Introduction to Modern Medical Imaging Allen T. Newton, Ph.D. Institute of Imaging Science, Department of Radiology Vanderbilt University PAVE 2014.

Introduction to Modern Medical Imaging

Allen T. Newton, Ph.D.

Institute of Imaging Science, Department of Radiology

Vanderbilt University

PAVE 2014

Medical Imaging

• Look at a couple of key components of medical imaging

• Look at some examples from MRI, ultrasound, CT

• The goal is to better visualize structure or function in the living or non-living organism, animal or human

• Involves collaborations with mathematicians, physicists, engineers, chemists and biologists

• Work with physicians to meet their diagnostic and treatment evaluation needs

PhysicsPhysics ChemistryChemistry

BiologyBiology MedicineMedicine

EngineeringEngineering

MathMathComputerComputerScienceScience

Imaging Science

Medical Imaging

Radiologists (MD)

4 yrs of college

4 yrs of medical school

Technologists (RT)

2-4 yrs of college

2 yrs of technical school

Physicist/engineer (PhD)4 yrs of college5-7 yrs of graduate school

interpret

create

improve

http://www.andor.com/image_lib/lores/introduction

How do we make medical images?How do we make medical images?

The Major Imaging Modalities

• Magnetic Resonance Imaging (MRI)

• X-ray Imaging

• Computed Tomography (CT)

• Positron Emission Tomography (PET)

• Ultrasound (US)

The Major Imaging Modalities

• Magnetic Resonance Imaging (MRI)

• X-ray Imaging

• Computed Tomography (CT)

• Positron Emission Tomography (PET)

• Ultrasound (US)

The Major Imaging Modalities

• Magnetic Resonance Imaging (MRI)

• X-ray Imaging

• Computed Tomography (CT)

• Positron Emission Tomography (PET)

• Ultrasound (US)

The Major Imaging Modalities

• Magnetic Resonance Imaging (MRI)

• X-ray Imaging

• Computed Tomography (CT)

• Positron Emission Tomography (PET)

• Ultrasound (US)

So, you are playing soccer…• … you collide with another player, and collapse in

pain on the ground

• You have pretty intense pain in your lower left leg

• How bad is it and how do we find out?

So, you go to the Emergency Room…• … and the attending physician orders an X-ray of your injured leg• What are they looking for?• What will the X-ray show?

General Message:

What is the problem?

Can imaging solve the problem?

How?Image adapted from http://www.gentili.net/image.asp

The X-ray shows a bad break in your tibia

32x32, 7.5 mm2 64x64, 3.75 mm2

128x128, 1.87 mm2 256x256, 0.93 mm2

Spatial ResolutionSpatial Resolution

7T MRI, 0.6x0.6x1.0 mm3 resolution

Spatial resolutionSpatial resolution

ContrastContrast

A Magnetic Resonance Imaging Scanner

• Can generate 2D and 3D views in any plane

• Uses no ionizing radiation

• Extremely versatile modality

• Spatial resolution: humans~100, animals~25 microns

Magnetic Resonance imagingMagnetic Resonance imaging

Axial Coronal Sagittal

Magnetic Resonance imagingMagnetic Resonance imaging

MRI showing blood vessels in brain

Magnetic Resonance imagingMagnetic Resonance imaging

• Bright in coherent white matter

• Darker where1) Fibers diverge/cross, or2) No preferred orientation

Adam Anderson, Ph.D.

Assessing brain white matter tracks

• Orientation is color code by direction

Red = Right/Left Green = Anterior/Posterior Blue = Superior/Inferior

• Reveals structure within white matter

Magnetic Resonance imagingMagnetic Resonance imaging

Establishes connections between different brain regions

Finding white matter tracks

Adam Anderson, Ph.D.

Magnetic Resonance imagingMagnetic Resonance imaging

Some examples from cancer imaging

MRI in cancer imagingMRI in cancer imaging

anatomical MRI

time (min)0 2 4 6 8

SI (

arb

. un

its)

0.30

0.35

0.40

0.45

0.50

Signal Intensity time courses 3D rendering of tumor

X-rays in cancer imaging, 1/2X-rays in cancer imaging, 1/2

Mrs. Röntgen's hand, the first X-ray picture of the human body ever taken

Mammogram displaying calcification, increased density

X-rays in cancer imaging, 2/2X-rays in cancer imaging, 2/2• Standard radiography yields a 2-D projection of a 3D object, whereas CT allows for true 3-D image acquisition

• CT acquires a series of projections from many angles around the subject; each set of projections is then reconstructed via a “backprojection” algorithm

• Developed by Sir Godfrey Houndsfield, won 1972 Nobel Prize in Medicine/Physiology

• Spatial resolution: humans~200 microns, animals~35 micron

Munden, et al, Radiology, 2005; 237:803-18www.radiologyinfo.org/

PET in cancer imaging, 1/2PET in cancer imaging, 1/2

• Images generated using very similar computations as in CT

• Spatial resolution: humans and animals ~2 mm

• Some radioactive isotopes (18F, 15O, etc) emit positrons:

• Such elements can be incorporated into metabolically relevant compounds

• Emitted positron encounters electron, they annihilate leaving 2 photons traveling in opposite directions which are measured by ring of detectors

1

A AX Q e

Z Z

• Most common PET tracer is FDG (flourodeoxyglucose), a glucose analog

18FDG

(blood)

18FDG

(tissue)

18FDG-6-PO4

(cells)X

www.breastcancer.org

Dominique Delbeke

CT PET CT/PET

PET in cancer imaging, 2/2PET in cancer imaging, 2/2

Today: Overview

Tuesday: X-Ray & Computed Tomography (CT)

Wednesday: Ultrasound, SPECT, PET

Thursday: MRI

Friday: fMRI lab !!!!!!

This week