Gamma Camera System Research Articles

Assessment of Gastric Accommodation by SPECT

Assessment of Gastric Accommodation by SPECT

Development of a compact and high spatial resolution gamma camera system using LaBr3(Ce)

In small animal imaging using a single photon emitting radionuclide, a high spatial resolution gamma camera is required. However, its spatial resolution is limited by the light output of conventional scintillators such as NaI(Tl). We developed and tested a small field-of-view (FOV) gamma camera using a new scintillator, LaBr3(Ce). The LaBr3(Ce) gamma camera consists of a 2mm thick LaBr3(Ce) scintillator, a 2in. 8×8 multi-anode position sensitive photomultiplier tube (Hamamatsu H8500), and a personal computer-based data acquisition system. The LaBr3(Ce) scintillator was directly coupled to the PSPMT and was contained in a hermetically shielded and light tight aluminum case. The signals from the PSPMT were gain corrected, weighted summed, and digitized by 100MHz free running A-D converters in the data acquisition system. The detector part of the gamma camera was encased in a tungsten gamma shield, and a tungsten pinhole collimator was mounted in front of the detector surface. The intrinsic spatial resolution that was measured using a tungsten slit mask was 0.75mm FWHM, and the energy resolution was 8.9% FWHM for 122keV gamma photons. We obtained transmission and emission images that demonstrated the high spatial resolution of the gamma camera system. Approximately two years after the fabrication of the detector, the flood image showed significant distortion due to the change in LaBr3(Ce) of its hygroscopic characteristic. These results confirm that the developed LaBr3(Ce) gamma camera is promising for small animal imaging using a low energy single photon emitting radionuclide if the hygroscopic problem of LaBr3(Ce) will be solved.

Optimization of Large-Angle Pinhole Collimator for Environmental Monitoring System

The purpose of this study was to optimize a large-angle pinhole collimator using Monte Carlo simulation for nuclear survey imaging. Simulations using GATE (Geant4 Application for Tomographic Emission) were performed to model the pinhole gamma camera system. A gamma camera consists of a cone-shaped pinhole collimator with a tungsten aperture and a CsI(Tl) scintillation crystal 6.0 mm thick and 50.0 mm × 50.0 mm in area. The focal length and the acceptance angle of the pinhole collimator were set to 14.5 mm and 120°, respectively. The intrinsic spatial resolution and sensitivity were simulated by changing the pinhole diameter and channel height. The point source of Tc-99m was located 30.0 mm above the center of the pinhole, and the projection data was estimated for pinhole diameter values from 0.5 mm to 4.0 mm while the channel heights were fixed between knife-edge and 3.0 mm. The optimal ranges of channel height and pinhole diameter were determined through evaluation of the intrinsic resolution and sensitivity tradeoff curves. The simulation results allowed us to determine the optimal values of pinhole diameter and channel height to be 1.5 mm and 0.5 mm, respectively, to get intrinsic resolution below 2.0 mm FWHM with a reasonable sensitivity for the system configured in this study. The resolution and sensitivity were measured experimentally, and the simulated and measured data were in good agreement. The results demonstrated that the pinhole collimator designed in this study could be utilized to create a large-angle radiation monitoring system.

First demonstration of 3-D lymphatic mapping in breast cancer using freehand SPECT

