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118 Cards in this Set
- Front
- Back
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How are CT axial images viewed ?
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- as if you were at patients feet, looking towards head
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How are CT coronal images viewed?
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-as if you were looking at the patient in front of you
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How are CT sagittal images viewed?
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as if you were looking at the side profile of the patient in front of you
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X plane?
Y plane? Z Plane? |
Axial/ Transverse
Coronal Sagittal |
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What do you need to do for CT patient prep?
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• Exam initiation (requisition)
• Protocol selection • Communication • Medical history (patient, screening form) • Laboratory values • Intravenous set up |
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What to expect on Requisition?
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• procedure request by physicians, or nurse practitioners (NP)
• received by clerical staff and entered into the booking system—errors can/will occur • ensure the original req is present for radiologist protocol to avoid any scanning errors |
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Protocol Selection
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• determined with use of requisition and patient clinical information
• Radiologist has final say • Technologist may ask for clarification if uncertainties arise |
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Communication and CT
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• listen- empathy concern
• explain • non verbal communication- mixed messages • barriers- language misreading body language, selective hearing, assumptions, cultural differences |
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Patient Education
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• at a minimum, the technologist should describe
o how the procedure is carried out o the approx. length of procedure o whether contrast agents, will be administered • if Yes, then an explanation of how they will be administered and any potential side effects is required o what is expected of the patient o any follow up necessary after the examination has been completed |
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Habits to avoid
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• don’t use false reassurances
• don’t ignore a patients wishes • don’t speak to them like you are talking to a child • don’t assume that a non responsive patient cant hear • don’t carry on a separate conversation with a coworker while patient is present • don’t think being professional means being cold • don’t blame the patient • don’t use abbreviations or medical lingo |
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Habits to adopt
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• be a good listener
• use focused questions • use the patients name • use touch to comfort and be aware of nonverbal messages • develop rapport with patient |
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Why take medical history/screening form?
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• provides diagnostic info for the radiologist
• ensures patient safety |
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Renal Functions
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• eGFR- glomerular filtration rate (how much blood passes through kidneys per minute) over 60 is good
• calculator in moodle- patients age, race and sex are factors • Serum Creatinine- measures creatinine level in blood • BUN- blood urea nitrogen • Previous iodinated CM- higher or lower values • P. 113 lab values 114 value tables |
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Setting Up IV
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• pull the caps off the IV bag and the drop chamber and connect them together
• lock down the roller clamp and squeeze the drip chamber once or twice to patially fill it • now open the roller camp and let the saline fill the IV tubing |
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Size needles and amounts of CM
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• routine CT imagin
o use a minimum of 20 g IV o if patient has a patent 18 g established, use it • CTA imaging o use a min 18g IV for a larger volume injections o if unable to attain an 18g IV a patent 20G IV may be utilized |
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Ways of administrating CM
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• Drink it
• Eject it • Enema it |
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Types of CM
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• positive
o barium o iodinated • Negative o Room air o C02 o Normally occurring air in body |
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Purpose of CM
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• CM enhances the visual difference between two structures in an image
• CT can differentiate between two structures that are 10 HU difference • CM can add a difference of 40-75HU • Abdomen has many organs structures which are very close in density o So CM is used to differentiate from pathology |
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Prep of CM in CT
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• all positive CM in CT is diluted- number one rule
o if not , density of CM is high enough to streak artifacts • 30cc of telebrix to 500 cc water |
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Contrast in the Colon
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• patients drink dilute CM at timed intervals
• approx. volume 1000-1500 ml o 3 hours o 1 hour o immediately before scan |
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Why test Bolus?
(romans p.161) |
• a preliminary minibolus injection is performed to determine an individuals delay to scan time
• ensures IV is functioning and that it has not gone interstitial |
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What is Bolus Triggering/ Tracking?
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-HU or ROI is measured before contrast, injection started and when ROI reaches peak value +/- 50 HI, the scan starts.
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Saline Flush
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• Flushes out contrast material that would otherwise be left behind in the injection tubing
• It eliminates the extra step of clearing the vascular access site of residual contrast after injection • Pushes the contrast bolus forward, may create better bolus shape • Increases amount of contrast available for use in image acquisition and may reduce artifact • Decreases amount of CM needed |
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Side effects to CM/Saline Flush
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• warmth
• funny taste • few hives • minor itchiness |
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Adverse Affect of CM
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• major hives
• breathing problems • LOC • Swell of face • Previous reaction to CM |
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Advantages of CT on extremity?
