Required Radiation Dose Research Articles

FACT inhibitor CBL0137, administered in an optimized schedule, potentiates radiation therapy for glioblastoma by suppressing DNA damage repair.

Standard-of-care for glioblastoma remains surgical debulking followed by temozolomide and radiation. However, many tumors become radio-resistant while radiation damages surrounding brain tissue. Novel therapies are needed to increase the effectiveness of radiation and reduce the required radiation dose. Drug candidate CBL0137 is efficacious against glioblastoma by inhibiting histone chaperone FACT, known to be involved in DNA damage repair. We investigated the combination of CBL0137 and radiation on glioblastoma. In vitro, we combined CBL0137 with radiation on U87MG and A1207 glioblastoma cells using the clonogenic assay to evaluate the response to several treatment regimens, and the Fast Halo Assay to examine DNA repair. In vivo, we used the optimum combination treatment regimen to evaluate the response of orthotopic tumors in nude mice. In vitro, the combination of CBL0137 and radiation is superior to either alone and administering CBL0137 two hours prior to radiation, having the drug present during and for a prolonged period post-radiation, is an optimal schedule. CBL0137 inhibits DNA damage repair following radiation and affects the subcellular distribution of histone chaperone ATRX, a molecule involved in DNA repair. In vivo, one dose of CBL0137 is efficacious and the combination of CBL0137 with radiation increases median survival over either monotherapy. CBL0137 is most effective with radiation for glioblastoma when present at the time of radiation, immediately after and for a prolonged period post-radiation, by inhibiting DNA repair caused by radiation. The combination leads to increased survival making it attractive as a dual therapy.

FACT inhibitor CBL0137, administered in an optimized schedule, potentiates radiation therapy for glioblastoma by suppressing DNA damage repair.

Standard-of-care for glioblastoma remains surgical debulking followed by temozolomide and radiation. However, many tumors become radio-resistant while radiation damages surrounding brain tissue. Novel therapies are needed to increase the effectiveness of radiation and reduce the required radiation dose. Drug candidate CBL0137 is efficacious against glioblastoma by inhibiting histone chaperone FACT, known to be involved in DNA damage repair. We investigated the combination of CBL0137 and radiation on glioblastoma. In vitro, we combined CBL0137 with radiation on U87MG and A1207 glioblastoma cells using the clonogenic assay to evaluate the response to several treatment regimens, and the Fast Halo Assay to examine DNA repair. In vivo, we used the optimum combination treatment regimen to evaluate the response of orthotopic tumors in nude mice. In vitro, the combination of CBL0137 and radiation is superior to either alone and administering CBL0137 two hours prior to radiation, having the drug present during and for a prolonged period post-radiation, is an optimal schedule. CBL0137 inhibits DNA damage repair following radiation and affects the subcellular distribution of histone chaperone ATRX, a molecule involved in DNA repair. In vivo, one dose of CBL0137 is efficacious and the combination of CBL0137 with radiation increases median survival over either monotherapy. CBL0137 is most effective with radiation for glioblastoma when present at the time of radiation, immediately after and for a prolonged period post-radiation, by inhibiting DNA repair caused by radiation. The combination leads to increased survival making it attractive as a dual therapy.

Abstract 5111: Rational synergistic radiosensitization strategies for group 3 medulloblastoma

