Optimal Radiation Dose Research Articles

Karakterisasi Bolus Berbahan Campuran Beeswax dan Petroleum Jelly Menggunakan Berkas Elektron Pada Energi 6 MeV dan 9 MeV

In radiotherapy cases of cancer on the surface of the skin generally use electron beams. The electron beam has not been able to provide the optimum surface radiation dose. Therefore, a material that is able to increase the dose of surface radiation is needed, which is called a bolus. This study tested a bolus made from a mixture of beeswax and petroleum jelly. The bolus test includes the determination of density, the value of Relative Electron Density (RED) and the determination of the absorbed dose. The absorbed dose value was obtained by irradiating using a Linear Accelerator (LINAC) at 6 MeV and 9 MeV energies. The RED value was obtained from the bolus tomography image using a CT-simulator by determining the Region of Interest (ROI). The bolus density values obtained from physical measurements using the TPS program have almost the same average density values. The RED bolus value obtained at a thickness of 0.2 cm to 0.8 cm has a lower RED value than the RED value of the breast, which is 0.976. However, at 1.0 cm thickness, the RED value is equivalent to breast tissue. The value of the absorbed dose in a bolus made from a mixture of beeswax and petroleum jelly, the thicker the bolus used, the smaller the increase in the absorbed dose. The results of this study indicate that a bolus made from a mixture of beeswax and petroleum jelly can be the choice of bolus material during radiotherapy.

Current and future on definitive concurrent chemoradiotherapy for inoperable locally advanced esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is an aggressive and fatal disease that is usually diagnosed when the chances for surgical intervention has been missed. Definitive concurrent chemoradiotherapy (dCRT) is the first choice of treatment for inoperable locally advanced esophageal squamous cell carcinoma (LA-ESCC). Nevertheless, the local recurrence rate for esophageal cancer patients undergoing dCRT remains high at 40-60%, with a 5-year overall survival rate of solely 10-30%. Immunotherapy in combination with dCRT is a promising treatment for inoperable LA-ESCC, for that improved long-term survival is expected. The present review provides a comprehensive overview of the evolutionary trajectory of dCRT for LA-ESCC, delineates notable relevant clinical studies, addresses unresolved concerns regarding the combination of dCRT with immunotherapy, and highlights promising directions for future research. When dCRT is combined with immunotherapy, the following aspects should be carefully explored in the future studies, including the optimal irradiation dose, segmentation scheme, radiotherapy technique, timing, sequence and duration of radiotherapy, and the selection of chemotherapeutic and immunologic drugs. In addition, further investigations on the mechanisms of how dCRT combined with immunotherapy exerts synergistic anti-tumor effects and molecular biomarkers ensuring precise screening of ESCC patients are needed.

Low-Dose Radiation Yields Lower Rates of Pathologic Response in Esophageal Cancer Patients

BackgroundAlthough neoadjuvant chemoradiation (nCRT) followed by surgery is standard treatment for locally advanced esophageal or gastroesophageal junction (E/GEJ) cancer, the optimal radiation dose is still under debate.ObjectiveThe aim of this study was to assess the impact of different preoperative radiation doses (41.4 Gy, 45 Gy or 50.4 Gy) on pathologic response and survival in E/GEJ cancer patients.MethodsAll consecutive patients with E/GEJ tumors, treated with curative intent between January 2009 and December 2016 in two referral centers were divided into three groups (41.4 Gy, 45 Gy and 50.4 Gy) according to the dose of preoperative radiotherapy. Pathologic complete response (pCR) rates, postoperative morbidity, overall survival (OS) and disease-free survival (DFS) were compared among the three groups, with separate analyses for adenocarcinoma (AC) and squamous cell carcinoma (SCC).ResultsFrom the 326 patients analyzed, 48 were included in the 41.4 Gy group (14.7%), 171 in the 45 Gy group (52.5%) and 107 in the 50.4 Gy group (32.8%). Postoperative complication rates were comparable (p = 0.399). A pCR was observed in 15%, 30%, and 34% of patients in the 41.4 Gy, 45 Gy and 50.4 Gy groups, respectively (p = 0.047). A 50.4 Gy dose was independently associated with pCR (odds ratio 2.78, 95% confidence interval 1.10–7.99) in multivariate analysis. Within AC patients, pCR was observed in 6.2% of patients in the 41.4 Gy group, 29.2% of patients in the 45 Gy group, and 22.7% of patients in the 50.4 Gy group (p = 0.035). No OS or DFS differences were observed.ConclusionsA pCR was less common after a preoperative radiation dose of 41.4 Gy in AC patients. Radiation dose had no impact on postoperative morbidity, long-term survival, and recurrence.

