Medical+Application

7/31/2019 Medical+Application

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Medical application


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APPLICATION OF RADIONUCLIDE

Cardiac performance:

The nuclide Tc-99m ( 1 -

1.5mci) is tagged with

human serum albuminin vitro (bolus) and is

injected into an external

vein such as jugular.

This bolus travels to the

right side of the heart ,

is pumped through the

pulmonary systemdrains into the left

ventricle from which its

pumped into the aorta

and into the bodysarterial system and

venous return.


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A crystal detector (NAI)

ofrays is placed

behind a collimator ( a

hollow cylinder of lead)and this collimator

detector called a probe.

Refer the fig

As the radioactive bolus

enters the right heart

the outer detector

records a high level ofactivity.

The bolus is then

pumped into the

pulmonary circulatory

system and very little

activity is seen.


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When the bolus return

from pulmonary

circulation and enters

the left ventricle thebeat to beat

variation seen in the

count rate.


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Thallium-201 study

Thallium-201 injected

into the blood binds

particularly strongly to

heart muscle. Diagnosis of heart

disease depends on the

fact that only tissue that

receives sufficient blood

flow binds thallium-201.

When someoneexercises strenuously,

some part of the

persons heart tissue

may not receivesufficient blood because

of narrowed arteries.

These areas do not

bind thallium-201 and

show up on an image as

dark spots.


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Heart images


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THE GAMMA CAMERA

The instrument used in Nuclear Medicine for

the detection of gamma rays is known as the

Gamma camera.

The components making up the gamma

camera are the collimator, detector crystal,

photomultiplier tube array, position logic

circuits, and the data analysis computer.


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ANGER CAMERA

A pin-hole in lead was used toproject a gamma ray image ofthe source distribution in1953 by Hal Anger.

In the late1950's

, Angerreplaced the film and screenwith a single NaI crystal andPMT array. This formed thebasis for the "Anger Camera"which is now the standard

clinical nuclear imagingdevice.


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PICTURE OF GAMMA CAMERA


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Detector


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Nuclear medicine scintillation detector

system.


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Need for pulse height Analyzer

NaI


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Pulse Height Analyzer


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SCINTILLATION DETECTORS

In order to detect the gamma photon we

use scintillation detectors. A Thallium-activated Sodium Iodide [NaI(Tl)] detectorcrystal is generally used in Gamma cameras.

A gamma ray photon interacts with the

detector by means of the PhotoelectricEffect or Compton Scattering causing therelease of electrons which in turn interactwith the crystal lattice to produce light, in aprocess known as scintillation.


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PHOTO MULTIPLIER TUBE

The PMT is an

instrument that

detects and amplifies

the electrons thatare produced by the

photocathode.


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BONE SCANS

Bone scans are

typically performed

in order to assess

bone growth and tolook for bone

tumours.

The tumors are the

dark areas seen in

the picture.


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Not included in syllabus

(for information)


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WHAT IS SPECT?

SPECT is short for Single Photon EmissionComputed Tomography.

As its name suggests (single photonemission), gamma ray emissions are thesource of information, rather than X-ray

transmissions as used in conventionalComputed Tomography.


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PROCEDURE IN SPECT

Internal radiation is administered bymeans of a pharmaceutical which islabeled with a radioactive isotope.

The radioactive isotope decays, resultingin the emission of gamma rays.

These gamma rays give us a picture ofwhat's happening inside the patient'sbody.

The gamma camera can be used in planarimaging to acquire 2-dimensional images,

or in SPECT imaging to acquire 3-dimensional images.


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SPECT OF LUNG
http://en.wikipedia.org/wiki/Image:Lung_SPECT-CT_keosys_format_dicom.JPG


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DATA ANALYSIS COMPUTER

To deal with the incoming projection data and

to process it into a readable 3D image, a

processing computer is used.

The computer may use various different

methods to reconstruct an image, such as

filtered back projection or iterative

reconstruction.


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IMAGE RECONSTRUCTION

The aim of thereconstruction

process is to retrieve

the radiotracer

spacial distributionfrom the projection

data .


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SPECT APPLICATIONS

HEART IMAGING.

BRAIN IMAGING.

KIDNEY/RENAL IMAGING. BONE SCANS.


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HEART IMAGING

The following figure

is a myocardial scan

taken under stress

conditions. Regionsof the heart that are

not being perfused

will display as cooler

regions .


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BRAIN IMAGING

This figure is a

transverse SPECT

image of the brain.


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KIDNEY IMAGING

renal planar scan

using MAG3 tracer (a

glucose analog).


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IMAGES OF STROKES

Ellen, 63, was suddenlyparalyzed on the right side ofher body.

Unable to even speak, shewas in a panic and her familywas extremely concerned. Asdrastic as these symptomswere, two hours after theevent, her CAT scan was stillnormal.

Suspecting a stroke, theemergency room physicianordered a brain SPECT study

that showed a hole of activityin her left frontal lobe causedby a clot that had choked offthe blood supply to this partof the brain.

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