S. Cornacchia

An Innovative CCD-Based High-Resolution CT System for Analysis of Trabecular Bone Tissue

Synchrotron-based digital radiography and microtomography devices are powerful, nondestructive, high-resolution research tools. In this paper, we present a linear system with a pixel size of 22.5 mum and a field-of-view (FOV) 13 cm long and about 1 mm high. The system is composed of a linear converter GOS screen coupled to an intensified electron-bombarded CCD (EBCCD) camera, by means of a rectangular-to-linear fiber optic adapter. This optical guide is composed of seven bundles, each one transporting light in a coherent way to preserve spatial information. In this way, a high spatial resolution over an extended FOV is obtained. The detector works as an X-ray scanner by means of a high-precision translation mechanical device with 18 cm travel range. The total FOV obtained this way is 13 cm long and 18 cm high. The aim of this paper is to demonstrate the feasibility of this system to investigate a large area of a bone and to calculate the appropriate histomorphometric parameters. Here we present an investigation gained at ELETTRA synchrotron facility at Trieste, Italy. A monochromatic 34-keV beam has been used for imaging a human proximal femur, about 9 cm in width, with our system. The reconstructed images (13 cmtimes13 cm) were cross sections containing femoral head, femoral neck, and greater trochanter. The local variations in trabecular and cortical structure of the examined bone were clearly visible at a level not obtainable with medical CT scanners. The used spatial resolution allowed the visualization of thin trabeculae, which typically lie in a range of 100 mum or lower. The quality of the reconstructed cross-section images confirmed that the system presented is a novel tool for high resolution three-dimensional (3-D) imaging of bone structure, with a pixel size over a volume of interest not achievable with conventional microCT scanners

X-ray computed tomography of an ancient large globe

Computed Tomography (CT) is one of the principal non-invasive techniques for the investigation of the inner structure of works of art. The main advantage of using CT is that it provides high resolution 3D information of the analyzed object. CT of large objects can be hampered by the long time needed and by the difficulties regarding the experimental arrangements required. In this paper we present a CT study of an ancient large globe (diameter of about 2.2 m). We set-up an ad hoc system for the analysis of the globe in situ. The system consists of an X-ray tube, a detector made of a GOS scintillator and an EBCCD camera, the movement axes, a vertical moving axis for the tube, a horizontal-vertical axis for the detector, and a rotating platform for the globe. The investigation of the entire globe has required the acquisition of about 32000 planar images, for providing the 3D tomographic reconstruction. The analysis of the reconstructed volume has allowed to estimate the composition of the inner structure of the globe.

Real-time system for dosimetry in IORT (intra operative radiation therapy)

Intraoperative radiation therapy (IORT) is a technique based on delivery of a high dose of ionizing radiation to the cancer tissue, after tumor ablation, during surgery, while reducing the exposure of normal surrounding tissue. The Novac7 is a new linear accelerator expressly conceived to perform in the operating room. This accelerator supplies electron beams with high dose rate. Because these peculiar characteristics, classical dosimetric techniques are not able to give at once a real-time response and an extensive measure of the absorbed dose. The new system is composed by a grid of scintillating optical fibres coupled with two arrays of photodiodes. The instrument samples the delivered beam at 100 Hz. The dedicated software collects the two projection-signals and reconstructs the bi-dimensional image. Moreover it provides a series of dosimetric parameters. We studied an appropriate reconstruction algorithm searching the best compromise between the computational complexity and a high precision. An accelerator ranging from 3 to 12 MeV has been used for the tests. The system is able to give a real time response (within 30 seconds), the resolution is of 1 millimetre. The response is linear versus dose and the measures are 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 results obtained strongly encourage the continuation of this research