Low-dose radiotherapy promotes the formation of tertiary lymphoid structures in lung adenocarcinoma.

A tertiary lymphoid structure (TLS) refers to an organized infiltration of immune cells that is linked to a positive prognosis and improved response to immunotherapy. However, methods that promote TLS formation are limited and challenging to implement in clinical settings. In this study, we aimed to promote the formation and maturation of TLSs in lung adenocarcinoma (LUAD) by combining low-dose radiotherapy (LDRT) with immunotherapy. Tissue sections from 198 patients who had undergone surgery were examined. Risk factors for patient survival were assessed, and the relationship between TLSs and five-year survival was analyzed. The Kras-LSL-G12D spontaneous lung cancer mouse model was used to screen the optimal irradiation dose (0/1/2 Gy whole lung irradiation) for promoting TLS formation. LDRT combined with anti-PD-1 was used to promote the formation and maturation of TLSs. TLS+, TLSHigh, TLS+GC+ and CD8High within TLS+ were associated with a favorable prognosis. LDRT increased the formation of early TLSs in the Kras-LSL-G12D lung cancer mouse model. In addition, LDRT combined with anti-PD-1 treatment can significantly improve the maturity of TLSs in mouse LUAD, resulting in greater antitumor effects. This antitumor effect was strongly associated with the number of CD8+ T cells within the TLSs. We successfully applied LDRT combined with PD-1 inhibitor therapy for the first time, which increased both the quantity and maturity of TLSs in lung cancer. This approach achieved a promising antitumor effect.

The scheme, and regulative mechanism of pyroptosis, ferroptosis, and necroptosis in radiation injury.

Radiotherapy (RT) stands as the primary treatment for tumors, but it inevitably causes damage to normal cells. Consequently, radiation injury is a crucial consideration for radiation oncologists during therapy planning. Cell death including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis play significant roles in tumor treatment. While previous studies elucidated the induction of apoptosis and autophagy by ionizing radiation (IR), recent attention has shifted to pyroptosis, ferroptosis, and necroptosis, revealing their effects induced by IR. This review aims to summarize the strategies employed by IR, either alone or in combination therapy, to induce pyroptosis, ferroptosis, and necroptosis in radiation injury. Furthermore, we explore their effects and molecular pathways, shedding light on their roles in radiation injury. Finally, we summarize the regulative agents for these three types of cell death and their mechanisms. In summary, optimizing radiation dose, dose rate, and combined treatment plans to minimize radiation damage and enhance the killing effect of RT is a key focus.

Evaluation of radiation dose and establishment of local DRLs for adult during abdominopelvic CT scan imaging for university hospital centers, Morocco

Objective: In this study, we have planned to establish the local Diagnostic Reference Levels (DRLs) for the five University Hospital Centers in Morocco and to propose a national DRL for abdominopelvic CT examinations for adult patients. Materials and methods: Data were collected using a specially designed form, which included patient demographics, exposure parameters and dosimetric indicators such as dose-length product (DLP) and CT volume dose index (CTDIvol). The establishment of local and national DRL in terms of CTDIvol and DLP was carried out in accordance with the methodology described in Report 135 of the International Commission on Radiological Protection (ICRP). The effective dose was assessed using the DLP and the dose conversion factor appropriate for this location. Results: A total of 300 patients undergoing abdominopelvic examinations at the five Moroccan university hospitals were collected for this study. Patients' mean age, weight and BMI were (50.97 ± 15.05) years (67.94 ± 11.41) Kg and (25.71 ± 3.03) Kg/m2 respectively. The local DRL, in terms of DLP were 551.56, 2293.33, 709.02, 843.52 and 1059.62 mGy-cm and in terms of CTDIvol were 11,05, 46,40, 13,14, 12,01, 9,88 mGy respectively for UHC-1, UHC-2, UHC-3, UHC-4 and UHC-5 hospitals. The proposed National DRL, defined as a single value for the 75th percentile on the aggregation of data from the five centers, for abdominopelvic scan CT was 773.20 mGy.cm and 12.05 mGy for DLP and CTDIvol, respectively. Conclusion: The Moroccan DRL was comparable to those of other countries, ranking 10th among 21 countries. However, we are still seeking to reduce and optimize radiation dose while maintaining good image quality for reliable diagnosis, and this can be achieved by enhancing radiographers' and radiologists' knowledge of radiation protection, protocol justification, and optimization through rigorous hospital radiation audits at national level.

