Tissue Dose Research Articles

Using Lithium-6 Filter for Study of Dose Distribution with Max. and Min. Displacement of Prostate Inside the Body by BNCT Method

Physical dose assessment of prostate tumor and adjacent healthy tissues in ORNL, adult male (AM) and KTMAN-2 phantoms was performed using the Monte Carlo transport code. Two different spectra of MIT reactor (without and with lithium filter) were considered. To evaluate the effectiveness of this method in destroying cancer cells for different depths of the prostate, the prostates were moved three times with a distance of 3 cm towards the surface of the body. In addition, the effects of using a lithium filter with different thicknesses on the physical doses of the prostate and adjacent healthy tissues were investigated. It has been observed that decreasing the depth of the prostate increases the physical dose received by the tumor. When the prostate is placed at the maximum depth inside the body, the tissues located in the path of the beam receive the maximum amount of dose. However, the use of a lithium filter reduces damage to healthy tissues, so that when the prostate is near the surface of the body, the lithium filter increases the amount of dose delivered to tumors. In these conditions, the average energy of the penetration distance of epithermal neutrons and neutrons in tissues increases. By changing the location of the prostate gland inside the body, the physical doses of normal tissues did not change, but it was observed that increasing the thickness of the lithium filter significantly reduced the dose of normal tissues.

Motion-Inclusive Treatment Planning to Assess Normal Tissue Dose for Central Lung Stereotactic Body Radiation Therapy

PurposeFor lung SBRT, 4DCT is often used to delineate target volumes, whereas organs at risk (OARs) are typically outlined on either average intensity projection (AIP) or mid-ventilation (MidV = 30% phase) images. AIP has been widely adopted as it represents a true average, but image blurring often precludes accurate contouring of critical structures such as central airways. Here we compare AIP vs MidV planning for centrally located tumors via respiratory motion-inclusive (RMI) plans to better evaluate dose delivered throughout the breathing cycle. MethodsIndependently contoured and optimized AIP and MidV plans were created for 16 treatments and rigidly copied to each of the 10 breathing phase-specific CT image sets. Resulting dose distributions were deformably registered back to the MidV image set (used as reference due to clearer depiction of anatomy compared to motion-blurred AIP) and averaged to create RMI plans. Doses to central OARs were compared between plans. ResultsMean absolute dose differences were low for all comparisons (range 0.01 – 2.87 Gy), however, individual plans exhibited differences > 20 Gy. Dose differences >5 Gy were observed most often for plan comparisons involving AIP-based plans (MidV vs AIP 23, AIP RMI vs AIP 12, MidV RMI vs AIP RMI 7, and MidV RMI vs MidV 8 times). Inclusion of respiratory motion reduced large dose differences. Standard OAR thresholds were exceeded up to five times for each plan comparison scenario and always involved PBT D4cc tolerance dose. AIP-based contours were larger by on average 3-15%. ConclusionLarge dose differences were observed when plans with AIP-based contours were compared with MidV-based contours indicating that observed dose differences were likely due to contoured volume differences rather than the effect of motion. Because of blurring with AIP images, MidV RMI-based planning may offer a more accurate method to determine dose to critical OARs in the presence of respiratory motion.

β-delayed multiple-particle emitters minibeam radiation therapy: first dosimetric evaluation with Monte Carlo simulations

