CT and MRI Flashcards
(25 cards)
What does CT stand for in medical imaging?
Computed Tomography
True or False: Computed Tomography uses X-rays to create images.
True
list and describe the equipment in the gantry
Central opening is called the aperture
and the moving tabletop is linked to
the gantry for controlled movement.
• X-ray tube: modified from general
radiographic tube as it needs to
withstand additional heat and
increased exposure times.
• Detector array: Convert transmitted
x-ray energy into light, which is
converted into electrical energy, and
then into a digital signal.
• Collimator assembly: Pre-patient (x-ray
tube) and post-patient (in the detector
array). This shapes the and limits the
beam.
describe the computer and the operating console
Computer: Two types of software -
1 for operating system
(hardware)and 1 for the
application (pre-processing,
reconstruction and
post-processing).
Operator console: Allows the
technologist to set and control
the parameters, select the
protocol and manipulate the
images generated.
define a voxel
three dimensional tissue volumes which have height, width, depth - determined by the slice thickness.
they are isotropic (they have equal dimensions in all three planes)
define attenuation
The degree to which a tissue volumes absorbs or blocks x-rays. each voxel is represented by CT number proportional to its attenuation
define conversion
The process of translating the attenuation information of each voxel into a 2 dimensional pixel on the computer monitor
define gray scale and CT number
Numbers assigned to each pixel based on the degree of attenuation - shows different shades of gray
water - baseline = 0
more dense structures = positive values
less dense = negative values
advantages of CT scan
• QUICK, USER FRIENDLY.
• EASILY ACCESABLE.
• MORE AFFORDABLE.
• GOOD BONY DEFINITION.
• GOOD LUNG, TISSUE, ABDO
DEFINITION.
• SCAN MOVING PARTS.
• IV CONTRAST CAN BE GIVEN.
. GIVES MORE INFORMATION
THAN CONVENTIONAL X-RAYS.
Fill in the blank: Patients may be given _____ to enhance the visibility of certain structures during a CT scan.
Contrast material
disadvantages of CT scan
• LIMITATIONS FOR CERTAIN TISSUE
IMAGING e.g. LIGAMENTS,
CARTILAGE,DISC,MUSCLE,TENDO
NS MAY BE REFERRED TO MRI.
• ALLERGY IV CONTRAST.
• NOT SUITABLE FOR RENAL
PATIENTS IF CONTRAST NEEDS TO BE ADMINISTERED.
list features of a radiographic tumour
Radiographic Appearance:
Solitary mass
Irregular mass
Surrounded by oedema
May calcify
Enhancement is noted with
contrast injection
Intracranial tumor
describe the appearnce of a a subdural hematoma on a CT scan
shape - crescent shaped
blood in the dura and arachnoid matter
tear in bridging veins
more prone in the elderly and alcoholics
What is the role of a CT technologist?
To operate the CT scanner and ensure quality images
epidural hemtoma
biconvex shaped
blood between the dura and skull
tearing in the middle meningeal artery
most prone in adolescents nd young adults
subarachnoid haemorrhage
blood in the circle of willies
rapture of berry aneurysm
polycistic kidney disease
intracerebral haemorrhage
blood in parenchyma and ventricles
hypertensive vasculopathy
territory of penetrator ateries
advantages of MRi
• MUCH MORE ANATOMICAL
INFORMATION
• VERY GOOD DETAILED IMAGES.
• NO RADIATION.
• SCAN 3 PLANES
• NON-INVASIVE
• CONTRAST SAFE
• BIG FIELD OF VIEW.
disadvantages of MRI
TAKES TIME
• LIMITATIONS: METALIC OBJECTS, PACEMAKERS.
• NOT EASY FOR TRAUMA PATIENTS
• NOT GOOD FOR MOVING PARTS, CHEST
ABDO: HAS LONG SEQUENSES
• EXPENSIVE.
• SMALL CHILDREN REQUIRE GA, NO MOVEMENT.
Fill in the blank: The development of _____ has improved the speed and quality of CT imaging.
Multislice CT technology
What does the term ‘windowing’ refer to in CT imaging?
Adjusting the brightness and contrast of images
Multiple Choice: Which of the following imaging modalities is often compared to CT scans?
A) MRI
B) Ultrasound
C) X-ray
D) All of the above
D) All of the above
True or False: CT scans are only performed in hospitals.
False (they can also be performed in outpatient imaging centers)
What is the typical recovery time after a CT scan?
There is usually no recovery time needed
