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  1. 1. CONTRAST MEDIA Dr. Sabhilash Sugathan
  2. 2. Contrast media are agents which permit visualization of details of internal structure or organs that would not otherwise be demonstrable. Classification
  3. 3. Positive contrast.-the use of a contrast material that is radiopaque such as insoluble salt barium sulfate and a variety of organic iodine compounds. - Barium is used for gastrointestinal studies. - Water-soluble, iodinated contrast media are used for many procedures, including all types of angiography, intravenous and retrograde urography, hysterosalphingography, sialography , myelography , cholangiography etc Negative contrast material that is not radiopaque such as air or carbon dioxide
  4. 4. CLASSIFICATION CONTRAST MEDIA X-RAY & CT ULTRASOUND MRI BaSO4 Oily CM Water soluble IODINATED CM Hepatic excretion Renal excretion Iopanoic acid High osmolar low osmolar Ionic monomers Ionic dimers Non-ionic monomers Non ionic dimers Diatrizoate Ioxaglic acid Iopromide Iotrol Iothalamate Iohexol Iotrolon
  5. 5. BARIUM SULPHATE • Has high atomic number 56, highly radiopaque. • Non absorbable, non toxic. • Insoluble in water/lipid. • Inert to tissues. • Can be used for double contrast studies. • Uses: barium swallow, barium meal, barium meal follow through, enteroclysis, barium enema
  6. 6. WATER SOLUBLE IODINATED CONTRAST MEDIA IODINE • Atomic number 53 & atomic weight 127 • Iodine is preferred because *High contrast density due to high atomic number *Allows firm binding to highly variable benzene ring *Low toxicity
  7. 7. USEFUL FACTORS TO REMEMBER • OSMOLALITY:- Is dependent on no. Of particles of solute in solution. • RADIO OPACITY:- Is dependent on the iodine concentration of the solution & is therefore dependent on the no. Of iodine atoms in each molecule of the contrast medium. • HIGH RADIO OPACITY & LOW OSMOLALITY ARE OF DESIRABLE REQUIREMENTS. • IODINE PARTICLE Ratio-the ratio of the no. Of iodine atoms per molecule to the no. Of osmotically active particles per molecule of solute in solution is therefore a fundamental criteria.
  8. 8. CLASSIFICATION OF IODINATED CONTRAST MEDIA • There are four chemical varieties of iodinated RCM in clinical use. • All four are tri - iodo benzene ring derivatives with three atoms of iodine at 2,4,6 positions (in monomers) and six atoms of iodine per molecule of the ring anion (in dimers).
  9. 9. CLASSIFICATION OF IODINATED CONTRAST MEDIA 1. IONIC MONOMERS (CONVENTIONAL/HIGH OSMOLAR CONTRAST MEDIA [HOCM]). 2. IONIC DIMERS. 3. NON-IONIC MONOMERS . 4. NON-IONIC DIMERS. Class 2, 3 , 4 are collectively known as low osmolar contrast Medias.
  10. 10. IONIC MONOMERS (HIGH OSMOLAR CONTRAST MEDIA [HOCM]) • All ionic monomers are salts consisting of a sodium or meglumine (n- methyl glucamine) as the non-radio opaque cation and a tri- iodinated benzoate as the radio opaque anion.
  11. 11. EG:- IOTHALAMATE • Anions consisting of a benzoic acid molecule with three atoms of iodine firmly attached at C2, C4 & C6. • The c3 & c4 are connected to amines e-nh2 (r3 & r5) which reduces toxicity & increase solubility. • These anions include • Diatrizoate (urograffin, angiograffin, hypaque) • Iothalamate (conray) • Ioxithalamate, • Metrizoate • Iodamic acid
  12. 12. • Each molecule completely dissociates in water solution into two ions – one non- radio opaque cation and one tri-iodinated radio opaque anion, giving an iodine: particle ratio of 3 : 2 • Iodine content at 0.3 osmol/kg H2O - 70mg I/ml • Osmolality at 280mgi2/ml - 1500 osmol/kg H2O • LD-50 = 7(g of I/kg wt of mouse) DISADVANTAGE : high osmolality (8 times that of plasma- 300 mosm/kg water), responsible for the adverse effects, because of the non radiopaque cations( na & meg)
  13. 13. DIFFERENCES B/W MEGLUMINE & SODIUM SALTS MEGLUMINE SALTS SODIUM SALTS • SOLUBILITY BETTER SAME, LESS IN SOME ACIDS • VISCOSITY HIGH LOW • TOLERANCE BETTER LESS, NAUSEA & VOMITING • BLOOD BRAIN NO EFFECT CROSSES BBB BARRIER • VASCULAR EFFECTS LESS MARKED • DIURETIC EFFECT STRONG LESS • OPACIFICATION POOR BETTER • BRONCHOSPASM CAUSES NO SO CI IN ASTHMA
  14. 14. LOW OSMOLAR CONTRAST MEDIA • IONIC DIMERS- IOXAGLATE(HEXABRIX), IOCARMATE • Only compound, mixture of sodium and meglumine salts • Two benzene rings (each with 3 iodine atoms) are linked by a bridge to form a large compound, carries only one carboxyl group, so known as monoacid dimers
