Fundamentals of Imaging This course will provide you with the principles involved in the formation and recording of the radiologic image in both conventional and digital imaging systems as well as the principles of image quality assessment. Control of Scatter Radiation

1. Fundamentals of
Imaging
RAD 206
Digital Imaging, Artifacts & Errors

2. The advantages of CR are its large dynamic range, digital
format, portability, and post-processing capability
But not PERFECT –Imaging Errors can still occur
2

3. What is Digital Radiography?
• Historically, digital radiography referred to
specialized modalities that produced digital
images.
• Examples would include:
– CT
– MRI
– Nuclear Medicine
– Ultrasound

4. Digital Radiography Today
• Since the early 1990s, Digital Radiography has
grown to include Computed Radiography(CR)
and ‘true’ Digital Radiography(DR) or Direct
Radiography.

5. Computer Language
• Computer Letters are on off
or 1 0
5
That is binary
digits
( numbers)

6. Example of Computer words
6

7. 7
Illustration of the exposure, readout and erasure stages involved in
generating a computed radiography image

8. Image Matrix
x
8
Y
(X7-Y5-11)

9. • PixelsPixels are individual picture elements in
a two-dimensional image.
• matrixmatrix is the total number of pixels in an
image ( from vertical and horizontal
dimensions).( If there are 1,024 (1 k) pixels in
both the horizontal and vertical dimensions, then the
image contains 1 k x 1 k = 1 M, or 1,0242
pixels.)
9

10. Matrix , Pixel , Voxel
10

11. Types of Digital Radiography
in convectional Radiography
• Detectors in Digital Imaging
• Gas and solid state detectors (CT scan and BMD)
• Scintillators Detectors & Photoconductors
(Nuclear Med)
• Photo-stimulable phosphors for CRCR ( computed
Radiography)
• DDRDDR or DRDR (Direct Digital Radiography)
11

12. • Bit
– 0 or 1
– ( see also KB, MB, GB)
• Byte
– The amount of gray scale in the image. The bit is the exponent
to two, ie, a 2 bit image is two to the second (or four), So the
image would have 4 shades of gray possible. Today, images are
10 or 12 bit.
Common Digital Terms

13. 13

14. Common Digital Terms
• Pixel
– Picture element. This is the basic component of
the digital image, it is what we see. 2 dimensional
• Voxel
– Volume element. This is a 3 dimensional element
that includes depth. The pixel is essentially the
end of the voxel.

15. • Matrix
– The actual image we see is made up of a series of pixels in
rows and columns called a matrix. Generally, the larger the
matrix the better the spatial resolution of the image. (512 x
512)
• FoV
– Field of view. This is how much anatomy is
displayed. A 12 cm FoV will display 12 cm of
anatomy on the screen. The smaller the FoV the
more magnified the anatomy is.
Common Digital Terms

16. Common Digital Terms
• Window width
– The gray scale of the digital image. The larger
the width the more grays demonstrated the
lower the contrast of the image.
• Window level
– The density or brightness of the image. The
higher the number the brighter the image.