Imaging Lecture Test 4
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- What are four special concerns w/ equine radiography?
- proper restraint, possible injury to personnel, damage to machine, need more time & patience
- Name two positioning devices for equine radiography
- positioning block and cassette tunnel
- What is the most common type of xray machine for equine?
- portable
- What is the most common cassette size for equine xray?
- 10x12
- What are three machine options for equine xray?
- small portable, mobile unit, mounted unit on rails
- Four safety considerations for equine xray?
- protect personnel 1st (equip 2nd), take safest view possible, avoid views from behind rear leg, never hold xray tube
- Why is labeling esp important for equine xray?
- all legs look the same from cannon bone distally
- 3 technique consideration for equine xray?
- clean debris from area of interest, pick foot & pack w/ playdough, and views of joints should be done weight bearing
- Why are special contrast techniques needed?
- give more info than flat films, used to highlight a lesion, increases contrast w/i a specific organ
- What are two types of contrast media?
- pos and neg
- What type of contrast media makes area white?
- Positive
- What type of contrast media makes area black?
- Negative
- Give 2 examples of positive contrast medias
- Organic Iodine & Barium
- What contrast media is used for excretory urography, angiography, and cystography?
- Organic Iodine
- What contrast media is usually used for the GI tract? When would it not be used and what would be used in its place?
- Usually barium, but contraindicated if perforation suspected - then iodine would be used
- Examples of neg contrast medias
- room air, oxygen, CO2, nitrous oxide
- What 2 neg contrast medias are safer because they are easily absorbed and have lest chance of air emboli?
- CO2 and nitrous oxide
- What type of contrast media is used for pneumocystography, double contrast studies, and pneumography?
- Negative
- What contrast media has side effect or air embolism?
- Air
- What are some side effects of iodine?
- nausea, allergic reaction, anaphylactic reaction, hypotension, and shock
- What are some side effects of barium?
- aspiration (make sure tube is in stomach), peritonitis (from perforation - leaks into abdomen)
- What change of exposure technique is used w/ contrast media?
- Increase MAS by 30%
- Describe general patient prep for abdominal study & what views taken?
- fast for 12-24 hours if possible, enema 4 hours prior, VD and right lateral views taken
- When is excretory urography indicated?
- to check kidney function and size
- What is procedure for excretory urography?
- place indwelling IV catheter, give bolus injection of iodine contrast agent, take films
- What are the 3 phases of excretory urography?
- nephogram (see renal vasculature), pyelogram (see renal pelvis), drainage phase (see ureters)
- When is cystography indicated?
- to examine bladder wall for abnormalities or tears
- What are 2 precautions for cystography?
- don't over fill bladder - it can rupture, use nitrous rather than air because of air embolism
- What is the procedure for cystogram?
- sedation necessary, do survey films first, clean penis, pass urinary catheter, remove urine, infuse contrast agent until bladder is moderately full
- Name and describe 3 kinds of cystograms
- pos contrast (iodine), pneumocystogram (gas), double contrast (both)
- When is a urethrogram indicated?
- to examine internal structure of urethra
- Name the 2 types of urethrograms
- retrograde and antegrade
- describe a retrograde urethrogram
- + or - contrast inserted w/ a balloon-tipped catheter, film taken at end of injection
- Describe retrograde urethrogram
- + contrast is placed into bladder (must use enough to induce urination), film is taken at voiding
- When is esophagography indicated?
- to examine esophageal function
- Describe esophagography procedure
- barium or iodine used, pt. in lateral recumbency slowly infuse contrast agent into cheek or mix into food, take film at pt swallows
- When is an upper GI study indicated?
- to evaluate stomach and small intestine
- In what situations are barium and iodine not used in an upper GI?
- don't use iodine in a dehydrated pt, don't use barium if perforation is suspected
- Describe patient prep for an upper GI?
- 21-24 hr fast, enema 4 hours prior, sedation if needed
- Describe procedure for upper GI
- do survey film first, use barium or iodine, place stomach tube, induce agent into stomach
- What views are taken in an upper GI series?
