C. Peroni

PERFORMANCES OF A VLSI WIDE DYNAMIC RANGE CURRENT-TO-FREQUENCY CONVERTER FOR STRIP IONIZATION CHAMBERS

Abstract In this paper we report on the design and test of a 14-channel VLSI chip to perform the current to frequency conversion for parallel plate strip ionization chambers. The chambers measure the intensity and the geometrical characteristics of a therapeutical beam.

Construction and test of the final CMS Barrel Drift Tube Muon Chamber prototype

A prototype of the CMS Barrel Muon Detector incorporating all the features of the final chambers was built using the mass production assembly procedures and tools. The performance of this prototype was studied in a muon test beam at CERN and the results obtained are presented in this paper.

Large scale validation of the M5L lung CAD on heterogeneous CT datasets

PURPOSE M5L, a fully automated computer-aided detection (CAD) system for the detection and segmentation of lung nodules in thoracic computed tomography (CT), is presented and validated on several image datasets. METHODS M5L is the combination of two independent subsystems, based on the Channeler Ant Model as a segmentation tool [lung channeler ant model (lungCAM)] and on the voxel-based neural approach. The lungCAM was upgraded with a scan equalization module and a new procedure to recover the nodules connected to other lung structures; its classification module, which makes use of a feed-forward neural network, is based of a small number of features (13), so as to minimize the risk of lacking generalization, which could be possible given the large difference between the size of the training and testing datasets, which contain 94 and 1019 CTs, respectively. The lungCAM (standalone) and M5L (combined) performance was extensively tested on 1043 CT scans from three independent datasets, including a detailed analysis of the full Lung Image Database Consortium/Image Database Resource Initiative database, which is not yet found in literature. RESULTS The lungCAM and M5L performance is consistent across the databases, with a sensitivity of about 70% and 80%, respectively, at eight false positive findings per scan, despite the variable annotation criteria and acquisition and reconstruction conditions. A reduced sensitivity is found for subtle nodules and ground glass opacities (GGO) structures. A comparison with other CAD systems is also presented. CONCLUSIONS The M5L performance on a large and heterogeneous dataset is stable and satisfactory, although the development of a dedicated module for GGOs detection could further improve it, as well as an iterative optimization of the training procedure. The main aim of the present study was accomplished: M5L results do not deteriorate when increasing the dataset size, making it a candidate for supporting radiologists on large scale screenings and clinical programs.

Monte Carlo simulation of ripple filters designed for proton and carbon ion beams in hadrontherapy with active scanning technique

Proton and carbon ion beams have a very sharp Bragg peak. For proton beams of energies smaller than 100 MeV, fitting with a gaussian the region of the maximum of the Bragg peak, the sigma along the beam direction is smaller than 1 mm, while for carbon ion beams, the sigma derived with the same technique is smaller than 1 mm for energies up to 360 MeV. In order to use low energy proton and carbon ion beams in hadrontherapy and to achieve an acceptable homogeneity of the spread out Bragg peak (SOBP) either the peak positions along the beam have to be quite close to each other or the longitudinal peak shape needs to be broaden at least few millimeters by means of a properly designed ripple filter. With a synchrotron accelerator in conjunction with active scanning techniques the use of a ripple filter is necessary to reduce the numbers of energy switches necessary to obtain a smooth SOBP, leading also to shorter overall irradiation times. We studied the impact of the design of the ripple filter on the dose uniformity in the SOBP region by means of Monte Carlo simulations, implemented using the package Geant4. We simulated the beam delivery line supporting both proton and carbon ion beams using different energies of the beams. We compared the effect of different kind of ripple filters and their advantages.

A method for the inter-calibration of a matrix of sensors

We present a quick and easy method for the calibration of a matrix of sensors. The algorithm is based on a three-step irradiation procedure which relies only on the constancy of the delivered fluence at each step. With this method the gain of each sensor is derived relative to a reference detector. The algorithm has been applied to a matrix of (32 x 32) ionization chambers. After the calibration coefficients have been applied, by comparing the response of the matrix of chambers to a reference detector over a large field, we determined that the fluence measurement of individual chambers is better than 0.7%. The algorithm solves the cumbersome problem of the relative gain calibration of a matrix of a large number of sensors.