Abstract Medulloblastoma (MB) is the most common malignant pediatric brain tumor. MB is comprised of 4 groups, termed Wnt, Shh, Group 3 and Group 4, each characterized by distinct molecular and clinical profiles. MYC-amplified Group 3 MB is associated imminent fatal metastatic relapse following standard treatment approaches, which currently include surgery, craniospinal irradiation and chemotherapy, highlighting an urgent need for identification of therapeutic vulnerabilities for these tumours. As such, using 4 novel patient-derived models of Group 3 MB that faithfully recapitulate the molecular and histological tumor characteristics, we characterised response to radiation of Group 3 MB in vitro to show that these tumors do not possess intrinsic radiation resistance. Furthermore, cumulative radiation experiments do not increase bulk radiation resistance in MB cells, highlighting the contribution of dynamic cell states to radiation response. In contrast, exposure to radiation leads to changes in cell clonogenic capacity as measured by limited dilution assays. Furthermore, RNA-seq data uncovered altered transcriptomic programs in response to cumulative radiation treatment. In particular, we observe differential regulation of genes encoding potassium ion channels and their regulators as well as genes encoding ECM and cell adhesion proteins. As part of our goal to evaluate the current multimodal treatment strategy of MB, we also show that a set of standard chemotherapeutic agents (etoposide, thiotepa and lomustine) currently used in the clinic do not produce a potent response at optimal doses in vitro, potentially accounting for abysmal survival outcomes seen in chemotherapy treated MB patients. As such, we conducted a screen of 144 FDA approved cancer drugs and identified therapeutics that selectively target Group 3 MB cells in contrast to normal tissue controls (foetal neural stem cells) in the low nanomolar dose range. In particular, topoisomerase inhibitor topotecan produces a potent response specific to MYC-amplified Group 3 MB, and sensitizes 2 patient-derived MB models to gamma irradiation. Altogether, our data characterizes Group 3 MB molecular and cellular responses to current treatment modalities and provides rationale for new clinical strategies to sensitize patients to radiation that will potentially allow to reduce the required radiation doses to treat these aggressive tumors, reduce the incidence of radiation treatment-related morbidity as well as improve cure rates. Citation Format: Julija Povilaikaite, Kaitlin Stitz, Nikhita Austin, Vijay Ramaswamy. Rational synergistic radiosensitization strategies for group 3 medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5111.

Reproducible spectral CT thermometry with liver-mimicking phantoms for image-guided thermal ablation

Objectives. Evaluate the reproducibility, temperature tolerance, and radiation dose requirements of spectral CT thermometry in tissue-mimicking phantoms to establish its utility for non-invasive temperature monitoring of thermal ablations. Methods. Three liver mimicking phantoms embedded with temperature sensors were individually scanned with a dual-layer spectral CT at different radiation dose levels during heating (35 °C–80 °C). Physical density maps were reconstructed from spectral results using varying reconstruction parameters. Thermal volumetric expansion was then measured at each temperature sensor every 5 °C in order to establish a correlation between physical density and temperature. Linear regressions were applied based on thermal volumetric expansion for each phantom, and coefficient of variation for fit parameters was calculated to characterize reproducibility of spectral CT thermometry. Additionally, temperature tolerance was determined to evaluate effects of acquisition and reconstruction parameters. The resulting minimum radiation dose to meet the clinical temperature accuracy requirement was determined for each slice thickness with and without additional denoising. Results. Thermal volumetric expansion was robustly replicated in all three phantoms, with a correlation coefficient variation of only 0.43%. Similarly, the coefficient of variation for the slope and intercept were 9.6% and 0.08%, respectively, indicating reproducibility of the spectral CT thermometry. Temperature tolerance ranged from 2 °C to 23 °C, decreasing with increased radiation dose, slice thickness, and iterative reconstruction level. To meet the clinical requirement for temperature tolerance, the minimum required radiation dose ranged from 20, 30, and 57 mGy for slice thickness of 2, 3, and 5 mm, respectively, but was reduced to 2 mGy with additional denoising. Conclusions. Spectral CT thermometry demonstrated reproducibility across three liver-mimicking phantoms and illustrated the clinical requirement for temperature tolerance can be met for different slice thicknesses. The reproducibility and temperature accuracy of spectral CT thermometry enable its clinical application for non-invasive temperature monitoring of thermal ablation.

Protocol of the HISTOTHERM study: assessing the response to hyperthermia and hypofractionated radiotherapy in recurrent breast cancer.

