Quality control of scintillation cameras planar and spect aapm. Many parameters can be derived from computer analysis of the image of a uniform flood source to obtain quantitative measures of uniformity. Quality assurance and quality control in nuclear medicine. The causes could be the non uniform detection efficiency small differences in pulse height spectrum and non linearity of pm tubes more server or instrument malfunctions. Uniformity testing of a dualhead gamma camera with a. Before using gamma camera, daytoday evaluation and judgment of floodfield uniformity are mandatory for patient testing 10 11. Pdf quality control of gamma camera with spect system is highly. Enabling smartphone authentication with builtin camera. Co57 flood source bad energy correction table generated. Quantitative assessment of field uniformity for gamma. The usual srgb gamma curve must be cancelled because the measurement is done on linearlight. Influence of highenergy photons from cobalt57 flood.
Gamma camera sensitivity should be uniform across the entire face of the detector. List qc tests for gamma cameras required by accrediting organizations. Quality control of scintillation cameras planar and spect. Extrinsic versus intrinsic uniformity correction for. Uniformity it is degree of uniformity of count density in the image when detector is flooded with a spatially uniform flux of incident gamma radiation. Any non uniformity must be rejected and resolved before patient testing to diminish artifacts and falsepositive or falsenegative patient consequences. Since the energy correction offsets direct the energy spectra downwards or the energy window upwards. Required equipment, phantoms and sources for intrinsic uniformity. Fine tuning and alignment of the large field of view lfov.
Limitations to head movement of dualhead gamma cameras may prevent proper geometry being attained for testing of intrinsic uniformity with a point source. List performance characteristics of gamma cameras and features affecting performance. Any nonuniformity must be eliminated before patient testing to. The tradeoff between image uniformity improvement and loss of camera sensitivity is maximized. Inherent non uniformities in a gamma camera system are compensated for by reducing the sensitivity for some locations on the detector. Non uniformity refers to the intensity variation from a uniform flood source. Agency i aea 5, the evaluation of detector non uniformity is the most prevalent practice in present day qua lity control procedures of gamma camera.
Both images show nonuniformity because the 57co source was imaged with a. Quality assurance testing of gamma camera and spect systems. An evaluation of cusum analysis and control charts applied. The daily floods collected on the gamma camera are digitized and analyzed.
Gammacamera uniformity as a function of energy and count. It is characterised by the same pattern of hot brighter and cold darker pixels occurring with images taken under the same illumination conditions in an imaging array. The three key elements for checking the gamma camera are. A total of 143 intrinsic uniformity test results for a new gamma camera in use in an envi. Position patient as close to collimator face as possible reference. Evaluation of detector non uniformity is the most common practice in present day nuclear medicine quality control procedures. Us4899054a gamma camera with image uniformity by energy.
The floodfield images obtained with the57co sources showed non uniformity patterns that were dependent on the age of the cobalt source, the distance of the source to the collimator, and the specific camera type. Gamma camera intrinsic uniformity in an unstable power supply. Even small errors introduced from statistical uncertainties might be of. Intrinsic uniformity and relative sensitivity quality. Tube by tube analysis of field uniformity for gamma cameras. The cold and hot spots were seen on the resulting image showing non uniformity hence the need for processor boards alignment, fine tuning and quality control of the camera. Pdf intrinsic uniformity test for a dual head spect gamma camera. Most nuclear medicine computers do not have a suffi ciently large matrix for. Spect has highlighted the need to improve gamma camera performance. A gamma camera phantom support stand for safer and faster. The live 3 point non uniformity correction without user calibration, combined to the auto gain control and active image enhancement are unique features in the industry which combined to the best quality sensors available on the market allows the owl to achieve. Quality control of gamma camera using phantom ct scan.
Emission computed tomography ect with ro tating gamma cameras is being increasingly used for nuclear medicine examinations. The object of this investigation was, firstly, to study the effectiveness of four simple indices in measuring uniformity and, secondly, to study the effect of photon energy and the use of energy correction circuitry on camera uniformity. If the scintillation gamma camera is fitted with a uniformity correction circuit the test should be performed with and without the circuit enabled. Alignment of lfov of the gamma camera tc99m technetium flood source was positioned under nai sodium iodide detector to check for flood uniformity. Pdf effect of energy window width on planer and spect.
A gamma camera is a perfect device for detecting nuclear fission products from either nuclear detonations or nuclear power plant reactors accidents. A non uniform area may be visualized as a hot spot or a cold spot. Gamma camera with image uniformity by energy correction. Uniformity correction matrix corrects residual non. A comparison between two methods of performing the daily. Describe how to perform basic qc tests and assess acceptable performance. The camera s picture is saved as a raw file to prevent any image processing done by the camera. This quality control atlas for scintillation camera systems has been developed under the auspices of the iaea. Factors affecting gammacamera nonuniformity iopscience. Nonuniformity induced artifacts in singlephoton emission.
The effects of the following parameters on intrinsic uniformity were studied. Flood field non uniformity is translated into tomographic images as major artifacts because it distorts the data obtained at each projection. In the present study, we investigated the effect of widow. Pdf effect of counts per image on the gamma camera uniformity. Internal uniformity test by a tc99m point source non homogeneous image due to pmts mistuning and a pmt defect. Imaging and detectors for medical physics lecture 5. The latter are essential for an automated analysis. Pdf the most basic and sensitive routine quality control qc of a gamma camera is that of.
What are 5 quality control parameters of a gamma camera. Fpn is a general term that identifies a temporally constant lateral non uniformity forming a constant pattern in an imaging system with multiple detector or picture elements. Iaea quality control atlas for scintillation camera systems. Co57 flood source bad energy correction table generated due to wrong positioning. Energy spectra of a new57co source, obtained with an external 1024. Before using gamma camera, day to day evaluation and judgment of flood field uniformity are mandatory for patient testing 10 11. The poorer uniformity, when the uniformity correction circuit is disabled, does not represent a malfunction. Bullseyering artifacts serial ring artifacts uniformity calibration may be necessary for other isotopes non aligned detectors in y linogram spect quality control practices perform gamma qc for each head technologist uniformity correction matrix flood images of. Pdf quality control of gamma camera with spect systems. 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.
Intrinsic uniformity test for a dual head spect gamma camera. Before uniformity correction, modern gamma camera systems typically have integral and differential uniformities between 47% 7. Variations in pmt response and non linearity in x, y positioning of pulses along the field of view is the leading cause of deterioration in gamma camera flood uniformity 8 and this occur whenever the pmt become unstable. This may relate to collimator damage or non uniformity in a cylindrical flood. Lars johansson, in principles of translational science in medicine. List basic gamma camera calibrations and how they affect performance. Effect of energy window width on planer and spect image. When a point source is placed too near to the uncollimated crystal, the detected flood image will be non uniform due to the inverse square law effect, oblique incidence, and increased path. Patient lies beneath gamma camera positioned close to. We sought to determine the best parameters for rapid performance of daily quality control testing of intrinsic uniformity and relative sensitivity for the singlehead gamma camera system in our nuclear medicine department. Pdf effect of counts per image on the gamma camera. Floodfield uniformity is a standard test of overall camera performance response of the detector to a uniform flux of radiation ideally equal image intensity over entire field of view non uniformity indicates detector drift inaccurate corrections the stability of uniformity with time and activity in fast mode is. Acceptance testing and quality control of gamma cameras.
Pdf plus abstract recently there has been some discussion on the dependence of the uniformity of a gamma camera on the energy of the incident photons and on their countrate hannan and bessent, 1974. The program calculates a number of quantities that pertain to the flood image as a whole and also the counts and the standard deviation in small areas centered over. Quizlet flashcards, activities and games help you improve your grades. The conventional method of intrinsic uniformity correction accounts only for nonuniformities within the.
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. Edge packing higher sensitivity at edge statistical variation. Nuclear medicine equipment and supplies quality control. Measuring intrinsic uniformity gamma camera point source 400800 uci 5 ufov diameter distance 515 million counts min.
Non uniformity can be due to many different factors bent septa on a collimation, pmt failure, naitlcrystal, electronics, too much variation between the uniformity correction matrix and the acquired data. Given a query image taken by a camera of interest, the camera can be identi. The photoresponse non uniformity prnu 31 of an image sensor has been used as a physical layer. Camera uniformity may be evaluated either intrinsically i. The number of counts used to form each image was 5, 10 and 30 million. Flood sources are regularly required for calibrating gamma cameras which employ digital non uniformity correction systems department of health and social security. 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 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. Measurement of uniformity and multiple head registration. Some gamma cameras are particularly sensitive to high energy contaminants and may show non uniformities in the flood images when the quality control is performed with a. This paper describes a computer program that is used to analyze the field uniformity of gamma cameras. Quantification of the uniformity images reflected these findings.
Gamma camera intrinsic uniformity in an unstable power. Display measurement a simple approach to smallarea. Gamma camera non uniformity 26 1 three uncorrected flood images at different count densities were acquired each day on the igems 400 at camera for a period of ten working days. Basic principles of gamma camera imaging and quality control. Also, poor energy resolution translates directly into. In conclusion, these results show that the intrinsic uniformity of the gamma camera. Integral and differential uniformities that get to 5% or more may show a ring most common reason for this artifact and is caused by non uniformity that maybe small or centrally located. However, it is not clear which best reflect changes in uniformity, or how action levels should be set. The usefulness of indices measuring gamma camera non uniformity 6 december 2000 physics in medicine and biology, vol. The common sources of artifacts are non uniformity in gamma camera detectors, center of rotation errors, misaligned cameras on multidetector scanner systems, errors in image reconstruction, patient motion and radiotracer uptake in non target organs and attenuation young et al.
Effect of counts per image on the gamma camera uniformity. Sensitivity and count rate is the camera s ability to. Planar imaging and the characteristics of acquisition. Persistent nonuniformity indicates oscilloscope malfunction e. A new correction method for gamma camera nonuniformity. Gamma camera uniformity is often monitored for quality control of performance. Effect of source to camera distance and count rate on. If spect image quality is related to overall camera performance, then using an extrinsic uniformity correction method rather than an. The degree of nonuniformity in the response of a gamma camera to a uniform field of radiation can be defined in terms of the global and local variations in. Measurement of differential uniformity is the most useful indication of the suitability of the spect system.
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