The document discusses factors that influence medical image quality during fluoroscopy. It states that image quality depends on both intrinsic characteristics of the imaging system as well as the observer. Key factors that determine statistical image quality include the number of x-ray photons absorbed and noise from photon variation. Common image distortions in fluoroscopy include veiling glare, vignetting, blooming, and pincushion or S-shaped distortions. The ideal resolution is 1.2 line pairs per millimeter and image quality considerations encompass contrast, resolution, temporal fidelity, dynamic range, and visual perception.

1. Sarbari Saha
Asst. Professor, Radiology

2. • Image quality is the quality of object which depends only on
intrinsic objective , physical characteristic, of a imaging system
and can be measured independently on the observer.
• Image is whatever the observer sees it is the eye of the beholder.
• It is an observer ability to achieve an acceptable level of
performance for a specific task.
• The number of x-ray photons absorbed by the image intensifier
determines the statistical quality of a fluoroscopic image.
• The image quality of an fluoroscopy system is defined by –
Scintillation, contrast and distortion.

3. Image
Production
X-ray
intensity
Distribution
Radiation Capture
(Detector output
light intensity
distribution)
Visual Image
(Film, display
monitor)

4. -----technology.
----- proper equipment design.
----- proper set up of equipment parameters.
-----proper utilization of the equipment.
------ knowledge and skills of the radiographers and radiologist.

6. Key consideration
Contrast to noise.
Resolution, density.
Temporal fidelity.
Dynamic range rendering.
Visual perception.
Skin dose.
Sharpness.
Graininess.
The ideal resolution should be 1.2lp/m.

7. Scintillation
• It is often used to indicate the emission of light or give off varying
amounts of light.
• Quantum noise is the variation of intensity distribution of the x-ray beam.
• The resultant can cause quantum mottle in the image
• The noise pattern, since it is random, in nature , has the tendency to appear
to be moving like a expression of crawling ants or snow.
• This effect is due to insufficient no of x-ray per unit time.
Remedies: Increase the tube current(mA) to generate more x-ray quanta.

8. Sharpness

9. Resolution & Density

10. Dynamic range of rendering

11. Temporal fidelity

12. Graininess

13. Contrast
• Image Intensifier not good at preservation of image contrast.
• Any light emitted at the output phosphor screen moving backward
through the tube axis.
• Contrast tends to deteriorate as image intensifier gets older, almost
10% per year.

14. Image Distortion in Fluoroscopy
The most common type of image distortion in fluoroscopy are as follows:
 Veiling Glare: It is the artefact related to internal light scattering at
output phosphor, it results in significant loss of image contrast particularly in
an image area representing high x-ray attenuation in the object.
Any brightness in the middle area of the disc image, which should be dark
indicates the veiling glare from scattered light, x-rays and electrons.
Vignetting: A optical distortion that produce a fall off at the edges. As
brightness measured at the output phosphor will vary from center to the
periphery of the image. So the resolution is better with increased resolution
and less distortion at center.
One source is pincushion artefact. It is caused mainly due to detoriation of the
video camera, camera or multi electro lens.
It can be overcome by electron –concentration effect of electronic optics.

15. Blooming: It is caused by the input of signals to the
video.
Pincushion & S Distortion: Pincushion
Distortion is a geometric, nonlinear magnified across
the image.
Appearance of straight lines curving towards the edge.
It can be seen clearly on rectangular grid.
S distortion is when electrons within the image intensifier
moves in paths along designated lines of flux, where the
image gets S shaped.
It is more larger type image intensifier so to reduce it
manufacture use highly conducting mu-metal that
reduces the vacuum bottle.
Pin cushion
S- Distortion

16. Conclusion
• Image quality is not just detector metrics.
• Image quality is not just a subjective impression.
• Image quality is a moving target.
• Patient dose need not be linked to detector dose or KVp.
• Demand and use aggressive spectral filtration.
• Use of pulsed fluoroscopy and the aufrichtig scale to produce better
images, not solely to reduce dose.
• Remember that visual perception can sometimes mask the true nature
of image attributes.

17. .......a thirst for knowledge and learning
that will last a lifetime….
“keep learning”-