Introduction to Radiology and Imaging Anatomy Flashcards
X-ray mechanism
X-ray photons interact with tissue and are either attenuated or pass through tissue
X-rays have the ability to____
penetrate tissue
Types of attentuation
Absorption
Scatter
What changes the appearance of radiograph
Direction and orientation of the object imaged
Radiography machine made of
Detector and X-ray source
No penetration of x-ray
Radiopaque (white)
Complete penetration of x-ray
Radiolucent (black)
Degree of x-ray penetration depends on
Atomic Number
Thickness
Higher atomic number means
More radiopaque, whiter, more absorption
Thicker means
More radiopaque, whiter, more absorption
What can x-ray not distinguish between
Water and soft tissue
Radiography as a function of composition (radiopaque to radiolucent)
Metal, bone, soft tissue/water, fat, gas
X-ray contrast agents and how they change
Iodine or barium
Attenuate the x-ray beam
Appear very radiopaque
Barium (x-ray)
Only for enteric use
Iodine (x-ray)
For enteric or vascular use
Enteric contrast agents administered either
Oral or rectally
Intravascular contrast agents (x-ray)
Iodine only
Venous or arterial
Lipohemarthrosis
Joint effusion containing fat and blood/fluid
Fat gloats to the top because it is less dense
Radiographic views of x-ray
Frontal (anteroposterior or posteroanterior)
Lateral
Orientation of X-ray
As if you are looking straight at the patients face
Way that lateral chest x-ray named
Side that is against the detector
Ex. left lateral
Do you need more than one view with x-ray?
Yes
Orthogonal views
Views at 90 degrees of each other
What kind of image does CT give?
Axial slice through body
Advantages of CT over radiography
CT eliminates superimposition of structures outside area of interest
CT has high-contrast so can better differentiate things like water and soft tissue
Data can be viewed in axial, coronal, or sagittal planes (multiplanar)
CT uses _________
ionizing radiation
Disadvantage of CT scan
Higher radiation dose
2 components of CT
Gantry and table
Mechanism of CT
X ray tube and detector rotate around the patient
Orientation of CT images
As if you are looking at the patients feet on the bed
CT units used
Attenuation
Attenuation
Degree to which something blocks a photon
Attenuation can be expressed how many ways?
2 - qual and quant
Low attenuation to high attenuation of CT
Gas, fat, water, muscle, active blood, contrast, bone
CT image composed of
voxels
CT windows _____
refer to adjustment of gray scale to highlight areas of interest
CT enteric contrast
Iodine or barium based solutions
H2O soluble CT contrast agent
Iodine
H2O insoluble CT contrast agent
Barium
Intravenous contrast media
Iodine based
Will make all organs with large blood supply much brighter (aorta, kidneys, liver)
Names for relative attenuation
Hypoattenuating
Isoattenuating
Hyperattenuating
CT enhancement
Increase in attenuation of a tissue after contrast administration
CT and metal
Can’t handle metal and will create lines across the image
Ultrasound mechanism
Based on acoustic sound waves
No ionizing radiation
Pulses emitted by transducer and reflected back by body tissues
Why use gel?
Air and gas are highly reflective so if present, sound wave will not make it to the body
Brightness of US depends on
Amplitude of signal
Depth of US image depends on
Timing at which echo originated
What will sound not travel through?
Gas and bone
Can only see cortex of bone because of this
Orientations of US images
Longitudinal (sagittal)/transverse (axial)
If target moving towad transducer…
FR>FT
If target moving away from transducer…
FT
Color doppler
Frequency info can be used to determine direction of flow in blood vessels
Uses frequency shift
Fluid in ultrasound
Doesn’t show up
Ultrasound terminology
Anechoic/Echolucent
Hypoechoic
Hyperechoic/echogenic
MRI mechanism
Uses magnetic fields and radiofrequency waves to create images
Imaging protons
No ionizing radiation
Disadvantages of MRI
Takes a lot longer
MRI components
Magnet and table
MRI T2 weighted
Fluid is bright Highlights pathology (edema)
MRI T1 weighted
Fluid dark
Highlights anatomy
Fluid in MRI
Stationary relative to how fast the scan takes place can be imaged
In MRI, fat is typically
Bright
MRI fat saturation
Fat signal is nulled
Vascular contrast MRI
Vessels and organs will be high in signal intensity on T1 ONLY weighted images
Advantages of fat saturation
Can help to highlight edema
MRI terminology
Hypointense (low SI) Isointense Hyperintense (High SI)
MRI contrast agents
Gadolinium based
Makes tissues bright on T1 weighted sequences
DIfferences between MRI and CT
Bones much brighter in CT