Nuclear imaging uses radioactive tracers and gamma cameras to produce functional images of the body. It has advantages over radiography like examining whole organs at once and providing computerized analysis. Common radiotracers like Tc-99m have short half-lives and emit gamma rays detectable by gamma cameras. These cameras use collimators, scintillation crystals and photomultiplier tubes to convert gamma rays into 2D images. SPECT provides 3D tomographic images by rotating gamma cameras around the patient. Nuclear imaging is useful for assessing organ function but has limitations like low resolution and radiation exposure.

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.

8. Tc-99m

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.

11. Bone Scan & Thyroid Scan Images

12. Pharmaceutical
Organ Pharmaceutical
Tc-99m pertechnetate
Brain Tc-99m DTPA
Tc-99m glucoheptonate
Cardiac Tc-99m pyrophosphate
Liver Tc-99m sulfur colloid
Tc-99m DTPA
Kidney Tc-99m DMSA
Tc-99m glucoheptonate
I-131
Thyroid I-131 Hippuran

13. General Imaging Consideration

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

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.

18. Types Of Collimator
 Parallel Hole Collimator
 Converging Collimator
 Diverging Collimator
 Pin Hole Collimator

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.

21. Pin Hole ,Converging &Diverging
Collimators
Converging

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

25. How It Works

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

27. X And Y Position Circuit

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

34. Summary

35. References
 Medical instrumentation by :
Jennifer Prekeges
 The essential physics of medical imaging by:
Bush Berg