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195 Cards in this Set
- Front
- Back
CT scan on lower extremity, ankle
what is the scan range |
start just above the tibial platform and end once through the calcaneous
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CT of ankle what are the window settings?
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350ww/50wl soft tissue and
2000ww/500wl bone |
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what position is a patient in for a CT of the ankle?
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supine legs flat on the table
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what is window width?
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contrast , shades of gray
determinines number of gray level displayed |
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what is window level
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mid point in gray scale
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what is the scan type of a CT of the ankle
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helical
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what is a topogram?
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also called: scanogram/sinogram/localizer
a localization image first image of examination low resolution low dose used for scan protocol design and treatment planning |
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scan range of a shoulder
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start just above the AC joint and end just below the scapular tip
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patient position for a shoulder
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supine with affected arm at side and unaffected arm above head
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reconstruction slice thickness for a shoulder
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1.25mm/ 0.625mm ( bone and soft tissue
2mm /2mm ( MPR) |
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reconstruction slice thickness for a ankle
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0.625/0.3mm ( bone and soft tissue)
2mm/2mm MPR |
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patient position for a CT of the hip
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supine legs flat on the table
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type of scan and type of topograms
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Topogram= AP/lateral
type of scan= helical |
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scan range of a CT of the hip
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start just above the SI jt and end approx 4 cm below the lesser trochanter
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recon slice thickness for a hip
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1.25mm/0.625mm ( soft tissue)
2mm/2mm MPR |
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scan range for a wrist
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just proximal to distal radioulnar jt end just proximal metacarpal joint
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what is pitch
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p=i/b
i= table index ( increment) per 360degrees b= beam width |
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windowing?
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manipulating gray level to provide optimal demonstration of different structures in the image
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what is a pixel
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each pixel contains information that the system obtains forms scanning. picture elment
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what is a voxel
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volume element slice thickness
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Hounsfield unit
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quantify the degree that a structure attenuates x-ray beam
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Scan Field Of View (SFOV)
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: determines the area within the gantry where raw data is acquired
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Display Field Of View (DFOV)
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determines how much and what section of the collected raw data will be used to create an image
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z plane
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thickness of the plane: determines the thickness of the slice
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what is the patient position for a pelvis/abdomen
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supine straight and flat arms raised over head
either feet first or head first |
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what are the recon slice thickness for abdomen/pevis
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5mm thickness/5mm intervals
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window settings for abdomen/pelvis
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soft tissue: 400ww/50wl
liver: 150 ww/70 wl lung 1500 ww / -700 wl |
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scan range for abdomen/pelvis
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start: highest point of diaphragm
end: below symphysis pubis |
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special instructions for abdomen /pelvis
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breathing: inspiration
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topograms for pelvis and abdomen
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AP, Lateral
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Patient position for Chest
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supine
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topogram for chest
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AP and Lateral
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scan type for chest
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helical
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scan range for chest
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start: just above lung apices
stop: just below costophrenic angles |
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recon slice thickness/interval for chest
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2.5mm thickness/ 1. 25mm interval
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window setting for chest
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soft tissue: 350ww/ 50wl
lung: 1500/ -70 |
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special instructions
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breathing: inspiration
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patient position for c -spine
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supine
head first |
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toopogram c-spine
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AP
lateral |
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scan type fror c spine
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helical
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scan range for c spine
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start: just above skull base C1
stop: mid T1 |
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recon slice of c-spine
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2.5mm thickness /1.25 mm intervals
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window setting of c spine
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soft tissue: 350 ww/50 wl
bone: 4000ww/400wl |
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position of patient for T spine
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supine with knees bent
arms raised over head |
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topograms for t spine
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ap
lateral |
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scan type for t spine
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helical
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scan range for t spine
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start: just above T1
stop just below T12 |
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recon slice thickness of t spine
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2.5 mm thickness /1.25 intervals
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window setting for T spine
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soft tissue 350ww/50wl
bone 4000ww/400wl |
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position of patient for L spine
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supine with knees bent
feet first arms above head |