Radiation therapy, one of the most effective methods for cancer treatment, is still limited by the tolerances of normal tissues surrounding the tumor. Innovative techniques like spatially fractionated radiation therapy (SFRT) have been shown to increase normal tissue dose resistance. Heavy ions also offer high-dose conformity and increased relative biological effectiveness (RBE) when compared to protons and X-rays. The alliance of heavy ions and spatial fractionation of the dose has the potential to further increase the therapeutic index for difficult-to-treat cases today. In particular, the use of β-delayed multiple-particle emitters might further improve treatment response, as it holds the potential to increase high linear energy transfer (LET) decay products in the valleys of SFRT (low-dose regions) at the end of the range. To verify this hypothesis, this study compares β-delayed multiple-particle emitters (8Li, 9C, 31Ar) with their respective stable isotopes (7Li, 12C, 40Ar) to determine possible benefits of β-delayed multiple-particle emitters minibeam radiation therapy (β-MBRT). Monte Carlo simulations were performed using the GATE toolkit to assess the dose distributions of each ion. RBE-weighted dose distributions were calculated and used for the aforementioned comparison. No significant differences were found among carbon isotopes. In contrast, 8Li and 31Ar exhibited improved RBE-weighted dose distributions with an approximately 12–20% increase in the Bragg-peak-to-entrance dose ratio (BEDR) for both peaks and valleys, which favors tissue sparing. Additionally, 8Li and 31Ar exhibited a lower peak-to-valley dose ratio (PVDR) in normal tissues and higher PVDR in the tumor than 7Li and 40Ar. Biological experiments are needed to conclude whether the differences observed make β-delayed multiple-particle emitters advantageous for MBRT.

Assessment of the potential threats to brain health posed by the radiation from 5G sub-6GHz base stations in China using dosimetric methods.

The 5G sub-6GHz radio frequency (RF) electromagnetic fields (EMF) are the most widely used in China's communications. The public has expressed concerns about possible brain health effects of the higher frequency bands in 5G compared to 2G, 3G, and 4G bands. It is imperative to empirically investigate the potential health hazards of these novel frequency bands in 5G communication technology. This study evaluates the assessment of brain tissue dose coupling from sub-6GHz band EMF emitted by base stations in China. Based on the 3D virtual human body model, the simulation environment was established. Dose including specific absorption rate (SAR) and internal electric field (IEF) between 2G, 3G, and 4G bands and 5G sub-6GHz was investigated using normalized exposure values and exposure limits. The results indicate that the sub-6GHz high-frequency band of 5G has the lowest dose value. It can be concluded that high-frequency electromagnetic radiation in 5G sub-6GHz reduces the dose and health threats to the brain. This provides strong support for the promotion of 5G commutation in China and other regions.

Evaluating automatically generated normal tissue contours for safe use in head and neck and cervical cancer treatment planning.

Volumetric-modulated arc therapy (VMAT) is a widely accepted treatment method for head and neck (HN) and cervical cancers; however, creating contours and plan optimization for VMAT plans is a time-consuming process. Our group has created an automated treatment planning tool, the Radiation Planning Assistant (RPA), that uses deep learning models to generate organs at risk (OARs), planning structures and automates plan optimization. This study quantitatively evaluates the quality of contours generated by the RPA tool. For patients with HN (54) and cervical (39) cancers, we retrospectively generated autoplans using the RPA. Autoplans were generated using deep-learning and RapidPlan models developed in-house. The autoplans were, then, applied to the original, physician-drawn contours, which were used as a ground truth (GT) to compare with the autocontours (RPA). Using a "two one-sided tests" (TOST) procedure, we evaluated whether the autocontour normal tissue dose was equivalent to that of the ground truth by a margin, δ, that we determined based on clinical judgement. We also calculated the number of plans that met established clinically accepted dosimetric criteria. For HN plans, 91.8% and 91.7% of structures met dosimetric criteria for automatic and manual contours, respectively; for cervical plans, 95.6% and 95.7% of structures met dosimetric criteria for automatic and manual contours, respectively. Autocontours were equivalent to the ground truth for 71% and 75% of common DVH metrics for the HN and cervix, respectively. This study shows that dosimetrically equivalent normal tissue contours can be created for HN and cervical cancers using deep learning techniques. In general, differences between the contours did not affect the passing or failing of clinical dose tolerances.

