Download Radionuclide Imaging in Oral and Maxillofacial Diagnosis

Radionuclide Imaging
in Oral and Maxillofacial
Diagnosis
Introduction
Henri Bequerel (1896)
Marie Curie (1898 )
Introduction

Nuclear radiology is a sub-specialty
of radiology in which radioisotopes
are introduced into the body for the
purpose of imaging, evaluating organ
function, or localizing disease or
tumors.
Introduction

Radionuclide imaging is the technique
of producing diagnostic images by
analyzing the radiation emitted from a
patient who has previously been given
radioactive medications
Introduction

Nuclear medicine differs from most
other imaging modalities in that the
tests primarily show the physiological
function.
Nuclear Imaging
Basic Principle

In diagnosis, radioactive substances
are administered to patients and the
radiation emitted is measured. The
majority of these diagnostic tests
involve the formation of an image
using a gamma camera.
After the radioactive tracer
material is administered. The
patient lies very still on a table
while a special camera
detects gamma radiation.
Which is transmitted to
computer . The physician
studies the computerized
images to assess how well an
organ is functioning.
Essential Requirements

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The radiopharmaceutical
The radiation detection system
The analyzing system
The display and recording system
Radiopharmaceuticals

They are radioactive compounds.
when these agents are injected I.V.
into the patients, they are up taken by
the target tissues, accumulate in
them, then detected and imaged by
external detectors. And imaging
systems.
Radiopharmaceuticals
Radiopharmaceuticals
Natural
Artificial
Radionuclide Production
They are produced by :
 Generators

Cyclotrons

Nuclear reactors
Radionuclide (label)

All radiopharmaceuticals include in
their molecule structure a
radionuclide (label) which:


Enables their movement within the body
to be traced
Physiological function to be assessed.
Choice of radionuclide

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

Able to combine to form a wide range
of chemical compounds
Have a specific activity
Give suitable type of emission
Have a suitable radioactive decay
rate

Today, technetium 99mTc is the most
widely used imaging isotope in
nuclear medicine!!
Technetium

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Chemically versatile
Conveniently available
Emits only gamma photons ( 140 ke V)
Decay rate T1/2= 6 hours
Obtaining Technetium



Mo-99 is obtained from the nuclear reactor
as a fission by-product or produced from
Mo-98, a naturally occurring metal, by
neutron flux exposure.
Tc-99m is generated at the site of its use
from its parent radionuclide (Mo-99) by a
chemical process called solvent extraction
method.
The basic Tc-99m compound obtained from
this method is sodium pertechnetate
(NaTcO).
Technetium Generator
Essential Requirements




The radiopharmaceutical
The radiation detection system
The analyzing system
The display and recording system
Gamma Camera
Gamma Camera

A gamma camera is an imaging
device, most commonly used as a
medical imaging device in nuclear
medicine. It produces images of the
distribution of gamma ray emitting
radionuclides.
The gamma camera

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
Detector
Collimator
Photomultiplier tubes (PMT)
Preamplifier
Amplifiers
Pulsed-height analyzer (PHA)
An X-Y positioning circuit
Display or recoding device
Prevents
scattered
radiation
discards
they determine the
scatter photons
location of each
scintillation
as it the crystal
protects
occurs in the
crystal.
and
prevents the
detection of radiation
detects the
from
outside the
fluorescent
flashes
collimator field of
and converts
Sodium
iodide with
view.
scintillations
into weak
thallium doping in a
signals
light-sealed housing. It
converts photon
energy into light
amplify signals
from the PMT
The analyzing system
The purpose of the analyzing system
is twofold:
 Position analysis:


The precise position in the scintillation
crystal is computed
Signal strength analysis:

detected with (PHA)
Single Photon Emission
Computed Tomography
(SPECT)
Single Photon Emission Computed
Tomography (SPECT)


SPECT studies entail:
acquiring rotating delayed static images,
generally sixty-four projections over 360º
followed by computer reconstruction to
provide three dimensional multiplanar
slices in the axial, coronal, and sagittal
planes, relative to the patient’s body.
Single Photon Emission Computed
Tomography (SPECT)

Use of a gamma camera with the
capacity to rotate 360 degrees about
the patient


multiple detectors
single moving detector
Single Photon Emission Computed
Tomography (SPECT)
Because of the complex threedimensional anatomy with extensive
overlap of bony structures, It may be
difficult to evaluate with planar bone
scan images.
Single Photon Emission Computed
Tomography (SPECT)

SPECT bone scanning offers both
enhanced:
image contrast
 resolution
 more accurate localization of active disease as
it provides 3D information
allowing the interpreters to visualize in
transaxial, coronal, and sagittal slices,
structures that would overlap on planar
views.