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topograms of l spine
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ap
lateral |
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scan type for L spine
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helical
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scan range for l spine
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start just above L1
end just below s1 |
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recon slice thickness for L spine
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2.5mm thickness/1.25 mm intervals
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window setting for L spine
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soft tissue 350ww/50lw
bone 4000ww/400wl |
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patient position for neck
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supine
head first lower shoulders as much as possible |
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topogram for neck
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ap
lateral |
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scan type for neck
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helical
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scan range for neck
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start mid orbit
stop: mid clavicle, center on glabella |
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recon slice thickness for neck
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2.5mm/1.35,, intervals
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window setting for neck
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soft tissue 350ww/ 50wl
bone 4000ww/400wl |
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special instructions
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modified valsalva maneuver , puff checks
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what is the ct number for water
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0
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how many HU will contrast add to an image
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range btw 40-73
approx 50 |
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which plane corresponds with slice thickness
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z
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what is the ww and wl of soft tissue
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350ww/50wl
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what is the ww and wl of bone
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1800ww/400wl
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what is the ww and wl of lung
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1500ww/-700
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what is the ww and wl of liver
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150ww/30wl
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list 3 scans required for HRCT
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multi phasic so
inspiration supine expiration supine prone inspiration |
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are all CT injections delivered through venous IV
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Yes all hrough venous access
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contrast appears in the right atrium first
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yes
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how can CT contrast be administered
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IV
enema rectal oral mouth |
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scan location for Knee
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above patella
below fibular head |
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laser light localization are assigned to what body planes
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midcoronal and mid sagittal
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can extremity CT scan be augmented?
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yes
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why are BUN and creatinine level assessed prior contrast CT study
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to ensure patient is within safe range - able to excrete the contrast from the body
ensure renal function is adequate |
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what is BUN
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is a measure of the ura nitrogen in the blood and inidciation of how well the kidney is able to excrete urea
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what is normal adult BUN
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btw 8 o 25 mg/100ml
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what is the normal range for creatinine with adults
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0.6 to 1.5mg.dl
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what does elevated BUN and creatinine levels inidicate
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patients with elevated levels are at a greater risk of having adverse effect from contrast bc they are not able to process and excrete contrast- renal system could be damaged by contrast
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patient preparation for patient taking metformin ( glucophage ) for non insulin dependent diabetes
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need to stop taking their med 48hrs post study
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what is eGFR
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test to screen for and detect kidney damage and monitor kidney status.
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difference between axial and helical
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axial: stop start
helical continuous slinky |
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critique a CT image by:
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spatial resolution
low contrast resolution temproal resolution |
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HU
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hounsfield units = density values=quantify the degree that a structure attenuates an xray beam
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HU of air
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-1000HU
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the three process of CT
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data acquisition
image reconstruction image display |
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how much do 2 tissues need to differ to be visible
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10HU to be visible on CT
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size of needle routinely used in CT for admin of contrast
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min of 20g IV
if patient has established 18g line use it |
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CTA imaging needle size
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min of 18g ex 5-6cc/sec
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types of contrast
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positive: barium and iodinated
negative: air, CO2, |
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bolus triggering
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HU of ROI is measured before contrast injection when ROI reaches peak value +/- 50 HU scan starts
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are all positive contrast media in ct diluted?
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yes
why? BC if not then the density of CM is high enough to cause streak artifacts |
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what is a test bolus
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a pulmonary mini bolus injection is preformed to determine an individuals delay to scan time
- ensure IV is functioning proporely |
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saline flush is what?
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-flushes out contrast material that would otherwise be left behind in the injection tubing
- it elminates extra step of cleaning vascular access site - pushes contrast bolus forward - creates more desirable bolus shape - reduces artifacts - increases amount of contrast available for use in image acquisition - decreases amount of contrast needed |
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advantages of CT extremity:
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display images x sections
images bilaterally for comparison displays bone and soft tissue better detail- contrast ability to create 3D recon/multiplane enhances surgical planning |
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is IV contrast used in extremities?
