Dosimetry Results Research Articles

Науково-методичні засади реабілітації радіоактивно забруднених агроландшафтів у контексті зеленої економіки

Goal. To outline the scientific and methodological principles of rehabilitation of radioactively contaminated agricultural landscapes of Ukrainian Polissia in the context of the European Green Course, taking into account modern environmental and socio-economic characteristics of the region to ensure full integration of the state into the European space. Methods. System analysis and synthesis; generally accepted methods of descriptive and variational statistics, as well as identification of the function of dose distribution of irradiation of the population was used for data processing and analysis. Statistical processing of dosimetry results and analysis of experimental data was performed using OriginPro 9 and Microsoft Excel 2016. Results. During the 35 years after the Chernobyl accident, the area, which was contaminated with radionuclides and the levels of radiation, especially with 137Cs and 90Sr, has decreased significantly — almost halved — as evidenced by radiological research data from research institutions. The results of a fragmentary radiological survey of agricultural and forest lands, as well as dosimetric control of the population indicate the need for large-scale radioecological monitoring. Conclusions. Radioactive contamination of the agricultural landscapes of Ukrainian Polissia against the background of the need for comprehensive rehabilitation of the region is one of the serious problems of Ukraine in implementing the points of the strategy “From farm to fork” in the European Green Course. The situation in radioactively contaminated agricultural landscapes, in particular the level of radiation contamination of agricultural products, is complex and complicated not only by purely radioecological, but also by other factors, including peculiarities of natural and climatic conditions, soil cover, material and technical characteristics of farms, and as the result, economic development of the region, as well as many social components, etc. The development of agricultural production in these areas should be based on a scientifically sound strategy and recommendations aimed at minimizing radiation doses to the population of Ukraine and focusing on biologically and environmentally friendly measures.

Reference dosimetry for inter-laboratory comparison on retrospective dosimetry techniques in realistic field irradiation experiment using 192Ir

The Korea Retrospective Dosimetry network (KREDOS) performed an inter-laboratory comparison to confirm the harmonization and reliability of the results of retrospective dosimetry using mobile phone. The mobile phones were exposed to 192Ir while attached to the human phantoms in the field experiment, and the exposure doses read by each laboratory were compared. This paper describes the reference dosimetry performed to present the reference values for inter-comparison and to obtain additional information about the dose distribution. Reference dosimetry included both measurement using LiF:Mg,Cu,Si and calculation via MCNP simulation to allow a comparison of doses obtained with the two different methodologies. When irradiating the phones, LiF elements were attached to the phones and phantoms and irradiated at the same time. The comparison results for the front of the phantoms were in good agreement, with an average relative difference of about 10%, while an average of about 16% relative difference occurred for the back and side of the phantom. The differences were attributed to the different characteristics of the physical and simulated phantoms, such as anatomical structure and constituent materials. Nevertheless, there was about 4% of under-estimation compared to measurements in the overall linear fitting, indicating the calculations were well matched to the measurements.

Does Single Computed Tomography Attenuation Correction able to Surrogate Serial Computed Tomography Attenuation Correction in Single-Photon Emission Computed Therapy Imaging for Peptide Receptor Radionuclide Therapy Dosimetry Result?

