Critical Dose Research Articles

Timeliness in the uptake of hepatitis B birth dose among Indian children under age five: A population-based study

ObjectiveTo assess the timeliness and risk factors for the delay in the uptake of the hepatitis B birth dose among Indian children aged 0–59 months. Information regarding whether the children received the birth dose and the time of receiving it was recorded based on the vaccination card available at the time of the National Family Health Survey (NFHS). MethodsUsing data from the fourth and fifth round of India’s National Family Health Survey (NFHS), the percentage of uptake and timely receipt of the hepatitis B birth dose were obtained by background characteristics and at the sub-national level (state). Multinomial logistic regression analysis was used to examine the risk factors. This study further performed a negative binomial regression estimation to predict the probability of receiving the birth dose at each day within a multivariable framework. ResultsIt was found that approximately 34 % of the children who received the birth dose and the timing of receiving the birth dose was made available through the vaccination card were administered the dose within 24-hours during 2015–16. However, the percentage increased to 51.91 % during 2019–21. During 2019–21, Ladakh had the highest proportion (85.03 %) of children receiving the dose within 24-hours, followed by Jammu & Kashmir with 78 %, and Arunachal Pradesh with 68 %. Mother’s education, economic status of the child’s family and region (children belong from) were found to be significant predictors in delay of receiving the birth dose within 24 hours. ConclusionResults indicated a need for targeted interventions to improve the coverage and timeliness in the uptake of this critical vaccine dose in the country. These interventions could include strategies such as strengthening the healthcare system, improving awareness among parents and healthcare providers, addressing logistical challenges in vaccine delivery, and promoting community engagement and education on importance of timely vaccination.

Intraprocedural, Intra-Arterial CT Foot Perfusion Examination for Assessment of Endovascular Therapy in Patients With Critical Limb Ischemia: A Prospective Pilot Study.

Current techniques to evaluate computed tomography (CT) foot perfusion in patients with critical limb ischemia use high contrast doses and cannot be used during endovascular procedures. CT perfusion of the foot with intra-arterial contrast injection during endovascular treatment in a hybrid angiography CT suite might solve these problems. The main objective of this study was to evaluate whether intra-arterial CT foot perfusion using a hybrid CT angiosystem is feasible during endovascular treatment for critical limb ischemia. This prospective pilot study investigated intraprocedural, intra-arterial CT perfusion of the foot using a hybrid CT angiosystem in 12 patients before and after endovascular treatment for critical limb ischemia. Time to peak (TTP) and arterial blood flow were measured before and after treatment and compared using a paired t test. All 24 CT perfusion maps could be calculated adequately. The contrast volume used for one perfusion CT scan was 4.8 ml. The mean TTP before treatment was 12.8 seconds (standard deviation [SD] 2.8) and the mean TTP posttreatment was 8.4 seconds (SD 1.7), this difference being statistically significant (p=.001). Tendency toward increased blood flow after treatment, 340 ml/min/100 ml (SD 174) vs 514 ml/min/100 ml (SD 366) was noticed (p=.104). The mean effective radiation dose was 0.145 mSv per scan. Computed tomography perfusion of the foot with low contrast dose intra-arterial contrast injection during endovascular treatment in a hybrid angiography CT suite is a feasible technique. Intra-arterial CT foot perfusion using a hybrid CT-angiography system is a feasible new technique during endovascular therapy for critical limb ischemia to assess the results of the treament. Future research is necessary in defining endpoints of endovascular treatment and establishing its role in limb salvage prognostication.

Influence of fluorescent dopants on the vat photopolymerization of acrylate-based plastic scintillators for application in neutron/gamma pulse shape discrimination.

