What is a Contrast Agent?

Contrast media (also called contrast media) are chemicals that are injected (or taken) into human tissues or organs to enhance the effect of image observation. The density of these articles is higher or lower than that of the surrounding tissue, and the contrast creates images with certain instruments. Such as X-ray observation of commonly used iodine preparations, barium sulfate and so on.

Chinese name: Contrast agent
Foreign name: contrast media

Alias: Contrast agent
Nature: Interventional radiology

Definition of contrast agent

Contrast is one of the most commonly used drugs in interventional radiology operations, and is mainly used for the display of blood vessels and body cavities. There are various types of contrast agents. Most of the contrast agents currently used in interventional radiology are iodine-containing preparations. Since the first successful femoral angiography with 50% sodium iodide in the United States in 1924, as with the development of interventional radiology, the contrast agent products have been continuously updated.

Contrast agent development

Production and development of iodine contrast agent

In the 1950s, triiodobenzene, the well-known Amidotrezoic Acid, was discovered, and the various contrast agents produced by it are still widely used today. This is the first leap in the history of modern contrast agents. Almost all of the iodine components of ionic contrast agents still in use are derived from it.

In the late 1960s, Swedish radiologist Almen proposed the concept of non-ionic contrast agents, and in 1971 reported the first non-ionic monomer contrast agent-Metrizamide (Amipaque). The emergence of volume contrast agents is the second leap in the history of modern contrast agents. Mefuglumide has the advantages of low osmotic pressure [485mmol / L (485mOsm.kg)] and good tolerance, but its performance is unstable.

The first generation of contrast agents was soon replaced by the second generation of non-ionic monomer contrast agents. Representative drugs were: iopanol (produced in 1974), iohexol (produced in 1976), iopamide (1979 Production), iomeprol (produced in 1979), iodopentol (produced in 1982), ioversol (produced in 1982), etc. These contrast agents have low osmotic pressure [500 ~ 700mOsm / kg] and are well tolerated And other characteristics, stable performance, high temperature sterilization, widely used.

In the late 1970s, non-ionic dimer contrast agents were developed to further reduce osmotic pressure. Among them, iotrolan is proved to have infinite water solubility, isotonic with body fluids at 300 mgl / ml, and is well tolerated. The disadvantage is that the relative molecular mass is too large (the relative molecular mass is 1626) and the viscosity is high. The emergence of non-ionic dimers is regarded as the third leap in the history of modern contrast agents. Iodixanol is also of the same kind, and its performance is similar to that of iodotril.

Contrast agent classification

Contrast agents can be divided into two categories, high-density contrast agents with high atomic weight and high specific gravity, and low-density contrast agents with low atomic weight and small specific gravity.

High-density contrast agents: Commonly used high-density contrast agents are barium sulfate and iodine preparations.

1. Barium sulfate: It is generally used for gastrointestinal angiography. It is made from pure medical barium sulfate powder with water to make a suspension. The concentration of barium sulfate is usually expressed in weight / volume (W / V). The concentration of barium sulfate used varies depending on the location and purpose of the inspection.

2. Iodine preparations: There are many types of iodine preparations, which can be divided into three categories, namely inorganic iodide, organic iodide, and iodized oil or fatty acid iodide.

Inorganic iodide is generally a 12.5% sodium iodide aqueous solution.

Can be used for fistula, urethra, bladder or retrograde pyelography. When used for cystography, it can be diluted 1 times.

Organic iodide: It is also a water-soluble iodine preparation.

Ionic type: Ionic contrast agents are divided into monoacid monomers and monoacid dimers according to their structure. Monoacid monomers are ubiquinone glucosamine (which can be used in various angiography and intravenous renal angiography. When used in different organs, the concentration is also different), iotaglucamine and so on. Monoacid dimers are represented by iodixamic acid.

The incidence of side effects of ionic contrast agents is high, and the body's tolerance is poor.

Non-ionic: such as iohexol, iopromide, and iopamidol.

