A. Berdondini

X-ray 3D computed tomography of large objects: investigation of an ancient globe created by Vincenzo Coronelli

X-ray cone-beam Computed Tomography is a powerful tool for the non-destructive investigation of the inner structure of works of art. With regard to Cultural Heritage conservation, different kinds of objects have to be inspected in order to acquire significant information such as the manufacturing technique or the presence of defects and damages. The knowledge of these features is very useful for determining adequate maintenance and restoration procedures. The use of medical CT scanners gives good results only when the investigated objects have size and density similar to those of the human body, however this requirement is not always fulfilled in Cultural Heritage diagnostics. For this reason a system for Digital Radiography and Computed Tomography of large objects, especially works of art, has been recently developed by researchers of the Physics Department of the University of Bologna. The design of the system is very different from any commercial available CT machine. The system consists of a 200 kVp X-ray source, a detector and a motorized mechanical structure for moving the detector and the object in order to collect the required number of radiographic projections. The detector is made up of a 450x450 mm2 structured CsI(Tl) scintillating screen, optically coupled to a CCD camera. In this paper we will present the results of the tomographic investigation recently performed on an ancient globe, created by the famous cosmographer, cartographer and encyclopedist Vincenzo Coronelli.

Dosimetry of high intensity electron beams produced with dedicated accelerators in Intra-Operative Radiation Therapy (IORT)

The technique of High Dose Intra-Operative Radiation Therapy (HDR-IORT) consists in the delivery of irradiation immediately following the removal of a cancerous mass, where the same incision is used to direct the radiation to the tumour bed. Given its particular characteristics, IORT requires dose measurements that are different from those requested in external radiotherapy treatments. The main reason lies in the fact that in this case a single high dose must be delivered to a volume target whose extension and depths will be determined directly during the operation. Since the possibility of devising a treatment plan using a TPS (Treatment Planning System) is not available, it is necessary to know the physical and geometric characteristics of the beam. Defining the physical characteristics of the beam entails both measuring the delivered dose and defining (monitoring) procedures. In any case a much higher dose will be released than occurs with conventional external accelerators. The ionization chamber recommended by the standard protocols for radiotherapy cannot be used because of the ion recombination inside the gas. In this work we propose the use of a calorimetric phantom, the Dosiort, to measure the beam properties. We describe the main characteristics and some preliminary results of the Dosiort System, which is proposed within the framework of a research project of the INFN (Italian National Institute of Nuclear Physics). The set-up is a solid phantom of density approaching 1 g/cc with sensitive layers of scintillating fibres at fixed a position in a calorimetric configuration for the containment of electrons of energy 4-12 MeV. The prototype will be able to define the physical and geometrical characteristics of the electron beam (quality, isotropy, homogeneity, etc) and to measure the parameters needed to select the energy, the intensity and the Monitor Units (MU) for the exposition: Percentage Depth Dose; Beam profiles; Isodose curves; Values of dose for MU.

The Use of Industrial Computed Tomography in the Study of Archaeological Finds

The successful use of Computed Tomography (CT) as an efficient and powerful non-destructive tool for the study of archaeological artefacts has been reported by several authors (Rossi et al. 1999a, b; Rossi and Casali 2001; Applbaum and Applbaum 2005). The 3D reconstruction of the objects enables the archaeologists to carry out archaeological analyses; information about manufacturing and assembly techniques, as well as information useful for dating artefacts or determining the appropriate maintenance and restoration procedures can be obtained with this technique (Casali 2006). Most of the studies of archaeological artefacts reported in the literature are carried out using medical CT (Mazansky 1993; Anderson 1995; Allen 2007), whereas investigations performed with industrial CT systems are rather limited. The present study illustrates the results obtained with a high resolution CT system for industrial applications developed in our laboratories. The advantage of our system as compared to medical CT is the higher penetration capability that allows the investigation of high density objects. The system provides isotropic spatial resolution and fast data acquisition due to the cone-beam geometry employed. In this study, we have focused on demonstrating the potential of this procedure for extracting and analysing an item from a cluster. To this aim, we have investigated a ceramic vase with a diameter of 20 cm, filled with ancient coins.

Dosimetry of High Intensity Electron Beams Produced by Dedicated Accelerators in Intra-Operative Radiation Therapy (IORT)

The technique of High Dose Intra-Operative Radiation Therapy (HDR-IORT) consists in the delivery of irradiation immediately following the removal of a cancerous mass, where the same incision is used to direct the radiation to the tumour bed. Given its particular characteristics, IORT requires dose measurements that are different from those requested in external radiotherapy treatments. The main reason lies in the fact that in this case a single high dose must be delivered to a target volume whose extension and depths will be determined directly during the operation. Since the possibility of devising a treatment plan using a TPS (Treatment Planning System) is not available, it is necessary to know the physical and geometric characteristics of the beam. Defining the physical characteristics of the beam entails both measuring the delivered dose and defining (monitoring) procedures. In any case a much higher dose will be released than occurs with conventional external accelerators. The ionization chamber recommended by the standard protocols for radiotherapy cannot be used because of the ion recombination inside the gas. In this work we propose the use of a calorimetric phantom, the Dosiort, to measure the beam properties. We describe the main characteristics and some preliminary results of the Dosiort System, which is proposed within the framework of a research project of the INFN (Italian National Institute of Nuclear Physics). The set-up is a solid phantom of density approaching 1 g/cm3 with sensitive layers of scintillating fibres at fixed a position in a calorimetric configuration for the containment of electrons of energy 4-12 MeV. The prototype will be able to define the physical and geometrical characteristics of the electron beam (energy, isotropy, homogeneity, etc) and to measure the parameters needed to select the energy, the intensity and the Monitor Units (MU) for the exposition: Percentage Depth Dose; Beam profiles; Isodose curves; Values of dose for MU.

