This document provides an overview of nuclear imaging techniques. It defines nuclear imaging as a method of producing images by detecting radiation from different parts of the body after administering a radioactive tracer. The key differences from other imaging techniques are that nuclear imaging assesses organ function rather than anatomy. Common nuclear imaging procedures described include bone scans to detect bone disorders, salivary gland scans, and the use of radioisotopes like technetium-99m. The document also explains the principles, equipment, and applications of single photon emission computed tomography and positron emission tomography.

1. SUBMITTED BY:
Rupal Patle
BDS IV Year
Peoples Dental Academy

2. INTRODUCTION
 DEFINITION: Nuclear imaging is a method of producing
images by detecting radiation from different parts of the body
after a radioactive tracer material is administered.
 The images are recorded on computer and on film.
 The nuclear imaging physician interprets the images to make a
diagnosis.
 Radioactive tracers used in nuclear medicine are, in most
cases, injected into a vein.

3. Nuclear imaging equipment

4. DIFFERENCE FROM OTHER
RADIOLOGIC TECHNIQUES
 Nuclear imaging assesses  how organs function (FUNCTIONAL IMAGING).
 Whereas other imaging methods Eg. Film radiography, CT, MRI, Diagnostic
ultrasonography assess  anatomy, or how the organs look (MORPHOLOGIC
IMAGING).
 In some human diseases (bone disorders eg. Condylar hyperplasia) abnormal
biochemical process occur prior to the anatomic change. In such diseases, such
abnormal biochemical changes can be assessed with the help of nuclear imaging
technique.
 It would not be wrong to call Nuclear Medicine as "Radiology” done inside out" or
"Internal Radiology" because it records radiation emitting from within the body rather
than radiation that is generated by external sources like Xrays.
 This technique allows measurement of tissue function and provides an early marker
of disease through measurement of biochemical change.

5. PRINCIPLE OF NUCLEAR IMAGING TECHNIQUE
 THE STEPWISE PROCEDURE OF
NUCLEAR IMAGING:
Radionuclides are administered via vein or
mouth
They distribute in the body according to
their affinity for particular tissues so
called target tissues.
Radionuclides emit gamma radiations.
Detected by γ-scintillation camera
Which forms images showing location of
radionuclides in the body.

6. MAIN INDICATIONS OF NUCLEAR IMAGING
 Nuclear imaging technique is used for assessing function
of:
- Salivary gland as salivary scans
- Brain
- Thyroids
- Heart
- Lungs
- Gastro-intestinal system
 It is also used for diagnosis of:
- Metastatic diseases
- Bone tumors as bone scans

7. RADIOISOTOPES AND RADIOACTIVITY
 RADIOACTIVITY: Spontaneous emission of radiation, from unstable
atomic nuclei.
Or
It is the process by which an atomic nucleus of an unstable atom loses energy by
emitting ionizing particles (ionizing radiation).
 RADIOISOTOPES: Radioisotopes are isotopes with unstable nuclei which
undergo radioactive disintegration.
 This disintegration is often accompanied by emission of radioactive particles or
radiation. The important emissions include:
- Alpha particles
- Beta- (electron) particles
- Beta+ (positron) particles
- Gamma radiation.

8. The main properties & characteristics of these
emissions are summarized in table given below:
PROPERTY ALPHA BETA- PARTICLES GAMMA RAYS BETA+
PARTICLES PARTICLES
NATURE Particulate – two Particulate – Electromagnetic Particulate –
protons and two electrons radiation – positron interacts
neutrons identical to X-rays very rapidly with a
SIZE Large Small Nil negative electron
CHARGE Positive Negative Nil to produce 2
SPEED Slow Fast Very fast gamma rays –
RANGE IN TISSUE 1 – 2 mm 1 – 2 cm As with X-rays annihilation
radiation –
ENERGY RANGE 4 – 8 MeV 100 keV – 6 MeV 1.24 keV – 12.4 properties as
CARRIED MeV shown in adjacent
DAMAGE CAUSED Extensive Ionization Ionization – similar column
ionization damage to X-rays
USE IN NUCLEAR Banned Very limited Main emission PET
MEDICINE used