Non-ionic iodine contrast agents have less toxic and side effects than ionic ones, and can be used for various angiographic and transvascular angiographic examinations. The incidence of non-ionic contrast agents is low, and the body is well tolerated.

non-ionic dimer: such as iotrolan (iotrolan), mostly used in spinal canal myelography.

(3) Iodized oil or fatty acid iodide: 40% of iodized oil is mainly used for bronchus, fistula and uterine fallopian tube angiography (cannot be used for cardiovascular angiography). Iodophenyl ester is a fatty acid iodide, which is an oily liquid. Because it is less irritating to tissues, it is suitable for spinal canal and ventricular angiography. In recent years, it has gradually been replaced by nonionic dimer iodotriol.

Contrast agents can also be classified according to the osmotic pressure of the drug, namely three types of hypertonicity, hypotonicity and isotonicity. Isotonic drugs are well tolerated. Too high or too low have different degrees of stimulation.

Contrast agent dosage

Contrast dose is an independent risk factor for contrast nephropathy. Cigarroa et al. Proposed a calculation formula for the amount of contrast agent: 5ml × body weight (Kg) / Cr (mg / dl), the maximum dosage does not exceed 300 ml. Studies have shown that the threshold dosage is exceeded, the incidence of contrast agent nephropathy is 21% -37%, and those who do not cross the threshold are 0% -2%.

Contrast agent response mechanism

Contrast reactions can be divided into specific reactions and physical-chemical reactions, the former has nothing to do with the dose, while the latter has a clear relationship with the dose.

Contrast agent specific response

Decades of research have shown that the diagnosis of urticaria, angioedema, laryngeal edema, bronchospasm, severe blood pressure drop, and sudden death in contrast agent responses are all idiosyncratic reactions, and their occurrence is related to the following factors.

Cell release media can stimulate the release of histamine from mast cells, whether ionic or non-ionic contrast agents. The content of histamine or its metabolites in urine was significantly higher in patients with contrast agent response than in those without contrast agent response.

Antigen-antibody response contrast agent is a hapten. Some groups in the contrast molecule can be combined with proteins in serum to form a complete antigen. Numerous studies have confirmed that part of the contrast agent response is an antigen-antibody response.

(3) Activated system contrast agents, especially ionic hypertonic contrast agents, can cause changes in blood cell and endothelial cell morphology and function, and can lead to the release of histamine, serotonin, bradykinin, platelet activating factor and other mediators.

Cholinergic contrast agents can produce cholinergic effects by inhibiting acetylcholine activity. Research results show that many types of iodine contrast agents have similar effects, so this effect is considered to be mainly iodine itself.

- Contrast Physics-Chemical Reactions

The incidence and severity of physical-chemical reactions are related to the amount of contrast agent used. The common nausea, vomiting, flushing, fever, and local pain in contrast agent reactions are caused by this. The related factors are as follows.

Osmotic pressure Because the osmotic pressure of currently used contrast agents is significantly higher than that of blood, which is 2 to 5 times, it is very easy to cause damage.

1) Endothelium and blood-brain barrier damage After the hypertonic contrast agent is injected into the blood vessel, the extracellular fluid osmotic pressure increases sharply, and the intracellular fluid is rapidly expelled, causing the endothelial cells to shrink, and the cell connections become loose and broken. A brain barrier is damaged, and the contrast medium leaks into the brain tissue space, exposing nerve cells to the danger of chemical toxicity of the contrast medium.

2) The hypertonicity of red blood cell damage makes the red blood cells hardened and deformed with spinous cells. As a result, red blood cells are difficult or unable to pass through the capillaries, causing microcirculation disturbance.

3) In addition to the expulsion of intracellular fluid, hypertonic contrast agents can allow interstitial fluid to enter capillaries, which can increase blood volume rapidly, up to 10% to 15%, resulting in increased heart load. But soon, with the extravasation of the contrast agent to the extravascular and osmotic diuretic effect, blood volume quickly returned to normal.

4) Although the overall incidence of nephrotoxicity-induced renal failure is low (<1%). It can reach 10% ~ 20% in patients with original renal insufficiency, and 60% of patients with contrast-induced nephropathy have a basis of azotemia.

