Conformal Technique Research Articles

Viscoelastic-Support-Layer-Based Macroscopic Conformal Transfer of van der Waals Materials Compatible with Plasmonic Application.

This study showcases the conformal geometries of van der Waals materials with metallic structures utilizing viscoelastic support layers. Mechanically exfoliated nanometer-thick graphite flakes were transferred onto metal structures with various side slopes using two different polymers: polycarbonate (PC) and polyethylene (PE). We proposed a morphology-based evaluation of the macroscale conformity that can contribute to the selection of a proper support layer. Although both support layers ensured high conformity on the sloped side, the PE layer offered superior conformity on the vertical metal structure. To further investigate the impact of conformal structures, we compared the terahertz transmission changes of a metal bowtie antenna before and after transferring graphite onto the bowtie gap for two distinct conformal structures. The conformity of graphite to the metal gap structure significantly influenced the optical response in the terahertz frequency regime. This suggests that the conformal structuring technique can be leveraged in various terahertz devices composed of metals and van der Waals materials, opening avenues for quantitative analysis in light-matter interactions.

Effective Personalization of Stereotactic Radiosurgery for Brain Metastases in the Modern Era: Opportunities for Innovation.

As survival rates improve for patients with metastatic disease, more patients are requiring complex treatment for brain metastases. Stereotactic radiosurgery (SRS) is a conformal radiotherapy technique that allows high ablative dose to be delivered to a specific target and is a standard effective local therapy for the treatment of patients with limited brain metastases. This review highlights the current landscape of SRS treatment in the context of modern therapeutic advances and identifies new research frontiers to personalize SRS and maximize the therapeutic ratio.

Current Radiotherapy Management of Extensive-Stage Small-Cell Lung Cancer in the Immunotherapy Era: An Italian National Survey on Behalf of the Italian Association of Radiotherapy and Clinical Oncology (AIRO).

Extensive-stage small-cell lung cancer (ES-SCLC) treatment has recently been revolutionized by the advent of immune checkpoint inhibitors. This survey was conducted to evaluate the current pattern of care among Italian clinicians, in particular about the integration with radiation therapy (RT). In June 2023, 225 Italian cancer care professionals were invited to complete a 21-question web-based survey about ES-SCLC management through personal contacts and the Italian Association for Radiotherapy and Clinical Oncology (AIRO) network. We received 90 responses; the majority were radiation oncologists (89%) with more than 10 years of experience (51%). The preferred management of ES-SCLC in patients with a good performance status was concomitant chemo-immunotherapy (84%). Almost all respondents recommended prophylactic cranial irradiation (PCI) (85%), taking into account age and thoracic response; PCI was performed mainly between the end of chemotherapy and before starting immunotherapy (37%), with a three-dimensional conformal technique (46%). Furthermore, 83% of respondents choose to deliver thoracic RT in the case of both an intrathoracic and extrathoracic response, with an RT schedule of 30 Gy/10 fractions. Stereotactic RT is increasingly being used in oligoprogressions. Our analysis showed the variability of real-world management of ES-SCLC. Future clinical trials and developments are needed to improve the multidisciplinary treatment of these patients.

Bootstrapping conformal defect operators on a line

We study a conformal field theory with cubic anisotropic symmetry in presence of a line defect. We compute the correlators of the low lying defect operators using Feynman diagrams and derive explicit expressions for the two, three and four point defect correlators at the cubic fixed point in 4 – ϵ dimensions to O(ϵ). We also compute the defect g-function for this setup and demonstrate that this is in agreement with the g-theorem, which states that the g-function is monotonic under the renormalisation group flow along the defect. Next, we focus on conformal bootstrap techniques to determine the CFT data associated with the defect operators, which is the main objective of the paper. We utilize the framework of crossing symmetric Polyakov bootstrap and compute the averaged CFT data to O(ϵ) up to a finite number of ambiguities. We comment on unmixing the CFT data for the double trace operators at O(ϵ) and use this to compute the O(ϵ2) data. Finally, we study these defect correlators non-perturbatively using numerical methods and isolate them near the free theory limit close to four dimensions.

