Nuclear Medicine GAMMA CAMERA- weekly and daily QA

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About Gamma camera quality assurance. WEEKLY AND DAILY

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QUALITY CONTROL TESTING OF A SCINTILLATION CAMERADAILY AND WEEKLY : 

QUALITY CONTROL TESTING OF A SCINTILLATION CAMERADAILY AND WEEKLY

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Test1 Set and check energy windows or peaking Frequency – Daily and before imaging different radionuclide Point source of radionuclide to be imaged

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Properly Adjusted 15 % window Improperly adjusted 20 % window Properly Adjusted 20 % window

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Window set to high side of photo peak Window symmetrically positioned Window set to low side of photpeak

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A-Photopeak is caused by the total absorption of the 140 kev gamma rays B. Escape peak –K shell xrays C. Lead peak

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Test 2 Extrinsic or intrinsic low count uniformity images of all camera heads Frequency – Daily 2- 6 million counts

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Improper flood phantom preparation Adherence of RPC particles to inner surface Particulate formation within the liquid Incomplete mixing of radionuclide Air Bubble simulating a PMT malfunction

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Ant view –liver picture 2 photopenic areas (arrows)-Suspected of being artifactual. Planar Extrinsic flood image demonstrating collimator damage as cause

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Subtle non uniformities Increasing non uniformites with time Uniformity corrected flood INTRINSIC FLOOD

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Test 3 Spatial (Distortion) Linearity and Resolution check with bar pattern 1 to 2 weeks

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Non uniformity and loss of resolution Occur when activity is great Resolution returns when activity reduced to proper level

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Intrinsic spatial resolution- 4 quadrant Bar Phantom -2.0,2.5,3.0,3.5mm wide lead bars.

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Test 4 Centre rotation 1 or 2 weeks Point source as recommended by manufacturer

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Reconstructed transaxial images can show the point sources appearing too large or even having a cold center if the centre of the rotation is misaligned Pictures shows rapid deterioration of resolution and introduction of circular artifacts

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Nuclear Med Technology and Techniques-Bernier Physics in Nuclear Medicine-James N sorenson Quality control of NM imaging devices-P.S.Soni Essential physics of medical imaging-Jerrold T Bushberg References:

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