Introduction to Imaging Flashcards
Name the three imaging planes.
sagittal plane
coronal plane
transverse (axial) plane
sagittal plane
longitudinal section that divides the body into right and left sections
midsagittal (median) plane - in midline
parasagittal - unequal right and left portions
coronal plane
divides body into anterior and posterior portions
perpendicular to sagittal plane
transverse (axial) plane
divides the body into superior and inferior portions
Name six imaging modalities
x-ray radiographs
ultrasound
computerized tomography (CT)
magnetic resonance imaging (MRI)
nuclear medicine
positron emission tomography (PET)
x-rays
electromagnetic waves produced by bombardment of a tungsten target with an electron beam
shorter wave length than visible light
radiographic images depend on differences in absorption of xray radiation by different tissues
effective radiation dose
calculated value, masured in mSv, that takes into account:
- absorved dose to all organs in the body
- relative harm level of the radiation
- sensitivities of each organ to radiation
What is the average background radiation exposure in the US?
3 mSv per year
ALARA principle
as low as reasonably achievable - try to decrease the dose for all the tests that are done
five basic x-ray densities
air (most black)
fat
soft tissue or water (shades of gray)
calcium or bone
metal or contrast (most white)
mammography
technique utilized to maximize soft tissue differentiation
screening for breast cancer
diagnostic work-up of patients with breast problems
GI contrast studies
x-ray studies using barium or dilute water soluble iodine solution to evaluate GI tract
contrast administered orally to evaluate esophagus, stomach, and small bowel
contrast introduced via a rectal tuve for study of large colon
air contrast exams for mucosal detail
fluoroscopic monitoring
angiography
injection of a contrast agent into a blood vessel followed by xray imaging of the blood vessel or area of the body fed by that vessel
used to evaluate coronary arteries as well as peripheral vasculature
also used to evaluate abdominal vasculature
can be used in tumor evaluation and to guide treatment
myelography
introduction of contrast material into the spinal subarachnoid space
used to evaluate disc disease as well as diseases in and around the spinal cord
arthrography
injection of contrast and or air into a joint space
can be used to evaluate the shoulder joint as well as the write joint, knee, or ankle
computer tomography
computer algorithm generates cross sectional images based on x-ray beam array passed through the body
all body parts can be imaged
image descriptor is density
intravenous (iodine based) and oral (barium or iodine based) contrast may be used to enhance anatomic and tissue differentiation
ultrasound
image based on computerized processing of sound
image descriptor is echogenicity
sound beam cannot pass through air
fluid is black
can be used in multiple areas of the body
good soft tissue differentiation
no known side effects
modality of choice for imaging pregnant woman
magnetic resonance imaging
computer generated image obtained by placing patient in a magnetic field and applying a radiofrequency pulse to change alignment of hydrogen protons
may use intravenous contrast (gadolinium)
image descriptor is signal
tissue caracterized with different pulse sequences
multiple scan planes possible
nuclear medicine
image generated by radioactive agent tagged to a tissue specific molecule
Tc99m frequently the radioactive agent
physiologic imaging rather than anatomic detail
examples - bone scan, hepatobiliary scan, tagged RBC study, cardiovascular studies
image descriptor is activity
positron emission tomography
radioactive isotope of a normally occurring element inserted into a molecule used by the body, such as glucose
physiological imaging
evaluate areas of increased uptake
imaging descriptor is activity