Freehand SPECT is a 3-D tomographic imaging modality based on data acquisition with a hand-held detector that is moved freely, in contrast to conventional, fixed gamma camera systems. In this pilot study, the feasibility of freehand SPECT for 3-D lymphatic mapping in breast cancer was evaluated. A total of 85 patients (age: 29-88 years) with an initial diagnosis of invasive breast cancer and no clinical evidence of nodal involvement prospectively underwent sentinel lymph node (SLN) biopsy. Preoperative lymphatic mapping (35-87 MBq (99m)Tc-Nanocoll) included tomographic imaging with a SPECT/CT device (Siemens Symbia T6) serving as reference. Initially, the freehand SPECT approach was assessed in a pilot study consisting of 50 patients. The quality of each freehand SPECT acquisition was assessed and ranked as good, intermediate or poor. In another series comprising a further 35 patients (validation study), a guidance system for the acquisition was implemented based on the results of the pilot study, ensuring acquisitions with good quality. For 3-D tomographic image reconstruction, ad hoc models and iterative reconstruction algorithms were used in all 85 patients. To allow for adequate comparison, SPECT/CT data and freehand SPECT data were registered within the same coordinate system. In the pilot study, freehand SPECT enabled mapping of 24 of 83 SLNs in 20 of 44 patients (3 dropouts, 3 patients without SLN either in SPECT/CT or in freehand SPECT). Using SPECT/CT as reference, the accuracy of freehand SPECT was 77.8% (7/9 nodes) in scans with good quality, while for intermediate and poor quality scans, the accuracy was reduced to 34.3 and 12.8%, respectively. In the validation study, quality feedback improved the results significantly and freehand SPECT enabled the mapping of at least one SLN in 87.5% of the patients (28/32 - 3 dropouts). Compared to the reference method, freehand SPECT showed a sensitivity of 83.3% (35/42 nodes). False-negative findings were related to insufficient scanning time, insufficient coverage of the axillary region, close proximity of the SLN to the injection site and low tracer uptake in the SLNs. In this preliminary study, we could demonstrate that 3-D localization of SLNs is feasible using freehand SPECT technology. Prerequisites for acquisition of a good scan quality, most likely allowing precise SLN mapping, have been defined. This approach has high potential to allow image-guided biopsy and further standardization of SLN dissection, thus bringing 3-D nuclear imaging into the operating room.

MONICA: a compact, portable dual gamma camera system for mouse whole-body imaging.

We describe a compact, portable dual-gamma camera system (named "MONICA" for MObile Nuclear Imaging CAmeras) for visualizing and analyzing the whole-body biodistribution of putative diagnostic and therapeutic single photon emitting radiotracers in animals the size of mice. Two identical, miniature pixelated NaI(Tl) gamma cameras were fabricated and installed "looking up" through the tabletop of a compact portable cart. Mice are placed directly on the tabletop for imaging. Camera imaging performance was evaluated with phantoms and field performance was evaluated in a weeklong In-111 imaging study performed in a mouse tumor xenograft model. Tc-99m performance measurements, using a photopeak energy window of 140 keV+/-10%, yielded the following results: spatial resolution (FWHM at 1 cm), 2.2 mm; sensitivity, 149 cps (counts per seconds)/MBq (5.5 cps/microCi); energy resolution (FWHM, full width at half maximum), 10.8%; count rate linearity (count rate vs. activity), r(2)=0.99 for 0-185 MBq (0-5 mCi) in the field of view (FOV); spatial uniformity, <3% count rate variation across the FOV. Tumor and whole-body distributions of the In-111 agent were well visualized in all animals in 5-min images acquired throughout the 168-h study period. Performance measurements indicate that MONICA is well suited to whole-body single photon mouse imaging. The field study suggests that inter-device communications and user-oriented interfaces included in the MONICA design facilitate use of the system in practice. We believe that MONICA may be particularly useful early in the (cancer) drug development cycle where basic whole-body biodistribution data can direct future development of the agent under study and where logistical factors, e.g., limited imaging space, portability and, potentially, cost are important.

