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ABSTRACT: The increasing availability of SPECT/CT devices with advanced technology offers the opportunity for the accurate assessment of the radiation dose to the biological target volume during radionuclide therapy. Voxel dosimetry can be performed employing direct Monte Carlo radiation transport simulations, based on both morphological and functional images of the patient. On the other hand, for voxel dosimetry calculations the voxel S value method can be considered an easier approach than patient-specific Monte Carlo simulations, ensuring a good dosimetric accuracy at least for anatomic regions which are characterized by uniform density tissue. However, this approach has been limited because of the lack of tabulated S values for different voxel dimensions and radionuclides. The aim of this work is to provide a free dataset of values which can be used for voxel dosimetry in targeted radionuclide studies. Seven different radionuclides (89Sr, 90Y, 131I, 153Sm, 177Lu, 186Re, 188Re), and 13 different voxel sizes (2.21, 2.33, 2.4, 3, 3.59, 3.9, 4, 4.42, 4.8, 5, 6, 6.8 and 9.28 mm) are considered. Voxel S values are calculated performing simulations of monochromatic photon and electron sources in two different homogeneous tissues (soft tissue and bone) with DOSXYZnrc code, and weighting the contributions on the basis of the radionuclide emission spectra. The outcomes are validated by comparison with Monte Carlo simulations obtained with other codes (PENELOPE and MCNP4c) performing direct simulation of the radionuclide emission spectra. The differences among the different Monte Carlo codes are of the order of a few per cent when considering the source voxel and the bremsstrahlung tail, whereas the highest differences are observed at a distance close to the maximum continuous slowing down approximation range of electrons. These discrepancies would negligibly affect dosimetric assessments. The dataset of voxel S values can be freely downloaded from the website www.medphys.it.
Physics in Medicine and Biology 01/2012; 57(2):517-33. · 2.83 Impact Factor
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ABSTRACT: In this work we present a comparison of different methods for reconstructing the position of the events detected by gamma cameras with small Field of View. This task was completed within a project aimed to the development of an ultra high resolution, MR compatible PET detector camera head based on SiPM detector. It is well known that the spatial resolution deteriorates and the displacement error (defined as the deviation of the reconstructed position from the true position) increases at the edges of the detector. Here we investigate the possibility of improving the detector performance by using different reconstruction methods. The usual algorithm based on the barycenter fails to track the true position near the edges of the detector. We implemented and tested four different algorithms: the classic barycenter, a modified barycenter method where we consider not the charge collected, but the charge squared (named ``barycenter squared''), an algorithm based on the estimation of the skewness of the distribution of the light (``skewness''), and finally a method based on the minimization of the difference between the distribution of light and a suitable fitting function (``Newton''). It turns out that the use of reconstruction algorithms different from the classic barycenter can help to improve the performance of the system. In particular, the reconstruction error improves, especially at the edges of the detector. Our simulations show that it is feasible to get submillimeter planar spatial resolutions at the center of the detector and of about 1 mm at the edges of the detector.
Journal of Instrumentation 01/2011; 6(01):C01030. · 1.87 Impact Factor
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[show abstract]
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ABSTRACT: In this paper Monte Carlo simulations were performed for X-ray irradiations of breast phantoms of various sizes such as PMMA cylinders of different diameters and a hemi-ellipsoidal PMMA phantom. The aim was the evaluation of the 2D distribution of primary and scattered photons and Scatter-to-Primary Ratio (SPR) in projection images in cone-beam breast Computed Tomography (CT). Irradiation geometry and technique factors reproduce the experimental conditions used for validation measurements with a prototype CT breast scanner. Simulations were performed with GEANT4 software. We varied the phantom diameter and shape, the X-ray tube voltage and added filtration. Magnification was 1.31. SPR increases from 0.4 (at 8 cm cylinder diameter) up to 1.5 (14 cm cylinder diameter) at the centre of the phantom. In the same phantom, SPR has lower values toward the bases of the cylinder than at its centre. The scatter component increases by adopting a 50 kVp or higher tube voltages, up to 80 kVp, and by increasing the added filtration. Simulated and measured lateral profiles across a 14 cm cylinder diameter in projection images show a relative deviation of 4%. Simulations show a different distribution of scatter and SPR in a 14 cm diameter cylinder and 14 cm hemi-ellipsoidal phantom, so questioning the use of simple cylindrical geometries when simulating the attenuation of the pendant breast for scatter correction procedures. The strength and the non-uniformity of the SPR inside the cylindrical phantom decrease as the size of the air gap between object and detector increases.