  15. 15. IONIC DIMERS- IOXAGLATE(HEXABRIX) • In solution each molecule dissociates into one radio- opaque hexa-iodinated anion and one non-radio opaque cation (sodium and/or meglumine). • Iodine particle ratio is 6:2 or 3:1 • Molecular weight is 1269 • Iodine content at -0.3 osmol/kg H2O- 150mg I/ml • Osmolality at 280mgi2/ml - 560 osmol/kg H2O • LD-50 = 12(g of I/kg wt of mouse) Eg:-Ioxaglate
  16. 16. NON-IONIC MONOMERS • Include iohexol (omnipaque), iopamidol, iopromide (ultravist), ioversol, ioxilan. • None of these molecules dissociate in solution. • They are tri-iodinated non-ionizing compounds and therefore in solution they provide three atoms of iodine to one osmotically active particle (the entire molecule), producing an iodine: particle ratio of 3:1.
  17. 17. NON IONIC MONOMERS • Iodine particle ratio is 3:1 • Molecular weight 600-800 • Iodine content at 0.3 osmol/kg H2O - 150mg I/ml • Osmolality at 280mgi2/ml - 600 osmol/kg h2o • Ld-50 = 22(g of i/kg wt of mouse) Eg:- iohexol (omnipaque)
  18. 18. NONIONIC DIMERS *Iotrolan(isovist) *Iodixanol (visipaque) • Each molecule contains 2 non ionosing tri- iodinated benzene rings linked together • They do not ionize or dissociate in solution. • Each molecule therefore provides in solution six atoms of iodine for one molecule, i.E. An iodine:particle ratio of 6:1.
  19. 19. NONIONIC DIMERS • Iodine particle ratio is 6:1 • Molecular weight 1550-1626 • Iodine content at 0.3 osmol/kg H2O- 300mg I/ml • Osmolality at 280mgi2/ml - 300 osmol/kg h2o • Ld-50 = >>26(g of i/kg wt of mouse) Eg:- iotrolan
  20. 20. PHARMACOKINETICS • After intravascular injection, the contrast media are distributed rapidly because of high capillary permeability into the extravascular, extracellular space (whole body opacification) (except in the central nervous system) & is simultaneously excreted. • Then equilibrium is reached b/w intra & extravascular space in about 10 min. Continued excretion & re entry of contrast media from ECF to ICF leads to decrease in plasma level. • Plasma half life is 30 – 60 min. • They do not enter the interior of blood cells or tissue cells and they are rapidly excreted, with over 90 % being eliminated by passive glomerular filtration by the kidneys within 12hrs.
  21. 21. ADDITIVES USED IN CONTRAST MEDIA 1) stabilizer – Ca or Na EDTA 2) buffers – stabilizes ph during storage – Na acid phosphates. 3) preservatives. 4) flavouring substances & emulsifiers for git media.
  22. 22. IDEAL CONTRAST MEDIA SHOULD HAVE:- 1) high water solubility. 2) heat & chemical stability (shelf life) - ideally 3-5 yrs. 3) biological inertness (non antigenic). 4) low viscosity. 5) low or iso osmolar to plasma. 6) selective excretion, like excretion by kidney is favourable. 7) safety: ld50 (lethal dose) should be high. 8) reasonable cost.
  23. 23. IMP POINTS TO REMEMBER • Contrast media used for myelography are non-ionic CM. • Cm used for cerebral angiography, are cm containing only meglumine cation. • Cm containing only meglumine cation- conray 280, triovideo 280, trazograff60% and angiograffin. • Cm which cause max nausea & vomiting are – ioxaglate (hexabrix). • Meglumine salts cause bronchospasm, so ci in bronchial asthma. • Among newer cm, iohexol is most hyperosmolar • Viscosity increases as conc increases & tends to be higher for big sized molecules (dimers). High viscosity interferes with mixing of contrast media with plasma & body fluids. Omnipaque240 has least viscosity. • Meticulous heparinization is required during angiography as incidence of
  24. 24. ULTRASOUND CONTRAST AGENTS
  25. 25. IDEAL ULTRASOUND CONTRAST AGENT • Be injectable by a peripheral vein • Be non toxic • Small enough to pass through pulmonary, cardiac & capillary systems • Stable enough to undergo the shear forces, hydrostatic pressure changes & diameter changes • Half life should be sufficient to allow complete examination • Should require little preparation
  26. 26. • Contrast agents might act by their presence in the vascular system, from where they r ultimately metabolized (blood pool agents) or by their selective uptake in tissue after a vascular phase. • Also called echo enhancing agents. • These agents increase the echogenicity of blood, which heightens the tissue contrast & allows better delineation of body cavities.