Basic performance and stability of a CdTe solid-state detector panel

We have developed a prototype gamma camera system (R1-M) using a cadmium telluride (CdTe) detector panel and evaluated the basic performance and the spectral stability. The CdTe panel consists of 5-mm-thick crystals. The field of view is 134 x 268 mm comprising 18,432 pixels with a pixel pitch of 1.4 mm. Replaceable small CdTe modules are mounted on to the circuit board by dedicated zero insertion force connectors. To make the readout circuit compact, the matrix read out is processed by dedicated ASICs. The panel is equipped with a cold-air cooling system. The temperature and humidity in the panel were kept at 20 degrees C and below 70% relative humidity. CdTe polarization was suppressed by the bias refresh technique to stabilize the detector. We also produced three dedicated square pixel-matched collimators: LEGP (20 mm-thick), LEHR (27 mm-thick), and LEUHR (35 mm-thick). We evaluated their basic performance (energy resolution, system resolution, and sensitivity) and the spectral stability in terms of short-term (several hours of continuous acquisition) and long-term (infrequent measurements over more than a year) activity. The intrinsic energy resolution (FWHM) acquired with Tc-99m (140.5 keV) was 6.6%. The spatial resolutions (FWHM at a distance of 100 mm) with LEGP, LEHR, and LEUHR collimators were 5.7, 4.9, and 4.2 mm, and the sensitivities were 71, 39, and 23 cps/MBq, respectively. The energy peak position and the intrinsic energy resolution after several hours of operation were nearly the same as the values a few minutes after the system was powered on; the variation of the peak position was <0.2%, and that of the resolution was about 0.3%. Infrequent measurements conducted over a year showed that the variations of the energy peak position and the intrinsic energy resolution of the system were at a similar level to those described above. The basic performance of the CdTe-gamma camera system was evaluated, and its stability was verified. It was shown that the camera could be operated daily for several months without calibration.

Determination of the detective quantum efficiency of gamma camera systems: a Monte Carlo study

The purpose of the present work was to investigate the validity of using the Monte Carlo technique for determining the detective quantum efficiency (DQE) of a gamma camera system and to use this technique in investigating the DQE behaviour of a gamma camera system and its dependency on a number of relevant parameters. The Monte Carlo-based software SIMIND, simulating a complete gamma camera system, was used in the present study. The modulation transfer function (MTF) of the system was determined from simulated images of a point source of (99m)Tc, positioned at different depths in a water phantom. Simulations were performed using different collimators and energy windows. The MTF of the system was combined with the photon yield and the sensitivity, obtained from the simulations, to form the frequency-dependent DQE of the system. As figure-of-merit (FOM), the integral of the 2D DQE was used. The simulated DQE curves agreed well with published data. As expected, there was a strong dependency of the shape and magnitude of the DQE curve on the collimator, energy window and imaging position. The highest FOM was obtained for a lower energy threshold of 127 keV for objects close to the detector and 131 keV for objects deeper in the phantom, supporting an asymmetric window setting to reduce scatter. The Monte Carlo software SIMIND can be used to determine the DQE of a gamma camera system from a simulated point source alone. The optimal DQE results in the present study were obtained for parameter settings close to the clinically used settings.

The impact of reconstruction method on the quantification of DaTSCAN images

Reconstruction of DaTSCAN brain studies using OS-EM iterative reconstruction offers better image quality and more accurate quantification than filtered back-projection. However, reconstruction must proceed for a sufficient number of iterations to achieve stable and accurate data. This study assessed the impact of the number of iterations on the image quantification, comparing the results of the iterative reconstruction with filtered back-projection data. A striatal phantom filled with (123)I using striatal to background ratios between 2:1 and 10:1 was imaged on five different gamma camera systems. Data from each system were reconstructed using OS-EM (which included depth-independent resolution recovery) with various combinations of iterations and subsets to achieve up to 200 EM-equivalent iterations and with filtered back-projection. Using volume of interest analysis, the relationships between image reconstruction strategy and quantification of striatal uptake were assessed. For phantom filling ratios of 5:1 or less, significant convergence of measured ratios occurred close to 100 EM-equivalent iterations, whereas for higher filling ratios, measured uptake ratios did not display a convergence pattern. Assessment of the count concentrations used to derive the measured uptake ratio showed that nonconvergence of low background count concentrations caused peaking in higher measured uptake ratios. Compared to filtered back-projection, OS-EM displayed larger uptake ratios because of the resolution recovery applied in the iterative algorithm. The number of EM-equivalent iterations used in OS-EM reconstruction influences the quantification of DaTSCAN studies because of incomplete convergence and possible bias in areas of low activity due to the nonnegativity constraint in OS-EM reconstruction. Nevertheless, OS-EM using 100 EM-equivalent iterations provides the best linear discriminatory measure to quantify the uptake in DaTSCAN studies.

