Radiotherapy

compared to a conventional system. This improvement could enable the use of low-dose radiopharmaceuticals and a low acquisition time. In clinical practice, uniformity and noise on the reconstructed image were similar to results obtained with a conventional camera whereas detectability and contrast were better. The average reconstructed resolution using the standard clinical filter was inferior to 9.5 mm. The energy resolution of the D-SPECT system at 140 keV was 5.8% which should prove useful in dual radionuclide studies. Conclusion: Clinical practice in nuclear medicine will be largely changed in the future due to the performances of the CZT detectors.

Response of the autonomic nervous system can be assessed by quantifying the dilation of the pupil of a human placed in darkness. When the intensity of the surrounding light is low, human's pupil dilates to capture a maximum number of photons. This type of dilation is known as dark adaptation. The aim of this study is to test the hypothesis that dark adaptation is slowed proportional to the amount of stress that an individual has experienced. We have developed a new tool for automatic quantification of pupil dilation. Our system uses statistics of the color of the pupil and the iris as well as model-to-image registration and region growing segmentation techniques. Our system has been tested on several images and shows high correlation with hand segmentation.

I-131 is a frequently used isotope for radionuclide therapy. This technique for cancer treatment requires a pretherapeutic dosimetric study. The latter is usually performed (for this radionuclide) by directly imaging the uptake of the therapeutic radionuclide in the body or by replacing it by one of its isotopes, more suitable for imaging. This study proposes to compare the image quality that can be achieved by three iodine isotopes: I-131 and I-123 for Single Photon Emission Computed Tomography (SPECT) imaging, and I-124 for Positron Emission Tomography (PET) imaging. The imaging characteristics of each isotope were investigated by simulated data. Their spectrums, point spread functions and contrast recovery curves were drawn and compared. I-131 was imaged with a HEAP (High Energy All Purpose) collimator while two collimators were compared for I-123: LEHR (Low Energy High Resolution) and ME (Medium Energy). No mechanical collimation was used for I-124. The influence of small high energy peaks (> 0.1%) on the main energy window contamination were evaluated. Furthermore, the effect of a scattering medium was investigated and the TEW (Triple Energy Window) correction was used for spectral-based scatter correction. Results show that I-123 gives best results with a LEHR collimator when the scatter correction is applied. Without correction, the ME collimator reduces the effects of high energy contamination. I-131 offers the worst results. This can be explained by the large amount of septal penetration from the photopeak and by the collimator which gives a low spatial resolution. I-124 gives the best imaging properties due to its electronic collimation (high sensitivity) and a short coincidence time window.

The purpose of this study was to compare quantification and image degrading factors for different iodine isotopes currently used in nuclear medicine: I-123 and I-131 for SPECT imaging and I-124 for PET imaging. The imaging characteristics of each isotope were investigated by simulated data. A planar source composed of a circular background with low activity and several hot spots was used to study the contrast recovery and the noise. The resolution was also determined. Moreover, the effect of an attenuating medium on those characteristics was investigated. Results have shown that the amount of downscatter from high energy peaks into the main energy window, depends on the collimator (SPECT) and increases with the attenuating medium (SPECT and PET). This downscatter decreases the image quality and reduces the accuracy of quantification. However, correction for downscatter significantly improves quantification. I-124 offers the best results, both for contrast recovery and resolution.

compared to a conventional system. This improvement could enable the use of low-dose radiopharmaceuticals and a low acquisition time. In clinical practice, uniformity and noise on the reconstructed image were similar to results obtained with a conventional camera whereas detectability and contrast were better. The average reconstructed resolution using the standard clinical filter was inferior to 9.5 mm. The energy resolution of the D-SPECT system at 140 keV was 5.8% which should prove useful in dual radionuclide studies. Conclusion: Clinical practice in nuclear medicine will be largely changed in the future due to the performances of the CZT detectors.

