Radiotherapy For Tumors Research Articles

Preoperative versus postoperative radiotherapy for localized soft tissue sarcoma treated with curative intent in a French tertiary center “SARCLOC”

BackgroundSoft tissue sarcomas of the extremities (E-STS) are rare and heterogeneous. Treatment combines surgery with preoperative or postoperative radiotherapy (RT) for deep, large, or high-grade tumors. We evaluate the effectiveness and toxicity in E-STS patients treated at our institution from 2015 to 2021.Materials and methodsThis retrospective, single-center study, compared clinical and therapeutic characteristics, toxicities, and surgical complications by radiotherapy type. Local recurrence-free survival (LRFS), overall survival (OS), and recurrence-free survival (RFS) were estimated using the Kaplan–Meier method.ResultsWe included 158 patients; 124 (78%) received preoperative RT. The two groups (preoperative RT vs. postoperative RT) differed significantly in terms of median tumor size (111 vs. 67.5 mm, p < 0.01), perivascular involvement (51% vs. 29%, p = 0.03), and bone contact (32% vs. 12%, p = 0.02), but not in grade (grade 2 or 3: 65% vs. 74%, p = 0.72). Median follow-up was 2.9 vs. 5.1 years. Two-year LRFS was 82% [95%CI: 74–88] for both groups; OS was 87% [95%CI: 80–92] vs. 88% [95%CI: 71–95]; and RFS was 72% [95%CI: 63–79] vs. 70% [95%CI: 52–83]. Postoperative complications were 53% vs. 35%, with wound disruption at 39% vs. 15% and infections at 29% vs. 6%. Grade 2 or higher dermatitis was 16% vs. 29%, and RT discontinuation rates were 4% vs. 12% for the two groups, respectively.ConclusionDespite poorer prognostic factors in the preoperative RT group, LRFS and OS were comparable to those in the postoperative RT group. Postoperative complications were more frequent with preoperative RT, and treatment discontinuation was more common postoperatively.

How to protect the proximal bronchial tree during stereotactic radiotherapy of ultracentral lung tumors: Lessons from MR-guided treatment

How to protect the proximal bronchial tree during stereotactic radiotherapy of ultracentral lung tumors: Lessons from MR-guided treatment

Permanent alopecia after radiotherapy of primary brain tumours: The most influential factors

PurposeAlopecia is a distressing side effect of radiotherapy in patients undergoing treatment for primary brain tumours. This study aimed to investigate the most influential clinical, demographic, and dosimetric factors associated with permanent scalp alopecia in patients with brain tumours treated with intensity-modulated radiations. Patients and methodsEighty patients with brain tumors treated with intensity-modulated radiations were enrolled. Inclusion criteria were having a primary brain tumour and patients with at least 18 months of radiotherapy. Scalp alopecia was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. The scalp location with hair loss was marked and delineated on their follow-up MRI, and the planning dosimetric parameters, including D0.1cm3 (as maximum dose), mean dose, and various volumetric parameters such as V16Gy-43Gy (with about 5Gy interval) were recorded. In addition, receiver operating characteristic (ROC) curve analysis was employed to identify predictive parameters for chronic alopecia. ResultsThe hair loss severity was grade 1 for 70 % of cases, and grade 2 for 30 %. Male gender, history of chemotherapy, and family history of hair loss were significantly associated with increased volume of hair loss follicles. The correlation and ROC analysis revealed that regions receiving doses of 30Gy or higher (i.e., V30Gy) were associated with a higher risk of developing grade 2 alopecia. The resulting areas under the curve of 0.694 were indicators for moderate correlations between the considered dose–volume histogram parameters and patients’ permanent alopecia. Even if these results were not statistically significant, these findings suggest that specific dosimetric parameters, such as V30Gy to V43Gy, maybe the strongest predictors of grade 2 chronic radiation-induced alopecia. The cut-off values were also about 13.5 to 8 cm3 for V30Gy to V43Gy, respectively, which can be played as an indicator of the dose–volume histogram threshold above which permanent alopecia will be expected after brain intensity-modulated radiotherapy. ConclusionThe incidence of permanent alopecia after intensity-modulated radiotherapy is influenced by demographic, dosimetric, and clinical factors such as gender, history of chemotherapy, and family history, and the skull follicle regions receiving doses of 30Gy or higher.