Влияние гамма-излучения на содержание свободного пролина и малонового диальдегида в проростках ячменя обыкновенного

It is well known that the formation of reactive oxygen species in the organism due to the impact of negative factors of various nature is one of the main mechanisms of stress state formation at the level of cells and tissues. In plants reactive oxygen species play a key role in the response to abiotic stress through signalling and activation of the defence system. The purpose of the work is to study the effect of gamma radiation on the content of malondialdehyde (MDA) and free proline in seedlings of common barley (Hordeum vulgare L.) of three varieties. The effect of radiation was assessed by changes in the concentrations of the substances under study, which was determined by the photometric method. It was shown that a statistically significant increase in the MDA content in germinated seeds of the Vityaz and Ladny varieties was observed when irradiated at doses of 2, 5, 10, 25 and 50 Gy, and in the Badjoriy variety when irradiated at doses of 2, 20, 25 and 50 Gy. An increase in the concentration of free proline was observed at all studied doses of gamma irradiation, with the exception of irradiation at a dose of 15 Gy for the Vityaz and Ladny varieties. A relationship was noted between the content of free proline and MDA in plant material (correlation coefficient for the Vityaz variety – 0.871+/-0.121; for the Ladny variety – 0.892+/-0.103; for the Badjoriy variety – 0.886+/-0.112). Regardless of the variety, the observed changes in the studied parameters demonstrate similar dynamics, which is of practical value for assessing the degree of technogenic pollution of agricultural biogeocenoses. The obtained quantitative data will make it possible to determine the optimal radiation doses for each zoned variety, which will help optimize the use of radiation technologies in agriculture.

Theranostic digital twins: Concept, framework and roadmap towards personalized radiopharmaceutical therapies.

Radiopharmaceutical therapy (RPT) is a rapidly developing field of nuclear medicine, with several RPTs already well established in the treatment of several different types of cancers. However, the current approaches to RPTs often follow a somewhat inflexible "one size fits all" paradigm, where patients are administered the same amount of radioactivity per cycle regardless of their individual characteristics and features. This approach fails to consider inter-patient variations in radiopharmacokinetics, radiation biology, and immunological factors, which can significantly impact treatment outcomes. To address this limitation, we propose the development of theranostic digital twins (TDTs) to personalize RPTs based on actual patient data. Our proposed roadmap outlines the steps needed to create and refine TDTs that can optimize radiation dose to tumors while minimizing toxicity to organs at risk. The TDT models incorporate physiologically-based radiopharmacokinetic (PBRPK) models, which are additionally linked to a radiobiological optimizer and an immunological modulator, taking into account factors that influence RPT response. By using TDT models, we envisage the ability to perform virtual clinical trials, selecting therapies towards improved treatment outcomes while minimizing risks associated with secondary effects. This framework could empower practitioners to ultimately develop tailored RPT solutions for subgroups and individual patients, thus improving the precision, accuracy, and efficacy of treatments while minimizing risks to patients. By incorporating TDT models into RPTs, we can pave the way for a new era of precision medicine in cancer treatment.

National diagnostic reference levels for digital diagnostic and screening mammography in Uganda.

