Evaluate the use of contrast media in diagnostic imaging.
evaluate - overall judgement, explain extent of effectiveness and usefulness. mention indications but also associated patient prep and health and safety.
introduction - contrast media is used in radiography to enhance the radiographic contrast of surrounding tissues. contrast medias are either more radioluent or more radiopaque than surrounding tissues. (contrast medias are positive or negative) their are associated indications and contraindications for each type plus clinical indications, however contrast media has been superseeded by other more advanced diagnostic imaging modalities, however it still has diagnostic importnce in first opinion practice in some cases, the types od contrast media, and imdications will be evalauted through this essay.
types of contrast media
contrast studies of ailmentary tract
examples of contrast media and features
contrast studies of urinary tract
myeolography (spinal studies)
conclusion - overall contrast media is a useful tool in diagnostic imaging, however the time consuming nature and asssociated health concerns mean it may be contraindicated. additionally the development of more advanced imaging tecniques such as endoscopy, ultrasound, MRI etc has meant that these tecniques are much less used and have less diagnostic value in some cases
positive - agents have a high atomic number + density, highly radiopaque, provide positive contrast and have a white apperance - barium, ionic/ non ionic water soluable iodine based media
negative - highly radiolucent, negative contrast, appear black - room air ( can cause air embolisum) so C02 and N20 safer.
double contrast media - negative and positive contrast media used in combination - studies of hollow organs e.g bladder, plus optimal mucosal detail.- used for hollow organs
barium used in ailematary tract, insoluable and inert - multiple forms available- powder, paste, suspension, BIPS.
water soluable iodine based media
ionic WSIBM - used for cardiac and urinary studies, has a very high osmotic pressure 8x normal. can cause neurotoxicity by increacing BBB permability, side effects v+, anaphlaxis
non ionic WSIBM - similar to ionic but lower osmotic pressure so safer for myelography. fewer reactions still used for cardiac and urinary studies where ionic media is contraindicated e.g hypotensive, dehydrated etc ( is more expensive)
negative contrast - air pneumosytogram ( avoid air embolisum)
ultrasound and endoscopy have supersseded its use as a diagnostic media. barium studies are time consuming have to be started early in the day so media can be followed through GI tract
barium sulphate used unless a perforation is suspected - as due to barium being inert it can cause granulaomas and adhesions to form., use IWSIBM - but is dissolved/ absorbs fluid in GI tract and dosent taste nice so harder to achive same contrast - other diagnostic imaging modalities may be indicated.
barium swallow - visualise oesophagus, indicated in cases of regurgitation, retching, dysphagia, hematemesis and suspected meagoesophagus. patient must be concious to allow swallowing and prevent aspirtaion. barium paste is placed at the back of the tounge (15 - 30 secs then must scan) for meagoesophagus - mix with tinned food to assess dilation. RL thoracic and VD radiographs taken immediately. stressful and time pressured. other modalities are more efficient at assessing oesophagus e.g endoscope, continual x-ray scans for barium swallow for megoesophagus.
barium follow through meal - visualise barium passage to the stomach and through the small intestine. indicated in cases of vomiting, diaghphram rupture, stomach displacement and FB's. centre x-rays over cranial abdo R+L lateral VD/ DV.endoscopy may be more efficient in some of these cases.
barium enema - visualise large intestine - indications tenesmus, melena, masses, intusuception. warm enema 3-4 hrs before and night before to empty GI tract. endoscope is superior to identify these conditions. GA required in these cases as its a painful procedure.
general patient prep - withold food for 12-24 hours prevent food etc obstructing veiw, oral cleansing solution, empty GI tract allow easy barium passage. GA avoided in these studies - affects GI motility plus when administering agents orally it could result in aspiration - pneumonia / regurg risk.
used to assess, kidneys, ureters, bladder and urethra. GA required to ensure correct positioning plus procedure is sometimes painflul.
indications - incontenance, heamaturia, proteinuria, dysuria,urolothiasis, caliculi.
kidneys and ureters - intravenous urography - use WSIBCM excreted by and opacifies kidneys - provide anatomical assessment.
rapid injection IVU - rapid injection of the contrast media, radiographs taken immediately then in subsequent 5 min intervals (center on umbilicus)
drip infusion IVU - IVFT with contrast media and dextrose (osmolarity - draws out excess fluid so agent stays in kidneys) administer then wait 5-10 mins before first exposure, then subsequent radiographs every 10 mins, IVFT contined to flush out media.
patient prep - GA - manage possible reactions, drip infusion contraindicated in diabetic patients, a useful tool to assess the kidneys, CT could be used but may not provide as clear contrast
bladder
cystography - assess bladder position, wall lesions, caliculi and rupture.
can use positive, negative or double contrast.- detail on mucosal surface
avoid neg (pneumosytogram)contrast if rupture is suspected could cause fatal air embolisum
ultrasonography is excellent at visulaising bladder, identifying caliculi additionally can perform cystocentesis - urine sample - more rounded diagnostics
injection of a contrast agent into the subarachnoid space to highlight the spinal cord. indicated to identify spinal lesions that cant be identified on traditional radiography. indications - paresis, paralysis, ataxia, spinal pain etc
identifys spinal cord compression, inflammetion CSF obstruction etc radiographs need to be taken immediately as CM absorbed quickly.
sites of administration - cisterna magna and lumbar puncture, need to be very specific and accurate. at cisterna magna patiensts head must be kept upright to avoid contrast media backflow to the brain.
potential complications / clinical considerations - seizures, spinal cord damage, septic meningitis, worsening neuro signs, loss of patent airway in positioning for a cisterna magna punctute.
there are many associated risks and complications with this type of contrast media study. MRI is much better modalitty to visulaise the spinal cord and possible issues associated
MRI - use gadolidium - paramagentic properties, increces speed that protons realign with magnetic feild = brighter image.
starved for 24hrs as food in the GI tract will obstruct the veiw of the kidneys.
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