A number of MR imaging techniques are used to measure deformation in the heart including SPAtial Modulation of Magnetization (SPAMM), HARmonic Phase (HARP) and Displacement ENcoding using Stimulated Echoes (DENSE). In SPAMM, a line or grid tag pattern is created magnetically in the tissue and displacement is measured from this reference by tracking the tags. In HARP, position information is encoded into the phase of a filtered image and this is used to calculate displacement. In DENSE, displacements are directly encoded into the phase of the image

Cowan, B.R.

Hettiwatte, S.N.

Young, A.A.

English

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  MURDOCH RESEARCH REPOSITORY  http://researchrepository.murdoch.edu.au/14210/         Hettiwatte, S.N., Cowan, B.R. and Young, A.A. (2007) Generalized Analysis Framework for SPAMM, HARP and DENSE. In: Proceedings of the Society for Cardiovascular Magnetic Resonance 2007. Journal of Cardiovascular Magnetic Resonance, Vol. 9, No. 2, pp. 354-355.            It is posted here for your personal use. No further distribution is permitted.    354 SATURDAY POSTER ABSTRACTSRonald J. Beyers, MSEE, Yaqin Xu, MD, PhD, Stuart S. Berr,PhD, Frederick H. Epstein, PhD, Joel Linden, PhD, BrentA.French,PhD. UniversityofVirginia,Charlottesville,VA,USA.Introduction: CMR-basedstudieshavepreviouslydemonstratedthatpotentagonistsoftheadenosineA2AReceptor(A2AR)canhelppreserveleftventricular(LV)contractilefunctionearlyafterreperfused myocardial infarction (MI) in mice (1). However,the long term effects of such anti-inﬂammatory agents on theprogression of LV remodeling have not been explored, nor havethelong-termeffectsoftheseagentseverbeencomparedwiththemost effective clinical treatment regimen currently available –thecombinationofACE-inhibitionandbeta-adrenergicreceptorblockade (AI + BB).Purpose:ThepurposeofthisstudywastotestthehypothesisthatselectiveA2ARactivationcouldhelppreservecardiacstruc-tureandfunctionafterreperfusedMIsimilartothatprovidedbythe combination of AI+BB.Methods: All mice were studied by CMR before and at 1, 7,and 28 days after experimental MI. MI was induced by a 1 hocclusion of the LAD followed by reperfusion. Study groupswere composed of untreated C57Bl/6J wild-type mice (WT,n = 6), mice treated with ATL313 (a potent A2AR agonist,n = 5) and mice treated with the combination AI + BB (n =7). ATL313 was administered (10 ng/kg-min) starting 1h post-reperfusion until Day 14 post-MI using implanted Alzet micro-osmotic pumps (Durect Corp). The AI + BB combination ofCaptopril and Metoprolol (each at 35 ug/kg-min) was deliveredsimilarly starting 1 h post-reperfusion until Day 28. CMR stud-ies included localizer scanning, 6-8 short-axis slices of black-blood cine imaging to cover the entire heart, and at Day 1, 6–7gadolinium-enhanced,highﬂip-angle(60–90◦)short-axisslices.Gd-DTPAwasinfusedaftercineimagingthroughanindwellingIP line. All imaging was performed on a 4.7 T scanner with acustom-built Litz RF-coil (Doty Scientiﬁc). All images had aﬁeld-of-view of 2.56 cm, a matrix size of 128 × 128, and zero-ﬁlled pixel size of 0.1 × 0.1 mm2. Post acquisition analysis per-formed on Matlab yielded myocardial LV end-diastolic (ED),end-systolic (ES) volumes and ejection fraction (EF) from thecine images. Day 1 infarct size was measured as percent of LVmass from the gadolinium enhanced images.FIG. 1. Mid-ventricularshort-axisimages28dayspost-MIof(A)anuntreatedWT mouse, (B) a WT mouse treated with ATL-313, an (C) a WT mouse treatedwith AI+BB. Reduced cavity ize and circumferential extent of all thinning areevident in (B) and (C).FIG. 2. End diastolic volume (EDV), end systolic volume (ESV) and jectionfraction (EF) at baseline and during ﬁrst 28 days following MI. Selective activa-tion of the A2AR (ATL-313) reduces ESV and increases EF to a degree similarto that seen in Al+BB mice compared to untreated wild-ty;e (WT) mice. Note* indicates p<0.05 in comparison to WT.Results: Gadolinium-enhanced CMR demonstrated similarDay 1 infarct sizes in untreated (40 ± 4%), ATL313-treated(41 ± 3%) and AI+BB-treated mice (44 ± 5%) with p = NS byANOVA. Fig. 1 shows example Day 28 ED images illustratingtheeffectofdrugtreatments.Speciﬁcally,LVcavitydilationandcircumferential wall thinning are evident in the untreated mice(Fig. 1A). In contrast, preservation of cavity size and minimalwall-thinning in the anterior segment were seen in the ATL313-and AI + BB-treated groups (Figs. 1B&C). Fig. 2 shows theEDV, ESV and EF results from the present study. Both ATL313and AI+BB signiﬁcantly reduced both EDV and ESV at Days7 and 28 post-MI compared to WT. ATL313 improved EF onDays1and28post-MI,whereasAI+BBimprovedEFonDays7 and 28 post-MI. All comparisons reported here met p < 0.05by ANOVA.Conclusions: Using CMR, we have shown that selective ac-tivation of the A2AR reduces post-infarct LV remodeling toan extent similar to that provided by the combination of ACE-inhibition and beta-adrenergic receptor blockade. In addition,A2AR-stimulation preserves EF on Day 1 post-MI signiﬁcantlybetter than the