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Combo with "QC Semiconductor Detectors" and 2 others
Terms in this set (33)
AKA efficiency is the detected count rate per unit activity. Desired to improve detectability of small lesions.
Determines the ability of the detector to reject scattered photons rather than the gamma ray energy.
A function of detector size and collimation and decreases rapidly with distance, inversely related to sensitivity. How deep, distance and size.
done quarterly or semiannual, requires tweaking of the amplifier gain to ensure that the preset energy window actually correlates with the gamma ray photopeak energy.
Count rate constancy
(sensitivity) daily check with a long-lived source should be used to verify proper operation. Co57 is recommended, single method for determining whether the probe's performance has changed.
Intraoperative probe performance
done annually, to ensure that it functions optimally.
Battery check, Background determination, constancy check and visual inspection.
Lower than expected constancy reading
energy window not correctly centered on photopeak, calibration is not correct, incorrect source-detector geometery (farther away than usual)
Higher than expected constancy reading
contamination, extraneous radiation source in detectors line of sight.
this is done daily, the technologist checks the peak of a known radioactive source by the camera's energy spectrum.
a daily assessment to measure the camera's ability to produce uniform images from a uniform source or accurate images. A uniform flood source of Tc99m or Co57 is placed on the detector of the camera and an image is taken. This range should be below 5%.
This is performed in combination with uniformity. It assesses the ability of the instrument to detect any radioactive disintegration emitted. Calculated by
cpm/dmp x 100
Performed weekly and assesses the camera's ability to produce image detail and sharpness. Uses a bar phantom.
Performed with resolution and assesses the images for horizontal and vertical line straightness or linear lines.
High calibration flood
Used as a calibration source for the systems images taking 100 million counts or greater. Applied to static, dynamic, and SPECT images to improve image quality and decrease non-uniformities inherent in the system.
Performed annually by comparing the extrinsic and intrinsic uniformity floods. It is then visually inspected for damage.
Number of quality control tests for scintillation camera.
Energy peaking, uniformity
High count calibration flood
Percent Energy window
Window widths are specified as a percent of the photopeak energy. A narrow window of 2-5% should be used for calibration and an wider window of 15-20% for imaging.
evaluates how well a given detector distinguishes between gamma rays of closely spaced energies. Performed quarterly or annually and determines the ability of the instrument to discriminate between different energies.
used to calculate energy resolution.
The nuclear medicine technologist does this to the operating voltage daily with the press of a button.
This daily measure is performed by the nuclear medicine technologist and assesses the instruments consistency from day to day by using a cesium 137 sealed source. Counts are recorded and compared to the previous day.
performed quarterly and evaluates the ability of the instrument to detect radioactive disintegration's.
Formula to calculate efficiency
cpm/dpm x 100
statistical quarterly assessment of the instrument which takes 10 separate counts of a sample.
Sensitivity/constancy, calibration, background check
Energy resolution, chi-square, efficiency
Number of quality control tests for scintillation detector
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