YUCK YUM. The Black and White of Contrast Radiography. Contrast Radiography. Contrast Radiography Today. Definition of Contrast.

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1 The Black and White of Contrast Radiography Sarah Tibbs, BVetMed YUCK YUM Contrast Radiography Imaging techniques that utilizes either negative or positive contrast agents that enhance visualization Multitude of contrast agents (and formulations) and techniques Contrast Radiography Today Many of these techniques have been replaced by newer and less invasive imaging modalities Ultrasound especially with Doppler Computed tomography (CT) Magnetic resonance imaging (MRI) Endoscopic procedures Gastrointesinal Urogenital Laproscopy Definition of Contrast Verb: To set in opposition in order to show or emphasize differences Noun: The difference in brightness between the light and dark areas of a picture Versus the Definition of Dye Terminology A substance used to color materials examples in veterinary medicine Methylene blue (used a marker subcutanoues or intravenous) indocyanine green Die cease living, to become dead OK Contrast Contrast agent Contrast media Barium Positive contrast Negative contrast Contrast study Radiographic iodinated contrast Etc. Not OK DYE/DIE Radiologist do not EVER want things die in radiology so don t even say the word! 1

2 Types of contrast agents Contrast agents in other modalities Negative contrast attenuates less Carbon dioxide Nitrous oxide Room air Positive contrast attenuates more Barium Liquid Paste BIPS Aqueous iodinated Sterile Ionic Non ionic Non sterile Ionic MRI Gadolinium compounds Paramagnetic substance Administered intravenous Highlights abnormal areas like tumors or inflammation Because vascular barriers are incompetent Or areas that have increased vascularity Seen best on T1 weighted images where is it hyperintense (white) Relatively safe Nephrogenic systemic fibrosis reported in people with severe renal disease Fibrosis of skin, joints, eyes, and internal organs Contrast agents in other modalities Ultrasound 1. Agitated saline No special equipment Limited uses Right to Left (or reversed) shunts 2. Micro-bubbles filled with gases Special ultrasound equipment (i.e. harmonics capabilities) improve the diagnostic utility Designed to persist longer than air, to pass through pulmonary capillary bed Administered via peripheral intravenous injection Can be used to evaluate blood flow, tissue perfusion, and extravasation (bladder leakage) Negative Contrast Agents Carbon Dioxide Safest Need a source More soluble in blood than room air Critical to use this if doing a negative contrast study with potential for vascular embolization (i.e. cystography with hematuria) Nitrous oxide Not very available Safe like CO2 Handling is more complicated Room air Most available and cheapest Risk of air embolism, which can be fatal Use of negative contrast radiography When Trying to answer simple question of location Can help evaluate the wall thickness If limited access to contrast (but should consider referral) Probably will need to go further with positive or double study to gather all information Where Bladder Esophagus Stomach ( Dew-ogram ) Colon Other places not frequently done Pericardium Peritoneum Joints DO THE DEW Question 1 A 5.5 yo F(S) DSH presents for recurrent hematuria and double contrast cystography is performed What negative contrast agent would you use? a)carbon dioxide b)room air c) Carbon monoxide d)barium e) Ionic aqueous iodinated 2

3 Case example Positive Contrast Agents urinary catheter radiopaque cystic calculi Barium Aqueous iodinated agents Double contrast cystogram Filling defect in the contrast puddle because of the cystic calculi Barium Ba, atomic number 56, soft silvery metallic element Barium carbonate (witherite, BaCO 3 ) rat poison, brick making, glass making, fluorescent light bulbs Barium nitrate (Ba(NO 3 ) 2 is used to add green color to fireworks Barium in Medical Imaging Barium sulfate Highly insoluble (not absorbed), inert and completely eliminated from the GIT Not hypertonic Non irritating with soothing properties as it coats the mucosa (sometimes used therapeutically) Excellent contrast, relatively cheap Used for gastrointestinal studies (from esophagus to colon) Barium measurements Question 2 Barium can be measured by three different systems Specific gravity cumbersome and not used clinically suspension density Need special equipment for measuring water (83.2 g as 77 degrees F) and then barium mixture Or use a hygrometer Weight to Volume (w/v) Certain grams of barium added to enough water to get a predetermined total volume Example want 20% w/v in 100 ml 20 g barium to X ml water to get 100 ml total Weight to Weight (w/w) Certain grams of barium added to enough water to get a predetermined total weight Example want 20% w/w in 100 grams 20 g barium to 80 ml (grams) water to get 100 g total We use Liquid Polibar barium suspension. The concentration is 100% w/v. It is diluted 1:1 with water to make a more appropriate concentration for our purposes. How many grams of barium are in 100 ml of our mixture? a)100 b) 500 c)10 d)50 e)1000 3