Breast cancer is globally the leading cancer in women, and despite the high 5-year survival rate the most frequent cause of cancer related deaths. Surgery, systemic therapy and radiotherapy are the three pillars of curative breast cancer treatment. However, locoregional recurrences frequently occur after initial treatment and are often challenging to treat, amongst others due to high doses of previous radiotherapy treatments. Radiotherapy can be combined with local hyperthermia to sensitize tumor cells to radiation and thereby significantly reduce the required radiation dose. Therefore, the combination treatment of mild local hyperthermia, i.e. locally heating of the tissue to 39-43°C, and re-irradiation with a reduced total dose is a relevant treatment option for previously irradiated patients. The mechanisms of this effect in the course of the therapy are to date not well understood and will be investigated in the HISTOTHERM study. Patients with local or (loco)regional recurrent breast cancer with macroscopic tumors are included in the study. Local tumor control is evaluated clinically and histologically during the course of a combination treatment of 60 minutes mild superficial hyperthermia (39 - 43°C) using water-filtered infrared A (wIRA) irradiation, immediately followed by hypofractionated re-irradiation with a total dose of 20-24 Gy, administered in weekly doses of 4 Gy. Tumor and tumor stroma biopsies as well as blood samples will be collected prior to treatment, during therapy (at a dose of 12 Gy) and in the follow-up to monitor therapy response. The treatment represents the standard operating procedure for hyperthermia plus re-irradiation. Various tissue and blood-based markers are analyzed. We aim at pinpointing key mechanisms and markers for therapy response which may help guiding treatment decisions in future. In addition, quality of life in the course of treatment will be assessed and survival data will be evaluated. The study is registered at the German Clinical Trials Register, Deutsches Register Klinischer Studien (DRKS00029221).

Choosing a breast reconstruction method when planning radiotherapy in breast cancer patients

The list of indications to adjuvant radiation therapy for breast cancer patients was extended in recent years, regardless of the type of reconstruction. Surgeons and radiologists have to choose the most appropriate sequence of reconstruction and to reduce the risk of complications. Radiotherapy is one of the main factors causing complications in patients undergoing breast reconstruction, and vice versa, the implant might hinder radiotherapy, preventing proper delivery of the required radiation dose. Both oncologists and radiologists try to reduce the incidence of complications, which is an important interdisciplinary aim. This article investigates international experience of well-known cancer centers and experience of the Department of Oncology and Reconstructive Breast and Skin Surgery, P.A. Herzen Moscow Oncology Research Institute, a branch of the National Medical Radiology Research Center, Ministry of Health of Russia. We analyzed the choice of the breast reconstruction method in patients undergoing radiotherapy after surgery and developed recommendations for choosing an optimal method of reconstructive surgery.

ANALYSIS OF EXISTING ENERGY INSTALLATIONS FOR ULTRAVIOLET DISINFECTION OF RECIRCULATING NUTRIENT SOLUTION IN SYSTEMS OF CROPS AUTOMATIC HYDROPONIC IRRIGATION IN PROTECTED GROUND

Decisive for solving food security problems in Ukraine while preserving and restoring the ecology of the environment should be an intensive method of management, i.e. the orientation of economic entities of their own activities on the innovative type of development, active use of scientific and technical developments and implementation of modern agricultural innovations. In its turn, the qualitative and quantitative indicators of crop production of protected soil depend on the technical condition of technological equipment.
 The purpose of the work is research and analysis of existing power plants for ultraviolet disinfection of recirculating nutrient solution in systems of automatic hydroponic irrigation of crops in a protected soil, as well as elucidation of the impact of filtration and disinfection of nutrient solution on the presence of microorganisms when reusing plants in systems. The paper investigates the ways to improve the operation of power plants for ultraviolet disinfection of recirculating nutrient solution in the cultivation of crop products of protected soil. It provides the value of the required radiation dose for 90% disinfection of the recirculation solution from various bacteria, viruses and fungal spores and the dependence of bactericidal efficiency on the wavelength of light. Ultraviolet rays with a length from 200 to 280 nm (UV-C range) have the most pronounced bactericidal effect. Research in this area has shown that the optimal wavelength for irradiation is 253.7 nm. As a result of such irradiation, microorganisms die or lose their ability to reproduce. It has been proven that the classical layout scheme of power plants for ultraviolet disinfection of the recirculation solution is inefficient, because it does not rid the recirculation solution of turbidity and the presence of iron and does not guarantee high efficiency of the ultraviolet disinfection plants. The paper describes the method of carbonate precipitation of metal ions, which is based on the formation of insoluble metal compounds as a result of treatment of an aqueous solution with carbonates or bicarbonates of alkali metals. Prospects for further research are the development of methods and tools to improve the operation of power plants for ultraviolet disinfection of recirculating nutrient solution in the cultivation of crop products of protected soil.