5) Cardiotoxicity In addition to the high blood volume caused by contrast agents, in selective coronary angiography, high permeability can directly affect the sinoatrial node and cause slow heart rate. High permeability weakens inter-atrial conduction, indoor conduction, and repolarization, causes ECG changes, and increases the incidence of arrhythmia and ventricular fibrillation.

6) Pain and vasodilation In peripheral angiography, although the endothelial damage caused by hypertonic contrast agent is transient, the vascular pain produced is very obvious. In addition to osmotic pressure, this is also related to the hydrophobicity and ionicity of the contrast agent. Contrast agents can directly affect the smooth muscle of small arteries, causing local arterial dilatation, producing heat and discomfort.

The water-soluble contrast agent will not be reconciled as a foreign body unless it is sufficiently mixed with the surrounding liquid. The ideal contrast agent should have infinite water solubility, but because iodine atoms are highly hydrophobic, it is difficult to achieve infinite water solubility. The water-solubility in ionic contrast agent comes from the salt of cation, while the water-solubility in non-ionization contrast agent comes from the molecular core and reduces its binding with biological molecules, in order to reduce the biological activity of the contrast agent and reduce the response. The monomeric ionic contrast agent is more water-soluble than the non-ionic type, but the non-ionic dimer contrast agent iodotrimone has extremely high water solubility.

(3) Charged ionic contrast agents are composed of iodine-containing anions with contrast function and cations without contrast function. The former is negatively charged and the latter is positively charged. Charges can increase the conductivity of body fluids, disrupt the ionized environment and electrolyte balance, and affect normal physiological processes. The charge of the contrast agent has a greater effect on its water solubility and hydrophobicity, and can increase the binding of contrast to protein.

Viscosity Viscosity is determined by the concentration and shape of the solute particles, the interaction with the solution and the interaction between the solute particles, and is inversely proportional to temperature changes, but proportional to the iodine concentration, such as 300mgI / m1 The viscosity of troren was 9.1 cps and iohexol was 6.1 cps, but its viscosity at 280 mgl / ml was similar to the non-ionic monomer contrast agent iohexol 300 mg l / ml. After the injection of the contrast agent, the viscosity of the blood-contrast agent mixture can be increased, thereby reducing the blood flow. This condition can occur only in high shear force states (such as aorta) and low shear force states (venous and capillary circulation), but it is beneficial to improve the sharpness of development. For this reason, although the non-ionic dimer contrast agent has a higher viscosity than the monomer-based contrast agent, the former is unmatched by the latter in terms of its development effect and response.

Chemical toxicity Chemical toxicity is caused by the combination of hydrophobic regions in contrast agent molecules with biological macromolecules, which affects their normal functions, the so-called "hydrophobic effect". The first generation of non-ionizing agent mefuglumine introduced a large number of hydrophobic groups and failed to hide it, so it was very chemically toxic and was quickly eliminated. Subsequent non-ionic contrast agents can effectively cover the hydrophobic core with hydrophilic groups, so the toxicity is significantly reduced.

High-risk factors for contrast agents

1. Have a contrast agent allergy history

2. Allergies such as eczema, urticaria, neurodermatitis, asthma, food and pollen allergies

3 Hyperthyroidism, goiter

4 Patients with severe cardiovascular disease (such as cardiac insufficiency, coronary sclerosis, recent myocardial infarction, long-term heart rate irregularity, and severe hypertension, etc.)