Plastic scintillators, a class of solid-state materials used for radiation detection, were additively manufactured with vat photopolymerization. The photopolymer resins consisted of a primary dopant and a secondary dopant dissolved in a bisphenol A ethoxylate diacrylate-based matrix. The absorptive dopants significantly influence important print parameters, for example, secondary dopants decrease the light penetration depth by a factor > 12 ×. The primary dopant 2,5-diphenyloxazole had minimal impact on the printing process even when loaded at 25 % by mass of the resin. Working curve measurements, which relate energy dose to cure depth, were performed as a function of feature size to further assess the influence of dopants. Photopatterns smaller than 150 μm width had apparent increases in critical energy dose compared to larger photopatterns, while all resins maintained printed features in line gratings with 50 μm of separation. Printed scintillator monoliths were compared to scintillators cast by traditional molding, demonstrating that the layer-by-layer printing process does not decrease scintillation response. A maximum light output of 31 % of a benchmark plastic scintillator (EJ-200) and successful pulse shape discrimination were achieved with 20 % by mass 2,5-diphenyloxazole as the primary dopant and 0.1 % by mass 9,9-dimethyl-2,7-distyrylfluorene as the secondary dopant in printed scintillator samples.

Impact of Sodium Tripolyphosphate on the Rheological Properties of Dams Sediments and Friction Factor during Hydraulic Dredging of Dams

The transporting of sediments across watershed systems and their placement in reservoirs causes expensive issues for the operators of dams in many different nations throughout the world. In addition to the reservoir's functional capacity steadily decreasing as sediment settles in it, silt removal is a sensitive and challenging process that frequently necessitates taking the reservoir out of service, which is practically unachievable in dry and semi-arid regions. De-silting by hydraulic dredging has recently become a necessity to increase their longevity. But during this operation there are load loss exists so it is necessary to find solutions to reduce it. The present paper revealed that use the Sodium Tripolyphosphate as a reducing agent of the friction factor during the hydraulic dredging of dams. To carry out this study, a rheumatic characterization of dams sediments and dams sediments -sodium tripolyphosphate mixtures was carried out using a torque controlled rheometer (Discovery Hybrid Rheometer DHR2 from TA instrument). The flow curves as a function of dose of sodium tripolyphosphate added to dam sediments were analysed by the modified Cross model. It is clearly shown, in this work, when the quantity of sodium tripolyphosphate is less than of 0.4 % causes a decrease in the yield stress, the zero shear rate viscosity (lower Newtonian plateau) and the infinite shear rate viscosity (upper Newtonian plateau). However, when dose of sodium tripolyphosphate is greater than the critical dose, the the yield stress, the zero shear rate viscosity (lower Newtonian plateau) and the infinite shear rate viscosity (upper Newtonian plateau) are increased. As a result, this study find that the increase on thixotropic behavior of dams sediments is occurred by the addition of sodium tripolyphosphate in a concentration ranging between 0.2 wt% and 0.8 wt% to 40 wt% and 45 wt% of dams sediments. The study also demonstrated that adding of 0.4 wt% of sodium tripolyphosphate to 40 wt% and 45 wt% dam sediments decreased the friction factor by 96% and 25% respectively.

Monte Carlo calculations of critical organ doses in radioembolization therapy of primary liver tumors via 90Y microspheres

Monte Carlo calculations of critical organ doses in radioembolization therapy of primary liver tumors via 90Y microspheres

Atomic-scale observation and prediction of gallium ion implantation induced amorphization on natural diamond surface

Gallium ion implantation is an important solution to modify the physical properties of diamonds, in which the critical condition of gallium ion implantation-induced amorphization of diamond has a crucial influence on the modification effect. Therefore, this work attempts to establish an analytical prediction model of the critical implantation dose for diamond amorphization considering the acceleration voltage, implantation angle and crystal orientation. The prediction accuracy of the model is validated with the electron backscatter diffraction pattern technology. The results show that the model has a satisfactory prediction accuracy when the acceleration voltage is higher. Moreover, the atomic-scale observation of gallium ion implantation-induced amorphization of natural diamonds is realized on a spherical aberration projection electron microscope. The results presented in this work are significant to modify the natural diamond tool for service life improvement with focused ion beams in the future as well as to guide doping diamonds to manufacture n-type semiconductor diamonds.

