OpenPET is an open source, modular, extendible, and high-performance platform suitable for multi-channel data acquisition and analysis. Due to the flexibility of the hardware, firmware, and software architectures, the platform is capable of interfacing with a wide variety of detector modules not only in medical imaging but also in homeland security applications. Analog signals from radiation detectors share similar characteristics - a pulse whose area is proportional to the deposited energy and whose leading edge is used to extract a timing signal. As a result, a generic design method of the platform is adopted for the hardware, firmware, and software architectures and implementations. The analog front-end is hosted on a module called a Detector Board, where each board can filter, combine, timestamp, and process multiple channels independently. The processed data is formatted and sent through a backplane bus to a module called Support Board, where 1 Support Board can host up to eight Detector Board modules. The data in the Support Board, coming from 8 Detector Board modules, can be aggregated or correlated (if needed) depending on the algorithm implemented or runtime mode selected. It is then sent out to a computer workstation for further processing. The number of channels (detector modules), to be processed, mandates the overall OpenPET System Configuration, which is designed to handle up to 1,024 channels using 16-channel Detector Boards in the Standard System Configuration and 16,384 channels using 32-channel Detector Boards in the Large System Configuration.
We propose a design for a high-resolution single-photon emission computed tomography (SPECT) system for in vivo /sup 125/I imaging in small animal using pixellated lithium-drifted silicon [Si(Li)] detectors. The proposed detectors are expected to have high interaction probability (>90%), good energy resolution [<15% full-width at half-maximum (FWHM)], and good intrinsic spatial resolution (/spl sim/1 mm FWHM). The SPECT system will consist of a dual head detector geometry with the distance between the detectors ranging 30-50 mm to minimize the imaging distance between the mouse and the detectors. The detectors, each with an active area of 64 /spl times/ 40 mm [64 /spl times/ 40 array of 1 mm/sup 2/ pixels and a 6 mm thick Si(Li) detector], will be mounted on a rotating gantry with an axial field-of-view of 64 mm. The detector signals will be read out by custom application-specific integrated circuits (ASICs). Using a high-resolution parallel-hole collimator, the expected spatial resolution is 1.6 mm FWHM at an imaging distance of 20 mm, and sensitivity is 6.7 cps//spl mu/Ci. /sup 125/I is a readily available radioisotope with a long half-life of 59.4 days and it is commonly used to label biological compounds in molecular biology. Conventional gamma cameras are not optimized to detect the low emission energies (27 to 35 keV) of /sup 125/I. However, Si(Li) detector provides an ideal solution for detecting the low-energy emissions of /sup 125/I. In addition to presenting the design of the system, this paper presents a feasibility study of using Si(Li) detectors to detect the emissions of /sup 125/I.
High speed wave-form sampling is becoming a more reliable method for TOF PET detector signal readout; event information including precise time are extracted from the digitized waveform in an unified signal processing chain. In this readout approach, the processing of larger data due to higher sampling rate would be the challenging issue. We conducted a study on the optimal waveform sampling speed using DRS4 evaluation board. The experimental setup consisted of two Hamamastu R9800 PMTs coupled with LSO crystals (6.3×6.3×25mm 3 ). 22 Na was used for positron source, and the two PMTs outputs of coincidence event were digitized varying DRS4 sampling rate in 0.7 - 5 giga-samples per second (GS/s). Initial results show that the coincidence time resolution of ~250 ps was measured in 2 - 5 GS/s, and becomes larger at the lower sampling rate.
We present the characterization of a positron emission tomograph for prostate imaging that centers a patient between a pair of external curved detector banks (ellipse: 45 cm minor, 70 cm major axis). The distance between detector banks adjusts to allow patient access and to position the detectors as closely as possible for maximum sensitivity with patients of various sizes. Each bank is composed of two axial rows of 20 HR+ block detectors for a total of 80 detectors in the camera. The individual detectors are angled in the transaxial plane to point towards the prostate to reduce resolution degradation in that region. The detectors are read out by modified HRRT data acquisition electronics. Compared to a standard whole-body PET camera, our dedicated-prostate camera has the same sensitivity and resolution, less background (less randoms and lower scatter fraction) and a lower cost. We have completed construction of the camera. Characterization data and reconstructed images of several phantoms are shown. Sensitivity of a point source in the center is 946 cps/mu Ci. Spatial resolution is 4 mm FWHM in the central region.
