RAD111 Ch1 PT2 Digital Imaging Characteristics

Digital Imaging characteristics

spatial resolution

contrast resolution

image signal

Spatial resolution (detail)

2D xray images are formed by a matrix of pixels.

Pixels are also known as DEL or detector elements.

pixel size decreases = matrix size increases

more pixels= greater spatial resolution

Contrast (brightness)

the difference in brightness between light and dark areas of an image

low contrast is desirable for chest images to distinguish the fine lung markings with the various shades of gray

Factors that affect contrast:

scatter radiation

contrast resolution

the ability of a digital imaging system to distinguish signals detected after penetration through tissues similar in density that are close together

Image signal

digital imaging systems have wide dynamic range

- exposure latitude must be defined

Signal-to-noise ratio (SNR)

noise in digital images.

the number of xray photons that hit the receptor (mAs) is considered the signal.

factors that negatively impact the final image is the noise.

high SNR is desirable bc the signal is greater than the noise. low contrast soft tissue structures can be seen better