The effect of breath-hold technique on conformal and intensity modulated radiotherapy techniques at right breast cancer radiotherapy including internal mammarian field

Background/Aim: Significantly lower heart doses can be achieved by breath-hold technique at left-sided breast cancer radiotherapy (RT). We see high doses at organs at risk such as lung, heart, and contralateral breast during right-sided breast cancer RT planning especially in the presence of RT indication for mammaria interna (MI) lymph nodes. This study compared RT-planning methods that are conformal with intensity-modulated RT (IMRT) with breath holding and free breathing for right-sided breast cancer RT including full axillary and MI lymph node fields. Methods: Computed tomography (CT) simulations were performed using free-breath (FB) and breath-hold (BH) methods in 10 patients with right-sided breast cancer. A total of 40 RT treatment plans were calculated. Right-sided breast, level 1-2-3 axillary regions, and MI regions served for the target-planning volume. Left-sided breast, heart, as well as right-sided and left lungs were contoured as critical organs according to the atlas of the "Radiation Therapy Oncology Group." We used a Varian Eclipse v.13 for treatment planning. Conformal “FieldinField” RT (FinFRT) and dynamic IMRT (dIMRT) planning were performed separately for each patient over breath-hold and free-breath images. For PTV, 50 Gy was prescribed in 25 fractions and optimized such that the planned target volume (PTV) remained between 95% and 110% of the dose. The mean and maximum doses of the heart, V5 and V20 of the lungs, as well as V95 doses for MI were recorded. Statistical analyses were performed with SPSS version 22, and a paired t-test was used for comparison. Results: Four treatment plans (FB FinFRT, BH FinFRT, FB dIMRT, BH dIMRT) were made separately for 10 patients. For comparison, common FB FinFRT plans were accepted as the baseline plan. As expected, there were no significant differences in PTV coverage. The mean dose received by 95% of the MI volume was between 42.27 Gy and 42.4 Gy. For the maximum heart dose, the breath hold technique had no significant effect on plans. The lowest average maximum heart dose was seen in the BH FinFRT group. Mean heart doses are between 1.28 Gy – 4.85 Gy. There was no significance between BH FinFRT and FB FinFRT plan (P=0.504), and there was a significant difference for heart mean dose versus dIMRT plans (P=0.001). The mean V20 of the lungs ranged from 11.9 to 17.8. There was a significant decrease in V20 with BH or FB dIMRT plans (P=0.001). There was no difference between BH FinFRT (P=0.138). On the contrary, lung V5 values were significantly higher in dIMRT plans, and the lowest mean V5 value was seen in BH FinFRT plan. Conclusion: With the BH method, lower doses (but not significantly lower doses) were obtained in critical organ doses. There was a significant decrease with FinFRT plans in terms of heart mean and maximum dose and lung V5 percentages. The dIMRT plans were significant only in lung V20 percentages. When planning RT, we recommend evaluating all treatment techniques individually for right-sided breast cancer patients to obtain lower doses in critical organs.

Transcriptional, hormonal and histological alterations in the ovaries of BALB/c mice exposed to TCDD in connection with multigenerational female infertility

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic congener of dioxins, has a proven reproductive toxicity. Due to the lack of evidence on the multigenerational female reproductive toxicity of TCDD through the maternal exposure, the current study aims to evaluate, on the one hand, the acute reproductive toxicity of TCDD on adult female pre-gestational exposed to a critical single dose of TCDD (25 μg/kg) for a week (group referred to as AFnG; adult female/non-gestation). On the other hand, the transcription, hormonal and histological effects of TCDD on the females of two generations F1 and F2, were also investigated after the exposure of pregnant females to TCDD on gestational day 13 (GD13) (group referred to as AFG; adult female/gestation). First, our data showed alternations in the ovarian expressional pattern of certain key genes involved in the detoxification of TCDD as well as in the biosynthesis of steroidal hormones. The expression of Cyp1a1 was highly induced in TCDD-AFnG group, but reduced in both F1 and F2. While the transcripts levels of Cyp11a1 and 3βhsd2 were decreased, Cyp19a1 transcripts were increased as a function of TCDD exposure. This was synchronized with a dramatic increase in the level of estradiol hormone in the females of both experimental groups. Beside a significant reduce in their size and weight, ovaries of TCDD-exposed females showed serious histological alterations marked by atrophy of the ovary, congestion in the blood vessels, necrosis in the layer of granular cells, dissolution of the oocyte and nucleus of ovarian follicles. Finally, the female fertility was dramatically affected across generations with a reduced male\\female ratio. Our data indicate that the exposure of pregnant female to TCDD has serious negative effects in the female productive system across generations and suggest the use of hormonal alternation as biomarker to monitor and assess the indirect exposure of these generations to TCDD.