Peptide Receptor Radionuclide Therapy (PRRT) is the administration of a radionuclide, such as the Lu-177 label, along with a pharmaceutical agent to destroy the lesion cell. The first cycle of Lu-177 DOTA-TATE is an excellent way to estimate radionuclide uptake for organs at risk. To estimate the absorbed dose for a kidney, serial SPECT-CT imaging with up to five sets is required. In general, serial CT on patients would result in additional external exposure and extra time consuming, especially for low dose CT such as cone beam CT technology. However, by introducing a new method, such as optimized single CT (24 h) to perform with serial SPECT attenuation correction, additional external exposure from serial CT exposure could be reduced.Aims:The purpose of this study is to assess the agreement between single CT scanning as CT attenuation Correction with serial CT scanning for serial SPECT imaging as well as estimated absorbed dose to the organ at risk.Settings and Design:During the first cycle of Lu177-DOTA-TATE, all patients should undergo internal dosimetry technique using SPECT-CT imaging with a PHILIP Brightview XCT gamma camera. The quantifications of SPECT images are being used to measure the uptake activity to the organ. In this investigation, Partik's categorical grading criteria are being used to convert the numeric value of Lin's concordance coefficient into an ordinal scale.Method:Total of 9 patients at our institution was administered with Lu177-DOTA-TATE enroll in this study. SPECT-CT data were acquired using automatic body contouring with a total of 48 angular views at steps of 6° (15 s/projections). The pixel size is 4.66 x 4.66 x 4.66 mm, the images size set to one, and SPECT data has been acquired for three-bed positions extending from the abdomen to the thorax region. Low-dose CT imaging performed at an X-ray tube voltage of 120 kVp.Results:Our current result demonstrated by single CT scanning for SPECT attenuation shown the excellent agreement with standard serial CT imaging for organs at risk such as kidney 0.999, spleen 0.9951, liver 0.9951 and bladder 0.9972.Conclusions:When compared to the previous method, patients benefit significantly more from this study, such as lower CT exposure.

A Comparison between Portal Dosimetry and Mobius3D Results for Patient-Specific Quality Assurance in Radiotherapy

A Comparison between Portal Dosimetry and Mobius3D Results for Patient-Specific Quality Assurance in Radiotherapy

Analysis of the planned, delivered dose distributions and quality assurance for helical tomotherapy and volumetric modulated arc therapy in locally advanced non-small cell lung cancer.

BackgroundWith full access to both helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT), we compared locally advanced non-small cell lung cancer (LA-NSCLC) treatment plans and verified the plans using patient-specific pretreatment quality assurance (PSQA).Materials and methodsFor each of the seventeen patients included in the study, two treatment plans (i.e. HT and VMAT) were created. Optimized plans were evaluated following the ICRU 83 criteria. Planned quality indexes and dosimetric parameters were compared. Lastly, all plans were subjected to PSQA assessment by determining the gamma passing rate (GPR).ResultsAll dosimetry results obtained from the planning target volume passed the ICRU 83 criteria. With regard to similar homogeneity indices, VMAT produced better conformity number values than HT (0.78 vs. 0.64), but differences in the values were insignificant. Furthermore, VMAT was associated with a significantly shorter mean treatment time (1.91 minutes vs. 6.66 minutes). For PSQA assessment, both techniques resulted in adequate GPR values (> 90% at the 3%/3 mm criteria).ConclusionBoth HT and VMAT techniques led to the generation of clinically satisfactory and reliable radiotherapy plans. However, the VMAT plan was associated with a non-significantly better degree of conformity and a significantly shorter treatment time. Thus, VMAT was determined to be a better choice for LA-NSCLC.

A customizable anthropomorphic phantom for dosimetric verification of 3D-printed lung, tissue, and bone density materials.

To design and manufacture a customized thoracic phantom slab utilizing the 3D printing process, also known as additive manufacturing, consisting of different tissue density materials. Here, we demonstrate the 3D-printed phantom's clinical feasibility for imaging and dosimetric verification of volumetric modulated arc radiotherapy (VMAT) plans for lung and spine stereotactic ablative body radiotherapy (SABR) through end-to-end dosimetric verification. A customizable anthropomorphic phantom slab was designed using the CT dataset of a commercial phantom (adult female ATOM dosimetry phantom, CIRS Inc.). Material extrusion 3D printing was utilized to manufacture the phantom slab consisting of acrylonitrile butadiene styrene material for the lung and the associated lesion, polylactic acid (PLA) material for soft tissue and spinal cord, and both PLA and iron-reinforced PLA materials for bone. CT images were acquired for both the commercial phantom and 3D-printed phantom for HU comparison. VMAT plans were generated for spine and lung SABR scenarios and were delivered as per departmental SABR protocols using a Varian TrueBeam STx linear accelerator. End-to-end dosimetry was implemented with radiochromic films, analyzed with gamma criteria of 5% dose difference, and a distance-to-agreement of 1mm, at a 10% low-dose threshold by comparing with calculated dose using the Acuros algorithm of the Eclipse treatment planning system (v15.6). 3D-printed phantom inserts were observed to produce HU ranging from -750 to 2100. The 3D-printed phantom slab was observed to achieve a similar range of HU from the commercial phantom including a mean HU of -760 for lung tissue, a mean HU of 50 for soft tissue, and a mean HU of 220 and 630 for low- and high-density bone, respectively. Film dosimetry results show 2D-gamma passing rates for lung SABR (internal and superior) and spine SABR (inferior and superior) over 98% and 90%, respectively. The end-to-end testing of VMAT plans for spine and lung SABR suggests the clinical feasibility of the 3D-printed phantom, consisting of different tissue density materials that emulate lung, soft tissue, and bone in kV imaging and megavoltage photon dosimetry. Further investigation of the proposed 3D printing techniques for manufacturability and reproducibility will enable the development of clinical 3D-printed phantoms in radiotherapy.