IEEE Transactions on Nuclear Science 11/2010; · 1.45 Impact Factor
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F. Attanasi,
N. Belcari,
S. Moehrs,
V. Rosso,
S. Vecchio,
G. Cirrone,
G. Cuttone,
P. Lojacono,
F. Romano, N. Lanconelli,
A. Del Guerra
[show abstract]
[hide abstract]
ABSTRACT: At the University of Pisa, the DoPET (Dosimetry with a Positron Emission Tomograph) project has focused on the development and characterization of an ad hoc , scalable, dual-head PET prototype for in-beam treatment planning verification of the proton therapy. In this paper we report the first results obtained with our current prototype, consisting of two opposing lutetium yttrium orthosilicate (LYSO) detectors, each one covering an area of 4.5 × 4.5 cm<sup>2</sup>. We measured the β<sup>+</sup>-activation induced by 62 MeV proton beams at Catana facility (LNS, Catania, Italy) in several plastic phantoms. Experiments were performed to evaluate the possibility to extract accurate phantom geometrical information from the reconstructed PET images. The PET prototype proved its capability of locating small air cavities in homogeneous PMMA phantoms with a submillimetric accuracy and of distinguishing materials with different <sup>16</sup>O and <sup>12</sup>C content by back mapping phantom geometry through the separation of the isotope contributions. This could be very useful in the clinical practice as a tool to highlight anatomical or physiological organ variations among different treatment sessions and to discriminate different tissue types, thus providing feedbacks for the accuracy of dose deposition.
IEEE Transactions on Nuclear Science 07/2010; · 1.45 Impact Factor
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R. Pani,
M.N. Cinti,
R. Pellegrini,
P. Bennati,
S. Ridolfi,
V.O. Cencelli,
A. Fabbri,
F. De Notaristefani,
D. Sacco,
F. Navarria,
S. Lo Meo, N. Lanconelli,
G. Moschini,
P. Boccaccio,
R. Scafe,
G. De Vincentis
[show abstract]
[hide abstract]
ABSTRACT: In this work we report on the performance of the MA-PMT prototype, Hamamatsu H8500C-100 MOD 8, with reduced dynode stages (eight) and super bialkali photocathode (38% Q.E. @ 380 nm). This tube represents the latest technological advancement to improve energy and spatial resolution of gamma imagers. It is particularly suitable for applications involving new high light yield scintillators. To evaluate the performances of this tube, we compared the energy and spatial resolution response with the analogous ones obtained from a standard H8500 MA-PMT coupled to a LaBr<sub>3</sub>:Ce scintillation crystal with the same identity. All measurements were performed with a 64 channel electronic readout. An improvement of about 10% in energy and spatial resolution was found, not properly in agreement with the increased value of quantum efficiency. However, this detector configuration permits to obtain 0.92 mm value of the intrinsic spatial resolution and 7.4% of energy resolution which represent the best results obtained with 4.0 mm thickness continuous LaBr3:Ce crystal.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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R. Pani,
P. Bennati,
R. Pellegrini,
M.N. Cinti,
S. Nourbakhsh,
P. Pani,
V.O. Cencelli,
F. De Notaristefani,
F. Navarria,
S. Lo Meo,
A. Perrotta, N. Lanconelli,
G. Moschini,
P. Boccaccio,
R. Scafe
[show abstract]
[hide abstract]
ABSTRACT: Knowledge of the Depth-Of-Interaction (DOI) in detector is crucial for small ring diameter PET scanner but it is also very important for single photon emission imaging, in particular for applications where very high spatial resolution is required and position distortions caused by slant collimators can strongly affect the final response of the 3D reconstructed image. In addition the DOI determination at 140 keV is the most critical due to thinner crystal thickness and the lower number of scintillation light photons. Continuous scintillation crystals are in principle the most suitable for continuous DOI determination based on the measurements of light width of cones generated at each gamma ray interaction. In this work we propose an analysis based on a Monte Carlo GEANT4 studies and on experimental measurements at 140 keV performed on a small LaBr3:Ce continuous crystal coupled to latest multi-anode PMT Hamamatsu H8500-MOD8 series equipped