5. Weak, dehydrated

6. Severe kidney disease

7. Severe liver disease

8. Severe diabetes

9. Severe pulmonary disorders (respiratory insufficiency, pulmonary hypertension, pulmonary embolism, etc.)

10 Brain injury (new cerebrovascular injury, convulsions, traumatic brain injury)

11. Paraproteinemia (Waldenstrom, macroglobulinemia, plasmacytoma)

12. Pheochromocytoma (risk of hypertension crisis)

13. Elderly people over 65 years old and infants and young children

14. Over anxiety

15. Recently used contrast agent

16. Use of B receptor blockers: easy to cause bronchospasm and bradycardia that may be difficult to treat

17. Long-term use of calcium antagonists: easily lead to bradycardia and vasodilation

18. Treatment with interleukin-2 and / or interferon

19. Use biguanide hypoglycemic drugs (easy to cause renal insufficiency, lactic acidemia)

20. Sickle cell anemia

Prevention of Contrast Agent Contrast

Although there is no perfect method to prevent the occurrence of contrast agent reactions, especially severe reactions, the following methods are worth using.

1. Correct treatment of contrast agent "allergy test" With the widespread use of non-ionic contrast agents, it is obviously unreasonable to judge the possible reactions of non-ionic contrast agents based on the test results of ionic contrast agents. Because the contrast agent response, especially the severe response, is often independent of the dose, a 1ml test dose may produce a fatal and specific response. In addition, because of different clinical understanding of the judgment standards, the false positive rate and false negative rate of this test are very high. For this reason, major foreign radiological societies and most hospitals do not conduct such "allergy tests", and some are limited to patients with a history of allergies, but the Chinese health department has not abandoned the test.

Preventive measures for high-risk patients

1) Use of low-volume non-ionic contrast agents

2) Pre-use antihistamine H1 receptor blockers: chlorpheniramine, 2-4 mg (1-2 ampoules), or phenagen, 4-8 mg (1-2 ampoules), before using contrast agents For the first 10-15 minutes, the group was injected intravenously slowly. H2 receptor blocker: cimetidine, 200-400 mg (1-2 ampoules), slowly intravenously or by adding 50 ml of 0.9% sodium chloride solution for injection.

3) Pre-oral administration of glucocorticoids: methylprednisolone, intravenous administration of prednisolone or methylprednisolone in the first 24 hours, 12 hours, and 40 mg of oral contrast medium respectively, 250 Mg, intravenously 30 minutes before contrast

4) Stabilize the cardiovascular system

5) Maintain water, electrolyte and acid-base balance

6) Avoid the use of nephrotoxic drugs (such as non-steroidal antirheumatic drugs, amphotericin B, cisplatin, aminoglycosides and cephalosporins, metformin)

7) For sedation, take 10 mg orally. Take care to avoid causing respiratory depression!

8) In order to maintain the autonomy of thyroxine function, 40 and 20 drops of sodium chlorate were used before and 2 hours after the angiography, and 15 drops each time three times a week after the angiography.

9) Patients with hyperthyroidism can use X-ray contrast agents only when necessary, and need to increase the use of methimazole 20 mg daily for 1-2 weeks.

10) Patients with pheochromocytoma should first give A receptor blockers to avoid hypertension crisis.

3 Use of non-ionic contrast agents as much as possible. A large number of clinical practices have shown that the total incidence of severe non-ionic contrast agents and the incidence of severe reactions are significantly lower than those of ionic contrast agents. Non-ionic dimer contrast agents are more safe. high. For this reason, although it is expensive, from all aspects, non-ionic contrast agents should be used as much as possible, especially in special parts such as coronary arteries, cerebrovascular, heart, pulmonary arteries and limbs. Although the safety of non-ionic contrast agents is high, due to the large amount of drugs entering the blood in a short period of time (1ml contrast agent contains 500 ~ 760mg drugs), it is by no means non-responsive and there are still deaths, so it must not be taken lightly .

4 Studies on reducing the amount of contrast agent have shown that the physical-chemical reaction in the contrast agent response has a clear proportional relationship with the contrast dose used. Reducing unnecessary doses can reduce or alleviate the reaction of the agent. For this reason, before each angiography operation, we must know what we are thinking about, and try to avoid angiography failure or repeated angiography caused by technical operation factors. Of course, if selective blood vessels are required, the radiography should be repeated or re-radiated. Some people also use radiography after a few days. For selective angiography of difficult patients, sometimes non-selective angiography is performed to clarify the blood vessels before selective intubation, which can reduce the contrast dose and X-ray volume.

