P.A. Lojacono

A 62 MeV proton beam for the treatment of ocular melanoma at Laboratori Nazionali del Sud-INFN (CATANIA)

At the INFN Laboratori Nazionali del Sud in Catania (Italy) the first Italian protontherapy facility, named CATANA (Centre di AdroTerapia e Applicazioni Nucleari Avanzate) has been realized in collaboration with the University of Catania. It is based on the use of the 62 MeV proton beam delivered by the K = 800 superconducting cyclotron installed and working at LNS since 1995. The facility is mainly devoted to the treatment of ocular diseases like uveal melanoma. A beam treatment line in air has been realized together with a dedicated positioning patient system. The facility is in operation since the beginning of 2002 and 52 patients have been successfully treated up to now. The main features of CATANA together with the clinical and dosimetric features will be extensively reported; particularly, will be described the proton beam line, that has been entirely realized at LNS, with all its elements, the experimental transversal and depth dose distributions of the 62 MeV proton beam obtained for a final collimator of 25 mm diameter and the experimental depth dose distributions of a modulated proton beam obtained for the same final collimator. Finally, the clinical results over one year of treatments, describing the features of the treated diseases will be reported.

Preliminary investigation on the use of the MOSFET dosimeter in proton beams

Metal Oxide Semiconductor (MOS) device structures can be used to measure ionizing radiation through the mechanism of hole trapping in the oxide layer leading to changing of electrical characteristic of the device. They are a new type of direct reading semiconductor dosimeters. Due to their extremely small physical size, ability to permanently store the accumulated dose, dose-rate independence and their ease of use make them very promising for in vivo dosimetry. They are attractive for dosimetry in small radiation fields used in modern radiation oncology modalities, as conformal radiotherapy, IMRT, stereotactic radiotherapy/radiosurgery and proton therapy. Preliminary results on the use of commercial MOSFET dosimeters (TN-502RD, Thomson & Nielsen Electronics Ltd, Canada) irradiated on therapeutic 62 MeV proton beams are presented. Linearity with absorbed dose, sensibility and energy dependence were investigated. Moreover, the possibility to use of MOSFET dosimeters in order to measure the Output Factors (OF) for very small irradiation fields was verified. The comparison of OF obtained using MOSFETs and other dosimetry systems is reported.

A fast monitoring system for radiotherapeutic proton beams based on scintillating screens and a CCD camera

A facility in which a 62 MeV proton beam is employed in the radiotherapeutic treatment of several ocular disease has been active since March 2002 at Laboratori Nazionali del Sud. A fast and accurate quality control system of such beam has been designed and tested. The system consists of a scintillating screen mounted perpendicularly to the beam axis at a fixed distance and observed by a highly sensitive charge-coupled device camera. The basic idea is the possibility to obtain real time information about the relative spatial dose distribution delivered to tissue through the measurement of the light emission in the scintillating screen. A comparison with the presently used dosimetric system (a motorized silicon diode) that, in the future, will be replaced by the device introduced in this paper (if its experimental performance will be successful) has been carried out. The good capabilities of the system make it worthy of further investigations into its applicability in proton beams monitoring for radiotherapeutic treatments (i.e., reconstruction of depth dose distribution and beam monitoring during patient irradiation).

Dosimetric and clinical experience in eye proton treatment at INFN-LNS

After six years of activity 155 patients have been treated inside the CATANA (Centro di AdroTerapia ed Applicazioni Nucleari Avanzate) facility. CATANA is the first and unique proton therapy facility in which the 62 MeV proton beams, accelerated by a Superconducting Cyclotron, are used for the radio‐therapeutic treatments of choroidal and iris melanomas. Inside CATANA new absolute and relative dosimetric techniques have been developed in order to achieve the best results in terms of treatment precision and dose release accuracy. The follow‐up results for 42 patients demonstrated the efficacy of high energy protons in the radiotherapeutic field and encouraged us in our activity in the battle against cancer

Heavy ions fragmentations measurements at intermediate energies in hadrontherapy and spatial vehicles shielding

The study of the nuclear fragmentation process involves many fields of interest, from the hadrontherapy, the new frontier for cancer therapy, to the spatial vehicles shielding design, to work safely in space with acceptable risks from galactic cosmic ray. Indeed, the measure of the fragmentation cross sections is an important information to estimate how this process modifies dose distributions and biological effectiveness. At present, simulations with analytical codes are used to deal with these problems. Such approach presents considerable uncertainty, especially because of a reduced number of experimental data, both on the fragmentation cross sections and on the different radiation biological effectiveness. All these reasons claimed more fragmentation cross section data, in a wide energy range and with different ions and materials.