Optimizing the Small Animal Radiation Research Platform (SARRP) for High-Dose Rate Focal Irradiation Studies

<h3>Purpose/Objective(s)</h3> The objective of the study is to enable high-dose rate focal irradiation in small animal models through modification of a commercial small animal radiation research platform (SARRP), which is widely used by investigators for preclinical research in radiation oncology. Small animal pre-clinical research is a fundamental part of clinical translation of novel treatment techniques. Currently, the SARRP system only enables dose rate of 3.5 Gy/min at the nominal isocenter. However, preclinical studies to investigate SBRT ablative models, such as those for the lung, liver, and more recently the heart, require much higher dose rates (ideally at least 10-20 Gy/min) and the current SARRP system setup requires long anesthesia time to deliver the required radiation dose to the animals. In addition, emerging applications such as lattice SBRT for larger tumors (which requires the delivery of a large grid of focal irradiation spots in a short time), is currently impossible with the current SARRP system. Here, we present our work to optimize the SARRP system using a modified beam collimation system to allow high-dose rate focal irradiation studies <i>in vivo</i>, while enabling a highly flexible set of collimator sizes and shapes to be used. <h3>Materials/Methods</h3> A commercial SARRP system with nominal source-to-axis distance (SAD) of 35 cm was studied in this work. In order to be able to perform experiments at a higher dose rate, a dedicated beam collimation apparatus was designed to provide a short source-to-surface distance (SSD) of 14 cm. Measurements were performed using an ionization chamber and radiochromic film dosimeter to measure the dose rate using the original beam collimation assembly at the isocenter (35 cm SSD), and using our dedicated beam collimation assembly at 14 cm SSD. Measurements were at the surface and at 2 cm depth in phantom with and without the x-ray filter in place. <h3>Results</h3> The SARRP system with standard collimation assembly provides a dose rate of 3.5 Gy/min at 2 cm depth in phantom at 35 cm SAD. The dose rate measured using our apparatus increased by a factor of 4.9, reaching 17 Gy/min, at 14 cm SSD and 2 cm depth in phantom. Removing the x-ray filter would additionally increase the dose rate by another factor of 6 at the surface and 1.7 at 2 cm depth in phantom. <h3>Conclusion</h3> The SARRP system with our modified collimation system would allow <i>in vivo</i> experiments with dose rates of 17-29 Gy/min at 14 cm SSD.

Almost zero-fluoroscopy LBBP-procedure using a 3D-mapping system

Abstract Introduction Cardiac device therapy has recently been extended by the option of Conduction System Pacing, CSP (HIS Bundle Pacing, HBP; Left Bundle Branch Area Pacing, LBBAP). Similar to cardiac resynchronization therapy (CRT), complex procedures can result in long fluoroscopy-duration and considerable radiation exposure for the patient and the implanting team. According to the principle ALARA (As Low As Reasonably Achievable), measures should be taken to reduce radiation, wherever possible. We report the almost fluoroscopy-free implantation of a LBBAP-system using a 3D electroanatomical mapping system (EAMS). The patient was indicated for a pace &amp; ablate concept due to recurrent, highly symptomatic, persistent atrial fibrillation (AF), a history of mitral valve repair and a severely dilated left atrium. ESC guidelines suggest choosing a RV-lead (indication IIa), alternatively either a CRT system or HBP (both IIb). LBBAP as new option for physiological pacing was chosen in this patient because it usually provides excellent stimulation thresholds and the lead – in contrast to HBP – is distant from Koch's triangle, so that AV-nodal-ablation can be performed safely. Methods Surgery was performed under deep sedation. After accessing the cephalic vein, a quick 3D map of relevant structures was acquired (right atrium; coronary sinus; HIS; interventricular septum, IVS). Then a preformed sheath and a stylet-driven pacemaker-lead were advanced. The lead-tip was visualized within the EAMS and maneuvered without fluoroscopy. After approaching the proximal IVS, the implantation site was confirmed by unipolar stimulation and the lead was advanced into the IVS under close monitoring of impedance and signals. Final position was confirmed by sheath-angiography [Fig. 1]. Results During lead fixation, LBBAP-typical ECG-changes (progression to rSR morphology, fixation beats) could be observed. A left bundle branch potential (poLBB) could be documented. The left ventricular activation time (LVAT) as a marker of rapid LV-excitation was shortened from 108 ms to 68 ms. Thresholds for non-selective and selective LBBP were 3 V @ 1 ms and 0.7 V @ 0.4 ms, with a sensing of 8.7 mV, impedance of 643 ohms and a paced QRS-width of 112 ms [Fig. 2]. An atrial lead was added (history of intermittent sinus rhythm) and a dual-chamber pacemaker was connected. Fluoroscopy was required for lead fixation into the IVS, atrial lead placement as well as for sheath angiography and lead length-optimization. Total fluoroscopy time was 1.13 minutes with a radiation dose of 45.04 μGy m2, procedure time 64 minutes. AVN total ablation was performed the following day without complications. Conclusions CSP using a 3D mapping system is simple, facilitates understanding of important anatomical structures and helps to reduce the required radiation dose to a necessary minimum. In individual cases, procedures requiring almost zero-fluoroscopy are possible. Funding Acknowledgement Type of funding sources: None.

