1. RAD 350 Chapter 17Digital Rad Tech. Spatial Resolution – ability to distinguish small items in close proximity with near the same atomic mass density Spatial Frequency – refers to “black lines” on a light background with space between the black lines the same width as the lines Used in mammo and fluoro especially and with digital systems to check spatial resolution

2. Spatial resolution in digital imaging Pixel and voxel size will greatly affect how the spatial resolution really looks on an image

3. Modulation Transfer Function (MTF) MTF is the ability to correctly transfer object detail onto an image

4. Contrast/Contrast Resolution Hi contrast = black and white (short scale – two densities – one black on white = 100% contrast Contrast resolution = MANY shades of gray = low contrast!

5. Dynamic Range Densities able to be seen on an image from base+fog (zero for digital) to maximum density OD 2.5 on the H & D curve. Remember humans only can see about 30 shades of gray! Postprocessing a digital image can widen or shorten the gray scale seen

6. Signal to Noise Ratio Relation of signal (image electrical strength to amount of electrical interference {noise} in the system) To increase SNR – either raise the signal or lower the noise or BOTH

7. Patient Dose Digital images can be post-process “manipulated” Don’t repeat an exposure to alter contrast or lighten the image as one can do that after exposure Tend to “burn it out” since one may “manipulate the image after exposing”

8. Detective Quantum Efficiency Patient’s spatial resolution and the receptors ability to effectively and accurately display the image and is determined by the thickness of the “capture layer” and it’s atomic composition DQE is the measure of x-ray absorption efficency