This study aimed to describe our institutional experience in the use of stereotactic body radiation therapy (SBRT) for the management of adrenal gland metastases from multiple primary cancers. Materials and Methods: We retrospectively reviewed 31 patients who underwent SBRT as treatment for 33 adrenal gland lesions in the academic radiotherapy department of Oscar Lambret cancer center between May 2011 and September 2018. The primary study endpoints were 1-and 2-year local control rates, defined as the absence of progression at the treatment site based on the response evaluation criteria in solid tumors (RECIST). Toxicities were graded in accordance with the Common Terminology Criteria for Adverse Events version 4.03. Results: The average tumor volume was 33.5 cm 3 (standard deviation: 51.7 cm 3), and the prescribed dose ranged from 30 to 55 Gy given in 3-9 fractions. The median biological effective dose was 112.5 Gy (range: 45-115.5 Gy), assuming α/β = 10. Considering progression at distant sites or death as competing events, the 1-and 2-year actuarial local control rates were 96.5% (95% confidence interval: 84.9-99.7) and 92.6% (95% confidence interval: 79.2-98.7), respectively. According to RECIST, a complete response was achieved in 10 (32.3%) lesions, a partial response in 10 (32.3%) lesions, and stability in 8 (25.8%) lesions. Three patients presented with local relapse at 8.8, 14, and 49.4 months. After a median follow-up of 18 months (range: 4.4-66.4), the median overall survival was 33.5 months (95% confidence interval: 17-not reached), while the median progression-free survival was 7.4 months (95% confidence interval: 3.8-14.1). Treatment-related toxicity was grade 1 or 2 in 42.4% of patients, including nausea (27.3%), abdominal pain (18.2%), vomiting (15.2%), and asthenia (9.1%). None of the patients developed acute grade ≥3 or late toxicity. Conclusion: SBRT seems to be a safe and effective treatment for adrenal gland metastases in patients whose primary tumor and metastatic spread are controlled by systemic treatment. With a 2-year local control rate of 92.6%, SBRT may be considered as one of the first-line treatments in oligometastatic patients with adrenal metastases.

The purpose of this study was to compare quantification and image degrading factors for different iodine isotopes currently used in nuclear medicine: I-123 and I-131 for SPECT imaging and I-124 for PET imaging. The imaging characteristics of each isotope were investigated by simulated data. A planar source composed of a circular background with low activity and several hot spots was used to study the contrast recovery and the noise. The resolution was also determined. Moreover, the effect of an attenuating medium on those characteristics was investigated. Results have shown that the amount of downscatter from high energy peaks into the main energy window, depends on the collimator (SPECT) and increases with the attenuating medium (SPECT and PET). This downscatter decreases the image quality and reduces the accuracy of quantification. However, correction for downscatter significantly improves quantification. I-124 offers the best results, both for contrast recovery and resolution. Ke...

This work describes the integration of the M6 Cyberknife in the Moderato Monte Carlo platform, and introduces a machine learning method to accelerate the modelling of a linac. Methods: The MLC-equipped M6 Cyberknife was modelled and integrated in Moderato, our in-house platform offering independent verification of radiotherapy dose distributions. The model was validated by comparing TPS dose distributions with Moderato and by film measurements. Using this model, a machine learning algorithm was trained to find electron beam parameters for other M6 devices, by simulating dose curves with varying spot size and energy. The algorithm was optimized using cross-validation and tested with measurements from other institutions equipped with a M6 Cyberknife. Results: Optimal agreement in the Monte Carlo model was reached for a monoenergetic electron beam of 6.75 MeV with Gaussian spatial distribution of 2.4 mm FWHM. Clinical plan dose distributions from Moderato agreed within 2% with the TPS, and film measurements confirmed the accuracy of the model. Cross-validation of the prediction algorithm produced mean absolute errors of 0.1 MeV and 0.3 mm for beam energy and spot size respectively. Prediction-based simulated dose curves for other centres agreed within 3% with measurements, except for one device where differences up to 6% were detected. Conclusions: The M6 Cyberknife was integrated in Moderato and validated through dose re-calculations and film measurements. The prediction algorithm was successfully applied to obtain electron beam parameters for other M6 devices. This method would prove useful to speed up modelling of new machines in Monte Carlo systems.

