Commercial Gamma Camera Research Articles

Image quality parameters in brain imaging with fan-beam collimator: a Monte Carlo study on radiation scattering effects.

The effects of scattered radiation on image quality in brain imaging with fan-beam collimator were quantitatively evaluated. A commercial gamma camera in conjunction with a fan-beam collimator was simulated using MCNPX code. The effects of radiation scattering on image quality were evaluated by employing the Snyder phantom and comparing the system response to an isotropic 99mTc point source in both spatial and frequency domains. The trans-axial spatial resolution of the obtained point spread functions were studied in the spatial domain, at source-to-collimator distances of 2, 4, 6, 8, and 10cm. At the same distances, the spatial frequencies at 90% (SF0.9) and 10% (SF0.1) of the maximum modulation transfer function were considered in the frequency domain. The maximum difference between the obtained full width at half-maximum in presence and absence of phantom was approximately 5%, while this difference was 14% for full width at tenth maximum. An analysis of system response in the frequency domain demonstrated a large difference of 43% between the obtained SF0.9 values in presence and absence of phantom. In contrast, this difference was a mere ~ 2% between the obtained SF0.1 values. Radiation scattering mainly degrades the image contrast resolution and has no considerable effect on the spatial resolution of the images acquired by the fan-beam collimator. Accordingly, the impact of radiation scattering on image quality was more obvious in frequency domain, and SF0.9 can be considered as an operational parameter for the quantitative assessment of radiation scattering effects on image quality in the frequency domain.

Development and calibration of a new gamma camera detector using large square Photomultiplier Tubes

Large area scintillation detectors applied in gamma cameras as well as Single Photon Computed Tomography (SPECT) systems, have a major role in in-vivo functional imaging. Most of the gamma detectors utilize hexagonal arrangement of Photomultiplier Tubes (PMTs). In this work we applied large square-shaped PMTs with row/column arrangement and positioning. The Use of large square PMTs reduces dead zones in the detector surface. However, the conventional center of gravity method for positioning may not introduce an acceptable result. Hence, the digital correlated signal enhancement (CSE) algorithm was optimized to obtain better linearity and spatial resolution in the developed detector. The performance of the developed detector was evaluated based on NEMA-NU1-2007 standard. The acquired images using this method showed acceptable uniformity and linearity comparing to three commercial gamma cameras. Also the intrinsic and extrinsic spatial resolutions with low-energy high-resolution (LEHR) collimator at 10 cm from surface of the detector were 3.7 mm and 7.5 mm, respectively. The energy resolution of the camera was measured 9.5%. The performance evaluation demonstrated that the developed detector maintains image quality with a reduced number of used PMTs relative to the detection area.

A novel fully integrated handheld gamma camera

In this paper, we present an innovative, fully integrated handheld gamma camera, namely designed to gather in the same device the gamma ray detector with the display and the embedded computing system. The low power consumption allows the prototype to be battery operated.To be useful in radioguided surgery, an intraoperative gamma camera must be very easy to handle since it must be moved to find a suitable view. Consequently, we have developed the first prototype of a fully integrated, compact and lightweight gamma camera for radiopharmaceuticals fast imaging. The device can operate without cables across the sterile field, so it may be easily used in the operating theater for radioguided surgery.The prototype proposed consists of a Silicon Photomultiplier (SiPM) array coupled with a proprietary scintillation structure based on CsI(Tl) crystals. To read the SiPM output signals, we have developed a very low power readout electronics and a dedicated analog to digital conversion system. One of the most critical aspects we faced designing the prototype was the low power consumption, which is mandatory to develop a battery operated device.We have applied this detection device in the lymphoscintigraphy technique (sentinel lymph node mapping) comparing the results obtained with those of a commercial gamma camera (Philips SKYLight). The results obtained confirm a rapid response of the device and an adequate spatial resolution for the use in the scintigraphic imaging.This work confirms the feasibility of a small gamma camera with an integrated display. This device is designed for radioguided surgery and small organ imaging, but it could be easily combined into surgical navigation systems.

