Contrast Media in Medical Imaging PDF 2024

# Contrast Media in Medical Imaging ## Dr. Muhd Rifqi Bin Rahim - Clinical Radiologist ## Outline - Introduction - Iodine Nated Contrast Media - Barium Suspension - MRI Contrast Media - Radionuclide Contrast ## Contrast Media (CM) * Chemical substances * Cause increased atomic number of area, high attenuation or differential absorption of X-rays from the surrounding tissues. * Permit clear demonstration of an organ or tubular structure. * To improve visibility of specific organs * Help distinguish “contrast” selected areas from surrounding tissues ## Contrast * **Subject Contrast**: Range of differences in the intensity of the X-ray beam being attenuated by the subject. * **Low Contrast Structures**: The difference of medical information between muscle, organs or vessels. * **Contrast Media** is used to enhance subject contrast in a tissue that normally has low subject contrast. ## Contrast Media Changes The Density of the Organs Therefore changing the subject contrast will change the radiographic contrast and film contrast. ## Contrast Media (Review) | Negative Contrast | Positive Contrast | |---|---| | (Air or CO2) | (all others) | | X-rays easily penetrate | Absorb X-rays | | Low atomic # material | High atomic # material | | Radiolucent _cannot_ be seen | Radiopaque _can_ be seen | | Black on film | White on film | ## 2 Basic Types of Positive CM ### Barium - Suspension - GI Tract Ingested or Rectally ### Iodine - Water Soluble - Powder - Liquid - Oil Based ## Iodinated CM Why lodine? - High atomic number #53 ### Water Based - Injected - intravascular / arterial / ductal/thecal - For oral ingestion - Organ function/flow - Open wounds - Ionic - High osmolality CM - Non-ionic - Low osmolality CM ### Oil Based - Not for intravascular Injection - Not for ingestion - Only ducts - Open wounds ## Differences Ionic and Non-Ionic CM | Ionic Contrast | Non-Ionic Contrast | |---|---| | The benzene ring is associated with the anion (-) and Cation (+) □Diatrizoate sodium (Hypaque) □lothalamate meglumine (Conray) | Gadodiamide (Omniscan) □lodixanol (Visipaque) □lopamidol (Isovue) □lopromide (Ultravist) □ioversol (Optiray) | | Iodine atoms to ions ratio is 3:2 | Increase ratio of iodine atom to particle 3:1 | | Dissociates into two molecular particles in blood plasma (Cations + and Anions -) _changed particle_ | No Charged Particles | | High osmolality (4–7x) more than of plasma. (Almost all CM reaction are due to hyper tonicity). | Low osmolality (2–3x) | | More causing allergic reactions | Less patient allergic reactions | ## Method of Administration and Usage Iodine CM * **Intravenous/intraarterial**: angiography, venography, IVU, CT scan * **Orally/rectally**: suspected perforated **organ** _viscous_, bowel preparation for CT scan * **Intrathecal**: myelography * **Intraluminal**: HSG, ERCP, cholangiogram, _inside lumen_ sinogram, fistulogram. * **Sinus/fistula** ## Oil Based * Are made from fatty acids, insoluble in water. * **Uses** * Broncography (lungs) * Tear ducts * Salivary glands * Lymphatic system * Hysterosalpingogram * Galactography (breast ducts) * **Risk of Fat Embolus** ## Images representing procedures using contrast media *There are 4 images on this page. Three black and white x-rays, and one image from a CT scan. The first image shows the outline of arteries in the upper torso, partially obscured by bones. The second image shows the outline of veins in the spinal column, partially obscured by bones. The third image has a white arrow pointing at a filled part of a lower torso, where some veins are filled with contrast medium. The fourth image shows a CT scan of a cross-section of the torso, partially obscured by bones. Arrows indicate the direction of the contrast medium. ## Images representing organs filled with contrast media *There are two images on this page. The first is a black and white x-ray of the vascular system of the left side of the head. The second is a black and white x-ray of a leg. The inside of the arteries are filled with contrast medium. The knee is circled in red, and the upper part of the calf, where much of the contrast medium is still present, is also highlighted with an arrow. ## Images representing a contrast study of kidneys *There are two images on this page, both black and white. The first is an x-ray of the kidneys. The second is a cross-section of the torso from a CT scan. The kidneys are outlined, and the contrast medium within them is highlighted with an arrow in the second image. There is some technical information, numbers and a date, at the bottom of the image. ## Benefit vs. Risk ## Adverse Effect ## Incidence of CM Reactions * Conventional Ionic Contrast Reactions - 10% * Minor:Major = 5%:0.1% | Reaction | HOCM | LOCM | |---|---|---| | Overall | 5-8% | 1-2% | | H/O Allergy | 10% | 3-4% | | Severe | 0.1% | 0.01% | | Fatal | 1/40-70k | 1/200-300k | ## Risk of CM Reaction * Previous adverse reactions to I-based contrast (3-6x) * History of asthma, allergy – steroid cover * Heart disease * Dehydration * Sickle cell anamea, polycythaemia DM and **myeloma** * Renal disease * Received large amount of CM within 24 hours ## Factors Contribute to Adverse Reactions: * **Viscosity** - (thick, sticky) harder to inject, more heat and vessel irritation (higher= greater viscosity) Warming contrast prior to injection will help. * **Osmolality** - is a measure of the total number of particles in solution. Ionic contrast media may lead to **hypovolemia** * **Toxicity** - (higher = greater viscosity) * **Miscibility** - easily mixes with blood ## CM Reaction Classification * **Immediate Reactions** were defined as those occurring within the department (within one hour). * **Delayed** as those occurring between the time the patients left the department and up to seven days later. ## Contrast Media Reaction | Mild | Moderate | Severe | |---|---|---| | nausea, vomiting Urticaria (hives) rash – itching Flush face – feeling of warmth Headace, Chills, Anxiety Diaphoresis | Hypotension (bradycardia) Hypertension (tachycardia) Dyspnea Bronchospasms/wheezing Laryngeal Edema | Laryngeal edema Convulsions Profound hypotension Clinically manifested arrhythmias Unresponsiveness Cardiopulmonary Arrest | | Treatment - does not usually get worse. Watch patient and reassure. | Needs immediate treatment - Keep IV line. Could lead to severe reactions. | PROMPT TREATMENT | ## Anaphylactoid (Idiosyncratic) * Unpredictable * Dose independent * Prevalence 1-2% (0.04 - 0.22% severe) * Fatal 1 in 70,000 (HOCM) ## Renal Toxicity * (increased serum creatinine > 0.5 mg%) * 2-7% * 5-10 x increase with pre-existing renal insufficiency * Nephrotoxixity direct relationship between serum creatinine * Hydrate 100 ml/hr of Normal saline 4 hrs prior to procedure, continue for 24 hours ## Contraindications for IV Contrast * No absolute contraindication. ## Relatives Contraindication * Renal Failure (monitor RFT) * Anuria _Abs_ _Usine_ * Asthma (possible allergies), allergic rhinitis, medication or food allergy – premed with steroid. * Cardiovascular disease * History of Contrast Allergy / Reactions * Diabetes - what medications is he taken * Multiple Myeloma ## Precaution Prior to IV Injection * Consent * Allergy History – increase reaction to CM * Past h/o allergy to CM – incidence increase 2x * Diabetes mellitus – patient on metformin, risk of lactic acidosis *Discontinue for 48 hrs after contrast* * Renal impairment - especially DM, paraproteinemia e.g myeloma. Tendency of worsening renal function – avoid dehydration. * Breast-feeding - 1% excreted in milk ## CM Extravasation * **Defines as**: escape of fluid from a vessel into the surrounding tissue, cause localized **_nomowing_ fluid** _Process of Seporr dead tissue broe_ vasoconstriction, resulting in sloughing of tissue and tissue necrosis if not reversed with an antidote. * Contrast material has seeped outside of vessel * Local redness and swelling * Apply warm compress 1st 24 hours * Cool compress for swelling ## Images representing extravasation *There are two images on this page, both of the upper arm. These are both black and white x-rays. The first image shows the arm from the side, the second, with an obvious and pronounced bulge, shows the arm from the front. The bulge is where the contrast medium has leaked out. ## Gastrografin * Water soluble * Not for iv injection * Poor mucosal coating *Basically used for R/O obstruction* * Won’t cause peritonitis if perforation * May cause severe chemical pneumonitis if aspirated * Osmotic pressure draws fluid into bowel lumen *Progressive distention in small bowel obstruction* *'Therapeutic' enema in constipation* ## Barium Sulphate (BaSO4) ## Barium Sulphate * Barium sulfate (BaSO4), chemical element with atomic number 56 * _reduction of force_ High attenuation of X-rays * _Cannot dissolve_ Insoluble in water, lack of absorption, and lack of toxicity. * High–density barium is preferred for fine-detail evaluation of the gastrointestinal system * Allergy to BaSO4 is very few reported ## Indication * Contrast study of GIT: Ba swallow, Ba meal and meal follow through, small bowel enema, barium enema, distal loopogram. * For better mucosal coating - different density of barium * Bowel preparation for CT scan examination – BaSO4 or Iodine, will increase lumen density ## Images revealing contrast media used in a bowel study *There are three images on this page. The first is a black and white x-ray, showing a long, thin, hollow tube. The second is an x-ray that appears to show the upper end of a large