Search

Background and Purpose: In our institute, breast cancer patients undergoing adjuvant treatment are included in a protocol aimed to reduce cardiovascular morbidity (SAFE-2014, NCT2236806), assessing preclinical heart damage with heart speckle-tracking ultrasound. To develop a dose constraint related to subclinical heart damage, a reliable delineation of heart substructures based on a pre-existing guideline was made.Patients and Methods: Heart substructures of 16 left-sided breast cancer patients included in the SAFE protocol were delineated by five operators. For each substructure, a multi-contour delineation based on a majority vote algorithm (MCD) was created. A consensus-based delineation (CBD) was developed by an independent team of two blinded operators. Dice similarity coefficients (DSC) between volumes delineated by different operators and the MCD were collected and reported, as well as DSC between CBD and MCD.Results: Mean DSCs between heart chambers delineated by each operator and the corresponding MCDs ranged between 0.78 and 0.96. Mean DSC between substructures delineated by all single operators and the corresponding MCD ranged between 0.84 and 0.94. Mean DSC between CBD and the corresponding MCD ranged from 0.89 to 0.97.Conclusion: Results showed low inter-observer variability of heart substructure delineation. This constitutes an external validation of the contouring atlas used, allowing a reliable dosimetric assessment of these volumes within the SAFE-2014 trial. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to test the sensitivity of a transmission detector for online dose monitoring of intensity-modulated radiation therapy (IMRT) for detecting small delivery errors. Furthermore, the correlation of changes in detector output induced by small delivery errors with other metrics commonly employed to quantify the deviations between calculated and delivered dose distributions was investigated.Methods: Transmission detector measurements were performed at three institutions. Seven types of errors were induced in nine clinical step-and-shoot (S&S) IMRT plans by modifying the number of monitor units (MU) and introducing small deviations in leaf positions. Signal reproducibility was investigated for short- and long-term stability. Calculated dose distributions were compared in terms of γ passing rates and dose-volume histogram (DVH) metrics (e.g., Dmean, Dx%, Vx%). The correlation between detector signal variations, γ passing rates, and DVH parameters was investigated.Results: Both short- and long-term reproducibility was within 1%. Dose variations down to 1 MU (∆signal 1.1 ± 0.4%) as well as changes in field size and positions down to 1 mm (∆signal 2.6 ± 1.0%) were detected, thus indicating high error-detection sensitivity. A moderate correlation of detector signal was observed with γ passing rates (R2 = 0.57-0.70), while a good correlation was observed with DVH metrics (R2 = 0.75-0.98).Conclusion: The detector is capable of detecting small delivery errors in MU and leaf positions, and is thus a highly sensitive dose monitoring device for S&S IMRT for clinical practice. The results of this study indicate a good correlation of detector signal with DVH metrics; therefore, clinical action levels can be defined based on the presented data. [ABSTRACT FROM AUTHOR]

Background: Soft tissue sarcomas (STS) are a group of rare, heterogeneous tumors. Scarce terapeuthic options are currently available, given the limited efficacy of systemic chemotherapy. Patients with low-burden metastatic disease may benefit from adjunction of local ablative treatments. However, because of the presumed radioresistance of STS, stereotactic body radiotherapy (SBRT) has not been steadily considered as a viable treatment option. Methods: We retrospectively reviewed STS patients treated with SBRT in a single institution,, for oligometastatic and oligoprogressive metastatic disease. Local control (LC), disease-free survival (DFS), and overall survival (OS) were assessed. We also reported the incidence of early and late adverse events and their grade according to Common Terminology Criteria for Adverse Events (CTCAE) 5.0. Univariate and multivariate statistical analysis were carried out to investigate variables correlated with outcome and toxicity. Results: Forty patients were treated between 2012 and 2019 to 77 metastases with SBRT to a median biologic effective dose (BED5, assuming an α/β=5) of 105 Gy (range 66 to 305 Gy). 63% of patients had received 2 or more chemotherapy lines at the time of SBRT. LC, DFS and OS at two years were 67%, 23% and 40% respectively. At multivariate analysis, LC only significantly improved in patients receving a BED5>150 Gy (hazard ratio [HR] 3.9. 95% confidence interval [CI], 1.6-9.7; p=0.028), while an interval>24 months between primary tumor diagnosis and metastatic disease relapse was correlated with improved DFS and OS (HR, 0.46; 95% CI, 0.22-0.96; P = 0.01 and HR, 0.48; 95% CI, 0.23- 0.99; P = 0.03, respectively). Early toxicity was observed in 4 patients, late toxicity in 1 patient. No toxicity grade>2 was observed. Conclusions: SBRT is an effective therapeutic option in metastatic STS. A BED5>150 Gy5 is required to obtain better tumor control rates. Metastatic relapse>24 months after diagnosis is correlated with improved overall survival. Adverse events are scarce and mostly transient, meaning SBRT is safe and could be an option even in heavily pretreated patients. [ABSTRACT FROM AUTHOR]

Purpose: To present BrainTool, a new anthropomorphic phantom made to assess the accuracy of brain radiosurgery treatments. Materials and method: A synthetic human brain T1/ MRI study was segmented, simplified, and 3D printed. The printed objects were glued to two PMMA disks thus creating four compartments. Each compartment was filled with different substances to create realistic MRI and CT brain contrasts. A water-equivalent silicon rubber casing covers the phantom giving it a realistic head look. Eight markers were attached inside the BrainTool to test the accuracy of image registration procedures. A holder hosting an ionization chamber can be inserted into the BrainTool to assess the targeting accuracy. BrainTool can be placed on any CT, MRI or linac couch or fixed to a Lexell stereotactic frame. To exemplify a possible use of BrainTool, we measured the registration accuracy and the targeting accuracy of a GammaKnife system. Registration accuracy- CT and T1 MRI images of the BrainTool phantom were sent to GammaPlan (Elekta) system and registered with the provided tool. The distances between correspondent markers’ positions in CT and MRI registered studies were evaluated and mean and range values were calculated. Registrations were carried out in the entire image or in a smaller userdefined region of interest (ROI) inside the phantom. Targeting accuracy- It was assessed by comparing planned and measured target positions. The measured target position was obtained using an iterative cross scan approach aimed to localize the camera measuring point. Planned and measured target positions uncertainty were both assessed. Results: In Fig. 1, a picture of the BrainTool phantom, a CT slice with measured HU and axial coronal and sagittal slice of a T1 weighted MR images, are shown. Two NiCl2 solutions (1.2 mmol/l and 0.8 mmol/l) were used to fill the phantom and simulate grey and white matter T1 relaxation times (650 ms and 1200 ms). Several T1 or T2 MRI relaxation times, can be simulated by choosing different solutions or concentrations. Registration accuracy – The mean distances between correspondent markers in CT and MRI registered studies were 1.2± 0.5mm; range [1.0mm -1.4mm] and 0.3 ± 0.2mm; range [0.0mm -0.6mm] for the entire image and the selected ROI, respectively. Targeting accuracy - Targeting mismatches along x, y and z and cumulative (r) were x=-0.7±0.5 mm, y=0.3±0.4 mm z= -0.9± 0.4 mm and r=1.2±0.8 mm, respectively. Conclusions: We have developed a phantom and exemplified its use in brain radiosurgery treatments. [ABSTRACT FROM AUTHOR]