CT Flashcards
What are disadvantages of conventional radiography?
no depth detail
organs/structures superimposed
What is cross sectional imaging?
Slices of human body in transverse/axial plane
CAT scans stand for?
Computed axial tomography
What are 3 planes of body?
Axial
Coronal
Sagittal
What is CT?
Using computer technology with x-ray to image body cross-sectionally
What type of image receptor is used in CT?
defector
What is the width of the slice determined by?
Width of x-ray beam
What is the image represented by?
MATRIX of numbers
What does each pixel have?
number that represents the x-ray attenuation in corresponding voxel of object
Each pixel has a location
What is a high CT number equal?
white areas because of increased attenuation
What does a low CT number equal?
Black because of decreased attenuation
What is the Hounsfield scale?
water is 0
air is -1,000
bone is 1,000
What does a narrow window allow?
Enhancing contrast of tissue
eg soft tissue window, bone window
How does CT work (3 steps)?
x-ray tube linked to detector
tube and detector circle patient
takes hundres of x-ray pictures
What are 4 advantages of CT?
Visualization of internal organs
avoids superimposition of tissues
high contrast allows differentiation of organs
viewed in multiple planes
what was the intial scanner?
Shoot and step (1 slice)
table only moves when source is off
What are spiral scanners?
Constant table movement
What is multislice scanners?
Multiple detector rings
What is the current rotation spped?
4 per second
What are 3 resolutions?
Spatial
Contrast
Tempora
What are 3 pieces of equipment in CT?
Gantry (doughnut on side)
computer
table
What is the procedure?
Patient lies in supine table & arms placed over head (body scans)
table moves in and out of gantry
holds breath at various times
IV contrast injected
oral contrast administered
What is the topogram?
Plain 2D image as initial scout view
used to define start & end of main scan
Find any artefacts
What is windowing?
changing brightness & contrast image
focuses on different anatomical structures
What does MRS allow for?
Selection of optimal plane to image an organ/disease process
What are 2 limits in CT scans?
aperture size
patient limits
what is the axial plane?
looking from patients feet up
left side of image is patients right side
what does orla constrats media do?
delineate small bowel
What are 2 types of oral contrast?
gastrogafin & barium
What does IV contrast allow for?
demonstrate blood vessels
improves sensitivity of lesions
small possibility of reactions
What are 6 medial applications in CT?
Oncology - staging & diagnosis
stroke
trauma - bone damage
guiding biopsy procedures
screening for disease
bone mineral densitometry
What are the top 4 cancer types?
lung
colorectal
breast
prostrate
What are 4 disadvantage of brain imaging?
unable to visualize vasculature without contrast media
poor visualization of cerebellum
poor sensitivity acute stroke
no anatomical detail
What does CT images show in the brain?
Exact, number, location and affect of tumor on adjacent structures
What type of strokes do CT distinguish?
Hemorrhagic or ischemic
What does CT perfusion imaging measure?
cerebral blood flow for early stroke detection
What 4 things can CT tell us about hemorrhage?
identification, location, classification and age of hemorrhage
How can CT demonstrate fractures?
due to high spatial resolution imaging
What 4 things can CT tell us about sinuses?
Which sinuses are affected
presence of polyps
anatomical variants
anatomy of OMU prior to FESS Sx
What can CT scans visualise in the inner ear?
ossicles and semicircular canaks
bone erosions
What 4 diseases do CT investigates?
hearing loss
tinnitus
pain
swelling
What is high resolution CT good for?
Chronic interstitial lung processes eg emphysema and fibrosis
airspace diseases
What 3 things can CT detect?
pulmonary angiography
pE detection
abdominal aortic aneurysm detection
What is used to image the hear?
Modern multislice CT scanners
How is CT used in oncology?
Disease detection
staging
monitoring
What does CT scans show about tumour follow up?
patients response to treatment
disease progress
What can CT scans be used for abodomn?
acute abdomen
solid organ injury
oncology
appendicitis/renal stones
What sex is pelvis CT limited to?
Females
What can pelvis scans show?
Oncology scanning & staging
fracture detection
What is a CT colongraphy?
Scan if large bowel
air pumped into colon
What are 3 examples of CT intervention?
Biopsies
Drainage
Tumour ablations
What is the CT dose?
2-20mSv
1 in 2000 risk of additional cancer incidence
What does increasing dose allow for?
Better image quality
what is the effective dose in chest CT?
~8 mSv
What is a ceretom scanner?
8 slices brain CT in trauma units
What are 3 improvements?
Dual source CT
perfusion imaging
radiomics
How many slice scanners do wide row detectors have?
320
What resolution is increased in dual source?
temporal resolution of 83ms due to covering large area in short amount of time
What is seen at 80kV?
iodine bone metal
What is seen at 140kV?
Plastic
uric acid stone
fat
What is an application of dual energy CT?
Quantification of iodine to visualize perfusion defects in lung
air, tissue, iodine
defects in myocardium
What does CT and PET combine?
Anatomical and functional imaging
images fused together
When is micro CT used?
studies which minute detail is desired
nm
When are examples of micro CT?
Tissue engineering
enamel thickness & tooth measurement
What is nano-CT?
Pixels of 300nm
What is industrial CT used for?
QS of materials
What aid is used for diagnosis with CT?
computer
How do you achieve no noise?
CNN machinery
What is radio genomics?
Create imaging biomarkers
