Digital Imaging Ch. 19 ICC

Which matrix size below has the smallest pixel size for a given FOV?

1024x1024

How many pixels are needed to image a line pair (lp):

2

It takes a minimum of ________ pixel(s) to image one line pair.

2

the minimum number of pixels needed to image one line pair

2

A pixel with a bit depth of 11 can display ________ shades of gray.

2048

portion of the collimated field that contains the anatomy and displayed on the monitor

FOV

Pixel size = matrix size / FOV

False, it's F/m

Spatial resolution describes the MAXIMUM separation of two objects that can be distinguished as separate objects in the image

False, it's minimum separation

Describes how much of the patient is imaged in a digital image matrix

Field of View

Contrast resolution can be described as the:

MINIMUM density or intensity difference of two objects that can be distinguished as separate in the image.

A line pair is a line in the image and the space next to it (its corresponding interspace).

True

A principal advantage of digital imaging over film/screen is the ability to post-process the image appearance:

True

Changes in FOV and matrix size will NOT affect each other, but a change in either one will affect pixel size

True

The bit depth of the image pixel determines how many shades of gray it can display.

True

Adjusting ____________ up or down changes the density (brightness) of a digital image.

Window level

A digital image is made up of

a matrix of pixels

Any unwanted information on an image is the definition for

artifacts

language used by computers

binary

Calculated using the formula, 2^n; reports the number of gray shades available

bit depth

the number of shades of gray that can be demonstrated in a digital image is affected by

bit depth

Amount of luminance an image displays on a monitor

brightness

The amount of luminance of an image or light displayed by a monitor is termed

brightness

the window level control is used to alter image

brightness

if a pixel has a bit depth of 8, this means that the pixel

can produce 256 shades of gray

The Digital image quality which is controlled by window width.

contrast

the window width control is used to alter image

contrast

in general, as image noise increases

contrast decreases

the ability of a system to distinguish between and/or display objects that attenuate xray photons differently

contrast resolution

if pixel pitch is increased, the image will have/display

decreased spatial resolution

If the FOV is constant, then as the matrix size increases, the pixel size ____________.

decreases

Spatial resolution increases as pixel size ___________.

decreases

The ability to detect and display a large range of radiographic densities: a wide

dynamic range

To improve contrast resolution, you want a ________ Signal to Noise Ratio (SNR):

high

The FOV best describes:

how much of the patient is imaged in a matrix

The FOV best describes

how much of the patient is imaged in the matrix

The statistical fluctuation of data or intensities in the image is called:

image noise

If the FOV increases but the matrix size is unchanged, then contrast resolution will:

improve b/c the pixel size will be larger

If the FOV remains unchanged and the matrix size increases, the spatial resolution will be

improved

which of the following image quality changes is undesirable

increased image noise

If pixel density is increased, the image will have/display

increased spatial resolution

Contrast resolution increases as pixel size ___________.

increases

If the matrix size is constant, then as the FOV increases, the pixel size _____________.

increases

As the number of XR photons reaching the detectors increases, the signal produced ___________ and the subsequent image noise __________.

increases, decreases

As the window width (WW) increases, the number of different intensities (shades of gray) in the image ____________ and therefore the image contrast ___________.

increases, decreasesd

As the amount of noise decreases in the image, the contrast resolution __________ and the spatial resolution __________.

increases, is not affected b/c actually noise does not affect SR, ie. RD, ie. sharpness

Which of the following will allow more line pairs/mm to be imaged?

increasing the number of pixels

spatial detail in a digital imaging system would be improved most by

increasing the number of pixels

which of the following will allow more line pairs/mm to be imaged

increasing the number of pixels

For a given FOV, spatial resolution will be ___________ for a ____________ matrix size:

lower, smaller b/c smaller matrix size means bigger pixel size

A discrete number of rows and columns in a square are known as a:

matrix

array of cells arranged in columns and rows

matrix

A digital image is made up of a:

matrix of pixels

1,024 x 1,024 is a measure of this quantity

matrix size

if the window width control is opened wider

more gray shades will be available

The statistical fluctuation in image data due to a weak signal is called:

noise

image quality constituted of unwanted or useless background information

noise

The bit depth of a pixel determines the:

number of intensities or shades of gray it can display

The H & D curve for digital is linear rather than S shaped because

of a wider dynamic range

each cell in a matrix

pixel

the distance or spacing from the middle one pixel to the middle of an adjacent pixel

pixel pitch

the use of high resolution monitors

promotes the visibility of anatomical structures

The anatomical structures that would cause the greatest degree of xray photon attenuation and i mage brightness would be those that are

radiopaque

If the FOV increases and the matrix size is unchanged, pixel size will

remain unchanged also

if a high degree of quantum mottle is noted on an image, the most appropriate solution to correct this exposure error would be to

repeat the exposure using a high mAs

which of the following is a contributor to image noise

scatter plus densities minus densities

Formula to calculate this is 1/2 (PS); determines the number of lines pairs that can be resolved if the pixel size is known

spatial frequency

The number of lp/mm (line pairs per millimeter) is a measure of the __________ in an image.

spatial resolution

Contrast Resolution describes:

the minimum density difference b/t two tissues that can distinguish separate tissues

Contrast resolution describes

the minimum density difference between two tissues that can distinguish separate tissues

Window width controls:

the number of density or intensity differences in the image

if an anatomical structure is smaller than one pixel

the structure will not be visualized

Digital imaging has ____________ compared with film/screen:

wider exposure latitude

Increasing the ____________ would result in a brighter digital image:

window level

Term used to describe the degree of brightness in the image. It is equal to the "midpoint " of the range of intensities displayed:

window level

The average or midpoint brightness or intensity level in the image is called the:

window level

postprocessing function that alters image brightness

window level

Term used to describe the "range" or number of different intensities displayed in the image:

window width

The 'range' of the image gray scale is called the:

window width

postprocessing function that alters image contrast or gray scale

window width

Refers to the change in appearance of an image as you change the WL or WW (using the mouse):

windowing