Magnetic Resonance Imaging: Single Coil Sensitivity Mapping and Correction using Spatial HarmonicsOutlineMotivationSlide 4TheoryMethodsSlide 7ResultsSlide 9Slide 10ConclusionReferencesMagnetic Resonance Imaging: Magnetic Resonance Imaging: Single Coil Sensitivity Mapping Single Coil Sensitivity Mapping and Correction using Spatial and Correction using Spatial HarmonicsHarmonicsEric Peterson and Ryan LipscombECE 53312/15/2006OutlineOutlineMotivationMotivationInhomogeneous coil sensitivityInhomogeneous coil sensitivityTheoryTheoryMethodsMethodsSpatial HarmonicsSpatial HarmonicsResultsResultsMotivationMotivationFlexible Torso Coil from ToshibaSensitivity profile of a circular phantom using two coils (top and left)MotivationMotivationDue to the Due to the inhomogeneous inhomogeneous and varying and varying sensitivity of the sensitivity of the vest coil the vest coil the images varyimages varyTheoryTheory),(),(*),(),( yxyxCyxMyxS),(),(*),(),( yxyxCyxMyxSImage degradation modelqpmkyimmexayxC )(),(Spatial Harmonics equationMethodsMethodsParallel imaging uses spatial harmonics Parallel imaging uses spatial harmonics to define the coil sensitivity mapto define the coil sensitivity mapUse low frequency spatial harmonics to Use low frequency spatial harmonics to define the sensitivity mapdefine the sensitivity mapFilter the image and the sensitivity mapFilter the image and the sensitivity mapInvert the sensitivity map and apply it Invert the sensitivity map and apply it to the imageto the imageKeyImage InputCropFind noise threshold with a user defined ROIFFTSelect number of harmonicsInvert and set minimum gain to 1Split noise and signal portions of the imageAttenuate inverse map using a user defined triangular filterMultiply the inverse map to the image to get the corrected imageNormalize the means of the original and corrected imagesOutput Corrected Image with NoiseSignal only portions of the original imageNoise only portions of the original imageIFFTOriginal imageSensitivity mapInverse sensitivity mapCorrected ImageCropResultsResultsCorrectedOriginalResultsResultsCorrectedOriginalResultsResults0.511.522.5x 10-16Absolute difference between ADC images before and after correctionConclusionConclusionThis method does a good job of This method does a good job of intensity normalizationintensity normalizationPreserves high frequency dataPreserves high frequency dataThe major limitation is due by high The major limitation is due by high frequency components of the lung frequency components of the lung such as tracheasuch as tracheaReferencesReferencesBydder M, Larkman DJ, Hajnal JV. Generalized SMASH Bydder M, Larkman DJ, Hajnal JV. Generalized SMASH imaging. Magn Reson Med 2002;47:160-170imaging. Magn Reson Med 2002;47:160-170Sodickson DK, Manning WJ. Simultaneous acquisition of Sodickson DK, Manning WJ. Simultaneous acquisition of spatial harmonics (SMASH): fast imaging with spatial harmonics (SMASH): fast imaging with radiofrequency coil arrays. Magn Reson Med 1997;38:591-radiofrequency coil arrays. Magn Reson Med 1997;38:591-603603Griswold MA, Jakob PM, Heidemann RM, Nittka M, Jellus Griswold MA, Jakob PM, Heidemann RM, Nittka M, Jellus V, Wang J, Kiefer B, Haase A. Generalized Autocalibrating V, Wang J, Kiefer B, Haase A. Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA). Magn Reson Med Partially Parallel Acquisitions (GRAPPA). Magn Reson Med 2002;47:1202-12102002;47:1202-1210Chen XJ, Moller HE, Chawla MS, Cofer GP, Driehuys B, Chen XJ, Moller HE, Chawla MS, Cofer GP, Driehuys B, Hedlund LW, Johnson GA. Spatially Resolved Hedlund LW, Johnson GA. Spatially Resolved Measurements of Hyperpolarized Gas Properties in the Measurements of Hyperpolarized Gas Properties in the Lung In Vivo. Part I: Diffusion Coefficient. Magn Reson Lung In Vivo. Part I: Diffusion Coefficient. Magn Reson Med 1999;42:721–728Med
View Full Document
Unlocking...