In this paper, we investigate the use of a positron emission tomography (PET) system to monitor the proton therapy. The monitoring procedure is based on the comparison between the <inline-formula> ...<tex-math notation="LaTeX">{ \beta }+ </tex-math></inline-formula> activity generated in the irradiated volume during the treatment, with the <inline-formula> <tex-math notation="LaTeX">{ \beta }+ </tex-math></inline-formula> activity distribution obtained with Monte Carlo (MC) simulation. The dedicated PET system is a dual head detection system; each head is composed of nine scintillating LYSO crystal matrices read out independently with a custom modularized acquisition system. Our experimental data were acquired at the Cyclotron Centre Bronowice, Institute Nuclear Physics in Kraków, Poland, and were simulated with the FLUKA MC code. Homogeneous and heterogeneous plastic phantoms were irradiated with monoenergetic 130 MeV protons. The capabilities of our PET system to distinguish different irradiated materials were investigated, and the proton pencil-beams were used as probes. Our focus was to analyze the activity width and the total activity event number in several cases. Irradiations were performed using either single pencil-beams one at a time, or two pencil-beams during the same data taking. The comparison of 1-D activity profile for experimental data and MC simulation were always in good agreement showing that, the treatment quality assessment in proton therapy can be based on <inline-formula> <tex-math notation="LaTeX">{ \beta }+ </tex-math></inline-formula> activity measurements.
•The Dose Profiler is a charged fragment tracker designed for range monitoring in particle therapy.•The detector design, carefully optimized to operate in clinical environment, is described.•The ...characterization measurements have been performed using different experimental setup.•The obtained performances are suitable for range monitoring application.
Particle therapy (PT) can exploit heavy ions (such as He, C or O) to enhance the treatment efficacy, profiting from the increased Relative Biological Effectiveness and Oxygen Enhancement Ratio of these projectiles with respect to proton beams. To maximise the gain in tumor control probability a precise online monitoring of the dose release is needed, avoiding unnecessary large safety margins surroundings the tumor volume accounting for possible patient mispositioning or morphological changes with respect to the initial CT scan. The Dose Profiler (DP) detector, presented in this manuscript, is a scintillating fibres tracker of charged secondary particles (mainly protons) that will be operating during the treatment, allowing for an online range monitoring. Such monitoring technique is particularly promising in the context of heavy ions PT, in which the precision achievable by other techniques based on secondary photons detection is limited by the environmental background during the beam delivery. Developed and built at the SBAI department of “La Sapienza”, within the INSIDE collaboration and as part of a Centro Fermi flagship project, the DP is a tracker detector specifically designed and planned for clinical applications inside a PT treatment room. The DP operation in clinical like conditions has been tested with the proton and carbon ions beams of Trento proton-therapy center and of the CNAO facility. In this contribution the detector performances are presented, in the context of the carbon ions monitoring clinical trial that is about to start at the CNAO centre.
•MC calculation of dose average LET and RBE evaluation.•Cross Sections for the production of secondary particles in proton therapy.•Calculation of fluence of secondary particles at different depth in ...water for the implementation in a TPS of next generation.
In proton therapy, secondary fragments are created in nuclear interactions of the beam with the target nuclei. The secondary fragments have low kinetic energies and high atomic numbers as compared to primary protons. Fragments have a high LET and deposit all their energy close to the generation point. For their characteristics, secondary fragments can alter the dose distribution and lead to an increase of RBE for the same delivered physical dose. Moreover, the radiobiological impact of target fragmentation is significant mostly in the region before the Bragg peak, where generally healthy tissues are present, and immediately after Bragg peak. Considering the high biological impact of those particles, especially in the case of healthy tissues or organs at risk, the inclusion of target fragmentation processes in the dose calculation of a treatment planning system can be relevant to improve the treatment accuracy and for this reason it is one of the major tasks of the MoVe IT project.
In this study, Monte Carlo simulations were employed to fully characterize the mixed radiation field generated by target fragmentation in proton therapy. The dose averaged LET has been evaluated in case of a Spread Out Bragg Peak (SOBP). Starting from LET distribution, RBE has been evaluated with two different phenomenological models. In order to characterize the mixed radiation field, the production cross section has been evaluated by means of the FLUKA code. The future development of present work is to generate a MC database of fragments fluence to be included in TPS.