Fate of inhaled electronic nicotine delivery systems (ENDS) puff constituents in the human respiratory tract

Published research on the fate of a puff from electronic nicotine delivery systems (ENDS) in the lungs is limited; more information would better inform human exposure and potential adverse outcomes from ENDS use. An ENDS puff is a mixture of multiple constituents in droplet and vapor form, including propylene glycol, vegetable glycerin, nicotine, water, and flavor chemicals. Understanding the complexity of the puff aids in developing mechanistic models that can account for the physical, physiological, and thermodynamic processes of the puff while traveling and depositing in lung airways. Previously, we developed a mathematical model to predict deposition and uptake of ENDS constituents in the oral cavity. In this study, we formulated the model for lung airways to extend to the entire respiratory tract and made adjustments to mechanisms such as phase change and nicotine protonation to study effects on droplet pH and nicotine evaporation. We conducted model simulations for two representative inhalation profiles relevant to ENDS users: mouth-to-lung and direct-to-lung inhalation. Simulation results showed that vapor uptake during ENDS use was the primary mechanism of the overall tissue dose for higher vapor pressure constituents. Nicotine protonation was unaffected by the ratio of propylene glycol to vegetable glycerin but changes to vanillin molarity impacted droplet pH and free nicotine fraction. The largest uptake and deposition occurred in the deep lung, where constituents more efficiently reach the arterial blood. Predicted total respiratory tract retention of higher vapor pressure constituents such as nicotine, propylene glycol, and benzaldehyde were 94–95%, whereas retention of lower volatility constituents such as vegetable glycerin and vanillin was 82–83%. Results also indicated regional uptake differences for the constituents evaluated in the two inhalation scenarios. Predictions from the ENDS deposition model can be linked to physiologically based pharmacokinetic (PBPK) models to determine the fate of puff constituents such as nicotine in other tissues and organs of the body and provides further basis for evaluating flavor chemicals and puff constituents based on user-specific exposure characteristics as well as internal dose to inform risk assessment of ENDS.

A Comparative Evaluation of Dosal Usefulness in Total Scalp Irradiation according to Treatment Plans and Methods

Objective: The purpose of this study is to choose a treatment plan and equipment to maximize tangential irradiation to protect the normal brain tissues as much as possible during total scalp irradiation. Subjects and Methods: After zoning the total scalp of a phantom and selecting a target area for treatment, the study made a Helical Tomo Therapy (HT) plan, a Helical Tomo Therapy with a Complete Block (HTCB) plan, and a Volumetric Modulated Arc Therapy (VMAT) plan. All of these plans made sure that the volume of a treatment plan with 95% of a prescription dose (40 Gy) would not exceed 95% of the entire volume and that Dmax would not be more than 110% of the prescription dose. The plans compared doses among organs at risk of damage including the brain. Doses in the brain tissues were assessed based on the volumetric criteria for normal tissues in Emami et al. Results: HT, HTCB, and VMAT had a dose of 21.68 Gy, 13.75 Gy, and 20.89 Gy, respectively, in brain tissues at D33%, a dose of 7.06 Gy, 3.21 Gy, and 7.84 Gy, respectively, at D67%, and a dose of 3.14 Gy, 1.75 Gy, and 3.84 Gy, respectively, at D100%. They recorded a Dmean of 16.64 Gy, 11.78 Gy, and 16.64 Gy, respectively. These results show that the overall dose was low in the HTCB plan. When the volume of a low dose was calculated based on 5 Gy, they recorded 87%, 49%, and 96%, respectively, in V5Gy. In addition, the maximum dose in the remaining organ (brain stem, hippocampus, and both lenses) except for the optic pathway was the lowest in HTCB Conclusion: The findings demonstrate that Tomo Therapy with a complete block minimized a dose in organs at risk of damage including the brain and hippocampus on both sides and accordingly reduced the probability of side effects such as radiation-induced brain injuries and a resulting decrease in neurocognitive functions. In addition to total scalp irradiation, if additional studies on ring targets treated in various areas are conducted to establish the benefits of tangential irradiation, it is believed that Tomo Therapy using Complete Block can be used to maximize tangential irradiation in treatment planning.

