CT SCAN Flashcards by MA. ANNE JARDINIANO

defined as the process of creating transverse, axial, cross-sectional image of human body through the basis and measurement of attenuation

computed tomography

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to cut/slice

tomos

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to write about/to produce images

graphien/graphia

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CT scan was originally ______ upon the invention of 1st generation on 1970s

CAT scan

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process of weaking the xray beam as it passes through matter which occurs through 2 distinct phenomenon

attenuation

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attenuation is primarily measured through ____ and _____

half value layer and linear attenuation coefficient

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is the measurement for the amount of x-ray intensity that is absorbed as it travels through matter

denoted by the Greek letter μ with a unit of with a unit of cm^-1

linear attenuation coefficient

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also known as CT numbers

is the numerical measurement that account to the radiodensity of a material

hounsfield units

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amount of differences of a tissue or organ processes attenuation of the xray beam with matter

differential absorption

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3 general steps in CT

data acquisition
image reconstruction
image display, manipulation, storage and communication

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3 goals of CT scan

to overcome superimposition of anatomy

to improve contrast

to record small differences in tissue

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mathematician who invented the algorithm

Allan McLeod Cormack

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engineer who designed CT hardware

Godfrey Newbold Hounsfield

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collection of data after a successful exposure

collection of remnant radiation

translation/sweep

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translate-rotate geometry

3-4 detectors

pencil beam configuration

3-5 minutes scan time/translate

for brain scanning

1st Gen

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1st Gen also called as

Mark 1
Brain Tissue
EMI

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standard matrix size

512 x 512

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rows and columns of pixel

image matrix

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translate-rotate geometry

narrow fan beam

5-30 detectors

20s to 3.5 minutes scan time

Dr. Robert S. Ledley

for whole body scanning

2nd Gen

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2nd gen also called as

Automated Computerized Transverse Axial Scanner (ACTAS)

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2nd gen CT has disadvantage of wide beam divergence, penumbra and scattered radn

the solution is _____

bow tie filter

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rotate-rotate geometry

wide fan beam

750-1000 detectors

0.35s-10s scan time/slice

3rd Gen

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disadvantage of 3rd gen

ring artifact

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hyperdense concentric ring in the center of CT image caused by the misalignment of xray detectors

ring artifact

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solution for ring artifact

xray detector calibration

rotate-stationary geometry wide fan beam detector ring >1s per slice scan time

4th Gen

due to decreasing distance between xray tube and px, the disadvantage of 4th gen is ____

increased radn dose

5th gen also called as

Ultrafast CT Electron Beam CT Heart Scanner

stationary-stationary geometry 4 stationary xray detector rings 50-100ms/slice high temporal resolution

5th Gen

5th Gen was invented by

Andrew Castagnini

spiral/helical geometry dual xray tube source dual curvilinear detector array

6th Gen

6th Gen was invented by

William Kalender and Kazuhiro Katada

scanning large amount of anatomy for short period of time

spiral/helical geometry or volumetric scanning

spiral/helical geometry cone fan beam flat panel detectors capable of volumetric scanning

7th Gen

technology that allows uninterrupted power supply and transfer of electrical information

slip ring technology

7th gen also known as

Multi Slice CT or Turbo Charged Spiral CT

most advanced CT scan machine that provides us with the dual source - dual energy which uses both high and low emission spectrum

spectral CT technology

4 major components of CT

gantry control console px couch computer

largest component of CT machine

gantry

tilt capability of gantry

15-30

CT xray tube called as

straton

heat loading capacity of straton xray tube

6-8 MHU

bulky and positioned outside the CT gantry and capable of producing 4% voltage ripple waveform and 96% voltage efficiency

three phase twelve pulse high voltage generator

compact and can be positioned inside the CT gantry and capable of producing less than 1% of voltage ripple waveform and almost near 100% voltage efficiency

high frequency high voltage generator

collects the remnant radn that exits the px body

xray detectors

profile for remnant radn

attenuation profile scan profile projection profile

profile for slice thickness

slice sensitivity profile

profile that pertains to the radiation dose received by the px during scan

dose profile

2 types of xray detectors

gas filled and scintillation

detector that uses a direct conversion method of generating electronic signals direct ionization event that occurs between the pressurized gas and remnant radiation