5. Note that the incidence of contrast agent response is different for different injection methods, and different injection techniques for different angiographic examinations should be strictly controlled to avoid increasing the incidence.

Classification and treatment of contrast agent response

Contrast Review

After using the contrast agent, the patient needs to stay in observation for at least 30 minutes, because 90% of side effects occur during this period. High-risk patients should remain in observation for longer. Delayed reactions (abnormal skin changes and cardiovascular disorders) can still occur in rare cases. If the symptoms are severe, they should be observed and treated in intensive care.

Contrast agent first-order side effect

Symptoms: sneezing, coughing, yawning, skin redness, low fever, nausea, vomiting, chills.

Measures: 1. Stop injection. 2. Establish a venous channel. 3 Give antiemetics such as triflurazine and ondansetron.

Symptoms: flushing, pruritus, hives, puffy eyelids.

Measures: 1. Intravenous injection of H1 or H2 receptor blockers, such as 8-12 mg of dimethylindene (2-3 ampoules), 4-6 mg (2-3 ampoules) of clomustine (pyrrolol by amine) or Cimetidine 400 mg (2 ampoules). 2. Intravenous glucocorticoids (equivalent to 250 mg of prednisolone) if necessary.

Contrast secondary reaction

Symptoms: blood pressure drops

Measures: 1. Lie flat and keep fresh air 2. 2. Nasal catheter or oxygen supplied by a mask. Rapid infusion of plasma substitute or Ringer's solution (500-1000 ml)

Symptoms: when blood pressure drops with bradycardia (vasovagal response)

Measures: In addition to the above measures, increase atropine 0.3 mg, intravenous or metaisoproterenol, 0.25-0.5 mg (0.5-1 ampoules), slowly intravenously.

Symptoms: when blood pressure drops with dyspnea, spastic cough

Measures: In addition to the above measures, spray bronchodilator aerosol sprays, 0.24 grams of aminophylline intravenously. Glucocorticoids (equivalent to 250-500 mg of prednisolone) are given intravenously and they take effect after 5-10 minutes. Oxygen is supplied to the mask in the semi-sitting position. If necessary, intravenous diazepam 5 mg can be given to sedate the patient.

Contrast agent tertiary side effect

Symptoms: Shock (tachycardia, sudden drop in blood pressure)

Measures: Follow the emergency procedures, immediately notify the emergency team, anesthetist, emergency department physician, give oxygen in a half-position mask, quickly inject plasma substitute or Ringer's solution (1500-2000 ml), epinephrine, 0.1-0.3 mg , Static note. Check heart function every 10-15 minutes. The dosage depends on the treatment effect, and the maximum dose is 1 mg (1 ampoule of epinephrine is diluted 1: 1000, that is, 1 ml is equivalent to 0.1 mg of epinephrine). In emergencies, if venous access cannot be found, double-dose intubation can be injected into the bronchi, or it can be injected intramuscularly or subcutaneously into the subglottic venous plexus. H1 or H2 receptor blocker, used in the same way as the first side reaction. Intravenous glucocorticoids (equivalent to 200-500 mg of prednisolone) are effective after 5-10 minutes. Dopamine (200 mg, 2 ampoules) is added to 250 ml of solution in the field, 15-30 drops per minute, intravenously, the dosage depends on the effect. If reflex hypotension occurs, give norepinephrine (5-10 mg in 250 ml of solution). Dosage depends on patient response.

Symptoms: broncho (laryngeal) spasm, wheezing, acute attack of asthma

Measures: Place the patient in a sitting position, give mask, oxygen, aminophylline, 0.24 mg, intravenous injection, epinephrine, 0.1-0.3 mg, intravenous injection, if necessary, increase the amount to 1.0 mg (1: 1000 ampoule adrenaline Dilute, ie 1 ml is equivalent to 0.1 mg of adrenaline). H1 or H2 receptor negative drug withdrawal, usage is the same as the first-level side effects. Intravenous glucocorticoid (equivalent to 250-500 mg of prednisolone), effective after 5-10 minutes. Give azepam 5 mg as needed, intravenously. Intubate if necessary.