9. RADIOISOTOPES USED IN
CONVENTIONAL NUCLEAR MEDICINE
 An ideal radionuclide has following properties:
- A short half life.
- Emits γ-rays.
- Capable of binding to a variety of biomolecules.
 Examples of radionuclides together with their target tissues
or target diseases:
- Technetium (99mTc) – Salivary glands, thyroid, bone,
blood, liver, lung & heart.
- Iodine (131I ) – Thyroid
- Gallium ( 67Ga) – Tumors & inflammation
- Krypton (81K) – Lung

10. For imaging Technetium is used extensively, as it
has following properties:
A. Technetium is a gamma emitter. This is important as the rays need
to penetrate the body so the camera can detect them.
B. It has a short half life of 6 1/2 hours. Thus the amount of radioactive
exposure is limited.
C. It is readily attached to a variety of different substances that are
concentrated in different organs, eg:
 Tc + MPD (methylene disphosphonate) in bone
 Tc + sulphur colloid in the liver and spleen.
D. It is easily produced, as and when required, on site.
 Technetium-99m generator or technetium cow or moly cow, is a
device used to extract the isotope 99mTc from a source of decaying
molybdenum-99.

11. γ – SCINTILLATION CAMERA
 A gamma camera, also called a scintillation camera or
Anger camera, is a device used to image gamma emitting
radioisotopes, a technique known as scintigraphy.
 These cameras capture photons and convert them to light
and then to a voltage signal.
 This signal is reconstructed to an image that shows
distribution of radionuclide in the patient.

12. Parts of γ – scintillation camera:
A. Collimator: First part of the
camera that absorbs γ-rays that
do not travel parallel to its plates.
The figure illustrates a magnified
view of a parallel-hole collimator
attached to a crystal. The
collimator simply consists of a
large number of small holes
drilled in a lead plate. Gamma-
rays entering at an angle to the
crystal get absorbed by the lead
and that only those entering
along the direction of the holes
get through to cause
scintillations in the crystal. If the
collimator was not in place these
obliquely incident gamma-rays
would blur the images produced
by the gamma camera. In other
words the images would not be
very clear.

13. B. Scintillation crystal:
 The γ-rays that pass
through the collimator then
strike scintillation crystal.
 Made up of sodium iodide
with trace amount of
thallium.
 This crystal shows
florescence when it absorbs
γ-rays.
 These flashes of light are
detected by photomultiplier
tubes coupled to the crystal.

14. C. Photomultiplier
tubes:
 These tubes detects
the flashes of light
and convert the light
into electronic signal
& amplify the signal.
 Size of signal is
directly proportional
to energy of
absorbed photon.

15. D. Analog to digital
converter:
 The signals from
photomultiplier tubes
go through an analog
to digital converter
(ADC)
 This component is
used to convert the
analogue information
produced by the
imaging system so
that it is coded in the
form of binary
numbers.
 In this way the analog
signal is digitalized &
used to produce
image by computer.

16. BONE SCANS
 Bone scan can detect 10 – 15 % mineral loss
Indications:
1. Metabolic bone diseases such as fibrous dysplasia
2. Pagets disease
3. Osteoarthritis
4. Osteomyelitis
5. Metastasis to bone

17.  Bone scan phases:
PHASE TIME IMPORTANCE
FIRST PHASE: First 30 sec Differences in vascularity to
Radionuclide angiography region.
phase/ dynamic vascular
flow phase
SECOND PHASE: At 5 min Difference in blood flow
Blood pool phase and vascular permeability in
bone
THIRD PHASE: 2 – 4 hours later Distribution of radioisotope
Bone scintigraphy phase/ in bone and metabolic
osseous delayed static image activity of bone

18. Bone scan

19. SALIVARY SCANS
 Principle:
The ability of the salivary glands' intercalated duct
epithelial cells to transport large monovalent
anions, including iodide and pertechnetate, from the
surrounding capillaries and secrete them into the
saliva provides the principle for imaging the salivary
glands with Tc-99m pertechnetate. The functional
capabilities, structural integrity and location of the
glands can be assessed.

20. Indications for salivary gland imaging include:
 Evaluation of functional status of salivary glands
 presentation of xerostomia
 presentation of pain
 Detection and evaluation of duct patency
 pain upon salivation
 presentation of xerostomia
 Detection and evaluation of mass lesions
 Preoperative localization of tumors
 Detecting aplasia of agenesis of gland
 Obstructive disorders
 Traumatic lesions and fistulas
 Function of gland after surgery

21. Salivary scan phases
PHASE TIME IMPORTANCE
FIRST PHASE: Initial At 5 min Distribution of radioisotope
phase in gland
SECOND PHASE: At 10 min (saliva stimulated Retention of radioisotope in
Washout phase by sour drink / candy) gland

22.  Fig 3- Salivary glands scan
 Region of interest on
scintigraphic image:
 area 7, oral cavity
 areas 1 and 2, parotid glands
 areas 4 and 5, submandibular
glands
 area 3, background for parotid
glands
 area 6, background for
submandibular glands and oral
cavity.

