Dose Calibration Research Articles

Evaluation of Fused Deposition Modeling Materials for 3D-Printed Container of Dosimetric Polymer Gel.

Accurate dosimetric verification is becoming increasingly important in radiotherapy. Although polymer gel dosimetry may be useful for verifying complex 3D dose distributions, it has limitations for clinical application due to its strong reactivity with oxygen and other contaminants. Therefore, it is important that the material of the gel storage container blocks reaction with external contaminants. In this study, we tested the effect of air and the chemical permeability of various polymer-based 3D printing materials that can be used as gel containers. A methacrylic acid, gelatin, and tetrakis (hydroxymethyl) phosphonium chloride gel was used. Five types of printing materials that can be applied to the fused deposition modeling (FDM)-type 3D printer were compared: acrylonitrile butadiene styrene (ABS), co-polyester (CPE), polycarbonate (PC), polylactic acid (PLA), and polypropylene (PP) (reference: glass vial). The map of R2 (1/T2) relaxation rates for each material, obtained from magnetic resonance imaging scans, was analyzed. Additionally, response histograms and dose calibration curves from the R2 map were evaluated. The R2 distribution showed that CPE had sharper boundaries than the other materials, and the profile gradient of CPE was also closest to the reference vial. Histograms and dose calibration showed that CPE provided the most homogeneous and the highest relative response of 83.5%, with 8.6% root mean square error, compared with the reference vial. These results indicate that CPE is a reasonable material for the FDM-type 3D printing gel container.

EPR dosimetry of biohydroxyapatite below liquid nitrogen temperature

Hydroxyapatite, major component of all organic solid tissues, can be used as a sensitive biodosimeter based on the electron paramagnetic resonance (EPR) spectroscopy. However, the dosimetric signal of biohydroxyapatite overlaps with the so-called parasitic signals due to the close g factor values and broadening of the resonance line at room temperature. Moreover, the unsaturated parasitic signals possess the intensity comparable to the dosimetric resonance. All of these significantly complicates the dose determination and limits applicability mainly to the cases of relatively large accumulated dose. The negligibly saturated dosimteric spectrum can be at least partially separated at the liquid nitrogen temperatures (LNT) due to the strong saturation and suppression of the parasitic resonance lines and the linewidth shortening as shown in the present work. Moreover, the advances in the modern EPR equipment in the last two decades resulted in high sensitivity and stability of the signals measured. These are the key parameters along with the computer simulations for the precise dosimetric spectrum separation and processing. This could lead to the higher accuracy of the LNT EPR method proposed in the present work. To test the approach, the stepwise dose calibration of biohydroxyapatite over the range 0.5 - 20 Gy was made. The corresponding dosimetric signal measured at 70 K exhibited the linear dose response. The results suggest the applicability of the LNT EPR method in the retrospective dosimetry.

A preliminary study of multispectral Cherenkov imaging and a Fricke-xylenol orange gel film (MCIFF) for online, absolute dose measurement.

Cherenkov luminescence imaging has shown potential for relative dose distribution and field verification in radiation therapy. However, to date, limited research utilizing Cherenkov luminescence for absolute dose calibration has been conducted owing to uncertainties arising from camera positioning and tissue surface optical properties. This paper introduces a novel approach to multispectral Cherenkov luminescence imaging combined with Fricke-xylenol orange gel (FXG) film, termed MCIFF, which can enable online full-field absolute dose measurement. By integrating these two approaches, MCIFF allows for calibration of the ratio between two spectral intensities with absorbed dose, thereby enabling absolute dose measurement. All experiments are conducted on a Varian Clinac 23EX, utilizing an electron multiplying charge-coupled device (EMCCD) camera and a two-way image splitter for simultaneous capture of two-spectral Cherenkov imaging. In the first part of this study, the absorbance curves of the prepared FXG film, which receives different doses, are measured using a fluorescence spectrophotometer to verify the correlation between absorbance and dose. In the second part, the FXG film is positioned directly under the radiation beam to corroborate the dose measurement capacity of MCIFF across various beams. In the third part, the feasibility of MCIFF is tested in actual radiotherapy settings via a humanoid model, demonstrating its versatility with various radiotherapy materials. The results of this study indicate that the logarithmic ratios of spectral intensities at wavelengths of 550±50 and 700±100nm accurately reflect variations in radiation dose (R2>0.96) across different radiation beams, particle energies, and dose rates. The slopes of the fitting lines remain consistent under varying beam conditions, with discrepancies of less than 8%. The optical profiles obtained using the MCIFF exhibit a satisfactory level of agreement with the measured results derived from the treatment planning system (TPS) and EBT3 films. Specifically, for photon beams, the lateral distances between the 80% and 20% isodose lines, referred to as the penumbra (P80-20) values, obtained through TPS, EBT3 films, and MCIFF, are determined as 0.537, 0.664, and 0.848cm, respectively. Similarly, for electron beams, the P80-20 values obtained through TPS, EBT3 films, and MCIFF are found to be 0.432, 0.561, and 0.634cm, respectively. Furthermore, imaging of the anthropomorphic phantom demonstrates the practical application of MCIFF in real radiotherapy environments. By combining an FXG film with Cherenkov luminescence imaging, MCIFF can calibrate Cherenkov luminescence to absorbed dose, filling the gap in online 2D absolute dose measurement methods in clinical practice, and providing a new direction for the clinical application of optical imaging to radiation therapy.

