Nuclear Medicine Physics

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Nuclear Medicine Physics Single Photon Emission ComputedTomography SPECT Jerry Allison Ph D Department of Radiology.
Medical College of Georgia A note of thanks toZ J Cao Ph D Medical College of GeorgiaSameer Tipnis Ph D .
G Donald Frey Ph D Medical University of South CarolinaSharing nuclear medicine presentation content Tomographic NM imagingSingle Photon Emission Computed Tomography.
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Physics in Nuclear Medicine Cherry Sorenson and Phelps 4 th edition 2012 Physics in Nuclear Medicine Cherry Sorenson and Phelps 4 th edition 2012 Produce tomographic images by acquiringconventional gamma camera projection data.
at several angles around the patient Similar to CT Emission vs transmissionProvide 3 D images to eliminateoverlaying and underlying activity of a.
better contrast more accurate lesion localization more demanding technically and longer dataacquisition more severe image noise.
SPECT data acquisitionGenerally two detectors mounted at 180 or90 on a rotation gantry SPECT data acquisition a sequence of 2 D static images at.
different angular positions views detector rotation range180 with 2 perpendicular detectors or360 with 2 opposite detectors SPECT Image Acquisition.
Improves spatialresolution 2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Data Collection Configuration Non Cardiac Cardiac.
SPECT Image Acquisition Typically 2 cameraheads rotating around Projection images every3 6 degrees.
30 s projection 15minutes total Matrix 64 x 64 or 128 x2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Data Collection Angular Stops.
3 to 6 degrees is common a lesser number causes streaking a larger number does not improve image Step shoot or continuous acquisition which is better .
Step Shoot Characteristics Some loss of time Less Blur View number for 360 SPECT128 views 64 views.
43 views 32 views An image with 128 x 128 matrix Contains 128 projections Each projection has 128 data Equivalent to 128 slice CT.
i e 128 tomographic slices per2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Sinogram for one of many slices Physics in Nuclear Medicine Cherry Sorenson and Phelps Back Projection of Sinogram Data.
Leads to blurring in image streaks andstar like artifacts Physics in Nuclear Medicine Cherry Sorenson and Phelps Filtered Backprojection Suppress blurring through filtering the.
projections A high pass filter ramp filter can be usedto suppress blurring Filtered Back Projection of noiseless Physics in Nuclear Medicine Cherry Sorenson and Phelps.
Filter Types Physics in Nuclear Medicine Cherry Sorenson and Phelps Filter Types A Butterworth less B Butterworth morenoise more smooth noise less smooth .
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Applied filter is the product of User selected characterized filter Shepp Logan cut off freq Hann cut off freq .
Butterworth order slope critical freq 0 707 response Others Procedure for applying filter 1D projection of each view is converted to spatialfrequency using a Fourier transform.
Ramp filter with roll off is applied in spatial frequencyspace k space Filtered projection is recovered with inverse Fourier Back projections performed to reconstruct image Selection of Filters for SPECT.
Filters trade noise for resolution No standard way to optimize filter choice Patient to patient variation Physician preferences and or technologist Vendor recommendation.
Iterative Reconstruction IR Filtered Back Projection has some limits Various corrections needed Attenuation Compton Scatter.
Ordered Subsets ExpectationMaximization OSEM is a commoniterative reconstruction algorithm Iterative Reconstruction Slow compared to filtered back projection.
Commonly used for PET and SPECT and Image recon Iterativerecon is theFor OSEM iterations I .
and subsets S affectimage quality2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Iteration 1.
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Iteration 52015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Iteration 102015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR.
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Non reconstruction Noise Factors Collimator Matrix 64 x 64.
128 x128 Slice thickness Counts Administered Dose Time per stop Number of Stops.
SPECT Data Collection Whole Image iscollected for each 64 x 64 or 128 x 128 Each row makes a.
Multiple slices canbe added to reduce Attenuation Correction Like all radionuclide imagingthere is a problem due to.
attenuation Correction can be important forjudging the activity of lesions Attenuation correction Gamma rays traveling smaller paths through the.
patient nearer to camera have less attenuationcompared to those from deeper in patient for AC can be assumed or measured Chang assumed Measured CT new .
CT can be non diagnostic low power cone beam or fully diagnosticdepending on the scanner model2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Attenuation in SPECTI1 I0e a.
I0 I1e a attenuation corrected intensity Correct intensity I0 dependenton the depth at which originates need to know a 2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Chang s AC method.
Image first reconstructed without AC To obtain contour of body Contours of image used to estimateattenuating depth for each pixel assumedto be constant.
Attenuation correction AC determined foreach pixel x y for each projection Reconstructed image corrected pixel by Works well for area with approximatelyconstant attenuation like head abdomen but.
not for areas like chest thorax2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Chang s Method Assume uniform attenuation I0 I1e a attenuation corrected.
intensity m is 0 15 cm for Tc 99m for soft tissue In Chang s method m is often set to 0 12 cm to better account for Compton scatter Uniform phantom with evenly.
distributed 99mTcLow counts Changin center method2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR AC in SPECT CT.
Accurate realistic map obtained for eachprojection using CT values used in Chang s algorithm to correctpixel by pixel AC here is more realistic since is not.
assumed to be constant Current SPECT CT systems use this method2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Philips Astonish NM Recon Software The Astonish Ordered Subsets.
Expectation Maximization OSEM Compensation for the blurring effects ofthe collimator built into the reconstruction Resolution Recovery allows recovery ofsome of the original resolution.
Astonish uses the distance from thedetector to the object of interest recordedas a function of angle by the cameraduring acquisition and geometricproperties of the specific collimator.
Philips Astonish NM Recon Software Used on essentially all Philips NM SPECTimages at MCG Iterations 4 Subsets 16.
On BrightViews CT data used forattenuation correction except brains dueto EEG electrode artifacts Chang s AC invoked for brains On SkyLight and C Cam CT data not.
Common SPECT Problems Patient motion System Alignment Center of rotation Collimator issues Distance issues.
Loss of resolution with distance Center of Rotation SPECT assumes heads always look at aconstant central rotation point COR Spatial Alignment .
Image will have blurring and circular COR must be tested periodically for all SPECT of three point sources Generally done with system QC software COR correction.
SPECT image Incorrect CORof a uniform correctionphantom on a introducing a ringcamera with artifact degradingpoor COR spatial resolution.
correction2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR COR correction COR correction is used when reconstructingtomographic data to correct for minor.
misalignment between the center of the imageand the axis of rotation COR corrections are stored in a correctiontable and are applied automatically after a dataset has been acquired .
2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis PhD DABR Collimator Issues Collimators are not completely uniform A high count flood must be stored tocorrect for collimator non uniformities.
20 M for 5 for 128 x128 Patient Studies SPECT Advantages No overlapping structures 3 dimensional lesion locations.
Fusion with high resolution images CT MRI Disadvantages Time consuming motion Images are noisy.
COR correction is used when reconstructing tomographic data to correct for minor misalignment between the center of the image and the axis of rotation. COR corrections are stored in a correction table and are applied automatically after a data set has been acquired. 2015 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR

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