23. ADVANTAGES OF NUCLEAR
MEDICINE OVER CONVENTIONAL
RADIOGRAPHY
 Target tissue function is investigated.
 All similar target tissues can be examined during
one investigation, e.g. the whole skeleton can be
imaged during one bone scan.
 Computer analysis and enhancement of results are
available.

24. DISADVANTAGES
 Poor image resolution – only minimal information of
target tissue is obtained.
 The radiation dose to the whole body can be relatively
high.
 Images are not usually disease-specific.
 Difficult to localize exact anatomical site of source of
emission.
 Fascilities are not widely available.

25. Further developments in radioisotope
imaging techniques include:
 SPECT (single photon emission computed tomography)
 PET (Positron emission tomography)

26. SINGLE PHOTON EMISSION
COMPUTED TOMOGRAPHY (SPECT)
 SPECT is a method of acquiring tomographic slices
through a patient.
 Most gamma cameras have SPECT capability.
 In this technique either a single or multiple gamma
cameras is rotated 360 degrees about the patient.
 Image acquisition takes about 30 – 45 min.

27.  Recent SPECT images have been fused with CT images
to improve identifying of the location of the
radionuclide.
 Distribution of radioactivity is displayed as a cross-
sectional image or SPECT scan.
 This image gives the exact anatomical site of the
source of the emissions to be determined.

28. ADVANTAGES OF SPECT
1. Better detailed resolution
2. Enhanced contrast
3. Localization of defects is more precise and more clearly
seen.
4. Extend and size of defects is better defined.

29. APPLICATIONS OF SPECT
 1. Heart Imaging
 2. Brain Imaging
 4. Tumor detection SPECT can be used to detect tumors in
cancer patients in the early stages.
 5. Bone Scans
 In maxillofacial region, the most common use of nuclear medicine is
to investigate abnormal metabolite bone activity, for instance, in
assessing growth activity in cases of condylar hyperplasia.
Traditionally a combination of 99mTc MDP and
gallium citrate is used to assess bone activity.
+

30. POSITRON EMISSION TOMOGRAPHY (PET)
 PET is more advanced imaging modality in nuclear medicine.
 The distribution of radioactivity in slices of organs can be
obtained in a more accurate way using PET.
 In the PET camera two cameras called Anger cameras are place on
opposite sides of the patient. This increases the collection angle and
reduces the collection times which are the limitations of SPECT.
 PET, radiopharmaceuticals are labeled with positron emitting
isotopes. A positron combines rather quickly with an electron. As a
result the two gamma quanta are emitted almost in opposite
directions .

31.  The mass of the two particles is annihilated (the
destruction of a particle and its antiparticle when they
collide) with the emission of 2 gamma rays of high energy
(511 keV) at 180 degree to each other.
 These emissions, known as annihilation radiation, can then
be detected simultaneously (in coincidence) by opposite
radiation detectors which are arranged in a ring around the
patient.
 The exact site of origin of each signal is recorded and a
cross-sectional slice is displayed as a PET scan.

32. BASIC PHYSICS OF PET

33. The variety of radioisotopes which
can now be used clinically in PET
include:
- 11C – Carbon
- 13N – Nitrogen
- 15O – Oxygen
- 18F – Fluorine (18F-Fluorodeoxyglucose positron
emission tomography)

34. APPLICATIONS
 Oncology
 Neurology
 Cardiology

35. REFERENCES
Essentials of dental radiography & radiology
 ERIC WHAITES EDITION 4
 YEAR OF PUBLICATION -2008,
 Publishers – Elsevier
 Page 15
Oral radiology – principles and interpretation
 STUART WHITE & MICHAEL. J. PHAROAH EDITION 6
 YEAR OF PUBLICATION- 2009
 Publishers – Elsevier
 Page 2
Textbook of Dental & maxillofacial radiology
 FRENY R KARJODKAR SECOND EDITION
 YEAR OF PUBLICATION- 2009
 Publishers – JAYPEE
 Page 17
Internet

36. THANK
YOU