Midterm- CT

Which of the following CT numbers represents water

0

As the display field of view decreases 1. noise increases 2. spatial resolution increases 3. spatial resolution decreases

1&2

Window level (WL) refers to: 1. the midpoint in a range of CT numbers. 2. image contrast. 3. image brightness. a) 1 and 2 b) 1 and 3 c) 2 and 3 d) 1, 2 and 3

1&3

A standard algorithm program was used to reconstruct the brain from the top of the head to the base of the skull. In order to have images that show bone contrast, the technologist must readjust the 1. raw data 2. window level 3. window width

2&3

Volume acquisition scanners are based on: 1. slice by slice date acquisition 2. slip ring technology 3. continuous rotation of the x ray tube

2&3

The national council on raditation protection and measurements recommends that the annual occupational dose for imaging professionals not exceed

50 mSv

A CT scanner with 16 detector rows, each scanning 4 widths, is called a __________- slice.

64?????

Gating is a technique that can effectively reduce patient dose by as much as _____ %. a. 100 b. 90 c. 80 d. 70

70

Second generation scanning employed

a fan beam/ multidetectors

Reformation is

a reconstruction of the raw data into the plane that was scanned

In CT imaging, the z- axis refers to the ____ plane

axial

Beam-shaping filters are designed to: a. remove higher-energy photons from the beam. b. change the spatial distribution of the beam. c. decrease subject contrast. d. restrict the path of photons coming from the x-ray tube.

change the spatial distribution of the beam

which of the following x-ray beam geometries is used by modern, multidetector CT scanners?

cone beam

The function of a bow-tie filter is/are to 1. decrease the beam energy at the periphery of the patient 2. shape the beam to be more polychromatic 3. minimize beam hardening artifacts

decrease the beam energy at the periphery of the patient

As pitch increases, patient dose

decreases

In multi-slice CT, as the pitch increases, the z-gap ______ and the image quality _____.

decreases, increases

Which of the following most closely approximates the actual radiation dose to a specific patient for a specific exam?

dose length product

As slice thickness increases, the patient dose increased?

false

As a technologist, if you want to decrease the original pixel size by half, what scanning parameter must be changed?

field of view (FOV)

First generation scanners were only capable of imaging the

head/brain

The window width (WW) determines the

image contrast

For CT scanning, as mAs increases, patient dose _____ and image noise _____ . a. decreases; decreases b. increases; increases c. increases; decreases d. decreases; increases

increases, decreases

As the display field of view increases, the resulting radiation dose to the patient: a. decreases b. increases c. is not affected.

is not affected

Compared to barium used for regular fluoroscopy procedures, the barium used for CT procedures is: a. less dense. b. more dense. c. of the same density.

less dense

First generation CT scanners used _____ beam scanning

pencil

Which of the following describes a characteristic of a first- generation CT scanner?

pencil x- ray beam and detector

Which of the following is the most effective type of CT detector?

scintillation

Which of the following International System of Units (Si ) measurements is associated with monitoring radiology staff?

sievert (Sv)

All power to the gantry of a spiral-helical CT scanner is conveyed via: a. high-tension cables. b. rotating wire brushes. c. photon flux. d. slip rings.

slip rings

when a spiral-helical CT scanner takes a scout image, the x-ray tube is

stationary

In multislice CT scanners, detector systems with equal-size detector elements are called _____ arrays. a. linear b. curved c. adaptive d. symmetric

symmetric

An image is said to have good spatial resolution if the boundaries of an object are distinct and have sharp borders

true

The size of the field of view represents the length of the diameter created when the x-ray tube scans around the patient

true

In sixth generation CT scanners, which of the following elements rotate around the patient?

x-ray tube and detectors