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• display cross sectional images
• image bilaterally for comparison • displays bone and soft tissue with one scan • better detail (contrast) • ability to create 3D and multiplanar images (sagittal and coronal) from axial images • enhances surgical planning |
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what window settings are acquired for bone?
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2000ww/50wl
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Soft Tissue
(can be reconstructed) |
350 ww/50wl
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Is IV contrast normally used for extremity?
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No!
-can be when looking specifically for other indications o Eg. Injection tumor o Rate? lower o Iv Site? IV on opposite extremity (R versus L) |
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CT Patient Position on Hip
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Patient Supine with legs extended- flat on table
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CT topograms for hip
Scan Type? |
AP and lateral
Helical |
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Scan Range for CT Hip?
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Start just above SI jts and end approx. 4 cm below lesser trochanters
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Recon slice thickness/ interval for CT hip
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1.25mm/0.625mm (soft tissue/bone)
2mm/2mm (MPR) |
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Window Setting CT hip
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350ww/50wl soft tissue
2000ww/500wl bone |
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Patient Position CT ankle
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Patient Supine legs extended flat on table
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Topogram for CT ankle
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AP and Lateral
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Scan Type for CT ankle
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Helical
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Scan Range for CT ankle
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STart just above tibial plafond joint and end once through calcaneus
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Recon Slice thickness/ interval for CT ankle
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0.625 x 0.3mml (bone/soft tissue)
2mm/2mm MPR |
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Window setting for CT ankle
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350ww/50wl soft tissue
2000ww/ 500wl bone |
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Patient position for CT shoulder
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Patient supine with affected arm at side, opposite arm above head
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CT Shoulder topogram
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AP and lateral
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Scan Type for CT shoulder
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Helical
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Scan Range for CT shoulder
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Start above AC joint and end just below scapular tip
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Recon Slice for CT shoulder
slice thickness/ interval |
1.25 mm x 0.625mm (bone/soft tissue)
2mm x2mm MPR |
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Window Setting for CT shoulder
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350ww/50wl soft tissue
2000ww/500wl bone |
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Patient position for tibial plateau
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Patient supine, legs flat on table
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Topograms for tibial plateau
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AP and lateral
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Scan Type for tibial plateau CT
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Helical
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Scan range for CT tibial plateau
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start above patella and end just below fibular head
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Recon Slice thickness/ Interval for CT tibial plateau
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1.25mm x 0.625 (bone/soft tissue)
2mm/2mm (MPR) |
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Window setting for Tibial plateau
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350 ww/50wl soft tissue
2000ww/500wl bone |
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Patient position for CT wrist
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Patient Prone, affected arm extended over head
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Topogram for CT wrist
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AP and Lateral
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Scan Type For CT wrist
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Helical
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Scan Range for CT wrist
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Just proximal to distal radioulnar joint ending at proximal metacarpals
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REcon slice thickness/ interval for CT wrist
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0.625/0.33mm (bone/soft tissue)
2mm/2mm (MPR) |
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Window setting for CT wrist
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350ww/50wl soft tissue
2000ww/500wl bone |
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Why do CT for abdomen of Pelvis?
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• Evaluation of all organs and most vessels within the Cavity
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Indication of CT for Abdomen/ Pelvis
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• Tumors
• Carcinoma • Staging carcinoma/mets • Lymphoma/lymphadenopathy • AAA • Dissections • Unexplained weight loss • Appendicitis • Pancreatitis |
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For a CT exam for Abdomen do you use feet or head first more often, and why?
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Feet first, because head first is inconvienet due to IV line
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What to do before CT abdominal scan?