Exploring Neuroprotection against Radiation-Induced Brain Injury: A Review of Key Compounds.

Brain radiation is a crucial tool in neuro-oncology for enhancing local tumor control, but it can lead to mild-to-profound and progressive impairments in cognitive function. Radiation-induced brain injury is a significant adverse effect of radiotherapy for cranioencephalic tumors, primarily caused by indirect cellular damage through the formation of free radicals. This results in late neurotoxicity manifesting as cognitive impairment due to free radical production. The aim of this review is to highlight the role of different substances, such as drugs used in the clinical setting and antioxidants such as ascorbate, in reducing the neurotoxicity associated with radiation-induced brain injury. Currently, there is mainly preclinical and clinical evidence supporting the benefit of these interventions, representing a cost-effective and straightforward neuroprotective strategy.

Tissue Glue-Assisted Plaque Radiotherapy for Choroidal Tumors with Scleral Thinning.

To evaluate tissue glue-assisted plaque placement regarding accuracy, stability, and longer-term outcomes for choroidal tumors with scleral thinning. All patients with tissue glue-assisted plaque radiotherapy at a single ocular oncology center were evaluated for patient demographics, tumor features, surgical details, tumor response, and glue-related complications. There were 13 patients (mean age 72 years) treated with tissue glue-assisted plaque radiotherapy for choroidal melanoma (n=12) or choroidal metastasis (n=1). At presentation, the tumor was mean 4.3 mm to the optic disc and 2.0 mm to the foveola with mean basal diameter of 9.5 mm and thickness of 4.2 mm. In all cases, the tissue glue-assistance was employed due to extreme scleral thinning in the bed of proposed radiation. The plaque size was 15 mm (n=5), 18 mm (n=7), or 20 mm (n=1). At application, there was no immediate glue hypersensitivity, ultrasonography confirmed accuracy of placement, and the glue remained adherent for the entire treatment duration (mean 113 hours) with stable plaque location at removal. At removal, the plaque-glue composite was peeled off the globe without need for glue dissolvent and without scleral disruption. At 12 months mean melanoma thickness (2.7 mm, regression 36%). There were no conjunctival, corneal, or scleral complications. Tissue glue-assisted plaque radiotherapy is safe and effective for treatment of choroidal tumors with thin sclera.

Hall probe calibration in high-precision magnetic field mapping system of superconducting cyclotron

Abstract Introduction Superconducting cyclotron can generate high-energy proton beams and are mainly used for radiation therapy of tumors and cancers. In the superconducting cyclotron SC200, the maximum magnetic induction intensity can typically reach up to 4.6 T, and the magnetic field accuracy is 1e-4. Hall probes are commonly used tools for measuring high-intensity magnetic fields. Objective Through comprehensive consideration, this study selects the SENIS Low-Noise Teslameter 3MH5 and Hall probe C to measure the magnetic field. When the magnetic field exceeds the range of 2 T, the measurement accuracy of the Hall probe is less than 1e-4, and the Hall probe needs to be calibrated to improve its measurement accuracy. Methods The Hall probes are calibrated using Swiss METROLAB PT2025 nuclear magnetic resonance (NMR) Tesla instrument and 1062 probe. Based on the calibration principle, a calibration system platform was built, test data were collected, and calibration curves were obtained. At the same time, the calibration data were analyzed through cross-validation experiments using the cubic polynomial fitting method. Results The results indicate that the test deviation range is from −0.1 g to 0.1 g, and the measurement accuracy can reach 1e-4. Conclusion In summary, the Hall probe can accurately measure the magnetic field distribution of the superconducting cyclotron. It can provide accurate and important data for the calculation and analysis of particle beam dynamics.