  27. 27. MECHANISM OF ACTION • Pri mechanism of signal enhancement is microbubble backscatter, which relates to differences in microbubble versus blood compressibility. • Increased echogenicity may be seen as an increased signal in color or spectral doppler signal strength or gray scale image intensity. • The halflife or persistence of microbubble depends on – *size(<7um passes through pul cirltn) *surface tension & gas diffusion across the bubble shell. *Transducer frequency & power • Mechanical index (MI) –peak pressure of usg beam calculated from frequency & power of usg beam. Higher the MI, more likely the bubble will break
  28. 28. GAS MICROBUBBLE CONTRAST MEDIA • Gas bubbles have a tremendous difference in acoustic impedance as compared to surrounding fluid due to the large differences in density, elasticity and compressibility. • Microscopic gas filled bubbles whose surface reflect sound waves. • Their extremely high reflectivity(backscatter) arises from the fact that microbubbles easily change their size, contracting in compression part of the ultrasonic cycle & expanding in the rarefaction part. • Thus they resonate in the ultrasound beam when there is a mismatch b/w their diameter and ultrasonic wavelength, which occurs for microbubbles in 2 to 7um at usg freq of 2-10 mhz • Free gas bubbles The bubbles may pre-exist in the liquid, or they may be created via cavitation during injection. Solution used r saline, indocyanine green or renograffin. Iv injection of physiological saline has been used as a contrast medium in echocardiography since the late sixties, but the utility of free gas bubbles is highly limited due to:- • Low stability • Large bubble size to pass the pulmonary vasculature
  29. 29. • For gas bubbles to be used as transpulmonic contrast media, the gas bubbles should be stable and smaller than 5 µm. • Bubbles larger than 10 mm may transiently obstruct the capillaries and act as gas emboli. • Several stabilizing coatings have been developed to produce encapsulated gas microbubble contrast media. • The coatings include albumin(albunex), gelatin, galactose microspheres & palmitic acid (levovist), polyglutaminic acid, lipophilic monolayer surfactants, and lipid bilayers (liposomes).
  30. 30. GENERATIONS OF ECHO ENHANCERS • FIRST GEN- UNSTABILISED BUBBLES IN INDOCYANINE GREEN , CANT SURVIVE PULMONARY PASSAGE, THEREFORE USED ONLY FOR CARDIAC & LARGE VEIN STUDY. • SECOND GEN- LONGER LASTING BUBBLES COATED WITH SHELLS OF PROTEIN, LIPIDS OR SYNTHETIC POLYMERS. • THIRD GEN- ENCAPSULATED EMULSIONS OR BUBBLES, OFFER HIGH REFLECTIVITY.
  31. 31. TYPES OF AGENTS NON ENCAPSULATED MICROBUBBLES • Formed by hand agitation • Unstable & breech quickly • Large size, small fraction pass through pul cirltn • Adequate for right heart visualization ENCAPSULATED MICROBUBBLES Encapsulated air Microbubbles *Albunex *Echovist (galactose) *Levovist (galactose & palmitic acid) *Cavisomes –gas filled cyanoacrylate microspheres for Liver, spleen & LN Encapsulated Perflurocarbon MB *Optison: albumin coated microspheres that contain Octafluropropane gas Uses:Cardiac app
  32. 32. LOW SOLUBILITY GAS BUBBLES • Since the effective duration of action of encapsulated air bubble is very short, newer agents designed both to increase backscatter enhancement further & to last longer in the blood stream, r currently under intense development. • Instead of air, many of these take advantage of low solublity gases such as perfluorocarbons, having lower diffusion rate & thereby increasing the longevity of the agent in the blood.
  33. 33. PARTICLE SUSPENSIONS OR EMULSIONS • Several types of particles have been reported as ultrasound contrast media • Collagen microspheres (solid) • Iodipamide ethyl ester (solid) • Perfluorochemicals (inert, dense liquids). • Perfluorocarbons lead to a large tissue impedance mismatch due to their high density and compressibility. • After iv injection, it can be detected in the intravascular space for several hours. Due to the small particle size, the contrast medium passes all capillary beds and will therefore enhance perfused tissue.