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not often but can be
rate slower IV site opposite to injured site |
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why do a ct of abdomen and pelvis
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to elevate all organs and most vessels
indiciations: tumors carminoma staging carcinoma/met lymphoma/lymphadenopathy AAA dissections unexplained weight loss appendicitics pancreatitis |
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scanogram
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initial scan
lower dose starts where laser light is can be done in 1 or 2 planes used for planning study |
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what are liver window settings?
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are more narrow than soft tissue ( short scale contrast) to improve visibility of subtle liver lesions
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what are lung windows
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are set to show the air filled lungs clearly
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bone windows
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make all soft tissue nearly uniform shade but bone is very bright and clearly seen
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what is a liver window?
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150ww/30wl
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what is a lung window?
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1500ww/-600wl
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bone window
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1800ww/400wl
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breathing instructions?
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help hold patient still during exam, reduce movement
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whta type of scan is a liver CT
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liver multiphasic
arterial phase- scan delay up to 35 sec venous phase- scan delay 65sec delayed scan 600sec past venous phase suspect hemangiomas |
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what is the slice thickness for liver CT
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5mm
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routine abdomen pelvis
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indiciations: suspected abdominal mass/tumor staging , abcess
scouts: AP /Lateral scan type: helical start: above diaphragm end: below symphysis pubis inspiriation IV : DFOV: 38cm window: soft tissue 400ww/50wl liver : 150ww/70wl lung : 1500ww/-700wl recon slice thickness/interval: 5mm/5mm |
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arterial liver
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three phase liver for suspected hemangioma, repeat gp 2600 sec after IV injection
indication: elevualation of suspected hypervascular hepatic tumors, mets from carcinoid, carcinoma scout: AP/lateral scan type : helical start: above diaphragm end: through entire liver- iliac crest inspiration IV 125ml at 4ml/s; 50 ml saline at 4.0ml/s scan delay 35 second DFOV 38cm window: soft tissue 350ww/50wl liver; 150ww/70wl |
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venous phase liver
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start above diaphragm
end : iliac crest inspiration no additional IV contrast scan delay -65dec soft tissue 350ww/50wl |
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CTV
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look at venous structures
100ml 4.oml/30 sec delay skull base to vertex |
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what are indication for a CT of the thorax:
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pulmonary embolism
pulmonary nodules( no contrast) infection mass trauma bronchietasis inhalation interstitial disease emphysema coronary artery disease |
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CT of the thorax:
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supine
may require IV contrast may not scout AP/lateral helical inspiration start: above apices to below costophrenic angles for chest and abdomen- diaphragm to below crest |
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for a CTA for pulmonary embolism what way to scan
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inferior to superior from lowest hemidiaphragm to lung apices
this prevents artifacts for contrast and reduces heart motion |
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window for CT for thorax:
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350ww/50wl for soft tissue
1500/-700wl lung |
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flow of blood through the heart
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start at lung apices
1 st. end just below costophrenic angles 2nd. above abdomen recon: 2.5mm thickness/1.25 mm intervals - overlap |
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CT thorax detectors:
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detector rows: 16, 64
detetctor width 1.25 0.625 coverage 20 40 less detail more detail |
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pulmonary embolism CTA
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suspected pulmony embolism
Scouts: AP LAteralshould start above lung apices adn extend to below tibial plateau so that tehy can be used for both gp 1& 2 arterial scan: scan helical start: hemidiaphragm to apices( inferior to superior) IV : 120ml total - split bolus DFOV 38 window : 700ww/180wl vascular 1.25mm/0.625mm |
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high reso chest HRCT
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maybe in a series of 35
inspiration supine ( helical) expiration supine inspiration prone recons: 1.25mm interval feet first, supine, arms above head |
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high reso chest
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indications: asbestos, inhalation, diffused pulmonary disease
scout : AP LAteral helical start: lung apices- to below costophrenic angles IV : none DFOV 38 lung window 1500ww/-700 |
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CTA aorta:
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may be gated
indications: blunt trauma, aortic dissection , aneurysm gp 1 unenhanced AP/Lateral helical IV none inspiration DFOV 38 350ww/50wl soft tissue recon 5.0mm/5.0mm start: 2cm above aortic arch end: 2cm below celiac artery gp2: gated arterial scan cardiac helical AP/lateral just above lung apices- 2cm below celiac artery IV: 100ml total DFOV 25 vascular ww: 700/180wl 1.25mm/1.25mm |
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CT spine
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indiciations: disc herination
spinal stenosis spinal infection trauma intraspinal tumour |
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C- spine
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head fisrt
laser light at glabella scan above skull base to T1 0.625x32=20mm 0.625x16 =10mm recons: 2.5mm/1.25mm intervals DFOV 13cm smaller = better detail scan plane- transverse no tilt on gantry |
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can you use head hold when patient is on spianl precautions?