Study and realization of real-time in-depth dosimetry system for IORT (intra operative radiation therapy)

Intra Operative Radiation Therapy (IORT) is a technique based on delivery of a high dose of ionising radiation to the cancer tissue, after tumour ablation, during surgery, while reducing the exposure of normal surrounding tissue. Novac7 and Liac are new linear accelerators expressly conceived to perform in the operating room. These accelerators supply electron beams with high dose rate. Because of this peculiar characteristic, classical dosimetric techniques are not able to give at once a real-time response and an extensive measure of the absorbed dose. In past years the authors realized a prototype for IORT dosimetry able to give the real time bi-dimensional image of dose distribution on a single layer. In the framework of a research project funded by the INFN (Italian National Institute of Nuclear Physics), a collaboration between the Physics Department of Bologna, Italy, the Physics Department of Cosenza and the Medicine Department of Catanzaro, Italy, has studied a new system composed of six layers. Each layer includes two orthogonal bundles of scintillating optical fibres. The fibres are optically coupled with four arrays of photodiodes as read-out system. This new system will be able to characterize completely the electron beam in energy, intensity and spatial distribution. In real time it will be able to measure the 3D dose distribution, providing a full check of quality assurance for IORT. The various phases of design, development and characterization of the instrument will be illustrated, as well as some experimental tests performed with the prototype. We verified that the system is able to give a real time response, which is linear versus dose and not affected by the high dose rate. The conclusions confirm the capability of the instrument to overcome problems encountered with classic dosimetry, showing that the obtained results strongly encourage the continuation of this research.

HIGH-ENERGY COMPUTER TOMOGRAPHY MEASUREMENTS IN A MUSEUM AND ANALYSIS OF THE RADIOPROTECTION PROBLEM

Abstract In recent years there has been a growing demand from museums for computed tomography (CT) diagnostic measurements to be performed on famous artworks (sculptures and paintings) inside the museum itself in order to assess whether are they in good condition or need a restoration procedure. The problem of radioprotection becomes critical when the energy used in CT is high, as typically occurs in the case of CT measurements on sculptures, where linacs are used to produce the high-energy X-rays necessary to penetrate marble or metal. In this study we used Monte Carlo simulations in order to evaluate dose distribution inside a museum where a high-energy CT system is used for diagnostic measurements on a sculpture.

3D dosimetry of high intensity therapeutic electron beams

The technique of High Dose Rate Intra-Operative Radiation Therapy (HDR-IORT) consists in the delivery of irradiation immediately following the removal of a cancerous mass, where the same incision is used to direct the radiation to the tumour bed. Given its particular characteristics, IORT requires dose measurements that are different from those requested in external radiotherapy treatments. The main reason lies in the fact that in this case a single high dose must be delivered to a target volume whose extension and depth will be determined directly during the operation. Because of this peculiar characteristics, until now there is not a dosimetric system able to detect the electron beam giving at once a realtime response and an extensive spatial measure of the absorbed dose. In this work we present the results obtained by using two orthogonal layers of a calorimetric phantom, the Dosiort, to measure the beam properties. We describe the main characteristics and some results of the Dosiort System, which is proposed within the framework of a research project of the INFN (Italian National Institute of Nuclear Physics). The final set-up is a solid phantom of density approaching 1 g/cm3 with sensitive layers of scintillating fibres at fixed positions in a calorimetric configuration for the containment of electrons of energy 4–12 MeV. The prototype will be able to define the physical and geometrical characteristics of the electron beam (energy, isotropy, homogeneity, etc) and to measure the parameters needed to select the energy, the intensity and the Monitor Units (MU) for the exposition: Percentage Depth Dose; Beam profiles; Isodose curves; Values of dose per MU. In this paper we report in particular the measurement of the read-out dynamic range and the first qualitative study of the results which can be extracted from the measurements taken with the XY double layer in a test beam.

Monte Carlo optimization of an industrial tomography system

Computed tomography (CT) is becoming a very useful non-destructive testing technique, in the industrial field, since it permits the detection of small inner defects in a reliable and accurate way. In order to get very good performance, in terms of image contrast and spatial resolution, the configuration of the tomography system has to be optimized carefully. Monte Carlo simulations can be a very helpful method, for choosing different conditions and selecting the best configuration of a CT system. In this paper we present a preliminary optimization of an industrial CT apparatus, obtained by means of Monte Carlo simulations. The system is composed of an X-ray tube, filtering and collimation devices, and a detector made of a scintillator coupled to a CCD camera. We focus our attention on large aluminum objects and investigate the contribution of the scattered radiation. Some options have been simulated, for reducing the scattering photons, thus improving the overall image quality