RTOG 0915-compliant patient specific QA for lung stereotactic body radiotherapy using the new PTW 1600SRS detector array

PurposeAn area of focus in radiotherapy is the treatment of oligometastatic lung cancer using highly conformal techniques such as SBRT, performed using VMAT that involves flattening filter free (FFF) beams. This study proposes a new calibration procedure for PTW Octavius 1600SRS detector array and was designed to also evaluate clinical and dosimetric aspects of a patient-specific quality assurance (PSQA) for lung SBRT patients. MethodsThe cohort consists of 20 patients, treated for lung metastases using SBRT with 50 Gy dose in 5 fractions (10 Gy/fr). The proposed calibration method uses only one calibration factor determined at maximum dose rate of 6MV FFF photon beam. The dosimetric accuracy of achieving a high dose gradient was analyzed using the RTOG 0915 protocol and was confirmed by PSQA procedures using the PTW Octavius 1600SRS detector. ResultsConformity index, gradient index, maximum dose at 2 cm and V20 parameters were evaluated with clinical favorable results, with only two plans with lesions situated in the inferior lobe exceeding the deviation allowed for the gradient index. Gamma passing rates using the new calibration method were 98.93% and 99.38% for different gamma criteria of 2 mm/2% and 1 mm/3%, respectively. ConclusionsThe proposed method for calibration using one calibration factor at maximum dose rate for the involved photon beam shows clinically acceptable gamma passing rates. Employing the RTOG 0915 protocol for lung SBRT treatment plan evaluation brings important dosimetric information about treatment plan quality and dose gradient fall-off which can be correlated with the results achieved during the pretreatment verification procedures.

Hypofractionated Radiotherapy for Breast Cancer: Experience of the Radiotherapy Department of the Mali Hospital

Aim: To evaluate the outcomes of hypofractionated radiotherapy in breast cancer. Patients and Methods: It was a retrospective study over a 3-year period, from January 2016 to December 2018, of breast cancer patients treated with hypofractionated radiotherapy at Mali Hospital. All patients with histologically confirmed breast cancer without distant metastases were included. We excluded all patients treated for breast cancer with palliative or normofractionated radiotherapy, patients with metastatic disease on admission and incomplete records. Patients were classified according to the 7th edition TNM classification. Radiotherapy was administered using an Elekta Compact 6MV linear accelerator with the 3D conformal technique, at a total dose of 42 Gy at a rate of 2.8Gy/fraction in 15 sessions, and 5 sessions/week. Data were collected from medical records and treatment sheets, entered into Excel and analysed using SPSS version 23 software. Results: Sixty-four patients out of 129 met our selection criteria (49.61%). The mean age was 44.65+/-11.11 with extremes of 25 and 88 years. Previous hormonal contraception was found in 23.43% of cases, familial breast cancer in 6.25% and nulliparity in 4.68% of cases. Ultramammography was performed in all patients. Assessment of distant extension consisted of a thoraco-abdominal CT scan in 92.18% of cases, and abdominal ultrasound combined with a chest X-ray in 7.82% of cases. Histology of the biopsy specimen showed non-specific carcinoma in 96.87% of cases, Scarf-Bloom and Richardson (SBR) grade II in 64.81% and grade III in 27.78%. Immunohistochemistry was performed in 26 patients, hormone receptor positive in 57.69% (n=15) and triple negative in 42.31% (n=11). Patients were classified as stage T3 or T4 in 82.68% of cases. 95.4% of patients underwent mastectomy and 4.6% lumpectomy; all patients underwent axillary curage. The patients were treated with hypofractionated radiotherapy on the wall and the supra- and sub-clavicular lymph

