Intro To Radiology Flashcards
Define an imaging modality
Variety of techniques utilized to acquire images of body (i.e. radiographs, MRI)
Describe radiographs, their modality, and whether they utilize ionizing radiation. What can be identified with a radiograph and what is the correct way to describe it?
2D images yielded from X-ray - show shadows of different radiographic density.
Ionization radiation - yes! X-ray are electromagnetic and have short wavelengths and high energy - interact with the body
Radiographic densities that can be identified: air, fat, water, bone, and metal (from least to greatest - air is black, bone/metal is white)
Lingo - radiopaque/ radiodense = looks bright, radiolucent = looks dark
What is ionizing radiation?
Radiation of x-rays (or gamma) or nuclear particles which have enough energy to free an electron from an atom or molecule - causing it to become charged
What are the advantages and disadvantages of radiographs?
Advantage: quick and cheap, available nearly anywhere, demonstrate bone/metal very well
Disadvantage: ionization radiation (chest X-ray about 1/5), limited info for soft tissues (can’t characterize anatomy well unless they are different densities, 3D anatomy can become superimposed or magnification occurs by being too close to the radiograph, also blurring can occur from patient moving
Define fluoroscopy and the modality used. State the advantages and disadvantages of using fluoroscopy. Provide an example of a fluoroscopy study.
Fluoroscopy is continuous x-ray passed through patient - can create a movie or still image. Often utilizes contrast agent; equipment can be portable
Ionization radiation - yes (scale of 3/5or 4/5)
Advantages: can see inside of bowel, bladder, heart chambers, thecal sac etc
- Real time visualization
- Moderate expense (~$300-900)
Disadvantages
- allergic/uncomfortable reaction to contrast used
- significance radiation exposure
Examples: barium swallow study, esophagram, myelogram
Describe interventional procedures, what modalities can be used, as well as any advantages and disadvantages. Provide an example of an interventional procedure.
Interventional procedures are best thought of as a treatment - you can diagnose and treat at the same time utilizing CT scan, MRI, Ultrasound and/or fluoroscopy
Advantages: Compared to open surgeries, they are minimally invasive, less expensive and less pain
Disadvantages: Possible complications (contrast allergies, pain, hemorrhage, infection)
- Blood product/body fluid exposure to personnel
- Radiation exposure 2/5
Examples: lung biopsy, placing drain, cardiac catherization and stenting
Describe nuclear medicine, what modality used, as well as how to describe generated images. What are the advantages and disadvantages of NM?
Nuclear medicine utilizes radiopharmaceutical (radioactive substance) by introducing into the body and studying a specific organ. As the substance enters and exits, radioactive decay causes GAMMA rays - imaged utilizing gamma camera.
Lingo: AKA Scintigraphy. Anatomy that shows on an image = hot, increased uptake, photon rich.
Anatomy that shows poorly or not at all = cold, decreased uptake, photon poor, photogenic
Examples: PET scan, nuclear stress test
Advantage: Excellent at showing organ function!
Disadvantage: Does not show organ anatomy in great detail -looks grainy
- Expensive! $2000-7000. IR is relatively high (bone scan 3/5, PET 4/5)
Describe how CT works, it’s advantages and disadvantages, as well as how to characterize images.
CT = computerized tomography - high tech use of x-ray, X-ray tube/ detector spiral around patient. Computer analyzes x-rays striking detectors and converts image.
Lingo: Some rays are attenuated when passing through body (Absorbed/lost), so when something looks bright = high attenuation; dark = low attenuation
Advantages: Excellent cross sectional anatomy, tremendous radiographic density resolution (1500x better than conventional X-ray), rapid, widely used. Excellent guidance for interventional procedures
Disadvantages: Expensive ($600-2000)
- Cumbersome for patients that may have tubes/catheters/ IV poles etc
IR = 3/5
metal causes artifact on CT, and when contrast is used can have complications
Describe how ultrasound is used, how resulting images are describes, as well as the advantages and disadvantages.
Ultrasound = sonography
Lingo: Bright image = hyper-echoic or echogenic, if less so= hypoechoic, if none = anechoic
Advantages: Relatively inexpensive, ZERO IR, real time imaging, can directly image any plane, IV contrast seldom used, safe for pregnant women and babies.
Disadvantages: Hard to image deep structures, so difficult to image obese patients or immobile patients
- US does not travel well through bone or air so certain anatomy not seen well
- Anatomy difficult to identify without proper training
Describe how MRI works and how to describe resulting images
MRI mainly images hydrogen within the body - most abundant in water and in fat.
- Proton on each hydrogen is spinning - creates electrical current ->
causes magnetic field - this aligns with strong magnet of MRI -> freq. can be calculated and a radio wave with matching freq. can be transmitted to them
*Matched frequency causes absorption of the ray by the hydrogen atom (resonance)
- when ray is turned off, hydrogen releases energy, is detected and converted to images.
Different tissues give that energy off at different rates = tissues can be told from each other
Images: Anatomy that is bright = high signal intensity; anatomy that is dark = low signal intensity
What are the advantages and disadvantages of MRI?
Advantages: excellent cross sectional anatomy, especially soft tissues (and bone)
- zero ionizing radiation
- can direly image any plane, can do non-invasive vascular imaging without contrast (unless necessary - Gadolinium - fewer complications than iodine based)
- good guidance for interventional procedures, tricky because of how metal reacts in magnetic field
Disadvantages:
- Expensive (400-3000)
- Contraindicted for some - patients with pacemakers, internal defibrillators, cerebral aneurysm clips, claustrophobia
- Artifact can be unavoidable because a patient can’t hold still or metal present
- Exams are slow
- Not widely available, and obese patients are generally not a good candidate.
What is the purpose of PACS and HIS?
PACS: Picture archiving and communication system: system of software that transmits images from multiple modalities onto serves to sore the images or allow them to be accessed simultaneously from multiple sites within a hospital
- often connected to RIS or HIS
HIS: hospital information system: Integrated system of hardware to manage all aspects of a hospitals operation, like medical, administrative, financial , legal issues
- can access PACS through this by caregivers
- pretty much - consolidates patient care information
