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Purpose: To determine the targeting accuracy of brain radiosurgery when planning procedures employing different MRI and MRI + CT combinations are adopted., Materials and Method: A new phantom, the BrainTool, has been designed and realized to test image co-registration and targeting accuracy in a realistic anatomical situation. The phantom was created with a 3D printer and materials that mimic realistic brain MRI and CT contrast using a model extracted from a synthetic MRI study of a human brain. Eight markers distributed within the BrainTool provide for assessment of the accuracy of image registrations while two cavities that host an ionization chamber are used to perform targeting accuracy measurements with an iterative cross-scan method. Two procedures employing 1.5 T MRI-only or a combination of MRI (taken with 1.5 T or 3 T scanners) and CT to carry out Gamma Knife treatments were investigated. As distortions can impact targeting accuracy, MR images were preliminary evaluated to assess image deformation extent using GammaTool phantom., Results: MR images taken with both scanners showed average and maximum distortion of 0.3 mm and 1 mm respectively. The marker distances in co-registered images resulted below 0.5 mm for both MRI scans. The targeting mismatches obtained were 0.8 mm, 1.0 mm and 1.2 mm for MRI-only and MRI + CT (1,5T and 3 T), respectively., Conclusions: Procedures using a combination of MR and CT images provide targeting accuracies comparable to those of MRI-only procedures. The BrainTool proved to be a suitable tool for carrying out co-registration and targeting accuracy of Gamma Knife brain radiosurgery treatments., (Copyright © 2021 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Purpose: To develop and validate a robust template for VMAT SBRT of lung lesions, using the multicriterial optimization (MCO) of a commercial treatment planning system., Methods: The template was established and refined on 10 lung SBRT patients planned for 55 Gy/5 fr. To improve gradient and conformity a ring structure around the planning target volume (PTV) was set in the list of objectives. Ideal fluence optimization was conducted giving priority to organs at risk (OARs) and using the MCO, which further pushes OARs doses. Segmentation was conducted giving priority to PTV coverage. Two different templates were produced with different degrees of modulation, by setting the Fluence Smoothing parameter to Medium (MFS) and High (HFS). Each template was applied on 20 further patients. Automatic and manual plans were compared in terms of dosimetric parameters, delivery time, and complexity. Statistical significance of differences was evaluated using paired two-sided Wilcoxon signed-rank test., Results: No statistically significant differences in PTV coverage and maximum dose were observed, while an improvement was observed in gradient and conformity. A general improvement in dose to OARs was seen, which resulted to be significant for chest wall V 30 Gy , total lung V 20 Gy , and spinal cord D 0.1 cc . MFS plans are characterized by a higher modulation and longer delivery time than manual plans. HFS plans have a modulation and a delivery time comparable to manual plans, but still present an advantage in terms of gradient., Conclusion: The automation of the planning process for lung SBRT using robust templates and MCO was demonstrated to be feasible and more efficient., (© 2020 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)

