9/12 Introduction To Medical Imaging - Brauer (Completed) Flashcards
What are the contrasts that can be used with X-ray? How are they administered? 2
Barium sulfate - orally & rectally
Iodine compounds - intravascularly, orally, rectally, vaginally
What is the role of barium sulfate as a contrast in X-rays? 2
To study hollow organs (Hernias)
What is the role of iodine compounds as a contrast in X-rays? 2
To Study vessels (angiography)
What’s happening during Fluoroscopy? Where is the source? 5
Continuous stream of x-rays using a tracer or contrast medium
Source is below the patient
How many frames per second is used for coronary artery study using fluoroscopy? 5
15 - 30 frames/second
How many frames per second is used for peripheral vascular studies? 5
2 - 3 frames/second
What is MDCT? 6
Multi-detector computed tomography
Patient moves through a rotating tube and then a computer can make 3-D renderings
What does the Hounsfield Scale measure? 7
Measures the density of a CT
What does CT stand for? 7
CT - computed tomography
What are the different values for the density of water, air, compact bone, and soft tissue in reference to the Hounsfield Scale? 7
Water –> 0
Air (of the lungs) –> (-1000)
Compact bone –> +3095
Soft tissue –> -100 - +100
What is a wide window good for in CT imaging? 7
Good for imaging bone
What is a narrow window width good for in CT imaging? 7
Good for soft tissue imaging
What are the benefits of CT? 8
Fast imaging
Some motion ok
Good resolution, gray scale can be adjusted on viewing screen
Widely available and cheap
What are the disadvantages to using CT? 8
Uses ionizing radiation
Contrast requires renal function eval
Iodine allergies w/ some patients
How does MRI work? 9
Patient is put in a magnetic field to align the spins of their atoms within all their tissue
A radio pulse is sent into the body which momentarily knocks the spins out of alignment
The atoms immediately re-align themselves and emit an energy as they do so
The energy changes for different tissue types that contain different varieties and concentrations of atoms
Imaging is received on a coil and sent to a computer
What are the contrast agents used in MRI? 9
Intravenous gadolinium
Oral Agents (juice, water)
What will appear Dark and Bright on a T1-weighted image? 10
Dark:
Tumor, inflammation,
infection,hemorrhage
Bright:
Fat, melanin, subacute hemorrhage, protein-rich fluid
What will appear dark and bright on a T2-weighted image? 10
Dark:
Calcification, fibrous tissue, protein-rich fluid
Bright:
Tumor, inflammation, infection, subdue all collection, edema (water)
What are the advantages of MRI? 11
No ionizing radiation
Better for soft tissue than CT
Very versatile (can view everything or nothing)
What are the disadvantages of MRI? 11
Data collection takes a long time
More costly than with CT
Only specific data is collected (wide range collected with CT)
Loud/hot/claustrophobic
No metal
Quiz yourself on CT vs MRI. What is the contrast that was used? 12
Open lecture
How is nuclear medicine chiefly different from CT and MRI? 13
Measures physiological process instead of anatomy
What is Digital Subtraction (DS) Angriography? 16
X-rays viewed in realtime
X-rays taken before contrast then with contrast and then bone and other tissue as are digitally subtracted out
What is a downside of DS? 16
You have to inject contrast using an IV
Why would you use volume-rendering algorithms for CT? 17
To get better depth perception within an image
During an Angiography using MRI how is a 3D perspective achieved 17
Using an MRI this can only be achieved by rotating the view
What is Functional Magnetic Resonance Imaging (fMRI) used for? 18
Detects changes in blood oxygenation and flow
Used to produce activation maps of the brain
How is it possible to use fMRI on hemoglobin? 18
Hemoglobin is:
diamagnetic when oxygenated
Paramagnetic when deoxygenated
Which methods use X-ray for image production?
Flouroscopy
CT
Nuclear medicine can be used in addition to CT
What’s the difference between AP and PA film radiograph?
PA (posterioranterior)
Film>front>back> xray tube
6ft distance
Pt. stands
AP (anteriorposterior) Film>back>front>xray tube 3 ft distance pt supine enlarged heart and mediastinum (NOT PREFERRED)
What’s the difference between flouroscopy and X-ray?
Both use X-rays, but X-ray alone is a single image w/ pt. sitting or standing. Fluoroscopy usually has the pt. lying and numerous images are taken each second
When would fluoroscopy be preferred over X-ray?
for vascular or coronary artery studies
How does CT build on plain film? How is a CT usually read? 6
CT’s builds a bunch of slices starting from the superior aspect of the pt. The computer allows for sagital or coronal views to be constructed
CTs are usually read transversely from cephalic to caudal
How does the Hounsfield Scale utilize Grey Scale? 7
Hounsfield scale uses series of greys, monitors only show 256 levels of grey therefore the “window” is adjusted to see different tissue