gas filled detectors

detectors that uses a indirect conversion method of generating electronic signals excitation event that occurs between a photoreactive crystals and remnant radn

scintillation detectors

4 photoreactive crystals of ssd/scintillation detectors

bismuth germanate oxide - PET cesium iodide - fluoro cadmium tungstate - CT sodium iodide - gamma cam

patient couch was made from ____ and ____

wood and carbon fiber

are the terms that are used to describe the movement of px couch towards the aperture

table feed table increments table speed

is the ratio between 1 full gantry rotation over table movement (mm) ratio of table speed/feed to slice thickness used to describe the table movement exclusively used for 6th and 7th gen

table pitch

if the pitch is >1 - the speed of indexing is ___

fast

most ideal value of table pitch should always be equal to __ to __

1 to 1.5

a system subcomponent collects the raw electrical signals from the xray detectors and converts it into a binary data for image reconstruction and processing

data acquisition system

serves as the link between the RT and CT components

computers

2 storage and communication

picture archiving and communication systems (PACS) health level seven (HL7)

used as a guide/planning tool for placing the locator and the coverage of the entire body under examination

localizer/preliminary scan scanogram topogram surview

scanning mode that is used for CT guided biopsies and dependent on RT

axial sequential mode or step and shoot scanning mode

scanning mode that is used for reducing motion/misregistration artifact also used in CM studies also called as volumetric scanning

helical/spiral scanning

is a mathematical process by which it is a method of constructing new data points based on the present range of discreet data set

interpolation

in image formation, it denotes the path of xray photon from the xray tube towards the detectors

ray

in image formation, it is the detection of individual rays and measures attenuation

ray sum

in image formation, it denotes a complete set or group of ray sum/s

view

artifact that is only seen when back projection algorithm is used lines that resembles grid like pattern/star like pattern all over the CT image

star pattern artifact

3 algorithms

back projection filtered back projection iterative reconstruction

algorithm that was already obsolete due to the existence of star pattern artifact

back projection algorithm

algorithm used in PH setting has convolution filter/kernels filter that removes the star pattern artifact

filtered back projection algorithm

plays an important role in decomposing bundles of digital frequency signals into its individual signal components also used to located and map signals for image processing and reconstruction mathematical function that was introduced by Jean Baptiste Joseph Fourier

fourier transformation

computer algorithm that is used to suppress filter individual digital signals such as high/low frequency signals to improve the image quality of CT image

convolution or kernel

high frequency filters that filters high frequency signals also called as _____ pass filter that allows transmission of low frequency signals

low pass filter

low frequency filters that filters low frequency signals also called as _____ pass filter that allows transmission of high frequency signals

high pass filter

algorithm that works through an assumed image and raw data from the scan profiles, it is then compared with the original image the differences between the actual and calculated projection are then use to updated the image for improved quality and suppression of image noise

iterative reconstruction algorithm

4 types of CT data

measurement data raw data filtered CT data CT image data

remnant radn data derived from measurement of attenuation

measurement data

data that is derived from the DAS

raw data

data that is derived from the convolution process

filtered CT data

finished CT image data derived from image reconstruction

CT image data

represents hounsfield units 2 dimensional in nature

pixel - picture element

is a grid that is formed by rows and columns of pixels

image matrix

represents slice thickness 3 dimensional in nature

voxel - volume element

combination of 2 or more CT data resulting into less accurate color representation

volume averaging

maximum diameter of the area of the scanned object that is represented by the reconstructed image

FOV - field of view

FOV that determines the area of the gantry which the raw data is acquired area of the aperture where raw data is acquired determines the number of xray detectors that would be activated

SFOV - scan field of view

FOV that determines the amount of raw data that would be needed for image reconstruction

DFOV - display field of view

is a post processing technique that is use dto adjust the CT image's different shades of gray

window settings

window settings that controls the HU values that are displayed as shades of gray midpoint value for shades of gray controls brightness

window level

window settings that determines the number of shades of gray that will be included in an image display controls scale of contrast

window width

measurement of radiation dose in single CT scan procedure

CTDI - computed tomography dose index

phenomenon by which the amount of radiation exposure is no longer related to the perceived image quality

uncoupling effect

process of creating images in a plane/orientation

image rendering

2D image rendering technique which uses pre-determine value of high or low intensity pixels and voles to create an image has maximum and minimum

intensity projections

act of suppressing data

segmentation

2D image rendering technique which uses combination of the acquired transverse slices to generate planar images of the body