Symptoms: edema of the throat

Measures: feasible tracheal intubation, or puncture the trachea with a large needle to give oxygen, and cut the trachea if necessary. Symptoms: pulmonary edema

Measures: feasible tracheal intubation, pressurized oxygen, and intravenous injection of furanilic acid (fast urine) 40 mg, morphine 10-15 mg, slowly intravenous injection.

Symptoms: Convulsions

Measures: Diazepam, 5-10 mg, intravenous injection.

Fourth-order side effect of contrast medium

Symptoms: respiratory cycle stops

Action: Immediate CPR (external chest compressions, artificial respiration, etc.).

Contrast common sense questions and answers

What is a contrast agent (formerly known as a contrast agent)?

Contrast is a diagnostic drug, the main ingredient is iodine. The characteristic of iodine is that it is impermeable to X-rays, so when taking X-rays, you can use the distribution of iodine in the body to make a contrast; or make clear the blood vessels and soft tissues that are usually invisible on X-rays to help doctors make reliable Diagnosis. Contrast agents can be injected into arteries or veins and are quickly distributed throughout the vascular system. Contrast agents are not metabolized ("used out") or changed in the body, they are excreted through the urinary system.

Why is the use of contrast media necessary?

Because many tissue structures of the human body are not visualized on X-ray films, they can only be "deepened" by using a contrast agent. Some X-ray examination techniques, such as angiography, cannot be performed without the contrast agent. In some technologies (such as CT), although contrast is not always necessary, the use of contrast will make the diagnostic image clearer and help the doctor make a more reliable diagnosis for you.

What are the benefits of using contrast agents?

Because the contrast agent can increase the difference between normal and abnormal tissues, it can help doctors detect the abnormal morphological structure and functional damage of human organs. And enable doctors to find and identify some early, small lesions (liver lesions, etc.). Without contrast agents, these lesions may go undetected and cause missed diagnosis or misdiagnosis. In addition, contrast agents can also help radiologists distinguish between benign lesions that generally do not require treatment and malignant lesions that require urgent treatment.

How safe is the contrast agent for the human body?

Conventional contrast agents currently used are quite safe under normal circumstances. However, some patients may still have mild or moderate adverse reactions, and in rare cases, serious adverse reactions may occur. A few years ago, a clinical study involving more than 337,000 cases was carried out in Japan. The results showed that the incidence of serious reactions was very low, and the incidence of mild adverse reactions was very low, regardless of ionic or non-ionic contrast agents. The rate is also very low. However, the use of non-ionic contrast agents is safer and has fewer adverse reactions than ionic contrast agents.

What issues should be paid attention to when drawing contrast media and injecting contrast media with infusion devices?

First, the contrast bottle stopper should be punctured with a needle or infusion set needle as thin as possible and with a long bevel when extracting the contrast. The use of thick needles (such as 2.0mm short bevel needles for conventional venipuncture) will increase the risk of debris generation, that is, the rubber particles at the puncture site will fall off. Secondly, repeated punctures in the same area of the rubber stopper should be avoided, as this will greatly increase the risk of debris. Due to the viscosity of the contrast medium, special needles or suction needles with liquid filtration devices cannot be used. On the other hand, the infusion device should use a filter to ensure sufficient liquid flow. When the contrast agent is heated to body temperature, its viscosity will be reduced by about half, so it is much easier to pump warmed contrast agent (especially high concentration preparations) into the syringe.

How long can the contrast medium be used after it is opened?

In general, any remaining contrast medium should be discarded during the examination. As a guideline, the maximum time between the use of the contrast medium after opening the bottle or drawing it into other input devices should not exceed 4 hours. The more likely time is to have a thermal response to microbial or bacterial growth. During this period, seeding due to volatilization can quickly cause the entire bottle contents to crystallize. In addition, the danger of drug degradation caused by light also exists. If the injection stays in the disposable syringe for several hours, it will absorb the sulfurized additives in the piston, which will undoubtedly harm the patient.