intestine. This area is circled in red. The last image, also a black and white x-ray, seems to show the lower intestine. ## Contraindication * Suspected perforation: *Eosophageal perforation – mediastinitis* *GIT perforation e.g injury, anastomotic leak – peritonitis, high fatality rate _Death_ * * If large volume aspiration – potential to plug the distal airways, cause gas exchange impairment. * p/h of allergic reaction (rare) * Left-sided colonic obstruction (relative contraindication) – potential become inspissated and hard, leading constipation ## MRI Contrast Media ## Why We Use Contrast Media in MRI * Improves the diagnostic accuracy of the MRI scan * Improves the visibility of inflammation, tumours, blood supply to organ, blood vessels ## Gadolinium Contrast Media * Complex molecules * Chemical bonds of gadolinium ion and a carrier molecule (a chelating agent). * Chelating agent prevents the toxicity of gadolinium while maintaining its contrast properties * Different brands use different chelating molecules ## Immediate Side Effect * Coldness at the site of injection * Notice mild nausea or headache - about 1-4% * Occasionally vomiting 1% * Mild allergy, skin rash ~ 1%. Usually settles down by itself * Severe allergic (anaphylactic) reactions are extremely rare 1/10000 ## Delay Side Effect: Nephrogenic Systemic Fibrosis (NSF) * Rare debilitating disease * _fitenira_ Skin contractures (or localized skin thickening and tightening) and internal organ damage. * Pre-existing factor: severe kidney function abnormalities. * Selective cases only * Newer agent reduced the risk of NSF ## Nephrogenic Systemic Fibrosis (NSF) * _exclude all DDX_ Nephrogenic systemic fibrosis (NSF) is a serious progressive clinico-pathologic entity that may progress to be fatal. * Diagnosis of exclusion - suspected in patients with variable skin rashes up to subcutaneous scleroderma-like plaques as well as variable systemic manifestations * Should be coupled with histological findings * Postulations : weak stability of gadolinium chelates leads to its free dissociation in tissues and induced fibrotic response in different body tissue ## Gadolinium Contrast * The use of renal protective agents such as N-acetylcysteine, sodium bicarbonate, diuretics, and **theophylline** is debatable and has not proven great benefits ## Other MRI Contrast Media * Manganese-based contrast agents: paramagnetic (Mn-DPDP) - detect hepatic lesions * Iron oxide contrast agents: superparamagnetic (SPIO) - successful outcomes in the diagnosis of liver tumors * Iron platinum contrast agents: superparamagnetic (SIPPs) - specifically target human prostate cancer ## Radionuclear Medicine Contrast Agent ## Radionuclear Medicine * radioactive material introduced into the patient – iv, oral, inhale etc. * γ Ray emitted by radionuclide * Detected by gamma camera ## Advantage of Nuclear Medicine * Ability to image qualitatively and quantitatively dynamic physiological processes of different body organs. * Radiopharmaceutical must be administered in different route, organ specific e.g iodine in thyroid or the physiological function of a particular organ (e.g. blood flow). * Radiopharmaceutical is typically made of two components i.e radionuclide and the chemical compound. ## Radioisotopes Commonly Used * technetium-99m * iodine-131 * fluorine -18 * nitrogen–13 * gallium-67, * krypton-81m * rubidium-82 * indium-111 * xenon-133 * thallium-201. ## Side Effect of Nuclear Imaging * Radioactive chemicals used in radionuclide scans are considered to be safe * Bleeding, soreness or swelling may develop at the injection site * Allergic reactions may occur, but extremely rare ## Strategies for Safe Clinical Practice to Reduce Risk for Renal Complications * Patients with SCr ≥ 2 g/dL and/or eGFR ≤ 60 mL/min per 1.73 m2 _Serum Creat_ Withhold contrast whenever possible and use alternative imagining modalities if feasible. Adequate hydration. Consider alternative diagnostic study if feasible. Avoid use of CM whenever possible. * Patients with end-stage renal disease who still produce urine Use lowest possible dose of contrast. Use intermediate to low osmolar and/or low risk GBCA followed by prompt dialysis if the patient is already undergoing dialysis. * Patients with end-stage renal disease who are anuria Can receive routine volumes of intravenous contrast material without risk for further renal damage or the need for urgent dialysis. ## Conclusion * Contrast agent will enhanced the normal and abnormal structures and hence it will improve the detection and extension of disease. * CM is not free from risk, use it if strong clinical indication. * CM reaction could occur as immediate or delay. ## Thank You

Contrast Media in Medical Imaging PDF 2024

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