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Ultrasound

WHat is propagation?
-passage of sound through a medium

-influenced by frequency of sound and density of material
What is acoustic impedence?

What is attenuation?
-measure of a material ability to propagate sound

-asorbtion of energy by a material
WHat is echogenicity (reflection)?

How do sound waves propagate?
-a materials ability to create an echo
-how well sound "bounces"

-by compression and relaxation of molecules (elasticity)
WHat can happen to the sound waves during a boundary effect, or tissue with different densities?
-scatterred (very high difference in frequency)
-reflected (echo)
-refracted (bent)
-atenuated (absorbed)
How is echo strength determined?

What are the color differences on an ultrasound
-by tissue elsaticity and density
-very large differences cause scattering and a weak echo

-weaker signal: darker image
-stronger signal: whiter image
What determines image depth?

How does gas present itself in an ultrasound?
-how long it takes to "hear" the echo

-low density, poor transmission, anechoic, black
How do fluid-filled structures present themselves on ultrasounds?

Solid organs?
-defined by walls, ie cysts, blood vessels

-uniform transmission through tissue
-speckled appearance due to lack of homogeneity
How does fat present itself in an ultrasound image?

What is the result of using low frequency waves for deep structures?
-hyper-echoic relative to solid organ, outlines structures

-high penetration BUT low resolution
What is the result of using high frequency waves for superficial structures?

What is the doppler effect?
-low penetration bU high resolution

-a sound-wave phase shift
-allows color imagin of vascular and cardia blood low
What are some ultrasound artifacts?
-acoustic shadowing: caused by metal, bone, gas, calculi blocking the sound wave

-comet tail: tapering bright echoes, caused by air bubbles, cholesterol crystals
WHat are some disadvantages of an untrasound?
-operator-dependent

-obesity (increased attenuation)

-bowel gas: limits role in GI evaluation and deep structures

-bone density: limited role inmusculoskeletal evaluation
How will gas, fat, water, and bone present itself on an Xray?

WHat are some factors that will affect image quality?
-air: black
-fat: blck/gray
-water: grey
-bone: white

-tissue density
-motion
-magnification
-rotation
-distortion/angulation
How far is the "bucky" suppose to be from the xray source?

On a lateral (routine film), which side of the pt will be against the "buky"?
-72 inchs.

-lateral with left side against
WHat does a lateral decubitus flim aid in identifying?

WHat are some contrast agents used for xrays?
-free fluid/air

-metallic subs.: braium or gadolinium
What is a major caution with using contrasts?

WHat are some contrast agent side effects?
-anaphylactic shock

-lactic acidosis in conjunction with a glucophage
-nephrogenic systemic fibrosis (gadolinium)
-renal failure (iodinated agent injected IV with (rapid) renal clearance
What is contraindicated in pts with compromised renal functionor myeloma?

WHat is need to localize an object?
-iodinated agents

-two views
WHat must always be an assumption when a child comes in with a fracture of a major bone?

What is the range for CT slices?
-child abuse

-1mm to 10mm
WHat is important when requesting a CT?

How does a CT image read?
-important to specify objective in consult

-slices are taken from foot to head
How is radioactive material introduced into the body?

WHere does the radioactive material aggregate?
-tagged to a substrate

-in a hypermetabolic area
WHat is imaging based on in nuclear med?

WHat is the purpose of nuclear med in diagnostic studies?
-metabolic uptake with the use of a "gamma" camera

-physiological function
What is a scintography used for?

What is used as a chemical contrast in a positron emission tomography (PET)?
-bone scans

- F-18 fluorodeoxyglucose
What is a co-registration?

What does the molecular imaging of scintigraphy indicate?
-PET in conjunction with MRI or CT

-indicator of metabolic activity in which "hot spots" will be seen in places where uptake is high
What type of exposure is used in scintigraphy?

WHat are some benefits for using a PET scan?
-low energy gamma radiation with a short half-life

-it is superior to CT for mediastinal evaluation for staging
-decrease in the need to biopsy (less invasive)
-metastatic disease in normal-sized lymph nodes and extrathoracic sites
WHat is the medium used in SPECT MUGA?

What is the benefit to using nuclear medicine studies?
-Tc99m labeled RBC's for cardiac function and EF

-low risk: dose of radiation is not harmful to the pt
How does an MRI work?
-radiofrequency field is rapidly cycled (pulsed) thus allowing for a magnetic field to be created which in turn alters the proton spin and creates an image from the electrical field.
WHat are some contraindications in an MRI study?

Beyond the vast capabilities of an MRI, what is one increasing role for an MRI that inhibits unnecessary radiation exposure?
-retained metal objects
-pacemaker
-claustrophobia

-mammography
What type of tissue is an MRI going to be useful for as apposed to a CT?

Which has a longer study time?
-MRI focuses on soft tissue, whereas a CT is for more dense tissues

-MRI is longer (45 min compared to 5 min)
What type of energy causes radiation injury?