This paper measures the sample to sample variation in the light yield proportionality of NaI(Tl), and so explores whether this is an invariant characteristic of the material or whether it depends on the chemical and physical properties of the tested samples. We report on the electron response of nine crystals of NaI(Tl), differing in shape, volume, age, manufacturer and quality. The proportionality has been measured at the SLYNCI facility in the energy range between 3.5 to 460 keV. We observe that while samples produced by the same manufacturer at approximately the same time have virtually identical electron response curves, there are significant sample to sample variations among crystals produced by different manufacturers or at different times. In an effort to correlate changes in the electron response with details of the scintillation mechanism, we characterized other scintillation properties, including the gamma response and the x-ray excited emission spectra and decay times, for the nine crystals. While sample to sample differences in these crystals were observed, we have been unable to identify the underlying fundamental mechanisms that are responsible for these differences.
We present the tomographic images and performance measurements of the LBNL positron emission mammography (PEM) camera, a specially designed positron emission tomography (PET) camera that utilizes PET detector modules with depth of interaction measurement capability to achieve both high sensitivity and high resolution for breast cancer detection. The camera currently consists of 24 detector modules positioned as four detector banks to cover a rectangular patient port that is 8.2/spl times/6 cm/sup 2/ with a 5 cm axial extent. Each LBNL PEM detector module consists of 64 3/spl times/3/spl times/30 mm/sup 3/ LSO crystals coupled to a single photomultiplier tube (PMT) and an 8/spl times/8 silicon photodiode array (PD). The PMT provides accurate timing, the PD identifies the crystal of interaction, the sum of the PD and PMT signals (PD+PMT) provides the total energy, and the PD/(PD+PMT) ratio determines the depth of interaction. The performance of the camera has been evaluated by imaging various phantoms. The full-width-at-half-maximum (FWHM) spatial resolution changes slightly from 1.9 mm to 2.1 mm when measured at the center and corner of the field of the view, respectively, using a 6 ns coincidence timing window and a 300-750 keV energy window. With the same setup, the peak sensitivity of the camera is 1.83 kcps//spl mu/Ci.
We have constructed a second-generation Compton coincidence instrument, known as the Scintillator Light Yield Non-proportionality Characterization Instrument (SLYNCI), to characterize the electron response of scintillating materials. While the SLYNCI design includes more and higher efficiency HPGe detectors than the original apparatus (five 25%-30% detectors versus one 10% detector), the most novel feature is that no collimator is placed in front of the HPGe detectors. Because of these improvements, the SLYNCI data collection rate is over 30 times higher than the original instrument. In this paper, we present a validation study of this instrument, reporting on the hardware implementation, calibration, and performance. We discuss the analysis method and present measurements of the electron response of two different NaI:Tl samples. We also discuss the systematic errors of the measurement, especially those that are unique to SLYNCI. We find that the apparatus is very stable, but that careful attention must be paid to the energy calibration of the HPGe detectors.
The probability of possible values for the four angles of the CKM matrix are determined by finding the ${\ensuremath{\chi}}^{2}$ values for each choice of angles fitting to ten standard experiments. The ${\ensuremath{\chi}}^{2}$ isosurface plots are first displayed in the space of three of the CKM angles showing the dependence of the bounds of $\ensuremath{\delta}$ and greatly improving the lower bound on ${V}_{\mathrm{cb}}$. The maximum likelihood ${\ensuremath{\chi}}^{2}$ contour plot in the $\ensuremath{\rho}\ensuremath{-}\ensuremath{\eta}$ plane shows the probability of each location for the vertex of the unitarity triangle which controls $\mathrm{CP}$-violating asymmetries in ${B}^{0}$ decays. We find for ${m}_{t}=150$ GeV that at the $2\ensuremath{\sigma}$ level the signal for asymmetries measuring $sin(2\ensuremath{\beta})$ is at least $sin(2\ensuremath{\beta})\ensuremath{\ge}0.25$. At the $1\ensuremath{\sigma}$ level the signal is at least $sin(2\ensuremath{\beta})\ensuremath{\ge}0.40$, with the preferred range of $sin(2\ensuremath{\beta})=0.6\ifmmode\pm\else\textpm\fi{}0.2$.