The Role of Radiation Therapy in the Management of Prostate Cancer and Posttreatment Imaging Appearances

AbstractProstate cancer remains a significant global health concern, necessitating continuous research and innovation in treatment modalities. This review explores the currently employed techniques in radiation dose planning and tumor irradiation in the context of prostate cancer management. In addition, we delve into the nuances of expected posttreatment magnetic resonance imaging (MRI) appearances within the gland or in the prostate bed, postradiation tumor recurrence, and its mimics.Radiation therapy (RT) has evolved as a cornerstone in prostate cancer treatment, offering both curative and palliative solutions. Recent developments have seen the emergence of advanced techniques such as intensity-modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT), allowing for precise targeting of cancer cells while minimizing damage to surrounding healthy tissue.The avoidance of normal tissue dose through more conformal dose distribution as in IMRT or proton therapy, improved imaging modalities as in multiparametric magnetic resonance imaging (mpMRI) and prostate positron emission tomography (PET), interventional separation of critical structures from the prostate target, and many other techniques can greatly reduce the side effects of RT. These advancements enhance treatment efficacy and reduce the risk of side effects, promoting improved patient outcomes.

A Novel Framework for Thermoradiotherapy Treatment Planning

Thermoradiotherapy combines radiation therapy with hyperthermia to increase therapeutic effectiveness. Currently, both modalities are optimized separately and in state-of-the-art research the enhanced therapeutic effect is evaluated using equivalent radiation dose in 2-Gy fractions (EQD2). This study proposes a novel thermoradiotherapy treatment planning framework with voxelwise EQD2 radiation therapy optimizing including thermal radiosensitization and direct thermal cytotoxicity. To demonstrate proof-of-concept of the planning framework, 3 strategies consisting of 20 radiation therapy fractions were planned for 4 prostate cancer cases with substantially different temperature distributions: (1) Conventional radiation therapy plan of 60 Gy combined with 4 hyperthermia sessions (RT60 + HT), (2) standalone uniform dose escalation to 68 Gy without hyperthermia (RT68), and (3) uniform target EQD2 that maximizes the tumor control probability (TCP) accounting for voxelwise thermal effects of 4 hyperthermia sessions without increasing normal tissue doses (RTHT + HT). Assessment included dose, EQD2, TCP, and rectal normal tissue complication probability (NTCP), alongside robustness analyses for TCP and NTCP against parameter uncertainties. The estimated TCP of around 76% for RT60 without hyperthermia was increased to an average of 85.9% (range, 81.3%-90.5%) for RT60 + HT, 92.5% (92.4%-92.5%) for RT68, and 94.4% (91.7%-96.6%) for RTHT + HT. The corresponding averaged rectal NTCPs were 8.7% (7.9%-10.0%), 14.9% (13.8%-17.1%), and 8.4% (7.5%-9.7%), respectively. RT68 and RTHT + HT exhibited slightly enhanced TCP robustness against parameter uncertainties compared with RT60 + HT, and RT68 presented higher and less robust rectal NTCP values compared with the other planning strategies. This study introduces an innovative thermoradiotherapy planning approach, integrating thermal effects into EQD2-based radiation therapy optimization. Results demonstrate an ability to achieve enhanced and uniform target EQD2 and TCP across various temperature distributions without elevating normal tissue EQD2 or NTCP compared with conventional methods. Although promising for improving clinical outcomes, realizable enhancements depend on accurate tumor- and tissue-specific data and precise quantification of hyperthermic effects, which are seamlessly integrable in the planning framework as they emerge.

Influence of Respiratory Motion on Dose Distribution in Gastric Mucosa-associated Lymphoid Tissue Lymphoma Radiotherapy.