The treatment of deep-seated tumours with electrons of very high energies (VHEE, 70–150 MeV) has already been explored in the past, suggesting that a dosimetric coverage comparable with ...state-of-the-art proton (PT) or photon radiotherapy (RT) could be achieved with a large (
>
10) number of fields and high electron energy. The technical and economical challenges posed by the deployment of such beams in treatment centres, together with the expected small therapeutic gain, prevented the development of such technique. This scenario could radically change in the light of recent developments that occurred in the compact, high-gradient, electron acceleration technology and, additionally, of the experimental evidence of the sparing of organs at risk achieved in ultra-high dose rate irradiation, also referred to as FLASH. Electrons with the energy required to treat intracranial lesions could be provided, at dose rates compatible with what is needed to trigger the FLASH effect, by accelerators that are a few metres long, and the organ sparing could be exploited to significantly simplify the irradiation geometry, decreasing the number of fields needed to treat a patient. In this paper, the case of two patients affected by a chordoma and a meningioma, respectively, treated with protons in Trento (IT) is presented. The proton plans have been compared with VHEE plans and X-ray intensity-modulated radiotherapy (IMRT) plans. The VHEE plans were first evaluated in terms of physical dose distribution and then assuming that the FLASH regimen can be achieved. VHEE beams demonstrated their potential in obtaining plans that have comparable tumour coverage and organs at risk sparing when benchmarked against current state-of-the-art IMRT and PT. These results were obtained with a number of explored fields that was in the range between 3 and 7, consistent with what is routinely performed in IMRT and PT conventional irradiations. The FLASH regimen, in all cases, showed its potential in reducing damage to the organs placed nearby the target volume, allowing, particularly in the chordoma case where the irradiation geometry is more challenging, a better tumour coverage with respect to the conventional treatments.
•According to WHO, 50% of medicines purchased from illegal sites are counterfeit.•The COVID-19 pandemic highlights issues that can arise when purchasing medicines online.•Participants rated online ...pharmacies as the safest to purchase medicines.•Past purchase from different online platforms variably predicted purchase of medicine types.
Introduction Some artifacts caused by prosthesis implants or gold seeds for prostate treatment create uncertainties in CT-Scan images (SOMATOM Scope). This will cause several approximations in ...radiation therapy (contouring, dose calculation). To improve the treatment, Siemens Healthineers, developed an iterative metal artifact reduction algorithm: iMAR. The aim of this study is to compare HU values reconstructed by the CT-Scan with and without iMAR for prostate treatment. And finally, evaluating dosimetrics effects by calculation of dose on iMAR corrected images. Methods The study is based on three steps. Firstly, on 30 patients with and without prosthesis/gold seeds to evaluate the average of HU into and outside prostate, before and after iMAR correction. Secondly, created customized phantom (QuasarTM ) with known material inserts (CIRS Model 062) to simulate human pelvic linked with previous results. We have done CT-Scan acquisitions of the phantom to evaluate accuracy in retrieving correct HU values and Standard Deviation (SD). The reference acquisition is made with QuasarTM acrylic insert, and an acquisition with double metals prosthesis inserts (with/without iMAR reconstruction) is performed. Same ROI (4 cm2 ) are calculated in this three reconstructions CT images to compare HU values and SD. Thirdly, 23MV VMAT treatment plan in the TPS Eclipse® is performed for both reconstruction (iMAR and no iMAR) to evaluate the dose distribution and to be able to do a dose measurement on the Clinac to determine if iMAR reconstruction is more accurate in dose calculation. Results On patients CT images, iMAR allows to regain information lost by metals artefacts. Moreover, the phantom study demonstrating that lost information (up to −100 HU and ± 100 SD) are improved with iMAR correction (up to + 10 HU and ± 15 SD) and outside the streaking artifact, HU and SD are constant. From a dosimetry point of view, the TPS variation in dose calculation may increase up to + 3.32 Gy in one pixel and the dose covering is improved by iMAR for muscle insert (dose constraint is applied). Therefore, iMAR has an impact in the dose calculation. Finally, the dose verification between treatment in Linac and calculation in TPS (in two measured points) shows that calculation in TPS is more accurate with iMAR ( ≠ 3% out of dose constraint and ≠ 0.2% in dose constraint) compared without iMAR ( ≠ 8.1% out of dose constraint and ≠ 1% in dose constraint). Conclusions iMAR algorithm increases confidence in contouring due to a visualisation of organ’s outlines with a very close reproduction of the HU values and SD. This, enables a stability of the information in TPS for dose calculation. Therefore, dose calculation is improved for the dose covering and dose calculation in TPS is closer to reality.
