Lucknow Call girls - 8800925952 - 24x7 service with hotel room
Muhammad yaseen
1. NUCLEAR IMAGING
Prepared By:
Muhammad Yaseen
Trainee Med. Physicist
Radiology Department
Mail: myaseena@hotmail.com
2. Contents
Introduction
Advantages Of Nuclear Imaging
Radiography Vs Nuclear Imaging
Radioisotopes used in NM
Radiopharmaceuticals
Gamma Camera
SPECT
Safety
Summary
3. 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.
4. Advantages Of Nuclear Medicine
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.
5. Radiographic Vs Nuclear Imaging
Radiographic Imaging Nuclear Imaging
Transmission Type Image Emission Type Of Image
Morphologic Imaging Functional Imaging
High Resolution Low Resolution
Use X-rays Use Gamma Rays
Short Time Long Time
6. 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
7. 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, e.g.
- Tc + MDP (methylene disphosphonate) in bone
- Tc + sulphur colloid in the liver and spleen.
D. It is easily produced, as and when required, on site.
9. 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
10. 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 strength 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.
14. GAMMA 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.
These signals are reconstructed to an image that shows
distribution of radionuclide in the patient.
15. Gamma Camera Components
Collimator
Crystal
PM Tubes
Analog To Digital Convertor
X And Y Positioning Circuits
A Visual Display With Display Electronics
16.
17. Collimator
The collimator can be made from lead foil.
The collimator stops about 99.9% of the available
photons.
The walls of each channel in the collimator are called
septa, and if a photon manages to penetrate the wall, it
is called septal penetration.
19. Parallel Hole Collimator
LEGP (low energy general
purpose) or LEAP (low
energy all purpose).
To increase the resolution,
smaller diameter holes are
needed.
To increase sensitivity, the
holes need to be wider.
20. Parallel Hole Collimator
To image higher energy
isotopes such as Ga-67 or
I-131, the collimator needs
to have thicker septa in
order to stop penetration.
This produces a heavier
collimator with lower
sensitivity.
22. Crystal (NaI)
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.
23. Photo Multiplier Tube
Extremely sensitive detector of light in the ultraviolet,
visible and near infrared
Multiplies the signal produced by incident light by as
much as 108
• single photons can be resolved
High gain, low noise, high frequency response, and large
area of collection
A tiny and normally undetectable current becomes a
much larger and easily measurable current
24. Components Of PMT
Made of a glass
vacuum tube
Photocathode
Several dynodes
One anode
26. Analog To Digital Convertor
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
28. Further Developments in Radioisotope
Imaging Techniques Include
SPECT (single photon emission computed tomography)
And
PET (Positron emission tomography)
29. Single Photon Emission Computed
Tomography
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.
30. Applications of SPECT
Heart Imaging
Brain Imaging
Tumor detection SPECT can be used to detect tumors in
cancer patients in the early stages.
Bone Scans
31. Advantages of SPECT
Better detailed resolution
Enhanced contrast
Localization of defects is more precise and more
clearly seen.
Extend and size of defects is better defined.
32. Limitation Of Nuclear Medicine
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.
Facilities are not widely available.
33. Safety Precautions
Injected patient should avoid to keep away from everyone
but specially from children and pregnant women
Only authorized users are allowed to handle the source.
Do not look directly into bore hole of the source holder or
cover it with any part of your body.
Use Lead Apron, lead goggles and lead thyroid shield