with super Bialkali photocathode (SBA). The basic idea of this work is that the high light output of LaBr<sub>3</sub>:Ce joint with SBA photodetector can reduces statistical uncertainties related to the light distribution spread determination. Furthermore it can be crucial with a more precise measurement of scintillation light distribution from the 8Ã8 anode array of MAPMT. Measurements and simulation confirm that light distribution spread (SD) is related to DOI, with a DOI resolution of about 2.0-2.2 mm (Monte Carlo) and 2.8-3.0 mm experimental at 140 keV. In addition, we shown how the selection in SD window provide a 10% of spatial resolution improvement, down to (0.85±0.03) mm, for a LaBr<sub>3</sub>(Ce) continuous crystal coupled to the new photodetector H8500-MOD8. This method can open the possibility to build a high-sensitivity detector with DOI capability useful for gamma-ray imaging application.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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V.O. Cencelli,
F. de Notaristefani,
A. Fabbri,
F. Petulla,
E. D'Abramo,
R. Panit,
M.N. Cinti,
P. Bennati,
P. Boccaccio, N. Lanconelli,
G. Moschini,
F. Navarria
[show abstract]
[hide abstract]
ABSTRACT: In recent years a great deal of attention was given to the Hamamatsu Position Sensitive PMTs, due to their suitability for building compact and high resolution gamma cameras. In this framework a great number of solution was proposed for the readout, that vary from the analog readout made with a resistive chain, in some cases including a hardware threshold, to fully digital readouts that read each of the PSPMT anodes individually. In order to obtain the best performance from the PSPMT, a readout that reads each channel individually must be chosen, but a great care must be also taken in designing and tuning the calculation of the point in which the gamma photon has actually interacted with the crystal. This paper describes a 5 cm by 5 cm, gamma camera, based on the Hamamatsu H8500 PSPMT and a continuous La Br<sub>3</sub>: Ce crystal, that makes the readout of each channel individually, up to a sampling frequency of 250 K Sample/sec, and uses a new algorithm, based on mean square estimation, to reconstruct the parameters of the light distribution produced by the interaction with the gamma photon. The system has many advantages: it does not suffer from reduction of the useful field of view of the detector, that is observed in the center of gravity based approach due to the truncation of the light distribution, determined by the limited dimension of the scintillating crystal. This characteristic allows the full exploiting of the detector surface (at the price of a slight lowering of the resolution a the very borders of the crystal); moreover it is easy to compensate for the gain variations in the PSPMT anodes and in the analog front-ends, avoiding spatial distortion of the gamma image; finally, for very high rate sources, the algorithm is inherently able to discriminate for double hits.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 12/2009
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[show abstract]
[hide abstract]
ABSTRACT: We have developed a SPEMT (Single Photon Emission MammoTomography) scanner that is made up of two cameras rotating around the pendulous breast of the prone patient, in Vertical Axis of Rotation (VAoR) geometry. Monte Carlo simulations indicate that the device should be able to detect tumours of 8 mm diameter with a tumour/background uptake ratio of 5:1. The scanner field of view is 41.6 mm height and 147 mm in diameter. Each head is composed of one pixilated NaI(Tl) crystal matrix coupled to three Hamamatsu H8500 64-anodes PMT's read out via resistive networks. A dedicated software has been developed to combine data from different PMT's, thus recovering the dead areas between adjacent tubes. A single head has been fully characterized in stationary configuration both in active and dead areas using a point-like source in order to verify the effectiveness of the readout method in recovering the dead regions. The scanner has been installed at the Nuclear Medicine Division of the University of Pisa for its validation using breast phantoms. The very first tomographic images of a breast phantom show a good agreement with Monte Carlo simulation results.
