All of the scrutinies designated as particular or advanced processs require the debut of some type of stuff into the country of involvement to supply contrast. this is necessary because the differences in denseness among the assorted in the organic structure are excessively little to supply equal contrast for visual image of anatomic inside informations. to counterbalance for this, it is necessary to increase or diminish the denseness of the organ to supply the coveted contrast. Approximately 90 % of all contrast media used in xray imagination are slackly termed intravascular or general contrast media.The physical belongingss of the I based contrast media include the ions or atoms associated with the chemical dislocation of the contrast media when it enters a solution, the figure & A ; size of the I molecules, & A ; the figure & A ; size of the molecules of any chemical additive. The development of contrast agents in 1972, a new agent was introduced for radiculography. This was produced by associating two iothalamtemolecules together to organize a dimer ( Dimer X ) . Dimer X overly toxic to patients & A ; was withdrawn from UK. Manufacturers needed to do a contrast agent, which is as near to the osmolarity of blood plasma ( 270 mOsmols/kg H2O ) as possible. Make a low osmolar contrast media by associating together two tri-iodinated benzoic acid derived functions & A ; replacing one of the acid carboxyl groups with a non ionizing group. In solution this gives six atoms of I and two atoms. This type of contrast media can be used in a more dilute signifier ( ie with saline ) & A ; hence cut downing the effectual osmolarity ( about 690 mOsmols/kg H2O ) . They are two type of contrast media, negative contrast agent and positive contrast agent.Negative contrast agent is
The soaking up of x-ray by a substance is dependent upon several factors, one of which is the atomic weight the substance. Negative contrast agent is radiolucent, low atomic figure of stuff, black on movie and their illustration are air, O and C dioxide Those stuffs that have lower atomic weight will rarefy less radiation. The attendant leftover radiation will bring forth a greater radiographic denseness ( darker image ) on the image receptor. This characteristic is utile when the aim is to show an anatomic construction against the dark background or to supply a silhouette image of the construction. Example of radiolucent or negative, contrast agent are air, C dioxide and H2O. Air is introduces by the patient during a radiographic scrutiny illustration inspiration during chest skiagraphy or can besides be introduced by the radiographer as portion of the scrutiny in a dual contrast Ba clyster. introduced into pits of the organic structure for illustration in the articulatio genus when executing an arthrogram to show the articulatio genus articulation. Carbon dioxide is introduced into the GI piece of land in concurrence with a Ba sulfate solution to show the mucosal form for illustration dual contrast Ba meal.carbon dioxide can be used as the negative contrast agent in a dual contrast Ba clyster, instead than air, as it causes less immediate abdominal hurting every bit good as less postprocedural hurting and uncomfortableness. However, some surveies have shown that C dioxide produces inferior distention and extra insufflations are required to keep equal quality distention. Carbon dioxide can besides be used as an alternate contrast to ionated contrasts for diagnostic angiography and vascular intercessions in both the arterial and venous circulation. the gas produce negative contrast due to its low atomic figure and low denseness compared with next tissues. Most of available gases have been used as negative contrast agent with changing consequence, nevertheless the four gases listed here are the most normally used negative contrast agents. The negative contrast agent can besides be used in concurrence with a positive contrast agent. One common process that used this combination of contrast agent is the dual contrast Ba clyster. Air and O may be unsafe during certain process because they can do gas emboli, but C dioxide and N do non present the hazard of gas emboli and can be used with comparative safety. they are besides able to be absorbed quickly by the organic structure. this factor can be advantageous when rapid soaking up is desired, but in instances in which many radiograms are taken, it is definite disadvantages. Because of their high atomic figure, positive contrast agent cause an addition in the fading of a-ray and are considered to be radio-opaque. Positive contrast media is radio-opaque, high atomic figure of stuff, white