INSIDE in-beam positron emission tomography system for particle range monitoring in hadrontherapy

Abstract. The quality assurance of particle therapy treatment is a fundamental issue that can be addressed by developing reliable monitoring techniques and indicators of the treatment plan correctness. Among the available imaging techniques, positron emission tomography (PET) has long been investigated and then clinically applied to proton and carbon beams. In 2013, the Innovative Solutions for Dosimetry in Hadrontherapy (INSIDE) collaboration proposed an innovative bimodal imaging concept that combines an in-beam PET scanner with a tracking system for charged particle imaging. This paper presents the general architecture of the INSIDE project but focuses on the in-beam PET scanner that has been designed to reconstruct the particles range with millimetric resolution within a fraction of the dose delivered in a treatment of head and neck tumors. The in-beam PET scanner has been recently installed at the Italian National Center of Oncologic Hadrontherapy (CNAO) in Pavia, Italy, and the commissioning phase has just started. The results of the first beam test with clinical proton beams on phantoms clearly show the capability of the in-beam PET to operate during the irradiation delivery and to reconstruct on-line the beam-induced activity map. The accuracy in the activity distal fall-off determination is millimetric for therapeutic doses.

Radiation damage studies of a recycling integrator VLSI chip for dosimetry and control of therapeutical beams

A VLSI chip based on a recycling integrator has been designed and built to be used as front-end readout of detectors for dosimetry and beam monitoring. The chip is suitable for measurements with both conventional radiotherapy accelerators (photon or electron beams) and with hadron accelerators (proton or light ion beams). As the chips might be located at few centimeters from the irradiation area and they are meant to be used in routine hospital practice, it is mandatory to assert their damage to both electromagnetic and neutron irradiation. We have tested a few chips on a X-ray beam and on thermal and fast neutron beams. Results of the tests are reported and an estimate of the expected lifetime of the chip for routine use is given.

The CNAO system to monitor and control hadron beams for therapy

Hadrotherapy might be the last chance option for patients with cancers growing deep in the body or surrounded by very sensitive organs. The Italian National Center of Oncological Hadrotherapy (CNAO) in Pavia is a synchrotron based center for the treatment of tumors with protons and carbon ion beams. The result of this sophisticated technique is strongly affected by the beam delivery performances. A powerful on-line system to monitor and deliver particles inside the target will be available at CNAO.

Full-beam performances of a PET detector with synchrotron therapeutic proton beams

Treatment quality assessment is a crucial feature for both present and next-generation ion therapy facilities. Several approaches are being explored, based on prompt radiation emission or on PET signals by [Formula: see text]-decaying isotopes generated by beam interactions with the body. In-beam PET monitoring at synchrotron-based ion therapy facilities has already been performed, either based on inter-spill data only, to avoid the influence of the prompt radiation, or including both in-spill and inter-spill data. However, the PET images either suffer of poor statistics (inter-spill) or are more influenced by the background induced by prompt radiation (in-spill). Both those problems are expected to worsen for accelerators with improved duty cycle where the inter-spill interval is reduced to shorten the treatment time. With the aim of assessing the detector performance and developing techniques for background reduction, a test of an in-beam PET detector prototype was performed at the CNAO synchrotron-based ion therapy facility in full-beam acquisition modality. Data taken with proton beams impinging on PMMA phantoms showed the system acquisition capability and the resulting activity distribution, separately reconstructed for the in-spill and the inter-spill data. The coincidence time resolution for in-spill and inter-spill data shows a good agreement, with a slight deterioration during the spill. The data selection technique allows the identification and rejection of most of the background originated during the beam delivery. The activity range difference between two different proton beam energies (68 and 72 MeV) was measured and found to be in sub-millimeter agreement with the expected result. However, a slightly longer (2 mm) absolute profile length is obtained for in-spill data when compared to inter-spill data.

A large dynamic range charge measurement ASIC family for beam monitoring in radiotherapy applications

A family of Application Specific Integrated Circuits ( ASICs ) called TERA have been developed for the readout of pixel and strip gas detectors used in radiotherapy applications. The TERA ASICs are based on the charge balancing integration technique in order to obtain a good linearity over a dynamic range of five order of magnitude.