The influence of thyroid hormone medication on intra-therapeutic half-life of 131I during radioiodine therapy of solitary toxic thyroid nodules

Despite a significantly improved dietary iodine supply, solitary toxic thyroid nodules (STN) are still a common clinical problem in former iodine deficient areas. Radioiodine treatment (RIT) is a well-established therapeutic option with few side effects and high success rates. As radioiodine biokinetics are individual for every patient, the necessary activity has to be calculated individually by a pre-therapeutic measurement of the intra-therapeutic effective half-life (EHL) in a radioiodine uptake test (RIUT). A suppressive medication with triiodothyronine (T3) or tetraiodothyronine (T4) is often needed to suppress uptake in normal thyroid tissue. Therefore, the aim of this study was to quantify the possible influence of this medication on intra-therapeutic radioiodine biokinetics. A cohort of 928 patients with STN undergoing RIUT and RIT was analysed. Patients were subdivided into 3 groups. Group T3: medication with T3 (n = 274), group T4: medication with T4 (n = 184) and group NM: no additional medication (n = 470). The T3 and T4 subgroups were further subdivided depending on the dose of thyroid hormone medication. In order to analyse the influence of thyroid hormone medication on individual intra-thyroidal biokinetics, the variance of the determined individual EHL between RIUT and RIT within the single groups and within the subgroups was investigated. EHL was significantly decreased between RIUT and RIT in the T3 and T4 subgroups (EHL: T3: 5.9 ± 1.1 d in RIUT and 3.3 ± 1.4 d in RIT (− 43%) (p < 0.05); T4: 5.9 ± 1.2 d in RIUT and 3.4 ± 1.5 d in RIT (− 42%) (p < 0.05). The decrease of EHL did not differ statistically between T3 or T4. However, both showed a highly significant difference compared to the NM group (p < < 0.05). A further subgroup analysis showed a significant dependence of the decrease in EHL related to the dose of thyroid hormone medication of 35–58% (T3) and 15–67% (T4) (p < 0.05). A significantly reduced EHL compared to RIUT in patients receiving thyroid hormone medication was detected. Moreover, a significant correlation between the dose of thyroid hormone medication (T3 or T4) and the decrease of EHL was found. Therefore, an adaption of the calculated activity should be considered in RIUT to obtain the required radiation dose in RIT of patients suffering from STN.

An Image Quality-informed Framework for CT Characterization.

Background Lack of standardization in CT protocol choice contributes to radiation dose variation. Purpose To create a framework to assess radiation doses within broad CT categories defined according to body region and clinical imaging indication and to cluster indications according to the dose required for sufficient image quality. Materials and Methods This was a retrospective study using Digital Imaging and Communications in Medicine metadata. CT examinations in adults from January 1, 2016 to December 31, 2019 from the University of California San Francisco International CT Dose Registry were grouped into 19 categories according to body region and required radiation dose levels. Five body regions had a single dose range (ie, extremities, neck, thoracolumbar spine, combined chest and abdomen, and combined thoracolumbar spine). Five additional regions were subdivided according to dose. Head, chest, cardiac, and abdomen each had low, routine, and high dose categories; combined head and neck had routine and high dose categories. For each category, the median and 75th percentile (ie, diagnostic reference level [DRL]) were determined for dose-length product, and the variation in dose within categories versus across categories was calculated and compared using an analysis of variance. Relative median and DRL (95% CI) doses comparing high dose versus low dose categories were calculated. Results Among 4.5 million examinations, the median and DRL doses varied approximately 10 times between categories compared with between indications within categories. For head, chest, abdomen, and cardiac (3 266 546 examinations [72%]), the relative median doses were higher in examinations assigned to the high dose categories than in examinations assigned to the low dose categories, suggesting the assignment of indications to the broad categories is valid (head, 3.4-fold higher [95% CI: 3.4, 3.5]; chest, 9.6 [95% CI: 9.3, 10.0]; abdomen, 2.4 [95% CI: 2.4, 2.5]; and cardiac, 18.1 [95% CI: 17.7, 18.6]). Results were similar for DRL doses (all P < .001). Conclusion Broad categories based on image quality requirements are a suitable framework for simplifying radiation dose assessment, according to expected variation between and within categories. © RSNA, 2021 See also the editorial by Mahesh in this issue.

SIMPLE METHOD OF MEASURING SSDE FOR HEAD CT: FACILITATING PRE-CT SCAN DOSE CALCULATION USING SPECIALIZED HEAD SCAN BAND

In this study, scaled scan band was developed to provide size-specific dose estimation (SSDE) values based on head circumference of patients undergoing computed tomography (CT) scans. The scan band was tested in 40 consecutive head CT examinations. The accuracy of the specialized scan band method was determined by comparing SSDEband with SSDE293,forehead, SSDEmean and SSDEcenter. SSDE293,forehead was used as the control value. The results of the linear fit of SSDEband, SSDEmean and SSDEcenter against SSDE293, forehead, were R2=0.958, R2=0.984 and R2=0.936, respectively. There was no significant difference between SSDEband, SSDEmean and SSDEcenter for SSDE293,forehead. Use of the proposed scan band method makes it possible to accurately determine the required radiation dose before a CT examination is performed.

High Intensity Violet Light (405 nm) Inactivates Coronaviruses in Phosphate Buffered Saline (PBS) and on Surfaces

It has been proven that visible light with a wavelength of about 405 nm exhibits an antimicrobial effect on bacteria and fungi if the irradiation doses are high enough. Hence, the question arises as to whether this violet light would also be suitable to inactivate SARS-CoV-2 coronaviruses. Therefore, a high-intensity light source was developed and applied to irradiate bovine coronaviruses (BCoV), which are employed as SARS-CoV-2 surrogates for safety reasons. Irradiation is performed in virus solutions diluted with phosphate buffered saline and on steel surfaces. Significant virus reduction by several log levels was observed both in the liquid and on the surface within half an hour with average log reduction doses of 57.5 and 96 J/cm2, respectively. Therefore, it can be concluded that 405 nm irradiation has an antiviral effect on coronaviruses, but special attention should be paid to the presence of photosensitizers in the virus environment in future experiments. Technically, visible violet radiation is therefore suitable for coronavirus reduction, but the required radiation doses are difficult to achieve rapidly.

Influence of the use of various imaging units and projections on the radiation dose received by children during chest digital radiography.

ObjectiveTo investigate the impact of the use of different imaging units and projections on radiation dose and image quality during chest digital radiography (DR) in 3- and 4-year-old children.MethodsTwo hundred forty 3- and 4-year-old participants requiring chest DR were included; they were divided into three groups: supine anterior-posterior projection (APP), standing APP and standing posterior-anterior projection (PAP). Each group included 40 participants who were evaluated using the same imaging unit. The dose area product (DAP) and the entrance surface dose (ESD) were recorded after each exposure. The visual grading analysis score (VGAS) was used to evaluate image quality, and the longitudinal distance (LD) from the apex of the right lung to the apex of the right diaphragm was used to evaluate the inspiration extent.ResultsDAP and ESD were significantly lower in the standing PAP and APP groups than in the supine APP group (P<0.05), but LD was significantly higher in the standing PAP and APP groups than in the supine APP group (P<0.05). Additionally, the pulmonary field area was significantly higher for the standing PAP group than for the standing and supine APP groups (P<0.05). The correlations between ESD, DAP, and VGAS were positive (P<0.001), showing that larger ESD and DAP correspond to higher VGAS. The correlations between ESD, DAP, and body mass index (BMI) were also positive (P<0.05), indicating that higher BMI corresponds to larger ESD and DAP. Finally, no differences in DAP, ESD, VGAS, LD, pulmonary field area, or BMI were noted between males and females (P>0.05).ConclusionThe radiation dose to superficial organs may be lower with standing PAP than with standing APP during chest DR. Standing PAP should be selected for chest DR in 3- and 4-year-old children, as it may decrease the required radiation dose.

