Imaging With Electricity - Systems And Computer Engineering

Imaging with Electricity:Biomedical Engineering SeminarCarleton Univerity, Ottawa, ON, 22 Sep 2015Andy AdlerProfessor & Canada Research Chair in Biomedical EngineeringSystems and Computer Engineering, Carleton University, OttawaImaging with Electricity, Andy Adler, 2015/09/221 / 40

Lung ImagingImaging with Electricity, Andy Adler, 2015/09/222 / 40

Lung ImagingSource: Kirby et al,Radiology 261.1 (2011)Pre- and post-salbutamol3He MR images (red)registered to two centercoronal thoracic 1 H MRimages (gray scale) for fiverepresentative patients withCOPDS1, S2: stage II disease,S3, S4: stage III disease,S5: stage IV disease.Imaging with Electricity, Andy Adler, 2015/09/222 / 40

Imaging new clinical insightsImaging with Electricity, Andy Adler, 2015/09/223 / 40

Electrical Impedance Tomography10-day old healthybaby with EITelectrodesSource:eidors3d.sf.net/data contrib/ifneonate-spontaneousImaging with Electricity, Andy Adler, 2015/09/224 / 40

Electronics – Block DiagramImaging with Electricity, Andy Adler, 2015/09/225 / 40

Current PropagationHealthy Adult MaleCT slide at ionImaging with Electricity, Andy Adler, 2015/09/226 / 40

Current Propagation Healthy Adult MaleCT slide at ionImaging with Electricity, Andy Adler, 2015/09/226 / 40

Current PropagationI Healthy Adult MaleCT slide at ionImaging with Electricity, Andy Adler, 2015/09/226 / 40

Current PropagationI Healthy Adult MaleCT slide at ionImaging with Electricity, Andy Adler, 2015/09/226 / 40

Current PropagationI Healthy Adult MaleCT slide at ionImaging with Electricity, Andy Adler, 2015/09/22 6 / 40

Finite Element ModellingImaging with Electricity, Andy Adler, 2015/09/227 / 40

Finite Element ModellingSimulated VoltagesVoxel CurrentsImaging with Electricity, Andy Adler, 2015/09/228 / 40

Thorax PropagationI CT Slice withsimulated currentstreamlines andvoltageequipotentialsImaging with Electricity, Andy Adler, 2015/09/229 / 40

Thorax PropagationI CT Slice withsimulated currentstreamlines andvoltageequipotentials Imaging with Electricity, Andy Adler, 2015/09/22 9 / 40

Changing ConductivityI ' &%Heart receivesblood (diastole)and is moreconductive Imaging with Electricity, Andy Adler, 2015/09/22 10 / 40

Changing ConductivityI ' &%Heart receivesblood (diastole)and is moreconductive Imaging with Electricity, Andy Adler, 2015/09/22 11 / 40

Changing ConductivityImaging with Electricity, Andy Adler, 2015/09/2212 / 40

Application: BreathingChest images of tidal breathing in healthy adultImaging with Electricity, Andy Adler, 2015/09/2213 / 40

Application: HeartEIT Signal in ROI around heart (and ECG)Imaging with Electricity, Andy Adler, 2015/09/2214 / 40

Mechanical VentilationMechanical Ventilator with EIT monitorSource: Swisstom.comImaging with Electricity, Andy Adler, 2015/09/2215 / 40

Acute Respiratory Distress Syndrome (ARDS)' ' &%&%Imaging with Electricity, Andy Adler, 2015/09/2216 / 40

EIT LungStateABCDEImaging with Electricity, Andy Adler, 2015/09/22FG17 / 40

EIT LungStateABCDEFGOverdistensionACollapseImaging with Electricity, Andy Adler, 2015/09/2217 / 40

EIT LungStateABCDEFGOverdistensionABCollapseImaging with Electricity, Andy Adler, 2015/09/2217 / 40

EIT LungStateABCDEFGOverdistensionABCCollapseImaging with Electricity, Andy Adler, 2015/09/2217 / 40

EIT LungStateABCDEFGOverdistensionABCDCollapseImaging with Electricity, Andy Adler, 2015/09/2217 / 40

EIT LungStateABCDEFGOverdistensionABCDCollapseEImaging with Electricity, Andy Adler, 2015/09/2217 / 40

EIT g with Electricity, Andy Adler, 2015/09/2217 / 40

EIT ng with Electricity, Andy Adler, 2015/09/2217 / 40

EIT for Non-Invasive Blood PressurePulse transit time from heart to descending aorta using EITSource: Sola et al, Med. Biol. Eng. Comput., 2011Imaging with Electricity, Andy Adler, 2015/09/2218 / 40

