Exam 1 Introduction to radiology Flashcards
Explain X-rays
Radiation passes through patient strikes cassette to create an image, rays don’t pass through dense tissues as easily creating the outlines
What is Computed Radiography?
x-ray passes through patient strikes a sensitized plate which is read and digitized into a computer image
What is digital radiography?
x-ray strikes a plate of sensors producing the computer image directly
Which type of radiography sends the image directly to the computer: digital or computed?
digital
Why are x-rays harmful to biological organisms?
can displace electrons from energy level, creating a free radical
What are the different risks of radiation?
deterministic effects resulting in cell death: skin erythema, epilation, radiation burns or cataracts; stochastic effects: cancer/leukemia
T/F: pediatric patients are at increased risk for stochastic effects
True; higher proportion of rapidly dividing cells
What are examples of background radiation exposure?
radon, radioactivity from rocks, cosmic rays
What accounts for 95% of all radiation exposure?
medical imaging
What does the risk model look like that estimates lifetime risk of radiation induced cancer?
linear no-threshold dose response curve (dose and risk are directly proportional
What questions should you ask to reduce the risk of radiation-induced cancer?
Is this test necessary? Will it change the management of the pt? Is there a better study that would answer the question?
What are the technical factors that can be controlled to reduce the exposure to radiation?
decrease tube current/tube voltage, wider collimation or change speed table moves, automated methods
What trimester is absolutely critical to avoid radiation exposure?
First trimester (organ exposure); after 2 gestational weeks it gets better
What is the first line of study to look at lungs, heart and skeleton?
Plain films
What are the main uses for plain films/x rays
CXR, spine films, skeletal films, abdoment films
What should always be done when getting an x-ray
get more than 1 view to put it in more of a 3D
What is basis of ultrasound?
high frequency sound waves reflect back based on distance/density
Does ultrasound use ionizing radiation?
negatory
What is the primary way of evaluation pregnancy?
ultrasound
What are the best uses of ultrasound?
pregnancy, gallbladder, abdominal/pelvic pain in women and children
T/F: ultrasound is good for evaluating veins for DVT?
False
Do CT scans use IR?
yes; a lot
How does CT work?
gantry moves around patient taking x-rays at many angles and computer puts them all together
What is CT best used for?
acute hemorrhage of brain, mass effect or herniation of brain, chest imaging, PE, tumor, interstitial lung disease, abdominal screening (tumor, inflammation, obstruction), UTI and kidney stones
T/F: CT can be used for non-hemorrhagic infarction?
false, it’s not good at that
T/F: CT is good for gallbladder disease? Abdominal pain in young women?
False; False
Can you use contrast for CT scans?
yes
What are the risks of IV contrast for CT scans?
Allergic reactions, contrast-induced nephropathy
What are risk factors for IV contrast reactions?
preexisting renal fxn ,DM, nephrotoxic drugs, reduced intravascular volume
How can you prevent nephropathy due to contrast?
Hydration, Mucomist
Does MRI have IR?
nope
Explain idea behind MRI
magnetic lines up all dipoles and measures their relaxation at different rates
What can MRIs damage?
pacemakers, aneurysm coils, other implants
What are the primary uses of MRI?
Patients with inflammatory bowel disease, liver for cancer, very specific images of nearly everything in the body
What is the contrast of MRI?
gadolinium
T/F: MRI contrast (gadolinium) is nephrotoxic?
False
What can gadolinium (MRI contrast) cause?
nephrogenic systemic fibrosis (NSF)
What is nuclear medicine good at?
gallbladder and bone scans
T/F: nuclear medicine is more of a functional test than giving a detailed anatomic representation?
True
What are barium exams less common than endoscopy?
barium gives you just the information, endoscopy allows you to do something while in the area.
What has CT replaced barium exams for diagnoses?
diverticulitis and small bowel obstruction
What do PET scans use for “contrast”?
FDG (flourine 18 fluorodeoxyglucose)
what is PET scans good for?
demonstrate abnormal metabolic activity in organs
What have PET scans been coupled with? Why?
CT scans to make them more accurate in localizing regions of abnormal uptake
