Purpose: To present the results of the first multi-centre real-world validation of autoplanning for whole breast irradiation after breast-sparing surgery, encompassing high complexity cases (e.g. with a boost or regional lymph nodes) and a wide range of clinical practices. Methods: The 24 participating centers each included 10 IMRT/VMAT/Tomotherapy patients, previously treated with a manually generated plan ('manplan'). There were no restrictions regarding case complexity, planning aims, plan evaluation parameters and criteria, fractionation, treatment planning system or treatment machine/ technique. In addition to dosimetric comparisons of autoplans with manplans, blinded plan scoring/ranking was conducted by a clinician from the treating center. Autoplanning was performed using a single configuration for all patients in all centres. Deliverability was verified through measurements at delivery units. Results: Target dosimetry showed comparability, while reductions in OAR dose parameters were 21.4 % for D mean , 16.7 % for ipsilateral lung D mean , and 101.9 %, 45.5 %, and 35.7 % for contralateral breast D 0.03cc and D mean , respectively (all p < 0.001). Among the 240 patients included, the clinicians preferred the autoplan for 119 patients, with manplans preferred for 96 cases (p = 0.01). Per centre there were on average 5.0 (1SD) patients with a preferred autoplan (range [0-10]), compared to 4.0 +/- 2.7 with a preferred manplan ([0,9]). No differences were observed regarding deliverability. Conclusion: The automation significantly reduced the hands-on planning workload compared to manual ning, while also achieving an overall superiority. However, fine-tuning of the autoplanning configuration clinical implementation may be necessary in some centres to enhance clinicians' satisfaction with the generated autoplans.

Radiotherapy treatments involving LINACs operating at accelerating potentials >10 MV generate (photo)neutrons which deliver dose to patients also outside the target volume. This effect is particularly relevant for patients with cardiac implantable electronic devices (CIEDs), which can be damaged by the therapeutic irradiation. In the last few years, there has been a rising interest in this issue, and it seems that damage to CIEDs is primarily associated with the thermal component of the photoneutron field. In particular, a recent study led by Politecnico di Milano considered CIEDs from various manufacturers and showed that some of these devices can be damaged after an irradiation with a thermal neutron fluence of about 10^9 cm^-2 . The present work results from a collaboration among Politecnico di Milano, the University of Pisa, the University of Trieste and three Italian hospitals located in Lucca, Trieste and Varese, respectively, and it is primarily aimed at evaluating the thermal neutron fluence in CIED region for some high-energy treatments delivered at 15 and 18 MV and to determine whether it is comparable to the critical value given above, which has been experimentally determined to be potentially harmful for CIEDs. Thermal neutron fluence was measured through CR-39 detectors and TLDs, which were housed inside a BOMAB-like phantom mimicking the patient’s trunk. The experimental sessions involved two models of LINAC, Varian Clinac DHX (Varese hospital) and Elekta Synergy (Lucca and Trieste hospitals). The experimental results show that the treatments considered in this study can lead to a thermal neutron fluence in the cardiac region comparable to the critical value. Furthermore, detailed Monte Carlo geometries for the facilities involved in this project were developed with the MCNP code (v. 6.2), and they were tested by comparing simulation results to measurements considering some benchmark irradiation plans. Bubble detectors were also employed for fast neutron fluence measurements to be compared to simulation outputs. These computational models stand out as promising tools for the investigations required in this work, and they can be used for further studies also extending their use to analogous facilities hosting the same models of LINACs.