The Multidimensional Integrated Intelligent Imaging project (MI-3)

MI-3 is a consortium of 11 universities and research laboratories whose mission is to develop complementary metal-oxide semiconductor (CMOS) active pixel sensors (APS) and to apply these sensors to a range of imaging challenges. A range of sensors has been developed: On-Pixel Intelligent CMOS (OPIC)—designed for in-pixel intelligence; FPN—designed to develop novel techniques for reducing fixed pattern noise; HDR—designed to develop novel techniques for increasing dynamic range; Vanilla/PEAPS—with digital and analogue modes and regions of interest, which has also been back-thinned; Large Area Sensor (LAS)—a novel, stitched LAS; and eLeNA—which develops a range of low noise pixels. Applications being developed include autoradiography, a gamma camera system, radiotherapy verification, tissue diffraction imaging, X-ray phase-contrast imaging, DNA sequencing and electron microscopy.

Evaluation of pulmonary nodules and lung cancer with one‐inch crystal gamma coincidence positron emission tomography/CT versus dedicated positron emission tomography/CT

Dedicated positron emission tomography (PET)/CT scanners using BGO and related detectors (d-PET) have become standard imaging instruments in many malignancies. Hybrid gamma camera systems using NaI detectors in coincidence mode (g-PET) have been compared to d-PET but reported usefulness has been variable when gamma cameras with half-inch to three-fourth-inch thick crystals have been used without CT. Our aim was to compare g-PET with a 1-in.-thick crystal and inbuilt CT for lesion localization and attenuation correction (g-PET/CT) and d-PET/CT in patients presenting with potential and confirmed lung malignancies. One hour after (18)F-fluorodeoxyglucose (FDG), patients underwent BGO d-PET/CT from jaw to proximal thigh. This was followed by one to two bed position g-PET/CT 194 +/- 27 min after FDG. Each study pair was independently analysed with concurrent CT. d-PET/CT was interpreted by a radiologist experienced in both PET and CT, and g-PET/CT by consensus reading of an experienced PET physician and an experienced CT radiologist. A TNM score was assigned and studies were then unblinded and compared. Fifty-seven patients underwent 58 scan pairs over 2 years. Eighty-nine per cent concordance was shown between g-PET/CT and d-PET/CT for the assessment of intrapulmonary lesions, with 100% concordance for intrapulmonary lesions >10 mm (36 of 36). Eighty-eight per cent (51 of 58) concordance was shown between g-PET/CT and d-PET/CT for TNM staging. Coincidence imaging using an optimized dual-head 1-in.-thick crystal gamma camera with inbuilt CT compares reasonably well with dedicated PET/CT for evaluation of indeterminate pulmonary lesions and staging of pulmonary malignancies and may be of some value when d-PET/CT is not readily available.

Performance evaluation for pinhole collimators of small gamma camera by MTF and NNPS analysis: Monte Carlo simulation study

Presently, the gamma camera system is widely used in various medical diagnostic, industrial and environmental fields. Hence, the quantitative and effective evaluation of its imaging performance is essential for design and quality assurance. The National Electrical Manufacturers Association (NEMA) standards for gamma camera evaluation are insufficient to perform sensitive evaluation. In this study, modulation transfer function (MTF) and normalized noise power spectrum (NNPS) will be suggested to evaluate the performance of small gamma camera with changeable pinhole collimators using Monte Carlo simulation. We simulated the system with a cylinder and a disk source, and seven different pinhole collimators from 1- to 4-mm-diameter pinhole with lead. The MTF and NNPS data were obtained from output images and were compared with full-width at half-maximum (FWHM), sensitivity and differential uniformity. In the result, we found that MTF and NNPS are effective and novel standards to evaluate imaging performance of gamma cameras instead of conventional NEMA standards.