Enhancing microwave breast cancer hyperthermia therapy efficiency utilizing fat grafting with horn antenna

A breast cancer hyperthermia system has been developed for the targeted of increasing hyperthermia therapy efficiency after lumpectomy surgery with the assistance of fat grafting technique. Enhancing the efficiency of hyperthermia treatment will decrease the required radiation doses after surgery. A fat grafting technique is applied around the tumor region that is located into glandular tissue for the purpose of enhancing wave penetration through glandular tissue. The proposed hyperthermia system employs a single horn antenna operating at 2.45 GHz. Here, a modified hyperthermia system was tested on a hemisphere phantom of two different densities with various tumor sizes at depth 2.8 cm from skin layer. Transmission and reflection coefficients of applied electromagnetic waves at the air-phantom interface were calculated analytically. Based on these computations, an external dielectric matched layer was added on the skin layer of breast to decrease reflection that would occur at the skin layer because of the difference in permittivity values. The experiments were conducted on a 3-D phantom that has the realistic dielectric properties using the available laboratory capability. Measured and simulated results confirmed the system ability to increase the diseased region temperature using fat grafting technique with a dielectric matched layer without increasing the system input power.

RDIa regression detectability index for quality assurance in: x-ray imaging

Novel iterative image reconstruction methods can help reduce the required radiation dose in x-ray diagnostics such as computed tomography (CT), while maintaining sufficient image quality. Since some of the established image quality measures are not appropriate for reliably judging the quality of images derived by iterative methods, alternative approaches such as task-specific quality assessment would be highly desirable for acceptance or constancy testing. Task-based image quality methods are also closer to tasks performed by the radiologists, such as lesion detection. However, this approach is usually hampered by a huge workload, since hundreds of images are usually required for its application. It is demonstrated that the proposed approach works reliably on the basis of significantly fewer images, and that it correlates well with results obtained from human observers.

Gadolinium-Based Nanoparticles for Theranostic MRI-Guided Radiosensitization in Hepatocellular Carcinoma.

Background: Radiation therapy (RT) of hepatocellular carcinoma (HCC) is limited by low tolerance of the liver to radiation, whereas radiosensitizers are effective in reducing the required radiation dose. Multimodality gadolinium-based nanoparticles (AGuIX) are small and have enhanced permeability and retention effects; thus, they are very suitable for radiation sensitizer HCC RT. Here, we evaluated the potential value of AGuIX for theranostic MRI-radiosensitization in HCC.Methods: The radiosensitization effects of AGuIX were evaluated via in vitro and in vivo experiments. Tumor growth, apoptosis imaging, and immunohistochemistry were performed to verify the antitumor effects of RT with AGuIX.Results: In vitro evaluation of the efficacy of radiosensitivity of the AGuIX demonstrated that the presence of AGuIX significantly decreased HepG2 cell survival when combined with an X-ray beam. In vivo MRI imaging showed the ratio of tumor/liver concentration of the AGuIX was the highest 1 h after intravenous injection. For antitumor effects, we found that the tumor size decreased by RT-only and RT with AGuIX. The antitumor effects were more effective with high-dose AGuIX-mediated RT. Apoptosis imaging and immunohistochemistry both demonstrated that the degree of the cell apoptosis was highest with a high dose of AGuIX-mediated RT.Conclusions: This study provides compelling data that AGuIX can facilitate theranostic MRI-radiosensitization in HCC.

