diagnostic imaging lecture 4

Question 0

what can you inject into a space to create high contrast? eg?

Answer 0

inject iodine. eg. subarachnoid space. definition of spinal cord improved.

Question 1

what causes contrast? what is high contrast? what is low contrast? what if film contrast?

Answer 1

different opacities. the difference in radiographic gray tones between two radiographed structures due to their physical differences. high contrast = black and white
low contrast = garay and gray.
film contrast - the ability of an xray film to produce a degree of image contrast.

Question 2

obesity is a problem why?

Answer 2

all looks gray due to subcutaneous fat over the tissues. eg. cant see spinal cord or tissues.

Question 3

how does kvp affect contrast? scatter?

Answer 3

high kvp decrease image contrast. under/over exposure decreases image contrast. (comton effect) = high scatter. kvp = penetrating power.

Question 4

how does fat effect contrast? if too fat?

Answer 4

fat enables soft tissue contrast by preventing silhouetting. but, high quantities of fat decreases image contrast due to the high kvp needed for penetration.

Question 5

intraabdominal fat is good why?

Answer 5

nice outline of the organs is seen as it reduces silhouetting. provides a natural contrast.

Question 6

how does gas effect contrast?

Answer 6

gas surrounding abdominal organs enhances the contrast. can inject it to provide a negative contrast medium. good inside the intestines.

Question 7

what is pneumoperitoneum?

Answer 7

gas inside the abdomen (not inside organs) can occur after surgery and it outlines the organs.

Question 8

what may you use contrast mediums for? what must you do first?

Answer 8

must take a plain xray first. they are added to enhance contrast and outline a structure. give i/v, orally, rectal, urethral, cardial chambers.

Question 9

what are negative contrast media’s? eg? show up? radiolucent? adverse effects?

Answer 9

do not absorb x rys eg. gas. radiolucent (dark) air, co2.

outline hollow organs. very simple and cheap. may cause overdistention and rupture, gas embolism.

Question 10

what is a positive contrast media? eg’s? shows up? radioopaque?

Answer 10

high absorbtion of xrays. - very radioopaque. (light) barium sulphate, or iodine compounds. - spinal cord, gi tract.
outline internal surface of hollow organs
organ displacement
filling defects.

Question 11

barium sulphate is used as a? must make sure gi tract is intact why? only safe to use where? application?

Answer 11

positive contrast media. application by oral or rectal. outline wall and lumen of gi tract. coats mucosa.
biologically inert, not metabolized or absorbed.
only safe in gi tract!!! if it gets into the peritoneal cavity then can cause neoplasia and granuloma. GI tract must be intact!!!!

Question 12

what are BIPS? used for? application?

Answer 12

barium impregnated polyethylene spheres. used to outline motility. given orally and take x rays at intervals. eg. delayed gastric emptying.

Question 13

when does barium sulphate become a problem?

Answer 13

when it leaks into the peritoneum or when it is inspired. - aorway obsturction and hypoxia. no problem inside the GI tract.

Question 14

iodinated contrast media? what kind? shows up? which type would you use in the spinal cord?

Answer 14

positive contrast media. shows up radiopaque (light) used to outline renal function/bladder/vagina. or in spinal cord - use non-ionic to avoid dehydration. but slightly more expensive! - does not dissociate.
ionic dissociates into cations and anions - hyperosmolar.

Question 15

which is the specific contrast media used for renal function? and biliary excretion?

Answer 15

iodinated contrast media.

Question 16

what are the adverse affects of iodinated contrast media? how are they reduced?

Answer 16

iodine allergy rare in small animals. , acute renal failure, pulmonary oedema, vomiting, hypotension, allergic reaction, seizures. much reduced with non-ionic media.

Question 17

what if you give too much contrast media?

Answer 17

sturcutures may be overshadowed. but if an opaque sturcture is surrounded by contrast media that is more radiopaque that itself - may appear lucent. radiopaque = light!!!!

Question 18

explain a double contrast study?

Answer 18

use both positive and negative contrasts. it highlights mucosla detail with positive contrast. but provides a dark back ground with the negative contrast. avoids overshadowing.

Question 19

when may you use iodinated contrast media for CT?

Answer 19

applied IV.

shows up vasculature of masses etc. eg. surgery of a mass to see how vascular it is. vascular filling defects in heart.

Question 20

what contrast medium may you use for MRI? not iodine

Answer 20

rare earth metals - gadolinium. eg. disruption of BBB.

Question 21

contrast media in ultrasound? problem? what does the sound reflect off? used for?

Answer 21

iv injection. sound reflection by gas bubbles. simple and cheap. but bubble may burst in capillaries. an expensive way is to use encapsulated microbubbles. may be used for portosystemic shunts.

Question 22

is the skull hard to radiograph? what angle shound you use?

Answer 22

yes! use later oblique angle (tilt the head.)

Question 23

what are common diseases of the skull?

Answer 23

inflamm, congenital, metabolic, neoplastic.

Question 24

peridontal disease?

Answer 24

common. involves soft tissues and bone! gingival retraction. alveolar bone and tooth root lysis.

Question 25

what are some congenital disease of the skull?

Answer 25

occipital dysplasia. hydrocephalus. (open fontanelle and flat skull.)

Question 26

metabolic bone disease? caused by?

Answer 26

hyperparathyroidism. increases pth. increases calcium reabsorbtion from the bone. hypercalcaemia.

Question 27

neoplasms of the skull? mainly in the nasal cavity

Answer 27

carcinomas, sarcomas - may be in the turbinates.

Question 28

what are the roentegan signs of a nasal neoplasia?

Answer 28

increased opacity
tubinate destruction
local bone lysis
nasal septal deviation

Question 29

infectious nasal cavity? eg? can be destructive? or non-destructive

Answer 29

rhinitis.
destructive - aspergillus, hard to differentiste from neoplasia
non- bacterial. inflamm, foreign body NO MASS EFFECT.

Question 30

what is otitis? roentgen signs?

Answer 30

infection of the ear canal. common. evaluate with radiographs. thickened sclerotic bullae and ear canal mineralisation.

Question 31

spinal cord - myelography. - contrast medium injected into the subarachnoid space which outlines the spinal cord.

Answer 31

good! can see collapsed disks and bone lysis.

Question 32

difference between extramedullary myelography and intramedullary?

Answer 32

extra - common hen the disk pushes in on the cord.

intra - golf tee sign - uncommon. oedema, haemorrhage, neoplasia. distended cord.