Out of the radiation particles, what is the order for increasing level of LET radiation?
-linear energy transfer (LET), a related type and intensity of radiation, and duration and exposure

-alpha: high LET, short range, stopped by paper
-beta: lower LET, long range, stopped by skin
-gamma: low LET, longer range, deep tissue penetration

-
WHat are some of the biological effects of ionizing radiation?
-intra-cellualr free radical formation (peroxides), which may react with and damage DNA

-cellular repair mechanisms are overwhelmed increasing the probability of permanent damage or death

-geneticallt damaged cells may produce abnormal cells that may become concerous
What will a radiography study help indicate in a cavitation/abscess?

What is looked for with masses/nodules?
-wall thickness and air-fluid levels

-margins smooth or irregular
What are some causes of inflammatory responses?

What will be some of the causes of fluid inside the lungs?
-pathogens, allergens, foreign bodies, trauma, cardivascular disease

-fluid collection from leaky capillaries (exudate) or changes in osmotic pressure (transudate) - also blood
What can an inflammatory response lead to?
-abscess formatio: thick walled cavity w/ fluid inclusion

-granuloma formation: solid mass

-fibrotic changes: thickened tissue with reduced compliance (elasticity)
What will inhibit an inflammatory response?

What is a trans-esophageal echocardiography especially used for?
-immune suppression

-heart valves and EF
What is the standard of care for imaging in a level I ED?

Where should the lungs be at full volume?

-CT

-the diaphragm should be at the 10th rib
What is a lordotic shot used for?

What are the blind spots on a lateral study?
-the lung apices

-retro-sternal space
-retro-cardiac space
-hemi-diaphragms
What is an expiratory film ordered for?

WHat is indicative in the image study in an expiratory film?
-obstruction

-diaphragm should be at about the 7th rib with a widening cardiac silhouette
What can an over-exposed image be useful for?

How far out should the pulmonary vasculature be seen peripherally?
-in emphasizing dense structures and retro-cardiac areas

-about 1/3 out from the hilum
What will be seen in a study of a female that has had a mestectomy?

What may the nipple shadows be mistaken for?
-leads to a loss of density, increased lucency
-loss of bilateral symmetry
-check for masses (why a mestectomy?)

-nodules
WHich type of pt postitioning will affect the cardiac silhouette shape by making it larger?

WHich hila is higher, left or right?
-AP will make the silhouette larger

-left should be higher
What is cephalization?

What is unusuall about seeing lymph nodes in a CXR?
-the redirection of fluid in the cephalid direction in a pt that is upright (supine position will always shift the fluid and therefore does not constitute cephalization)

-they should not be seen in the hila or the mediatinal area at all
What is located in the anterior compartment of the mediastinum?

Middle?

Posterior?
-ascending aorta, aortic knob, heart, lymph nodes, thyroid, and thymus

-esophagus, trachea, lymph nodes, and aortic arch

-descending aorta, lymph nodes, spinal nerves, and vertebral bodies
What should the heart shape and size be in a normal CXR?

What is a sulcus sign indicative of?
-on a PA film te width of the heart should be less than 1/2 the width of the thoracic cavity with distinct borders and normal contours

-it is presumptive evidence for the presence of a pneumothorax on a supine radiograph
What are lateral CXR valuable for?

-localizing a lesion seen on a frontal CXR

-clarifying lobar collapse/consolidation

-evaluating a retrosternal or retrocardiac shadow

-confirming the presence of encysted fluid (loculated) in the oblique fissure
What does the major and minor fissure seperate?

What part of the PMH of the pt is of interest when examining a current raadiograph study?
-major: seperates the right lower lobe from the middle and upper lobes of the right lung
-minor: seperates the right upper lobe from the middle lobe of the right lung

-old films that are available in medical records so that any possibly missed lesions are not expanding and may just be benign
-also to track congestive heart failure
Which area of the lungs do foreign objects typically reside?

WHat is the first component of the airway that is absent cartilage rings, and has smooth muscle with adrenergic innnervation?
-the right mainstem bronchi

-bronchioles
What can obstruction in the airway lead to?

What are some acute causes of inflammation?
-atelectasis

-asthma, infection, chemical irritation
What are some chronic causes of inflammation?

What are some pulmonary structural changes?
-bronchitis and emphysema

-blebs and bullae
What is a genetic airway pathology?

What is atelectasis?
-cystic fibrosis

-incomplete expansion (collapse) of a segment of a segment or lobe that developes over time.
-rapid resolution once obstruct. is cleared
With atelectasis, will there be mediastinal deviation?

What are some indications for further evaluation with bronchoscopy or CT scan in a pt with atelectasis?
-yes, towards the afflicted side

-entire lung atelectasis
-atelectasis of a lobe for more than 2 days
-atelectasis of a segment for more than 2 weeks
Is a CXR necessary for an acute exacerbation of asthma?

What about long standing asthma?
-no, but it is indicated for suspicion of infectious process or aspiration of foreign body

-may show an interstitial pattern caused by scarring or mild bronchiectasis
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