M.KUMARASAMY COLLEGE OF

ENGINEERING

WELCOME

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What do Physicists do in…

“REAL LIFE

Many work with doctors

in the field of

Medicine

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Doctors often need to look inside our

bodies without cutting them open….

Some you may have heard of…

X-rays…..NMR…..MRI scans

And new ones you may not have heard of yet….

PET scans…..MEG

are essential in the development of many scanning technologies

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Here is your chance

to…Find out the basics of how these

scans work

See how important electro magnetic

field in modern medicine.

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ELECTRO

MAGNETICWAVES

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X-

raysVery little ordinary

light can pass

through skin. It’s

either absorbed at

the surface or

reflected back..

To “see” inside we

need a kind of

“light” with more

energy…

Skin

Ordinary Light

X rays

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Taking “X rays”

The patient is

placed in

front of a

source of

X-rays.

X ray

Tube

A photo graphic

plate is placed

on the other

side of the

patient

Most of the

X rays pass

through the

patient’s

body…….

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X-rays are also partly absorbed by some

tissues in body this creates a more subtle

picture.

SOFT

TISSUE

bone

Soft tissue

Photographic

plate

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X-RAYS

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Advantage of X rays

X-rays are easy to produce

X-rays machines are relatively cheap

X-rays are used to diagnose broken

bones, dislocated joints etc..

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Disadvantage of X-rays

In large doses X rays can

harmful to health.

Imaging of soft tissues and

organs is not always very

detailed.

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MRIWhat do the letters stand

for?

M……….. Magnetic

R………… Resonance

I…………. Imaging

MRI scanners do not use X rays.

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With the patient safety check

complete the scan can

begin…The part of the body to be scanned is placed in the centre of the primary magnet

X

This field causes the Hydrogen nuclei in the

patients body to line up with the field2/15/2015 14

The patient is placed on a bed and then

moved into a large hollow tube.

The tube contains a very powerful

magnet….

Using an MRI

Scanner…

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It took physicists over 40 years to turn their

discovery of nuclear magnets into images of

the human body.

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View an MRI scan from any

angle..

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ADVANTAGES

Do not involve

exposure to

radiations.

Ability to image

without the use of

ionising radiations.

Scanning and

detection of

abnormalities in soft

tissues.2/15/2015 18

DISADVANTAGES

Very expensive (1 million )

While processing creates

so much of noise.

It is done in enclosed

space.

Less spatial resolution than

COMPUTED

TOMOGRAPHY.

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PET(positron emission tomography)

“snapshot” images are useful

but doctors sometimes need “real time”pictures of how parts of your body are

functioning…

e.g. How your heart is

functioning.

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PET SCANNERS LOOK LIKE CT

SCANNERS…

-NO X RAY

TUBE.

-The ring is

surrounded by

“Gamma Ray”

detectors

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PET scan patients are injected with a

specially created substance called a

“RADIOTRACER”….

Usually a “Radioactive” type

of glucose.

The radiotracer is a

source of positrons

which leads to the

production of gamma

rays…

INSIDE THE PATIENTS

BODY!

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The radiotracer concentrates itself

in certain tissue types…

This glucose type

radiotracer has

concentrated

itself in high

glucose using

cells like the

brain, kidneys

and cancer cells.

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PET ScansThe biggest cost

is in the

production of

RADIOTRACE

R

The hospital

needs to have

access to a

“CYCLOTRON

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ADVANTAGES

Used for diagnosis of

many diseases.

At small movement it

does not ruin the scan.

To show blood flow,

oxygen and glucose

metabolism in the

tissue.

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DISADVANTAGES

Scans works by

injecting a patient with

radionuclide.

Radioactivity decays

rapidly.

Images are of

substantially lower.

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MEG(magnetoencephalography)

It doesn’t put anything

into a patients body….

It just measures something that is

already there

No X rays/Strong Magnetic

Fields/Radio

waves/Radiotracers

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Your body is full of tiny electric

currents!

These tiny currents produce tiny magnetic

fields

MEG is able to measure some of these.2/15/201528

ADVANTAGES

Measure activity of the

brain extreme quickly.

Temporal specificity

Effective diagnostic tool

for evaluating brain

function.

Easy to use

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DISADVANTAGES

Very invasive

More expensive

Cannot detect activity of

the cell

Cannot be used with the

patients who are

claustrophobic.

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NMR(NUCLEAR MAGNETIC RESONANCE)

Used for magnetic resonance

imaging for medical diagnosis and

magnetic resonance microscopy in

research setting.

Biochemical information can also be

achieved from LIVING TISSUE.

EX: HUMAN BRAIN TUMOR

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NMR process

NMR scan the narrow table moves the patient through a tunnel like structure

create a magnetic field through which radio waves are sent , creating a 3-D image of the internal structure.

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NMR SCANNER

NMR SCANNER

also utilised

in low field NMR.

Its effectiveness can be

Improved byHYPERPOLARISATION

and using 2D,3D

Techniques.

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NMR HAHN ECHO DECAY

EXPERIMENT

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ADVANTAGES

Does not require contrast media,so no

anaphy lactic reaction.

Better accuracy in localisation of

etiology

No complications like

pancreatitis,bleeding etc..

Non invasive

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DISADVANTAGES

Imaging compared with other

modalities is intrinsic

insesitivity of the method.

Very expensive

Time consuming

Spectra take long time to

interpret.

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ELECTRO MAGNETIC BLOOD

FLOW METERWorks on the principle of

FARADAY’S LAW OF

ELECTRO MAGNETIC

INDUCTION’.

Used to measure the blood

flow

For this the diameter of

blood vessel is outlined by

the TRANSDUCER IN THE

RADIOGRAM2/15/2015 EMF 37

ELECTRO MAGNETIC BLOOD

FLOW METER

It is used during the

vascular surgery to

measure the quantity

of blood passing

through the vessel or

graft before during or

after surgery.

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VARIOUS METHODS USED FOR

ASSESSMENT

Observation and

palpation of pulses

Intra-arterial pressure

measurements with

careful attention to the

presence of

“GRADIENTS’

Arteriography

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ADVANTAGES

Measurement of flow and

volume of blood.

During arterial

reconstruction

Superior mesenteric artery

reconstruction

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DISADVANTAGES

Some times magnetic fields

are not uniform

Wall of flow tube is

conductive

Flow is axially non-

symmetrical

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THANK YOU

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QUERIES….?

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