Standardization of the heart-to-mediastinum ratio of 123I-labelled-metaiodobenzylguanidine uptake using the dual energy window method: feasibility of correction with different camera–collimator combinations

Although the heart-to-mediastinum (H/M) ratio in a planar image has been used for practical quantification in (123)I-metaiodobenzylguanidine (MIBG) imaging, standardization of the parameter is not yet established. We hypothesized that the value of the H/M ratio could be standardized to the various camera-collimator combinations. Standard phantoms consisting of the heart and mediastinum were made. A low-energy high-resolution (LEHR) collimator and a medium-energy (ME) collimator were used. We examined multi-window correction methods with (123)I- dual-window (IDW) acquisition, and planar images were obtained with IDW correction and the LEHR collimator. The images were obtained using the following gamma camera systems: GCA 9300A (Toshiba, Tokyo), E.CAM Signature (Toshiba/Siemens, Tokyo) and Varicam (GE, Tokyo). Cardiac phantom studies demonstrated that contamination of the H/M count ratio was greater with the LEHR collimator and least with the ME collimator. The corrected H/M ratio with the LEHR collimator was similar to that with ME collimators. The uncorrected H/M ratio with the ME collimator was linearly related to the H/M ratio with IDW correction with the LEHR collimator. The relationship between the uncorrected H/M ratios determined with the LEHR (E.CAM) and the ME collimators was y = 0.56x + 0.49, where y = H/M ratio with the E.CAM and x = H/M ratio with the ME collimator. The average normal values for the low-energy collimator (n=18) were 2.2+/-0.2 (initial H/M ratio) and 2.42+/-0.2 (delayed H/M ratio), and for the low/medium-energy (LME) collimator (n=14) were 2.63+/-0.25 (initial H/M ratio) and 2.87+/-0.19 (delayed H/M ratio). H/M ratios in previous clinical studies using LEHR collimators are comparable to those with ME collimators. The IDW-corrected H/M ratios determined with the LEHR collimator were similar to those determined with the ME collimator. This finding could make it possible to standardize the H/M ratio in planar imaging among various collimators in the clinical setting.

TU‐A‐342‐01: Quality Assurance Testing of Gamma Camera and SPECT Systems

Routine maintenance, calibration, and quality control of gamma camera and SPECT imaging systems is crucial for providing the nuclear physician or radiologist images of high quality without artifact. This lecture will provide an overview of the gamma camera and SPECT calibrations, performance measurements, and quality assurance tests, whether they are for routine quality control or annual physics surveys as defined by the ACR accreditation program. A discussion of common artifacts and how to avoid and correct them will be included.Gamma camera and SPECT performance measurements are well defined in documents published by MITA/NEMA and in AAPM Task Group reports. Unfortunately, many of the specified tests cannot be easily done on installed systems in the field. Modifications become necessary, and as a result performance measurements and quality assurance testing of gamma camera and SPECT systems have been quite variable. Not included in the published documents are calibration procedures that are vendor specific. Improper calibrations, particularly uniformity calibration, also lead to unwanted artifacts. It is the burden of the physicist to know which performance tests are critical in the field and to also become familiar with specific calibration procedures of our gamma camera and SPECT systems.Educational Objectives:1. Learn the basic gamma camera and SPECT performance measurements and quality assurance test procedures.2. Become familiar with calibration procedures of current systems.3. Become familiar with the test procedures and the frequency of testing prescribed by the ACR accreditation programs.4. Be able to identify common gamma camera and SPECT image artifacts and how to correct them.

A Simulation Study on Spatial Resolution and Noise Power Spectra of a URA-based Multi-hole Collimator in a Small Gamma Camera

Presently the gamma scintillation camera is widely used in various industrial, environmental and medical diagnostic fields. Two major performance parameters, spatial resolution and noise, are primarily determined by the collimator. The imaging performance of the simple collimator, single pin-hole, and a coded-aperture collimator, uniformly redundant array (URA), are analyzed in this study. Though parallel-hole collimators are used in some medical applications, in principle its performance is equivalent to that of a single-hole collimator and moreover its use is limited to the near-field application only. A coded aperture imaging (CAI) techniques have been proposed for gamma-ray imaging especially for far-field applications such as the astrophysics study or environmental monitoring in order to overcome these limitations of a pin-hole or a parallel-hole collimator.In this study, the simulated gamma images using a monte carlo code, MCNP, were acquired with two different energy windows and two-type and four-different collimators. For the evaluation of spatial resolution and noise power spectra, modulation transfer function (MTF) and normalized noise power spectra (NNPS) were computed for all images. In the result, we found that MTF and NNPS can reflect the different properties of different gamma camera systems.