P143 - PRRT in patients with neuroendocrine tumor: preliminary results of OAR dosimetry and dose-response relationship for NET hepatic metastases

P143 - PRRT in patients with neuroendocrine tumor: preliminary results of OAR dosimetry and dose-response relationship for NET hepatic metastases

Volumetric Modulated Arc Therapy (VMAT) Craniospinal Irradiation (CSI) for Children and Adults: A Practical Guide for Implementation

PurposeVolumetric modulated arc therapy (VMAT) craniospinal irradiation (CSI) has been shown to have significant dosimetric advantages compared to 3-dimensional conformal therapy but is a technically complex process. We sought to develop a guide for all aspects of the VMAT CSI process and report patient dosimetry results. Methods and MaterialsWe initiated VMAT CSI in 2017 and have regularly revised our standard operating procedure for this process since then. Herein, we report a detailed template for the entire VMAT CSI process from initial patient setup and immobilization at time of computed tomography (CT) simulation to contouring and treatment planning, quality assurance, and therapy delivery. The records of 12 patients who were treated with VMAT CSI were also retrospectively reviewed. ResultsPatient age ranged from 2 to 59 years with 5 pediatric patients (age <18 years), 5 young adults (age 18-35 years), and 2 older adults (age >35 years). The majority of patients (67%) had medulloblastoma. CSI dose ranged from 21.6 to 36 Gy, with a median of 36 Gy. The median CSI planning target volume was 2383 cc with a median V95% of 99.8% and median 0.03 cc hotspot of 112.5%. The average V107% was 7.4% and the average conformality index was 1.01. ConclusionsVMAT CSI has potentially significant dosimetric and acute toxicity advantages compared to 3-dimensional conformal. However, proper procedures need to be in place throughout the process in order to be able to realize these potential advantages. We herein describe our detailed standard operating procedure for VMAT CSI. Recognizing the scarcity of proton beam centers in many areas, VMAT CSI represents a feasible treatment with more widespread availability.

Patient-specific dose assessment using CBCT images and Monte Carlo calculations

Today, the use of Cone-Beam Computed Tomography (CBCT) is increasing rapidly in medical diagnosis, therefore evaluation of patient's dose is a very important issue in radiation protection of patients. This study aimed to evaluate the patient-specific dose using CBCT images. Since CBCT images only showed a part of the head and while, the total anatomical specification of the head should be defined for dose assessment, therefore the whole parts of the head were generated using the data of the Extended Cardiac-Torso (XCAT) reference phantoms and pseudo-images were created. Tissue densities were calculated by the voxel values of pseudo-images and were used as the input file of Gate8.2 Monte Carlo (MC) code. Also, the GIANO CBCT unit was simulated and the absorbed dose was calculated by the code. For verification of this method, Rando phantom with embedded thermoluminescence dosimeters (TLD) with different protocols was used. The results of MC calculations and TLD measurements were compared and statistical analysis was performed using IBM SPSS Statistics. The calculated effective dose values determined by CBCT images for three different Temporomandibular joint, Single-Arch, and Both-Arch protocols were found to be 87 ± 3 μSv, 64 ± 1 μSv, and 66 ± 2 μSv, and the results of thermoluminescence dosimetry were 86 ± 2 μSv, 57 ± 1 μSv, and 63 ± 3 μSv, respectively. There were no significant differences (P-Value>0.05) between the results of MC calculations using CBCT images and the results of TLD dosimeters. In this study, a method for patient-specific dose assessment using CBCT images was introduced. It was shown that the dose of patients with its specification can be evaluated by CBCT images with acceptable accuracy.