Study of an appropriate reconstruction algorithm for an innovative electron beam imaging system for dosimetry in 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. The Novac7 is a new linear accelerator expressly conceived for IORT that supplies electron beams at several energy, with high dose rate. These peculiar characteristics give rise to some complications with classical dosimetric techniques. In the framework of a research contract between ENEA and the Physics Department of Bologna, Italy, an original digital system has been developed to study and visualise the Novac7 electron beam in real time. The system is conceived as a grid consisting of two bundles of scintillating optical fibres (SOP) over-crossing each other, optically coupled with two arrays of photodiodes as read-out system. The problem of image reconstruction can be expressed as follows: there are only two profiles, or data arrays, which correspond respectively to the light emitted along the fibres perpendicular to the X-axis for the X-profile, and along the fibres perpendicular to the Y-axis for the Y-profile. This problem is not dissimilar to the reconstruction problem in tomography where several projections should be composed to trace them back to the original image. Unfortunately, here we have only two profiles: we have two one-dimensional profiles and are seeking one bidimensional image that could produce them. We selected a known beam image acquired by another digital instrument, then we extracted from it the two profiles simulating the acquisition arrays. Subsequently, we tested several reconstruction algorithms on these profiles, comparing the reconstructed image with the original one. We started from the simple sum algorithm until to iterative algorithms, searching the best compromise between the computational complexity and an high precision. We found that the iterative method is the best solution: it respects the geometrical characteristics and the absolute intensity values of the original image. Moreover it can reconstruct the image in a time of less than one second, a very good result.

A CCD-based high resolution CT system for analysis of trabecular bone tissue

This paper illustrates the effectiveness of a new multi-slice CT system to study the trabecular bone tissue. The system is capable of acquiring 3D images of 5600/spl times/5600/spl times/52 voxels on specimens up to 130 mm with a spatial resolution of 22.5 micrometers. This new detector is coupled to a CCD intensified camera (EBCCD) and was patented by the University of Bologna. The CT acquisitions were performed with an experimental setup at Elettra facilities at beamline SYRMEP. The reconstructed images were sections containing the femoral head, femoral neck and trochantere. The used spatial resolution allows to visualize also thin trabeculae, which typically lie in a range below 100 microns. The morphometric trabecular characterization parameters as BV/TV, Tb.Th, Tb.Sp, Tb.N were calculated over three regions of interest. The local variations in trabecular and cortical structure of the examined bone are clearly visible at a level not obtainable with medical CT scanners. The quality of the reconstructed cross sections images confirm that this investigation technique is an advanced tool for high resolution three-dimensional imaging of bone structure.

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

High resolution X-ray analysis of a proximal human femur with synchrotron radiation and an innovative linear detector

Synchrotron based digital radiography and micro tomography devices are powerful, non-destructive, high-resolution research tools. In this study, we present a linear system capable of a nominal spatial resolution of 22.5 micrometers over a Field-Of-View (FOV) of 13 cm long and about 1 mm high. The system is composed of a linear converter GOS screen coupled to an intensified Electron-Bombarded CCD (EBCCD) camera, by means of a rectangular-to-linear fiber optic adapter. This optical guide is composed of seven bundles, each one transporting light in a coherent way to preserve spatial information. In this way, a high spatial resolution over an extended FOV is obtained The detector works as an X-ray scanner by means of a high-precision translation mechanical device. Here we present an investigation gained at ELETTRA synchrotron facility at Trieste (Italy). A monochromatic 34 keV has been used for imaging a human proximal femur, 9 cm in width, with our system. The excellent spatial resolution of the system allows the analysis of the trabecular structure of the bone over the entire FOV of about 10 cm.

Study and development of two innovative electron beam imaging systems for dosimetry in 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. The major stumbling block to the large-scale application of this radiotherapy technique is the transfer of the patient, with an open wound, from the operating room to the radiation therapy bunker, with the consequent organisational problems and the increased risk of infection. To overcome these limitations, Novac7, a new linear accelerator expressly conceived to perform in the operating room, has been developed. It can deliver electron beams of different energies with a high dose rate (up to 20 Gy/min). These peculiar characteristics give rise to some complications with classical dosimetric techniques. In the framework of a research contract between ENEA and the Physics Department of the University of Bologna, Italy, two original systems have been developed to study and visualise the Novac7 electron beam in real time. The first system is composed by an electron-light converter, a cooled CCD camera and a computer with dedicated software. The second dosimeter is based on a grid of scintillating optical fibres coupled with photodiodes. The achieved results prove that the first system is able to obtain two dimensional measurements of dose distributions in real time and it is a good system for quality controls. The second system has the same capabilities of the first one, but moreover it has the possibility to monitor the delivered beam impulse by impulse. The conclusions confirm the capability of both instruments to overcome problems encountered with classic dosimetry, showing that the results obtained strongly encourage the continuation of this research.