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• Confirm ID/screening form
• No metal • NCOP- no chance of pregnancy- ten day rule • Advise patient of length of time of scan • Breathing instructions – inspiration, not too deep • Tell women they may feel like they are wetting the bed |
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Patient Position of CT abdomen
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• Supine, straight and flat
• Arms raised over head, protect IV if present • Use compression band lightly to keep still • Can be head or feet first- site specific • Centering o Use laser lights o Top of scan (x) begins at highest point of diaphragm o End of scan (x) approx. lesser trochanters o Horizontal plane (Y) aligned with mid-coronal o mid sag straight (Z) |
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Topogram of CT abdomen
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• Initial scan of patient
• Lower dose • Starts at top- where laser light is • Ends when end of scan area is covered o Stop scan- image appears in real time • Can be one plane or two • Used for planning studies |
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Abdominopelvic CT Window Level/Width
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• Soft tissue windows allow some distinction between different densities of soft tissues (organs muscles fat), making edema, tumors and other abnormalities more obvious
• Liver windows are more narrow than soft tissue (short scale contrast) to improve visibility of subtle liver lesion • Lung windows are set to show the air filled lungs clearly • Bone windows make all soft tissue a nearly uniform shade, but bone is very bright and clearly seen • Windows o Soft tissue: 350ww/50wl o Liver: 150ww/30 wl o Lung: 2500ww/-600wl o Bone:1800 ww/400wl |
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CT examination of Abdomen
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• Enter patient info
• Choose body area • Choose protocol • Confirm patient data • Confirm scan parameters • Do scanogram o Topogram/localizer • Ask patient to hold breath on inspiration to reduce movement and decrease motion • Start scan • First images appear before scan is finished |
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Scan Field for CT abdomen
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start at hemidiaphragm to lesser trochanters
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Recon of CT Abdomen
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• Reconstructed images typically 5mm to 2.5mm
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Liver Multiphasic
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• Arterial phase—scan delay up to 35 sec
• Venous phase—scan delay 65 sec • Delayed—scan delay 600 sec post venous phase(suspect hemangiomas) o Hemangioma’s- disappears on delayed imaging |
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Indications of a CT chest?
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• Pulmonary embolism
• Pulmonary nodules • Infection • Mass • Trauma • Bronchiectasis • Inhalation injury • Interstitial disease • Emphysema • Coronary Artery disease |
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PAtient position for CT chest?
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• Patient lies supine on table
• Patient may require IV contrast and or oral contrast - inspiration |
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Topogram for CT chest?
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AP and Lateral?
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Scan Type for CT chest?
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Helical
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Scan RAnge for CT chest
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• Scan from above apices to below costophrenic angles—(for chest and abdomen scan 2nd group from diaphragm to below crest)
• CTA for pulmonary embolism ( can be scanned inferior to superior) from lowest hemidiaphragm to lung apices- (arterial flow of blood) |
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Windowing for CT chest?
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• Soft tissue 350 ww/50wl
• Lung 1500 ww/-700wl |
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Recons for CT Chest
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• Recons 2.5 mm thickness /1.25 intervals
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High Resolution Chests
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• May be in a series of 2-3 scans: inspiration supine (helical), expiration supine, inspiration prone
• Reformats at 1.25mm intervals |
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CTA chest Aorta
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• 2cm above arch to 2cm below celiac
• may be gated |
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Indications for CT spine
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• Disc Herniation
• Spinal stenosis • Spinal infection • Trauma • Intraspinal tumour |
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Patient Position for CT C spine
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• patient supine on table
• head first • laser lights at glabella |
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Scan Range for CT C spine?
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• scan just above skull base to mid T1
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Recon Slice thickness/ interval
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• acquired 0.625X16= 10mm or 0.625x32=20mm
• recons 2.5 mm at 1.25 intervals |
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Patient position T Spine CT
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• Patient is supine on tbale with knees bent
• Feet will enter the scanner • The patient arms are raised over their head for examinations • Laser lights at 2: above jugular notch |
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Topogram for CT T Spine?
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AP and lateral
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Scan Range for CT T Spine?
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• Scan just above T1 to just below T12
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Recons Interval/ Slice thickness CT T spine?
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• Acquired 0.625x16=10mm
• Or 0.625x32=20mm • Recons 2.5 mm at 1.25 intervals |
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Patient position for L Spine?
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• Patient is supine on the table with knees bent
• Feet will enter the scanner • The patients arms are raised over their head for examination • Laser lights xiphoid process (T9/T10) |
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Topogram for L Spine
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AP and Lateral
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Scan range for L Spine?