Skin Dosimetry with EBT3 Radiochromic Film in Radiotherapy of Parotid Cancer.

Background: Skin is a sensitive organ and should be spared in radiotherapy and irradiation of skin in radiotherapy can cause to acute and late skin effects such as erythema, desquamation, epilation, color change, or even necrosis. Objective: The aim of the present study is to do skin dosimetry in radiotherapy of parotid cancer using Gafchromic EBT3 radiochromic film. EBT3 radiochromic films were calibrated in 0.2-5 Gy dose range.Material and Methods: This is an experimental study in the field of radiotherapy physics. Treatment planning was performed on a RANDO phantom for treatment of parotid cancer by a clinical oncologist. Based on the treatment planning, the skin dose at various points in the overlapping region of right anterior-oblique and right posterior-oblique fields were measured using EBT3 radiochromic film.Results: The minimum and maximum skin doses in a fraction (with 2.0 Gy prescribed dose) were 0.50 Gy and 0.97 Gy, respectively. Based on these values, the total skin dose in 30 treatment fractions (for removed tumor) or in 35 treatment fractions (for unremoved tumor) was in the range of 15-33 Gy. Conclusion: Based on the skin dosimetry results of parotid cancer radiotherapy using EBT3 films, it is predicted that there will occur mild skin reactions and these reactions can be neglected due to being mild.

Хромосомні аберації у лімфоцитах людини за зовнішнього та/або внутрішнього опромінення зразків крові 137Cs у модельних експериментах in vitro

The linear dependence of the yield of unstable chromosomal aberrations in human lymphocytes on the dose of prolonged external and/or internal irradiation of peripheral blood samples by 137Cs in the dose range of 0.09 - 0.54 Gy in vitro is presented. The higher cytogenetic efficiency of internal 137Cs irradiation is shown in comparison with external. It is shown that the cytogenetic efficiency of 137Cs in blood contamination is caused by influence on cells not only in the mitotic rest phase but during proliferation, within intracellular radioactivity through their cultivation. It is proposed to use the presented dose dependences of the yield of chromosomal aberrations in lymphocytes in vitro for human biological dosimetry during radiation accidents associated with prolonged external exposure or 137Cs incorporation to the body as a supplement to the results of physical dosimetry.

Clinical performance of FractionLab in patient-specific quality assurance for intensity-modulated radiotherapy: a retrospective study.

BackgroundThis study was aimed at comparing and analyzing the results of FractionLab (Varian/Mobius Medical System) with those of portal dosimetry that uses an electronic portal imaging device. Portal dosimetry is extensively used for patient-specific quality assurance (QA) in intensity-modulated radiotherapy (IMRT).MethodsThe study includes 29 patients who underwent IMRT on a Novalis-Tx linear accelerator (Varian Medical System and BrainLAB) between June 2019 and March 2021. We analyzed the multileaf collimator DynaLog files generated after portal dosimetry to evaluate the same condition using FractionLab. The results of the recently launched FractionLab at various gamma indices (0.1%/0.1 mm–1%/1 mm) are analyzed and compared with those of portal dosimetry (3%/3 mm).ResultsThe average gamma passing rates of portal dosimetry (3%/3 mm) and FractionLab are 98.1% (95.5%–100%) and 97.5% (92.3%–99.7%) at 0.6%/0.6 mm, respectively. The results of portal dosimetry (3%/3 mm) are statistically comparable with the QA results of FractionLab (0.6%/0.6 mm–0.9%/0.9 mm).ConclusionThis paper presents the clinical performance of FractionLab by the comparison of the QA results of FractionLab using portal dosimetry with various gamma indexes when performing patient-specific QA in IMRT treatment. Further, the appropriate gamma index when performing patient-specific QA with FractionLab is provided.