RADT-36. FUNCTION-ADAPTED RADIOTHERAPY PLANNING IN THE MANAGEMENT OF HIGH-GRADE GLIOMAS: A COMPARING STUDY FOR DOSE SPARING OF SPEECH-ELOQUENT BRAIN AREAS

Abstract BACKGROUND Radiotherapy (RT) for brain tumors can induce injury of functional white matter tracts. In neurosurgery navigated transcranial magnetic stimulation (nTMS)- and diffusion tensor imaging (DTI)-based fiber tracts (FT) is an established tool to protect functional FT during tumor resection. We investigated it´s applicability in RT planning with the aim of dose reduction of language-associated fiber tracts. METHODS Preoperative, nTMS-generated and DTI-based FT of the functional left hemispheric language network of patients with language-eloquent malignant gliomas (WHO III/IV) were imported into the planning software (ARIA®) according to the DICOM standard and contoured as a risk structure. Brain shift after tumor resection was compensated using elastic fusion (Brainlab®). The treatment plans were optimized or recalculated with the aim of reducing the dose to the fiber tracts outside the planning target volume (PTV). The dosimetric evaluation was performed according to dose volume histogram parameters. RESULTS RT plans of 27 patients were retrospectively evaluated in the study. The mean dose (Dmean) to the fiber tracts was 37.3+/-11.8 Gy, with plan optimization dose was 33.6 +/- 12.2 Gy (-10.9% p&amp;lt;0.01), within the 20 Gy isodose the dose reduction to be achieved was on average - 25.0% (range 0-48.5%). The V54Gy and V20Gy were on average 40.2 +/- 23.7% and 72.3 +/- 21.1% compared to 38.2 +/- 23.5% and 58.1 +/- 23.7% (both p&amp;lt;0.01) with optimization. The Dmean of the PTV did not change (59.8 Gy vs. 59.8 Gy (p=0.5)), nor did the dose homogeneity (HI, (D5-D95)/Dp)(p=0.63)). The dose exposure of the organs at risk was within the specified dose constraints. CONCLUSION This study showed that (nTMS)- and diffusion tensor imaging (DTI)-based fiber tractography could be used in radiotherapy planning to spare language-eloquent brain areas without having to accept dose reductions within the PTV. Whether the concept of tract-based sparing of language function brings clinical benefits to patients needs to be further investigated in prospective studies.

Screening of biomarkers in acute radiation enteritis based on microbiome and clustering methods

BackgroundRadiation enteritis (RE) is a common complication of radiotherapy for abdominal and pelvic tumors, adversely affecting treatment outcomes and patients’ quality of life. Gut microbiome alterations may contribute to RE development, but the underlying pathogenic factors are not fully understood. This study aimed to characterize the intestinal microbial changes associated with RE and severe acute radiation enteritis (SARE) and to identify predictive biomarkers.MethodsWe enrolled 50 cervical cancer patients undergoing radiotherapy and 15 healthy women (controls). Stool samples were collected at the baseline and during weeks 2, 4, and 6 of radiotherapy, and then analyzed using 16 S rDNA sequencing and bioinformatics.ResultsAlthough the Bacteroidetes/Firmicutes (B/F) ratio was higher in patients with RE or SARE, it alone could not predict these conditions. Three enterotypes were identified based on dominant genera: Blautia (enterotype 1), Escherichia-Shigella (enterotype 2), and Faecalibacterium (enterotype 3). A decrease in Blautia and an increase in Escherichia-Shigella and Faecalibacterium were correlated with RE and SARE. Univariate logistic regression revealed that the Faecalibacterium enterotype at the baseline was associated with a 4.4-fold higher risk of developing SARE (odds ratio 5.400; P = 0.017). The Escherichia-Shigella enterotype was also linked to increased SARE incidence.ConclusionThese findings suggest that while single bacterial genera or the B/F ratio are insufficient predictors, enterotype classification may serve as a potential biomarker for predicting SARE in patients undergoing radiotherapy.

P188 Stereotactic MRI-guided adaptive radiotherapy for renal tumors in a solitary kidney

P188 Stereotactic MRI-guided adaptive radiotherapy for renal tumors in a solitary kidney

Brainstem Toxicity Following Proton Beam Radiation Therapy in Pediatric Brain Tumors: A Systematic Review and Meta-Analysis.

