Lecture 1 Intro to Med Imaging

8/9/2019 Lecture 1 Intro to Med Imaging

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MEDICAL IMAGINGBMEN 420 – 500

MW 04:10PM-05:25PM ETB 1020

INSTRUCTOR: MARY PRESTON MCDOUGALL

5026 ETB

[email protected]

OBLIGATORY “FUNNY” INTRODUCTION

Possible Syllabus:

Your Syllabus:

• Office hours

• Prereqs

• Required text

• Grading and exam dates

• Email and distribution of papers


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COURSE OUTLINE

1. Signals and Systems

– Signals

– Systems

– Fourier Transform

– Sampling theory

2. Image Quality

– Contrast-to-noise ratio

– Signal-to-noise ration

– Image resolution

– Artifacts and distortion

3. Radiographic imaging

– Physics, instrumentation,

image formation

4. Nuclear Medicine imaging

– Physics, instrumentation,

image formation

5. Ultrasound imaging

- Physics, instrumentation,

image formation

6. MRI

- Physics, instrumentation,

image formation

INTRODUCTION - TERMS

• Imaging MODALITY = imaging technique, method, system

– Magnetic Resonance Imaging (MRI)

– Ultrasound

– Projection radiography (x-ray)

– Computed Tomography (CT) – Nuclear Medicine (PET, SPECT)

• Projection vs. Tomographic

• Static vs. Dynamic

• Functional vs. Anatomic or

Structural

“risk free”

“non-

invasive”


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INTRODUCTION

• Signal originates from

body’s physical parameters →physical measurements:

• ZĞŇĞĐƟǀŝƚǇ ї ƌĞƚƵƌŶŝŶŐ ĞĐŚŽĞƐ ;h Ϳ̂

• >ŝŶĞĂƌ ĂƩĞŶƵĂƟŽŶ ĐŽĞĸĐŝĞŶƚ їǆ-ray intensities (CT)

• Hydrogen proton density → radiofrequency waves (MRI)

• Four main [medical imaging] signals:

– X-ray transmission

– Gamma ray emission

– Ultrasound echoes

– Nuclear magnetic resonance induction

HISTORY OF MEDICAL IMAGING

First published medical image,

December 1895, Würtzburg, Germany

• Wilhelm Conrad Röntgen

• “a new kind of rays” exposed film evenwhen optically shielded

• X-ray used pre-surgically January,

1896

• Nobel Prize in Physics, 1901, for

discovery and use of x-rays


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• 1896: discovery of radioactivity. Initially used in

cancer therapy only.

• 1923: “Father of Nuclear Medicine”, George de

Hevesy, introduces ideas of using radioactive

TRACERS to study physiology

• 1952: the modern Anger scintillation camera was

developed by Hal Anger at UC Berkeley for nuclear

imaging.• 1952: Bloch and Purcell receive Nobel Prize for

discovery of phenomenon of nuclear magnetic

resonance.


• 1961: first use in medicine of nuclear imaging

• 1960’s: simple A-mode and B-mode ultrasound

scanning develops from WWII sonar technology

• 1971: Raymond Damadian publishes paper

suggesting use of NMR in medical imaging

• 1972: Godfrey Hounsfield produced first true CT

scanner for cross-sectional imaging with x-rays using

image reconstruction technique of Cormack

Early CT image


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• 1973: Paul Lauterbur published paper showing first

localized magnetic resonance images

• 1979: Hounsfield and Cormack share Nobel Prize in

Medicine

• 1991: Nobel Prize to Richard Ernst for work in

localizing NMR signal

• 2003: Nobel Prize to Paul Lauterbur and Peter

Mansfield for invention of MRI

Modern: PET/CT & PET/MR

MODALITIES: BASIC CHARACTERISTICS AND COMPARISON

• Projection radiography uses the fact that the body’s

tissues selectively attenuate x-ray intensity

• Routine diagnostic radiography

• Digital radiography

• Neuroradiology

• Mobile x-ray systems

• Angiography

• Computed tomography (CT) uses the fact that the

body’s tissues selectively attenuate

x-ray intensity

• Standard, single slice

• Helical

• Multislice


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• Nuclear Medicine images using radioactive sources

that emit radiation from within the body =>

*** a FUNCTIONAL imaging method ***

• Conventional radionuclide imaging, scintigraphy

• Single-photon emission computed tomography (SPECT)

• Positron emission tomography


• Ultrasound Imaging fires high frequency sound into

the obdy and receives the echoes retruning from

structures within the body.

