Lecture 1 ppt: radiography and notes Flashcards
What is a way to test anatomical knowledge?
Seeing if you know how to interpret radiographic images
What’s the difference between radiolucent and radiodense?
1) Radiolucent tissues absorb minimal x-rays = blacker appearance on the “film”
2) Radiodense tissues absorb more x-rays = whiter appearance on the “film”
Give an example of something that’s radiolucent and something that’s radiopaque
1) Radiolucent: air
2) Radiopaque: bone
What two types of imaging have transverse sections as their anatomic view?
CT scans and MRIs
What two types of imaging don’t use radiation?
MRI and ultrasonography
Give an example of nuclear medicine
PET scan
Describe how CT scans work and what the end result is
-CT works by using x-rays too, but the machine is more advanced
-It rotates around a stationary person creating multiple cross-sectional images (Axial or transverse), which can then be rendered into a 3D image by the computer
-This gives us a cross-sectional slice (axial or transverse) of the specific body region
What property does a CT image depend on?
Density
What units is density expressed in (in regards to CT scans)
Density is expressed inHounsfield unit (HUs), whichspans from +1000 for bones (bright), 0 for water (gray), to -1000 for air (dark)
What’s one way radiologists know when there’s something wrong in a CT image?
Every tissue in the body has its normal density familiar to radiologists.
If the density is altered that could indicate something’s wrong
What is basic CT scan terminology?
Tissues can be described as hyperdense,hypodenseorisodense(when compared to some other structure)
True or false: MRIs can show physiological processes of the body
True
1) What is it called when an MRI shows physiological processes?
2) Describe how MRIs work
1) Functional MRI (fMRI)
2) MRI works by using magnetic fields and radiofrequency pulses to exciteprotons(hydrogen ions) in our body. Excited hydrogen ions emit signals toward the MRI scanner which, based on the intensity of the signal, creates a gray-scale image. As we’re made mostly of fat and water, there’s plenty of hydrogen to detect.
1) What is the density of protons in our tissues related to?
2) What type of imaging is this relevant to?
1) Increased density = increased signal
2) MRIs
1) In MRIs, how is high signal intensity shown? What about intermediate or low intensity?
2) What word do we use to describe structures that are brighter than they should be on an MRI? What about darker?
1) High signal intensity is shown as white, intermediate signal intensity as gray and low signal intensity as black.
2) When a structure is brighter than it should be, we say it’shyperintense. If it’s darker, then it’shypointense
List 3 advantages of MRIs
1) No radiation
2) Can combine with contrasts
3) Anyplane of the bodycan be imaged
List 3 disadvantages of MRIs
1) Takes longer than CT scanning
2) Uncomfortable for some people as the machine is very loud and requires the person to be placed in a narrow tube (problematic for claustrophobia)
3) MRI is contraindicated for people with metal implants due to the intense magnetic field it creates
What is the best technique for soft tissue imaging?
MRIs
1) What does a T1 weighted MRI image (T1w) show?
2) What does a T2 weighted MRI image (T2w) show?
1) T1w: best shows structures made of mainly fat (fluids are dark / black; fat is bright / white).
2) T2w: presents structures made of both water and fat (fat and fluids are bright).
1) When is PD (proton density) used in MRIs?
2) What does FLAIR stand for in relation to MRIs? What does it best show, and what is it useful for identifying?
1) Handy for examination of muscles and bones.
2) Fluid-attenuated inversion recovery; best shows the brain. Useful for identifying central nervous system disease (such as cerebrovascular insults, multiple sclerosis and meningitis)
1) In relation to MRI’s, what does DWI stand for? What does it detect?
2) What is DWI useful for and why? What conditions can it detect?
3) What does flow sensitive mean in relation to MRIs? What body part does this method show?
Diffusion weighted imaging; detects distribution of fluids (extra- and intra- cellular) within tissues.
2) DWI is useful for both structural and functional soft tissue assessment, since the balance between fluid compartments is altered in some conditions (infarctions, tumors),
3) Examines the flow of body fluids without using contrast agents; shows if everything is okay with the cerebrospinal fluid flow and blood flow through the vessels.
What 4 things are MRIs usually used for?
1) Neuroimaging (NMRI)
2) Musculoskeletal assessments
3) Gastrointestinal assessments
4)Cardiovascularassessments
Describe what each part of the brain (cortex, white matter, CSF) and bone marrow look like in both T1w and T2w MRIs
1) T1w: cortex is gray, white matter is light gray, CSF is black andbone marrowwithin bones is white.
2) T2w: cortex is light gray, white matter is dark gray, CSF is white, and bone marrow is light gray
1) Describe how ultrasounds work
2) What property does this method rely on?
3) Define echogenic
1) Uses high frequency sound waves emitted from a transducer through a person’sskin which echo from the contours of theinner body structuresbouncing back to the transducer, which then translates them into a pixelated image displayed on the connected monitor
2) The density of the tissues; defines how echogenic they are.
3) Echogenic: the amount of sound tissues will resonate back (echo) or pass through themselves