In silico Evaluation of a Vancomycin Dosing Guideline Among Adults with Serious Infections.

This study aimed to compare the achievement of pharmacokinetic-pharmacodynamic (PK-PD) exposure targets for vancomycin using a newly developed dosing guideline with product-information-based dosing in the treatment of adult patients with serious infections. In silico product-information- and guideline-based dosing simulations for vancomycin were performed across a range of doses and patient characteristics, including body weight, age, and renal function at 36-48 and 96 hours, using a pharmacokinetic model derived from a seriously ill patient population. The median simulated concentration and area under the 24-hour concentration-time curve (AUC 0-24 ) were used to measure predefined therapeutic, subtherapeutic, and toxicity PK-PD targets. Ninety-six dosing simulations were performed. The pooled median trough concentration target with guideline-based dosing at 36 and 96 hours was achieved in 27.1% (13/48) and 8.3% (7/48) of simulations, respectively. The pooled median AUC 0-24 /minimum inhibitory concentration ratio with guideline-based dosing at 48 and 96 hours was attained in 39.6% (19/48) and 27.1% (13/48) of simulations, respectively. Guideline-based dosing simulations yielded improved trough target attainment compared with product-information-based dosing at 36 hours and significantly less subtherapeutic drug exposure. The toxicity threshold was exceeded in 52.1% (25/48) and 0% (0/48) for guideline- and product-information-information-based dosing, respectively ( P < 0.001). A Critical care vancomycin dosing guideline appeared slightly more effective than standard dosing, as per product information, in achieving PK-PD exposure associated with an increased likelihood of effectiveness. In addition, this guideline significantly reduced the risk of subtherapeutic exposure. The risk of exceeding toxicity thresholds, however, was greater with the guideline, and further investigation is suggested to improve dosing accuracy and sensitivity.

Exploring the effects of graphene and temperature in reducing electron beam damage: A TEM and electron diffraction-based quantitative study on Lead Phthalocyanine (PbPc) crystals

High-resolution transmission electron microscopy (TEM) of organic crystals, such as Lead Phthalocyanine (PbPc), is very challenging since these materials are prone to electron beam damage leading to the breakdown of the crystal structure during investigation. Quantification of the damage is imperative to enable high-resolution imaging of PbPc crystals with minimum structural changes. In this work, we performed a detailed electron diffraction study to quantitatively measure degradation of PbPc crystals upon electron beam irradiation. Our study is based on the quantification of the fading intensity of the spots in the electron diffraction patterns. At various incident dose rates (e/Å2/s) and acceleration voltages, we experimentally extracted the decay rate (1/s), which directly correlates with the rate of beam damage. In this manner, a value for the critical dose (e/Å2) could be determined, which can be used as a measure to quantify beam damage. Using the same methodology, we explored the influence of cryogenic temperatures, graphene TEM substrates, and graphene encapsulation in prolonging the lifetime of the PbPc crystal structure during TEM investigation. The knowledge obtained by diffraction experiments is then translated to real space high-resolution TEM imaging of PbPc.