Neonatal Breathing Preterm newbornshave complex,unstable physiology Ventilatory supportis often essential Currently, noadequate monitorsof breathing These data are froma lamb model ofneonatesSource: D. Tingay et al, In PressImaging with Electricity, Andy Adler, 2015/09/2219 / 40

EIT for Brain ImagingApplications: Epileptic foci Stroke (Ischaemicvs. Haemoragic) Fast Neural ImagingSource: Holder, www.ucl.ac.uk/medphys/research/eit/pubs/brain EIT overview.pdfImaging with Electricity, Andy Adler, 2015/09/2220 / 40

EIT for Cancer Imaging: Breast/Prostate Cancerous tissuehas differentelectrical properties Image tissue Image increasedvascularizationSource: Khan, Mahara, Halter et al, Conf. EIT,2014Imaging with Electricity, Andy Adler, 2015/09/2221 / 40

Non-medical applications Flow in pipes Mixing tanks Imaging metalic ores Hydro-geologyFigure shows resistivityin a cross-section of LaSoufrière de Guadaloupevolcano.Source: N. Lesparre et al, Conf. EIT, 2014Imaging with Electricity, Andy Adler, 2015/09/2222 / 40

Why is EIT hard?Imaging with Electricity, Andy Adler, 2015/09/2223 / 40

Inverse Problems . . . Plato’s caveImaging with Electricity, Andy Adler, 2015/09/2224 / 40

Plato’s cave . . . Shadows on the wallSource: jpgImaging with Electricity, Andy Adler, 2015/09/2225 / 40

Inverse ProblemsForward Problem: Forms ShadowsImaging with Electricity, Andy Adler, 2015/09/2226 / 40

Inverse ProblemsForward Problem: Forms ShadowsInverse Problem: Shadows FormsImaging with Electricity, Andy Adler, 2015/09/2226 / 40

Inverse ProblemsForward Problem: Forms ShadowsInverse Problem: Shadows Forms Ill-conditionedSensitivity to some movements is lowImaging with Electricity, Andy Adler, 2015/09/2226 / 40

Inverse ProblemsForward Problem: Forms ShadowsInverse Problem: Shadows Forms Ill-conditionedSensitivity to some movements is lowIll-posedSome movements don’t change shadowsImaging with Electricity, Andy Adler, 2015/09/2226 / 40

Inverse ProblemsForward Problem: Forms ShadowsInverse Problem: Shadows Forms Ill-conditionedSensitivity to some movements is lowIll-posedSome movements don’t change shadowsNoisyFlickering lightImaging with Electricity, Andy Adler, 2015/09/2226 / 40

Inverse ProblemsTechniques: to calculate stable & meaningful parameters in thepresence of inversion difficultiesExamples Image deblurring / restoration Medical imaging Geophyical imaging Model parameter fitting Reconstruction with incomplete/noisy dataImaging with Electricity, Andy Adler, 2015/09/2227 / 40

Forward Model (linearized)Reconstruction in Pictures Forward ProblemMeasurements(difference)Image(difference) noiseJacobianImaging with Electricity, Andy Adler, 2015/09/2228 / 40

Forward Model (linearized)Reconstruction in Pictures Forward ProblemMeasurements(difference)Image(difference) noiseRegularized linear inverse modelJacobian Linear Solution: Minimize norm2– PenaltyFunctionNorm weighted bymeasurement accuracyImaging with Electricity, Andy Adler, 2015/09/2228 / 40

Electrode errors: “Zero bad data”Idea #1: Reconstruction with Data Errors“Traditional”SolutionError HereReplaceWith zero–2 σ-21-2σ2-2σ3-2σ4Imaging with Electricity, Andy Adler, 2015/09/2229 / 40

Electrode errors: “Zero bad data”Idea #1: Reconstruction with Data Errors“Traditional”SolutionError HereReplaceWith zero–2 σ-21σElectrode Error: Regularizedimaging-22-2σ3-2σ4Error ModelSolutionError Here2–LowSNRhere ReplaceWith zeroσ-21-2σ2-2σ3-2σ4Imaging with Electricity, Andy Adler, 2015/09/2229 / 40

Electrode Error compensation Offline compensation using “jack-knife” approach (2005)ABEIT images in anaesthetised, ventilated dogA: uncompensated, B: compensated. Left: ventilation Centre:saline (right lung) Right: ventilation and saline Automatic detection (via reciprocity comparison) (2009) New work to speed online calculation & use data qualityImaging with Electricity, Andy Adler, 2015/09/2230 / 40