Purpose or ObjectiveAs a useful 3D quality assurance (QA) tool, ArcCHECK has gained wide application in helical tomotherapy (HT), but most of the studies were based on old models.This study is to report our experience in ArcCHECK based QA for HT with TomoEdge technique including the establishment of the action level. Material and MethodsA total number of 303 clinical plans in different treatment regions in our hospital were retrospectively studied.The tomotherapy plan verification was conducted using the ArcCHECK diode array with an acrylic insert for placing an A1SL ionization chamber.DQA plans were created by situating the target at the center of ArcCHECK for point dose measurement and meanwhile, making sure the electronic part of the device was not under the main beam.Gamma analysis method was then used to quantitatively compare the dose measured by ArcCHECK and that calculated from the treatment planning system (TPS).The criteria of 3mm distance to agreement (DTA), 3% dose difference, 10% threshold and absolute dose comparison were chosen.According to AAPM TG 119, the recommended action level of gamma passing rate was calculated as AL=Gm-1.96σ,where Gm was the mean of the gamma passing rate and σ was the standard deviation (SD). ResultsDetails of our data are shown in table 1.A value pitch of 0.287 was used for almost all cases except for some brain treatments with values of 0.143 and 0.215.Jaw width of 2.5cm and 5cm with dynamic technique took up 95.7% of total cases and only fixed setting was used for 1cm jaw width.Good point dose agreements between measurements and TPS data were obtained with a mean deviation of 0.75%.Absolute gamma comparison gave an averaged passing rate of 96.6% with the SD of 4.7%, which resulted in an action level of 87.4%.Cases with lower gamma passing rate appeared to be in thorax and abdomen regions, which were suspected to be related to high MF and off-axis induced diode over-response.Our limited data showed that the gamma passing rate could be larger than 92% after a new DQA plan was created by locating the ArcCHECK close to the isocenter.

Purpose The Flattening Filter Free (FFF) modality of the LINAC generates an unflattened X-ray beam with a dose rate up to 5 times (1200 MU/min) the maximum dose rate of a standard flattened beam. Aim of this study is to take advantage of high dose rate to spare treatment time for left breast breath-holding patients and to deliver an equal or better treatment in dose distribution. Here a 6 MV three-fields FFF-IMRT technique is proposed and compared to the standard two tangential 3D-CR conformal radiotherapy (3D-CR). Methods Our 6 MV three-fields IMRT technique adds a slightly tilted beam to the usual two tangential beams. The low modulation allows the maximum dose rate. For a group of 22 patients undergoing left breast treatment with ABC, a comparison was made between 3D-CR standard treatments and FFF-IMRT. 3D-CR plans were calculated by CMS XIO® (v.5.11 convolution superposition algorithm) and Monaco® (v.5.11.02 collapsed cone algorithm), FFF-IMRT plans by Monaco® (v.5.11.02 Monte Carlo algorithm). For plan comparison, 14 indicators were examined by a paired Student T-test to assess statistical significance of differences (p < 0.05). Assessed indicators are listed below: •Left lung: V 20 Gy , V 10 Gy •Heart: Mean Dose, V 25 Gy •Right breast: V 2 Gy •Patient: Maximum Dose ( D 1 % ) •PTV: V 95 % , Maximum Dose ( D 1 % ) , V 105 % (cm3), V 105 % (%), Conformity Index (as defined in Monaco® v.5.11.02) •CTV: V 98 % •Apnoeas number •Treatment time Overall treatment times were evaluated for 3D-CR and FFF-IMRT plans by simulating a patient with a 25 s breath hold phase and a breath recover phase of 30 s. Times for patient set-up, portal imaging and treatment room leaving were also taken into account (total 600 s). Results Significant differences were found for the indicators listed in Table 1. FFF-IMRT plans showed better CTV coverage, high doses (hot spots) control and conformity. All the FFF-IMRT plans were faster and achieved a mean time gain of 15.1% (2%–18%) for 50 Gy, 2 Gy/fraction prescriptions and 14.9% (4%–18%) for 42.40 Gy, 2.65 Gy/fraction prescriptions, and a mean reduction of apnoeas number by two. Conclusions The FFF-IMRT technique delivers an equal or better dose distribution with a significant reduction of treatment time and number of apnoeas, substantially improving patient comfort. The Flattening Filter Free (FFF) modality of the LINAC generates an unflattened X-ray beam with a dose rate up to 5 times (1200 MU/min) the maximum dose rate of a standard flattened beam. Aim of this study is to take advantage of high dose rate to spare treatment time for left breast breath-holding patients and to deliver an equal or better treatment in dose distribution. Here a 6 MV three-fields FFF-IMRT technique is proposed and compared to the standard two tangential 3D-CR conformal radiotherapy (3D-CR). Our 6 MV three-fields IMRT technique adds a slightly tilted beam to the usual two tangential beams. The low modulation allows the maximum dose rate. For a group of 22 patients undergoing left breast treatment with ABC, a comparison was made between 3D-CR standard treatments and FFF-IMRT. 3D-CR plans were calculated by CMS XIO® (v.5.11 convolution superposition algorithm) and Monaco® (v.5.11.02 collapsed cone algorithm), FFF-IMRT plans by Monaco® (v.5.11.02 Monte Carlo algorithm). For plan comparison, 14 indicators were examined by a paired Student T-test to assess statistical significance of differences (p < 0.05). Assessed indicators are listed below: •Left lung: V 20 Gy , V 10 Gy •Heart: Mean Dose, V 25 Gy •Right breast: V 2 Gy •Patient: Maximum Dose ( D 1 % ) •PTV: V 95 % , Maximum Dose ( D 1 % ) , V 105 % (cm3), V 105 % (%), Conformity Index (as defined in Monaco® v.5.11.02) •CTV: V 98 % •Apnoeas number •Treatment time Overall treatment times were evaluated for 3D-CR and FFF-IMRT plans by simulating a patient with a 25 s breath hold phase and a breath recover phase of 30 s. Times for patient set-up, portal imaging and treatment room leaving were also taken into account (total 600 s). Significant differences were found for the indicators listed in Table 1. FFF-IMRT plans showed better CTV coverage, high doses (hot spots) control and conformity. All the FFF-IMRT plans were faster and achieved a mean time gain of 15.1% (2%–18%) for 50 Gy, 2 Gy/fraction prescriptions and 14.9% (4%–18%) for 42.40 Gy, 2.65 Gy/fraction prescriptions, and a mean reduction of apnoeas number by two. The FFF-IMRT technique delivers an equal or better dose distribution with a significant reduction of treatment time and number of apnoeas, substantially improving patient comfort.

