Ct Registry Ch3 Pt1

Front 1

What are the five key influences on parameter selection?

Back 1

Contrast Resolution

Spatial Resolution

Temporal Resolution

Image Noise

Patient Dose

Front 2

______________ is the ability to differentiate small differences in density on the image.

Back 2

contrast resolution

Front 3

______________ is a measure of the size of the smallest object that can be visualized in an image.

Back 3

Spatial Resolution

Front 4

Typically, tissues with differences in density of less than ______________ can be differentiated with CT.

Back 4

0.5%

Front 5

Name the four geometric factors that can affect spatial resolution.

Back 5

focal spot size

detector aperture size

focal spot to patient distance

patient to detector distance

Front 6

Name the four factors that we can control that affect spatial resolution.

Back 6

slice thickness

display FOV

image matrix

reconstruction filter

Front 7

Spatial resolution is often expressed in terms of ______________.

Back 7

line pairs

Front 8

A resolution test consists of scanning a water phantom and determining the ______________.

Back 8

smallest line pair that can be resolved

Front 9

In a resolution test, the formula to find the spatial resolution is ______________.

Back 9

10 divided by (number of lines)
or 10 divided by (2 times number of line pairs)

Front 10

______________ refers to the precision of a measurement with respect to time.

Back 10

Temporal Resolution

Front 11

Technological improvements that have allowed CT scans to be completed more rapidly have ______________ the temporal resolution possible with CT.

Back 11

increased

Front 12

As temporal resolution increases so can ______________.

Back 12

spatial resolution

Front 13

Name 3 technological improvements that increased temporal resolution over the years.

Back 13

helical scanning

multi-row detector scanners

retrospective ECG triggering

Front 14

______________ appears in a CT image as a point-to-point fluctuation in the CT number within a uniform material.

Back 14

noise

Front 15

An image will appear more noisy, or grainy, when there are ______________ contributing to the pixels.

Back 15

fewer photons

Front 16

A easy way to increase the number of contributing photons is to increase the ______________.

Back 16

tube current or the scan time

Front 17

The ______________ is the amount of ionizing radiation absorbed by the patient per unit mass.

Back 17

dose

Front 18

There is a tradeoff between ______________ and minimizing the patient dose.

Back 18

maximizing the image quality

Front 19

What 7 things affect patient dose in CT?

Back 19

scan rotation time

tube current

peak tube voltage

slice thickness

table increment

pitch

anatomical coverage desired

Front 20

What 4 things does the amount of attenuation depend on?

Back 20

atomic number

density of electrons

thickness

photon energy