combination of AI + BB, a property that mayprove beneﬁcial to survival in patients with large anterior MI.More generally, these results demonstrate the utility of serialCMRinmiceforevaluatingtheefﬁcacyofnewtherapiesagainstheartfailureandforcomparingnewtherapeuticapproacheswithconventional clinical paradigms.REFERENCE1. Toufektsian MC, Yang Z, Prasad KM, Overbergh L, Ramos SI, MathieuC, Linden J, and French BA. Stimulation of A2A-adenosine receptors af-ter myocardial infarction suppresses inﬂammatory activation and attenuatescontractile dysfunction in the remote left ventricle. AJP Heart & Circ Phys2006; 290:H1410–1418.508. GENERALIZED ANALYSIS FRAMEWORK FORSPAMM, HARP AND DENSESujeewa N. Hettiwatte, PhD,1 Brett R. Cowan, MBChB,2Alistair A. Young, PhD.31 Bioengineering Institute, Uni-versity of Auckland, Auckland, New Zealand, 2CentreSATURDAY POSTER ABSTRACTS 355for Advanced MRI, Faculty of Medical and Health Sci-ences, University of Auckland, Auckland, New Zealand,3Department of Anatomy with Radiology and Bioengi-neering Institute, University of Auckland, Auckland,New Zealand.Introduction: A number of MR imaging techniques are used tomeasure deformation in the heart including SPAtial Modulationof Magnetization (SPAMM), HARmonic Phase (HARP) andDisplacement ENcoding using Stimulated Echoes (DENSE). InSPAMM, a line or grid tag pattern is created magnetically inthe tissue and displacement is measured from this reference bytracking the tags. In HARP, position information is encodedinto the phase of a ﬁltered image and this is used to calculatedisplacement. In DENSE, displacements are directly encodedinto the phase of the image.Purpose: We show how all methods can be analyzed usinga single generalized framework. We test this framework by nu-merically creating SPAMM, HARP and DENSE images withknown deformations and comparing the results with the analyt-ical solution.Methods:Aknowndeformationwasdeﬁnedcomprisingaxialshear in a cylindrical annulus (1). SPAMM grid-tagged imagesweregeneratedwithatagspacingof7mmat45degand135degwith the ﬁrst ﬁve terms of a Fourier expansion used to approx-imate a square wave tag proﬁle. CSPAMM cosine modulatedimages and DENSE images were generated with displacementencoding in both the × and y directions. All images were gen-erated in DICOM format; SPAMM and CSPAMM at 256 × 256and DENSE at 128 × 128 resolution, all with FOV = 300 mm.Displacementimageswerecalculatedasfollows.InSPAMM,grid tagged images were interpolated to 512 × 512, and con-volved with a 2nd derivative of a Gaussian to obtain line tagsin each direction. Tags were detected by searching from eachTABLEErrors (mean ± sd) in displacement and Eulerian strainsAngular displacement(degrees)Radial displacement(mm)RadialstrainCircumferentialstrainShearstrainSPAMM −1.88 ± 0.46 −0.35 ± 0.29 0.00 ± 0.07 −0.01 ± 0.02 0.03 ± 0.03HARP 1.11 ± 0.77 0.06 ± 0.07 0.05 ± 0.05 0.00 ± 0.00 −0.04 ± 0.02DENSE 0.00 ± 0.01 0.00 ± 0.01 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00FIG. 1. Unwrapped displacement maps: Left to right: SPAMM (x and y), HARP(x and y) and DENSE (x and y).pixel along a line normal to the initial undeformed tags. Eachpixel value was equated to the distance from that pixel to thenearest tag centre in the tag direction to obtain a wrapped im-age of initial position X as a function of current position x.The displacement u(x) was then given by x-X(x). This dis-placement is only accurate at tag line centers; at other pointsdisplacement was obtained using a thin plate spline interpo-lation. In HARP, the Fourier transform of CSPAMM imagesgave spectral peaks, which were ﬁltered using a circular ﬁltercentered at the harmonic peak d = 1/7 cycles/mm with radius0.8 d and Gaussian roll off. The phase of the inverse Fouriertransform gave the X(x) map, and displacement u(x) was againgiven by x-X(x). In DENSE, the image phase gave displace-ment u(x) directly. The displacement maps from each methodwere unwrapped (2) and used to calculate angular and radialdisplacements and Eulerian strains, using the same pixel basedcalculation.Results:Theﬁgureshowstheunwrappeddisplacementmapsfrom each technique in the × and y directions. The mean andstandarddeviationofdifferenceswiththeanalyticsolutionwerecalculated for all pixels at least 5 mm from the inner or outeredge (Table).Conclusions: A generalized analysis framework demon-strates the similarity in displacement encoding methods.Simulated errors in displacements and strains were lowestin DENSE, intermediate in HARP and highest in SPAMM.SPAMM had the highest errors due to the simple pixel basedtrackingalgorithmandtheinterpolationschemeused.InHARP,the errors are largely due to the choice of ﬁlter parameters usedin Fourier domain.REFERENCES1. Radiology 1993; 188:101–108.2. J Opt Soc Am A 1994; 11:107–117.

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Generalized Analysis Framework for SPAMM, HARP and DENSE

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Generalized Analysis Framework for SPAMM, HARP and DENSE

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