4 Forms of Barium Sulfate for radiology When NOT to use barium Powders for reconstitution that tended to separate and flocculate (not recommended) Flocculation is when small particles come out of suspension and form a floc/lump Suspensions (recommended) contain inactive ingredients to minimize this Example: Liquid Polibar Emulsifier/stabilizers Flavors/preservatives, As well as anti-foaming agents Barium paste (recommended for esophagograms) Mucosal adherence Definite contraindications Do NOT use in any organ outside of the gastrointestinal tract (except on skin as a marker) If need endoscopy to follow Relative contraindications Suspect perforation Risk of aspiration Because granulomas can form But risk to benefit ratio must be considered And if surgery is to follow that debridement and lavage can be performed in body cavities to remove the barium contamination Question 3 A dog is presented for persistent vomiting. On survey radiographs you are suspicious of a intestinal foreign body. What procedure can you perform to determine if the patient needs surgery? a) Esophagram b)barium upper GI series c) Pneumocolonogram d)barium enema e)cystography Case example NEXT STEP? Intestinal obstruction with a foreign body Barium Impregnated Polyethylene Spheres BIPS BIPS Large (5mm) and small (1.5mm) spheres Usually 10 larger and 30 smaller ones are administered Either administered in one large capsule in or multiple (4) smaller capsules Either with meal (specific food) or without If in a meal, capsules are opened and BIPS are mixed with food How Interpret by how many (% of total) spheres move over time 1.5 mm empty with ingesta 5mm empty with migrating motility complexes When Chronic vomiting/diarrhea To evaluate gastric emptying or intestinal transit Looking for partial obstruction at the pylorus or in the intestines Use when there is no access to the gold standard of gastric emptying scintigraphy 4

5 Pros BIPS Does not obscure abdominal structures Easy to administer To evaluate GIT transit of solid particles (vs. barium) Cons No anatomic/morphologic information (i.e. mucosal surface information) No differentiation between extra and intra luminal obstruction Effected food or drugs NOT very reliable BIPS don t always move as expected May take up to 10 hours to complete the study Aqueous iodinated contrast agents Tri-iodinated benzoic acid ring with various side chains Monomers Ionic agents (dissociate into an anion and cation) Non-ionic agents Dimers Ionic agents Non-ionic agents Can be administered intravenously Specific agents are safe for intrathecal (IT) use Physiochemical properties of aqueous Tonicity osmotic force of insoluble particles in solution Some are hypertonic Osmolality (mosm/kg of water at 37 C) Amount of particles in solution Blood osmolality 290 mosm/kg of water Different measure but similar clinical significance Important for patient comfort, side effects, and cytotoxicity Physiochemical properties of monomers Ionic monomers For solubility the benzene ring (iodine part), dissociates from the sodium and/or meglumine Hypertonic salt compounds High osmolality ( mosm/kg of H20) Cheaper Effective NOT for intrathecal use Remember blood is 290 mosm/kg of H20 Physiochemical properties of monomers Remember blood is 290 mosm/kg of H20 Physiochemical properties of dimers Non-ionic monomers For solubility they are hydrophilic because of a hydroxyl group This is key for safe intrathecal use Low osmolality ( mosm/kg of H20) Expensive Safer/Less side effects Ionic dimers Low osmolality (577 mosm/kg of H2O) Dissociates NOT for intrathecal Non-ionic dimers Iso-osmolality (290 mosm/kg of H2O) Safest? Expensive Remember blood is 290 mosm/kg of H20 5

