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Radiology > Radiology year 4 lecture 7 > Flashcards

Radiology year 4 lecture 7 Flashcards

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1
Q

What extra information can be gained from using contrast agents?

A

shape, position, size, contour, number, internal architecture, function, mucosal surface, integrity of sturcture

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2
Q

Must contrast agents be more radiolucent, the same or more radiopaque than the surrounding soft tissues?

A

radiolucent/ radiopaque

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3
Q

What are agents called that are more radiolucent than surrounding tissues?

A

negative contrast

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4
Q

What are agents called that are more radiopaque than surrounding tissues?

A

positive contrast

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5
Q

What are the ideal properties of a contrast medium?

A

Different absorptive power from soft tissue, non-irritant/ toxic, accurate delineation of organ, persistnece for a sufficient time to take a radiograph, totally expelled from the body, inert

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6
Q

What are the properties of negative contrast agents?

A

lower atomic number or density than soft tissue so appearing black on the film

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7
Q

what negative contrast agents are there?

A

air (most common), oxygen, NO, Co2

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8
Q

Where are negative contrast agents used?

A

bladder, GI, peritoneal. Either alone or in combination with positive contrast in double contrast studies.

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9
Q

What are the advantages of negative contrast agents?

A

cheap, quick, safe

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10
Q

What are the disadvantages of negative contrast agents?

A

poor mucosal detail if usd alone, air and oxygen are slowly eliminated and may confuse further studies, theoretical risk of air embolus.

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11
Q

What are the properties of positive contrast agents?

A

higher atomic number than soft tissue so appear white on film.

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12
Q

What two elements are normally used as positive contrast agents?

A

Barium sulphate, iodine (as a complex organic molecule).

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13
Q

Where are barium sulphate preparations used?

A

GI tract, bladder and nasal chambers

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14
Q

Why should barium sulphate not be injected into blood vessels?

A

it is insoluble so in liquid forms a suspension, not a solution

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15
Q

what different forms can barium sulphate be used in?

A

powder. paste, suspension, barium-impregnated plyethylene spheres, mixed with meat for looking at oesophageal disorders

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16
Q

What are the advantages of barium sulphate?

A

low toxicity, excellentmucosal detail, inert, may actually soothe GI tract, palatable,

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17
Q

What are the disadvantages of barium sulphate?

A

inhalation may cause pneumonia, leakage from perforated GI tract will remain indefinitely in th emediastinum/ peritoneum causing granuloma/ adhesion formation.

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18
Q

Water are ionic water soluble iodine-containing constrast media derived from and how are they produced?

A

derived from benzene ring of benzoic acid, with three iodine atoms added and variable side-chains. They are all clear solutions are produced as sodium or meglumine salts. (sodium= toxic but low viscosity, meglumine= low toxic, higher viscosity. Usually they are combined.)

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19
Q

What ar the advantages of ionic WSICM?

A

water soluble so can be injected into vessels, rapid excretion by kidneys, allowing urinary studies, available in different concentrations for different studies.

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20
Q

What are the disadvantages of ionic WSICM?

A

very high osmotic pressure (hyper osmolar) compared with the body (x5) due to dissociation in body fluids. LEads to vomiting, nausea, shivring, flushing, metallic taste in the mouth, decreased BP and periperal vasodilation, anaphylaxis. morality in man 1:40000

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21
Q

what has been produced to try and reduce the side effects of ionic WSICM?

A

dimer ioxaglate (hexabrix).

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22
Q

What are the two categories of ionic WSICM?

A

intravascular and oral

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23
Q

What are intravascular ionic WSICM used for?

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A

heart, great vessels, kidneys, liver, carotid, cerebral circulation. Intillation: bladder, joint, slaivry glands, sinuses.

24
Q

What are the disadvantages of intravascular ionic WSICM?

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A

irritant if injected perivascularly (use a cannula), ittitant in inflamed bladder, may cause discomfort in large doses, toxic and CV effects, cardiac and renal failure?

25
What are oral ionic WSICM used for?
GI studies if GI perforation or inhalation.
26
what at are the adantages and disadvantages of oral ionic WSICM?
advantages: absorbed if leak into lung or body cavity Disadvantages: bitter taste, expensive, hyperosmolar so draw fluid in to GI tract and become progressively diluted and less radiopaque, irritant to mucosa, fast transit time, poor mucosal detail sirculatory collapse.
27
What form do non-ionic WSICM come in?
monomers or dimers
28
What are the properties of non-ionic WSICM monomers?
do not dissociate in solution, low osmotic pressure (so side-effets reduced)
29
What are the non-ionic WSICM monomers used for and what are the advantages and disadvantages?
subarachnoid space for myelography, intravascular. Lower side-effects, good contrast, safe for myelography, expensive (less so now).
30
Name a monomer non-ionic WSICM
iopamidol
31
What are the properties of dimer non-ionic WSICM?
latest generation (not lisensed for animal use yet). They are iso-osmolar with plasma and thus further reduced the unwanted side-effects of conventional ionic and non-ionic media. Better image quality as not diluted.
32
What are cholecystopaques used for?
billiary system and gall bladder. IV not suitable for small animals. iodine compounds are specially prepared with increased protein binding to be taken up by the liver.
33
When is oily iodine contrast media used?
when WSICM too irritant or for longer study duration. Investigating uterus, salivary glands, lymph vessels.
34
Should anaesthesia be used in GI tract studies and why?
not unless for colon. It is difficult to administer barium for an oesophageal study if patient asleep and it can interfere with peristalsis and increased the risk of barium entering lungs if regurgitated. Opiates also slow gastric emptying and increase intestinal transit times.
35
What would require investigation of the oesophagus?
retching, regurgitation, dysphagia.
36
What is the technique for looking at the oesophagus?
No preparation required, plain films first, administer slowly. Barium sulphate paste- persists and adheres to mucosa- highlights lesions liquid: highlights radiolucent foreign bodies, position of oesophagus (use if megaoesophagus suspected) liquid and meat: highlights dialtions but will not allow investigation further down GI tract Use Gastrografin if suspect oesophageal perforation
37
what views are most useful for the oesophagus?
lateral of neck and thorax, dorsoventral view of thoracic oesophagus may give additional information.
38
What allows imagins of swallowing function directly?
image intensified fluroscopy
39
When would the stomach need to be investigated?
persistent vomiting, haematemesis, radiolucent foreign bodies, neoplasia, delayed gastric emptying, position, shape, size.
40
What is the technique for looking at the stomach?
starve for 24hrs, give enema if faeces in colon, sedation (acepromazine, buprenorphine), plain film first.
41
What is given for a positive contrast gastrogram, how is it viewed?
liquid barium by stomach tube (2-3ml/kg), right and left lateral, ventrodorsal, dorsoventral centred on cranial abdomen. Gas bubble and barium puddle highlight different areas of the stomach.
42
Why is a double contrast gastrogram good and what does it involve?
Better detail than positive alone. Give liquid barium by stomach tube, roll animal to coat gastric mucosa, give 10-15ml/kg air by stomach tube,remove stomach tube, hold mouth closed.
43
For the double contrast gastrogram, how many views are taken and where is the air/ barium in each position?
four views. RLR: air in fundus, barium in pylorus, LLR: air in pylorus, barium in fundus VD: air in body, barium in fundus and pylorus DV: air in fundus and pylorus, barium in body. Repear films in 5-10 mins and re-repeat at intervals if required.
44
When should gastric emptying begin, when should the stomach be nearly empty and completely empty?
15mins (in nervous animals 30-45mins), nearly empty 1-2 hours, completely by 4hours.
45
What does a double contrast gastrogram show?
position of stomaach, thickness of wall and integrity, oreign bodies/ masses,adherence of barium to mucosa (erosions or ulcerations), accumulation of secretions (if barium appears dilute)
46
When is a negative contrast gastrogram used?
rarely. USeful for stomach position, foreign body, cheap and easy with little risk of barium inhalation but poor mucosal detail.
47
What are the indications for investigation of the small intestine?
same as for stomach
48
What is the technique for small intestine investigation?
starve for 24hours, enema if required, sedation, plain film first, 3-5ml/kg barium sulphate liquid by stomach tube, lateral and ventrodorsal projections initially 15mins after administration, then at regular intervals (30-60mins), centre mid abdomen.
49
When should barium reach the large intestine and all be in the large intestine?
4 hours, by 24 hours.
50
What can be assessed through barium in the small intestine?
position of intestines, thickness of wall, integrity of wall, obsturction, lesion on mucosa, dilution of barium
51
How can the large intestine be investigated?
Not follow-through with barium as it goes into faecal balls. | Instead: barium enema, double contrast study, pneumocolon.
52
When would a barium enema be used to investigate the colon?
tenesmus, melaena, identificaiton of colon relative to other masses, (chronic diarrhoea).
53
what is the technique for barium enema?
low residue diet for a few days before, non-irritant soapy water enema 2-3 hours before examination, general anaesthesia- Foley catheter or purse string to overcome reduced anal tone, plain films first, dilured barium sulphate suspension, lateral and ventrodorsal abdomina projections.
54
Why would you use a double contrast study in a colon exam?
for enanced mucosal detail.
55
What is the technique for a double contrast study of the colon?
as for barium enema, allow barium to drain our, distend colon with air 12-20ml/kg
56
Why would you use a pneumocolon?
cheap, easy, good for position of the colon. less mucosal detail
57
how much air should be given for a pneumocolon, what views should be used and what can be seen?
10-20ml/kg, lateral and ventrodorsal projections. | position of colone, outline, filling defects (objects), mucosal damge.

Radiology (7 decks)

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