Introduction The treatment of extra-cranial lesions in stereotactic condition request a high precision on the target movement. Errors Positioning and deformation structures appear during ...unsynchronized CT acquisitions (FreeBreathing or blocked). The use of synchronized breathingfree 4D-CT allow to overcome Systematic errors. This study intended to evaluate reconstruction performance of the scanner Siemens Somatom Scope in 4D mode with virtual breathing cycles (BC). Methods The assembly developed for this study includes the motorized piloting phantoms Quasar® and Catphan®. The mobile test object is a sphere 30 mm diameter in a pulmonary density insert. The image quality is explored using Catphan® moving. The Maximum Amplitude (MA) is 70 mm in the 3 reconstruction plans. Acquisition parameters are fixed: total collimation of 16x1.2 mm, voltage 130 kV, 320 mAs reference with modulated intensity (CARE Dose 4D ®), 0.1 pitch with rotation time of 0.6 s. BC (regular or very unstable) were modelled via the software Quasar Respiratory Motion. Retrospective mode 4D-CT of Siemens Scope divides the BC into 8 phases. Phases are reconstructed in 1.5 mm reconstructed slice thickness with the RPF and the noise reduction option (SAFIRE®) method. Other sequences of Average reconstruction and max/MinIP are obtained with 2 and 3 SAFIRE® levels. Varian Eclipse 11.0 TPS is used for the segmentation of mobile objects in each phase. Analyses focus on fidelity of area, diameter and expected positions reconstruction of the sphere for each phase. Stability of Hounsfield units (HU) and the modifications of contrasts are carried out on the various sections of the Catphan® phantom. Results Sequences of regular breathing cycles showed that when amplitude increases or period decreases, reconstructed volume (RV) relative errors are increasing up to 29% for the maximum. Irregular respiratory increase the RV errors in phases, average and MIP reconstructions. These errors are corrected by excluding manually irregular zones from the cycle before reconstruction. Total MA in MIP and Average reconstructions have less than 0.1 slice thickness difference (all sequences combined) from expected that represented less than 0.2 mm. HU standard deviations in phases doesn’t change significantly due to the automatic management of the signal intensity into 4D-CT. HU values changes when period and amplitude increases (-977 to −407). SNR and CNR are decreasing when period and amplitude increases. When amplitude and period go higher than 3.5 cm and 5.5 s, CNR is less than reference (no motion), for SNR limits are 3 s and 3 cm. Conclusions Images reconstruction according to the breathing cycle allows to increase the precision on the positioning of mobile lesions. Major errors of respiratory instabilities can be corrected while excluding the irregularity zone from the cycle. It is necessary to have a maximum regular periods to have accuracy retrospective reconstruction of the movement. The lesion follow-up on 8 phases will allow the delineation of an ITV. Average and max/MinIP sequences will be exploited for the delineation and the dose calculations. The installation of an End to End quality control for each treatment plan will be carried out.
Purpose: Intraoperative electron radiotherapy (IOeRT) is considered the first clinical translation of FLASH with electrons. A crucial aspect is represented by the precise dose monitoring and ...measurement; to this aim, we propose a method fully based on Monte Carlo (MC) simulation that uses as input the beam current measurement and the beam optics simulation. To validate this approach, we chose the NOVAC11 (produced by Sordina IORT Technologies SpA) accelerator, which provides a well-studied model. Methods: We used FLUKA and FRED MC software to simulate in detail the geometry of the NOVAC11 and the coupled applicator usually adopted in clinical practice to deliver the dose in the surgical bed. The simulation results of the longitudinal and off-axis profiles and dose per pulse obtained in a water phantom with different applicators are compared to the experimental data. Results: A very good agreement not only for the relative dosimetry in both the longitudinal and off-axis profiles, with a gamma index pass rate of 100% with 3%/3 mm acceptance criteria, but also for the absolute dosimetry was obtained. Conclusion: The results completely validate the MC description of the system and provide a reliable evaluation of the dose per pulse and output factor with an accuracy of the order of few % for different sets of applicator diameters and lengths.
Hadrontherapy is an emerging technique in cancer therapy that uses beams of charged particles. To meet the improved capability of hadrontherapy in matching the dose release with the cancer position, ...new dose-monitoring techniques need to be developed and introduced into clinical use. The measurement of the fluxes of the secondary particles produced by the hadron beam is of fundamental importance in the design of any dose-monitoring device and is eagerly needed to tune Monte Carlo simulations. We report the measurements carried out with charged secondary particles produced from the interaction of a 80 MeV/u fully stripped carbon ion beam at the INFN Laboratori Nazionali del Sud, Catania, with a poly-methyl methacrylate target. Charged secondary particles, produced at 90° with respect to the beam axis, have been tracked with a drift chamber, while their energy and time of flight have been measured by means of a LYSO scintillator. Secondary protons have been identified exploiting the energy and time-of-flight information, and their emission region has been reconstructed backtracking from the drift chamber to the target. Moreover, a position scan of the target indicates that the reconstructed emission region follows the movement of the expected Bragg peak position. Exploiting the reconstruction of the emission region, an accuracy on the Bragg peak determination in the submillimeter range has been obtained. The measured differential production rate for protons produced with E(Prod)(kin) > 83 MeV and emitted at 90° with respect to the beam line is dN(P)/(dN(C)dΩ) (E(Prod)(kin) > 83 MeV, θ = 90°) = (2.69 ± 0.08(stat) ± 0.12(sys)) × 10⁻⁴ sr⁻¹.
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