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no!
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sinus screening CT is used for ?
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sinus screening is intended as an inexpensive accurate and low dose radiation method for confirming the presence of inflammatory sinonasal disease
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indicator for sinus ct
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recurrent or chronic sinusitis
scout: lateral scan type: axial scan plane: coronal start: mid sella end: through frontal sinus IV none gantry angle: perpendicular to the orbital meatal line DFOV 16 |
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soft tissue neck
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vascular abnormality
AP and Lateral helical transeverse mid orbit - clavicular heads IV: 125ml at 1.5 ml/s split bolus 1st injection 50ml 2minute delay 2nd injection 75ml scans initiated 25 secs after start of second injection angle on gantry parallel to hard palate DFOV 18 |
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if doing a soft tissue neck and patient has dental work how should the scan be changed
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scan should be split into 2 groups and angle to reduce artifact
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c spine
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fracture/dislocation
AP/Lateral helical transverse start: just above skull base end: T1 no angle on gantry DFOV 13 ww: soft tissue 350ww/50wl 2.50mm 1.25 mm |
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Tspine
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fracture dislocation
AP/lateral helical transverse above T1- below T12 no angle on the gantry DFOV 16 350ww/50ww soft tissue 2.5ww/1.25wl |
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Lspine
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fracture/dislocation
supine- knees bent feet will enter scanner first, arms are raised over head lazer light xiphoid process ( t9-T10) AP/Lateral- scout L1 to just below S1 helical transverse just above L1- below S1 DFOV 14-16 350ww/50wl 0.625x16=10mm 0.625x32mm=20 2,5mm/1.25mm |
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spine ct are reformatted in
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coronal and sagittal
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CTA spine
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localized of the shunt of spinal dural arteriovenoous fistulas blunt trauma
AP/lateral helical transverse Arterial phase: start: skull base end sacrum IV 120ml DFOV 20 350ww/50wl at 6ml/s scan delay = bolus tracking place ROI in the aorta just below diaphragm manually trigger when enhancement value approaches 125HU 1.25mm/0.625 |
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t spine position
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supine knees bent arms raised above head
lazer light at 2" above jugular notch T1 aquire at 0.625x16=10mm or 0.625x32=20mm may not scan full T-spine |
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windowing for Spine-
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will cange depending on exam
soft tissue 350ww/50wl bone 4000ww/400wl |
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myelography
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intrathecal contrast -fluoro admin
sacn delay of 1-3hr to allow contrast to dilute patient maybe required to roll 3x before CT visualize spinal cord some patients can not have can MRI demon to CSF leaks |
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CTA
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study arterial vessels Av fistucles AVM
blunt trauma, vascular injury scan skull has to sacrum 2 sets of scans 1st scan > delay bolus in aorta level of diaphragm 2nd delayed scan immediately after 1st 120ml of contrast at 6ml/s measure DFOV to body habitus but when doing spine don't need edge of body - mag DFOV to just include spine |
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CT neck
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supine, head first depressed shoulders as much as possible
angle the gantry parallel to hand palate center on glabella scan mid orbit to clavicle extend chin upDFOV include as soft tissue mod valsala maneuveur |
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CT neck
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contrast enhancement contrast of the neck allows muscosa lymph nodes pathological tissue to enhance split bolus is used
1st bolus 50ml given scan at 2min this allows delay for structure that are slower to enhance scan 2nd bolus ( 75ml) given 25sec after the 2min scan allows for all vessels to be fully opacified |
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CTA head
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can be used to evaluate and meaure stenosis of carotid, arteries stenosis of vertebral arteries
less invasive the traditional angiography CTA has arterial imaging |
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CTV
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ct venous
used to visualize venous anatomy some protocols used except images are acquired when contrast is in venous |
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CT head
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indication:
stroke TIA hemorrhage trauma tumors AVM thrombosis aneurysm headache/seizures mass/lesions/hearing loss unknown /surprieses |