Screening and diagnostic mammography are associated with some risk of radiation-induced breast cancer. This study was conducted to establish the National Diagnostic Reference Levels (NDRLs) for digital diagnostic and screening mammography in Uganda to achieve breast radiation dose optimization. A cross-sectional study was conducted among female participants recruited by consecutive sampling from three selected hospitals with digital mammography in Uganda. The study variables extracted from the mammography machines were exposure factors, compressed breast thickness (CBT), and Average Glandular Dose (AGD) of two standard mammogram views. The stratified National DRL was derived by calculating the 75th percentile of the AGD across all the samples at various CBT ranges for both screening and diagnostic mammography in craniocaudal (CC) and mediolateral oblique (MLO) views. We included 300 participants with mean ages of 50.28±9.32 and 47.45±13.45 years for the screening and diagnostic mammography, respectively. There were statistically significant positive correlations between AGD and exposure factors (mAs, kVp) (all p-values<0.0001). For screening mammography, mAs demonstrated a strong positive correlation (r = 0.8369 in CC, 0.8133 in MLO), whereas kVp showed a positive correlation with relatively lower coefficients (r = 0.3700 in CC, 0.3080 in MLO). For diagnostic mammography, mAs exhibited an even stronger positive correlation (r = 0.8987 in CC, 0.8762 in MLO), and kVp maintained a positive correlation with somewhat lower coefficients (r = 0.4954 in CC, 0.3597 in MLO). In screening mammography, for CBT within the range of (7-39) mm, the NDRLs were (1.5mGy, 1.66mGy) in CC) and MLO views. For CBT in the range of (40-59) mm, the NDRLs were (1.78mGy, 1.87mGy), and for CBT in the range of (60-99) mm, the NDRLs were (2.18mGy, 2.22mGy). For diagnostic mammography, the NDRLs were established as (1.7mGy, 1.91mGy), (2.00mGy, 2.09mGy), and (2.63mGy, 2.81mGy) for CBT ranges of (7-39) mm, (40-59) mm, and (60-99) mm, respectively. The NDRLs for digital screening and diagnostic mammography in Uganda have been proposed for the first time. The NDRL values in mammography should be specific to CBT ranges and mammographic views for both diagnostic and screening mammography.

Radiotherapy and blockade of immune checkpoints in treatment of cancer patients

Background. Immunotherapy, which aims to use immune defense mechanisms to fight cancer, is a new area of anticancer treatment. A major breakthrough in tumor immunotherapy was the discovery of immune checkpoint proteins, which act as powerful suppressors of the immune system. Humanized monoclonal antibodies, which target these proteins, have proven to be clinically effective in patients with different types of cancer. However, the majority of patients do not respond to checkpoint inhibitor therapy, which necessitates the use of combination strategies to overcome resistance to immunotherapy. In recent years, the combination of radiotherapy and immune checkpoint inhibitors has attracted considerable attention and has been widely studied in preclinical and clinical trials. Much attention is given to the optimization of combined treatment regimens. However, the optimal radiation dose, fractionation scheme, radiation volumes, and radiation sequence in checkpoint inhibitor treatment still remain unclear. Purpose – to analyze and summarize data from preclinical and clinical trials aimed at solving problems related to the choice of optimal doses, fractionation, radiation volume, and sequencing of checkpoint inhibitor immunotherapy and radiotherapy. Materials and methods. For data search, we used Cochrane library and databases (Pubmed, Scopus, Google Scholar). The results of the studies published over the period from 2008 to 2023 were analyzed. Results and discussion. The evidence of the rationality of combining radiotherapy and checkpoint inhibitors in the treatment of cancer patients is shown. The data on the effects of radiation dose and fractionation on antitumor immune responses were analyzed. The results of works that deal with the search for the optimal sequence of radiotherapy and immune checkpoint inhibitors and the selection of the irradiation volume necessary for the generation of an effective systemic antitumor immune response are considered. Conclusions. Combined treatment with radiation therapy and immune checkpoint inhibitors is a promising strategy for patients with metastatic tumors. Preclinical and clinical data indicate that different radiation regimens can cause different effects on antitumor immunity. Further studies of doses and fractionation regimens of radiation therapy, irradiation volume, and the optimal time for each component of combination therapy are needed to determine the conditions for maximizing the immune response. The obtained results will help optimize the combination treatment regimens and wider implementation of such treatment in clinical practice.

Coronary stenosis quantification in cardiac computed tomography angiography: multi-factorial optimization of image quality and radiation dose.