Background: Proton beam radiation therapy (PBRT) is an advanced cancer treatment modality that utilizes the distinctive physical properties of protons to precisely deliver radiation to tumor targets while sparing healthy tissue. This cannot be obtained with photon radiation. In this systematic review and meta-analysis, we aimed to comprehensively assess the risk of brainstem toxicity in pediatric brain tumor patients undergoing PBRT. Methods: With adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a predetermined search strategy was used to identify eligible articles from PubMed, Web of Science, Scopus, and Cochrane Library through July 2024. Results: The current study included a total of 11 eligible articles. The pooled prevalence of patients who suffered from brainstem toxicity was 1.8% (95% CI: 1%, 2.6%). The pooled prevalences of patients with Grade 1 to Grade 5 brainstem toxicity were found to be 10.6% (95% CI: 8.8%, 30%), 1.5% (95% CI: 0.6%, 2.5%), 0.7% (95% CI: 0.3%, 1.1%), 0.4% (95% CI: 0.1%, 0.7%), and 0.4% (95% CI: 0.1%, 0.8%), respectively, with an overall pooled prevalence of 0.7% (95% CI: 0.4%, 1%). Conclusions: This study revealed a relatively low incidence of symptomatic brainstem toxicity and its related mortality in the pediatric population undergoing PBRT. However, further research is encouraged to study the broader effects of PBRT and to explore various factors that may influence the risk of brainstem toxicity in patients treated with PBRT.

Biological effectiveness of uniform and nonuniform dose distributions in radiotherapy for tumors with intermediate oxygen levels

Objective. We propose a criterion of biological effectiveness of nonuniform hypoxia-targeted dose distributions in heterogeneous hypoxic tumors based on equivalent uniform aerobic dose (EUAD). We demonstrate the utility of this criterion by applying it to the model problems in radiotherapy for tumors with different levels of oxygen enhancement ratio (OER) and different degrees of dose nonuniformity.Approach. The EUAD is defined as the uniform dose that, under well-oxygenated conditions, produces equal integrated survival of clonogenic cells in radiotherapy for heterogeneous hypoxic tumors with a non-uniform dose distribution. We define the dose nonuniformity effectiveness (DNE) in heterogeneous tumors as the ratio of the EUAD(DN) for a non-uniform distributionDNand the reference EUAD(DU) for the uniform dose distributionDUwith equal integral tumor dose. The DNE concept is illustrated in a radiotherapy model problem for non-small cell lung cancer treated with hypoxia targeted dose escalation. A two-level cell population tumor model was used to consider the hypoxic and oxygenated tumor cells.Results. Theoretical analysis of the DNE shows that the entire region of the OER can be separated in two regions by a threshold OERth: (1) OER > OERthwhere DNE > 1 indicating higher effectiveness of nonuniform dose distributions and (2) OER < OERthwhere DNE < 1 indicating higher effectiveness of uniform dose distributions. Our simulations show that the value of the threshold OERthin radiotherapy with conventional fractionation is significant in the range of about 1.2-1.6 depending on selected radiotherapy parameters. In general, the OERthincreases with reoxygenation rate, relative hypoxic volume and dose escalation factor. The threshold value of OERthis smaller of about 1.1 for hypofractionated radiotherapy.Significance. The analysis of dose distributions using the DNE shows that the uniform dose distributions may improve biological cell killing effect in heterogeneous tumors with intermediate oxygen levels compared to targeted nonuniform dose distribution.

MSOR4 Presentation Time: 5:15 PM: Feasibility of Diffusing Alpha-Emitting Radiotherapy in Orthotopic Glioblastoma Multiforme Murine Tumors and Its Combination with 'Standard-of-Care' Drugs in Mice-Bearing Human Xenografts

MSOR4 Presentation Time: 5:15 PM: Feasibility of Diffusing Alpha-Emitting Radiotherapy in Orthotopic Glioblastoma Multiforme Murine Tumors and Its Combination with 'Standard-of-Care' Drugs in Mice-Bearing Human Xenografts

On the trail of CBCT-guided adaptive rectal boost radiotherapy, does daily delineation require a radiation oncologist?