Single Photon Emission Computed
Tomography (SPECT)

The SPECT technique:
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easier to perform
better reproducibility
Gives better localization of the condyles
Better sensitivity
More time and cost efficient
Salivary gland scan
Salivary gland scan
Definition
 A salivary gland scan is a nuclear
medicine test that examines the
uptake and secretion in the salivary
glands of a radioactively labeled
marker substance. The pattern of
uptake and secretion shows if these
glands are functioning normally.
Scintigraphy (radioisotope imaging)
It provides a functional
study of the salivary
glands, taking
advantage of the
selective concentration
of specific
radiopharmaceuticals
in the gland.
Scintigraphy (radioisotope imaging)
It depends on the selective conc. Of
99mTc in the gland and then its
excretion (the dye appears after
injection and reaches max. conc.
Within 30 mints).
Salivary gland scan
Purpose
 Evaluation of functional status of
salivary glands

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Vasculatrity
Duct function
Patency of larger ducts
Detection and evaluation of mass
lesions
Proprative localization of tumors
Scintigraphy (cont.)
Advantages:
Disadvantages:
 Allow bilateral
 Lacks specificity
comparison.of the 4
 radiation dose
glands in one image.
 Demonstrates little
 Can be performed in
morphology
acute infection or gland
which can not be
cannulated.
 Computer analysis of the
results are possible.
Salivary gland scan

The patient is positioned under a
gamma scintillation camera that
detects radiation. The patient then is
injected with a low-level radioactive
marker, usually technetium-99m or
technetium pertechnetate.
Salivary gland scan

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Immediately after the injection,
imaging begins.
After several images, the patient is
given lemon drop candies to suck on,
which stimulate the salivary glands.
Another set of images is made for
comparison purposes.

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Normal results
Normally functioning
salivary glands take up
the
radiopharmaceutical
then secrete it when
stimulated by the
lemon drops.

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Abnormal results
Abnormally functioning
salivary glands fail to
exhibit a normal uptake
and secretion pattern.
Scintigraphy (radioisotope imaging)
Saliva excreated in
the mouth
Parotid
Subman.
Thyroid
0-5 min
6-15 min
*
16-20 min
21-25 min
*=Acid stimulation at 15 min.
Subman.
Parotid
*
*
Scintigraphy (radioisotope imaging)
Bone Scanning
Bone Scanning

Definition
A bone scan is a diagnostic
procedure used to evaluate
abnormalities involving bones and
joints. A radioactive substance is
injected intravenously, and the image
of its distribution in the skeletal
system is analyzed to detect certain
diseases or conditions.
Bone Scanning
Bone is an extraordinarily dynamic
tissue. Constant turnover in response
to metabolic or mechanical demands
results in a steady state between new
bone formation and resorption.
Bone-imaging techniques
there are a number of ways to
perform a bone scan study. The
method chosen is typically influenced
by the clinical diagnosis to be
evaluated.

Bone-imaging techniques

Bone-imaging techniques include,
basically:
standard bone scan
 three-phase bone scan
 single photon emission computed
tomography (SPECT)

Standard bone scans involve
the acquisition of static images three
hours after tracer administration.
 Delayed static images may be useful
in the evaluation of benign conditions,
such as condylar hyperplasia.
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Three-phase study
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Three-phase study comprises
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flow assessment,
blood pool image,
delayed static views acquisition.
Three-phase study
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Three-phase study comprises
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flow assessment,
blood pool image,
delayed static views acquisition.
Three-phase study
The dynamic flow study requires rapid sequential
images for sixty seconds during the intravenous
administration of the radiotracer.

This is followed by a blood pool image reflecting
tissue hyperemia and is acquired immediately after the
flow study.

