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Adv. Mod Unit 3

CT

QuestionAnswer
Which plane divides the body into inferior (caudal) & superior (cranial) portions? transverse (axial) plane
which plane divides the body into right and left portions? sagittal
which plane divides the body into anterior & posterior portions? coronal
What plane is the orthogonal plane? oblique
What are the major developments in xray beam and detector geometry called? generations
Which generation CT scanner used a pencil-wide xray beam & single detector? first
Which generation CT scanner used a wide fan beam that eliminated the need for translation? third
Which CT scanner generations have curved detector array? third and fourth
T/F: In fourth generation, the tube and detectors both move. false; the tube rotates but the detector don't
What are volume CT scanners? continous rotation of the xray tube while patient moves through the gantry.
Which scanners can slice up to 320 slices per tube rotation? multislice scanners
What are some advantages to multislice CT scanners? *shorter acquistion time *decreased amount of contrast medium *improved spatial resolution *improved image quality
What is the opening of a CT scanner called? aperture
What is the mounted framework that surrounds the patient called? gantry
What part of the CT scanner is made up of photodiodes coupled with scintillation crystal materials? detector array
How is a digital signal made from a CT scanner? xrays are converted into light, light is converted into electrical energy and then into digital signal
On multidetector units, what determines the slice thickness? the size of the detector row used
kv, mAs, pitch, field of view, slice thickness, table indexing, reconstruction algorithms, display windows are settings that are adjusted based on what? each patient
What does each pixel in a CT matrix represent? CT number
What is a voxel? 3D or volumetric picture element that represents the attenuation characteristics of the anantomy found in the voxel
What is another name for a CT #? hounsfield unit
What Hounsfield unit is water? 0
How is a Hounsfield unit/CT # created? by using a formula relating the attenuation coefficient of the tissue being imaged to that of water.
What is the mathematical unit that describes the shade of gray that is related to the attenuation characteristic in the voxel? CT #/ Hounsfield unit
What color does bone show up on CT? white
What is the hounsfield unit for air? -1000
As WW (window width) increases, what happens to the contrast? contrast decreases
As WW is narrower, what happens to the contrast? contrast increases
Pixels with CT numbers of -200 or lower are what color? black
Pixels with CT numbers of 600 or higher are what color? white
What does setting the window level determine? the midpoint of the range of CT numbers to be displayed
What does setting the window width determine? adjusts how many CT number are visible in the range
What range should the WL be for soft tissue anatomy? 30-60
As WL (window level) increases, what happens to the image display? the image gets dimmer
As WW decreases, what happens to the contrast? contrast increases
As WL decreases from +248 to -106, the image appears how? whiter
As WW decreases from 603 to 95, the contrast does what? increases
What is another name for scout? scanogram
What is a scanogram used for? used to select the range of the CT scan
What determines the amount of anatomy covered during a scan? pitch
What is the pitch to be considered undersampling? 2:1 a pitch higher than 1
What is the pitch to be considered oversampling? .05:1 a pitch lower than 1
What does it mean if the pitch is 1? table speed and slice thickness are equal; when the tube makes one complete rotation the distance that the table moves is the same measurement as the beam width.
Which image reformatting setting demonstrates contrast filled structures? maximum intensity projection
Which image reformatting demonstrates the outline of outer shell of the structures? surface shaded rendering
Name some specialized procedures done in CT. 3D reconstruction, CT virtual endoscopy, CT enteroclysis, CT angiography
What is the contrast media used in CT? iodinated, nonionic
What is checked before contrast is administrated? for possible poor renal function (creatinine)
In the lung windows, what kind of window is used? wide? narrow? wide
How do patients lay on the table for a Chest CT? supine with arms elevated above head
What is different when doing a Chest CT when the patient has possible cancer and a patient who doesn't? Patients who have a history of cancer, you want to scan thru the adrenal glands. For patient who don't have a cancer history, scan to the lung bases.
T/F: For cardiac studies and pulmonary embolism protocols, IV iodinated contrast is administered. true
For abdomen CT, what are your parameters to scan? diaphragm to iliac crests
For a pelvis CT what are the parameters? iliac crest to symphysis pubis
For a routine abdomen or pelvis study what are your mm per slice? 5-7mm
When you increase pitch, what happens to pt. dose? pt. dose decreases
thinner CT slices does what to pt. dose? increases pt. dose
T/F: the primary difference between each generation of CT scanners was the speed of the system. false; the difference was the number and arrangement of detectors
What are the three primary components of a computed tomographic system? *gantry *computer *operator console
What do the detectors measure in a CT system? attenuation of radiated tissue
The depth of the voxel is determined by what? slice thickness
CT numbers are a numerical scale that represent tissue _________. densities
The general CT number for white brain matter is_____. +45
The general CT number for blood is ____. +20
The general CT number for lung tissue is _____. -200
Which medium serves as a baseline for CT numbers? water (0).
Window width controls what? displayed image contrast
window level controls what? image brightness
Pitch is the relationship between _________ & ________. table speed; slice thickness
How must the intravenous contrast media be adminstered during a multislice CT scan? hand, bolus injection
T/F: Patient dose is higher for a CT scan of the head as compared with a routine skull series. true
T/F: the higher the pitch ratio during a volume CT scan, the greater the patient dose. false; the lower the pitch ratio = greater patient dose
Trauma to the skull may lead to a collection of blood accumulating under the dura mater is called what? subdural hematoma
What is the most common slice thickness range for a routine CT study of the chest? 5mm
Which CT generation scanner contains a bank of up to 960 detectors? third
Which CT generation scanner has 4800 or more detectors on a fixed ring? fourth
Which CT generation scanner was the first scanner with fan-shaped beam and 30 or more detectors? second
Created by: mokapis