The accuracy and variability of quantification in computed tomography angiography (CTA) are affected by the interplay of imaging parameters and patient attributes. The assessment of these combined effects has been an open engineering challenge. In this study, we developed a framework that optimizes imaging parameters for accurate and consistent coronary stenosis quantification in cardiac CTA while accounting for patient-specific variables. The framework utilizes a task-specific image quality index, the estimability index (), approximated by a surrogate estimability polynomial function (EPF) capable of finding the optimal protocol that (1)maximizes image quality with an upper bound for desired radiation dose or (2)minimizes the dose level with a lower bound of acceptable image quality. The optimization process was formulated with the decision variables being subject to a set of constraints. The methodology was verified using CTA data from a prior clinical trial (prospective multi-center imaging study for evaluation of chest pain) by assessing the concordance of its prediction with the trial results. Further, the framework was used to derive an optimum protocol for each case based on the patient attributes, gauging how much improvement would have been possible if the derived optimized protocol would have been deployed. The framework produced results consistent with imaging physics principles with approximated EPFs of 97% accuracy. The feature importance evaluation demonstrated a close match with earlier studies. The verification study found scores closely predicting the cardiologist scores to within 95% in terms of the area under the receiver operating characteristic curve and predicting potential for either an average of fourfold increase in within a targeted dose or a reduction in radiation dose by an average of 57% without reducing the image quality. The protocol optimization framework provides means to assess and optimize CTA in terms of either image quality or radiation dose objectives with its results predicting prior clinical trial findings.

Quantitative functional imaging with CT perfusion: technical considerations, kinetic modeling, and applications

CT perfusion (CTP)-derived quantitative maps of hemodynamic parameters have found important clinical applications in stroke, cancer, and cardiovascular disease. Blood flow, blood volume, transit time, and other perfusion parameters are sensitive markers of pathophysiology with impaired perfusion. This review summarizes the basic principles of CTP including image acquisition, tracer kinetic modeling, deconvolution algorithms, and diagnostic interpretation. The focus is on practical and theoretical considerations for accurate quantitative parametric imaging. Recommended CTP scan parameters to maintain CT number accuracy and optimize radiation dose versus image noise are first reviewed. Tracer kinetic models, which describe how injected contrast material is distributed between blood and the tissue microenvironment by perfusion and bidirectional passive exchange, are then derived. Deconvolution algorithms to solve for hemodynamic parameters of kinetic models are discussed and their quantitative accuracy benchmarked. The applications and diagnostic interpretation of CTP in stroke, cancer, and cardiovascular disease are summarized. Finally, we conclude with a discussion of future directions for CTP research, including radiation dose reduction, new opportunities with novel CT hardware, and emerging diagnostic applications.

Anthropomorphic breast phantoms for radiology imaging: a review

Phantoms are used to validate diagnostic imaging methods or improve the skills of medical professionals. For instance, they allow conducting an unlimited number of imaging studies during medical training, assessing image quality, optimizing radiation dose, and testing novel techniques and equipment. Researchers in breast imaging use anthropomorphic models to validate, assess, and optimize new methods for diagnosing breast diseases. Such models also facilitate control over the quality of diagnostic systems, help optimize clinical protocols, and improve image reconstruction algorithms. Realistic simulation of the breast tissue is essential to address the challenges of advancing X-ray mammary gland studies. The review aimed to describe phantoms currently available for diagnostic imaging and the way they were fabricated. In this literature review, PubMed, eLIBRARY, and Google Scholar databases were screened for relevant articles. Thus, 72 articles and 13 conference papers were included. The study two major types of breast phantoms: computational and physical. Specifically, computational phantoms are classified into subgroups depending on the data they use. These include mathematical models, tissue samples, and medical images of the breast. The classification of the physical phantoms is based on their manufacturing process: casting silicone-like substances, 3D printing with resins and plastics, or printing on paper using X-ray contrast ink. Computational phantoms are generally advantageous with respect to versatility, efficiency, precision, and safety and allow the generation of large amounts of virtual data. Physical phantoms provide the most realistic diagnostic images without the need for a patient and allow performing an unlimited number of radiological studies.

