Image reproduction +fMRI. Filtered Back Projection.

Slides:

Advertisements

Similar presentations

Class Business Class website is up Blackboard forum is up.

Advertisements

Fund BioImag : Echo formation and spatial encoding 1.What makes the magnetic resonance signal spatially dependent ? 2.How is the position of.

Fund BioImag : Echo formation and spatial encoding 1.What makes the magnetic resonance signal spatially dependent ? 2.How is the position of.

Principles of the MRI Signal Contrast Mechanisms MR Image Formation John VanMeter, Ph.D. Center for Functional and Molecular Imaging Georgetown University.

In Chan Song, Ph.D. Seoul National University Hospital

Richard Wise FMRI Director +44(0)

RF Pulse – generates a B 1 field that realigns the precessing spins in the low energy state In the case of a 90 o pulse the alignment is perpendicular.

Statistical Parametric Mapping

Fund BioImag : MRI contrast mechanisms 1.What is the mechanism of T 2 * weighted MRI ? BOLD fMRI 2.How are spin echoes generated ? 3.What are.

Chapter Four Image Enhancement in the Frequency Domain.

Introduction to Functional and Anatomical Brain MRI Research Dr. Henk Cremers Dr. Sarah Keedy 1.

Topics spatial encoding - part 2. Slice Selection  z y x 0 imaging plane    z gradient.

Principles of MRI: Image Formation

Magnetic Resonance Imaging Maurice Goldman Member Académie des sciences.

Image Reconstruction T , Biomedical Image Analysis Seminar Presentation Seppo Mattila & Mika Pollari.

Opportunity to Participate EEG studies of vision/hearing/decision making – takes about 2 hours Sign up at – Keep checking.

Principles of MRI. Some terms: –Nuclear Magnetic Resonance (NMR) quantum property of protons energy absorbed when precession frequency matches radio frequency.

Functional Magnetic Resonance Imaging Albert Parker February 26, 2002.

Principles of NMR Protons are like little magnets

fMRI introduction Michael Firbank

Opportunity to Participate

Structural and Functional Imaging Functional images tend to be lower resolution and fail to convey spatial information Pixels.

BMME 560 & BME 590I Medical Imaging: X-ray, CT, and Nuclear Methods Tomography Part 2.

Imaging PET Course Layout Class + ContentDateClass Physical Principles of PET I Physical principles of MRI II Imaging applications III.

Imaging PET Course Layout Class + ContentDateClass Physical Principles of PET I Physical principles of MRI II Imaging applications III.

Chapter 4 Image Enhancement in the Frequency Domain.

FMRI: Biological Basis and Experiment Design Lecture 5: non-BOLD MRI Equilibrium and excitation Relaxation rates Image contrast –TE –TR.

MRI, FBP and phase encoding. Spins Precession RF pulse.

Image reproduction. Slice selection FBP Filtered Back Projection.

Image Fourier Transform Faisal Farooq Q: How many signal processing engineers does it take to change a light bulb? A: Three. One to Fourier transform the.

Some Properties of the 2-D Fourier Transform Translation Distributivity and Scaling Rotation Periodicity and Conjugate Symmetry Separability Convolution.

SPM+fMRI. K space K Space Mechanism of BOLD Functional MRI Brain activity Oxygen consumptionCerebral blood flow Oxyhemoglobin Deoxyhemoglobin Magnetic.

Principles of MRI Some terms: – Nuclear Magnetic Resonance (NMR) quantum property of protons energy absorbed when precession frequency.

Chapter 4 Image Enhancement in the Frequency Domain.

Measuring Blood Oxygenation in the Brain. Functional Imaging Functional Imaging must provide a spatial depiction of some process that is at least indirectly.

Application of Digital Signal Processing in Computed tomography (CT)

Principles of MRI Physics and Engineering

Leo Lam © Signals and Systems EE235. Leo Lam © x squared equals 9 x squared plus 1 equals y Find value of y.

Outline 2-D Fourier transforms The sampling theorem Sampling Aliasing

Contrast Mechanism and Pulse Sequences Allen W. Song Brain Imaging and Analysis Center Duke University.

fMRI Methods Lecture2 – MRI Physics

Filtered Backprojection. Radon Transformation Radon transform in 2-D. Named after the Austrian mathematician Johann Radon RT is the integral transform.