Purpose: Radiotherapy treatment of moving lesions is a challenging task in which different strategies can be used to adequately treat the tumor while sparing the surrounding tissue. The complexity of these strategies requires accurate and appropriate quality assurance tests. For this purpose, ADAM (Anthropomorphic Dynamic breAthing Model), a new phantom which simulates realistic patient breathing, was developed aiming to test the image quality and dose delivery in lung cancer treatments., Materials and Methods: ADAM reproduces a male torso complete with a moving anterior chest wall and internal parts. The phantom's external body is printed with a 3D printer using acrylonitrile butadiene styrene. Internal lungs, ribs, spinal cord, and lung tumor (LT) are made of materials that simulate human tissues. Driven by an Arduino programmable board, the lungs can move along linear or elliptical paths while the anterior chest wall moves up and down. Phantom features and usability, reproducibility of LT position in the phantom chest, internal and external motion repeatability and tumor-to-surface motion correlation were investigated., Results: Hounsfield Units of the employed materials demonstrates the phantom adequately simulates human tissues. Tests performed with the Synchrony system confirm ADAM's suitability for respiratory internal tracking. Reproducibility of the internal structure position is within 1mm as are internal and external motion repeatability. A strong positive correlation is found between the lung and chest wall positions (R 2 =0.999)., Conclusions: ADAM demonstrates to be suitable to be employed with gating and tracking devices used in the treatment of moving lesions., (Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Purpose: We present the γTools, a new phantom designed to assess geometric and dosimetric accuracy in Gamma Knife treatments, together with first tests and results of applications., Methods: The phantom is composed of two modules: the imaging module, a regular grid of 1660 control points to evaluate image distortions and image registration result and the dosimetry module for delivered dose distribution measurements. The phantom is accompanied by a MatLab routine for image distortions quantification. Dose measurement are performed with Gafchromic films fixed between two inserts and placed in various positions and orientations inside the dosimetry module thus covering a volume comparable to the full volume of a head., Results: Tests performed to assess the accuracy and precision of the imaging module demonstrated sub-millimetric values. As an example of possible applications, the phantom was employed to measure image distortions of two MRI scanners and to perform dosimetric studies of single shots delivered to homogeneous and heterogeneous materials. Due to the phantom material, the measured absolute dose do not correspond to the planned dose; doses comparisons are thus carried out between normalized dose distributions. Finally, an end-to-end test was carried out in the treatment of a neuroma-like target which resulted in a 100% gamma passing rate (2% local, 2 mm) and a distance between the real target perimeter and the prescription isodose centroids of about 1 mm., Conclusions: The tests demonstrate that the proposed phantom is suitable to assess both the geometrical and relative dosimetric accuracy of Gamma Knife radiosurgery treatments., (Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Purpose: Radiosurgery (RS) is a well-established treatment in selected patients with brain metastasis. The aim of this study is to compare the differences between CyberKnife (CK) and TomoTherapy (HT) treatment plans of RS of single brain metastasis (BM) to define when HT should be used in cases beyond Cyberknife-when both systems are readily available for the radiation oncologist., Methods and Materials: Nineteen patients with single brain metastasis treated with CK were re-planned for radiosurgery using TomoTherapy Hi-ART system. Two planning approaches have been used for TomoTherapy plans: the classical one (HT) and the improved conformity (icHT) that produces dose distributions more similar to those of RS plans. PTV coverage, Conformity Index (CI), Paddick Conformity Index (nCI), Homogeneity Index (HI), Gradient Index (GI), and beam on time of CK, HT, and icHT plans were evaluated and compared., Results: A good coverage was found for CK, HT, and icHT plans. A difference between mean HI of CK and icHT plans was observed (p = 0.007). Better dose gradients compared to both icHT and HT modalities were observed in CK plans. icHT modality showed improved mean CI respect to HT modality, similar to that obtained in CK plans., Conclusions: CK plans show higher conformity and lower GI than icHT and HT plans. TomoTherapy demonstrates the advantage of being a device capable to reach different clinical objectives depending on the different planning modality employed. CyberKnife and TomoTherapy are both optimal RS devices, the choice to use one over another has to be clinically guided.

Linac-based stereotactic radiosurgery (SRS) has been widely used for treating small intracranial lesions. This technique allows conforming the dose distribution to the planning target volume (PTV), providing a steep dose gradient with the surrounding normal tissues. This is realized through dedicated collimation systems. The present study aims to compare SRS plans with two collimating systems: the beam modulator (BM) of the Elekta Synergy linac and the DirexGroup micromultileaf collimator (μMLC). Seventeen patients (25 PTVs) were planned both with BM and μMLC (mounted on an Elekta Precise linac) using the Odyssey (PerMedics) treatment planning system (TPS). Plans were compared in terms of dose-volume histograms (DVH), minimum dose to the PTV, conformity index (CI), and homogeneity index (HI), as defined by the TPS, and doses to relevant organs at risk (OAR). The mean difference between the μMLC and the BM plans in minimum PTV dose was 5.7% ± 4.2% in favor of the μMLC plans. No statistically significant difference was found between the distributions of the CI values for the two planning modalities (p = 0.54), while the difference between the distributions of the HI values was statistically significant (p = 0.018). For both BM and μMLC plans, no differences were observed in CI and HI, depending on lesion size and shape. The PTV homogeneity achieved by BM plans was 15.1% ± 6.8% compared to 10.4% ± 6.6% with μMLC. Higher maximum and mean doses to OAR were observed in the BM plans; however, for both plans, dose constraints were respected. The comparison between the two collimating systems showed no substantial differences in terms of PTV coverage or OAR sparing. The improvements obtained by using μMLC are relatively small, and both systems turned out to be adequate for SRS treatments.

Purpose: This study sought to evaluate acute toxicity and local control in patients who underwent extracranial stereotactic body radiation therapy (SBRT) for paracardiac and cardiac metastatic lesions, defined as such when located at a maximum distance of 1 cm from the heart or inside its parenchyma., Materials and Methods: Between January 2009 and May 2011, 16 patients with paracardiac and cardiac lesions were treated with SBRT. For dose specification, in 15 of 16 patients, the prescription dosage was 36 Gy in three fractions (70% isodose). In one patient, the target lesion was inside the heart, and the prescription dosage was 30 Gy in three fractions (70% isodose)., Results: Regarding response to stereotactic radiotherapy, we recorded one (6%) complete response (CR), six (37%) partial responses (PR), five (32%) stable disease (SD) and four (25%) local failures. Median interval to local failure was 5.2 (range, 3-12) months. The cause of death was distant progression of disease in all four patients. Compliance to treatment was excellent; no patient developed cardiological symptoms or electrocardiographic abnormalities, even months after SBRT., Conclusions: Results of our retrospective study indicate that SBRT represents a safe and effective treatment option for patients with cardiac and paracardiac metastases.