PDOC-05 MULTIPLE ISOCENTRE VMAT PLANNING FOR PAEDIATRIC CRANIOSPINAL IRRADIATION USING THE HALCYON LINEAR ACCELERATOR

Abstract Paediatric brain tumours constitute the leading cause of cancer specific deaths worldwide. Many patients require craniospinal irradiation (CSI), one of the most technically demanding techniques in radiotherapy. Many LMIC centres have installed Varian Halcyon® linear accelerators and require a technique to execute CSI safely. This study evaluates a multiple isocentre VMAT planning strategy for CSI. The Halcyon is a ring based linac with a single 6MV flattening filter free (FFF) photon beam, a stacked and staggered double MLC for beam shaping and modulation, and no movable collimator jaws. Multiple isocentres are required for treatment fields longer than 28 cm. Paediatric CSI requires dose to be delivered to the entire thecal sac incorporating whole brain as well as entire spinal cord, resulting in long planning target volumes. In addition to the length of the treatment field, CSI treatments are complex due to the change in geometry of the target and the patient body over the length of the treatment field. Traditional 3D conformal radiotherapy techniques (3DCRT) require multiple isocentres with field matching and junction feathering. VMAT offers an alternative, but also require multiple fields to achieve coverage. A Halcyon based three isocentre VMAT technique was investigated and evaluated according to the QUANTEC criteria. Portal dosimetry quality assurance was performed on all fields to ensure they were clinically deliverable. High quality paediatric CSI VMAT treatments can be delivered on the Halcyon, using three isocentres with automatic feathering applied in field overlap regions. Two full arcs and one support arc were used for the brain area, with two posterior partial arcs per spine isocentre, each covering a total of 140 degrees posteriorly to limit integral dose and dose to the lungs and kidneys. Imaging and setup is required for every isocentre further than 8cm/10cm (Halcyon V2/V3 respectively) from the previous isocentre.

Randomized Prospective Trial Comparing 2 Schedules of Hypofractionated Adjuvant Radiotherapy 3 Weeks Against One Week Fractionation Regimen in Females with Breast Cancer

Abstract Purpose Acceleration of radiotherapy in 5 fractions for breast cancer can reduce the burden of treatment especially in Low middle income countries. We report on acute toxicity after whole breast irradiation /chest wall irradiation ± nodal irradiation, QOL score & Local recurrence incidence with ultra- hypofractionation schedule compared to modest hypofractionation protocol. Material and Methods Acute toxicity and health-related quality of life (HRQoL) of 101 patients, randomized between a 15- or 5-fractions schedule, were collected, using the RTOG acute toxicity scoring system, EORTC QLQ-C30 and BR23 questionnaire. The prescribed dose to the breast was either 15∗2.67 Gy (40.05 Gy) or 5∗5.2 Gy (26 Gy),60.1% of patients received tumor boost divided in both arms, with prescribed dose 5∗200cGy with 3D conformal radiotherapy technique. Inclusion criteria were: T1–T3 invasive breast cancer with or without axillary involvement (N0-N1&N2) after breast conserving or modified radical surgery. Results A total of 101 patients included in the study. Median age was 53±10.29 years, most of the cases enrolled were stage II with 38 patients in arm 1 (26 Gy) and 26 in arm 2(40Gy),only 19 cases had stage III breast cancer with 14 cases included in arm 2,while nodal negative status reported in 49 cases. A significant difference was observed for acute skin toxicity after radiotherapy in favor of better tolerability for arm 1 (P value <0.0001),also patients in ultra hypofractionation arm reported significant lower score for symptom scale including breast pain (P value >0.0001),swollen breast (P value <0.0001),difficulty to move arm (P value=0.0001),swollen hand (P value <0.0001)and QOL deterioration was less also in ultra fractionation arm (P value <0.0001) and none of the cases in both arms had local recurrence till time of data collection (12-20 months follow up duration). Conclusion In this single institute study, acute toxicity of accelerated breast radiotherapy in 5 fractions over 5 days seems to compare favorably to hypofractionated breast radiotherapy in 15 fractions. Less radiation dermatitis, breast edema, breast pain, difficulty to move arm and swollen hand. Quality of life is also less disturbed and patients have a better future perspective, however longer time for follow up &larger enrolled numbers needed to confirm non inferiority of this approach.

Radiotherapy for hypopharyngeal carcinoma in Senegal: Experience of the main cancer care facility

