Pdf determining spatial resolution of gamma cameras using. Quality control of scintillation cameras planar and spect. Singlephoton spatial and energy resolution enhancement of a columnar csitlemccd gamma camera using maximumlikelihood estimation. Hence, the image produced is a convolution of the gamma camera intrinsic resolution and the slit width or hole spacing. The performance of a gamma camera system is defined by the sharpness and detail of the images it produces, the efficiency with which it detects incident radiation, its ability to measure the energy of the incident. Energy resolution defined as fwhm of photopeak divided by photopeak energy, expressed as percentage since it is energy dependent, for a gamma camera usually specified for tc99m, typically 910% for conventional gamma cameras. Slides to iaea nuclear medicine physics handbook human health. Gamma camera image for a quadratic bar phantom with different slits size to measure the resolution fig4. For current cameras we can only supply you with special collimators, since the standard collimators can only be purchased through the camera manufacturer.
The nema protocol sug gests measurement at 140 kev with uniform irradiation of the useful field of view, without a collimator. In nuclear medicine, single photon emission computed tomography spect anger gamma camera is nowadays one of the most widespread imaging techniques for diagnosis. A technology demonstration workshop on gamma imaging was held at iaea hq and seibersdorf laboratories on 1923 october 2015. Allows for simultaneous imaging of different radioisotopes, for example tc99m 140 kev and i1. As a result, the detection efficiency of the gamma camera detector is somewhat less than would be desirable at higher. Spatial resolution intrinsic resolution r int refers to how well the crystal and pmt system localize an interaction in the crystal. Practically, performance tests of the gamma camera and spect systems must be limited so that. Collimator resolution r coll refers to how well the collimator localizes the gamma ray source in the patient, affected by hole diameter and. This pinhole gamma camera displayed an energy resolution of 25. The applications of scintigraphy include early drug development and nuclear medical imaging to view and analyse images of the human body or the distribution of medically injected, inhaled, or ingested radionuclides emitting gamma rays. Siemens orbiter gamma camera system with intrinsic resolution of 3. Energy resolution is one of the major limitations of gamma camera performance, mainly affecting image contrast and resolution. Hpge is available with higher efficiency nearly 100 % with along with high.
This quality control atlas for scintillation camera systems has been developed under the auspices of the iaea. The use of appropriate clinical mode is also retained, which might affect energy windows. Table 72 summarizes energy resolution for typical gamma rays measured with a. However, plastics have much faster pulse light decay and find use in timing applications, even though they often offer little or no energy resolution. The ergo is ideal for performing planar, gated, and dynamic nuclear medicine. Both cameras were equipped with 55 pm tubes arranged in a hexagonal array and with a rectangular fov measuring 38. Trained technologists may perform some of annual tests. Too many factors such as distance, number of counts, and type of collimator were studied in this paper. As solid state imaging technologies, both produce high quality images that are a vast improvement over the old angerbased technology. Gamma camera pet is markedly inferior to pet imaging with a purpose designed pet scanner, as the scintillator crystal has poor sensitivity for the high energy annihilation photons, and the detector area is significantly smaller. Spectroscopes, or spectrometers, are sophisticated devices designed to measure the spectral power distribution of a source. Analytical and experimental fwhm of a gamma camera. The content has been established from the contributions of many persons and represents a wide range of situations from around the world and from scintillation camera systems produced by different manufacturers.
Gamma and xray detection introduction canberra industries. Overview of todays lecture university of washington. There is a need for a simple method of measuring gamma camera energy resolution, which is practical for technology students as well as for routine quality control. Advances in gamma camera design and in the embodied ct systems, over the. While czt utilizes direct conversion, csi uses indirect conversion with the aid of photodiodes. This lab will assess changes in spatial resolution and sensitivity of the gamma camera as a function of sourcetocollimator distance and collimation type lehr versus melp. Pdf singlephoton spatial and energy resolution enhancement. Jun 20, 2019 the key differences between a czt gamma camera and csi really lie with the conversion technology. The ergo imaging system is digirads advanced solidstate large fieldofview lfov general purpose nuclear medicine camera. Patient lies beneath gamma camera positioned close to. Accurate quantification of gamma camera images is a requirement for. To introduce basic characteristics of a gamma camera, by measuring two gamma camera performance parameters. Quizlet flashcards, activities and games help you improve your grades.