Journal of Instrumentation 10/2009; 4(10):P10012. · 1.87 Impact Factor
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[show abstract]
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ABSTRACT: Geant4 is an object oriented toolkit created for the simulation of High-Energy Physics detectors. Geant4 allows an accurate modeling of radiation sources and detector devices, with easy configuration and friendly interface and at the same time with great accuracy in the simulation of physical processes. While most Monte Carlo codes do not allow the simulation of the transport and boundary characteristics for optical photons transport generated by scintillating crystal, Geant4 allows the simulation of the optical photons. In this paper we present an application of the Geant4 program for simulating optical photons in SPECT cameras. We aim to study the light transport within scintillators, photomultiplier tubes and coupling devices. To this end, we simulated a detector based on a scintillator, coupled to a photomultiplier tube through a glass window. We compared simulated results with experimental data and theoretical models, in order to verify the good matching with our simulations. We simulated a pencil beam of 140 keV photons impinging the crystal at different locations. For each condition, we calculated the value of the Pulse Height Centroid and the spread of the charge distribution, as read out by the anode array of the photomultiplier. Finally, the spatial and the energy resolutions of the camera have been estimated by simulated data. In all cases, we found that simulations agree very well with experimental data.
Journal of Instrumentation 07/2009; 4(07):P07002. · 1.87 Impact Factor
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ABSTRACT: Several updated Monte Carlo (MC) codes are available to perform calculations of voxel S values for radionuclide targeted therapy. The aim of this work is to analyze the differences in the calculations obtained by different MC codes and their impact on absorbed dose evaluations performed by voxel dosimetry. Voxel S values for monoenergetic sources (electrons and photons) and different radionuclides (90Y, 131I, and 188Re) were calculated. Simulations were performed in soft tissue. Three general-purpose MC codes were employed for simulating radiation transport: MCNP4C, EGSnrc, and GEANT4. The data published by the MIRD Committee in Pamphlet No. 17, obtained with the EGS4 MC code, were also included in the comparisons. The impact of the differences (in terms of voxel S values) among the MC codes was also studied by convolution calculations of the absorbed dose in a volume of interest. For uniform activity distribution of a given radionuclide, dose calculations were performed on spherical and elliptical volumes, varying the mass from 1 to 500 g. For simulations with monochromatic sources, differences for self-irradiation voxel S values were mostly confined within 10% for both photons and electrons, but with electron energy less than 500 keV, the voxel S values referred to the first neighbor voxels showed large differences (up to 130%, with respect to EGSnrc) among the updated MC codes. For radionuclide simulations, noticeable differences arose in voxel S values, especially in the bremsstrahlung tails, or when a high contribution from electrons with energy of less than 500 keV is involved. In particular, for 90Y the updated codes showed a remarkable divergence in the bremsstrahlung region (up to about 90% in terms of voxel S values) with respect to the EGS4 code. Further, variations were observed up to about 30%, for small source-target voxel distances, when low-energy electrons cover an important part of the emission spectrum of the radionuclide (in our case, for 131I). For 90Y and 188Re, the differences among the various codes have a negligible impact (within few percents) on convolution calculations of the absorbed dose; thus either one of the MC programs is suitable to produce voxel S values for radionuclide targeted therapy dosimetry. However, if a low-energy beta-emitting radionuclide is considered, these differences can affect also dose depositions at small source-target voxel distances, leading to more conspicuous variations (about 9% for 1311) when calculating the absorbed dose in the volume of interest.
Medical Physics 06/2009; 36(5):1543-52. · 2.83 Impact Factor
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S. Vecchio,
F. Attanasi,
N. Belcari,
M. Camarda,
G.A.P. Cirrone,
G. Cuttone,
F. Di Rosa, N. Lanconelli,
S. Moehrs,
V. Rosso,
G. Russo,
A. Del Guerra
[show abstract]
[hide abstract]
ABSTRACT: The in-beam PET is a novel PET application to image the beta<sup>+</sup> activity induced in biological tissues by hadronic therapeutic beams. Thanks to the correlation existing between beam-delivered dose profiles and beam-induced activity profiles, in vivo information about the effective ion paths can be extracted from the in-beam pet image. in situ measurements, immediately after patient irradiation, are recommended in order to exploit the maximum statistics, by also detecting the contribution provided by the very short lived isotopes, e.g. <sup>15</sup>O. A compact, dedicated tomograph should then be developed for such an application, so as to be used in the treatment room. We developed a small PET prototype in order to demonstrate the feasibility of such a technique for the monitoring of proton therapy of ocular tumors at the CATANA facility (Catania, Italy). The prototype consists of two planar heads with an active area of about 5 cm times 5 cm. Each head is made up of a square position sensitive photomultiplier (Hamamatsu H8500) coupled to a matrix of the same size of LYSO scintillating crystals (2 mm times 2 mm times 18 mm pixel dimensions). Dedicated, compact electronic boards are used for the signal multiplexing, amplification and digitization. The distance between the pair can be varied from 10 cm up to a maximum of about 20 cm. The validation of the prototype was performed on plastic phantoms using 62 MeV protons at the CATANA beam line. Different dose distributions were delivered and a good correlation between the distal fall-off of the activity profiles and of the dose profiles was found, i.e., better than 2 mm along the beam direction.