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patient position for CT head
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patient is supine on table head placed in head in holder
if coronal position needs to be achieved patient can extend chin and drop head as far as possible a patient may be placed prone which requireds special holder patient head first into gantry patients OML parrallel with gantry ( tilt) DFOV 23cm |
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routine brain
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axial, scan below base of skull to above vertex
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posterior fossa
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axial scan
foramen magnum to above petrous ridges transverse foramen magnum- through petrous ridges angle gantry parallel to IMOL DFOV 23 140ww/40wl |
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temporal bone
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axial scans
AP Lateral transverse just below mastoid process just above Petrous ridge Angle gantry parallel to IMOL DFOV 9.6 ww 4000ww/400wl 0.625mm/0.625mm |
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scans of sella turcia is usually preformed
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usually in MRI
axial CT done bc: pituitary mass, microadenoma, below sella floor to above sella dorsum DFOV 14cm transverse angle gantry parallel to IOML 350ww/50wl 1.25mm/1.25mm |
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helical scanning of the head is done is what exams/
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CTA
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window settings for head include
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soft tissue brain 160ww/40wl=slice inferior posterior fossa
soft tissue brain 100ww/30wl= slices above posterior fossa bone 2500ww/60wl blood 200ww/60wl |
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intracerebral hemorrhage
stroke |
after stroke edema progresses and brain density decreases proportionately serve ischemis results in a 3% increase in intraparenchynal water w/in 1hr this corresponds to 7-8 HU decrease in brain density
there is 6% increase in water @ 6hrs |
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ct sinuses
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coronal position
prone/supine scan from mid sella through frontal sinuses center perpendicular to the OML scan anterior to posterior head positioned as coronal as possible coronal position - axial acquisition -stop start soft tissues light see soft tissue better |
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Ct sinuses demostrates what?
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air fluid levels and help for planing for surgery
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facial bones
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helical below mandible to above fromtal sinuses
angle in IOML axial jaw elevated everything in same place can angle gantry more if patient cannot extend chin |
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CTA vascular study
circle of willis |
indication: locate cerebral aneurysm
helical transverse scan 2 sets of images image arteries 1. non contrast head 2. arterial phase CTA 80 ml 4.0ml/s start above frontal sinuses end below skull base DFOV 25 140ww/40wl posterior fossa 90ww/35wl vertex |
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why must a CT head be started prior to starting a blood thinner?
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rule out intracanial hemorrhage
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CTA what type of scan is used and why
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helical so flow of contrast can be mapped-viewed
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axial scan is used because ?
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allows for gantry tilt
can reduce radiation exposure because can gantry and reduce exposure to the eyes |
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CT of l-spine the laser light is
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xiphoid
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ct chest is done in 3 series why?
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to demonstrate expansion and contracting lungs and their function units aveolar /bronchial function
as well as looking for any air that has escaped lungs - with cavity |
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CTA spine what is the injection rate
|
CTA spine
6ml/sec |
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what is the delay between contrast injection and scanning for intrathecal contrast admin
|
1-3 hours to allow the contrast material to become sufficiently dilute
if you don;t wait that time then intradural structures may be masked. roll patient before scanning is recommended to mix contrast |
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what are the goals for a CTA for cercivocranial vascular evaluation
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1. to accurately measure stenosis of teh carotid and vertebral arteries and their branches
2. to evaluate the circle of willis 3. detect other vascular lesions such as dissections or occlusion |
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how can you improve visualization of intradural structures?