Human Functional Brain Imaging Dr. Ryan C.N. D’Arcy NRC Institute for Biodiagnostics (Atlantic)

Contrast Mechanisms in MRI Introduction to Cardiovascular Engineering Michael Jay Schillaci, PhD Managing Director, Physicist Tuesday, September 16 th,

1 © 2010 Cengage Learning Engineering. All Rights Reserved. 1 Introduction to Digital Image Processing with MATLAB ® Asia Edition McAndrew ‧ Wang ‧ Tseng.

EE104: Lecture 5 Outline Review of Last Lecture Introduction to Fourier Transforms Fourier Transform from Fourier Series Fourier Transform Pair and Signal.

Contrast Mechanism and Pulse Sequences

BMI2 SS08 – Class 7 “functional MRI” Slide 1 Biomedical Imaging 2 Class 7 – Functional Magnetic Resonance Imaging (fMRI) Diffusion-Weighted Imaging (DWI)

Basic MRI Chapter 1 Lecture. Introduction MRI uses radio waves and a magnetic field to make images MRI uses radio waves and a magnetic field to make images.

Ultrasound Computed Tomography 何祚明陳彥甫 2002/06/12.

Fourier Transform.

MR Image Formation FMRI Graduate Course (NBIO 381, PSY 362)

MRI Physics: Spatial Encoding Anna Beaumont FRCR Part I Physics.

FMRI and MR Spectroscopy. BOLD BOLD=Blood Oxygenation Level Dependant contrast Neurons at work use oxygen (carried by hemoglobin) 1-5 s. delay, peaks.

MRI: Contrast Mechanisms and Pulse Sequences

Magnetic Resonance Learning Objectives

Outline Carrier design Embedding and extraction for single tile and Multi-tiles (improving the robustness) Parameter α selection and invisibility Moment.

Principles of MRI Physics and Engineering Allen W. Song Brain Imaging and Analysis Center Duke University.

Principles of MRI Physics and Engineering Allen W. Song Brain Imaging and Analysis Center Duke University.

BOLD functional MRI Magnetic properties of oxyhemoglobin and deoxyhemoglobin L. Pauling and C. Coryell, PNAS USA 22: (1936) BOLD effects in vivo.

resentations/E225/ Go to 51:47-1:06 mark listen for 9 minutes.

fMRI Basic Experimental Setup

FMRI data acquisition.

Outline 2-D Fourier transforms The sampling theorem Sampling Aliasing

Jody Culham Brain and Mind Institute Department of Psychology

MRI Physics in a Nutshell Christian Schwarzbauer

Magnetic Resonance Imaging: Physical Principles

An Optimal Design Method for MRI Teardrop Gradient Waveforms

Digital Image Processing

Biomedical Imaging: Magnetic Resonance Imaging - Basics

Presentation transcript:

Image reproduction +fMRI

Filtered Back Projection

Filtered backprojection Filter the measured projection data at different projection angles with a special function. Backproject the filtered projection data to form the reconstructed image. Filtering can be implemented in 2 ways, in the spatial domain, the filter operation is equivalent to to convolving the measured projection data using a special convolving function h(t) More efficient multiplication will be in the spatial frequency domain. FFT the measured projection data into the frequency domain: p(,  )=FT {p(t,  ) Multiply the the fourier transform projections with the special function. Inverse Fourier transform the product p ’ (,  ).

Phase Encoding Gradient FrequencyPhaseSlice Slice Plane Y or XX or YZXY Z or XX or ZYXZ Z or YY or ZXYZ

Phase encoding

K space

K Space

Partial K space reconstruction

Zero padding

Conjugate symmetry

Homodyne reconstruction

Mechanism of BOLD Functional MRI Brain activity Oxygen consumptionCerebral blood flow Oxyhemoglobin Deoxyhemoglobin Magnetic susceptibility T2* MRI signal intesity

Magnetic Properties of Oxyhemoglobin and Deoxyhemoglobin Deoxyhemoglobin: paramagnetic (  > 0) paramagnetic with respect to the surrounding tissue Oxyhemoglobin: diamagnetic (  < 0) isomagnetic with respect to the surrounding tissue

T 2 * Effect in fMRI excitation reception MR signal (S) action rest TE t

Time Series and Activation Maps Off On Scan Number Signal Intensity

Temporal resolution  Impulse-response function 2s 5s 12s

PCA_IMAGE: PCA of time  space: 1: exclude first frames 2: drift 3: long-range correlation or anatomical effect: remove by converting to % of brain 4: signal?