  34. 34. • Perfluorochemicals are eliminated either by phagocytosis of the reticuloendothelial system or by evaporation in the lungs. • Due to the selective phagocytosis, liver and spleen show late phase enhancement. • Particle suspensions are generally less effective than gas bubbles, and much larger doses are needed for enhancement. Perfluorocarbons may furthermore be less safe than the gas bubbles; a relatively high percentage of mild allergic reactions have been shown in humans.
  35. 35. DOPPLER RESCUE: • APPLICATION OF UCA RESULTS IN ENHANCEMENT OF COLOUR, POWER & SPECTRAL DOPPLER WAVEFORM & THIS IMPROVES DOPPLER IMAGING & IS TERMED AS “DOPPLER RESCUE “
  36. 36. APPLICATIONS • Evaluating normal, increased or decreased vascularity. • Detecting vascular stenosis & occlusions • Improving neoplasm detection • Analysing & characterizing tumour neovascularity • Differentiating normal variants such as renal column of bertin from neoplasm. • Echocardiography – cardiac cavities, valves, coronary artery & myocardial viability
  37. 37. APPLICATIONS HEPATIC *Neoplasm evaluation *Vessel valuation -portal hypertension -TIPSS -Buddchiari syndrome -Liver transplant evaluation RENAL *Solid masses *Pseudomases *Cysts *Renal artery stenosis *Renal transplants VASCULAR *lower extremityDoppler- native & bypass grafts *abdominal arterial examntn- stenosis Coeliac, SMA,Renal *Carotid & ranscranial doppler
  38. 38. ENHANCEMENT ON B-MODE & DOPPLER AFTER IV ECHOGEN
  39. 39. REPERFUSION STUDY OF POST TRANSPLANT KIDNEY, FOLLOWING INFUSION OF OPTISON.
  40. 40. ARTIFACTS • Colour blooming – grey scale pixels are displayed as colour pixel in areas that lack flow, occurs when high conc of UCA is delivered by bolus inj. • Bubble noise – audible sound accompanied on visible spectral doppler tracing blips • An increase (17 to 45 %) in maximum doppler shift frequency
  41. 41. CONTRAST AGENTS USED IN MRI
  42. 42. CONTRAST MEDIA USED IN MRI • GADOLINIUM CHELATES • BLOOD POOL AGENTS • LIVER CONTRAST AGENTS • ENDOLUMINAL CONTRAST AGENTS • TARGETED CONTRAST AGENTS
  43. 43. GADOLINIUM • Is the standard exogenous contrast agent used in clinical MR imaging. • It is T1 relaxing agent and is paramagnetic. • It belongs to lanthanide metal group with atomic no. 64. • It has a high spin contrast number which produces desirable relaxivity contrast agents • Three agents have been approved by FDA, they are- *Gd-HP-DO3A:gadoteridol/prohance (non ionic)
  44. 44. GADOLINIUM • These function as extracellular contrast agents. • They are rapidly excreted by glomerular filteration with half lives b/w 1 – 2hrs. • As these compounds are excreted by renal excretion, caution shd be taken in renal impaired patients. • 3 –5% of adverse reactions, occur in the form of nausea • Dose- 0.1 to 0.3mmol/kg body weight • Disadvantages *enhancement is non specific neither organ specific or pathology specific. *Short window for imaging of blood vessels as it is diluted in blood stream and excreted rapidly.
  45. 45. BLOOD POOL AGENTS • These agents reversibly bind to plasma albumin achieving a substantial improvement in magnitude and duration of blood pool enhancement. • Eg- spio-super paramagnetic iron oxide crystals -Uspio -Magnetite • These cause predominant T2 shortening. Uses – to image small vessels(eg acc renal, cor ). –vessels with slow flow (eg pul emb, dvt), -Arteriovenous malformation - Perfusion studies • Disadv: overlap b/w arterial and venous structures and separation is difficult
  46. 46. LIVER CONTRAST AGENTS • Gadobenate dimeglumine (multihance,bracco) • Small iron particles- endorem & resovist • Manganese –containing contrast agents- teslascan – absorbed by liver, pancreas and cortex of kidneys, T1 relaxation
  47. 47. ENDOLUMINAL CONTRAST AGENTS • Negative contrast agents, based on iron particles(abdoscan, nycomed-amersham) for use in MR enteroclysis & MR imaging of rectal cancer. • Combination of methyl cellulose solution for bowel distention & iv gadopentate dimeglumine for bowel wall enhancement. • Natural contrast- blueberry juice acts as a negative contrast in upper abdominal mr imaging, eg mrcp
  48. 48. TARGETED CONTRAST AGENTS • BLOOD POOL AGENTS • LIVER SPECIFIC AGENTS • NECROSIS SPECIFIC AGENTS (BIS-GADOLINIUM-MESOPORPHYRIN) • LYMPHOGRAPHIC CONTRAST AGENTS • AGENTS TARGETED AT INFLAMMATION DETECTION.