Influence of resin composition on rheology and polymerization kinetics of alumina ceramic suspensions for digital light processing (DLP) additive manufacturing

Alumina ceramics with optimized microstructures and mechanical properties were obtained by the attractive digital lighting processing (DLP) additive manufacturing methodology in the present study. A acrylate-based resin system was designed for the alumina powders with a mean particle size of 0.5 μm. The influence of oligomer on the viscosity and polymerization kinetics of the ceramic suspensions has been elaborately discussed by rheology, curing depth and photo-DSC characterizations. The results indicated that the introduction of oligomer has improved the cross-linking density of resins and decreased the critical dose of energy for resin polymerization, which contributed to a tougher ceramic-resin slice with higher dimensional accuracy. Densifying processes including debinding and high temperature sintering of the ceramic parts were conducted according to the TG-DTA characterizations, alumina ceramics with uniform microstructures and eliminated delamination or intralaminar cracks were finally obtained. The flexural strength was 471 MPa for the ceramics obtained from the resin composition containing 20 wt% oligomer, Weibull modulus for the ceramics were determined to be 17.31 by evaluating thirty all sides polished ceramics, indicating the highly uniform property of the ceramics fabricated by DLP additive manufacturing.

Unveiling the Intrinsic Structure and Intragrain Defects of Organic-Inorganic Hybrid Perovskites by Ultralow Dose Transmission Electron Microscopy.

Transmission electron microscopy (TEM) is a powerful tool for unveiling the structural, compositional, and electronic properties of organic-inorganic hybrid perovskites (OIHPs) at the atomic to micrometer length scales. However, the structural and compositional instability of OIHPs under electron beam radiation results in misunderstandings of the microscopic structure-property-performance relationship in OIHP devices. Here, ultralow dose TEM is utilized to identify the mechanism of the electron-beam-induced changes in OHIPs and clarify the cumulative electron dose thresholds (critical dose) of different commercially interesting state-of-the-art OIHPs, including methylammonium lead iodide (MAPbI3 ), formamidinium lead iodide (FAPbI3 ), FA0.83 Cs0.17 PbI3 , FA0.15 Cs0.85 PbI3 , and MAPb0.5 Sn0.5 I3 . The critical dose is related to the composition of the OIHPs, with FA0.15 Cs0.85 PbI3 having the highest critical dose of ≈84 e Å-2 and FA0.83 Cs0.17 PbI3 having the lowest critical dose of ≈4.2 e Å-2 . The electron beam irradiation results in the formation of a superstructure with ordered I and FA vacancies along <110>c , as identified from the three major crystal axes in cubic FAPbI3 , <100>c , <110>c , and <111>c . The intragrain planar defects in FAPbI3 are stable, while an obvious modification is observed in FA0.83 Cs0.17 PbI3 under continuous electron beam exposure. This information can serve as a guide for ensuring a reliable understanding of the microstructure of OIHP optoelectronic devices by TEM.

Dosimetric Comparison of Different Radionuclides Used in Metastatic Bone Disease Treatment.

This study aimed to determine the critical organ doses in 223Ra, 89Sr, 153Sm, and 32P treatments via dosimetry using the phantoms. The OpenDose was used to calculate S values (mGy MBq-1s-1) for bone surface, red bone marrow, urinary bladder wall, testes, ovaries, uterus, and kidneys using male (ICRP110AM) and female (ICRP110AF) phantoms. The cortical thoracic spine was modeled as metastasis. Moreover, the absorbed doses were computed via MIRD formalism according to the activities of 3.3, 148, 2220, and 370 MBq for ICRP110AM and 4.015, 148, 2701, and 370 MBq for ICRP110AF in 223Ra, 89Sr, 153Sm, and 32P treatments, respectively. Whilst the maximum bone surface doses were found as 1.22E+02 and 8.51E+01 mGy at 32P treatment, the minimum bone surface doses were calculated as 8.42E-02 and 8.26E-02 mGy at 223Ra. In terms of the comparison of red bone marrow, urinary bladder wall, and kidney doses, 153Sm and 89Sr treatments showed maximum doses of 2.45E-03, 1.50E-03, 3.23E-07, 5.45E-06, 1.20E-01, 1.49E-01 mGy and the minimum doses with 3.46E-05, 1.99E-05, 6.33E-09, 8.77E-09, 1.19E-04, 1.15E-04 mGy, respectively. The maximum testes and ovaries-uterus doses were found as 6.17E-08, 7.40E-06, 3.46E-07 mGy in 153Sm treatment, and minimum testes and ovaries doses as 1.70E-09, 1.34E-07 mGy in 223Ra. The minimum uterus dose with 7.03E-09 mGy was determined in 89Sr treatment. It is observed that 223Ra produces low critical organ doses in the treatment of painful bone metastasis. Among the beta-emitting radionuclides, 89Sr stands out by showing optimal dosimetric results.

