The Geant4 Monte Carlo radiation transport toolkit provides the basic services and infrastructure required for the development of flexible simulation frameworks and applications, which have found ...generalized use in high energy physics, nuclear physics, astrophysics, and medical physics research. Object-oriented design provides the possibility to implement or modify any physics process in Geant4 without changing other parts of the code. This feature makes Geant4 open to extension of its physics modeling capabilities and to the implementation of alternative physics models. In this paper, the development of a simulation platform for performance studies and detector optimization of the Clear-PEM scanner, a high-performance positron emission mammography prototype, and the implementation of precise low energy bremsstrahlung angular generators for the Geant4 LowE category are described.
In this work we present a first feasibility study of the ClearPEM technology for simultaneous PET-MR imaging. The mutual electromagnetic interference (EMI) effects between both systems were evaluated ...on a 7T magnet by characterizing the response behavior of the ClearPEM detectors and front-end electronics to pulsed RF power and switched magnetic field gradients; and by analyzing the MR system performance degradation from noise pickup into the RF receiver chain, and from magnetic susceptibility artifacts caused by PET front-end materials.
The ClearPEM scanner is a dedicated system to perform breast imaging with the ability of measuring DOI, allowing an image spatial resolution close to 1.5 mm. The DOI is measured by calculating the ...amplitude asymmetry between the signals produced by two APD, one in the top and other in the bottom of the crystal. The DOI resolution measured in laboratory tests is 2.0 mm. In this paper we present a method to periodically confirm this value with the scanner fully mounted. The DOI resolution obtained with this method was 2.8 mm, which is consistent with the resolution measured during the laboratory tests.
The ClearPEM detector is a dual planar Positron Emission Mammography (PEM) scanner that was developed within the framework of the international Crystal Clear Collaboration at CERN. The scanner is ...being used for preclinical studies and the new phase of the clinical trials will start on the second half of November. A second prototype was build and installed (ClearPEM-Sonic). The main results presented in this paper were obtained with the first prototype. The scanner image performance was evaluated using gelatin phantoms. The methodology included the quantification of the homogeneity (BV) and statistical noise (COV). Lesion detectability was evaluated using parameters such as lesion to background noise (LTBN) and lesion contrast recovery coefficient (CRC). Results indicate BV and COV of the order of 5-9% and 20-24%, respectively. ClearPEM images have been found globally homogeneous showing no artifacts. Small lesion to background ratio (LTB) and lesions of dimensions smaller than 3 mm showed less good contrast, but in most cases we report CRC values between 80% and 100%. The detection of lesions is feasible down to 2-3 mm in diameter.
The EndoTOFPET-US project aims to develop a multimodal detector to foster the development of new biomarkers for prostate and pancreatic tumors. The detector will consist of two main components: an ...external plate, and a PET extension to an endoscopic ultrasound probe. The external plate is an array of LYSO crystals read out by silicon photomultipliers (SiPM) coupled to an Application Specific Integrated Circuit (ASIC). The internal probe will be an highly integrated and miniaturized detector made of LYSO crystals read out by a fully digital SiPM featuring photosensor elements and digital readout in the same chip. The position and orientation of the two detectors will be tracked with respect to the patient to allow the fusion of the metabolic image from the PET and the anatomic image from the ultrasound probe in the time frame of the medical procedure. The fused information can guide further interventions of the organ, such as biopsy or in vivo confocal microscopy.
The isotope 222Rn belongs to the 238U decay chain and can be obtained from natural mineral sources. The fact that radon is a gas and its radionuclide daughters get implanted on surrounding materials ...allows a set of different experiments in radiation physics. These experiments range from isotope decay time measurement to alpha, beta and gamma spectroscopy. To solve the radioactive decay chain equations, a simple iterative method is used as an alternative to the exact analytical solution.
Clear-PEM: A PET imaging system dedicated to breast cancer diagnostics Abreu, M.C.; Aguiar, D.; Albuquerque, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2007, Letnik:
571, Številka:
1
Journal Article
Recenzirano
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The Clear-PEM scanner for positron emission mammography under development is described. The detector is based on pixelized LYSO crystals optically coupled to avalanche photodiodes and readout by a ...fast low-noise electronic system. A dedicated digital trigger (TGR) and data acquisition (DAQ) system is used for on-line selection of coincidence events with high efficiency, large bandwidth and small dead-time. A specialized gantry allows to perform exams of the breast and of the axilla. In this paper we present results of the measurement of detector modules that integrate the system under construction as well as the imaging performance estimated from Monte Carlo simulated data.
Positron emission mammography (PEM) can offer a non-invasive method for the diagnosis of breast cancer. Metabolic images from PEM using 18F-fluoro-deoxy-glucose, contain unique information not ...available from conventional morphologic imaging techniques like X-ray radiography. In this work, the concept of Clear-PEM, the system presently developed in the frame of the Crystal Clear Collaboration at CERN, is described. Clear-PEM will be a dedicated scanner, offering better perspectives in terms of position resolution and detection sensitivity.
We present results on the characterization of the Clear-PEM breast imaging scanner. Clear-PEM is a dual-head Positron Emission Mammography scanner using APD-based detector modules that are capable of ...measuring depth-of-interaction (DOI) with a resolution of 2 mm in LYSO:Ce crystals. The full system comprises 192 detector modules in a total of 6144 LYSO:Ce crystals and 384 32-pixel APD arrays readout by ASICs with 192 input channels, which represents an unprecedented level of integration in APD-based PET systems. The system includes Frontend and Data Acquisition electronics and a robotic gantry for detector placement and rotation. The software implements calibration (energy, time and DOI), normalization and image reconstruction algorithms. In this work, the scanner main technical characteristics, calibration strategies and the spectrometric performance in a clinical environment are presented. Images obtained with point sources and extended uniform sources are also presented. The first commissioning results show 99.7% active channels. After calibration, the dispersion of the channels absolute gain is 15.3%, which demonstrate that despite the large number of channels the system is rather uniform. The mean energy resolution at 511 keV is 15.9% for all channels, and the mean DOI constant is 5.9%/mm, which is consistent with a 2 mm DOI resolution, or better. The coincidence time resolution at 511 keV, for a energy window between 400 and 600 keV, is 5.2 ns FWHM. The image resolution measured with point sources was found to be of the order of 1.3 mm FWHM. The DOI capability was found to have a strong impact on the image sharpness. Images of extended uniform 68 Ge sources, corrected for sensitivity and for the artifacts due detector dead spaces, have good uniformity. First clinical breast images are presented.
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