The detective quantum efficiency (DQE) for evaluating the performance of a small gamma camera system with a uniformly redundant array (URA) collimator

Presently, the gamma scintillation camera is widely used in various industrial, environmental and medical diagnostic fields. Hence, the objective and quantitative evaluation of its imaging performance is required for imaging quality assurance and excessive exposures prevention. In this study, the detective quantum efficiency (DQE) of a small gamma camera with three pinholes (1, 2, and 4 mm in hole diameter) and one-coded aperture (uniformly redundant array (URA); 286 holes, hole diameter 2 mm) collimator was determined using modulation transfer function (MTF), normalized noise power spectrum (NNPS), and incoming signal-to-noise ratio (SNR). We found that the resolution of URA was a little lower than that of the pinhole, 2 mm in hole diameter, and the noise of URA was prominently lower than that of all pinholes. Thus, the DQE of URA was higher than that of the pinhole. We found that the determination of DQE could be a quantitative and effective method to evaluate gamma camera systems performances.

Performance Test Data Analysis of Scintillation Cameras

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, we present a set of image analysis tools to calculate the performance parameters of gamma camera systems from test data acquired according to the National Electrical Manufacturers Association NU 1-2001 guidelines. The calculation methods are either completely automated or require minimal user interaction; minimizing potential human errors. The developed methods are robust with respect to varying conditions under which these tests may be performed. The core algorithms have been validated for accuracy. They have been extensively tested on images acquired by the gamma cameras from different vendors. All the algorithms are incorporated into a graphical user interface that provides a convenient way to process the data and report the results. The entire application has been developed in MATLAB programming environment and is compiled to run as a stand-alone program. The developed image analysis tools provide an automated, convenient and accurate means to calculate the performance parameters of gamma cameras and SPECT systems. The developed application is available upon request for personal or non-commercial uses. </para>

PET-CT is only one option

We read with great interest the editorial comments of Alavi et al. [1] on limitations of positron emission tomography computed tomography (PET-CT) for use in clinical work. We would like to emphasize this aspect and also add a further limitation for the new hybrid imaging modalities, which concerns the discussion of cooperation or fusion with radiology departments. As the colleagues emphasize, there is still a long way to go to establish robust protocols for the use of PET-CT in clinical routine in order to maintain a good patient-based practice and ensure radiation exposure safety of the patients. Therefore, it will be necessary to focus the discussion regarding hybrid imaging modalities on the sophisticated use in routine hospital work rather than to discuss immature political fusion of the imaging specialities. Nuclear medicine has a wide spectrum of functional procedures ,which are not all an immanent part of hybrid systems. From our personal point of view, it is absolutely necessary to interpret nuclear medicine as functional imaging and not to use F-18 fluorodeoxyglucose (FDG) as contrast agent for the X-ray CT scan. PET imaging is easy to perform but complicated in terms of interpretation if you do not consider, for example, different attenuation and scatter correction methods and partial volume corrections. In a department of nuclear medicine, there needs to be good communication between different specialities on a daily basis, such as clinicians, technicians, and physicists. The nuclear medicine community (physicians, physicists, and industry) has still failed to implement dynamic PET scanning in clinical routine. Advanced tools are necessary because—not only for PET imaging but also for routine nuclear medicine applications—it is crucial to give the referring physicians hard facts such as quantitative values rather than standard uptake value (SUV). In our opinion, it is also a tremendous disadvantage to disregard the various tools that have been developed in the past, such as radionuclide venography (RNV), kidney analysis, brain imaging, bleeding source, salivary gland imaging, sentinel node scintigraphy, etc., and replace functional nuclear medicine with “hot-spot” fusion modalities. Unfortunately, the development of new devices rarely enables conversion of the already existing software tools (i.e., semiquantitative lymphoscintigraphy, early uptake renal analysis ) to newly installed computer systems. Whenever we replace a gamma camera system in our department, we have never-ending discussions about the software tools we want to obtain from the industry. In some cases, the manufacturer is no longer able to deliver these tools, and we have to develop them with our team. The industry’s interests are sometimes divergent to clinical practice, and as physicians, we have to follow our own— and particularly our patients’—interests. Therefore, we are of the opinion that nuclear medicine has a wide field of clinical functional investigations and PET-CT is only one option of them.