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• Scan above L1 to just below S1
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Recons
Slice thickness / Intervals for L spine |
• Acquired 0.625 x32=20mm or x16=10mm
• Recons at 2.5mm at 1.25 intervals |
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Windowing For SPINE CT
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• Soft tissue 350 ww/50wl
• Bone window 4000 ww/400wl |
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Myelography
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• Intrathecal contrast- Fluoroscopy
• Scan delay of 1-3 hours to allow contrast to dilute • Patient may be required to roll • Why? o Some patients can not have an MRI o Demonstrates CSF leaks |
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CTA spine
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• AV fistulas, AVM
• Blunt trauma (vascular injury) • Scan skull base to sacrum • 2 sets of scan o 1st scan delays bolus in aorta level of diaphragm o 2nd delayed scan immediately after first • 120 mL of contrast of 6ml/s o more contrast- high rate |
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Indications of CT neck
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• Bone
o Disk herniation o Stenosis of the vertebral canal and intervertebral foramen o Tumors o Abscess o Infection o Trauma • Soft tissue o Tumour congenital defects o Enlargement of glands o Infection |
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Patient position of CT neck
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• Supine
• Head first • Ask patient to lower shoulders as much as possible • Angle gantry parallel to hard palate • Center on glabella |
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Scan Range for CT neck?
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• Scan mid orbit to clavicle
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Patient instructions of CT neck?
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• Performed modified valsava maneuver “puff cheeks out” – distends pyriforms sinuses
• Pronounce longe e during scan evaluating aryepiglottic folds and pyriform sinus |
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Contrast Enhancements for CT neck
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• Contrast in the neck allows mucosa, lymph nodes, pathological tissue to enhance
• Split bolus is used o First bolus (50ml) given, scan at 2 mins • This allows for structures that slower to enhances o Second bollus (75ml), given 25 seconds after 2 minutes scans • Allows for all vessels to be fully opacified |
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DVOF for CT neck
RECON slicethickness/ interval CT neck |
- 18cm
• reconstructions slice thickness 2.5 mm at 1.25 mm intervals |
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Windowing for CT neck
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• soft tissue window 350ww/50wl
• bone 4000ww/400wl |
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CTA of neck
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• Can be used to evaluate and measure
o Stenosis of carotid arteries o Stenosis of vertebral arteries |
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CTV
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• CT venous
• Used to visualize venous anatomy • Same protocols used except images are acquired when contrast is in venous enhancement |
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CT patient position for sinuses
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• Coronal position
o Prone or supine • Perpendicular to the orbital metal line |
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CT scan range for sinuses
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• Scan from mid sella through frontal sinus
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Scan type for CT sinuses
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axial
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Does CT sinuses show air/fluid levels?
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• Provides road map for surgeons and demonstrates air fluid levels
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CT Facial Bones
Scan type Scan Range Position |
• Helical
• Below mandible to above frontal sinus • Angle to infraorbital meatal line |
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Vascular facial bones for CT
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• CTA
o Circle of willis (COW) • Scan 2 sets of images o Non contrast head o Arterial phase CTA (80ml 4.0 mL/s) • Skull base to above frontal sinus • CTV o 100ml 4.0 mL/s 30 sec delay o skull base to vertex |
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Indications for CT head
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• Stroke
• TIA • Hemorrhage • Trauma • Tumors • AVM • Thrombosis • Aneurysm • Headache/seizures • Mass/lesion/ hearling loss • Unknown surprises |
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Patient position for CT head
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• Patient lies supine on table, head placed in head holder
• If coronal position needs to be achiebed patient can extend chin and drop head as far back as possible or patient may be placed prone, (which requires a special holder) • Patient will be placed head first into the gantry • Patients orbitomeatal line or supraorbitalmeatal line should be parallel with gantry (tilt gantry) |
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DFOV for CT head
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23 cm
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Routine CT brain
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• Axial scan
o Scan below base of skull to above vertex |
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Posterior Fossa CT
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• Axial scan
o From foramen magnum to above petrous ridge |
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Temporal Bones CT
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• Axial scan
o Below mastoid to above petrous ridge (DFOV 10cm) |
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Sella
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• 99% performed in MRI
• Axial in CT o Below sella floor to aboce sella (DFOV 14cm) |
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Scan Types for HEad
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• In routine head imaging axial scanning is used
• Helical scanning is used for CTA’s |
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Window Settings for CT head
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• Window setting include:
o Soft tissue brain 160ww/40wl – slices in post fossa o Soft tissue brain 100ww/30wl – slices above post fossa o Bone 2500ww/60wl o Blood 200ww/60wl |
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Strokes and CT
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• After e a stroke edema progresses, and brain density decreases proportionately. Severe ischemia results in a 3% increase in intraparenchymal water within 1 hour. This corresponds to 7-8 hounsfield units.
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