Imaging Electrode MovementIdea #2: Electrode movementSensitivity tosensormovement Jacobian now includesmeasurement changedue to movement noise“image” now includesx,y sensor movementImaging with Electricity, Andy Adler, 2015/09/2231 / 40

Imaging Electrode MovementIdea #2: Electrode movementSensitivity tosensormovement noiseJacobian now includesmeasurement change and “image”now includesPenalty:Imagemovementdue to movementx,y sensor ��of movementand imageco-varianceExpectedimageExpectedmovement1 -½“Unlikelyhood”of movement-½ 1 -½-½ 1 -½-½ 1 -½-½ 1 -½-½ 1Imaging with Electricity, Andy Adler, 2015/09/2231 / 40

Electrode movement compensationSource: Gómez-Laberge et al, Phys. Meas., 2006Imaging with Electricity, Andy Adler, 2015/09/2232 / 40

Idea #3: Data QualityImaging with Electricity, Andy Adler, 2015/09/2233 / 40

Idea #3: Data QualityDepth Sounder – with analog and digital guagesImaging with Electricity, Andy Adler, 2015/09/2233 / 40

What’s the problem?With strong priors and complex algorithms, algorithms give uspretty pictures, even when they are irrelevant.Question: how can we know when to trust a pretty picture? how can we know when the data are junk?Imaging with Electricity, Andy Adler, 2015/09/2234 / 40

Data Quality Measure: Concept Concept: High Quality Data are Consistent Idea: Use IP to predict each data point from all othersOriginald Remove id (i) Calculate error Solvem̂(i) Predictd̂ (i)(i) i di d̂iImaging with Electricity, Andy Adler, 2015/09/2235 / 40

Example: Data quality measuresR1AR2R3R4T1T2T3T4Patient 1Patient 7BNormalized data quality R1R2R3R4T1T2T3T4Protocol stepsClinical data and data quality metric for each stage of the protocol(R1–R4 — recruitment: PEEP , T1–T4 — titration: PEEP ).A: EIT images B: Calculated data quality.Imaging with Electricity, Andy Adler, 2015/09/2236 / 40

Perspectives Data analysis is hard powerful algorithms are useful we live in a world of big data complex systems fail in complex ways users like pretty picturesSo . . . the situation will get worseImaging with Electricity, Andy Adler, 2015/09/2237 / 40

Solutions?Imaging with Electricity, Andy Adler, 2015/09/2238 / 40

Solutions?Imaging with Electricity, Andy Adler, 2015/09/2238 / 40

Solutions? Imaging with Electricity, Andy Adler, 2015/09/2238 / 40

Solutions? Imaging with Electricity, Andy Adler, 2015/09/2238 / 40

Solutions? Thus, we needImaging with Electricity, Andy Adler, 2015/09/2238 / 40

Solutions? Thus, we need Open DataImaging with Electricity, Andy Adler, 2015/09/2238 / 40

Solutions? Thus, we need Open Data Open source analysisImaging with Electricity, Andy Adler, 2015/09/2238 / 40

For EIT . . .Imaging with Electricity, Andy Adler, 2015/09/2239 / 40

For EIT . . .Imaging with Electricity, Andy Adler, 2015/09/2239 / 40

For EIT . . .Imaging with Electricity, Andy Adler, 2015/09/2239 / 40

Thank you . . .Imaging with ElectricityAbstract: We use body surface electrical current stimulation andmeasurements to generate images of the internal electricalproperties. This principle is used in geophysics, process monitoring,and medical imaging. Currently, the most successful medicalapplication of electrical impedance tomography (EIT) is for imagingthe thorax, where the movement on conductivity contrasting air andblood can be imaged over time. The generation of EIT imagesrequires solving an inverse problem, which is ill-conditioned becauseof the diffuse nature of current propagation. The technology is thussensitive to electrode properties, data quality, and patient movement.To address these issues, several innovative strategies to analyze andinterpret these data have been developed. This talk will explain ourrecent progress in imaging the chest with EIT, and the imagegeneration and interpretation strategies that are required.Imaging with Electricity, Andy Adler, 2015/09/2240 / 40

Flow in pipes Mixing tanks Imaging metalic ores Hydro-geology Figure shows resistivity in a cross-section of La Soufriere de Guadaloupe volcano. Source: N. Lesparre et al, Conf. EIT, 2014 Imaging with Electricity, Andy Adler, 2015/09/2222 / 40