MPR - multiplanar reformation

3D image rendering technique which uses combination of the pre selected pixels and voxels/values of the chosen anatomic structure which then forms surface 3D recon skeletal system

SSD - surface shaded display

3D image rendering technique which uses all of the pixel and voxel values of the chosen anatomic structure (no data loss/suppression) which then forms a volumetric 3D image

VRT - volume rendering technique

ability to explore or cut through 3D anatomy

fly through feature

3 resolution

spatial - xray, mammo contrast - mri, ct temporal - utz, fluro

resolution that has ability to resolve small objects that are laying very close together as separate objects

spatial resolution or detail

resolution that has ability to resolve or differentiate between objects that have the same densities as their background

contrast resolution

is the ability of the scanner to yield the same amount of HU from the region of interest towards the periphery of a homogenous object frequency: daily

uniformity

it is the standard deviation of a large number of pixels that were obtained from the water bath frequency: daily

noise

it refers to the relationship between the LAC and hounsfield units frequency: semi-annual

linearity

the LAC value of the water in a phantom should bear a ______ value given by the scanner

zero LAC

it refers to the radiation intensity output of the scanner, if it is compliant with CTDI set by the ACR standards uses CTDI phantom/pen dosimeter

radiation dose

it refers to the accuracy of slice sensitivity profiles being projected by the CT scan image uses ramp, spiral or step wedge in a phantom frequency: semi-annual

slice thickness accuracy

3 physics based artifacts

photon starvation partial volume averaging beam hardening

2 scanner based artifacts

tube arcing ring artifact

2 patient based artifacts

ghosting artifact metallic artifact

scanner based artifact that occurs when there is a undesired surge of electrical current inside the xray tube housing main cause of xray tube short circuit streaking in appearance throughout the entire DFOV

tube arcing

solution for tube arcing artifact

tube replacement

scanner based artifact that occurs when there is a misalignmnet of xray detectors appears as concentric rings in the center of DFOV occurs in 3rd, 6th and 7th gen

ring artifact

solution for ring artifact

xray detector calibration

physics based artifact that occurs when there is an insufficient amount of xray photons that reaches the xray detectors appears as white noise/streaks in highly attenuating structures such as bones

photon starvation artifact

physics based artifact that occurs when a polychromatic beam experiences attenuation from the organ that is being imaged appears as dark streaking lines near a dense anatomic structure

beam hardening

physics based artifact that appears as cupping artifact in which the CT numbers obtained in the center of the object are lower than the periphery

beam hardening

physics based artifact that occurs when increasing slice thickness over a region of anatomy that is small produces less accurate representation of image due to the confinement of more than one data attenuation profile inside the voxel

partial volume artifact

patient based artifact that occurs when there is an uncontrolled voluntary and involuntary motion that was exhibited by the patient appears as shading, ____ or blurring

ghosting/motion artifact

patient based artifact that occurs when there is a presence of metal in the SFOV which attenuates the xray beam star streaking or sun burst in appearance

metallic artifacts

2 CM delivery techniques

drip infusion technique bolus technique

CM delivery technique that uses the force of gravity to deliver IV CM slow delivering

drip infusion technique

CM delivery technique where the IV CM is delivered in a rapid injection rate

bolus technique

bolus technique where enhancement peaks are non-uniform and operator dependent also non reproducible

hand bolus technique

bolus technique where enhancement peaks are uniform and machine dependent also reproducible

mechanical injector technique

2 methods of scan delay

test bolus technique bolus tracking technique

method of scan delay that is used to determine the length of time from the injection of CM to peak enhancement in the organs 5-10 cc

test bolus technique

method of scan delay that uses a bolus of cm to start a scan uses a low radiation dose scans to monitor the progress of contrast enhancement in the body

bolus tracking technique

3 phases of CM enhancement

arterial phase venous phase delayed phase

3 laboratory examinations in patient considerations

serum creatinine eGFR PTT/PT

2 px history in patient considerations

hx of asthma hx of allergies

2 premedications in patient considerations

corticosteroids antihistamines

CT SCAN Flashcards

(134 cards)