IEEE Transactions on Nuclear Science 03/2009; · 1.45 Impact Factor
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ABSTRACT: A new multi-energy CT for small animals is operative (now only in scanning mode) at the Physics Department of the University of Bologna. The system makes use of a set of quasi-monochromatic X-ray beams produced by means of an Highly-Oriented Pyrolytic Graphite Bragg monochromator. This source is able to provide beams with energy tunable in a range from 20 to 70 keV. Here we present a complete characterization of the source. A theoretical model of the source has been analyzed, according to the known Zachariasen's theory for diffracting crystals. The beams have also been characterized in resolution and intensity, over the accessible range, and we present here some measured spectra. The monochromator system demonstrated an energy spread of about 3 keV (Full Width at Half Maximum-FWHM) at a beam energy of 26 keV. At the same energy, the intensity of the output beam is about 6% of the primary beam.
IEEE Transactions on Nuclear Science 03/2009; · 1.45 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: A new multi-energy CT for small animals is being developed at the Physics Depart-ment of the University of Bologna, Italy. The system makes use of a set of quasi-monochromatic X-ray beams, with energy tunable in a range from 26 to 72 keV. These beams are produced by Bragg diffraction on a Highly Oriented Pyrolytic Graphite crystal. With quasi-monochromatic sources it is possible to perform multi-energy investigation in a more effective way, as compared with conventional X-ray tubes. Triple-energy projection allows to combine a set of three quasi-monochromatic images of an object, in order to obtain a corresponding set of three single-tissue images, which are the mass-thickness map (product of density and thickness) of three reference materials. The triple-energy technique can be applied to the mass-thickness-map reconstruction of a contrast medium, because it is able to remove completely the signal due to other tissues (i.e. the structural background noise). Here, we present a description of the system and the methods for combining the images at the different energies. We also show some results of images acquired at three different energies and of the reconstructed information about the contrast medium (Iodine). We achieved that the measurement of the Iodine mass-thickness agrees very well with the known concentration of the injected Iodine solution.
JINST. 01/2009; 4.
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R. Pani,
R. Pellegrini,
P. Bennati,
M. N. Cinti,
S. Ridolfi,
R. Scafe,
G. De Vincentis,
S. Lo Meo, N. Lanconelli,
F. Navarria,
G. Moschini,
A. Fabbri,
E. D'Abramo,
D. Sacco,
V. Orsolini Cencelli,
F. De Notaristefani
[show abstract]
[hide abstract]
ABSTRACT: In this work we propose an analysis of a novel Low Energy (LE) parallel hole collimator for high resolution single photon emission tomography (SPET) applications. This prototype, realized jointly with Nuclear Fields, is a lead parallel hole collimator with 1.0 mm hexagonal hole, 18 mm length, 0.2 mm septa and 10x10 cm<sup>2</sup> of useful detection area. It has been planned to match the high spatial resolution performances of a compact gamma camera based on LaBr 3 :Ce continuous scintillation crystal. The imaging performances of this prototype are compared with others two parallel collimators, for different dimensions and applications, and a tungsten pinhole collimator ones. All the collimators were tested with a compact scintillation gamma camera based on LaBr 3 :Ce continuous crystal and multi anode photomultipler tube (MA-PMT) Hamamatsu H8500. The high intrinsic spatial resolution of this crystal enhances the response of collimators at short source-to-collimator distance (SCD) overcoming alignment problems with the collimator pattern. From our analysis the collimator prototype seems to be complementary with the use of pinhole one and when coupled to the compact LaBr 3 :Ce gamma camera can allow a very attractive trade-off between spatial resolution, sensitivity and detection area for radionuclide molecular imaging applications.
Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
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[show abstract]
[hide abstract]
ABSTRACT: The possibility to visualize pathological tissues - for example tumor neo-angiogenesis pattern-, using new X-ray imaging technique (such as Multi-Energy subtraction X-ray Imaging) is strictly related to an accurate knowledge of the X-ray absorption coefficients. Unfortunately, μ(E) values are partially derived from Monte Carlo simulation and known only for a little number of pathologies.
Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
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F Attanasi,
N Belcari,
M Camarda,
A Del Guerra,
S Moehrs,
V Rosso,
S Vecchio, N Lanconelli,
G A P Cirrone,
F Di Rosa,
G Russo
[show abstract]
[hide abstract]
ABSTRACT: The higher physical selectivity of proton therapy demands higher accuracy in monitoring of the delivered dose, especially when the target volume is located next to critical organs and a fractionated therapy is applied. A method to verify a treatment plan and to ensure the high quality of the hadrontherapy is to use Positron Emission Tomography (PET), which takes advantage of the nuclear reactions between protons and nuclei in the tissue during irradiation producing beta(+)-emitting isotopes. Unfortunately, the PET image is not directly proportional to the delivered radiation dose distribution; this is the reason why, at the present time, the verification of depth dose profiles with PET techniques is limited to a comparison between the measured activity and the one predicted for the planned treatment by a Monte Carlo model. In this paper we test the feasibility of a different scheme, which permits to reconstruct the expected PET signal from the planned radiation dose distribution along beam direction in a simpler and more direct way. The considered filter model, based on the description of the PET image as a convolution of the dose distribution with a filter function, has already demonstrated its potential applicability to beam energies above 70 MeV. Our experimental investigation provides support to the possibility of extending the same approach to the lower energy range ([40, 70] MeV), in the perspective of its clinical application in eye proton therapy.
Physica Medica 07/2008; 24(2):102-6. · 1.07 Impact Factor
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S. Vecchio,
F. Attanasi,
N. Belcari,
M. Camarda,
G.A. Pablo Cirrone,
G. Cuttone,
A. Del Guerra,
F. Di Rosa, N. Lanconelli,
S. Moehrs,
V. Rosso,
G. Russo
[show abstract]
[hide abstract]
ABSTRACT: The in-beam PET is a novel PET application to image the beta<sup>+</sup> activity induced in biological tissues by hadronic therapeutic beams. Thanks to the correlation existing between beam-delivered dose profiles and beam-induced activity profiles, in vivo information about the effective ion paths can be extracted from the in-beam PET image. In-situ measurements, immediately after patient irradiation, are recommended in order to exploit the maximum statistics, by detecting the contribution provided by short lived isotopes. A compact, dedicated tomograph should then be developed for such an application, so as to be used in the treatment room. We have realized a small PET prototype in order to demonstrate the feasibility of such technique for the monitoring of proton therapy of ocular tumors at the CATANA facility (Catania, Italy). The DoPET (dosimetry with a positron emission Tomograph) tomograph consists of two planar heads, with an active area of about 5 cm x 5 cm. Each head is made up of a squared position sensitive photomultiplier (Hamamatsu H8500) coupled to a matrix of the same size of LYSO scintillating crystals (2 mm times 2 mm times 18 mm pixel dimensions). Dedicated, compact electronic boards are used for the signal multiplexing, amplification and digitization. The distance between the pair can be set from 10 cm up to a maximum of about 20 cm. The validation of the prototype was performed using 62 MeV protons at the CATANA beam line and plastic phantoms. Different dose distributions have been delivered and a good correlation between the distal fall-off of the activity profiles and of the dose profiles was found, i.e., better than 2 mm along the beam direction.