Analysis of Precision and Stability Tests of the Doce Calibrator CRC-25R


 
 
 
 Dose calibrator is a measuring tool that is widely used in hospitals to determine radionuclide activity in nuclear medicine services. In determining this activity it has several factors; namely precision, accuracy and stability which is become depining factor of the tool suitability. The aim of this research is to determine the level of precision, accuracy and stability of the Capintec dose calibrator type CRC-25R with an I-131 source and a standar Cs-137 source at the Nuklear Medicine Installation of RSUD A.W. Sjahranie Hospital Samarinda. Data processing in this research was carried out using quantitative analysis tecnhniques, namely descriptive statistics. This analysis technique use primary data obtained from direct measurements of radionuclide activity. Data processing was carried out by measuring radionuclide activity, namely source I-131 and standard source Cs-137 of 0,1 ml using a Capintec type CRC-25R for 7 days. These results are visualized in the form of tables and graphs of precision, accuracy and stability tests from both source with predetermined limits. Base on this research, it can be concluded that if we look at the precision, accuracy, and stability test using I-131 source anda Cs-137 standard source on the Capintec type CRC-25R at A. W. Sjahranie Samarinda Hospital, it can be used to measure a constant source over a long periode of Long time.
 
 
 
 

The Impact of Dose Calibration Point Differences Between the Treatment Plan and Patient-specific Quality Assurance in Passive Scattering Proton Beam Therapy.

Passive scattering proton beam therapy (PSPT) is performed by taking actual measurements of all pre-designated fields in a treatment plan followed by appropriate adjustments to the prescribed dose. For this reason, it is necessary to ensure precision management of the measurements (patient-specific calibration) in the administration of a planned dose. Therefore, this study investigated the impact on dose distribution in treatment planning when the patient calibration point differs from the normalized point in a treatment plan. A total of 16 cases were selected, where the patient calibration point and normalized point did not match, and the normalized point used in the treatment plan was changed to the patient calibration point using a treatment planning system (VQA ver. 2.01, HITACHI). At this point, the displacement of the relative dose at the isocenter was estimated as an error owing to the difference compared to the patient calibration point. Overall, the error was within the range of ±1.5%, with the exception of orbit cases. Calibrated points also tended to be lower than the normalized points in the treatment plan. In terms of treatment sites, a greater deviation was observed for head cases. Cases with a large deviation in sites other than the head were attributed to poor flatness within the radiation field owing to a narrower opening of the patient collimator. Dose measurement errors in PSPT due to differing calibration points were generally within ±1.5%, with higher deviations observed in head treatments because of complex structures and narrow collimator openings. A γ analysis for significant deviations showed a 98.7% passing rate, suggesting limited overall impact. It is important to select stable calibration points in dosimetry to ensure high precision in dose administration, particularly in complex treatment areas.

