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