Objectives: To describe the epidemiological, diagnostic, therapeutic, and prognostic factors associated with patients treated for hypopharyngeal carcinoma at the Radiotherapy Department of the National Hospital Center Dalal Jamm. Patients and Methods: Data from 50 consecutive patients treated for hypopharyngeal carcinoma between 2018 and 2022 were retrospectively analyzed. All patients received three-dimensional conformal radiotherapy (3DCRT) with or without chemotherapy. Epidemiological and diagnostic data, treatment details, and therapeutic outcomes were collected in an Excel 2016 database created for the study. Statistical analyses were performed using SPSS version 20.0. Overall survival estimates were generated using the Kaplan-Meier method. Statistical significance was considered at p = 0.05. Uni- and multivariate analyses were conducted to identify prognostic factors associated with survival. Results: The average age of the patients was 44 years (± 14.4 years), with a male-to-female ratio of 0.56. Sixteen percent of the patients were active smokers and 4% were alcohol consumers. The mean delay to the first consultation was 6 months, and dysphagia was the primary symptom (92%). The majority of patients (89.8%) were classified as stage IVa, and 10% had metastases at diagnosis. Treatment consisted of curative concurrent chemoradiotherapy (95.92%), preceded by induction chemotherapy in 58% of patients. A radiation dose of 70 Gy was utilized in 75% of cases. The 2-year overall survival rate was 25%. Multivariate analysis indicated that the presence of feeding gastrostomy (p=0.044), use of induction chemotherapy (p=0.012), and radiation dose less than 70 Gy (p=0.020) were associated with poorer survival. Conclusion: Concurrent chemoradiotherapy using 3D conformal techniques improved management, although outcomes remain unsatisfactory. Prospective cohort studies are imperative to identify specific risk factors in our population. Additionally, timely access to appropriate treatment modalities could enhance prognosis.

Radiation-induced Esophagitis in Breast Cancer Patients Treated With Supraclavicular Field Irradiation.

The objective of this research was to assess the frequency and intensity of radiation-induced esophagitis in breast cancer patients treated with supraclavicular radiotherapy field irradiation. This study involved 100 patients with positive lymph nodes receiving radiotherapy to the breast or chest wall along with supraclavicular field irradiation, with toxicity levels assessed weekly. Treatment utilized the 3D conformal technique, and variables, such as mean and maximum dose to the cervical esophagus, mean dose to the entire esophagus, and length of the esophagus within the treated area were recorded. The occurrence of grade 2 or higher esophagitis was 48%, with patients facing the risk of developing such esophagitis at an average dose of 13 Gy. The probability of grade 2 esophagitis occurring at doses exceeding 13 Gy was statistically significantly higher (p<0.001) with an odds ratio of 24.4. Limiting the mean cervical esophagus dose to <13 Gy could help reduce the frequency and severity of grade 2 or higher toxicity.

Assessment of prostate cancer radiotherapy using three-dimensional treatment planning technique.

To assess the available commercial treatment planning system using three-dimensional conformal radiation therapy with respect to treatment for prostate cancer patients. This is a cross-sectional study was conducted from June 2021 to February 2022 at the Baghdad Centre for Radiation Therapy and Nuclear Medicine, Baghdad, Iraq, and comprised patients with prostate cancer who were treated with 6MV or 10MV energy using three-dimensional conformal radiation therapy technique, and irradiated using a linear accelerator. The patents were divided into three treatment phases. The prescribed dose in Phase I was 5000 centigrade, in Phase II it was 1800 centigrade, and in Phase III it was 600 centigrade. The number of beams used was 5 and 7. Data was analysed using SPSS 24. Out of 35 patients, 10 (28.6%) in phase I, 15 (42.8%) in phase II, and 10 (28.6%) in phase III. The PTV dose of 5 and 7 beams 6MV energy at the centre was higher than at 1mm, 2mm, and 3mm p values = (0.351, 0.013*, 0.076, 0.295), respectively. Dose to the rectum comparing 6MV and 10MV for beams 5, and 7. The dose to the rectum on phase one at 6MV and 10MV was similar for 5 beams (p=0.611) and 7 beams (p=0.778). A significant difference was seen for 7 beams (p-value=0.008). Phase three showed significant variations in rectum dose at 6 MV and 10MV for 5 beams (p=0.0004). For bladder, a significant difference observed between the energies for 5 beams on phase one and three (p-value=<0.00001*, 0.002*), while at 7 beams only phase 3 were significant (p-value=0.041*). The three-dimensional conformal radiation therapy plan with 10MV energy and a higher number of beams gave a higher coverage of dose for prostate tumours and was found to be a safe dose for the rectum and bladder.

Multi-segments conformal plan optimization for head and neck cancer.