  49. 49. THANK YOU
  50. 50. • Gd CHELATES • Gadopentate dimeglumine -magnevist • Gadoterate meglumine- dotarem • Gadoteridol- prohance • Gadodiamide- omniscan • Gadobutrol- gadovist • Gadoversatamide- optimark
  51. 51. PHARMACOKINETICS • The pharmacokinetics of all extracellular MRI contrast agents with the exception of gd-bopta are similar to iodinated water-soluble contrast media. • After iv injection they are rapidly diffused into the interstitial extravascular space. • Gd chelates are eliminated unchanged from the intravascular compartment by passive glomerular filtration. • By 24 hours >95 per cent of the injected dose is excreted in urine with normal renal function. • A very small amount (<0.1 per cent) is eliminated via faeces. The biological half-life is approximately 1.5h. • Extracellular mri contrast agents do not cross the intact specialized vascular blood–brain barrier .
  52. 52. CLINICAL USE OF EXTRACELLULAR MRI CONTRAST AGENTS • These agents accumulate in tissues with abnormal vascularity (malignant, infective and inflammatory lesions) and in regions where the blood–brain barrier is disrupted. • Dosage • 0.1 millimol/kg or 0.2 ml/kg • Max dose – 20 ml • Lethal dose– 10 mmol/kg
  53. 53. SAFETY OF EXTRACELLULAR MRI CONTRAST AGENTS • Extracellular MRI contrast agents are well tolerated with a low incidence of adverse effects. • In blood, the osmotic load of all gd-based contrast media is very low, compared to iodinated contrast media, because only a small amount of the contrast agent is required to produce a diagnostic mri examination.
  54. 54. • Side effects • Minimal with standard dose. • Slight transitory increase in bilirubin & blood iron. • Mild transitory head ache (9.8%). • Nausea (4 %). • Vomiting ( 2%). • Hypotension, rash ( 1%). • Life-threatening reactions are very rare.
  55. 55. CONTRAINDICATIONS • No known contraindication. • Although , caution in • Hematological disorders- hemolytic anemia. • Pregnancy, lactation. • Respiratory disorders- asthma. • Previous allergy.
  56. 56. HEPATOCYTE SPECIFIC CM • Gadolinium based compounds: • These agents have a capacity for weak and transient protein binding and is eliminated through both the renal and hepatobiliary pathways. • The hepatic uptake represents 2–4 per cent of the injected dose. • It behaves as a conventional extracellular contrast agent in the first minutes following iv administration and as a liver-specific agent in a later delayed phase (40–120 min after administration) when it is taken up specifically by normal functioning hepatocytes. • Gadobenate dimeglumine (gd- bopta)- multihance • Gadoxetic acid ( gd-eob-dtpa)- eovist
  57. 57. • Mangafodipir trisodium – teslascan • Is strongly paramagnetic due to unpaired electrons. • Mn usually toxic , but made tolerable by complexing to a molecule which facilitates binding to plasma protein. • Primarily excreted by liver -70% (as similar chemical structure to vit b6). • Also taken by tissues with active aerobic metabolism- pancreas, renal cortex, gi mucosa, myocardium, adrenals. • So far approved by fda only for diagnosing liver lesions. • Acts by shortening t1 relaxation time.
  58. 58. RETICULO ENDOTHELIAL CELL SPECIFIC • FERUMOXIDES – • ARE SPIO ( POLYSACCHARIDE COATED SUPER PARAMAGNETIC IRON OXIDE) PARTICLES. • CONTAIN A CENTRAL CORE OF IRON OXIDE PARTICLE SURROUNDED BY A THIN INCOMPLETE DEXTRAN COATING, THAT CAUSES INDIVIDUAL PARTICLES TO FORM POLYCRYSTALLINE AGGREGATES. • THEY HAVE A SIZE OF APPROX 50- 200 NM.
  59. 59. • RES IN LIVER, SPLEEN, BONE MARROW TAKE UP THE AGENT & HAS A LOW SIGNAL IN TI OR T2*. • LESIONS NOT CONTAINING RECELLS DO NOT TAKE UP THE AGENT & REMAIN UNAFFECTED, SO HAVE A HIGH SIGNAL. • IMMEDIATELY FOLLOWING IV ADMINISTRATION, THE CONTRAST AGENT ALSO CAUSES T1 RELAXATION AND EARLY T1-WEIGHTED IMAGING MAY BE PERFORMED. • USES • DIFFERENTIATE B/W HEPATIC ORIGIN TUMOR THAT CONTAIN RES & TUMORS THAT DO NOT.