Orthogonal strip HPGe planar SmartPET detectors in Compton configuration

The evolution of Germanium detector technology over the last decade has lead to the possibility that they can be employed in medical and security imaging. The potential of excellent energy resolution coupled with good position information that Germanium affords removes the necessity for mechanical collimators that would be required in a conventional gamma camera system. By removing this constraint, the overall dose to the patient can be reduced or the throughput of the system can be increased. An additional benefit of excellent energy resolution is that tight gates can be placed on energies from either a multi-lined gamma source or from multi-nuclide sources increasing the number of sources that can be used in medical imaging. In terms of security imaging, segmented Germanium gives directionality and excellent spectroscopic information.

Validation of an iterative reconstruction for a mobile tomographic gamma camera system—The Cardiotom

The Cardiotom is a mobile gamma camera that uses ectomography, an alternative method of acquisition to SPECT. It is designed for early diagnosis of myocardial and cerebral infarctions in the emergency room. Ectomography is a limited view angle method, using a rotating slant hole collimator and a stationary camera head, to acquire projection images. The aim of this work was to validate a fully 3D ML–EM iterative reconstruction algorithm for the Cardiotom. Validation measurements were performed with 99mTc point sources. Resolution in the reconstructed volume was determined in X, Y, and Z directions from the point spread functions. The results were compared with the values for the formerly used filtered back projection (FBP). The new reconstruction algorithm provides greatly improved depth resolution with respect to the FBP method previously implemented on the Cardiotom. Furthermore, for clinical examinations, images can be available for interpretation within 15 min of the injection, therefore, valuable information can be obtained without delaying treatment of the patient.

TU‐A‐M100J‐01: Quality Assurance and Acceptance Testing of Gamma Camera and SPECT Systems

The general purpose gamma camera and those configured for SPECT are the bread‐and‐butter imaging instruments in nuclear medicine, and remains the principle component in systems specifically designed for cardiac SPECT. Routine maintenance, calibration, and quality control of these imaging systems is crucial for providing the nuclear physician or radiologist images of high quality without artifact, the bane of nuclear medicine imaging. Acceptance testing, for the most part, provides baseline measurements that are used as reference data for future comparisons.Performance measurements and quality assurance testing of gamma camera and SPECT have been quite variable. The vendors are very specific about calibration procedures that are done one site, but the quality assurance testing by the customer are left up to the individual laboratories that vary to a large part based on the expertise of the staff. Federal and state radiation safety regulatory agencies purposely do not include any gamma camera quality assurance testing in their regulations. There are now two nuclear medicine accreditation programs, one by the American College of Radiology (ACR) and the other by the Intersocietal Commission for Accreditation of Nuclear Medicine Laboratories (ICANL), that have sought to standardize nuclear medicine imaging and quality assurance procedures performed. Also specified are the qualifications of the personnel who perform and interpret the imaging results.This lecture will provide an overview of the gamma camera and SPECT calibrations, performance measurements, and quality assurance tests, whether they are for acceptance testing or routine quality control. NEMA, ACR and ICANL accreditation program documents, and AAPM Task Group reports will be used as a backdrop for the presentation. A discussion of common image artifacts and how to avoid and correct them will also be included.Educational Objectives:1. Learn the basic gamma camera and SPECT performance measurements and quality assurance test procedures.2. Become familiar with the test procedures and the frequency of testing prescribed by the ACR and ICANL accreditation programs.3. Be able to identify common gamma camera and SPECT image artifacts and how to correct them.