The present study investigated the effect of respiratory motion on planned radiotherapy (RT) dose for gastric mucosa-associated lymphoid tissue (MALT) lymphoma using four-dimensional dose (4D-dose) accumulation. 4D-computed tomography (4D-CT) images of 10 patients with gastric MALT lymphomas were divided into 10 respiratory phases. Further, the 3D-dose was calculated using 3D conformal RT (3D-CRT) and volumetric modulated arc therapy (VMAT) plans based on the average intensity projection (AIP) images. Then, both plans were recalculated according to each phase image. Moreover, the dose distributions in each phase were transferred to the AIP images using deformable image registration. The 4D-dose distribution was calculated by summing the doses of each phase, and it was compared with the dosimetric parameters of the 3D-dose distribution. For 3D-CRT, the D95 and D99 of the 4D-dose in the planning target volume (PTV) were significantly lower than those of the 3D-dose, with mean differences of 0.2 (p=0.009) and 0.1 Gy (p=0.021), respectively. There were no significant differences in the other PTV and organ-at-risk dosimetric parameters of 3D-CRT or in any dosimetric parameters of VMAT between the 3D- and 4D-dose distributions. The effect of respiratory motion on the planned 3D-CRT and VMAT dose distributions for gastric MALT lymphoma is minimal and clinically negligible.

A Dosimetric Comparative Study of Carbon-Ion Radiotherapy Versus X-ray Volumetric Modulated Arc Therapy for Stage III Non-Small-Cell Lung Cancer.

Compared to photon beam, carbon-ion radiotherapy (CIRT) has both physical and biological advantages. To examine whether two-dimensional (2D) CIRT is dosimetrically superior to photon beam volume-modulated arc therapy (VMAT) in protecting the normal tissues for stage III non-small-cell lung cancer (NSCLC). A retrospective study was conducted. Thirteen patients with stage III NSCLC treated in our center with curative CIRT and a sham photon beam VMAT treatment planning with the same normal tissue dose constraints were included for analysis. Target dose distributions and the homogeneity index (HI) within the planning target volumes were compared. Both CIRT and VMAT plans have good tumor coverage with no significant differences in D98, D95, and D50 of Planning target volume 1 (PTV1) between the two plans. The HIs between the two plans are similar. The HI of PTV2 is superior in the CIRT plan (CIRT vs. VMAT: 0.08 vs. 0.16, P < 0.05). In general, CIRT results in a lower dose of the organ-at-risk (OAR) than the photon plans. The V5, V10, V20, V30, V40, and Dmean of the contralateral lung in the CIRT plan are significantly lower than that of the photon VMAT. For the ipsilateral lung, the V5 of CIRT is significantly lower. The CIRT also had significantly lower spinal cord Dmax, esophageal Dmean and V50, V10 and V30 of bone, and V50 of the trachea and bronchial tree. Compared with photon VMAT, 2D-CIRT using the passive beam scanning technique significantly reduces the radiation dose to the OARs in curative radiotherapy of stage III NSCLC, suggesting a better protection of the normal tissues.

Optimization of collimator angle combined island blocking with parked gap achieves superior normal tissue sparing in SBRT planning of multiple liver lesions.

To propose an efficient collimator angle optimization method by combining island blocking (IB) and parked gap (PG) problem to reduce the radiotherapy dose for normal tissue. The reduction will be done with single-isocenter multi-lesion volumetric modulated arc therapy (VMAT) for the stereotactic body radiation therapy (SBRT) of liver cancer. A novel collimator angle optimization algorithm was developed based on the two-dimensional projection of targets on a beam's eye view (BEV) plane as a function of gantry and collimator angle. This optimization algorithm minimized the sum of the combined IB and PG (IB & PG) areas from all gantry angles for each arc. For comparison, two SBRT plans were respectively generated for each of the 20 retrospective liver cancer cases with multiple lesions. One plan was optimized using the IB & PG algorithm, and the other plan was optimized with a previously reported optimization algorithm that only considered the IB area. Plans were then evaluated and compared using typical dosimetric metrics. With the comparable target coverage, IB & PG plans had significantly lower D500cc, D700cc, mean dose (Dmean), and V15 of normal liver tissues when compared to IB plans. The median percent reductions were 3.32% to 5.36%. The D1cc, D5cc, and Dmean for duodenum and small intestine in IB & PG plans were significantly reduced in a range from 7.60% up to 16.03%. Similarly, the median integral dose was reduced by 3.73%. Furthermore, the percentage of normal liver Dmean sparing when IB & PG plans compared to IB plans, was found to be positively correlated (ρ=0.669, P=0.001) with the inter-target distance. The proposed IB & PG algorithm has been demonstrated to outperform the IB algorithm in almost all normal tissue sparing, and the magnitude of liver sparing was positively correlated with inter-target distance.

