Gamma Camera Quality Control

Gamma Camera Quality Control Without adequate quality control, the functional reliability of a nuclear medicine facility is in doubt. Frank P. Dawry Physx.home.comcast.net

Quality Control: A Crucial Component In Ensuring Quality Patient Care • Routine conduction of equipment quality control is a necessity for ensuring quality patient care by establishing quality imaging. • All instrumentation specific to the operations of a nuclear medicine facility must undergo quality control testing on a regular basis to assure reliability and safety. • Quality patient care can only be achieved if optimal diagnostic accuracy is demonstrated through appropriate quality control procedures. • According to published guidelines written by • the American Society of Nuclear Cardiology (ASNC), • the Joint Commission on the Accreditation of Healthcare Organizations (JCAHO), • the Society of Nuclear Medicine (SNM), • as well as radiation safety guidelines issued by the Nuclear Regulatory Commission (NRC), agreement states and other radiology societies, quality control of equipment must be performed routinely and documented. Frank P. Dawry Physx.home.comcast.net

Part of an overall nuclear medicine quality assurance program Survey meter calibration Dose calibrator QC testing Scintillation (thyroid) probe testing Scintillation camera QC testing Computer software testing Monitor performance testing Staff performance ‘Outcomes’ testing Quality Control testing The routine assessment of an instrument in order to confirm acceptable system performance Frank P. Dawry Physx.home.comcast.net

Spatial linearity Energy resolution Flood field uniformity Spatial resolution (intrinsic and extrinsic) System alignment SPECT reconstructed spatial resolution Whole body spatial resolution Multiple window spatial registration Count rate performance System sensitivity Detector shielding Detector sensitivity System volume sensitivity Standards • NEMA – National Electrical Manufacturers Association • Establishes definitions, quantitative measurements of performance characteristics and reporting techniques for the specification of scintillation camera parameters Performed during acceptance testing prior to first use Verified during total system evaluation annually Frank P. Dawry Physx.home.comcast.net

Routine Camera Quality Control procedures • Daily • Visual checking the energy spectrum – “peaking” • Evaluating the system performance with flood sources – “daily floods” • Weekly • Checking the spatial resolution with a bar phantom • Checking the system linearity with a bar phantom • Correcting for system and collimator non-uniformities • Performing camera uniformity analysis • Monthly • Checking the center of rotation for tomographic scans • System sensitivity Frank P. Dawry Physx.home.comcast.net

Scintillation Camera Performance • Extrinsic, or System measurements – with the collimator attached • Give the best indication of clinical performance • Intrinsic measurements– with the collimator off • Useful for comparing the performance of different cameras because they uncouple the camera performance from the collimator performance Frank P. Dawry Physx.home.comcast.net

Camera operation James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

Frank P. Dawry Physx.home.comcast.net

Uniformity • The measure of a camera’s response to a uniform irradiation of the camera surface. • Intrinsic uniformity is measured using a radionuclide point source (~150 uCi Tc-99m) placed approximately 5 crystal diameters away from an uncollimated camera • System or Extrinsic uniformity is measured using a sheet source placed directly on the surface of a collimated camera • 5 to 10 millicuries (mCi) of Co-57 or • 25 mCi Tc-99m in fillable-water tank. Frank P. Dawry Physx.home.comcast.net

Sheet Sources 57Co Sheet Source T1/2 = 270 days 122 keV 10-15 mCi at time of purchase. 99mTc Sheet Source (water filled) T1/2 = 6 hrs. 140 keV 10-15 mCi at time of filling. Frank P. Dawry Physx.home.comcast.net

Daily Flood • 5 million counts • 256 x 256 acquisition matrix • Resulting image should show a uniform distribution across the entire field of view Frank P. Dawry Physx.home.comcast.net

Uniformity parameters • UFOV – useful field of view • CFOV – center field of view • Integral uniformity • The difference between the maximum and the minimum pixel value divided by the sum of these two values X 100 = +/- 100 X (Max – Min)/(Max + Min) • Differential uniformity • The largest difference between any two pixels within a set of 5 contiguous pixels in a row or column (rate of change) = +/- 100 X (Hi – Low)/(Hi + Low) Frank P. Dawry Physx.home.comcast.net

Spatial Resolution / System Linearity“BARS” • Resolution - the ability of a camera to separately image two objects. • If the two objects are seen as a single blurred spot in the image until they are 5mm apart, the resolution is said to be 5mm. • Linearity - the ability of a camera to reproduce a straight line. • 3 million counts, 256 x 256 matrix for extrinsic • 30 million counts 512 x 512 matrix for intrinsic Frank P. Dawry Physx.home.comcast.net

Spatial Resolution James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

Spatial LinearityDeviation from straight line of less than 1.0 mm for UFOV PLES Phantom Quadrant Bar Phantom James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

Intrinsic Uniformity James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

Extrinsic Uniformity James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

Resolution phantoms Moire effect Frank P. Dawry Physx.home.comcast.net

UB gamma camera test pattern One image per detector head is all that's needed to equally and effectively test all quadrants of the gamma camera. Frank P. Dawry Physx.home.comcast.net

Uniformity corrections • Correcting for system and collimator non-uniformities due to small variations in sensitivity. • Applied to tomographic (SPECT) reconstructed images • Acquired for each collimator that is used for SPECT imaging • 30 to 120 million count acquisition • 256 or 512 matrix size Frank P. Dawry Physx.home.comcast.net

Uniformity corrections James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

Camera uniformity analysis • Similar to a daily flood except greater number of counts acquired • ≥30 million counts • 256 x 256 matrix • Useful for tracking of uniformity trends Frank P. Dawry Physx.home.comcast.net

Center of rotation - COR • Used to verify the integrity of the motion of the gantry during tomographic imaging • COR value is the difference between the measured COR and the theoretical COR • Tc-99m point source either centered in the field of view or off centered Acceptable limits < ±2 mm Frank P. Dawry Physx.home.comcast.net

Center of rotation - COR James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

SPECT Phantoms – system performance testing • Jaszczak Frank P. Dawry Physx.home.comcast.net

SPECT Phantoms – tomographic system performance testing Frank P. Dawry Physx.home.comcast.net

SPECT Phantoms – tomographic system performance testing James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

SPECT Phantoms – planar system performance testing James R Halama, PhD Loyola UniversityMedical Center Frank P. Dawry Physx.home.comcast.net

Society of Nuclear Medicine ‘simulator’ phantom program Lumbar Spine Cardiac Frank P. Dawry Physx.home.comcast.net

SPECT phantom Frank P. Dawry Physx.home.comcast.net

ICANL INTERSOCIETAL COMMISSION FORTHE ACCREDITATION OF NUCLEARLABORATORIES Frank P. Dawry Physx.home.comcast.net

PET/CT plus consideration for the CT portion and the merging of the two imaging modalities. Frank P. Dawry Physx.home.comcast.net

SPECT/CTin review • Similar to SPECT with consideration for CT portion and the merging of the two imaging modalities. Frank P. Dawry Physx.home.comcast.net

Gamma Camera Quality Control