  60. 60. • DOSE • IV SLOW INFUSION OVER 30 MIN. • 0.56 MG OF IRON ( 0.05 ML FERIDEX) /KG. • SHOULD BE DILUTED IN 100 ML OF 50% DEXTRAN. • FURTHER DELAY OF 30 MIN PRIOR TO IMAGING ALLOW FOR MAXIMUM UPTAKE BY RE CELLS. • CONTRAST ENHANCEMENT OBSERVED FROM 30 MIN TO 4 HRS FOLLOWING INFUSION.
  61. 61. • SIDE EFFECTS • HAS A GOOSAFETY PROFILE. • BUT IN <3 % PTS- LOW BACK ACHE DURING INFUSION, USUALLY SELF LIMITING, DISAPPEAR AFTER STOPPING/ SLOWING, ALSO LEG, GROIN PAIN, HEAD, NECK PAIN. • RARELY -GI- NAUSEA, VOMITING, DIARRHEA, ANAPHYLAXIS, HYPOTENSION. • C/I - PTS WITH ALLERGY, HYPERSENSITIVE TO IRON, PARENTERAL DEXTRAND.
  62. 62. BLOOD POOL AGENTS • These agents reversibly bind to plasma albumin achieving a substantial improvement in magnitude and duration of blood pool enhancement. • Circulate in intravascular space for a longer time, cause significant reduction in t1 relaxation time of circulating blood. • So best for mra. • Eg- spio-super paramagnetic iron oxide crystals -Uspio -Magnetite • These cause predominant T2 shortening. • Uses - to image small vessels(eg acc renal, cor ). - vessels with slow flow (eg pul emb, dvt), - Arteriovenous malformation - Perfusion studies • Disadv: overlap b/w arterial and venous structures and separation is difficult • Gadofosveset (ms-325)
  63. 63. OTHER TISSUE SPECIFIC MR CONTRAST MEDIA • ATHEROSCLEROTIC PLAQUES (ASP) • USPIO S ACCUMULATE IN MONOCYTE -MACROPHAGES OF ASP. • GADOFLUORINES ACCUMULATE IN FOAM CELLS & CELLULAR DEBRIS DEEP TO INTIMA AT SITES OF ASP. • NECROSIS- GADOPHORINS –USED TO ASSESS MYOCARDIAL NECROSIS. • TUMOR SPECIFIC MR CM - • EG: MONOCLONAL ANTIBODY LABELED PARAMAGNETIC & SUPER PARAMAGNETIC NANOPARTICLES. • PERFLUORINATED GASES, GD BASED AEROSOLS , HYPERPOLARIZED HE & O2 GAS – IMAGING LUNGS .
  64. 64. ORAL CONTRAST MEDIA • NON SPECIFIC. • USED IN ABDOMEN & PELVIS STUDIES TO PROVIDE RELIABLE DIFFERENTIATION OF BOWEL FROM ADJACENT STRUCTURES & TO PROVIDE BETTER DELINEATION OF BOWEL WALL. • POSITIVE CM. • NEGATIVE CM.
  65. 65. POSITIVE CONTRAST MEDIA • INCREASE THE OVERALL SIGNAL INTENSITY WITHIN THE IMAGE, BY SHORTENING T1 TIMES OF TISSUE WATER. • GENERALLY SOLUTION OF PARAMAGNETIC METAL IONS. • MOSTLY PRESENT IN NATURAL PRODUCTS ( MN IN TEA). • SPECIFICALLY FORMULATED AGENTS- • MN CHLORIDE ( LUMENHANCE)- T1 RELAXING • GD DTPA (MAGNEVIST ENTERAL)- ,, BUT THE INCREASED SIGNAL MAY INDUCE GREATER ARTIFACTS DUE TO PERISTALSIS. USE OF ANTISPASMODIC AGENTS & ULTRA FAST IMAGING TECHNIQUES CAN SOLVE THIS.
  66. 66. NEGATIVE CONTRAST MEDIA • ELIMINATE TISSUE SIGNAL FROM THE AREA OF INTEREST BY:- • REDUCING THE T2 RELAXATION TIME – BY USING SUSPENSION OF FUROMOXIDE PARTICLES. • OR BY USING AN AGENT THAT CONTAINS NO PROTONS, & THEREFORE PRODUCE NO VISIBLE MR SIGNAL. • BARIUM SULPHATE, USED FOR INTRA LUMINAL STUDIES.