To evaluate better dose distribution with three-dimensional radiation therapy, and to compare it with multi-segmented treatment planning techniques in patients with head and neck cancer. The prospective study was conducted at the Baghdad Centre for Radiation Therapy and Nuclear Medicine, Baghdad, Iraq, and comprised data of 50 patients with head and neck cancerous tumours from June 2021 to February 2022. There were 35 (70%) females and 15(30%) males. The mean age was 47.31 ± 3.95 years (range 19 - 69 years The patients had undergone computed tomography simulation. The images were exported to Monaco 5.1 for contouring by the radiation oncologist. The data was then imported to XiO planning system. Each plan was repeated twice; once with three-dimensional conformal radiation therapy and the other with field-in-field technique. Data was analysed using SPSS 24. There were 50 patients whose data was analysed. The results showed significant differences between three-dimensional conformal radiation therapy and field-in-field techniques for dose coverage at 90% and 95% volumes (p<0.05). There was a significant difference between the two techniques for 2Gy dose (p<0.05), but the difference was not significant for 5Gy dose (p>0.05). The field-in-field treatment planning technique was found to be more effective than the threedimensional conformal radiation therapy technique.

Radiation Therapy in the Management of Head and Neck Mucosal Melanoma.

Mucosal melanoma of the head and neck (HNMM) is a rare but highly aggressive malignancy, often diagnosed at an advanced stage with poor prognosis. This review discusses current treatment strategies, emphasizing the role of radiotherapy in managing this challenging disease. A comprehensive analysis of 33 studies provides updated information on techniques and outcomes, highlighting the consistent benefit of adjuvant radiation in improving local control. Advances in conformal techniques, such as intensity-modulated radiotherapy (IMRT), have significantly reduced toxicity rates. Preliminary data on proton and carbon ion therapies suggest the potential for further enhancement of the therapeutic ratio, despite limited availability. Although recent studies report 3-year local control rates as high as 90%, overall survival within the same time frame remains well below 50-60%, underscoring the need for continued improvement in systemic therapies to address the persistent issue of distant metastases.

Stereotactic body radiotherapy in ultracentrally located lung tumors

Stereotactic body radiotherapy (SBRT) is a highly conformal radiotherapy technique that delivers high doses of radiation per fraction, typically in 1 &amp;ndash; 5 fractions. It is a standard treatment option for patients with early-stage non-small cell lung cancer that is peripherally located, for those who are medically inoperable, or for patients who do not opt for surgery. Similarly, SBRT is considered an effective treatment option for oligometastatic lung tumors. However, in the case of ultracentrally located lung tumors&amp;mdash;tumors situated close to the central airway and mediastinal region&amp;mdash;there is an increased risk of severe toxicities (grade 4 &amp;ndash; 5) due to the dose tolerances of the surrounding organs at risk. The definition of ultracentrally located lung tumors remains unclear. Some studies define an ultracentral lung tumor as one in which the gross tumor volume directly involves the proximal bronchial tree or trachea, while others define it as the planning target volume (PTV) that includes the trachea or main bronchial system. In addition, some studies consider tumors whose PTV touches or overlaps with the central bronchial tree, esophagus, pulmonary vein, or pulmonary artery as ultracentral. In addition, the optimal SBRT regime and organ-at-risk dose limitations for ultracentral tumors have yet to be clearly established. The aim of this review is to explore and discuss the role of SBRT in the treatment of ultracentrally located lung tumors.

Machine-Learning-Accelerated DFT Conformal Sampling of Catalytic Processes.

Computational modeling of catalytic processes at gas/solid interfaces plays an increasingly important role in chemistry, enabling accelerated materials and process optimization and rational design. However, efficiency, accuracy, thoroughness, and throughput must be enhanced to maximize its practical impact. By combining interpolation of DFT energetics via highly accurate Machine-Learning Potentials with conformal techniques for building the training database, we present here an original approach (that we name Conformal Sampling of Catalytic Processes, CSCP), to accelerate and achieve an accurate and thorough sampling of novel systems by exporting existing information on a worked-out case. We use methanol decomposition (of interest in the field of hydrogen production and storage) as a test catalytic reaction. Starting from worked-out Pt-based systems, we show that after only two iterations of active-learning CSCP is able to provide reaction energy diagrams for a set of 7 diverse systems (Pd, Ni, Au, Ag, Cu, Co, Fe) leading to DFT-accuracy-level predictions. Cases exhibiting a change in adsorption sites and mechanisms are also successfully reproduced as tests of catalytic path modification. The CSCP approach thus offers itself as an operative tool to fully take advantage of accumulated information to achieve high-throughput sampling of catalytic processes.

The risk of second malignancies following prostate cancer radiotherapy in the era of conformal radiotherapy: astatement of the Prostate Cancer Working Group of the German Society of Radiation Oncology (DEGRO).