A dosimetric comparison of 3D-CRT, IMRT and IMAT treatment techniques - assessment from radiation protection point of view.

The purpose was to assess the impact of irradiation technique type and beam energy on the mixed radiation field around the medical linear accelerator (linac) in terms of radiation quality and related radiation protection quantities. Seven radiotherapeutic plans with Alderson-Rando anthropomorphic phantom [different techniques: conventional three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and intensity modulated arc therapy (IMAT), different beams: 6 MV or 18 MV, and their arrangements) were prepared for the case of prostate malignancy. Recombination chambers REM-2 and GW2 were positioned on the treatment couch 100 cm from the beam axis at the height of the isocentre. Recombination chambers REM-2 and GW2 were used for recombination index of radiation quality Q4 determination, measurement of total tissue dose Dt and calculation of gamma and neutron components to Dt. Estimation of Dt and Q4 allowed for the ambient dose equivalent H*(10) calculations for each plan. For plans prepared with 6 MV beams, Q4 values within the limits of uncertainty were equal to one, which confirms the correctness of the measurement method. For plans implemented with 18 MV beams, the value of Q4 was in the range of 3.7-5.7. Comparison between treatment techniques indicates that the lowest exposure resulting from out-of-field doses comes from 6 MV IMAT (0.7 mSv), whereas the highest one is from 18 MV IMRT (55.1 mSv). With the recombination chambers technique it was confirmed that the choice of beam energy directly affects the generation of photoneutrons. The treatment plan technique can have a significant impact on the out-of-field dose.

Estimating organ dose with optimized peak dose index in cone-beam CT scans

PurposeOrgan dose evaluation is important for optimizing cone beam computed tomography (CBCT) scan protocols. However, an evaluation method for various CBCT scanners is yet to be established. In this study, we developed scanner-independent conversion coefficients to estimate organ doses using appropriate peak dose (f(0)) indices. MethodsThis study included various scanners (angiography scanners and linear accelerators) and protocols for the head and body (thorax, abdomen, and pelvis) scan regions. f(0) was measured at five conventional positions (center position (f(0)c) and four peripheral positions (f(0)p) at 90° intervals) in the CT dose index (CTDI) phantom. To identify appropriate measurement positions for organ dose estimation, various f(0) indices were considered. Organ doses were measured by using optically stimulated luminescence dosimeters positioned in an anthropomorphic phantom. Thereafter, the conversion coefficients were calculated from each obtained f(0) value and organ or tissue dose using a linear fit for all scanners, and the coefficient of variation (CV) of the conversion coefficients was calculated for each organ or tissue. The f(0) index with the minimum CV value was proposed as the appropriate index. ResultsThe appropriate f(0) index was determined as f(0)c for the body region and a maximum of four f(0)p values for the head region. Using the proposed conversion coefficients based on the appropriate f(0) index, the organ/tissue doses were well estimated with a mean error of 14.2% across all scanners and scan regions. ConclusionsThe proposed scanner-independent coefficients are useful for organ dose evaluation using CBCT scanners.

Evolution of dosimetric treatment planning for pediatric total lymphoid irradiation (TLI): a single-institution experience.