Energy resolution the primary reason for wanting good energy resolution in a gamma camera is that it gives the camera the ability to distinguish scattered from unscattered radiation. Gamma camera energy spectra summed signal from all pmts energy windows balance between accepting all good events importance of sensitivity and rejecting scattered events. Small changes in intrinsic resolution simply alter the modulation of the high and low count areas in the hole or bar pattern image and reduce image contrast. The effect of energy and source location on gamma camera intrinsic. The energy of the gamma rays should be between 50 and. Lukes episcopal hospital, houston, texas objective. Technology demonstration workshop on gamma imaging.
The gamma camera is designed to provide acceptable detection efficiency while maintaining high intrinsic spatial resolution in the energy range of 100200 kev. Physics in nuclear medicine university of michigan. The spatial resolution of a gamma camera is a measure of its ability to resolve small objects in the field of view. We supply collimators for all commercial gamma cameras, new and older types. The key differences between a czt gamma camera and csi really lie with the conversion technology. These rejected events contribute to dead time and reduce the count rate capability of gamma cameras. Digirad was the first to design and commercialise solidstate detector technology for nuclear medicine, and continues to be a leader in the development, manufacture and distribution of solidstate gamma cameras for use in general nuclear. For example, the best energy resolution from a scintillator for 0. Energy resolution isa function of gamma ray energy and therefore the energy at which it is measured must be specified.
Guidelines on quality control for nuclear medicine instrumentation eanm working group authors. The main drawback of this technique is that the sensitivity is inversely proportional to the spatial resolution due to the use of mechanical collimation. If a gamma photon scatters within the patients body via compton scatter it will change direction and, therefore, will not hit the detector at a location corresponding to its location of origin. Naitl energy spectra 140 kev 10% er 20% er c o u n t s energy kev gamma camera energy spectra 140 kev photons, 9. Pdf simple method to measure gamma camera energy resolution. Portable high energy gamma ray imagerd university of michigan. Quality assurance testing of gamma camera and spect systems. High energy collimators are used for iodine1 and f18fdg. Practically, performance tests of the gamma camera and spect systems must be limited so that they can be completed timely. Energy resolution defined as fwhm of photopeak the narrower fwhm the better is the gamma camera at discriminating unscattered and scattered rays typical energy resolution values.
The energy resolution of a detector is defined as the full width of the photopeak at one half of its. Determining spatial resolution of gamma cameras using matlab article pdf available in journal of medical imaging and radiation sciences 481 november 2016 with 560 reads how we measure reads. Pdf determining spatial resolution of gamma cameras. Quality assurance testing of gamma camera and spect systems sharon l. Imaging and detectors for medical physics lecture 5. Capabilities of 8 devices over a set of experiments relevant to iaea applications were demonstrated. Affected by crystal thickness, gamma ray energy, scatter in crystal. The better the energy resolution, the narrower the acceptance window can be, and.
Interdetector variability 3, intrinsic andor system spatial resolution linearity 4. On a gamma camera, measurements without a collimator. You can also see the compton backscatter peak and the compton edge. System uniformity with all commonly used collimators for each gamma camera head a. Energy resolution fwhm kev photopeak energy kev x 100. Which would improve spatial resolution in gamma camera images. Position patient as close to collimator face as possible reference. Medium energy collimators are used for medium energy photons of nuclides such as krypton81, gallium67, indium111. There is a need for a simple method of measuring gamma camera energy. Basic principles of gamma camera imaging and quality control. Photopeak daily ensure isotope energy level centered over photopeak. Table 72 summarizes energy resolution for typical gamma rays measured with a naitl.
