Also, poor energy resolution translates directly into. Imaging and detectors for medical physics lecture 5. Effect of counts per image on the gamma camera uniformity. Pdf the most basic and sensitive routine quality control qc of a gamma camera is that of. 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. 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. Quality assurance and quality control in nuclear medicine. Gamma camera with image uniformity by energy correction. A comparison between two methods of performing the daily.
Camera uniformity may be evaluated either intrinsically i. 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. Planar imaging and the characteristics of acquisition. 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. 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. Flood field non uniformity is translated into tomographic images as major artifacts because it distorts the data obtained at each projection. 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. List performance characteristics of gamma cameras and features affecting performance. This may relate to collimator damage or non uniformity in a cylindrical flood. A new correction method for gamma camera nonuniformity. List basic gamma camera calibrations and how they affect performance. A non uniform area may be visualized as a hot spot or a cold spot. Edge packing higher sensitivity at edge statistical variation. List qc tests for gamma cameras required by accrediting organizations.
The three key elements for checking the gamma camera are. Evaluation of detector non uniformity is the most common practice in present day nuclear medicine quality control procedures. Gamma camera intrinsic uniformity in an unstable power. Required equipment, phantoms and sources for intrinsic uniformity.
Co57 flood source bad energy correction table generated due to wrong positioning. Any non uniformity must be rejected and resolved before patient testing to diminish artifacts and falsepositive or falsenegative patient consequences. Nuclear medicine equipment and supplies quality control. Enabling smartphone authentication with builtin camera.
Any nonuniformity must be eliminated before patient testing to. Before using gamma camera, day to day evaluation and judgment of flood field uniformity are mandatory for patient testing 10 11. 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. Most nuclear medicine computers do not have a suffi ciently large matrix for. 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. Influence of highenergy photons from cobalt57 flood. Gamma camera sensitivity should be uniform across the entire face of the detector. If the scintillation gamma camera is fitted with a uniformity correction circuit the test should be performed with and without the circuit enabled. An evaluation of cusum analysis and control charts applied. Lars johansson, in principles of translational science in medicine.
Quantification of the uniformity images reflected these findings. The number of counts used to form each image was 5, 10 and 30 million. Before using gamma camera, daytoday evaluation and judgment of floodfield uniformity are mandatory for patient testing 10 11. Both images show nonuniformity because the 57co source was imaged with a. Intrinsic uniformity and relative sensitivity quality. Position patient as close to collimator face as possible reference. This paper describes a computer program that is used to analyze the field uniformity of gamma cameras. 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. Uniformity correction matrix corrects residual non. Gammacamera uniformity as a function of energy and count. Iaea quality control atlas for scintillation camera systems. 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. Pdf intrinsic uniformity test for a dual head spect gamma camera.
Patient lies beneath gamma camera positioned close to. Internal uniformity test by a tc99m point source non homogeneous image due to pmts mistuning and a pmt defect. Non uniformity refers to the intensity variation from a uniform flood source. Quality control of scintillation cameras planar and spect aapm. A total of 143 intrinsic uniformity test results for a new gamma camera in use in an envi.
Pdf quality control of gamma camera with spect systems. Pdf effect of energy window width on planer and spect. Measurement of uniformity and multiple head registration. Quality control of gamma camera using phantom ct scan. If spect image quality is related to overall camera performance, then using an extrinsic uniformity correction method rather than an. Uniformity testing of a dualhead gamma camera with a. Energy spectra of a new57co source, obtained with an external 1024. Many parameters can be derived from computer analysis of the image of a uniform flood source to obtain quantitative measures of uniformity. Measuring intrinsic uniformity gamma camera point source 400800 uci 5 ufov diameter distance 515 million counts min. 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. Gamma camera intrinsic uniformity in an unstable power supply. Fine tuning and alignment of the large field of view lfov. Pdf quality control of gamma camera with spect system is highly.
Co57 flood source bad energy correction table generated. Pdf effect of counts per image on the gamma camera uniformity. The usefulness of indices measuring gamma camera non uniformity 6 december 2000 physics in medicine and biology, vol. The latter are essential for an automated analysis. The daily floods collected on the gamma camera are digitized and analyzed. Quantitative assessment of field uniformity for gamma. Even small errors introduced from statistical uncertainties might be of. In the present study, we investigated the effect of widow. The camera s picture is saved as a raw file to prevent any image processing done by the camera. The poorer uniformity, when the uniformity correction circuit is disabled, does not represent a malfunction. Quality assurance testing of gamma camera and spect systems. Spect has highlighted the need to improve gamma camera performance.
Factors affecting gammacamera nonuniformity iopscience. Alignment of lfov of the gamma camera tc99m technetium flood source was positioned under nai sodium iodide detector to check for flood uniformity. Describe how to perform basic qc tests and assess acceptable performance. 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. The tradeoff between image uniformity improvement and loss of camera sensitivity is maximized. Display measurement a simple approach to smallarea.
What are 5 quality control parameters of a gamma camera. The conventional method of intrinsic uniformity correction accounts only for nonuniformities within the. Flood sources are regularly required for calibrating gamma cameras which employ digital non uniformity correction systems department of health and social security. Basic principles of gamma camera imaging and quality control. Acceptance testing and quality control of gamma cameras. 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. Quality control of scintillation cameras planar and spect. 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. Inherent non uniformities in a gamma camera system are compensated for by reducing the sensitivity for some locations on the detector.
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. 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. A gamma camera is a perfect device for detecting nuclear fission products from either nuclear detonations or nuclear power plant reactors accidents. Given a query image taken by a camera of interest, the camera can be identi. However, it is not clear which best reflect changes in uniformity, or how action levels should be set. 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. Limitations to head movement of dualhead gamma cameras may prevent proper geometry being attained for testing of intrinsic uniformity with a point source. The photoresponse non uniformity prnu 31 of an image sensor has been used as a physical layer. Effect of energy window width on planer and spect image. Sensitivity and count rate is the camera s ability to. Quizlet flashcards, activities and games help you improve your grades. The effects of the following parameters on intrinsic uniformity were studied. 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. 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.
Emission computed tomography ect with ro tating gamma cameras is being increasingly used for nuclear medicine examinations. Tube by tube analysis of field uniformity for gamma cameras. In conclusion, these results show that the intrinsic uniformity of the gamma camera. Us4899054a gamma camera with image uniformity by energy. 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. Effect of source to camera distance and count rate on. Before uniformity correction, modern gamma camera systems typically have integral and differential uniformities between 47% 7. Pdf effect of counts per image on the gamma camera. Since the energy correction offsets direct the energy spectra downwards or the energy window upwards. Persistent nonuniformity indicates oscilloscope malfunction e. 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 usual srgb gamma curve must be cancelled because the measurement is done on linearlight.
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