Effects of irradiation on the quality of fresh waxy corn

The present study aimed to investigate the effects of different irradiation doses on the physicochemical properties, sensory indexes, the total bacterial count in fresh waxy corn, and the optimum irradiation dose range for fresh waxy corn. The whole ear of fresh waxy corn was irradiated with the irradiation doses of 0, 2, 4, 6, 8, and 10 kGy, and the changes in the contents of moisture, reducing sugar, total sugar, starch, total dietary fiber, ash, crude fat, and protein, as well as the changes in color, odor, taste, and the total bacterial count of fresh waxy corn before and after irradiation were compared. The results showed that the contents of moisture and total dietary fiber in the irradiated fresh waxy corn showed no significant changes (P ≥ 0.05). On the contrary, the contents of reducing sugar and protein in the fresh waxy corn with irradiation treatment increased at certain doses, with a maximum increase of 95.95% and 13.60%, respectively. Similarly, the contents of total sugar, starch, and ash decreased significantly (P < 0.05) by 29.22%, 20.23%, and 20.60%, respectively. The irradiation treatment could maintain the brightness of fresh waxy corn and improve its sensory attributes by interfering with the contents of flavor substances, such as alkanes, alcohols, and some aromatic compounds in fresh waxy corn. The total bacterial count of irradiated fresh waxy corn decreased significantly (P < 0.05) to one order of magnitude. Overall, the experimental results suggest that irradiation is helpful for improving the quality and extending the shelf life of fresh waxy corn.

Technical specifications of dose management systems: An international atomic energy agency survey.

Dose management systems (DMS) have been introduced in radiological services to facilitate patient radiation dose management and optimization in medical imaging. The purpose of this study was to gather as much information as possible on the technical characteristics of DMS currently available, regarding features that may be considered essential for simply ensuring regulatory compliance or desirable to fully utilize the potential role of DMS in optimization of many aspects of radiological examinations. A technical survey was carried out and all DMS developers currently available (both commercial and open source) were contacted and were asked to participate. An extensive questionnaire was prepared and uploaded in the IAEA International Research Integration System (IRIS) online platform which was used for data collection process. Most of the questions (93%) required a "Yes/No" answer, to facilitate an objective analysis of the survey results. Some free text questions and comments' slots were also included, to allow participants to give additional information and clarifications where necessary. Depending on the answer, they were considered either as "Yes" or "No." Given the way that the questions were posed, every positive response indicated that a feature was offered. Thus, the percentage of positive responses was used as a measure of adherence. The percentages of positive answers per section (and sub-section) are presented in graphs and limitations of this type of analysis are discussed in detail. The results of this survey clearly exhibit that large differences exist between the various DMS developers. Consequently, potential end users of a DMS should carefully determine which of the features available are essential for their needs, prioritize desirable features, but also consider their infrastructure, the level of support required and the budget available before selecting a DMS.

Audit Dosis dan Optimisasi Pemeriksaan CT Scan Kepala: Studi Multisenter

One of the principles of radiation protection is optimizing radiation dose and image quality. Dose audits and optimization of head CT scans for the adult patient category have been carried out in Hospital A and Hospital B. The research at Hospital A started with a dose audit, revealing that the typical values of CTDIvol and DLP were above the IDRL, and optimization of patient radiation dose was necessary. The optimization strategy at Hospital A involved a gradual selection of exposure factor combinations. In the first stage, a manufactured dedicated water phantom scan was performed with voltage 80, 100, and 120 kVp variations while the current remained constant. Based on image quality evaluation using the Noise Power Spectrum (NPS) method, the lowest NPS was obtained at voltage 120 kV, which was 19,47 HU2mm2. In the second stage, using voltage 120 kVp, a head rando phantom scan was performed with variations of current 100, 150, 200, 250, 300, 350, 400, and 450 mAs. 40% of the radiologists chose the exposure factor combination voltage 120 kVp and current 350 mAs as the combination producing image with the most preferable quality. When comparing the voltage and current combinations before and after optimization with the IDRL, there was a decrease of 7.9% and 2.1% in CTDIvol and DLP. Meanwhile, the dose audit results at Hospital B revealed that the typical value of CTDIvol was already below the IDRL. Still, the typical value of DLP was above the IDRL, so optimization of patient radiation dose for patient-related parameters was necessary. The optimization strategy at Hospital B involved creating new protocols based on exposure factors obtained from image quality evaluation using the NPS method and the interpretation of radiologists. The optimization results with a comparison of four protocols showed that protocol 3 was the most optimal using the exposure factors: collimation 40 × 0.625, the pitch of 0.2, the scan time of 13.8 seconds, Dose Right Index of 25, voltage 120 kVp, and current 144 mAs. The implementation of this protocol contributed to a 67.7% reduction in CTDIvol and a 53.6% reduction in DLP compared to the IDRL. The research objective is to obtain the optimal combination of exposure factors with radiation dosage and image quality as an initial optimization implementation. Keywords: dose audit, radiation protection, optimization, diagnostic reference levels