What factors can reduce the stability of X-ray contrast agents? What should be paid attention to when storing contrast media?

Generally speaking, there is a certain difference between long-term storage and temporary storage. From a pharmacokinetic perspective, temporary storage has no significant effect on contrast media. X-ray contrast agents should be stored at room temperature of 15 ~ 25 , and avoid light. The contrast medium can be placed in a heating cabinet for a short time, for example, the preparation is heated to 37 ° C before the injection or infusion. The contrast medium can be stored in a heating cabinet or immersed in hot water to about 40 ° C for a day or several days. Contrast can also be safely placed in hot water for a short time heating, for example: heating to 60 ~ 80 can dissolve the crystals of the contrast. This can not help us think of another problem that the contrast changes, that is, during transportation in winter The contrast agent liquid will undergo pure physical crystallization. Please keep in mind that the contrast agents we use are usually high concentrations, and their concentration is related to the iodine content. The Euvitamin 370 preparation containing 370 mg of iodine per milliliter has a concentration of 0.769 g of ioprolamide per milliliter, that is, it is a 76.9% preparation. Liquid formulations can freeze at very low temperatures. However, experience has shown that not all substances in the bottle will crystallize at low temperatures, because crystallization requires seed crystals, and frozen formulations can be heated in hot water or kept at room temperature for a period of time and shaken again and then stored. In general, make sure that the formulation contains no small particles, especially crystals, before using the contrast medium. The effect of light on contrast agent stability is much greater than heating. The main changes caused by light are the increase in the iodide composition and the decrease in pH, which leads to the separation of the acidic substances contained in the ionic builder.

There is no clear rule on how long the contrast medium can be stored under light. The results of contrast medium stability experiments require contrast medium to be stored away from light. This is mainly because the degree of degradation caused by light mainly depends on the brightness of the light and the near-ultraviolet spectrum in sunlight and sunlight, which are very active in photochemical reactions. These factors depend on the type of light; daylight depends on the degree of sunnyness of the sky to have a geographical location. In general, the contrast agent is exposed to a general working room with a light of 600 LUX for a whole day and its stability Sex is not affected much. However, it should be avoided in any case, even for a short time. In addition to the high brightness, sunlight also contains a large amount of ultraviolet light, which can form a strong photochemical reaction. The contrast agent is not only destroyed by short-wave light, but also by X-rays. Therefore, do not store the contrast agent for a long time within the range that X can cover. However, during the diagnosis or examination, the placement of contrast medium for a short time is allowed.

Compared with ionic, the advantages of non-ionic contrast agent

It does not decompose into ions in the solution and does not participate in the metabolic process of the body, so it has the advantages of water solubility and strong dispersion power. In addition, it does not have a charge, so it does not interfere with the electrical balance of the human body and does not interact with calcium ions, so it does not affect the blood calcium concentration, thereby avoiding adverse reactions caused by changes in calcium concentration. Its low protein-binding rate in solution has the advantages of low osmotic pressure, low chemical toxicity, low viscosity, and fast absorption, thereby enhancing the tolerance of the tissue to the contrast agent, and rarely causing serious ions that are prone to ionic contrast agents side effects. At the same time, it has very little effect on the blood-brain barrier, and in terms of image quality, high-contrast images can be obtained.

Future development of contrast agents

In the era of the medical imaging market, portable ultrasound has a strong appeal. One of the obstacles to the development of ultrasound is the problem of contrast agents. Contrast agents can greatly improve image quality and diagnostic results. For some diagnoses, they will be one of the key factors that help ultrasound effectively compete with MRI and CT. MRI and CT examinations often use contrast agents. MRI has superparamagnetic iron oxide ( SPIO ), but few contrast agents can be used for ultrasound. Even among these small amounts of contrast agents, some applications are controversial. The US FDA and European Medicines Product Evaluation Agency have also warned against the use of these contrast agents in some heart diseases. Medical experts are lobbying against these rulings. If these market regulatory obstacles are removed, it will have a significant impact on the market growth of ultrasound and ultrasound contrast agents.