• A-mode imaging

• B-mode imaging• M-mode imaging

• Doppler imaging


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• Magnetic Resonance Imaging (MRI) uses a

combination of a high-strength magnetic field and

radio waves to image properties of the proton

nucleus of the hydrogen atom.

• Standard MRI

• Echo-planar imaging (EPI)

• MR spectroscopic imaging

• Functional MRI (fMRI)

MODALITY CHARACTERISTICS AND COMPARISON

• Radiography

• CT scanning

• Nuclear medicine

• MRI

• Ultrasound

use electromagnetic energy

a small portion of the

spectrum is useful for

medical imaging

uses sound waves

1-20Hz

“reflection modality”

use

ionizing

radiation

“transmissionmodalities”

“emissionmodality”


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non-ionizing radiation(NIR)

wave model

ionizing radiation (IR)

particlemodel

naturally occurring sources


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Chest Abdomen Head

X-Ray/

CT

widely used

excellent

needs contrast

excellent

good for bone

bleeding, trauma

Ultrasound no, except for

heart

excellent poor

Nuclear extensive use inheart

Merge w/ CT PET

MR growing cardiac

applications

minor role standard

MODALITY CHARACTERISTICS AND COMPARISON - CLINICAL

Cardiovascular Skeletal / Muscular

X-Ray/

CT

Excellent, with catheter-injected

contrast

strong for skeletal system

Ultrasound real-time

non-invasive

cheap

but, poorer images

not used

Research in elastography

Nuclear functional information

of perfusion

functional - bone marrow

MR getting better

High resolution

Myocardium viability

excellent

MODALITY CHARACTERISTICS AND COMPARISON - CLINICAL


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Ultrasound: ~ $100K – $250K

CT: $400K – $1.5 million (helical scanner)

MR: $350K (knee) - 4.0 million (siting)

Service: Annual costs

Hospital must keep uptime

Staff: Scans performed by technologists

Hospital Income: Competitive issues

Significant investment and return

MODALITY CHARACTERISTICS AND COMPARISON - ECONOMICS

Radiologists look for specific patterns in medical images. It is

the job of the engineers and scientists who develop medical

imaging systems to produce images that are as accurate and

useful as possible.

SUMMARY

Modality Projection/

Tomographic

Anatomic/

Functional

Static/

Dynamic

Ionizing/

Non-

ionizing/

Other

Resolution Cost

Scintigraphy

Conventional

radionuclide

Projection Functional Static Ionizing Low Medium

SPECT Tomographic Functional Static Ionizing Low Medium-high

PET Tomographic F unctional Static Ionizing Medium Medium-high

Projection

Radiography

Projection Anatomic Either Ionizing High Low

CT Tomographic Anatomic Either Ionizing High Medium-high

Ultrasound Other/Direct

Anatomic Dynamic Other Low Low

MRI Tomographic usuallyAnatomic

Static,

becoming

dynamic

Non-

ionizing

High High


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WHAT MORE IS THERE?

“..if only there

existed giant

machines that could

look through human

skin…”

EXAMINE OUR UNIVERSE-

20 ORDERS OF MAGNITUDE


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20 ORDERS SMALLER

ENGINEERING AT THE NANO-SCALE.

• 20 orders of magnitude ineach way from our world isincomprehensible-

• However, we can image each

• Both directions are worthstudying- one we candirectly manipulate and use.

• Nano-science andengineering (dimensions <10-9) is one of the next greatchallenges.


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Symptom-based diagnosis

(In-Vitro Diagnostics, Imaging)

Recover or revisit

MEDICAL IMAGING IN CONTEXT: EVOLVING MEDICAL PRACTICE

“Here…

Try This”

Visit your doctor with illness

Symptom-based diagnosis

(In-Vitro Diagnostics, Imaging)

Treatment

Predict

Gene Assay

Molecular

Diagnostics

Pinpoint

Imaging

Molecular

Imaging

Prevent/Treat

Molecular

Therapeutics

Detect

Protein

In Vitro

(IVD)Imaging, IVD

Track and

Verify

The Future … Personalized Medicine

Molecular

Therapeutics

Molecular

Imaging Molecular

Diagnostics

Targeted

Chemistry

MEDICAL IMAGING IN CONTEXT: EVOLVING MEDICAL PRACTICE


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The inner life of the cell• Tools engineers have developed are allowing us to peerinside, and even manipulate the cell.

• The complexity is unimaginable, the challenges endless.

Lecture 1 Intro to Med Imaging

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