Radiographic Contrast Media PDF

SPECIAL PROCEDURE-1- RADIOGRAPHIC CONTRAST MEDIA BY SUHA R. HILAL  RADIOGRAPHIC CONTRAST MEDIA CONTRAST - It is the difference in optical density between different parts of image. -Any substance that make an organ or structure more visible than without it's addition. -A...

SPECIAL PROCEDURE-1- RADIOGRAPHIC CONTRAST MEDIA BY SUHA R. HILAL  RADIOGRAPHIC CONTRAST MEDIA CONTRAST - It is the difference in optical density between different parts of image. -Any substance that make an organ or structure more visible than without it's addition. -Any substance that allows visualization of structures that cannot be seen under normal circumstances.  History of contrast media 1896-WALTER BRADFORD discovered contrast media. 1897- First reported GI contrast study performed using Bismuth- TOXIC! 1910- Barium Sulphate used (safer) 1920’s- Sodium Iodide used which is a treatment for syphilis. Iodine was found to be radio opaque to x-rays. 1927 - First reported IVU with iodised organic salts (Uroselectan) - As you must know from physics of x ray when x ray beam hit an object (patient's body or body part) attenuation will happen to that beam with different attenuation values according to the composition of the object itself ( bone , air , fluid, soft tissues ). - Air attenuation …. Negligible ( due to low density) - Bone attenuation …Significant (due to high density) - Soft tissues … similar to water - Low attenuating material means it allow radiation to pass through it freely and called (radiolucence) black color on x ray film.. - High attenuating material means it inhibit the passage of radiation through it and called (radiopaque) white color on x ray film.. - If the two organs have similar densities , then it is not possible to distinguish them on a radiograph, because no natural contrast exists.. - Radiographic contrast media were developed to increase differences in the attenuation (absorption) of radiation by soft tissues.  Classification 1- Radiographic contrast agents.. 2- MRI contrast agents.. 3- Ultrasound contrast agents.. Radiographic contrast media are divided into positive and negative contrast agents. 1- The positive contrast media attenuate X-rays more than do the body soft tissues.. 2- The Negative contrast media attenuate X-rays less than do the body soft tissues. The positive contrast media divided into 1-Water-soluble iodine-based agents. 2- Non-water-soluble barium agents. Which are radiopaque materials and appear white on film. The Negative contrast media like 1- Air 2- Carbon dioxide Which are radiolucent materials and appear black on film.  Barium examination of GIT 1- Barium swallow (esophagus) 2- Barium meal (stomach) 3- Barium meal follow through (stomach & small intestine) 4- Barium enema (colon) [ Barium have a drink]  Positive contrast media 1- Water-soluble iodine-based agents. 2- Non-water-soluble barium agents. Water-soluble contrast media - Oral used [Gastrographin] - IV injection [Urographin , Telrbrix] - Intra thecal [ Iohexol]  Water-soluble iodine-based agents Chemical composition :- are based on a benzene ring to which three iodine atoms (I) are attached. 1- A monomer contains one benzene ring tri-iodinated 2- A dimer contains two benzene rings tri-iodinated - Iodine is radiopaque material so , it is used in composition of contrast media , - when there is more iodine give more contrast so, dimers ( have 6 iodine atoms ) are better than monomers (have 3 iodine atoms) as a more powerful contrast ability.. - Iodine-based contrast agents can be divided into two groups, ionic and non-ionic,basedon their water solubility NON -IONIC CM IONIC CM Low osmolality High osmolality Lower risk Higher risk High cost $ Low cost $ No electrical charge( that is electrical charged (which is why called Non ionic) responsible For the side effect of CM )  Osmolality Osmolality describes the concentration of solute per kg of water The osmolality of CM solutions is expressed in millios mol/kg water The osmolality of CM is dependent on the concentration  Ionic contrast media(HOCM) High Osmolar Contrast Media (HOCM) - Composed of salts which dissociate in water into anions (radiopaque) and cations. - Osmolality up to 5x serum osmolality (toxicity). - E.g. Gastrografin, Urografin, Isteropac  Non–ionic contrast media Low Osmolar Contrast media (LOCM) 1-Non-dissociating. 2-Only about 2x serum osmolality. 3-Less side effects, less nephrotoxic. 4-E.g. Ultravist, Omnipaque Iso-osmolar Contrast Media (ISOCM) 1- Osmolality approximately equals serum osmolality. 2- Preferred in renal impaired patients. 3-E.g. Visipaque Note The low- and iso-osmolar contrast media are( 5–10 ) times safer than the HOCM and are used routinely in clinical practice  IDEAL CONTRAST MEDIA 1- High water solubility. 2- Heat & chemical stability(shelf life) ideally 3 to 5yrs. 3- Biological inertness ( non antigenic). 4- Low viscosity. 5- Low or iso osmolar to plasma. 6- Selective excretion, like excretion by kidney is favorable. 7- Safety: LD50 (lethal dose) should be high. 8- Reasonable cost.  Commonly used preparations Ionic contrast media : 1- Urograffin 2- Gastrograffin 3- Angiograffin 4- Trazograph 5- Conray  Most commonly used media Non ionic monomers 1- Omnipaque 2- Optiray 3- Ultravist 4- Lek-Pamidol 5- Iopamiro  Non ionic dimers : 1- Isovist 2- Visipaque