Nuclear Science Symposium Conference Record, 2007. NSS '07. IEEE; 12/2007
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M.N. Cinti,
R. Scafe,
R. Pellegrini,
C. Trotta,
P. Bennati,
S. Ridolfi, N. Lanconelli,
L. Montani,
F. Cusanno,
F. Garibaldi,
J. Telfer,
R. Pani
[show abstract]
[hide abstract]
ABSTRACT: The aim of this paper is to investigate the intrinsic spatial resolution limit by coupling a CsI(Tl) micro-pixel scintillation array to position sensitive photomultipliers (PSPMTs) for ultra-high resolution gamma-ray imaging. On this purpose, 1 mm thick array with 0.2 mm pixel side, 0.4 mm pitch has been realized by Spectra Physics (Hilger). The present scintillation arrays technology is suitable to produce larger crystal areas. In this paper we present spatial resolution and positioning results obtained by coupling the micro-pixel scintillation array to Hamamatsu square PSPMTs: 1rdquo R8520-C12, 1rdquo R5900-L16 and 2rdquo H8500 Flat panel PMT. Preliminary measurements demonstrate better performance in term of uniformity response when micro-pixel array is coupled to a H8500 PSPMT model. This setup carries out an intrinsic spatial resolution lower limit of about 0.6 mm FWHM at 50% FWHM energy resolution, defining it as the minimum scintillation array pitch detectable at 122 keV. The results obtained by R5900-L16 with a better sampling of the scintillation light has shown an improvement of the position linearity in spite of a worse spatial resolution due to the poor light output of scintillation array.
IEEE Transactions on Nuclear Science 07/2007; · 1.45 Impact Factor
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S Vecchio,
N Belcari,
P Bennati,
M Camarda,
R Campanini,
M N Cinti,
A Del Guerra,
E Iampieri, N Lanconelli,
R Pani,
L Spontoni
[show abstract]
[hide abstract]
ABSTRACT: We have developed a tomograph for single photon emission imaging (SPECT) of the breast for the detection of small size tumors. The SPECT is mounted on a ring that is rotating around the breast with the patient in prone position. The breast will be imaged by two opposing detector heads of approximately 5 Â 15 cm 2 each, with a field of view about 13 cm wide. Each head is made up of one pixilated NaI crystal matrix coupled to three Hamamatsu H8500 PMTs. A ''general purpose'' lead collimator is positioned in front of the crystal. Detailed simulations have been made for the optimization and the evaluation of the detector performances. Monte Carlo results indicate that tumors of 8 mm diameter are detectable with a tumor/background uptake ratio of 5:1. The experimental characterization of the detector head is presented. The rotating ring is now being assembled.
Nuclear Instruments and Methods in Physics Research A85.Àm. 01/2007; 5814057(27).
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N. Lanconelli,
R. Campanini,
E. Iampieri,
R. Pani,
M.N. Cinti,
P. Bennati,
N. Belcari,
M. Camarda,
L. Spontoni,
S. Vecchio,
P. Randaccio,
P. Russo,
A. Del Guerra
[show abstract]
[hide abstract]
ABSTRACT: This work is developed within the framework of a larger project, which aims to develop a multimodal CT-SPET system dedicated to breast imaging. The goal of this paper is to optimize the choice of the various parameters involved in the design of a SPET system dedicated to breast imaging. In particular, we simulated different collimators, different tumor to background (T/B) ratios for two different spherical tumors with diameters of 5 mm and 8 mm. The performance of the explored cameras were analyzed in terms of SNR and image contrast (IC) values, calculated on the reconstructed images. In addition, we investigated the visibility limits of the system, by modifying the tumor size, the T/B value, and the diameter of the breast phantom (8 cm, 10 cm, and 13 cm). As a general tendency, we found out that a high-resolution camera is preferable, in terms of image contrast. On the other hand, the general purpose collimator seems to give a smoother image, giving rise to SNR values comparable to those obtained with the high-resolution collimator, even with a reduced contrast. High-sensitivity collimators seem to give a worse response on the reconstructed images. The 8 mm tumor is clearly visible for all the simulated conditions, even if it could be very close to the visibility limit for the high-sensitivity collimator. The 5 mm tumor is close to the visibility limit for general purpose and high-resolution collimators, for a T/B ratio equal to 10:1 and is not visible with high-sensitivity collimator. The smaller tumor is almost obscured by the background with the thickest breast (13 cm diameter).
Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
