1. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Important points in chapter 3 (chapter 14 and 15 from the book)
We discuss the essential elements of image quality in nuclear medicine and how it is measured and characterized
We describe the major factors that determine gamma camera performance Standard tests of gamma camera performance
The general concepts are applicable as well to the tomo-graphic imaging techniques

2. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Important points in chapter 3 (chapter 14 and 15 from the book)
Part-1
Part-2
Gamma camera performance characteristics
Image quality of gamma camera

3. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Image quality
Image quality refers to the faithfulness with which and image represents the imaged object
The quality of nuclear medicine images is limited by several factors
The gamma camera is not capable of producing “perfect” images of the radionuclide distribution
Certain inherent imperfections arises from the performance characteristics of the detector, its associated electronic circuitry, and the collimator
Image artifacts also can be caused by malfunctions of various camera components

4. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Basic Methods for characterizing and evaluating image quality
The first by means of physical characteristics that can be quantitatively measured or calculated for the image and image system
Spatial resolution
Contrast
Noise
Contrast-to-noise ratio (CNR)
The second by means of observer performance studies using images obtained with different imaging systems or under different imaging conditions

5. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Basic Methods for characterizing and evaluating image quality
Although they describe 3 different aspects of image quality these 3 factors cannot be treated as completely independent parameters because improvements in one of them frequently are obtained at the expense or deterioration of one or more of the others
Example; collimator resolution and efficiency
Although observer performance can be characterized objectively, and certainly is related to the physical measures of image quality, the relationships are not well established due to the complexity of the human visual system and other complicating factors, such as observer experience

6. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Basic Methods for characterizing and evaluating image quality
Hence;
The two methods, though related, are some what independent

7. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Basic Methods for characterizing and evaluating image quality
The first by means of physical characteristics that can be quantitatively measured or calculated for the image and image system
Spatial resolution
Contrast
Noise
Contrast-to-noise ratio (CNR)
The second by means of observer performance studies using images obtained with different imaging systems or under different imaging conditions

8. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Spatial resolution refers to the sharpness or detail of the image, or to the ability of the imaging instrument to provide such sharpness or details
Sharp edges or small, pointed objects produce blurred rather than sharply defined images
Part of the blurring arises from collimator characteristics and part arises in the detector and electronics
Resolution is related to position so anything would affect the positioning process would affect the resolution

9. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Intrinsic spatial resolution
The limit of spatial resolution achievable by the detector and electronics, ignoring additional blurring due to the collimator
collimator spatial resolution

10. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Intrinsic spatial resolution is limited primarily by two factors
The multiple scattering of photons within the detector
The statistical fluctuation in the distribution of light photons among PMTs from one scintillation event to the next

11. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Intrinsic spatial resolution is limited primarily by two factors

12. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Interaction of Photons with matter
Compton
scattering
Photoelectric effect
Pair production
Predominant type of interaction for various combinations
of incident photons and absorber atomic numbers

13. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Intrinsic spatial resolution
The intrinsic resolution is a function of gamma rays energy

14. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Intrinsic spatial resolution

15. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Intrinsic spatial resolution
Modern cameras are substantially improved over earlier versions because of
The use of more efficient PMs tubes and better techniques for optical coupling between the detector crystal and the PM tubes
The use of greater numbers of smaller PMTs (some gamma cameras have as many as 110 PMTs per head)
The use of improved electronics
The use of accurate corrections for nonlinearity and non-uniformity

16. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Intrinsic spatial resolution
The intrinsic spatial resolution makes a negligible contribution to the overall system resolution of the gamma camera, which is largely determined by the resolution of the collimator

17. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Is perhaps the principle limiting factor when absorptive collimators are used for spatial localization
Because collimator hole diameters must be relatively large (to obtain reasonable collimator efficiency), there is blurring of the image by an amount at least as great as the hole diameters
Collimator resolution also depends on source-to-detector distance

18. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution

19. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution

20. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Design considerations for parallel hole collimators
Septal thickness
Geometry of Collimator holes

21. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Design considerations for parallel hole collimators
Septal thickness

22. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Design considerations for parallel hole
collimators
Septal thickness

23. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Design considerations for parallel hole
collimators
Septal thickness

24. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Design considerations for parallel hole
collimators
Septal thickness

25. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Design considerations for parallel hole
collimators
Septal thickness

26. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Design considerations for parallel hole collimators
Geometry of collimator holes

27. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Design considerations for parallel hole collimators
Geometry of collimator holes

28. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Source-to-collimator distance

29. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator spatial resolution
Source-to-collimator distance

30. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator efficiency
Source-to-collimator distance

31. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator efficiency
Source-to-collimator distance

32. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Collimator efficiency
Source-to-collimator distance

33. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
System resolution (extrinsic resolution)

34. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical
characteristics
Spatial resolution
Methods for evaluating spatial resolution
Talk about the FWHM

35. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Other factors could affect spatial resolution
Image sharpness (resolution) can be affected by patient motion

36. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Other factors could affect spatial resolution

37. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Other factors could affect spatial resolution
The image resolution also can be affected by the display system

38. Image quality and Performance Characteristics
Chapter-3
The Gamma Camera
Image quality and Performance Characteristics
Evaluating image quality using physical characteristics
Spatial resolution
Other factors could affect spatial resolution
The image resolution also can be affected by the display system