Accuracy of Injection Dose of Amyloid PET Agent Using Radiopharmaceutical Activity Suppliers

This study aimed to identify disposable items with low amyloid positron emission tomography (PET) agent radioactivity adsorption for accurate injections using a radiopharmaceutical activity supplier. First, we investigated disposable items currently used for amyloid PET agent injection. Next, we measured the residual radioactivity rates of amyloid PET agents on three-way stopcocks, extension tubes, butterfly needles, and indwelling needles to identify disposable items with low radioactivity adsorption. Finally, we evaluated the accuracy of amyloid PET agent injection using the selected disposable items and a radiopharmaceutical activity supplier. The polybutadiene extension tube exhibited a significantly lower residual activity rate than that of the polyvinyl chloride extension tube. Similarly, the indwelling needles showed significantly lower residual activity rate than that of butterfly needles. The dose indicated by a radiopharmaceutical activity supplier was 184.1 MBq, while the dose calibrator measured the radioactivity which flowed into the vial as 170.2 MBq, resulting in an administration accuracy of 8.2%. To ensure accurate amyloid PET agent injections, we recommend using polybutadiene extension tubes and indwelling needles due to their lower radioactivity adsorption.

Determination of Exposure during Handling of <sup>125</sup>I Seed Using Thermoluminescent Dosimeter and Monte Carlo Method Based on Computational Phantom

Background: The thermoluminescent dosimeter (TLD) and Monte Carlo (MC) dosimetry are carried out to determine the occupational dose for personnel in the handling of <sup>125</sup>I seed sources.Materials and Methods: TLDs were placed in different layers of the Alderson-Rando phantom in the thyroid, lung and also eyes and skin surface. An <sup>125</sup>I seed source was prepared and its activity was measured using a dose calibrator and was placed at two distances of 20 and 50 cm from the Alderson-Rando phantom. In addition, the Monte Carlo N-Particle Extended (MCNPX 2.6.0) code and a computational phantom with a lattice-based geometry were used for organ dose calculations.Results and Discussion: The comparison of TLD and MC results in the thyroid and lung is consistent. Although the relative difference of MC dosimetry to TLD for the eyes was between 4% and 13% and for the skin between 19% and 23%, because of the existence of a higher uncertainty regarding TLD positioning in the eye and skin, these inaccuracies can also be acceptable. The isodose distribution was calculated in the cross-section of the head phantom when the <sup>125</sup>I seed was at two distances of 20 and 50 cm and it showed that the greatest dose reduction was observed for the eyes, skin, thyroid, and lungs, respectively. The results of MC dosimetry indicated that for near the head positions (distance of 20 cm) the absorbed dose rates for the eye lens, eye and skin were 78.1±2.3, 59.0±1.8, and 10.7±0.7 µGy/mCi/hr, respectively. Furthermore, we found that a 30 cm displacement for the <sup>125</sup>I seed reduced the eye and skin doses by at least 3- and 2-fold, respectively.Conclusion: Using a computational phantom to monitor the dose to the sensitive organs (eye and skin) for personnel involved in the handling of <sup>125</sup>I seed sources can be an accurate and inexpensive method.

Determination of the Re-188 Calibration Number for the Capintec CRC- 25PET Dose Calibrator.

During the development of novel Re-188 radiopharmaceuticals, it was discovered that no calibration settings were published to calibrate Re-188 on the Capintec CRC-25PET dose calibrator. Sodium [188Re]perrhenate was eluted from an OncoBeta 188W/188Re generator to measure activity on a Capintec CRC-25R dose calibrator using established dose calibrator settings provided by the manufacturer. The eluent was then used to tune the calibra on settings on a Capintec CRC-25PET dose calibrator, accounting for geometry. Radionuclidic purity of the [188Re]perrhenate source was verified via gamma spectroscopy. The calibrator number for Re-188 was determined to be 469 x 10 for the Capintec CRC-25PET dose calibrator, which differed from the manufacturer provided calibra on number of 496 x 10 for the Capintec CRC-25R dose calibra on model. W-188 breakthrough was characterised as < 0.01%. This previously unreported calibration number can be used to determine the activity of Re- 188 labelled radiopharmaceuticals using the Capintec CRC-25PET dose calibrator model.