on movie and their illustration are Br, I, and Ba. They produce an country of lessening radiographic denseness on the image receptor. Contrast agents that are radio-opaque contain component with high atomic figure such as I, Br and Ba. When these substances are used to make full organ, they basically make the organ radiopaque, and the image appears clear or white on the radiogram. They can take the signifier of tablets, pulverizations, and liquids and can be introduced into the organic structure through a assortment of paths. They are comparatively in non toxic in most instances, but certain patients may exhibit reactions of changing badness, particularly to agents incorporating I. In some instances, little doses of these agents may do decease. the positive contrast agent used during the advanced processs discussed in this text will be organic I compound. An ionic compound dissociates ( dissolves ) into charged atoms when it enters a solution ( illustration: blood ) . Ionic media breakdown into cations ( +ive charged atoms ) & A ; anions ( -ive charged atoms ) . Five times the osmolarity of human plasma ( hyperosmolar ) . Example: Conray 280, 325 & A ; 420 ( The figure refers to the iodine concentration in mg/ml-1 ) .It is Monomer and dissociates into 2 atoms in the blood. Non-ionic contrast media do non fade out into charged atoms when it enters a solution. For every three I molecules in a non-ionic solution, one impersonal molecule is produced. Frequently referred to as “ low osmolar ” . It have 3:1 compounds. Far safer than ionic contrast agents. Example: Omnipaque 140,180,240,300,350.Dimer and does non disassociate. Generally isomer, more syrupy than ionic and besides more hydrophilic. The extra chemical groups determine the belongingss of the contrast agent. There are solubility, viscousness and osmolarity. Properties of Water-soluble Injectibles are, low toxicity, high opacity, low viscousness, high miscibility. Viscosity describes the thickness or opposition to flux of a contrast agent. The thickness of the contrast agent is related to the concentration, the size of the molecules in a specific contrast agent & A ; the temperature of the contrast agent. The viscousness affects the rate that the contrast media can be injected. High viscousness cause harm to vessel endothelia, blood encephalon barrier, nephritic tubule. The osmolarity of a solution is the measuring of the figure of molecules & A ; atoms in a solution per kg of water.If cells in a organ are surrounded by a solution of greater osmolarity than the cellular fluid, H2O will go forth the cells which will finally shrivel & amp ; distort, sometimes being disrupted wholly ( Dawson 1984 ) . Fluid displacements can hold a annihilating consequence on patients. ( The osmolarity value of blood plasma & A ; CSF = 270, where as Ionic CM ( monomer ) = 1400 ) . Enhance capable contrast or render high capable contrast in a tissue that usually has low capable contrast.Therefore altering the Subject contrast will alter the Radiographic contrast and movie contrast. Visualize variety meats, multitudes, etc. otherwise unable to be differentiated ( by imaging ) otherwise. Designation of alterations in vasculature and vascular unity. Follow blood, lymph or serosal pit fluid flow. Contrast media is needed because soft tissue has a low absorption/interaction ratio. Absorption is dependent on atomic figure, atomic densit, negatron denseness, portion thickness, K-shell adhering energy ( K-edge ) , P-E interaction is the procedure of soaking up. Treatment of inauspicious reactions to contrast medium has already been stated that all patient must be keep under changeless observation during and after contrast media disposal, and exigency drugs and O should be ready available if required. contrast media should be administered at organic structure temperature and the maker ‘s optimum does should non be exceeded. this minimizes the hazard of an inauspicious reaction. Before originating any intervention, the badness of the event should be carefully evaluated, this guarantee the appropriate intervention can be given. reaction to endovenous disposal of contrast media can be classified into three classs inauspicious Reactions ( Mild reaction ) , Adverse Reactions ( Moderate reaction ) and Adverse Reactions ( Severe reaction ) .Mild reaction is merely needed careful observation of the patient. Most of the symptoms will go through within a few proceedingss post disposal. Sign and symptoms are of mild reaction are, nausea & A ; purging, cough, heat ( heat ) , flushed esthesis, concern & A ; giddiness, metallic gustatory sensation in oral cavity, perspiration ( workout suits ) , urticaria ( urtications ) , anxiousness, Itching, lividness, icinesss, shudders ( agitating ) , rhinal stuffiness, swelling of eyes or face. Treatment for the mild reaction are observation & A ; reassurance merely. Normally no medical intervention is required and the reaction does non interfere significantly with the scrutiny process making under taken. Sign and symptom for inauspicious Reactions ( Moderate reaction ) are pulse alteration, hypotension, high blood pressure, dyspnoea, bronchospasm, laryngospasm, erythema, pruritis, abdominal hurting. Treatment-Close observation, Treat symptoms. Compaction and tight vesture should be release and the patient reassured. the patient will necessitate to be seen by a trefoil and the inauspicious reaction required information to be entered in the patient ‘s lasting medical record. Drug therapy mat be required, such as disposal of anantihistamine ( eg: Piriton 10md ) intravenously, or epinephrine ( adrenaline ) 0.5 mL 1:1000 solution subcutaneously, to cut down the symptoms. While Adverse Reactions ( Severe reaction ) potentially life endangering mild & A ; moderate marks & A ; symptoms plus unresponsiveness, paroxysms, clinically manifest arrhythmias, cardiorespiratory apprehension, nephritic failure and decease. The above categorization mild, moderate and terrible do non try to separate between allergic-like and non-allergic like reaction. Rather, they encompass the spectrum of inauspicious events that can be seen following the intravascular injection pf contrast media. A demand of a Contrast Agent is easy to administrate, no toxicity, stable compound. Will non disassociate into toxic ions. When injected the media dressed ores in country ( s ) required illustration in order to bring forth good contrast. The agent ‘s physical characteristics allow the organ to be decently demonstrated ( non-flocculating ) illustration even barium coating of the tummy in the presence of an acerb environment. The agent should hold rapid riddance. The agent should non be carcinogenic. The agent should hold a viscousness appropriate to the patient when introduced. The agent should do minimum hurt to the patient when introduced. The agent should be cost-efficient. Examples of countries where contrast agents are used in Arteriography- Mesenteric arterias, Angiography ( DSA ) – Cardiology, Venography ( replaced by ultrasound- Doppler ) , IVU, Fluoroscopy – Alimentary piece of land, hyserosalpingography, sialography, dacrocystography, computerised Tomography ( CT ) , Magnetic Resonance Imaging ( MRI ) , Ultrasound – Liver, kidney, Myelography ( replaced by MRI ) and Arthrography – Knee articulations. The followers is the sum-up of somme general safeguard to be taken earlier and after the disposal of contrast media. Before injection, discourse the process with the patient, obtain an informed consent from the patient, set up a set of baseline critical marks, know the patient, look into the chart for history of allergic reaction or hypersensitivity, look into the consequences of the patient ‘s blood work for illustration blood urea N, creatinine, prothombin clip, in instances of arterial entree, partial thrombokinase clip, thrombocyte count, look into wheather patient has other medical jobs such as hepatic or nephritic diesease, gestation, multiple myeloma, congestive bosom failure, Gravess ‘ disease, homozygosity for reaping hook cell disease, bronchiole asthma, thyrotoxicosis. We must cognize the process of contraindication and restriction to the specific particular process, know the possible reaction that can happen with the contrast agent used, look into exigency equipment and cognize location and content of crash cart. After injection, cognize where doctor may be reached, evaluated patient ‘s critical map for abnormalcies of respiration, pulse, blood force per unit area, presence of cyanosis. Stay with and supervise the patient for at least 20 proceedingss after injection. Iodised Oils is infrequently used in skiagraphy. It used where water-soluble agents are contraindicated or where a syrupy compound is required. Not easy absorbed & A ; in some fortunes, carry a hazard of oil-embolus. It formed from poppy seed oil & A ; illustrations include Lipiodol & A ; Myodil. Safety advanteages utilizations of contrast media are Smoother blood flow, no harm to the endothelium and to blood cell. No harm to the blood encephalon barrier and to renal tubule. Ergonomis advantages usage of contrast media are Use of higher concentration, usage of smaller diameter catheters, less invasive process and easier manual injection.
illustration of positive contrast media