Quality Control Protocol

In order to perform quality control tests in practice, by means of a quality control protocol, on the gamma scintillation camera and the computer connected with it, it is important to be already familiar with the general principles of a planar gamma camera system -as imaging device used in Nuclear Medicine-

We divide the quality control of a gamma camera system in:

• Acceptance and reference testing to ensure that, a certain gamma camera meets the technical and performance specifications quoted by the manufacturer. Reference measurements are carried out at the time of acceptance testing, at the time that the gamma camera or part of it is taken out of clinical practice and at a standard time of half a year (more or less).
• Routine daily checking to ensure that, each instrument continues to work as required; or to determine the rate of deterioration of the system performance over time.
• Camera-Computer Quality Control to implement methods by which routine monitoring can be performed, to register changes in hardware components or in software and study protocols, that could produce undetected changes in collected quantitative data.

A. Acceptance and reference quality control

A.01 *Physical Inspection- *Detector Head Shielding

* Inspect a gamma camera - computer system, control console, data storage and image display devices for shipping or other damage and production fidelity.

**Measure the adequacy of the detector-head shielding to eliminate background radiation detection.

A.02 Energy Resolution
Test the ability of the system to discriminate between primary and scattered gamma events.

A.03 Uniformity

v Intrinsic Uniformity
Measure the response of the scintillation camera to an homogeneous flux of radiation without variables such as collimators which may change its inherent characteristics

v Intrinsic uniformity for various energy window widths
Test the intrinsic response of gamma camera throughout a range of energy window widths and reveal non-uniformities that may not be apparent during the standard intrinsic uniformity test.

v Intrinsic uniformity for energies other than 140keV
Test the intrinsic response of gamma camera for energies of radionuclides commonly used in diagnostic nuclear imaging

v System Uniformity
Measure the ability of the overall system of gamma camera (with any collimator available fitted) to respond correctly to an homogeneous flux of radiation

A.04 Spatial Resolution

v Intrinsic Spatial Resolution
Define the ability of the gamma camera to accurately determine the original location of a gamma ray on a X-Y plane without collimator mounted on it.

v System Spatial Resolution.
Measure the ability of the overall gamma camera system (collimator fitted on the detector) to accurately determine the original location of a gamma ray on a X-Y plane, without and with scatter medium.


A.05 Spatial Linearity (Distortion)

v Intrinsic Spatial Linearity
Measure the intrinsic characteristic of a scintillation camera that estimates the amount of positional distortion caused by the camera with respect to incident gamma events in the detector


A.06 Count Rate Performance
Count rate performance characterizes the gamma camera ability to accurately function at count rates close to the maximum rate of its operation

v Intrinsic Count Rate Performance.
Test the intrinsic count rate performance of a gamma camera in terms of its response to an increasing flux of incident gamma radiation. Calculate the gamma camera dead time and the observed intrinsic count rate corresponding to a 20% count loss

v Maximum Count Rate Performance.
Test the maximum count rate of a gamma camera

v System Count Rate Performance.
Calculate the overall gamma camera system count rate corresponding to a 20% count loss in a scattering medium

A.07 System Sensitivity
Test the ability of the overall gamma camera system (collimator in place) to efficiently detect incident gamma rays.

v Point Source Sensitivity
Investigate local variations in gamma camera system sensitivity to distinguish their contribution to the overall non-uniformity.

v Plane Sensitivity
Calculate the average overall system sensitivity (finite plane source) on the CFOV plane 




A.08 Multiple Window Spatial Registration
Test how accurately gamma camera positions photons of different energies when detected through different energy windows.
(The positional deviations of an image due to X-Y gain calibration variations at different energies).

A.09 Angular Variation of Spatial Position
Measure the registration of spatial positions as a function of angular position of the gamma camera system.

A.10 Whole Body Imaging Spatial Resolution
Test the whole body gamma camera system resolution both to the parallel and 
perpendicular direction of the camera motion in whole body scanning.


A.11 Planar Gamma Camera Overall Performance
Test all components of a gamma camera system under simulated clinical conditions.


B. Routine Daily Quality Control

B.01 Head movements and Collimator support
Check the collimator and detector head mountings 


B.02 Multi Channel Analyzer (MCA) Energy Calibration
Center the clinically used Multi Channel Analyzer windows on the photopeak

B.03 Flood field Uniformity 
Check the flood field uniformity of the gamma camera system in a daily routine basis 

B.04 Background Count Rate
Check the background count rate of a gamma camera system under routine clinical conditions imaging

B.05 Test of the film imager
Check possible degradation of the information transferred from gamma camera system due to the display process



C. Digital Camera- Computer Quality Control

C.01 Pixel Size Calibration
Estimate the pixel value in mm for all used matrices.

C.02 Test of the gamma camera head- Analogue-to-Digital Converter (ADC)
Test the Analogue-to-Digital Converter linearity

C.03 Basic Timing Test
Check the computer clock and the accuracy of timing information

C.04 Dynamic Acquisition Performance 
Check whether data losses and/or timing errors between frames happen when a dynamic study is carried out .

C.05 Special Functions Test (e.g. ECG gated acquisition)
Test that the interface is triggered correctly from the Electro Cardio Graph (ECG)

C.06 Computer Software Evaluation- Dynamic phantom
Test some aspects of gamma camera computer software supplied by the manufacturer.