Asignificant number of prostate cancer patients are long-term survivors after primary definitive therapy, and the occurrence of late side effects, such as second primary cancers, has gained interest. The aim of this editorial is to discuss the most current evidence on second primary cancers based on six retrospective studies published in 2021-2024 using large data repositories not accounting for all possible confounding factors, such as smoking or pre-existing comorbidities. Overall, prostate cancer patients treated with curative radiotherapy have an increased risk (0.7-1%) of the development of second primary cancers compared to patients treated with surgery up to 25years after treatment. However, current evidence suggests that the implementation of intensity modulated radiation therapy is not increasing the risk of second primary cancers compared to conformal 3D-planned radiotherapy. Furthermore, increasing evidence indicates that highly conformal radiotherapy techniques may not increase the probability of second primary cancers compared to radical prostatectomy. Consequently, future studies should consider the radiotherapy technique and other confounding factors to provide amore accurate estimation of the occurrence of second primary cancers.

Escalade de dose en radiothérapie modérément hypofractionnée pour les cancers de la prostate localisés, ESHYPRO : résultats d’une série monocentrique rétrospective évaluant la toxicité et l’efficacité

PurposeProstate cancer is the most frequent cancer among men and radiotherapy hypofractionation regimens have become standard treatments for the localized stages, but the absence of increased risk of acute and late genitourinary or gastrointestinal toxicity of the dose escalation still must be demonstrated. Material and methodsThe study population included all patients with localized prostatic adenocarcinoma treated at the institut Curie from February 2016 to March 2018 by external radiation delivered by a linear accelerator using an image-guided conformal intensity modulation technique at a total dose of 75Gy in 30 fractions of 2.5Gy in the planning target volume that included the prostate and the proximal seminal vesicles, and could be paired with a prophylactic lymph node radiotherapy at 46Gy in 23 fractions with simultaneous integrated boost. ResultsA total of 166 patients were included. Among them, 68.6% were unfavourable intermediate or (very) high risk. The median age and follow-up were 71.4years and 3.96years. One hundred and forty-nine patients received prophylactic lymph node radiotherapy (89.8%). One hundred and thirty-one patients received hormonotherapy (78.9%). Genito-urinary toxicity events of grades 2 or above during radiotherapy, at 6months, 1year and 5years were respectively 36.7%, 8.8%, 3.1% and 4.7%. Two patients had late grade 4 toxicity at 5years (1.6%). Grade 2 gastrointestinal toxicity events during radiotherapy, 6months, 1year and 5years were respectively 15.1%, 1.9%, 14.6% and 9.3%. Of these, eight patients had grade 3 toxicity (6.2%). There was no grade 4 toxicity. Analyses did not reveal any predictive factor for toxicity. The 5-year overall, progression-free, and specific survival rates were respectively 82.4%, 85.7%, and 93.3%. Serum prostate specific antigen concentration and cardiovascular risk factors were found to be predictive factors of deterioration in overall survival (P=0.0028 for both). ConclusionExternal radiotherapy for localized prostatic cancer with our moderately hypofractionated dose escalation regimen is well tolerated. In the absence of increased late toxicity, the analysis of the modes of long-term relapses will be interesting to determine the benefit of this dose escalation on local and distant relapses.

A Four-dimensional Computed Tomography Generated Internal Target Volume Approach to Paediatric High Risk Neuroblastoma to Reduce Organ at Risk and Normal Tissue Irradiation

AimsThe magnitude of upper abdominal organ motion in children may be overestimated by current planning target volumes (PTV). A four-dimensional computed tomography (4DCT) – derived internal target volume (ITV) is frequently used in adult radiotherapy to take respiratory-related organ motion into account. In this study, the dosimetric consequences for target coverage and organs at risk from the use of an ITV approach compared to standard PTV margins in children with high-risk neuroblastoma were investigated. Materials and methods14 patients, median age 4.1 years, range 1.5 – 18.9 years, (9 midline targets, 5 lateralised) each had two dual arc volumetric modulated arc therapy (VMAT) plans (14 ×1.5 Gy) generated. One used an ITV-approach; motion information derived from 4DCT (PTV_itv) with a 5mm ITV to PTV expansion, and the other a PTV margin of 10mm from CTV to PTV (PTV_standard). Differences in absolute PTV volume and organ at risk doses are described. ResultsThe ITV approach resulted in a highly significant reduction in PTV size of 38% (p<0.0001). For midline targets, an ITV approach resulted in a small but statistically significant reduction in combined mean kidney dose of 0.8Gy, p 0.01. Mean heart and lung dose were reduced by an average of 1 Gy with an ITV approach. Non-PTV integral dose from 30.4 Gy L to 27.8 Gy L using an ITV approach. ConclusionAn ITV-approach to respiratory related organ motion management in children can significantly reduce absolute PTV volumes, maintain target coverage and reduce dose delivered to normal tissue in proximity to the target. This is an essential step to maximising the benefits of highly conformal radiotherapy techniques including VMAT for this patient group, and in the future with Proton Therapy.