Quantitative analysis of regional endocardial geometry dynamics from 4D cardiac CT images: endocardial tracking based on the iterative closest point with an integrated scale estimation

Regional cardiac function analysis is important for the diagnosis and treatment planning of ischemic heart disease, but has not been sufficiently developed in the field of computed tomography (CT). Therefore, we propose a 3D endocardial tracking framework for cardiac CT using local point cloud registration based on the iterative closest point with an integrated scale estimation algorithm. We also introduce regional function descriptors that express the curvature and stretching of the endocardium: Surface distortion (E) and Scaling rate (S). For a region-to-region comparison, we propose endocardial segmentation according to coronary perfusion territories defined by the Voronoi partition based on coronary distribution. Our study of 65 endocardial segments in ten subjects showed that global endocardial deformation has a positive relationship with the stroke volume index (r = 0.896 and 0.829 in and , respectively) and ejection fraction (r = 0.804 and 0.835), and a positive relationship with the brain natriuretic peptide level (r = 0.690 and 0.776). A positive relationship between segmental E and S (r = 0.845), a higher value of E in ischemic segments (p = 0.021) that are determined by fractional flow reserve estimated from coronary CT data, and a higher value of S in the left circumflex artery territory (p < 0.05) were also observed. The required radiation dose was 5.0 ± 0.7 mSv and the computation time was 7.2 ± 1.1 min. The result suggests that proposed endocardial deformation analysis using CT can be conducted on site and in time for the acute setting, and may be useful for the diagnosis of cardiac dysfunction or myocardial ischemia.

Observers Agreement in Perception of Non-Cavitated Approximal Dental Caries by Intraoral Digital CCD Radiography at Different Exposure Parameters and Corresponding Required Radiation Dose

Objectives: To evaluate the diagnostic accuracy of Charged Coupled device (CCD) in detection of Non- Cavitated Approximal caries at different exposure parameters in relation to radiation dose in vitro. Study Design: Seventy-eight surfaces of extracted teeth were inserted in acid gel to create non-cavitated proximal caries with different depth, and then Radiographs have been taken to all teeth by CCD sensor. Radiographs were interpreted by three observers. The lesions were classified as (N) No lesion, (D1) Less than ½ enamel thickness, (D2) more than halfway of enamel but not involve DEJ. (D3) Dentin caries. Teeth were randomly selected for histological analysis after consensus from three oral and maxillofacial radiologists as Gold standard. The corresponding radiation dose was measured by unfors meter device at different exposure parameters. Results: The histological examination showed that the distribution of lesions was 39.8% Sound, both enamel lesions are equal 17.8%, Dentin lesions 24.6. The sensitivity and specificity of CCD to detect normal surfaces were 0.95, D1 was 0.37, D2 was 0.74 and D3 was 0.86. As the lesions depth increased, the sensitivity increased. The higher image quality was produced by using exposure parameters (70 KvP, 160 ms) and (70 KvP, 200 ms). While, (60 KvP, 200 ms) and (60 KvP, 250 ms) produced the worse image quality. Conclusion: Regard the balance between the higher diagnostic accuracy of digital images and minimum radiation dose: using exposure parameters as (70 KvP, 160 ms) is considered the best image quality and relative dose (81 mSv). While, (70 KvP, 125ms) and (66 KvP, 160 ms) are little bit lower quality and corresponding dose are (63), (73) respectively. Although (70 KvP, 200 ET) produce higher image quality but its relative dose is high (101mSv).

Relative merits and limiting factors for x-ray and electron microscopy of thick, hydrated organic materials

Electron and x-ray microscopes allow one to image the entire, unlabeled structure of hydrated materials at a resolution well beyond what visible light microscopes can achieve. However, both approaches involve ionizing radiation, so that radiation damage must be considered as one of the limits to imaging. Drawing upon earlier work, we describe here a unified approach to estimating the image contrast (and thus the required exposure and corresponding radiation dose) in both x-ray and electron microscopy. This approach accounts for factors such as plural and inelastic scattering, and (in electron microscopy) the use of energy filters to obtain so-called “zero loss” images. As expected, it shows that electron microscopy offers lower dose for specimens thinner than about 1 µm (such as for studies of macromolecules, viruses, bacteria and archaebacteria, and thin sectioned material), while x-ray microscopy offers superior characteristics for imaging thicker specimen such as whole eukaryotic cells, thick-sectioned tissues, and organs. The required radiation dose scales strongly as a function of the desired spatial resolution, allowing one to understand the limits of live and frozen hydrated specimen imaging. Finally, we consider the factors limiting x-ray microscopy of thicker materials, suggesting that specimens as thick as a whole mouse brain can be imaged with x-ray microscopes without significant image degradation should appropriate image reconstruction methods be identified.