Total lymphoid irradiation (TLI) is a conditioning regimen in allogeneic hematopoietic stem cell transplantation (allo-HSCT) which may reduce long-term toxicities attributed to other techniques, such as total body irradiation (TBI). At our institution, TLI treatments were first planned with the three-dimensional conformal radiation therapy (3D-CRT) technique and later with volumetric modulated arc therapy (VMAT). With the recent availability of a basic helical tomotherapy (HT), the possible dosimetric gain of the latter for TLI is studied. 22 pediatric patients were planned for VMAT and HT, prescribed to 8 Gy in 4 fractions. VMAT was planned with template based on a single cost function, using the Monaco treatment planning system (TPS). HT plans were planned using Accuray Precision TPS for a basic HT without the dynamic jaws feature or VOLO-Ultra algorithm. Plan quality was analyzed based on four quality indices, mean and maximum doses to planning target volume (PTV) and organs at risk (OARs), dose gradient and integral doses. Differences were analyzed with Wilcoxon signed-rank test. HT plans resulted in improved conformity (CI) and homogeneity indices (HI) (p < 0.05) but less steep dose gradient (p = 0.181). VMAT plans created larger areas with high doses within the PTV, while comparable doses to OARs, except mainly for the spinal marrow, for which a reduction of 37.7% in D2% was obtained (p < 0.05). Integral dose for non-tumor tissue was 11.3% lower with the VMAT template (p < 0.05). HT achieves better conformity and homogeneity even without its more advanced features. Nevertheless, the VMAT template achieves dosimetric results close to those of HT, both with similar clinical outcome.

Hybrid VMAT-3DCRT as breast cancer treatment improvement tool

Radiation therapy is an important tool in the treatment of breast cancer and can play a crucial role in improving patient outcomes. For breast cancer, if the technique has been for a long time the use of 3DCRT, clinicians have seen the management evolve greatly in recent years. Field-in-field and IMRT approaches and more recently dynamic arctherapy are increasingly available. All of these approaches are constantly trying to improve tumour coverage and to preserve organs at risk by minimising the doses delivered to them. If arctherapy allows a considerable reduction of high doses received by healthy tissues, no one can deny that it also leads to an increase of low doses in tissues that would not have received any with other techniques. We propose a hybrid approach combining the robustness of the 3DCRT approach and the high technicality and efficiency of arctherapy. Statistical tests (ANOVA, Wilcoxon, determination coefficient, ROC, etc.) allow us to draw conclusions about the possibility of using the hybrid approach in certain cases (right breast, BMI > 23, age > 48, target volume > 350 cc, etc.). Depending on the breast laterality and patients morphological characteristics, hybridization may prove to be a therapeutic tool of choice in the management of breast cancer in radiotherapy.

Identification of avian polyomavirus and its pathogenicity to SPF chickens.

The research aimed to study an Avian polyomavirus strain that was isolated in Shandong, China. To study the pathogenicity of APV in SPF chickens, and provide references for epidemiological research and disease prevention and control of APV. The genetic characterization of APV strain (termed APV-20) was analyzed and the pathogenicity of APV was investigated from two aspects: different age SPF chickens, and different infection doses. The results revealed that the APV-20 exhibits a nucleotide homology of 99% with the other three APV strains, and the evolution of APV In China was slow. In addition, the APV-20 infection in chickens caused depression, drowsiness, clustering, and fluffy feathers, but no deaths occurred in the infected chickens. The main manifestations of necropsy, and Hematoxylin and Eosin staining (HE) showed that one-day-old SPF chickens were the most susceptible, and there was a positive correlation between viral load and infection dose in the same tissue. This study showed that SPF chickens were susceptible to APV, and an experimental animal model was established. This study can provide a reference for the pathogenic mechanism of immune prevention and control of APV.

Feasibility study of multiple-energy Bragg peak proton FLASH on a superconducting gantry with large momentum acceptance.

