Intro to Diagnostic Imaging Flashcards
How will objects appear on X-rays?
-Dense objects will be radio-opaque (white)
-Non-dense objects will be radio-lucent (black/transparent)
What is the order of tissue/material from darkest to whitest on an X-ray?
-Air
-Fat
-Water
-Muscle
-Bone
-Barium
-Lead
Why is diagnostic imaging important?
-To localize an anatomic problem
-To identify the tissue involved
-To identify the nature of the tissue damage
-To direct treatment
What are the different types of imaging?
-X-ray
-CT
-MRI
-Ultrasound
-Nuclear imaging
How does X-ray work?
-A form of electromagnetic radiation, ionizing
-Made by accelerated electrons hitting a tungsten target
-Quality of image depends on kVolts, mA, and exposure time
-Depends on differential absorption by different tissues
What is required for an X-ray?
A minimum of two views is required, perpendicular to one another
What is used to screen the thoracic cavity?
X-ray is a highly valuable tool to screen the thoracic cavity (ex: can see pneumonia on X-ray)
What are advantages of X-rays?
-Quick
-Inexpensive
-Ideal for bony changes
What are disadvantages of X-rays?
-Does not show soft tissue changes
-Radiation exposure (small)
What is Computerized (axial) Tomography (CT)?
-A moving x-ray
-Provides detailed planar images by progressive visual “slices”
What are the advantages of CT?
-Cross sectional images
-Can enhance contrast
-Better sensitivity than plain film x-ray
-OK with metal
-Fast
What are the disadvantages of CT?
-High radiation exposure
-Less sensitive than MRI
What is magnetic resonance imaging (MRI)?
-Applies a powerful magnetic field to the patient
-Detects the rate of magnetization and demagnetization
-Produces “slice” images, can be in any plane
What are the advantages of MRI?
-Grey scale does not apply, aka any structure can be highlighted
-No radiation exposure involved
-Can image through bone
-High sensitivity to slight tissue differences
-Can image in several planes
What are the disadvantages of MRI?
-Cost
-Time lying still
-Limited tube size
-Can’t use with metal
-Can be too sensitive/not specific
-Not good for bone/calcified tissue
What is ultrasound?
-Sends in ~ 35MHz range US signals
-Picks up (receiver) and examines timing and amplitude of the reflections for echo, examines frequency change for doppler
-Produces a 2D image in real time, can be moving
What are the advantages of ultrasound?
-Biologically harmless
-Records and displays motion
-Required no contrast
-Portable
-Distinguishes solid from fluid
What are the disadvantages of ultrasound?
-Does not penetrate bone well
-Does not go through air/gas
-Skill dependent
What does ultrasound image well?
-Fetus
-Children
-Abdominal organs (gallstones, kidneys, pelvic organs/masses)
-Aorta (aortic aneurysms)
-Blood flow (with doppler)
What is a bone scan (Skeletal scintigraphy)?
-Used to help diagnose problems with bones
-A tool of nuclear medicine
-A physiologic study-looking at problems with bone metabolism and how injured or broken bone is healing
-A small amount of radioactive drug injected into the bloodstream
What are bone scans used for?
-Metastatic disease
-Arthritis
-Stress fractures
-Osteomyelitis
-Loosening of implants
-Multiple trauma
How do bone scans work?
-Patient is given a rapidly decaying radioisotope into their veins
-Once the radiation is in the body, it can take 2-4 hours depending on what is being examined, the radioactive substance gravitates to areas of bone damage
-Once the radiation has settled a camera is used to image the bones, the dark spots on the image is the area of damage
What is nuclear imaging?
A non-invasive procedure that used injected radioactive material and a PET scanner, CT scan, or MRI
What does nuclear imaging image well?
-Thyroid masses (w/ radio labeled iodine)
-Bone metastases (18 fluoro deoxyglucose)
-Lung circulation and ventilation (xenon)
-Cancer
-GI diseas
-Endocrine diseases