Acceptance testing and quality control of gamma cameras. Photomultiplier tubes used in these applications are usually tested for energy resolution. Simple method to measure gamma camera energy resolution. Iaea quality control atlas for scintillation camera systems. This singlehead gamma camera is compact, lightweight, portable, and is designed to offer maximum clinical versatility. The energy resolution of a detector is defined as the full width of the photopeak at one half of its maximum. Planar scintigraphy used in nuclear medicine imaging emission imaging radioactive source inside patients body in both spect and planar scintigraphy radiation source used mainly 99 a 140 kev rays hence the name gamma camera. The first quality control julie blust department of nuclear medicine, st. Key differences between a czt gamma camera and a csi imager. Intrinsic resolution improves with higher yray energy and deteriorates with lower energy photons, because greater statistical fluctuations occur in the production of. The need for high performance of organ or tissues images pushed many scientists to study the factors affecting the image resolution. High energy resolution hpge and therefore suitable for radiation spectroscopy. The camera was intended to characterize potential performance gains of compton cameras in nuclear medicine applications.
Spatial resolution can also be defined as the minimum distance between two points such that they can be pictured separately. Once the camera is delivered and installed, verification of the camera specifications constitutes the first quality control test which is performed on the system. Pdf energy resolution is one of the major limitations of gamma camera performance, mainly affecting image contrast and resolution. The essential physics of medical imaging, jt bushberg, ja seibert, em leidholdt jr. The primary reason for wanting good energy resolution in a gamma camera is that it gives the camera the ability to distinguish scattered from unscattered radiation. Most gamma cameras can acquire data using multiple energy windows. Typically, the energy window the difference between upperlevel and lowerlevel discriminators is set to 14%, or 20 kev, centered around 140 kev. The energy resolution depends on the size and type of detector, and the gamma energy. Naitl scintillation detectors the high z of iodine in nai gives good efficiency for gamma ray detection. The list below represents the standard parallelhole collimators we manufacture for legacy gamma camera systems. Assessment of spatial resolution on spect using image. Thus compton scattering reduces image contrast and spatial resolution.
Energy resolution fwhm kev photopeak energy kev x 100 scatter rejection if a gamma photon scatters within the patients body via compton scatter it will change direction and, therefore, will not hit the detector at a location corresponding to its location of origin. The content has been established from the contributions of many persons and represents a wide range of situations from around the world and from scintillation camera systems produced by. The effect of energy and source location on gamma camera intrinsic and extrinsic spatial resolution 1737 camera royal philips electronics, the netherlands. A compton camera for low energy gamma ray imaging in nuclear.
This is comparable to the intrinsic resolution of a gamma camera. There is a need for a simple method of measuring gamma camera energy resolution, which is practical for technology students as well as for routine quality. The energy resolution defines the minimum width of the. The technologies demonstrated comprised cztcdte detectors, a labr3detector and hpge detectors. Energy resolution is one of the most important characteristics in radiation measurement such as gamma cameras and spectrometers.
Detection is achieved either through direct detection of the high energy photon by the sensor or by indirect detection of visible photons emitted from a phosphor or scintillator, either a fiberoptic or a lens coupled to the detector. The effect of energy and source location on gamma camera. Gamma camera systems are chosen based on departmen tal needs and the specifications which the manufacturers define as the camera performance characteristics. The smaller the sigma of the distribution, the higher the energy resolution and the bigger the sigma the lower the energy resolution. Compton scattered photons falling outside the energy window still must be processed by the gamma camera pulseheight analyzer circuitry. Andors high energy camera solutions cover a broad wavelength range, spanning vuv, euv, xray and gamma regions. Progress in nuclear science and technology, volume 4. A modern gamma camera has an energy resolution of 9% to 10 % at 140 kev 99m tc. In the attached sodiumiodide spectrum for cesium 7, the fwhm resolution is about 50 kev, or 7,5%.