While the Bragg peak proton beam (BP) is capable of superior target conformity and organs-at-risk sparing than the transmission proton beam (TB), its efficacy in FLASH-RT is hindered by both a slow energy switching process and the beam current. A universal range shifter (URS) can pull back the high-energy proton beam while preserving the beam current. Meanwhile, a superconducting gantry with large momentum acceptance (LMA-SC gantry) enables fast energy switching. This study explores the feasibility of multiple-energy BP FLASH-RT on the LMA-SC gantry. A simultaneous dose and spot map optimization algorithm was developed for BP FLASH-RT treatment planning to improve the dose delivery efficiency. The URS was designed to be 0-27cm thick, with 1cm per step. BP plans using the URS were optimized using single-field optimization (SFO) and multiple-field optimization (MFO) for ten prostate cancer patients and ten lung cancer patients. The plan delivery parameters, dose, and dose rate metrics of BP plans were compared to those of TB plans using the parameters of the LMA-SC gantry. Compared to TB plans, BP plans significantly reduced MUs by 42.7% (P<0.001) with SFO and 33.3% (P<0.001) with MFO for prostate cases. For lung cases, the reduction in MUs was 56.8% (P<0.001) with SFO and 36.4% (P<0.001) with MFO. BP plans also outperformed TB plans by reducing mean normal tissue doses. BP-SFO plans achieved a reduction of 56.7% (P<0.001) for prostate cases and 57.7% (P<0.001) for lung cases, while BP-MFO plans achieved a reduction of 54.2% (P<0.001) for the prostate case and 40.0% (P<0.001) for lung cases. For both TB and BP plans, normal tissues in prostate and lung cases received 100.0% FLASH dose rate coverage(>40Gy/s). By utilizing the URS and the LMA-SC gantry, it is possible to perform multiple-energy BP FLASH-RT, resulting in better normal tissue sparing, as compared to TB plans.

A high-resolution 3D radiochromic hydrogel photonic crystal dosimeter for clinical radiotherapy.

The precise, rapid and direct visualization of 3D topographical dose in the target tissue that is crucial for effective radiation therapy remains a challenge. Herein, by combining hydrogel photonic crystals with film stacking or 3D printing, a 3D radiochromic dosimeter with a dose sensitivity of up to 10 nm Gy-1, a spatial resolution <50 μm, and the ability to detect complex 3D topographical dose distribution was proposed for clinical radiation dose verification. The sensitivity and response range of the dosimeter by radiation-induced polymer cross-linking and consequent Bragg wavelength shift can be tuned via the solid content and extent of acrylate modification. The combination of rapid readout, low dose response, high spatial resolution, and great pre-irradiation and post-irradiation stability highlights the translational potential of this technology for topographical dose mapping in clinical radiotherapy applications.

Оценка радиационных рисков на индивидуальном уровне при многократном прохождении компьютерной томографии на современных компьютерных томографах

Technological developments, as well as software upgrades to existing computerized tomography (CT) scanners, require a continuous review of the methods for estimating radiation risk from CT procedures. According to the International Commission on Radiological Protection (ICRP), such assessments should be based on absorbed doses in organs and tissues exposed to radiation. This work is devoted to the study of the influence of various characteristics of the CT (manufacturer, type of scanner, etc.) on the evaluation of radiation risks on the example of multiple exposures in standard CT procedures. As an example, the value of lifetime attribute risk (LAR) and lifetime attributable risk fraction (LARF) for 5 CT scans during the life of a woman aged 20, 25, 30, 45 and 50 years is estimated. The lifetime attributable risk of possible cancer induction was estimated according to the ICRP mathematical model (Publication 103) and using the medical and demographic characteristics of the Russian population, as well as scan protocol data for typical CT scanners of selected models. The results were obtained with the use of old and updated conversion factors for the DLP (Dose Length Product – a measure of the absorbed radiation dose for the whole CT examination) parameter to organ doses from a particular procedure. The lifetime attributable risk of possible cancer induction calculated using organ doses derived from old conversion factors was compared with the risk calculated with data for modern CT scanners with updated conversion factors. The LAR was evaluated over time for one CT examination, two, three, four and five different procedures during the patient's lifetime. It was found that to date such factor as software updates in the field of optimisation of scanning protocols or the CT scanner manufacturer still do not has a significant impact on the radiation risks associated with specific diagnostic procedures. The methods developed by the authors for calculating absorbed doses and radiation risks can be used in planning CT examinations and optimising patient dose loads on any modern CT scanners.