Investigation of the Dosimetry Characteristics of the GAFCHROMIC® EBT3 Film Response to Alpha Particle Irradiation

The purpose of this study was to investigate the dosimetric characteristics of the GAFCHROMIC® EBT3 film responding to alpha particle irradiation. Unlaminated GAFCHROMIC® EBT3 film pieces, were irradiated with a 30.055 kBq 241Am alpha source, at eight different dose levels, between 0 and 509 Gy. The irradiations were performed inside an enclosed box. Epson Expression 10000 XL scanner in transmission mode was used to digitize irradiated films 24 hours post-irradiations as 16-bit RGB images in tagged image file format (TIFF). Optical density (OD) values were obtained by following the OD theorem. Raw and normalized pixel values (PVnorm) from the red, green, and blue colour channels were sampled from a 3 × 3 mm2 region of interest. Calibration curves were created for both data sets (OD and PVnorm) and were fit accordingly. Monte Carlo simulations with the Geant4 toolkit were performed to establish a dose rate at the point within the sensitive layer of the film. An alpha dosimetry protocol for EBT3 films was obtained from the Monte Carlo calculated dose rate and dose calibration curves for alpha radiation were created. It is necessary to extend this study for different film types and compare to photon dosimetry calibration curves.

AAPM Medical Physics Practice Guideline 14.a: Yttrium-90 microsphere radioembolization.

Radioembolization using Yttrium-90 (90 Y) microspheres is widely used to treat primary and metastatic liver tumors. The present work provides minimum practice guidelines for establishing and supporting such a program. Medical physicists play a key role in patient and staff safety during these procedures. Products currently available are identified and their properties and suppliers summarized. Appropriateness for use is the domain of the treating physician. Patient work up starts with pre-treatment imaging. First, a mapping study using Technetium-99m (Tc-99m ) is carried out to quantify the lung shunt fraction (LSF) and to characterize the vascular supply of the liver. An MRI, CT, or a PET-CT scan is used to obtain information on the tumor burden. The tumor volume, LSF, tumor histology, and other pertinent patient characteristics are used to decide the type and quantity of 90 Y to be ordered. On the day of treatment, the appropriate dose is assayed using a dose calibrator with a calibration traceable to a national standard. In the treatment suite, the care team led by an interventional radiologist delivers the dose using real-time image guidance. The treatment suite is posted as a radioactive area during the procedure and staff wear radiation dosimeters. The treatment room, patient, and staff are surveyed post-procedure. The dose delivered to the patient is determined from the ratio of pre-treatment and residual waste exposure rate measurements. Establishing such a treatment modality is a major undertaking requiring an institutional radioactive materials license amendment complying with appropriate federal and state radiation regulations and appropriate staff training commensurate with their respective role and function in the planning and delivery of the procedure. Training, documentation, and areas for potential failure modes are identified and guidance is provided to ameliorate them.

Development of Inclined Applicators for Flattened Beam Intraoperative Radiotherapy

A 3D-printed applicator for intraoperative radiation therapy (IORT) using the INTRABEAM system has been introduced, designed to protect normal tissue, expand indications, and assess its effectiveness in various intraoperative settings. The study involved designing and creating inclined applicators at 0° and 45° angles, which were capable of producing flattened and unflattened beams and shielding non-target areas from radiation. The applicator was evaluated based on dose uniformity, percentage depth dose, leakage, and dose rate. The findings showed that the applicator provided a uniform beam at various depths (1.23 to 1.30 for the flattened beam and 1.25 to 1.32 for the unflattened beam) and effectively shielded against leakage, with no leakage dose measured at 1 mm from the surface. Additionally, the dose rates after 3 min of irradiation for flattened and unflattened beams were 51.0 and 52.9 cGy for 0° and 48.5 and 54.8 cGy for 45° applicators, respectively. This suggests that the applicator can efficiently deliver IORT while minimizing exposure to normal tissues, particularly in treating chest and abdominal lesions near or on critical organs. The applicator has undergone dose calibration and has moved forward to clinical application.

DOSE MAP BLOOD IRRADIATOR DOSIMETRY SYSTEM: CUSTOMIZED BLOOD EQUIVALENT PHANTOM AND GAFCHROMIC EBT-XD FILM

Blood irradiation is done to sterilize and cease donor T-lymphocytes functionality to avoid Transfusion Associated-Graft Versus Host Disease (TA-GVHD). Dose mapping is the primary means of ensuring that the irradiation process is being conducted correctly. The aim of this study is to measure the minimum, maximum and central absorbed gamma radiation dose delivered at the newly customized blood equivalent phantom using a Gafchromic EBT-XD film. A Gammacell 3000 Elan Blood Irradiator with Cesium-137 source was used. To obtain the dose calibration curves, the films were placed at the center of a phantom and irradiated with the dose range from 5 Gy to 35 Gy with one unirradiated film as a control. The dose calibration curve was plotted using red, green and blue channels. While, for the dose mapping measurement, the irradiation exposure of 9.03 minutes was used to deliver a central dose of 25 Gy to the film. The response of the film will be compared with the GC Dose Mapping Report 2022 which used a water equivalent medium as a phantom. For the calibration curve, the red channel of the film was utilized in this study as it had a higher signal than the other channel. The doses obtained at central, minimum and maximum using EBT-XD film with customized blood equivalent phantom were in agreement with that obtained from GC Dose Mapping Report 2022 to be within ±7.6%, ±8.51% and ±9.95% respectively. We concluded that the customized blood equivalent phantom together with EBT-XD film has a potential to map the dose in blood irradiator accurately. The doses obtained from EBT-XD film were in the range of doses needed to inhibit the proliferation of the T-lymphocytes with central, minimum and maximum doses were 26.9 Gy, 17.2 Gy and 35.7 Gy respectively.

A mathematical model to identify the output variations of TrueBeam linear accelerators using Machine Performance Check evaluations

The aim of this work is to find an effective mathematical model to identify the output variations of TrueBeam (Varian Medical Systems, Palo Alto, CA, U.S.A.) linear accelerators (Linacs), using the daily output measurements performed with Machine Performance Check (MPC) tool. All daily output data, measured with MPC from July 2020 to October 2021, were exported and plotted for all energies investigated. After identifying the dates of dose calibration, the measurement period was divided into four and three sub-periods for photon and electron beams, respectively, common to the three Linacs; straight lines were applied to the data and slopes were analysed. Finally, all the output data were merged and a parameters optimisation process was performed that minimised the differences between output values measured by MPC and output values calculated by model. The output of Linacs under examination showed an increase for all photon and electron energies in agreement with the literature findings. MPC output trends were well represented by means of a linear mathematical model and the angular coefficients of the regression lines characterized the rate of daily output increase. The optimisation of the model provided an optimised angular coefficient for photon (0.0126% per day) and electron (0.0128% per day) beams. In this study, linear regression analysis is used to identify the TrueBeam output drift. The proposed model fitting daily MPC output data allows to define the right timing for preventive beams calibrations offering a tool to improve dose control.

Dose Calibrator Measurements in the Case of Voltage Fluctuations

Radiation dose measurements of radiopharmaceuticals and measurements of dose calibrators at different voltages and fluctuations were evaluated. Low and high doses of technetium, iodine and fluorine pharmaceuticals were measured in different voltages. The results showed that only low doses could make small and insignificant differences.

Electron beam detection in radiotherapy using a capacitor dosimeter equipped with a silicon photodiode.

In this study, a newly developed capacitor dosimeter was evaluated using electron beams commonly utilized in radiotherapy. The capacitor dosimeter comprised a silicon photodiode, 0.47-μF capacitor, and dedicated terminal (dock). Before electron beam irradiation, the dosimeter was charged using the dock. The doses were measured without using a cable by reducing the charging voltages using the currents from the photodiode during irradiation. A commercially available parallel-plane-type ionization chamber and solid-water phantom were used for dose calibration with an electron energy of 6MeV. In addition, the depth doses were measured using a solid-water phantom at electron energies of 6, 9, and 12MeV. The doses were proportional to the discharging voltages, and the maximum dose difference in the calibrated doses measured using a two-point calibration was approximately 5% in the range of 0.25-1.98Gy. The depth dependencies at energies of 6, 9, and 12MeV corresponded to those measured using the ionization chamber.

A Machine-Vision Approach to Transmission Electron Microscopy Workflows, Results Analysis and Data Management.

Transmission electron microscopy (TEM) enables users to study materials at their fundamental, atomic scale. Complex experiments routinely generate thousands of images with numerous parameters that require time-consuming and complicated analysis. AXON synchronicity is a machine-vision synchronization (MVS) software solution designed to address the pain points inherent to TEM studies. Once installed on the microscope, it enables the continuous synchronization of images and metadata generated by the microscope, detector, and in situ systems during an experiment. This connectivity enables the application of machine-vision algorithms that apply a combination of spatial, beam, and digital corrections to center and track a region of interest within the field of view and provide immediate image stabilization. In addition to the substantial improvement in resolution afforded by such stabilization, metadata synchronization enables the application of computational and image analysis algorithms that calculate variables between images. This calculated metadata can be used to analyze trends or identify key areas of interest within a dataset, leading to new insights and the development of more sophisticated machine-vision capabilities in the future. One such module that builds on this calculated metadata is dose calibration and management. The dose module provides state-of-the-art calibration, tracking, and management of both the electron fluence (e-/Å2·s-1) and cumulative dose (e-/Å2) that is delivered to specific areas of the sample on a pixel-by-pixel basis. This enables a comprehensive overview of the interaction between the electron beam and the sample. Experiment analysis is streamlined through a dedicated analysis software in which datasets consisting of images and corresponding metadata are easily visualized, sorted, filtered, and exported. Combined, these tools facilitate efficient collaborations and experimental analysis, encourage data mining and enhance the microscopy experience.

The evaluation of an on-site monitoring program for activity meter quality assurance with exemption-level sources

This paper discusses the feasibility of a monitoring program for the quality assurance status of activity meters. We sent a questionnaire to clinical nuclear medicine departments of medical institutions, requesting information on their activity meters and quality assurance practices. On-site visits were conducted with exemption-level standard sources (Co-57, Cs-137 and Ba-133) for dose calibrators in nuclear medicine departments including physical inspection, accuracy and reproducibility. A method offering a quick check on the detection efficiency of the space dimension inside the activity meters was also introduced. For dose calibrator quality assurance, the daily checks had the highest implementation. However, annual checks and upon acceptance/after a repair check were reduced to 50% and 44%, respectively. The accuracy results of dose calibrators showed that all models exceeded the ±10% criteria with Co-57 and Cs-137 sources. The reproducibility results showed that some models exceeded the ±5% criteria with Co-57 and Cs-137 sources. The appropriate application of exemption-level standard sources considering the uncertainty that affects the measurement is discussed.

Automated radiosynthesis of [89Zr]Zr-DFOSq-Durvalumab for imaging of PD-L1 expressing tumours in vivo