Background: Stereotactic body radiotherapy (SBRT) has been reported as a safe and efficient therapy for treating refractory ventricular tachycardia (VT) despite optimal medical treatment and catheter ablation. However, data on the use of SBRT in patients with electrical storm (ES) is lacking. The aim of this study was to assess the clinical outcomes associated with SBRT in the context of ES. Methods: This retrospective study included patients who underwent SBRT in the context of ES from March 2020 to March 2021 in one tertiary center (CHU Lille). The target volume was delineated according to a predefined workflow. The efficacy was assessed with the following end points: sustained VT recurrence, VT reduced with antitachycardia pacing, and implantable cardioverter defibrillator shock. Results: Seventeen patients underwent SBRT to treat refractory VT in the context of ES (mean 67±12.8 age, 59% presenting ischemic heart disease, mean left ventricular ejection fraction: 33.7± 9.7%). Five...

Introduction: Static beam IMRT (IMRT-F) and/or arc IMRT (IMRT-A) are now available in many radiotherapy departments in our regions. The aim of this interregional audit is to perform an independent quality control in each participating centre with a common methodology. Methods: A set of images, structures and dosimetric objectives were sent to all participating centres for two cases: prostate (76 Gy, 38 fractions) and Head and Neck (66 Gy, 56 Gy, 33 fractions). The agreement between e28 Abstracts/Physica Medica 31 (2015) e23-e54

The goal of this study is to show that the PTV concept is inconsistent for prescribing lung treatments when using type B algorithms, which take into account lateral electron transport. It is well known that type A dose calculation algorithms are not capable of calculating dose in lung correctly. Dose calculations should be based on type B algorithms. However, the combination of a type B algorithm with the PTV concept leads to prescription inconsistencies. Methods: A spherical isocentric setup has been simulated, using multiple realistic values for lung density, tumor density and collimator size. Different prescription methods are investigated using Dose-Volume-Histograms (DVH), Dose-Mass-Histograms (DMH), generalized Equivalent Uniform Dose (gEUD) and surrounding isodose percentage. Results: Isodose percentages on the PTV drop down to 50% for small tumors and low lung density. When applying the same PTV prescription to different patients with different lung characteristics, the effective mean dose to the GTV is very different, with factors up to 1.4. The most consistent prescription method seems to be the D DMH 50% (PTV) DMH point, but is also limited to tumors with size over 1 cm. Conclusions: Even when using the different prescription methods, the prescription to the PTV is not consistent for type B-algorithm based dose calculations if clinical studies should produce coherent data. This combination leads to patients' GTV with low lung density possibly receiving very high dose compared to patients with higher lung density. The only solution seems to remove the classical PTV concept for type B dose calculations in lung.

DT was 28.8 cc (6.5 to 14.3 cc) and 46.4 cc for PTV ITV (10.4 to 139 cc), so a 40% volume reduction. The mean treatment time for DT was 25 min, lower than the one for ITV method for which control CBCT are necessary. The patient breathing rates (frequency and amplitude) are often irregular during treatment and different from the reference 4DCT. This doesn't affect the treatment delivery and target tracking. With 4 year a follow-up, the clinical tolerance

The goal of this study is to show that the PTV concept is inconsistent for prescribing lung treatments when using type B algorithms, which take into account lateral electron transport. It is well known that type A dose calculation algorithms are not capable of calculating dose in lung correctly. Dose calculations should be based on type B algorithms. However, the combination of a type B algorithm with the PTV concept leads to prescription inconsistencies. Methods: A spherical isocentric setup has been simulated, using multiple realistic values for lung density, tumor density and collimator size. Different prescription methods are investigated using Dose-Volume-Histograms (DVH), Dose-Mass-Histograms (DMH), generalized Equivalent Uniform Dose (gEUD) and surrounding isodose percentage. Results: Isodose percentages on the PTV drop down to 50% for small tumors and low lung density. When applying the same PTV prescription to different patients with different lung characteristics, the effective mean dose to the GTV is very different, with factors up to 1.4. The most consistent prescription method seems to be the D DMH 50% (PTV) DMH point, but is also limited to tumors with size over 1 cm. Conclusions: Even when using the different prescription methods, the prescription to the PTV is not consistent for type B-algorithm based dose calculations if clinical studies should produce coherent data. This combination leads to patients' GTV with low lung density possibly receiving very high dose compared to patients with higher lung density. The only solution seems to remove the classical PTV concept for type B dose calculations in lung.