Three hours after radiotracer administration,
the bony uptake of technetium-99m labeled
diphosphonates is maximal, and a significant
proportion of the unbound tracer will have been
excreted by the kidneys. Therefore, the final delayed
staticimages are acquired at this time.
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Three-phase study
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Three-phase examinations are
frequently performed to evaluate:
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trauma
inflammatory disease,
primary bone tumors.

Normal results
The normal appearance of the scan
will vary according to the patient's
age. In general, a uniform
concentration of radionuclide uptake
is present in all bones in a normal
scan.
Abnormal results
Bone scanning
Hot spots
uptake
Cold spots
uptake
Bone Scanning
Scintigraphically, areas of increased
bone metabolism are evidenced and
appear as areas of increased
radiotracer uptake, namely “hot
spots.”
Bone Scanning
Decreased uptake is associated with
metabolically inactive bone, lack of
osteogenesis, or an absent vascular
supply.where there is diminished or
absent uptake, are called
“cold spots.”
Advantages of bone scan

In many clinical conditions, bone
scintigraphy will demonstrate
abnormalities long before the
radiographs.
Conventional radiologic
techniques

demonstrate bony
changes when there has
been an alteration of 30
to 50 % of the bone
mineral content

Dependes on differential
absorption
Bone scans

Has the ability to show
reactive modifications in
osteoblastic activity
that would not appear on
radiographic images,
but do not show
morphologic changes

positive if there is,
approximately, a 10 %
increase in the
osteoblastic activity
above normal
Bone Scanning
Bone scintigraphy has the potential to provide
valuable information concerning the diagnosis
and follow-up of several oral conditions such
as:
 primary or metastatic malignancies,
 benignneoplasms,
 cystic lesions,
 inflammatory and infectious processes,
 metabolic diseases,
 fibro-osseous dysplasias,
 hyperplasias,
 bone graft viability
Primary and Metastatic
Malignancies
The superior sensitivity of bone scintigraphy
in providing valuable information for preoperative
assessment of the malignant lesions’ extent has
been reported by many authors.

The most frequently encountered scintigraphic
pattern in malignant bone lesions is that of one or
multiple randomly distributed foci of intensely
increased radiotracer uptake, the so-called “hot spots”

Inflammatory and Infectious
Processes

Inflammation represents a dynamic process
that takes place in the connective tissue as
a reaction to intrinsic and/or extrinsic
agents.
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Accordingly, some oral conditions such as
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osteomyelitis,
traumatic injuries
osteoarthritis,
periapical lesions,
periodontal disease
play an important role in bone metabolism
and result in a positive bone scan image.
Inflammatory and Infectious
Processes
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The usefulness of the bone scan as a
diagnostic aid for inflammatory responses
of the temporomandibular joints (TMJ) is
somewhat controversial.
However, attempts have been made to
improve the evaluation of the metabolic and
physiological status of TMJ bony structures.
In fact, bone scans may demonstrate
inflammatory reactions that take place in
TMJ bony structures,
Inflammatory and Infectious
Processes
Inflammatory and Infectious
Processes
Fibro-Osseous Dysplasias

Fibrous dysplasias of the jaw are believed
to be benign, self-limiting, but nonencapsulated, lesions occurring mainly in
young subjects.

Histologically, they are characterized by the
replacement of normal bone by a cellular
fibro-osseous tissue containing
islands or trabeculae of metaplastic bone.
Fibro-Osseous Dysplasias
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Radiographs are usually adequate for
the diagnosis
however, bone scintigraphy is often
useful to establish the extent and
activity of maxillofacial lesions.
Fibro-Osseous Dysplasias
Bone Graft Viability

Bone scintigraphy provides a means of
predicting graft failure before radiographic
or clinical changes become apparent and,
thus, helping to avoid a loss of surrounding
bone from graft necrosis or infection.

useful in reconstruction of the jaw that
usuallyinvolves a vascularized bone
autograft, becauseclinical monitoring of the
transplanted bone is difficult
In Conclusion
Conclusion
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Radionuclide imaging has its
advantages and disadvantages

Morphologic and physiologic imaging
modalities,in combination, should
support each other in offering
valuable information diagnosis
Thank You