IntroductionDose-escalation radiotherapy for rectal tumours is increasingly considered as a non-operative approach, with online-adaptive radiotherapy (oART) supporting this approach by correcting inter-fraction tumour position errors. However, using cone-beam computed tomography (CBCT)-guided oART requires daily target volume delineation by different operators, leading to inter-operator delineation variability and potential dosimetric issues. This study aims to compare and quantify the inter-operator and inter-professional delineation variability of the rectal boost volume on CBCT, including volumes by an automatically delineated oART treatment planning system. Materials and methodsA rectal boost volume, defined as the primary tumour extended to the entire adjacent rectal wall, was delineated on 10 CBCTs from 5 patients by 15 operators: 4 expert radiation oncologists (ROs), 4 radiation therapists (RTTs) and 7 non-expert ROs. These contours were compared between the different professional groups. A comparison to the average volume of the group (ROs, RTTs, or non-expert ROs) with the lowest delineation variability was also performed for each individual volume including the volume automatically generated by an oART treatment planning system. ResultsDelineation variability was the highest in the superior (range: 2.3–6.0 mm), and inferior (2.3–12.4 mm) directions, compared to the left (0.2–4.4 mm), right (0.3–2.0 mm), anterior (0.1–2.9 mm), and posterior (0.5–4.0 mm) directions. Non-expert ROs, RTTs, and automatic oART volume showed similar ranges of delineation errors when compared to the expert ROs’ volume, which was chosen as reference volume since this professional group showed the lowest variability. DiscussionExpert ROs showed consistent results. Other professional groups exhibit similar variability, comparable to the automatic oART volume. Therefore, RTTs could safely perform the rectal boost delineation without non-expert ROs supervision in the absence of expert ROs during CBCT-based oART. Moreover, these findings provide quantitative data to compute accurate margins for the rectal boost planning target volume in a CBCT-guided oART workflow.

Anti irradiation nanoparticles shelter immune organ from radio-damage via preventing the IKK/IκB/NF-κB activation

BackgroundNormal tissue and immune organ protection are critical parts of the tumor radiation therapy process. Radiation-induced immune organ damage (RIOD) causes several side reactions by increasing oxidative stress and inflammatory responses, resulting in unsatisfactory curability in tumor radiation therapy. The aim of this study was to develop a novel and efficient anti irradiation nanoparticle and explore its mechanism of protecting splenic tissue from radiation in mice.MethodsNanoparticles of triphenylphosphine cation NIT radicals (NPs-TPP-NIT) were prepared and used to protect the spleens of mice irradiated with X-rays. Splenic tissue histopathology and hematological parameters were investigated to evaluate the protective effect of NPs-TPP-NIT against X-ray radiation. Proteomics was used to identify differentially expressed proteins related to inflammatory factor regulation. In addition, in vitro and in vivo experiments were performed to assess the impact of NPs-TPP-NIT on radiation therapy.ResultsNPs-TPP-NIT increased superoxide dismutase, catalase, and glutathione peroxidase activity and decreased malondialdehyde levels and reactive oxygen species generation in the spleens of mice after exposure to 6.0 Gy X-ray radiation. Moreover, NPs-TPP-NIT inhibited cell apoptosis, blocked the activation of cleaved cysteine aspartic acid–specific protease/proteinase, upregulated the expression of Bcl-2, and downregulated that of Bax. We confirmed that NPs-TPP-NIT prevented the IKK/IκB/NF-κB activation induced by ionizing radiation, thereby alleviating radiation-induced splenic inflammatory damage. In addition, when used during radiotherapy for tumors in mice, NPs-TPP-NIT exhibited no significant toxicity and conferred no significant tumor protective effects.ConclusionsNPs-TPP-NIT prevented activation of IKK/IκB/NF-κB signaling, reduced secretion of pro-inflammatory factors, and promoted production of anti-inflammatory factors in the spleen, which exhibited radiation-induced damage repair capability without diminishing the therapeutic effect of radiation therapy. It suggests that NPs-TPP-NIT serve as a potential radioprotective drug to shelter immune organs from radiation-induced damage.

Unprecedented presentation of pelvic synovial sarcoma: A compelling case report

Synovial sarcoma (SS) is a rare tumor that typically arises in various body regions, with its manifestation in the abdominal-pelvic area being exceptionally uncommon. However, despite its rarity in this location, it often metastasizes to the thorax. Despite its slow growth, it can be misdiagnosed as benign in less than 10% of cases. Diagnosis necessitates identification of the SYT-SSX fusion transcript, alongside immunohistochemical and cytogenetic assessments. Treatment involves surgical resection followed by radiotherapy for localized tumors, while chemotherapy is necessary for metastatic cases. Despite treatment, synovial sarcomas have a high recurrence rate, with about half recurring within two years. We report the case of a 73-year-old patient from sub-Saharan Africa who presented to the emergency room with obstructive symptoms, revealing a mass near the anus compressing the rectum upon imaging, causing an obstructive syndrome. Despite initial tumor resection, histological analysis identified a neurofibromatous origin. Twenty months later, recurrence prompted a hospital visit, revealing thoracic metastases necessitating surgery and chemotherapy. Subsequent analysis confirmed perianal synovial sarcoma. This case underscores the rarity of pelvic-anal synovial sarcoma and emphasizes the importance of early detection and proper management. Synovial sarcoma should figure prominently on the list of differential diagnoses of high-grade pelvic masses due to the importance of adjuvant chemotherapy.

Safety and efficacy of thermo-expandable metallic stent in ureteral stricture following gynecological malignancy surgery and radiotherapy: a single center experience with 33 cases.

The effectiveness of metallic stents in treating ureteral strictures following surgery and radiotherapy for gynecological tumors is currently uncertain. We aimed to investigate the efficacy and safety of thermo-expandable metallic stent (Memokath) in the treatment of ureteral stricture after radiotherapy for gynecological tumors. In this descriptive cross-sectional study, 27 patients with ureteral stricture were treated with Memokath stent after gynecological tumor radiotherapy with or without chemotherapy that was admitted to our hospital from August 2021 to August 2023. Clinical data on efficacy, safety, and complications during stent insertion and indwelling were analyzed. The successful insertion of thirty-three stents in twenty-seven patients studied. The stenosis length was 10.14 ± 6.76cm, and the hospitalization was 4.43 ± 1.83 days. One patient has died from the primary disease carrying a patency stent. The Kaplan-Meier graph showed that the cumilative patency rate of patients with thermo-expandable metallic stent were 92.4% (SD = 5.2%) in eight months, 77.4% (9.1%) in 12 months and 67.7% (SD = 12%) in 29 months, while the cumilative survival rate was 87.5% (SD = 11.5%) in 29 months. The stent patency was 81.48% and later complications of stent indwelling were 5/27, including refractory urinary tract infection (UTI) in three cases, stent migration, and stent intolerance respectively. The creatinine levels, hydronephrosis degree, and glomerular filtration rate improved after the operation, and the first two indicators were statistically significant. Memokath stent is a safe and effective treatment for ureteral stricture after surgery and radiotherapy with or without chemotherapy for gynecological tumors.

Dosimetric comparison of gamma knife and linear accelerator (VMAT and IMRT) plans of SBRT of Lung tumours

This study evaluates dosimetric differences in Stereotactic Body Radiation Therapy (SBRT) for lung tumors using plans of Gamma Knife, and Volumetric Modulated Arc Therapy (VMAT), Intensity-Modulated Radiation Therapy (IMRT) plans based on Linear Accelerator, aiming to inform the reader of appropriate treatment strategy selection. Ten patients with 23 lung tumor lesions treated with SBRT at Zhongshan Hospital of Dalian University were analyzed. Plans of Gamma Knife, and VMAT, IMRT plans based on Linear Accelerator were created for each lesion, totaling 18 plans per type. Lesions were treated with 30–50 Gy in 5–10 fractions. Dosimetric parameters, including gradient index (GI), heterogeneity index (HI), conformity index (CI), and doses to the plan target volumes (PTVs), the gross tumor volumes (GTVs) and organs at risk (OARs) were compared. Plans of Gamma Knife showed superior HI and GI, higher PTV and GTV doses, and reduced doses to the ipsilateral and contralateral lungs, esophagus, spinal cord, and heart compared to VMAT and IMRT plans (p < 0.05). However, Plans of Gamma Knife required longer delivery times. When comparing VMAT and IMRT plans, VMAT plans had shorter delivery times than IMRT plans, but required more monitor units (MUs). Additionally, IMRT plans delivered a lower mean dose to the ipsilateral lung compared to VMAT plans. Gamma Knife SBRT plans achieves steeper dose falloff and minimizes radiation to normal lung tissue compared to VMAT and IMRT plans, but with longer delivery times. VMAT and IMRT plans displayed similar dose distributions for lung SBRT.

Assessment of different shielding materials for radiation therapy of maxillofacial tumors – An in vitro study

Aim: Since the advent of radiotherapy, the success rate of head and neck cancer treatment has increased significantly. However, when the tissue tolerance level is exceeded, unnecessary and uncontrolled exposure to radiation is considered detrimental. Such problems remain difficult to prevent and manage. The aim of the study to evaluate and compare the degree of attenuation of therapeutic radiation using four different radiation shielding materials of varying thickness. Study Setting and Design: In vitro experimental study. Materials and Methods: The samples were divided into four groups based on the different radiation shielding materials of thickness 3mm and 5mm. The materials are Lead (Pb), Silver-tin alloy (Ag-Sn) with Polyvinylsiloxane (PVS), Polymethylmethacrylate (PMMA) with Barium sulphate (BaSO4), and a combination of Ag-Sn with PVS and PMMA with BaSO4 which was exposed to radiation. The radiation dose measurements were recorded and the radiation attenuation properties of the shielding materials were evaluated. Among all of the shielding materials the most efficient material under consideration is determined. Statistical Analysis Used: One-way ANOVA followed by post hoc test was used to compare the means of all four groups. Results: A statistically significant difference between groups was found by a one-way ANOVA with a P = 0.001. In the post hoc test, statistically significant findings were obtained with a P = 0.05 when comparing the variation values of 3mm and 5mm thickness between each group and other groups. Conclusion: The shielding materials results in significant reductions in radiation dosage. It was concluded that the combinations of Ag-Sn alloy with PVS, and PMMA with BaSO4 of thickness 5 mm had a good shielding effect.

Optimizing target and diaphragmatic configuration, and dosimetric benefits using continuous positive airway pressure in stereotactic ablative radiotherapy for lung tumors.

This study aimed to evaluate the impact of facilitating target delineation of continuous positive airway pressure (CPAP) in patients undergoing stereotactic ablative radiation therapy (SABR) for lung tumors by lung expansion and respiratory motion management. We performed a prospective single-institutional trial of patients who were diagnosed with either primary lung cancer or lung metastases and received SABR with a dose of 40 to 60 Gy in 4 fractions. Four-dimensional computed tomography simulations were conducted for each patient: once without CPAP and again with CPAP. Thirty-two patients with 39 tumors were analyzed, after the withdrawal of five patients due to discomfort. For 26 tumors separated from the diaphragm, CPAP significantly increased the superoinferior distance between the tumor and the diaphragm (5.96 cm vs. 8.06 cm; p < 0.001). For 13 tumors located adjacent to the diaphragm, CPAP decreased the overlap of planning target volume (PTV) with the diaphragm significantly (6.32 cm3 vs. 4.09 cm3; p = 0.002). PTV showed a significant reduction with CPAP (25.06 cm3 vs. 22.52 cm3, p = 0.017). In dosimetric analyses, CPAP expanded lung volume by 58.4% with a significant reduction in mean dose and V5 to V40. No more than grade 2 adverse events were reported. This trial demonstrated significant improvement of CPAP in target delineation uncertainties for lung SABR, with dosimetric benefits, a favorable safety profile and tolerability. Further investigation is warranted to explore the role of CPAP as a novel strategy for respiratory motion management.

The correlation of the modulation complexity score (MCS) with the number of segments and local gamma passing rate for the Intensity Modulated Radiation Therapy (IMRT) treatment planning delivery.

To compare the modulation complexity scores across treatment sites, and to examine their connection with monitor unit, segment number and global and local gamma passing percentage. The cross-sectional study was conducted at the Baghdad Centre for Radiation Therapy and Nuclear Medicine, Baghdad Medical City, Baghdad, Iraq, from May 2021 to February 2022. Included were 34 patients, with the age range between 20 - 50 years, subjected to intensity-modulated radiation therapy for head and neck tumours in group A or pelvic tumours in group B. Treatment planning was done using Monaco 5.1, and radiotherapy was done using Synergy linear accelerator. Modulation complexity scores were calculated using MATLAB 2019a. Data was analysed using SPSS 24. Of the 34 patients, 22(64.7%) were in group A; 12(54.5%) males and 10(45.5%) females. There were 12(35.3%) patients in group B; 8(66.7%) females and 4(33.3%) males. The number of segments was greater in group B than group A. A modest positive linear association was seen in group A, demonstrating that an increase in segment numbers resulted in a rise in modulation complexity score (R2=0.0244). Group B tumours had inverse negative linear correlation (R2=0.0189). As the complexity of plans increased in group A, local gamma passing percentage decreased (R2=0.0452). Group B showed a slight negative connection with modulation complexity score (R2=0.0622). The modulation complexity score may be used to provide a simple prediction for pre-treatment verification, and it may also serve as a simple quality assurance tool for intensity-modulated radiation therapy plans.