Deep characterization of a fast monitoring system for radiotherapeutic proton beams based on scintillating screens and a CCD camera

On August 2004, in the issue of IEEE Transaction on Nuclear Science Vol. 51, n. 4 was published a manuscript describing extensively a fast and accurate quality control system for radiotherapeutic proton beams. The system was developed for a facility, active since March 2002 at Laboratori Nazionali del Sud (Catania, Italy), in which 62 MeV proton beams are employed for treatment of ocular diseases. It consists of a scintillating screen mounted perpendicularly to the beam axis at a fixed distance and observed by a highly sensitive CCD (charge-coupled device) camera. In the manuscript were reported preliminary experimental results and the comparison of the system performances with respect to other conventional systems. In this work is presented a deeper physics characterization of the system in terms of system yield versus proton beam dose rate and its linearity, contrast and background correction, signal to noise ratio and spatial resolution measured as MTF values. The latter was measured using both a sinusoidal pattern method and an edge pattern method. The equivalence between these two methods of MTF evaluation is demonstrated for proton beams. Finally, MTF values calculated for the presented system by means of the edge pattern method is compared with routine dosimetric system values together with associated spatial resolutions.

A silicon pixel detector system as an imaging tool for proton beam characterization

High energy protons represent a very promising alternative in the tumor irradiation, as respect the photon and electron beams. In Italy, the first and at present the only proton-therapy facility, CATANA (Centro di AdroTerapia e Applicazioni Nucleari Avanzate), was built in Catania, at the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS). Here a 62 MeV proton beam, produced by a Superconducting Cyclotron (SC), is used for the treatment of shallow tumors like those of the ocular region. A beam monitoring system, based on ion chambers for dose monitoring and on silicon diodes scanning the beam cross section for the beam quality control. Moreover, gaf-chromic films are used to measure the geometric features of the beams. Even though these systems are stable and reliable, nevertheless they are time consuming and, in the gas-chromic film case, they require an off-line analysis. In this paper we present a feasibility study for using a silicon pixel detector as device for proton beams imaging and characterization. We present the performance of such a device exposed to the CATANA proton beam in terms of dose, dose rate and exposure time response.

2D dosimeter based on monolithic silicon sensors for beam verification in conformal radiotherapy

Due to the features of modern radiotherapy techniques, such as Intensity Modulated Radiation Therapy (IMRT), Stereotactic Treatments with photons and proton therapy, where high spatial dose gradient are often present, detectors to be employed for two-dimensional dose verifications must satisfy narrow requirements. In particular, they have to exhibit high spatial resolution. For these applications, in the framework of the European Integrated project MAESTRO (LSHC-CT-2004-503564) and of the INFN experiment PRIMA, we designed a modular system based on a monolithic silicon segmented sensor. A single sensor has been coupled with readout electronics and tested with satisfactory results by using 6, 10 and 25MV X-rays from a LINAC at the University Hospital of Florence and 62MeV protons at INFN LNS Catania, following MAESTRO procedures. For photons, almost all the channels exhibit performances within project specifications (repeatability ≪0.5%, reproducibility ≪1%, deviation from linearity ≪1%, dose rate dependence ≪1%). For protons, the measured Spread Out Bragg Peak is in good agreement with the one measured with a single diode and the detector shows also a good linearity in the range 20–5000 cGy. The output factors are in agreement with those measured with ionization chamber, single diode or film, within experimental errors.

Production of Inorganic thin Scintillating Films for Ion Beam Monitoring Devices

In this work we present the development of beam monitoring devices consisting of thin CsI(Tl) films deposited on Aluminium support layers. The light emitted by the scintillating layer during the beam irradiation is measured by a CCD-camera. In a first prototype a thin Aluminium support layer of 6 micron allows the ion beam to easily pass through without significant energy loss and scattering effects. Therefore it turns out to be a non-destructive monitoring device to characterize on-line beam shape and beam position without interfering with the rest of the irradiation process. A second device consists of an Aluminium support layer which is thick enough to completely stop the impinging ions allowing to monitor at the same time the beam profile and the beam current intensity. Some samples have been coated by a 100 Å protective layer to prevent the film damage by atmosphere exposition. In this contribution we present our experimental results obtained by irradiating the samples with proton beams at 8.3 and 62 MeV. We also propose some innovative applications of these beam monitoring devices in different nuclear sectors such as cancer proton therapy and high intensity beam accelerators.