Shattering Effect Study of Aramid–Steel Composite Target Plates under Localized Blast Loading

With the extensive application of composite laminates in protective structures, new materials and new structures have been developed rapidly. As an excellent impact-resistant material, aramid fiber is widely used in the field of protective structures. Aramid laminates show excellent performance in anti-penetration, but there is no research on its anti-explosive characteristics. In this paper, a kind of aramid–steel composite target (ASCT) plate protective structure is proposed innovatively. The failure mode and damage mechanism of three kinds of ASCT plates with equal area density and single-layer steel plates under a local explosion load are studied, and the most effective composite mode is given. The results show that the aramid laminates stuck on the back explosion surface ASCT (SA) exhibit the best anti-explosion effect, which is center deflection reduced by 12% and 18% compared with a single-layer steel plate (S-1) and an equal-thickness steel plate (S-2), respectively. Plate ASCT (SA), plate ASCT (AS), and ASCT (SAS) plate center tear failure did not occur. The analysis shows that different combinations change the propagation of stress waves in the structure, which in turn affects the failure of the composite plate. The critical failure dose of different structural configuration plates is obtained by simulation. The influence of explosion center distance, explosive charge, and bonding thickness of aramid laminate on the central deflection of steel plate was discussed by dimensional analysis, and the empirical formula of central deflection of the aramid–steel composite target plate was obtained. The research results can provide a theoretical basis and reference for the lightweight and efficient protection of composite structural armor.

Optimal Intensity and Duration of Walking Rehabilitation in Patients With Chronic Stroke

For walking rehabilitation after stroke, training intensity and duration are critical dosing parameters that lack optimization. To assess the optimal training intensity (vigorous vs moderate) and minimum training duration (4, 8, or 12 weeks) needed to maximize immediate improvement in walking capacity in patients with chronic stroke. This multicenter randomized clinical trial using an intent-to-treat analysis was conducted from January 2019 to April 2022 at rehabilitation and exercise research laboratories. Survivors of a single stroke who were aged 40 to 80 years and had persistent walking limitations 6 months or more after the stroke were enrolled. Participants were randomized 1:1 to high-intensity interval training (HIIT) or moderate-intensity aerobic training (MAT), each involving 45 minutes of walking practice 3 times per week for 12 weeks. The HIIT protocol used repeated 30-second bursts of walking at maximum safe speed, alternated with 30- to 60-second rest periods, targeting a mean aerobic intensity above 60% of the heart rate reserve (HRR). The MAT protocol used continuous walking with speed adjusted to maintain an initial target of 40% of the HRR, progressing up to 60% of the HRR as tolerated. The main outcome was 6-minute walk test distance. Outcomes were assessed by blinded raters after 4, 8, and 12 weeks of training. Of 55 participants (mean [SD] age, 63 [10] years; 36 male [65.5%]), 27 were randomized to HIIT and 28 to MAT. The mean (SD) time since stroke was 2.5 (1.3) years, and mean (SD) 6-minute walk test distance at baseline was 239 (132) m. Participants attended 1675 of 1980 planned treatment visits (84.6%) and 197 of 220 planned testing visits (89.5%). No serious adverse events related to study procedures occurred. Groups had similar 6-minute walk test distance changes after 4 weeks (HIIT, 27 m [95% CI, 6-48 m]; MAT, 12 m [95% CI, -9 to 33 m]; mean difference, 15 m [95% CI, -13 to 42 m]; P = .28), but HIIT elicited greater gains after 8 weeks (58 m [95% CI, 39-76 m] vs 29 m [95% CI, 9-48 m]; mean difference, 29 m [95% CI, 5-54 m]; P = .02) and 12 weeks (71 m [95% CI, 49-94 m] vs 27 m [95% CI, 3-50 m]; mean difference, 44 m [95% CI, 14-74 m]; P = .005) of training; HIIT also showed greater improvements than MAT on some secondary measures of gait speed and fatigue. These findings show proof of concept that vigorous training intensity is a critical dosing parameter for walking rehabilitation. In patients with chronic stroke, vigorous walking exercise produced significant and meaningful gains in walking capacity with only 4 weeks of training, but at least 12 weeks were needed to maximize immediate gains. ClinicalTrials.gov Identifier: NCT03760016.