Modification of 3 MSCT Parameters Using Iterative Reconstruction Techniques for Radiation Dose, Image Quality, and Anatomical Information

Cardiovascular Computed Tomography Angiography (CCTA) examination in diagnosing and evaluating congenital heart disease in pediatrics can make radiation exposure controversial and can lead to cancer risk. Development of parameter settings or modifications, namely tube voltage (kVp), pitch, and rotation time as an effort to optimize radiation dose to produce very low radiation dose. Apart from that, iterative reconstruction techniques are used as a reconstruction method to reduce noise to improve image quality. This study aimed to determine the effect of modifying 3 parameters using the iterative reconstruction technique on radiation dose, image quality, and anatomical information in pediatric CCTA examinations with clinical congenital heart disease at Harapan Kita Heart Hospital. Experimental research with a nonequivalent design. The results of this research are that the modification of 3 MSCT parameters and the iterative reconstruction technique produces a very low radiation dose which is significant at p = 0.000, with an average CTDIvol of 0.314 mGy, DLP 5.518 mGy.cm and can maintain different but not significant image quality, namely p = 0.72 in pulmonary artery SNR, p = 0.88 in ascending aorta SNR, p = 0.37 in pulmonary artery CNR and p = 0.41 in ascending aorta CNR so that it can provide anatomical information on contrast enhancement in the aorta and pulmonary artery area p = 0.02, extra cardiac analysis p = 0.04, contrast filling atria and ventricles p = 0.05, arterial and venous abnormalities p = 0.01, artifacts p = 0.17. Anatomical information is still informative in making a diagnosis. This study used a sample of 30 patients in the control group and intervention group using a purposive sampling method. Modification of 3 MSCT parameters with iterative reconstruction techniques provides an important contribution to the development of safe and informative scanning techniques for diagnosis.

Approaches to Establishing National Diagnostic Reference Levels for Computed Tomography: A Systematic Review

Background: The international commission on radiation protection (ICRP) publican 135 recommends that Diagnostic Reference Levels (DRLs) should be tied to defined technical and patient parameters for the imaging task. Whereas for computed tomography (CT) examinations, DRLs are defined in terms of two established technical parameters namely, Volume-based Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP), a debate has ensued as to whether patient size, age and weight or clinical indication should be used as patient parameters. The objective of diagnostic reference levels (DRLs) is to assist in the optimisation of radiation dose to the patients while maintaining diagnostic image quality. It is generally accepted that each country requires having national DRLs to guide the practice of radiography regarding dose optimization as a prerequisite to good radiation protection practice. Objective: This review aimed to establish commonly used approaches to establishing national diagnostic reference levels for computed tomography. Methods: A systematic literature search in databases containing leading journals in radiography, radiology and medical physics was performed aided by the use of carefully selected search terms that relate to CT and DRLs. The literature search was achieved by the use of the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) flow chart. A total of 109 studies were screened out of which 54 were excluded and 55 sought for retrieval. After further assessment for quality, 20 studies were included in this study for review. Key Findings: 95% of the studies in this review used CTDIvol and DLP as technical parameters indicating dose. 70% of the studies reviewed used patient size, age and weight while 30% used clinical indication as patient parameters. 30% of the reviewed articles did indicate that the surveys to establish NDRLs employed a retrospective approach, while 35% employed a prospective approach and 35% did ..