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intrathecal administration of water soluble contrast material
ie helpful for diagnosis of degenerative disc disease or extradural neoplasm |
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when is CT superior to MRI for spine scans?
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in evaluation of bony abnormalities
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how to limit motion while doing a foot?
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foot holder and tapping the foot to prevent motion
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HRCT is used for?
|
evaluation of lung parenchyma in patient with diffuse lung disease such as fibrosis and emphysema
usually a series of scans usually done on full inspiration but addition expiration images can be done - better dipict bronchiolitis and air trapping |
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HRCT protocol
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is done with fast acquisition and think section ( 1.5mm or less)
reduces motion and increases spatial resolution DFOV should include only lungs field volumetric HRCT replaced HRCT axial addition prone images may be taken to help differentiate actual disease from densities owning to the effects of gravity that mimic disease |
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colongraphy
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evaluation of the colon
AP lateral helical just above diaphragm end : at lesser trochanters inspiration rectal contrast with air DFOV 38cm 350ww/50wl soft tissue 2.5mm/1.25mm recon slice |
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When imaging a soft tissue neck which of the following structures would you angle the gantry to?
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Hard palate
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Which of the following procedure(s) requires the use of a split bolus?
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soft tissue neck
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hat is the DFOV for a routine CT head?
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23cm
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What is the scan location for a CTV head?
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Below skull base to above vertex
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The anatomy demonstrated in CT head images predominately is determined by:
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angle of the gantry
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Provide 5 indications for performing a CT Head.
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stroke, TIA, hemorrhage, trauma, tumors
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What is the scan range for a T-spine?
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Above T1 to below T12
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A patient requires a CT myelogram. Which department will inject the contrast?
|
fluoro
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Why would a patient require a myelogram?
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CSF leak
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What slice thickness are C-spine images acquired with a helical scan type reconstructed to?
|
2.5mm
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What interval thickness are C-spine images acquired with a helical scan type reconstructed with?
|
1.25mm
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why are the patients arms raised above the head during chest or abdomen scans?
|
reduce the artifacts on images
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Why is the patient asked to drink contrast medium prior to an abdominal CT exam?
|
To differentiate stomach from surrounding tissues
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window settings
|
Soft tissue – 350ww/50wl,
Bone – 1800ww/400wl, Liver – 150ww/30wl, Lung – 1500ww/-700wl |
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If a patient receives IV contrast which chamber of the heart will the contrast enter first?
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right atrium
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Which of the following is NOT considered an adverse reaction to contrast medium?
a. Swelling face b. Warmth Correct c. Decreased Level of Consciousness |
warmth
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For a CT abdomenpelvis which of the following is your start and end location?
|
Above diaphragm to below symphysis
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routine chest:
|
includes both soft tissue adn ling windows to evaluate mediastinal structures as well as lung
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CTA chest
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indications: pulmonary embolism
less invasive and more specific to VQ scanning major role in detection and of both acute and chronic thromboembolic disease CTV may follow CTA to asses for venous thrombosis within the pelvis and lower extremities |
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how to mark extrimities ( hand, wrist forearm, elbow?)
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place radiopaque markers 1 for left and 2 for right on the extremities at one edge of the scan
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CT shoulder position?
|
supine and arm to be examined is rest downward along body and opposite arm is extended above head
double contrast : air and iodinated contrast |
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ct of the knee must include?
|
only one knee with patella, both femoral condyles, and proxiaml tibia through fibular head
legs extended, knees side by side and feet enter gantry first |
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three positions for writs
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1. arm over head
2. sit or stand at far side of the scanner and extend arm into the scanner 3, writs rests of abdomen ( less favorable) |
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CT arthrography is used to see what?
|
evaluation of the joint capsule , finding loose bodies within joint
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lower/upper extremity position
|
lower: usually feet first , supine
upper: supine, head first |