/s for all collimated field sizes, with an R80 depth of 6.1 cm corresponding to an energy of 17.5 MeV. Heterogeneity was <5.0% with asymmetry of 2.2% to 6.2%. The short SSD setup was feasible under realistic treatment conditions simulating broad clinical indications on an anthropomorphic phantom. Short SSD and tuning for high electron beam current on a standard clinical LINAC can deliver flat, homogenous UHDR electrons over a broad, clinically relevant range of field sizes and depths with practical working distances in a configuration easily reversible to standard clinical use.

Clinical radiation dose verification by topographic persistent luminescence dosimetry

Radiation dose verification in radiotherapy is essential to determine the dose delivered to irradiated tissue while minimizing normal tissue toxicity. However, the challenge remains in determining topographic radiation dose profiles due to limitations in conventional dosimeters. Herein, we report a robust technique for visualizing and verifying clinical doses based on reusable, flexible scintillating films comprising lanthanide-doped persistent luminescent nanoparticles. These nanoparticle-based films outperform commercially available radiochromic films in terms of linear response to irradiation doses between 0 and 25 Gy. We demonstrate topographic persistent luminescence dosimetry for radiotherapy of mice and rabbits with malignant tumors. Our data show a higher signal-to-background ratio, especially at lower (<0.1 Gy) and higher (>10 Gy) X-ray doses. We also demonstrate that topographic persistent luminescence dosimetry can record complex clinical dose distributions for dose verification and radiotherapy planning.

Application of a Portable Colorimeter for Reading a Radiochromic Film for On-Site Dosimetry

Radiochromic films have widely been used for quality assurance (QA) in radiation therapy and have many advantageous features such as self-developing visible coloration, wide dose range and easiness to handle. These features have a good potential for application to other fields associated with high-dose radiation exposure, e.g., verification of various radiation sources used in industry and research, occupational radiation monitoring as a preparedness for radiological emergencies. One of the issues in such applications is the elaborate process of acquisition and analyses of the color image using a flatbed scanner and image processing software, which is desirably to be improved for achieving a practical on-site dosimetry. In the present study, a simple method for reading a radiochromic film by using a portable colorimeter (nix pro 2; abbreviated here “Nix”) was proposed and its feasibility for diagnostic X-rays was tested with a commercial radiochromic film (Gafchromic EBT-XD). It was found that the color intensities of red and green components of EBT-XD were successfully measured by Nix over a wide dose range up to 40 Gy. Though some angle dependence was observed, this error could be well averted by careful attention to the film direction in a reading process. According to these findings, it is expected that the proposed on-site dosimetry method of combining a radiochromic film and a portable colorimeter will be practically utilized in various occasions.

Development and characterization of modular mouse phantoms for end-to-end testing and training in radiobiology experiments

Objective. In radiation oncology, experiments are often carried out using mice as a model for in vivo research studies. Due to recent technological advances in the development of high-precision small-animal irradiation facilities, the importance of quality assurance for both dosimetry and imaging is increasing. Additive manufacturing (AM) offers the possibility to produce complex models from a three-dimensional data set and to build cost-effective phantoms that can easily be adapted to different purposes. The aim of this work was therefore to develop detailed anatomical mouse models for quality assurance and end-to-end testing of small-animal irradiation and imaging by means of AM. Approach. Two mouse phantom concepts were designed, constructed, and examined for this purpose. The first model includes cavities corresponding to the most important organs. The final solid model was constructed using AM in two separate parts that can be attached with a plug connection after filling these cavities with tissue-equivalent mixtures. Moreover, different radiation dosimeters can be placed in the lower part of the model. For the second concept, AM was used for building modules like the phantom outer shell and bones, so that different mixtures can be used as a filling, without modifying the phantom structure. Main results. CT as well as Micro-CT scans of both concepts showed an excellent quality and adequate image contrast, with material attenuation properties close to those of mouse tissues, apart from the current bone surrogates. Radiation dose measurements with radiochromic films were, with some exceptions in areas with larges bone volumes, in agreement with calculations within less than ±4%. Significance. AM shows great potential for the development of mouse models that are inexpensive, easy to adapt, and accurate, thus enabling their use for quality assurance in small-animal radiotherapy and imaging. The introduction of such 3D-printable mouse phantoms in the workflow could also significantly reduce the use of living animals for optimization and testing of new imaging and irradiation protocols.