  67. 67. CONTRAST MEDIA RELATED TO SPECIFIC CLINICAL AREAS • RENAL TRACT THERE IS NO DOUBT THAT HIGH DOSES OF CONTRAST MEDIA IMPAIR RENAL FUNCTION, USUALLY PEAKING AT 3–5D, CAUSING A DECREASE IN URINE OUTPUT AND AN INCREASE IN SERUM CREATININE AND UREA LEVELS, DECREASED CREATININE CLEARANCE AND REDUCED GLOMERULAR FILTRATION RATE (GFR). IN SOME PATIENTS THIS MAY PROCEED TO RENAL FAILURE WITH ANURIA, URAEMIA AND DEATH. RENAL DIALYSIS (EITHER INTRAVASCULAR OR PERITONEAL) IS VERY EFFECTIVE AND MAY BE LIFE-SAVING AS AN ALTERNATIVE METHOD OF EXCRETING RCM AND URAEMIC METABOLIC PRODUCTS.
  68. 68. • THESE SEVERE ADVERSE REACTIONS ARE VERY UNLIKELY TO OCCUR IF THE PATIENT IS WELL HYDRATED AND HAS NORMAL RENAL FUNCTION BEFORE THE RCM INJECTION. PARTICULARLY IMPORTANT ADVERSE FACTORS ARE PRE-EXISTING RENAL FAILURE AND OLIGURIA, DIABETIC NEPHROPATHY, NEPHROTOXIC DRUGS, PATIENTS WHO ARE NOT WELL HYDRATED AND PATIENTS WHO ARE LIABLE TO BE INJECTED WITH VERY HIGH DOSES OF RCM FOR MULTIPLE SEQUENTIAL EXAMINATIONS REPEATED WITHIN A FEW DAYS. ALTERNATIVE IMAGING PROCEDURES MUST ALWAYS BE CONSIDERED.
  69. 69. • THE USUAL RECOMMENDED DOSE FOR IV UROGRAPHY IN THE NORMALLY WELL- HYDRATED ADULT WITH NORMAL RENAL FUNCTION IS 15–25 G IODINE; THIS DOSE MAY BE INCREASED PROVIDED THE PATIENTS ARE WELL HYDRATED (BY IV NORMAL SALINE IF NECESSARY BEFORE, DURING AND AFTER RCM INJECTION). A MAXIMUM OF ABOUT 70 G OF IODINE (1 G IODINE KG-1 BODY WEIGHT IN ADULTS) IS GENERALLY ADVISABLE EVEN IN PATIENTS WITH GOOD RENAL FUNCTION, BUT CONSIDERABLY LARGER QUANTITIES (UP TO 200 G OR EVEN 300 G OF IODINE, I.E. UP TO 600 G OF RCM) MAY BE REQUIRED, PARTICULARLY IN DIFFICULT ANGIOGRAPHIC AND INTERVENTIONAL PROCEDURES.
  70. 70. • AFTER EARLY UNCERTAINTY, IT IS NOW ESTABLISHED THAT HOCMS ARE MORE NEPHROTOXIC, AND LOCMS ARE PREFERRED FOR ALL PATIENTS CONSIDERED TO BE AT INCREASED RISK, ESPECIALLY WITH DIABETIC NEPHROPATHY. THERE IS INCREASING EVIDENCE THAT RCM (PARTICULARLY HOCM AND LARGE DOSES) MAY INDUCE DAMAGE TO THE TUBULES IN THE RENAL MEDULLA AND REDUCE INTRA-MEDULLARY BLOOD FLOW IN PATIENTS WITH ACUTE CALCULUS RENAL COLIC.
  71. 71. NERVOUS SYSTEM • LOCMS ARE MUCH MORE COMFORTABLE FOR CEREBRAL ARTERIOGRAPHY IN THE CONSCIOUS PATIENT AND ARE ALWAYS PREFERRED. CEREBRAL RCM PHOTOGRAPHIC ARTERIOGRAPHY IS BEING STRONGLY CHALLENGED AND PARTIALLY DISPLACED BY CT AND MR ANGIOGRAPHY (MRA). CEREBRAL ANGIOGRAPHY • ADVERSE REACTIONS TO RCM INCLUDE DILATATION OF THE EXTERNAL CAROTID ARTERIAL TERRITORY CAUSING FACIAL PAIN AND HEAT. DAMAGE TO THE BLOOD–BRAIN BARRIER MAY CAUSE DANGEROUS CEREBRAL OEDEMA, BRADYCARDIA AND HYPOTENSION.