Evaluation of Correlation between DAP (Dose-Area Product) Values and Cardiologist Dose during Coronary Angiography Using Monte Carlo Simulation

Introduction: The present study investigated the correlations between the patient’s dose-area product (DAP) values and cardiologist’s dose using Monte Carlo simulation. During angiography procedures, patients are exposed to the primary beam; however, the cardiologist is irradiated by the scattered radiation arising from the table and the surrounding equipment. Accordingly, the cardiologist’s dose is directly related to the patient’s dose. Material and Methods: This study investigated 25 cardiac angiography procedures. In each procedure, the DAP readings and the cardiologist dose as measured using an electronic personal dosimeter placed over the apron were recorded. Moreover, the DAP values and dose received by the cardiologist in the chest region were calculated using the Monte Carlo N-Particle extended code. For the validation of the simulated spectrum, dosimetric measurements were made using a Farmer ionization chamber and a phantom. Results: The data obtained from 18 simulations showed that there was a strong linear relationship (R2=0.71) between the two variables of cardiologist’s dose and patient’s DAP. Likewise, the obtained results of dosimetry conducted on the patients in 25 cardiac angiography procedures revealed that there was a strong relationship (R2=0.78) between the two variables. Conclusion: The reported correlation rates show the appropriateness of the physician radiation exposure to total patient’s DAP. With respect to the strong correlation coefficient obtained from the simulation method, it is recommended that this method should be verified by dosimetry. The findings of this study showed a linear relationship between the cardiologist’s dose and the total dose of the patient.

A Collaborative Experience: Implementation of an Optimized Tc-99m Generator Assembly Process

Abstract Technetium-99m (Tc-99m) has a 6-hr half-life making customer transportation times a challenge. Australian Nuclear Science and Technology Organization (ANSTO) health products group has overcome this by delivering the parent isotope molybdenum-99 (Mo-99), which has a half-life of 66 hr, in shielded GENTECH™ generators. As part of ANSTO's questioning attitude, an augmented risk assessment was undertaken to identify any potential exposure risks of the GENTECH™ assembly process. The evaluation identified potential areas of improvement in contamination control for the manual handling of the generator leads. Upon further analysis, contamination events from the generator leads had the potential for skin doses above the threshold for skin tissue reactions. Additional substitution and administrative controls were designed to mitigate the risks identified. The effectiveness of the new controls was assessed for efficiency in the manufacturing process through mock trials and fitness for use in a pharmaceutical cleanroom environment. The implemented controls were monitored, and data from each run were gathered. These data included changes in radiological conditions and dosimetry results. Upon implementation, there was an observable decrease in glove contamination. The decrease verified that there was a reduction in the risk of skin contamination events. The data analysis was used to model the dose averted, which revealed a reduction in potential extremity dose to production workers. This paper aims to show the optimization within an approved process through the implementation of engineering and administrative controls, resulting in a dose reduction to workers.

Impact of photoelectric cross section data on systematic uncertainties for Monte Carlo breast dosimetry in mammography

Monte Carlo (MC) simulations are employed extensively in breast dosimetry studies. In the energy interval of interest in mammography energy deposition is predominantly caused by the photoelectric effect, and the corresponding cross sections used by the MC codes to model this interaction process have a direct influence on the simulation results. The present work compares two photoelectric cross section databases in order to estimate the systematic uncertainty, related to breast dosimetry, introduced by the choice of cross sections for photoabsorption. The databases with and without the so-called normalization screening correction are denoted as ‘renormalized’ or ‘un-normalized’, respectively. The simulations were performed with the PENELOPE/penEasy code system, for a geometry resembling a mammography examination. The mean glandular dose (MGD), incident air kerma (K air), normalized glandular dose (DgN) and glandular depth-dose (GDD(z)) were scored, for homogeneous breast phantoms, using both databases. The AAPM Report TG-195 case 3 was replicated, and the results were included. Moreover, cases with heterogeneous and anthropomorphic breast phantoms were also addressed. The results simulated with the un-normalized cross sections are in better overall agreement with the TG-195 data than those from the renormalized cross sections; for MGD the largest discrepancies are 0.13(6)% and 0.74(5)%, respectively. The MGD, K air and DgN values simulated with the two databases show differences that diminish from approximately 10%/3%/6.8% at 8.25 keV down to 1.5%/1.7%/0.4% at 48.75 keV, respectively. For polyenergetic spectra, deviations up to 2.5% were observed. The disagreement between the GDDs simulated with the analyzed databases increases with depth, ranging from −1% near the breast entrance to 4% near the bottom. Thus, the choice of photoelectric cross section database affects the MC simulation results of breast dosimetry and adds a non-negligible systematic uncertainty to the dosimetric quantities used in mammography.

Comparison of different methods for post-therapeutic dosimetry in [177Lu]Lu-PSMA-617 radioligand therapy

BackgroundDosimetry is of high importance for optimization of patient-individual PSMA-targeted radioligand therapy (PSMA-RLT). The aim of our study was to evaluate and compare the feasibility of different approaches of image-based absorbed dose estimation in terms of accuracy and effort in clinical routine.MethodsWhole-body planar images and SPECT/CT images were acquired from 24 patients and 65 cycles at 24h, 48h, and ≥96h after administration of a mean activity of 6.4 GBq [177Lu]Lu-PSMA-617 (range 3–10.9 GBq). Dosimetry was performed by use of the following approaches: 2D planar-based dosimetry, 3D SPECT/CT-based dosimetry, and hybrid dosimetry combining 2D and 3D data. Absorbed doses were calculated according to IDAC 2.1 for the kidneys, the liver, the salivary glands, and bone metastases.ResultsMean absorbed doses estimated by 3D dosimetry (the reference method) were 0.54 ± 0.28 Gy/GBq for the kidneys, 0.10 ± 0.05 Gy/GBq for the liver, 0.81 ± 0.34 Gy/GBq for the parotid gland, 0.72 ± 0.39 Gy/GBq for the submandibular gland, and 1.68 ± 1.32 Gy/GBq for bone metastases. Absorbed doses of normal organs estimated by hybrid dosimetry showed small, non-significant differences (median up to 4.0%) to the results of 3D dosimetry. Using 2D dosimetry, in contrast, significant differences (median up to 10.9%) were observed. Regarding bone metastases, small, but significant differences (median up to 7.0%) of absorbed dose were found for both, 2D dosimetry and hybrid dosimetry. Bland-Altman analysis revealed high agreement between hybrid dosimetry and 3D dosimetry for normal organs and bone metastases, but substantial differences between 2D dosimetry and 3D dosimetry.ConclusionHybrid dosimetry provides high accuracy in estimation of absorbed dose in comparison to 3D dosimetry for all important organs and is therefore feasible for use in individualized PSMA-RLT.

Determination of optimal ventilation rates in educational environment in terms of radon dosimetry.

New and renovated energy efficient buildings with minimised ventilation rates together with increased building airtightness are often associated with higher indoor radon concentrations compared to the concentrations in existing buildings. The purpose of our study is to analyse the problem associated with the increased radon concentration and ventilation requirements and recommendations in schools. The radon concentration was critically assessed by varying the design ventilation rates (DVRs) within fifteen cases according to legislative requirements and recommendations. The case study is a branch primary school in western part of Slovenia situated in a radon prone area. Radon (222Rn) concentrations were simulated in the classroom, using CONTAM 3.2. For validation, measurements were performed on 8 measuring days in September and 6 measuring days in March. The simulated and measured 222Rn concentrations are well correlated for all measurement days, with the simulated/measured ratio of 0.85-1.39. In order to define optimal DVRs in terms of dosimetry, the effective dose and its ratio to the worldwide average effective dose at workplace, received by radon progeny in 950h (expected effective dose, 0.13mSv/y), were calculated for each case. Simulations showed that the highest radon concentrations were observed in case 1 with a DVR of 79.6m3/h (621 Bq/m3) and case 4 with a DVR of 69.4m3/h (711 Bq/m3), both defined by national regulations. The calculated values in both cases exceeded the national reference value for radon (300 Bq/m3) by 2.1 times and 2.4 times, and the WHO guideline value (100 Bq/m3) by 6.2 times and 7.1 times, respectively. The simulations are in line with the results of radon dosimetry. Both DVRs correspond to the highest effective doses, 1.88 mSv/y (about 14-fold higher than expected effective dose) for case 1 and 2.15 mSv/y (about 17-fold higher than expected effective dose) for case 4. Case 11_Cat I with a DVR of 1999.7m3/h defined by EN 15251: 2007 resulted in minimal Rn concentration (35 Bq/m3) and corresponds to the lowest effective dose 0.11 mSv/y and its ratio to the expected effective dose 0.8. Ventilation is an immediate measure to reduce radon concentration in a classroom and it must be performed in line with other holistic measures to prevent and control radon as a health risk factor.