Obesity prediction: Novel machine learning insights into waist circumference accuracy

AimsThis study aims to enhance the precision of obesity risk assessments by improving the accuracy of waist circumference predictions using machine learning techniques. MethodsWe utilized data from the NHANES and Look AHEAD studies, applying machine learning algorithms augmented with uncertainty quantification. Our approach centered on conformal prediction techniques, which provide a methodological basis for generating prediction intervals that reflect uncertainty levels. This method allows for constructing intervals expected to contain the true waist circumference values with a high degree of probability. ResultsThe application of conformal predictions yielded high coverage rates, achieving 0.955 for men and 0.954 for women in the NHANES dataset. These rates surpassed the expected performance benchmarks and demonstrated robustness when applied to the Look AHEAD dataset, maintaining coverage rates of 0.951 for men and 0.952 for women. Traditional point prediction models did not show such high consistency or reliability. ConclusionsThe findings support the integration of waist circumference into standard clinical practice for obesity-related risk assessments using machine learning approaches.

CEREBRAL RADIONECROSIS IN PATIENTS IRRADIATED FOR CAVUM CANCER: RETROSPECTIVE STUDY OF 15 CASES

Introduction: Cerebral radionecrosis is a rare but a serious complication induced by radiotherapy of the nasopharyngeal cancer. Since nasopharyngeal cancer is common to have skull base infiltration, radiation fields cover inevitably the temporal lobes despite the use of the more advanced intensity-modulated radiotherapy (IMRT). Even though the development of imaging means and the systematic practice of CT and MRI in post-therapeutic monitoring, the diagnosis and treatment of cerebral remain challenging. Materiel and Method:A retrospective study including fifteen cases of cerebral radionecrosis occurring after radiotherapy of cavum cancer, based on data from 382 irradiated for cavum cancer during the period from January 2017 to January 2022 and who were regularly followed in post-therapeutic monitoring. Results: The incidence of cerebral radionecrosis in our patients was 3,9%. The average age of patients was 47.5 years (range 28 - 62 years), with a female predominance (sex ratio: 4M/11F = 0.36). All our patients were followed for locally advanced UCNT of the cavum (73% stage IVA and 27 % stage III). 80% of cases have benefited from conformal radiotherapy technique by intensity modulation (VMAT archtherapy). And all cases have had concomitant chemotherapy. Cerebral radionecrosis occurred after an average delay of 31.6 months (11-77 months) from the end of irradiation. The location of the cerebral radionecrosis lesions was temporal in all our patients. Exploring dosimetric data of our patients, we noted that in 58% of cases the dose constraint at the level of the temporal lobe affected by radionecrosis was not respected. Cerebral radionecrosis was initially discovered on MRI of the cavum, a brain MRI was subsequently requested to show areas of cerebral radionecrosis. Spectroscopy was carried out in 33% of patients. Cerebral radionecrosis was treated with corticosteroid therapy in 53% of cases. After a mean follow-up of 19.8 months (2-63 months) the evolution of cerebral radionecrosis in patients irradiated fornasopharyngeal cancer, was marked by radiological stability without the appearance of clinical symptoms in 53% of cases. Conclusion: Cerebral radionecrosis of radiation-treated cavum patients could be a devastating complication. Furthermore, the differential diagnosis remains challenging and may require the use of advanced imaging modalities. The intricate relationship between dose parameters and radionecrosis incidence requires large-scale longitudinal studies. Despite the fact that there is no definitive treatment for cerebral radionecrosis, bevacizumab has proven to be an encouraging treatment option.