  72. 72. CARDIOVASCULAR SYSTEM • PERIPHERAL ARTERIOGRAPHY THE USUAL IODINE CONCENTRATION REQUIRED FOR CONVENTIONAL FILM-SCREEN ANGIOGRAPHY IS ABOUT 300 MG I ML-1 CONTRAST MEDIUM. CONVENTIONAL HOCM (1500 MOSMOL KG-1 WATER) HAS BEEN COMPLETELY DISPLACED FOR PERIPHERAL ARTERIOGRAPHY BY LOCM (600–700 MOSMOL KG-1 WATER), BECAUSE THE LATTER CAUSES MUCH LESS WARMTH, DISCOMFORT, PAIN AND MOVEMENT. LOCM PERMITS ALMOST PAINLESS ANGIOGRAPHY IN ALL TERRITORIES, USUALLY ELIMINATING DISCOMFORT, MOVEMENT AND THE NEED FOR
  73. 73. PERIPHERAL VENOGRAPHY • VENOGRAPHY OF THE LEG FOR POSSIBLE DEEP VEIN THROMBOSIS (DVT) IS THE MOST FREQUENT VENOGRAPHIC STUDY. THE PROCEDURE IS PERFORMED BY INJECTING RCM INTO A SMALL VEIN OF THE FOOT, WITH THE LEG DEPENDENT AND TOURNIQUETS RESTRICTING PERIPHERAL VENOUS RETURN. IF THE DEEP VEINS ARE ALREADY COMPROMISED AND PARTLY THROMBOSED, PERIPHERAL VENOGRAPHY OF THE LEG IS A POTENTIALLY DANGEROUS PROCEDURE, AS BOTH DEEP AND SUPERFICIAL VENOUS RETURN FROM THE LEG ARE COMPROMISED, AND SOME CASES OF VENOUS GANGRENE DUE TO VENOUS ENDOTHELIAL DAMAGE AND THROMBOSIS HAVE BEEN INDUCED BY ATTEMPTED VENOGRAPHY.
  74. 74. • LOCM IS STRONGLY ADVISED BECAUSE OF ITS LOWER OSMOLALITY AND ITS LESS IRRITANT EFFECT ON THE VENOUS ENDOTHELIUM. ENDOTHELIAL CONTACT TIME SHOULD BE REDUCED TO THE MINIMUM BY WASHING OUT WITH SALINE, MASSAGING AND EXERCISING THE LEG IMMEDIATELY AFTER SATISFACTORY RADIOGRAPHS HAVE BEEN OBTAINED. TERMINATION OF THE INJECTION OF CONTRAST MEDIUM MUST BE SERIOUSLY CONSIDERED IF THE INJECTION CAUSES PAIN OR IF THE DEEP VEINS ARE SEEN TO BE EXTENSIVELY THROMBOSED, FOR ALL RCM MAY INDUCE THROMBOPHLEBITIS.
  75. 75. CARDIAC AND CORONARY ANGIOGRAPHY • INTRACARDIAC INJECTIONS LOCM INJECTIONS ARE MUCH PREFERRED AS THEY CAUSE LESS DISTURBANCE OF CARDIAC FUNCTION, DEPRESSION OF MYOCARDIAL CONTRACTILITY, PERIPHERAL VASODILATATION, HYPERVOLAEMIA, SYSTEMIC HYPOTENSION AND ECG CHANGES. THEY ARE ALSO MUCH BETTER TOLERATED SUBJECTIVELY THAN HOCM. • PULMONARY ANGIOGRAPHY LOCM INJECTIONS SHOULD BE USED FOR PULMONARY ANGIOGRAPHY AS THEY CAUSE LESS ELEVATION OF THE PULMONARY ARTERY PRESSURE, COUGHING, MOVEMENT AND DISCOMFORT. SEPARATE UNILATERAL PULMONARY ARTERY INJECTIONS SHOULD REPLACE MAIN STEM PULMONARY ARTERY INJECTION.
  76. 76. • AORTOGRAPHY INJECTIONS OF LOCM AT THE 300–400 MG ML-1 IODINE CONCENTRATION ARE GREATLY PREFERRED AS THEY CAUSE MUCH LESS DISCOMFORT AND VASODILATATION. • CORONARY ANGIOGRAPHY HOCMS (E.G. UROGRAFIN 76 PER CENT) WITH PHYSIOLOGICAL LEVELS OF SODIUM AND WHICH DO NOT BIND AVIDLY TO SERUM CALCIUM (RELATED TO BUFFER AGENTS) HAD A GOOD REPUTATION FOR SELECTIVE CORONARY ANGIOGRAPHY, BUT LOCMS ARE EVEN SAFER FOR THEY CAUSE LESS MARKED HAEMODYNAMIC, MYOCARDIAL AND PHYSIOLOGICAL CHANGES AND DEPRESSION

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