BMI2 SS07 – Class 1 “Introduction” Slide 1

Biomedical Imaging 2Biomedical Imaging 2

Class 1 – Introduction

01/23/07

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Course instructorCourse instructor

Dr. Harry L. GraberResearch Assistant Professor of Pathology / SUNY Downstate Medical Center / Room BSB 4-132, (718) 270-1286 / harry.graber@downstate.edu

A.B., Chemistry 1983, Washington University, St. Louis, MO

Ph.D., Physiology and Biophysics 1998, SUNY Health Science Center, Brooklyn, NY

Postdoctoral Fellow 1998, SUNY Downstate Medical Center

Res. Asst. Professor 2001, SUNY Downstate Medical Center

Research Focus: Optical Tomography - Image Reconstruction and Signal Analysis

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Lecture hours / locations, creditsLecture hours / locations, credits

• Classes

– Location: SUNY DMC HSEB 6A (except for 4/24/07, when it’s 6B)

– Hours: Tuesday, 5:30 pm to 8:30 pm

• Credits

– Classroom Participation: 15% – Homework: 20% – Exam1: 30% – Exam2: 35%

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Course materialsCourse materials

• No specific textbook

• Topic-specific readings (research papers, review papers, scientific magazine articles, internet pages) will be provided as needed

• Lecture notes and copies of assigned readings will be posted for download at http://OTG.downstate.edu/download.htm

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What is This Course About?What is This Course About?

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Imaging Modalities Covered in BMI1Imaging Modalities Covered in BMI1

• X-ray Projection Radiography

• X-ray Computed Tomography

• Nuclear Imaging

– Planar Scintigraphy

– Positron Emission Tomography

– Single Photon Emission Computed Tomography

• Ultrasound

• Magnetic Resonance Imaging

– Structural MRI (anatomy)

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Imaging Modalities Covered in BMI1Imaging Modalities Covered in BMI1

• In brief, structural imaging (SI) techniques

– With one significant exception

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Imaging Modalities Covered in BMI2Imaging Modalities Covered in BMI2

• Functional imaging (FI) methods

– Diffuse Optical Tomography

– Optical Coherence Tomography

– Functional MRI (fMRI)

– Electroencephalographic Imaging

– Magnetoencephalography

– (Combined, or multi-mode, imaging)

• But what does “functional” mean?

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Meaning of “functional” is context-specificMeaning of “functional” is context-specific

• Always involves examination of what tissue is doing– But how this examination is carried out is different for different

methods– In some cases, functional imaging just means producing as

many structural images as you can, as fast as you can• Example: functional x-ray CT

– Same goes for some kinds of functional ultrasound• What about MRI?

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Varieties of fMRIVarieties of fMRI

• Diffusion-weighted Imaging• Perfusion Imaging

– Contrast-agent-based– Magnetic Resonance Angiography / Venography

• Saturation-based• Bipolar-gradient-based

– Arterial Spin Labeling• Diffusion Tensor Imaging• Magnetic Susceptibility Imaging

– Contrast-agent-based– Blood Oxygen Level Dependent

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Some Modalities Are Inherently FunctionalSome Modalities Are Inherently Functional

• A: Abdominal x-ray CT image (structural/anatomical)• B: PET image of same tissue section (functional)• C: Co-registered x-ray CT and PET images

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FI Usually Is More “Indirect” than SIFI Usually Is More “Indirect” than SI

• Direct imaging = (essentially) no math needed– Laws of physics do the work

– e.g., Project an image onto a piece of film with a lens

• Indirect imaging = lots of math required– Computers used to process the measurement data and

reconstruct images

• “More indirect” means that additional, post-reconstruction operations are needed– Usually involves some type of comparison among images

from data collected at different times

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Instructional EmphasisInstructional Emphasis

• Image contrast mechanisms– How is energy interacting with matter (i.e., tissue)– What is the image a picture of?

• Biological/clinical motivation– Why do we care about the parameter(s) in the image?– How is having this image going to help us?

• How will it affect the treatment our patient is getting?

• Data analysis “from soup to nuts”– Pre-processing operations– Image reconstruction– Post-processing operations– “Post-post-” processing operations

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Tentative SyllabusTentative Syllabus1) 01/23 Introduction; diffuse optical tomography (DOT)2) 01/30 DOT3) 02/06 Image post-processing & time-series analysis, Pt. 14) 02/13 Optical coherence tomography (OCT)5) 02/20 fMRI – diffusion-weighted, perfusion6) 02/27 fMRI – perfusion7) 03/06 Exam18) 03/13 fMRI – BOLD9) 03/20 Image post-processing & time-series analysis, Pt. 210) 03/27 fMRI – diffusion-tensor imaging11) 04/10 EEG/MEG principles12) 04/17 EEG imaging13) 04/24 MEG imaging14) 05/01 DOT’s “relatives”: fluorescence OT, bioluminescence OT,

correlation tomography, optoacoustic tomography15) 05/08 Exam216) 05/15 Wrap-up

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Diffuse Optical tomography (DOT)Diffuse Optical tomography (DOT)

• Year discovered: ~1988

• Form of radiation: Near-infrared light (non-ionizing)

• Energy / wavelength of radiation: ~1 eV / 600–1000 nm

• Imaging principle: Interaction (absorption, elastic scattering) of light w/ tissue

• Imaging volume: ~103 cm3

• Resolution: Low (~1cm)

• Applications: Perfusion, functional imaging

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DOT and CT: Superficial Similarities, Essential DifferencesDOT and CT: Superficial Similarities, Essential Differences

• Generation: x-ray tube• Detection: Detector arrays (ion.-chambers,

scint. + photodiode)• Computer reconstruction of 2D slices/ 3D

volumetric images

Source

Detector

Object

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Principles of DOTPrinciples of DOT

• Scattering dominated• Limited penetration depth (~cm), low

res. (mm-cm)• Economic, functional (hemodynamics)

Clear medium Scattering medium

screen / detector screen / detectorlight source

obstacle (absorber) obstacle (absorber)

light source

light source detector

SD

SD

DD

D

Hb

HbO2

400 500 600 700 800 900 1000

Wavelength [nm]

103

104

105

106

102Mol

ar e

xtin

ctio

n co

eff.

[cm

-1 M

-1]

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DOT InstrumentationDOT Instrumentation

Scalp

Bone

Cortex

CSF

2-3 cm

Source / Detector 1

Detector 2

Detector 3

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DOT ApplicationsDOT Applications

SPECTBrain

Arm

Breast

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Electromagnetic spectrumElectromagnetic spectrum