SU‐G‐IeP4‐12: Performance of In‐111 Coincident Gamma‐Ray Counting: A Monte Carlo Simulation

Purpose:The decay of In‐111 results in a non‐isotropic gamma‐ray cascade, which is normally imaged using a gamma camera. Creating images with a gamma camera using coincident gamma‐rays from In‐111 has not been previously studied. Our objective was to explore the feasibility of imaging this cascade as coincidence events and to determine the optimal timing resolution and source activity using Monte Carlo simulations.Methods:GEANT4 was used to simulate the decay of the In‐111 nucleus and to model the gamma camera. Each photon emission was assigned a timestamp, and the time delay and angular separation for the second gamma‐ray in the cascade was consistent with the known intermediate state half‐life of 85ns. The gamma‐rays are transported through a model of a Siemens dual head Symbia “S” gamma camera with a 5/8‐inch thick crystal and medium energy collimators. A true coincident event was defined as a single 171keV gamma‐ray followed by a single 245keV gamma‐ray within a specified time window (or vice versa). Several source activities (ranging from 10uCi to 5mCi) with and without incorporation of background counts were then simulated. Each simulation was analyzed using varying time windows to assess random events. The noise equivalent count rate (NECR) was computed based on the number of true and random counts for each combination of activity and time window. No scatter events were assumed since sources were simulated in air.Results:As expected, increasing the timing window increased the total number of observed coincidences albeit at the expense of true coincidences. A timing window range of 200–500ns maximizes the NECR at clinically‐used source activities. The background rate did not significantly alter the maximum NECR.Conclusion:This work suggests coincident measurements of In‐111 gamma‐ray decay can be performed with commercial gamma cameras at clinically‐relevant activities. Work is ongoing to assess useful clinical applications.

SORIS—A standoff radiation imaging system

Abstract The detection of radiological and special nuclear material within the country's borders is a crucial component of the national security network. Being able to detect small amounts of radiological material at large distances is especially important for search applications. To provide this capability General Electric's Research Center has developed, as a part of DNDO's standoff radiation detection system advanced technology demonstration (SORDS-ATD) program, a standoff radiation imaging system (SORIS). This vehicle-based system is capable of detecting weak sources at large distances in relatively short times. To accomplish this, GE has developed a novel coded aperture detector based on commercial components from GE Healthcare. An array of commercial gamma cameras modified to increase the system efficiency and energy range are used as position sensitive detectors. Unlike typical coded aperture systems, however, SORIS employs a non-planar mask and thus does not suffer the typical limitations of partially encoded regions giving it a wide field of view. Source identification is done using both low-statistics anomaly indicators and conventional high-statistics algorithms being developed by Pacific Northwest National Laboratory. The results of scanned areas and threats identified are displayed to the user and overlaid on satellite imagery.

Design and construction of a stand-alone camera system and its clinical application in nuclear medicine

This paper reports investigations into some of the improvements of the performance of `modular' gamma-ray cameras. Each modular camera has a 10×10 cm NaI(Tl) scintillation crystal and four 5×5 cm photomultiplier tubes (PMTs). When the gamma-ray photons interact with the crystal, scintillation flashes are emitted from the crystal and detected by the PMTs. The PMTs then convert the light flashes to current pulses. A digital computing circuitry processes the PMT outputs and assigns an estimated ( x, y) coordinate corresponding to the location of interaction of each gamma-ray photon in the crystal and thus an image is formed. This paper is concerned with improvements and clinical applications of the modular cameras. We do the camera characterization by measuring spatial resolution and sensitivity of the modular camera and compare these characteristics to those of a commercial gamma camera. We design and construct a stand-alone planar imaging system based on the modular camera. This imager is examined with a set of phantoms and clinical tests to demonstrate the clinical feasibility of the stand-alone system.