6 Physiochemical properties of aqueous Aqueous iodinated contrast agents Iodine Concentration varies by agent - always check label and calculate doses by mg I/kg! Maximal safe doses Dose important so as not to obscure pathology Can dilute to appropriate concentration of iodine Viscosity Effected by composition of the agent Determined in ionic agents by the cation (meglumine very viscous but Na is more toxic) Non ionic are more viscous (iohexol is very viscous) important in neurotoxicity/cellular toxicity contact time Also important in ability to administer quickly as a bolus (critical in vascular studies) Ionic Monomers (HOCM) Diatrizoate (Hypaque) Iothalamate (Conray TM ) Metrizoate Ioxithalamate Dimer (LOCM) Ioxaglate Non Ionic Monomers (LOCM) Iohexol (Omnipaque ) Iopamidol (Isovue ) Ioversol Ioxilan Iopromide Iobitridol Iomeprol Iopentol Dimer (IOCM) Iodixonal Iotrolan Question 4 A dachshund presents down in the rear. You enjoy spinal surgery and are skilled at it. You are concerned the patient needs cord decompression because of a herniated disc. A myelogram is needed to find the surgical lesion. What type of contrast would you use? a)barium b)carbon dioxide c) Sterile ionic aqueous iodinated d)non sterile ionic aqueous iodinated e)sterile non ionic aqueous iodinated Case example But the dog is down so the surgeons want to know where to cut So what procedure can we do? Lumbar myelogram With herniated L1-L2 Disc causing cord compression Mineralized discs -IVDD Contrast Media Adverse Reactions Renal failure CNS effects Others Contrast Media Induced Nephropathy Acute renal failure Peaks at 3-4 days post Resolves (usually) in 1-2 weeks Multiple incompletely understood mechanisms Renal tubule flow Direct cytotoxic effects Renal hemodynamics Increased incidence if Dehydrated (always correct before contrast) Pre-existing renal disease Others in humans 6

7 Neurotoxicity Cytotoxic effects Viscosity and length of exposure time Chemical structure, osmolality, ionicity Signs Seizures, nausea, altered mentation, vomiting, cortical blindness, cranial nerve deficits Disrupted blood brain barrier could increase risk Elevating the head after administration may decrease flow of contrast to the brain and help reduce risk ALWAYS USE NON IONIC FOR INTRATHECAL ADMINISTRATION Adverse reactions Anaphylactoid Idiosyncratic Non-dose dependent Seems like an allergic reaction Urticaria, bronchospasm, and hypotension Anaphylaxis/allergic reaction very rare antibodies are not usually formed and risk of repeat reaction is low Non -idiosyncratic dose dependent Altered myocardial function or arrhythmias, vasodilatation, and hypotension Anticoagulant Direct cytotoxic effects on brain Vaso-vagal reaction Endothelial damage, red blood cell deformation Discomfort (including N/V, chills, fever, headache, sneezing) Adverse reactions Classed as Minor, Moderate, and Severe (i.e. feel funny and get a rash to full cardiopulmonary arrest) Most reaction are mild (if severe usually in first 20 minutes) Keep crash cart near 1-3 % in humans with non ionic 5-12% with ionic Treatment of reactions Antihistamine and steroids IV fluids CPR (atropine and epinephrine) Consider pre-treatment IV fluids Acetylcysteine (renal protective effects) Steroids (but need before) or antihistamines Types of studies Lots and variable techniques GI Esophagram Gastrogram Upper GI Series Colongram Angiography Selective Non selective Angiocardiography Portography Urogenital tract IVU/EU/IVP Percutaneous pyelogram Cystogram Urethrogram Vaginogram/Vaginourethragr am Myelography Arthrography Other uncommon techniques Fistulogram Bronchography Lymphangiography Mesenteric Peripheral Pleurography/peritoneo gram Dacryocystorhinography Sialography So.. Techniques to perform studies are covered later The details of steps can vary by radiologist/text Just remember what not to do! 7

8 So..remember Barium ONLY in GI tract Case Example Non-ionic if risk of perforation Hydrate patient before IV contrast CO 2 in bladder if hematuria ONLY NON-IONIC FOR MYELOGRAM Esophagram with fluoroscopy Dilated esophagus that contains gas and some mineralized material Question 5 o How was contrast administered to this patient? Case example a)intravenously b)orally c)per rectum d)percutaneously into the peritoneum e)is this lecture over yet! Mesenteric venous portography (angiography) References 1. Costa, N. Understanding Contrast Media. Journal of Infusion Nursing. 2004; 27(5): Thrall D. Textbook of Veterinary Diagnostic Radiology. 5 th Ed Saunders, St Louis, MO. 3. Thomsen HS, Muller RC, and Mattrey RF. Trends in Contrast Media Springer, NY. 4. Wallack, ST. The Handbook of Veterinary Contrast Radiography Solana Beach, CA. 5. Walter PA, Feeney DA, and Johnson GR. Diagnosis and Treatment of Adverse Reactions to Radiopaque Contrast Agents. Current Veterinary Therapy IX. 1986: