Ct Registry Ch8 Pt1

Front 1

_______________ is the increase in average energy of the x-ray beam as it penetrates tissue.

Back 1

beam hardening

Front 2

The degree of beam hardening is dependent upon the _______________ and _______________.

Back 2

body part being penetrated

its composition

Front 3

beam hardening can cause a variation in the _______________ of a given tissue type from the periphery to the center of an image.

Back 3

CT Number

Front 4

______________ is a phenomenon when central tissues are surrounded by denser material and as a result of beam hardening may appear to be less dense than they actually are.

Back 4

cupping

Front 5

Beam hardening may be manifested by broad streaks when scanning thick body parts. Anatomical parts that may cause this are:(4)

Back 5

petrous pyramids of the temporal bones
shoulders
ribs
hips

Front 6

What can be done to minimize beam hardening?(4)

Back 6

Use thin slices

dilute the contrast

perform scan with slight delay after iv contrast

scan in the opposite direction

Front 7

What is partial volume artifact?

Back 7

partial volume artifact is a situation where a voxel contains more than one type of tissue. The CT number assigned to this voxel is determined by a weighted average of the densities within the voxel rather than displaying each tissue type individually.

Front 8

To minimize partial volume artifacts, ____________ should be selected.

Back 8

thinner slices

Front 9

As slice thickness decreases, apparent noise in the image is ______________. to counteract this, the mAs should be _______________.

Back 9

increased

increased

Front 10

A ghost artifact looks like a _________________ of a tissue boundary.

Back 10

double margin

Front 11

It is important to ensure your patient is _______________, _______________, and _______________.

Back 11

comfortable

understands the procedure

able to perform necessary breathing requirements

Front 12

Metal artifacts can cause streaks emanating from the object. These are caused by a combination of: (4)

Back 12

beam hardening

edge gradient effect

partial volume effect

motion

Front 13

_______________ occurs when different attenuation coefficients are obtained for the same object depending upon the vantage point of the projection.

Back 13

edge gradient effect

Front 14

The edge gradient effect appears as streaks which emanate from structures that have _______________ and _______________.

Back 14

sharp edges

great density differences from neighboring tissues

Front 15

The _______________ the detector, and the _______________ projections acquired reduce the chances of edge gradient effects occurring.

Back 15

smaller

more

Front 16

A way that the CT tech can reduce edge gradient effect from occurring is:(3)

Back 16

if possible, move the structure that causes the edge gradient effect or reposition patient

Increase data sampling, or oversampling

use thinner slices

Front 17

________________ occur because the anatomy outside the scan field-of-view contributes toward the attenuation and hardening of the x-ray beam, but it is ignored during the image reconstruction process.

Back 17

out-of-field artifacts

Front 18

Sometimes out-of-field artifacts may be caused by _______________

Back 18

an obstruction of the reference detectors by the patient's body

Front 19

The result of out-of-field artifacts is a variation and inaccuracy of the _______________ of the tissues in the final images.

Back 19

CT Number

Front 20

The Ring Artifact is typically caused by a _______________ on a 3rd generation scanner.

Back 20

faulty detector

Front 21

If a detector has an offset difference of as little as _______________ with neighboring detectors, a ring artifact may result.

Back 21

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