Single event performance of FED based SRAMs using numerical simulation

In this work, single event performance of field effect diode (FED) devices have been investigated. Three variations of FED structures have been taken up for the study, and they are, (i) regular FED, (ii) modified FED-I, and (iii) modified FED-II. The study can be split into parts, (i) single event transients (SET) in the FED devices which is used to extract the sensitive location of the device, and (ii) single event upsets in FED-based SRAM cells which is used to extract the critical radiation dose i.e. the minimum dose required to flip the cell content. Among the three FED structures, the collected charge due to SET is maximum in regular FED structure, and the critical dose is minimum in regular FED structure. From the MOSFET literature, it has been found that the single event performances of the MOSFET devices are much superior to the FED devices.

Identification of the effect of ionizing radiation on epichlorohydrin-based homo-, co-, and ter-polymers

In this study, the effects of ionizing radiation on a series of epichlorohydrin (ECH)-based polymers, namely poly(epichlorohydrin) (CO) homopolymer, poly(epichlorohydrin-co-ethylene oxide) (ECO) copolymer, and poly(epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) (GECO) terpolymer, were examined. Polymers are irradiated at room temperature with accelerated electrons in the 0–150 kGy absorbed dose range. The effect of irradiation on the chain structure polymers was examined with sol-gel and rheological analyses. While ECH-based homo- and co-polymers showed crosslinking up to a specific dose, it was found that chain scission above a critical dose value was more dominant. On the other hand, in the ECH terpolymer, crosslinking tendency in the 0–80 kGy dose range was found to be dominant over chain scission. It was found that radiation stability varies depending on the initial molecular mass of the copolymer. Using the Charlesby–Pinner and Charlesby–Rosiak equations for each polymer, the chain scission and crosslink yield ratio (p0/q0), gelation dose (Dg), and virtual gelation dose (Dv) were determined and the effect of ionizing radiation on these polymers, which has increased in use in recent years, was examined. In this study, the effect of ionizing radiation on the long-chain branching value of ECH-based polymers was also examined using a rubber process analyzer (RPA) and large amplitude oscillatory shear testing (LAOS), and a mechanism for the exchange of branching has been proposed.

From organ at risk to target organ: Dosimetric comparison of myocardial stereotactic ablative body radiotherapy between helical tomotherapy and volumetric arc therapy for refractory ventricular tachycardia.