Introduction: This study explores an optimization tool of Monaco 5.0 TPS with the aim of sparing delivering time of the SBRT treatments of lung cancer in order to meet the clinical request.

Introduction: The relative effectiveness of periodic machine QA or patient pre-treatment dosimetry for IMRT is debated (Siochi et al., Med. Phys. 40(7), 2013). VMAT machine QA, in particular, are difficult and time consuming. The goal of our study is to assess the feasibility of linac tests that take into account the peculiarity of VMAT treatments (gantry rotation with variable speed and dose rate erogation, MLC moving leaves) using an ion chamber array in a rotational phantom and an in-house developed software.

65 Table. ROC analysis AUC 95% CI Sensitivity Specificity

We recently demonstrated in a clinical trial the ability of a new protocol, IQ SPECT, to acquire myocardial perfusion imaging (MPI) studies in a quarter of the time (12 s/view) of the standard protocol, with preserved diagnostic accuracy. We now aim to establish the lower limit of radioactivity that can be administered to patients and the minimum acquisition time in SPECT MPI using an IQ SPECT protocol, while preserving diagnostic accuracy. Methods: An anthropomorphic cardiac phantom was used to acquire clinical rest scans with a simulated in vivo distribution of Tc-99m-tetrofosmin at full dose (740 MBq) and at doses equal to 50%, 25%, and 18%. For each dose, 2 sets of images were acquired, with and without a transmural defect (TD). Variable acquisition times were also used for each dose. We analyzed raw data and reconstructed images, including no correction and correction for attenuation (AC), for scatter (SC), or for both (ACSC). Images were evaluated qualitatively and quantitatively in order to assess left ventricle (LV) wall thickness (full width at half maximum of the medial sections), TD, and cavity contrast in the LV wall. Data were compared across different acquisition times within the same dose and across doses with the same acquisition time. Results: Images were visually scored as very-good quality except those acquired with 4 s/view or less at 100% dose and 6 s/view or less with 50%, 25%, or 18% dose, due to false-positive defects. LV wall thickness was not significantly different among all acquisitions. Cavity contrast remained unchanged within the same dose for all images and tended to be higher in AC and ACSC images. TD contrast remained unchanged within the same dose for all images. In SC and no-correction images, contrast was constant for all doses. AC images had significantly higher TD contrast values, and ACSC images showed a drop in TD contrast for a 50% dose. Conclusion: IQ SPECT effectively preserved both image quality and quantitative measurements with reduced acquisition time or administered dose in a phantom study. These findings suggest that approximately one eighth of the time, compared with standard protocols with a full dose, or a lower dose at an acquisition time of 12 s/view can be applied in MPI without the loss of diagnostic accuracy.