Establishing national clinical diagnostic reference levels and achievable doses for CT examinations in Brazil: A prospective study

PurposeDiagnostic reference levels (DRL) and achievable doses (AD) are important tools for radiation dose optimization. Therefore, a prospective study was performed which aimed to establish a multi-parametric, clinical indication based – DRL(DRLCI) and clinical indication – AD (ADCI) for adult CT in Brazil. MethodsThe prospective study included 4787 patients (50 ± 18 years old; male:female 2041:2746) at 13 Brazilian sites that have been submitted to head, paranasal sinus, cervical spine, chest, or abdomen-pelvis CT between January and October 2021 for 13 clinical indications. The sites provided the following information: patient age, gender, weight, height, body mass index[BMI], clinical indications, scanner information(vendor, model, detector configuration), scan parameters (number of scan phases, kV, mA, pitch) and dose-related quantities (CT dose index volume- CTDIvol, dose length product- DLP). Median(AD) and 75th(DRL) percentile CTDIvol and DLP values were estimated for each body region and clinical indications. Non-normal data were analyzed with the Kruskal-Wallis test. ResultsIn majority of Brazilian sites, body region and clinical indications based DRLs were at or lower than the corresponding DRLs in the US and higher than Europe. Although radiation doses varied significantly for patients in different body mass index groups (p < 0.001), within each body region, there were no differences in radiation doses for different clinical indications (p > 0.1). Radiation doses for 7/13 clinical indications were higher using iterative reconstruction technique than for the filtered back projection. ConclusionsThere was substantial variation in Brazil DRLCI across different institutions with higher doses compared to the European standards. There was also a lack of clinical indication-based protocol and dose optimization based on different clinical indications for the same body region.

Dose escalation for stereotactic arrhythmia radioablation of recurrent ventricular tachyarrhythmia - a phase II clinical trial

BackgroundStereotactic arrhythmia radioablation (STAR) is delivered with a planning target volume (PTV) prescription dose of 25 Gy, mostly to the surrounding 75–85% isodose line. This means that the average and maximum dose received by the target is less than 35 Gy, which is the minimum threshold required to create a homogenous transmural fibrosis. Similar to catheter ablation, the primary objective of STAR should be transmural fibrosis to prevent heterogenous intracardiac conduction velocities and the occurrence of sustained ventricular arrhythmias (sVA) caused by reentry. We hypothesize that the current dose prescription used in STAR is inadequate for the long-term prevention of sVA and that a significant increase in dose is necessary to induce transmural scar formation.ObjectiveA single arm, multi-center, phase II, dose escalation prospective clinical trial employing the i3 + 3 design is being conducted to examine the safety of a radiation dose-escalation strategy aimed at inducing transmural scar formation. The ultimate objective of this trial is to decrease the likelihood of sVA recurrence in patients at risk.MethodsPatients with ischemic or non-ischemic cardiomyopathy and recurrent sVA, with an ICD and history of ≥ 1 catheter ablation for sVA will be included. This is a prospective, multicenter, one-arm, dose-escalation trial utilizing the i3 + 3 design, a modified 3 + 3 specifically created to overcome limitations in traditional dose-finding studies. A total of 15 patients will be recruited. The trial aims to escalate the ITV dose from 27.0 Gy to an ITV prescription dose-equivalent level of maximum 35.1 Gy by keeping the PTV prescription dose constant at 25 Gy while increasing the dose to the target (i.e. the VT substrate without PTV margin) by step-wise reduction of the prescribing isodose line (85% down to 65%). The primary outcome of this trial is safety measured by registered radiation associated adverse events (AE) up to 90 days after study intervention including radiation associated serious adverse events graded as at least 4 or 5 according to CTCAE v5, radiation pneumonitis or pericarditis requiring hospitalization and decrease in LVEF ≥ 10% as assessed by echocardiography or cardiac MRI at 90 days after STAR. The sample size was determined assuming an acceptable primary outcome event rate of 20%. Secondary outcomes include sVA burden at 6 months after STAR, time to first sVA recurrence, reduction in appropriate ICD therapies, the need for escalation of antiarrhythmic drugs, non-radiation associated safety and patient reported outcome measures such as SF-36 and EQ5D.DiscussionDEFT-STAR is an innovative prospective phase II trial that aims to evaluate the optimal radiation dose for STAR in patients with therapy-refractory sVA. The trial has obtained IRB approval and focuses on determining the safe and effective radiation dose to be employed in the STAR procedure.Trial registrationNCT05594368.