Ventricular tachycardia (VT) is an important type of arrhythmia with a risk of sudden death. Although implanted cardiac defibrillation and radiofrequency ablation are used together with medical treatments for VT, the treatment options are limited in cases that do not respond to them. Stereotactic ablative body radiotherapy (SABR) applied to VT substrates in resistant cases is an emerging treatment with positive results. Such clinical results have increased the interest in this subject. However, the ideal treatment device and method have not yet been described for this therapy, which is generally applied at a single fraction using various devices and methods. Herein, treatment planning was conducted for a total of 8 patients (11 VT substrates) using the Varian TrueBeam EDGE and TomoTherapy Radixact devices at a single center, and the results were compared dosimetrically. The Wilcoxon-signed rank test was used for the statistical analysis, and mean values were expressed as medians and interquartile ranges (IQRs). In the volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) plans, the plan coverages and conformity indexes were similar; meanwhile, the homogeneity indexes were 0.10 (IQR = 0.05) and 0.07 (IQR = 0.05), respectively, and were significantly better in the HT plan (p = 0.02). The gradient indexes were 3.18 (IQR = 0.8) and 5.33 (IQR = 3.68) in the VMAT and HT plans, respectively, and were significantly better in the VMAT plan. For the organs at risk, similar doses were observed. The maximum doses for the stomach and esophagus and the mean doses for the left lung and both lungs were significantly lower in the VMAT plan. Similarly, the maximum and mean doses for the cardiac substructures and great vessels were significantly lower in the VMAT plan. More homogeneous plans were obtained in HT, while a faster dose reduction and lower critical organ dose were observed in VMAT. Reasonable myocardial SABR plans could be obtained with both techniques. The effects of the dosimetric differences on the clinical outcomes should be evaluated in prospective clinical studies.

Pretreatment Spinal Column Dose Estimation for Spinal SBRT Using Octavius Four-dimensional Phantom and Dose-volume Histograms Four-dimensional Feature: A Dosimetric Analysis.

The aim of this study was to estimate the spinal column dose for spinal Stereotactic body radiation therapy (SBRT) before patient treatment using the PTW dosimetry Octavius dose-volume histograms (DVH) four-dimensional (4D) feature. Twenty-three patients were included in the study, and a volumetric modulated arc therapy plan with 6MV flattening filter-free (6FFF) was generated for each patient in the Eclipse planning system using the Anisotropic Analytical Algorithm (AAA) algorithm (Varian Medical Systems, Palo Alto, CA) for the TrueBeam STx LINAC machine. The Octavius 4D system was used to estimate the spinal cord dose by delivering the plans to the 4D phantom. The measured dose was compared with the Eclipse treatment planning system (TPS) (Varian Medical Systems, Palo Alto, CA) dose. The spinal cord max and mean doses estimated using Varisoft DVH 4D are in close agreement with the TPS calculated max and mean doses. The deviation between measured dose and TPS dose is ±5% for the spinal max dose, and the deviation between measured dose and TPS dose is ± 3% for the spinal mean dose. The study demonstrates that the PTW Octavius 4D phantom and DVH 4D feature can be used as a tool to estimate spinal cord dose before the treatment in spinal SBRT plans. The system provides an independent dose measurement that is comparable to the TPS dose. The close agreement between measured and calculated doses validates the use of this system as a critical organ dose verification tool.

Adaptive radiation therapy (art) for patients with limited-stage small cell lung cancer (LS-SCLC): A dosimetric evaluation.

Adaptive radiation therapy (ART) refers to redesigning of radiation therapy (RT) treatment plans with respect to dynamic changes in tumor size and location throughout the treatment course. In this study, we performed a comparative volumetric and dosimetric analysis to investigate the impact of ART for patients with limited-stage small cell lung cancer (LS-SCLC). Twenty-four patients with LS-SCLC receiving ART and concomitant chemotherapy were included in the study. ART was performed by replanning of patients based on a mid-treatment computed tomography (CT)-simulation which was routinely scheduled for all patients 20-25 days after the initial CT-simulation. While the first 15 RT fractions were planned using the initial CT-simulation images, the latter 15 RT fractions were planned using the mid-treatment CT-simulation images acquired 20-25 days after the initial CT-simulation. In order to document the impact of ART, target and critical organ dose-volume parameters acquired from this adaptive radiation treatment planning (RTP) were compared with the RTP based solely on the initial CT-simulation to deliver the whole RT dose of 60 Gy. Statistically significant reduction was detected in gross tumor volume (GTV) and planning target volume (PTV) during the conventionally fractionated RT course along with statistically significant reduction in critical organ doses with incorporation of ART. One-third of the patients in our study who were otherwise ineligible for curative intent RT due to violation of critical organ dose constraints could be treated with full dose irradiation by use of ART. Our results suggest significant benefit of ART for patients with LS-SCLC.