Objectives89Zr-labelled proteins are gaining importance in clinical research in a variety of diseases. To date, no clinical study has been reported that utilizes an automated approach for radiosynthesis of 89Zr-labelled radiopharmaceuticals. We aim to develop an automated method for the clinical production of 89Zr-labelled proteins and apply this method to Durvalumab, a monoclonal antibody targeting PD-L1 immune-checkpoint protein. PD-L1 expression is poorly understood and can be up-regulated over the course of chemo- and radiotherapy treatment. The ImmunoPET multicentre study aims to examine the dynamics of PD-L1 expression via 89Zr-Durvalumab PET imaging before, during, and after chemoradiotherapy. The developed automated technique will enable reproducible clinical production of [89Zr]Zr-DFOSq-Durvalumab for this study at three different sites. MethodsConjugation of Durvalumab to H3DFOSqOEt was optimized for optimal chelator-to-antibody ratio. Automated radiolabelling of H3DFOSq-Durvalumab with zirconium-89 was optimized on the disposable cassette based iPHASE technologies MultiSyn radiosynthesizer using a modified cassette. Activity losses were tracked using a dose calibrator and minimized by optimizing fluid transfers, reaction buffer, antibody formulation additives and pH. The biological profile of the radiolabelled antibody was confirmed in vivo in PD-L1+ (HCC827) and PD-L1- (A549) murine xenografts. Clinical process validation and quality control were performed at three separate study sites to satisfy clinical release criteria. ResultsH3DFOSq-Durvalumab with an average CAR of 3.02 was obtained. Radiolabelling kinetics in succinate (20 mM, pH 6) were significantly faster when compared to HEPES (0.5 M, pH 7.2) with >90 % conversion observed after 15 min. Residual radioactivity in the 89Zr isotope vial was reduced from 24 % to 0.44 % ± 0.18 % (n = 7) and losses in the reactor vial were reduced from 36 % ± 6 % (n = 4) to 0.82 % ± 0.75 % (n = 4) by including a surfactant in the reaction and formulation buffers. Overall process yield was 75 % ± 6 % (n = 5) and process time was 40 min. Typically, 165 MBq of [89Zr]Zr-DFOSq-Durvalumab with an apparent specific activity of 315 MBq/mg ± 34 MBq/mg (EOS) was obtained in a volume of 3.0 mL. At end-of-synthesis (EOS), radiochemical purity and protein integrity were always >99 % and >96 %, respectively, and dropped to 98 % and 65 % after incubation in human serum for 7 days at 37 °C. Immunoreactive fraction in HEK293/PD-L1 cells was 83.3 ± 9.0 (EOS). Preclinical in vivo data at 144 h p.i. showed excellent SUVmax in PD-L1+ tumour (8.32 ± 0.59) with a tumour-background ratio of 17.17 ± 3.96. [89Zr]Zr-DFOSq-Durvalumab passed all clinical release criteria at each study site and was deemed suitable for administration in a multicentre imaging trial. ConclusionFully automated production of [89Zr]Zr-DFOSq-Durvalumab for clinical use was achieved with minimal exposure to the operator. The cassette-based approach allows for consecutive productions on the same day and offers an alternative to currently used manual protocols. The method should be broadly applicable to other proteins and has the potential for clinical impact considering the growing number of clinical trials investigating 89Zr-labelled antibodies.

Hot or not? Investigating radiation safety and policy updating for the appropriate storage of radioactive specimens at Mount Sinai Hospital

PurposeThe current hospital policy for this study is stringent regarding the storage of radioactive sentinel lymph node (SLN) specimens, which requires the storage time of 24 hours before being handled by Pathology. Additional labeling along with separate containment of these specimens can be forgone if negligible radiation levels are found. The objective of this study was to determine whether the storage time needed for resected radioactive breast and primary site specimens to decay to twice the background radiation levels is less than 24 hours. MethodsThe investigators retrieved breast and primary site SLN specimens from the Pathology department on the same day of the biopsy. A dose calibrator was used to measure the dose, specimen, and concurrent background radioactivity in Megabecquerels (MBq). Radioactive decay calculations were used to further investigate when specimen activities reached twice the background levels. A retrospective analysis was performed using a one-sample t-test to determine if the time to reach double the background activity was significantly different from 24 hours. This study pertained to workflow optimization; thus, general procedure consent forms were sufficient. Both patient confidentiality and privacy were protected. The investigators followed the necessary radiation safety measures. ResultsThe mean time for specimens to reach twice the background level of radioactivity was 3.99 hours, significantly less than current storage time of 24 hours (p < 0.001). The mean time point for the SLNs to reach 1/16th of the original activity was 7.78 hours (p < 0.001). The average node activity was 0.14 MBq. ConclusionThe average sentinel node activity was less than 1 exemption quantity and the time to reach less than twice the background levels was significantly less than 24 hours, meaning that radioactive labels are not needed, and the 24-hour overnight specimen storage can be mitigated.

Low radiation dose calibration and theoretical model of an optical fiber dosimeter for the International Space Station.

The optical-fiber-based dosimeter of the LUMINA project was deployed in August 2021 in the International Space Station in the framework of the Alpha mission. The sensing elements of the dosimeter are P-doped optical fibers, which were proven to be excellent candidates for dosimetry applications. The twofold objective of this paper is to provide a theoretical model for the radiation response of the dosimeter and to report on the experimental work carried out at CERN for the qualification and calibration of the engineering model of the LUMINA dosimeter. Combining the theoretical response and experimental data, the calibration curve of the flight model is obtained. Finally, this study broadens the investigation of the room temperature radiation response of P-doped optical fibers in a range of dose rates 104 times lower than previously reported, from 21µGy(SiO2)/h to145mGy(SiO2)/h.