- VD, DV, & rt lateral
- Describe a double contrast gastrogram
- same as upper GI except pt needs empty stomach and gas introduced right after barium - films done right away (don't wait)
- When is a barium enema contraindicated?
- when rupture/perforation is suspected
- Describe procedure for a barium enema
- survey films first, pt in lateral recumbency, lubricated enema cath inserted and balloon inflated, infuse media slowly
- What is a pneumoperitonealgram
- the injection of CO2 or nitrous into the peritoneal cavity to improve the contrast of abdominal organs
- What is a myelogram?
- induction of iodine contrast into the subarachnid space around the spinal cord
- What is a non-selective angiogram?
- injection of a bolous of iodine contrast into a vessel - film is taken at time of injection and is effective for identifying occulsions or aneurisms
- How does US work?
- Short bursts of ultra-high frequency sound waves are xmitted into patient. When they hit something they bounce back and are converted into a white dot on monitor screen.
- In US, the greater the difference in density and composition between two adjoining tissues, the ____ the echo will be.
- stronger
- In US, the stronger the echo, the ____ the white dot on the monitor screen.
- brighter
- In US, what determines the position of the white dot on the monitor screen?
- the length of time between the production of the sound burst and the return of the echo
- In US, echos from deeper tissues take ____ to return to the transducer and will be be placed as white dots ____ on the monitor screen.
- longer, lower
- In US, echos from more superficial structures tissues return ____to the transducer and will be be placed as white dots ____ on the monitor screen.
- faster, closer to the top
- What is the appearance of fluid on an US?
- Black
- What is the appearance of soft tissue on an US?
- shades of grey
- What is the appearance of bone/stone/gas on an US?
- white
- What is acoustic impendance?
- How well a substance xmits sound
- What is acoustic interface?
- the boundary between two tissues w/ different xmitting properties (causes returning echo)
- What is echogenicity?
- the ability to produce echos
- What is anechoic?
- produces no echos (no dots on screen)
- What is hypoechoic?
- Produces weak echoes (grey dots on screen)
- What is isoechoic?
- produces echoes similar to background echoes
- What is hyperechoic?
- produces intense echoes (bright white dots on screen - bones)
- What is resolution?
- The degree of image detail and quality
- One cycle per second is called a ____.
- hertz
- One million cycles/second is called a ____.
- megahertz
- Diagnostic US uses sound waves at what frequency?
- 2-10 MHz (2-10 million cycles/second)
- What is attenuation?
- sound waves are attenuated or decreased as the travel through tissue
- What three thing can cause attenuation?
- absorption, reflection, and scatter
- What are three common transducer frequencies?
- 3.5, 5, and 7.5 MHz
- The higher the transducer frequency, the ____ the sound wave is attenuated, but the ____ the detail.
- faster, better
- lower transducer frequency = ____ penetration and thus ____ poorer resolution
- better penetration, poorer resolution
- higher transducer frequency = ____ penetration and thus ____ poorer resolution
- lower penetration, better resolution
- US does not penetrate what three things?
- bones, stones, and air
- In US, you must have gel between transducer and skin in order to eliminate what?
- air gap
- What is an acoustic window?
- clear path for sound wave around bones or lungs to get to structure of interest
- What is acoustic shadowing useful in identifying?
- bladder stones
- What is acoustic enhancement and what is it used for?
- Concept that sound waves travel through fluid more readily thus they have higher remaining energy when they pass through an area composed of fluid. Useful in differentiating a solid tumor from an abscess.
- What is the most common display format in US?
- Real Time - produces a moving picture - can see fetal movement and heart beating
- In US, what type of display format isn't used much anymore.
- A Mode
- In US, what display format isn't used very often, produces a still life picture, and is also called "brightness mode"?
- B Mode
- In US, what display format is used w/ echocardiography, produces an "ice pick" view of the heart, and makes a line tracing of heart wall and valve action?
- M Mode