intro and basic principles

what type of supervision is required in ct

direct supervision

how many hours of education (distributed over 4 different subject matters) are required by the arrt for you to sit for the ct registry

16 hours

how many ct numbers are required by the arrt for you to sit for your registry

125

how many ct numbers are required for us to get in ct clinical this semester

50

what is the maximum number of each ct exam that you can record for the arrt post primary certification

5

what is the total number of objectives you will need to turn in for ct this semester

4

what is the total number of evaluations you will need to get in ct this semester

2

what requires direct supervision in ct

contrast administration

venipuncture

scanning

what does tomo mean

to cut, section, or slice

what are the 3 advantages of ct over conventional radiography

superior image quality

no superimposition

ability to differentiate between small differences in densities

what direction does the x axis on ct axes move

right to left

what direction does the y axis on ct axes move

anterior to posterior

what direction does the z axis on ct axes move

superior to inferior

what is the point that all 3 axes meet

orgin

which axes make up a pixel

2D

x and y

which axes make up a voxel

3D

x, y, and z

if given a matrix size of 512 be able to calculate the number of pixels

512 × 512 = 262,144

what is beam attenuation

the reduction of xray as it passes through matter

what are the 3 things that can happen when xray photons pass through matter

absorption

scatter

penetration

what are the 3 properties of matter that affect the number of photons that interact with matter

density

thickness

atomic number of tissue

what is the effect of increasing these properties on the number of photons that interact with matter

if increased= more is reduced and it appears white

what is the definition of linear attenuation coefficient

the amount of xray beam that is scattered or absorbed per unit thickness of the absorber

what can a technologist do to change/affect attenuation (factor)

kVp

what are the shades of gray/ct numbers called in ct

hounsfield units (Hu)

what is the ct number for bone

+1000

what is the ct number for water

0

what is the ct number for air

-1000

what is used to compare the linear attenuation coefficient to to assign a housfield unit

water

what postprocessing tool can be used to determine the ct number of an area and the standard deviation of the pixels within in

ROI

what does polychromatic mean related to the xray beam

an xray beam that is composed of photons with varying energies

what is beam hardening

an artifact in ct that happens when you have a body part that is very dense

where is beam hardening seen on a head ct

seen on the base of the skull through the petrous ridge area

what are the 2 benefits of filtering the low energy, long wavelength xray photons from the beam

reduces beam hardening (artifact) and reduces patient dose

what is volume averaging

how many photons your averaging in your pixel

how can volume averaging be reduced

by using a smaller pixel size (reducing the 3rd dimension) USING THINNER SLICES

what is raw data

all measurements that have been taken

not processed yet

what is image data

data included in the image after the computer has processed it and assigned a Hu

what is prospective reconstruction

images that come up right after scanning

what is retrospective reconstruction

the reconstructed image

uses raw data to make a new image

what is the scanning method that is used when the patient table moves continuously through the ct scanner during the scan

helical/spiral scanning

what material is the ct table made of and why

carbon graphite fiber because it doesnt absorb xray

what is the term for the the degree to which a ct table can move horizontally which determines the extent a patient can be scanned without repositioning

scannable range

what is the term for the process of moving the table by a specified measure

table incrementation

what is the smallest measurement of table movement that is required to be able to be reproduced

1 mm

what is it called when the technologist uses an anatomic landmark to set the table position

table referencing

which side is the right side when looking at an axial CT image

the right side is my left side when looking at it and vice versa

what image plane is this

axial

what image plane is this

coronal

what image plane is this

sagittal

which image orientation is acquired from the original ct scan

axial

which image orientations are created through post processing

sagittal and coronal