Effects of Real-Time Dosimetry on Staff Radiation Exposure in the Cardiac Catheterization Laboratory.

Radiation protection is essential for staff of cardiac catheterization laboratories in order to prevent long-term radiation- associated injury and disease. Instant feedback about the actual received dose may help operators to optimize the use of existing shielding devices. Therefore, the current study was designed to investigate whether routine use of real-time dosimetry may be able to reduce staff radiation exposure. Over a period of 72 days, operators and assisting nurses were equipped with RaySafe i3 real-time dosimeters (Unfors RaySafe AB), but had no access to the dosimetry results during the first half of the study. This was followed by a second period that allowed operators to modify their behavior according to the dosimetry results. Compared with the first phase, the knowledge of real-time dosimetry results led to a uniform reduction in radiation exposure of all team members by approximately 60%, independent of the chosen vascular access. There were no significant changes in fluoroscopy time, dose-area product, or patient characteristics. Real-time dosimetry effectively reduced staff radiation exposure in the cardiac catheterization laboratory. This change was caused by optimized use of existing shielding equipment since no modifications of the general procedural approach or patient characteristics had occurred.

Predictability of Elimination and Excretion of Small Molecules in Animals and Humans, and its Impact on Dosimetry for human ADME Studies with Radiolabeled Drugs.

We assessed the extent to which urinary and fecal excretion of 14C-labeled drug material in animal ADME studies was predictive of human ADME studies. We compared observed plasma elimination half-lives for total drug-related radioactivity in humans to pre-study predictions, and we estimated the impact of any major differences on human dosimetry calculations. We included 34 human ADME studies with doses of 14C above 0.1 MBq. We calculated ratios of dosimetry input parameters (percentage fecal excretion in humans versus animals; observed half-life in humans versus predicted pre-study) and output parameters (effective dose post-study versus pre-study) and assessed their relationship. A quantitative correlation assessment did not show a statistically significant correlation between the ratios of percentages of 14C excreted in feces and the ratios of dosimetry outcomes in the entire dataset, but a statistically significant correlation was found when assessing the studies that were based on ICRP 60/62 (n=19 studies; P=0.0028). There also appeared to be a correlation between the plasma half-life ratios and the ratios of dosimetry results. A quantitative correlation assessment showed that there was a statistically significant correlation between these ratios (P<0.0001). In all cases where the plasma elimination half-life for 14C in humans was found to be longer than the predicted value, the radiation burden was still within ICRP Category IIa. Containment of the actual radiation burden below the limit of 1.00 mSv appeared to be determined partly also by our choice to limit 14C doses to 3.7 MBq.

Analysis of gamma index using in-house developed heterogeneous thorax phantom

Quality assurance (QA) before patient treatment plays a major role in complex radiotherapy (RT) treatment planning. Phantoms are the standard materials that are used for the pre-treatment QA of patients. Contemporary phantoms used in RT are mainly water-based, having simple geometry and of uniform density. These phantoms dose not replicate the exact heterogeneities of the actual human body. The present work aims to evaluate the results of relative dosimetry performed on in-house developed heterogeneous thorax phantom (HTP) using an electronic portal imaging device (EPID). To perform the relative dosimetry, contours were drawn on HTP at three different locations and intensity modulated radiotherapy (IMRT), as well as Rapid ARC (RA), were generated on it to compare the fluence obtained on TPS as well as on linac machine. The gamma evaluation results indicate a strong correlation between planned and the measured fluence. We found the EPID-based QA done on HTP explore its property as a QA tool and it can further be used to perform patient-specific relative dosimetry.