Does contrast medium have any harm to the body?

Contrast agents are widely used in clinical practice. With the help of contrast agents, doctors can make better observations of patients' conditions through instruments and equipment, and make the diagnosis of diseases more accurate. For example, contrast agents are often used for fallopian tube angiography in gynecology, and the effect is worthy of recognition. However, some people worry that contrast agents will cause harm to the body. So, are there any harms to the body caused by contrast agents?

Contrast agents are chemicals that are injected or taken into human tissues or organs to enhance the effect of observation. Such as iodine preparations and barium sulfate commonly used in X-ray observation. It is generally believed that it is harmless to the human body. However, if the body is allergic, the contrast agent may cause allergic reactions, such as urticaria, angioedema, laryngeal edema, bronchospasm, and severe drop in blood pressure.

If the above symptoms occur, anti-allergic drugs should be used immediately and targeted treatment should be given to avoid damage to the body. 1. Classification of contrast agents:

1. Paramagnetic positive contrast agents (T1 effect, such as Gd-DTPA)

This type of contrast agent can shorten the T1 and T2 relaxation times of tissues. At low doses (<1mml/kg), the T1 effect is obvious and T1WI shows high signals.

2. Magnetic susceptibility negative contrast agents (T2 effect, such as Dy-DTPA)

This type of contrast agent causes loss of tissue signal by inducing changes in local MRI gradients, which is most obvious on T2-sensitive sequences and T2 gradient echo images.

3. Superparamagnetic iron oxide particles (SPIDs)

Its main function is to shorten the T2 relaxation time, so it is called T2 gradient echo contrast agent, but at very small doses, it manifests as a T1 enhancement effect.

2. Clinical Application

1. Central nervous system: It provides a basis for further localization and qualitative diagnosis of intracranial and intraspinal lesions.

(1) Discovery of lesions that are not visible on plain scan.

(2) Determine whether the tumor is extracerebral or intracerebral.

(3) Further display the internal conditions of the tumor and provide information for determining the treatment plan.

(4) Identification of edema and diseased tissue.

(5) To distinguish, to some extent, neoplastic lesions from non-neoplastic lesions.

2. Nasopharynx:

(1) It is helpful to determine the size, extent, and especially the depth of wetting of NPC.

(2) Showing signs of skull base metastasis and lymphatic tissue involvement.

(3) Follow-up after NPC treatment (especially radiotherapy).

3. Chest: focuses more on evaluating myocardial infarction.

(1) Differentiate between vascular and nonvascular lesions during mediastinal enhancement;

(2) It is helpful to display the false lumen of aortic dissecting aneurysm.

(3) The extent of intracardiac tumor invasion and the enhancement of the distinction between tumor and thrombus.

(4) Differentiate between reversible and irreversible myocardial damage.

(5) Breast imaging to differentiate scars after surgery or radiotherapy from tumor recurrence.

4. Abdomen: The liver is the main target of abdominal MRI scans

(1) Differentiation between diseased and normal liver tissue.

(2) Enhance the detection rate of small liver cancer lesions.

(3) It helps to distinguish the portal vein from the dilated bile duct.

(4) Differential diagnosis of intra- and extra-renal tumors; and the blood perfusion of the tumor.

5. Musculoskeletal system: Its sensitivity in bone metastasis is close to that of radionuclide scanning.

(1) Differentiate between bone tumors, aseptic necrosis, and parasympathetic dystrophy-related bone changes.

(2) Differentiate the histological types of bone tumors.

(3) Differentiation between changes in bone structure after treatment and tumor recurrence.

6. Contrast-enhanced MRI angiography: a non-invasive vascular imaging technique. Magnetic resonance imaging contrast agents have become the main display agents for this rapidly developing vascular imaging technology.

(1) Changes in vascular structure, such as stenosis, dilation, aneurysm, varicose vein, etc.

(2) To compensate for missed diagnosis caused by sudden changes in blood flow velocity and direction.

(3) The structures of small blood vessels and veins are displayed more clearly.