CT angiography is a modern high-tech diagnostic technique used to study the condition of blood vessels and assess the speed of blood flow. CT angiography is a method of radiation diagnosis. The use of special computer programs allows you to recreate three-dimensional images of vascular networks, assess the blood supply to various anatomical areas, accurately localize areas of blood flow disorders and determine the cause of these disorders. Due to the high information content and affordable price, CT angiography has taken a worthy place in the list of methods used in the diagnosis of pathology of arteries, veins and lymphatic vessels. It is widely used in vascular surgery, phlebology, therapy, rheumatology, neurology and other fields of medicine.
CT angiography is a relatively new technique. It began to be introduced into clinical practice in the 80s of the last century, after the American physicist Cormack in 1963 developed algorithms for computer image reconstruction based on X-ray data, and the British engineer Hounsfield in 1972 designed the first computer tomograph. CT angiography is an improved version of classical angiography – a study in which a contrast agent is first injected into the vessels of the patient, and then a series of images are taken.
However, CT angiography has fundamental differences from conventional angiography. Studying conventional radiographs, the doctor works with a two-dimensional image of the three-dimensional structure of the vascular network in two or three projections. At the same time, due to the superposition of layers of tissues on top of each other, some of the information is lost. When working with CT angiography data, a specialist can study the model of the bloodstream “in volume”, changing the viewing angle, bringing individual sections closer, etc. This makes it possible to obtain the most complete and reliable information about the number, location and patency of blood vessels, accurately localize pathologically altered areas, assess the extent and degree of patency disorders, determine the severity of blood and lymph supply disorders.
Types of CT
Taking into account the type of vessels studied, there are three types of CT angiography: CT-arteriography (examination of arteries), CT-venography (examination of veins), CT-lymphography (examination of lymphatic vessels). This technique allows you to get information about the state of the vessels of any anatomical zone. The most popular types of CT angiography are:
- Cerebral CT angiography – examination of the arteries of the brain.
- CT angiocardiography is a study of the heart vessels.
- CT-aortography is a study of the arch, descending and ascending parts of the aorta.
- CT angiography of abdominal vessels – examination of the abdominal aorta, the abdominal trunk, the splenic artery, the upper and lower mesenteric arteries and renal arteries.
- Peripheral CT-arterio- or CT-phlebography – examination of the arteries and veins of the extremities.
Taking into account the method of administration of the contrast agent , there are:
- Puncture – contrast is injected into the vessel using a conventional puncture needle. The drug spreads through the vascular bed and gradually enters the study area.
- Catheterization – a catheter is inserted into a large superficially located vessel, it is promoted to the vessels located in the study area, and then contrast is injected directly into the area of the studied vascular network.
Depending on the size of the area under study, there are:
- General – a contrast agent is injected through a catheter into the thoracic or abdominal aorta.
- Selective – contrast preparation is injected punctually or by catheterization into large vessels of the study area.
- Superselective – the contrast agent is brought directly to the small vessels of the study area using a catheter.
CT angiography is usually used at the final stage of diagnosis. The aim of the study is to study individual vessels and vascular networks, to assess blood and lymph flow in various anatomical zones. The procedure is prescribed if necessary to clarify the diagnosis or to conduct a differential diagnosis. In addition, CT angiography is used in the process of preoperative preparation (when planning the type and scope of surgery), as well as in the postoperative period (to assess the effectiveness of surgical treatment).
Cerebral angiography (CT angiography of the brain) is prescribed to assess the condition of blood vessels, detect developmental abnormalities, aneurysms, blood supply disorders in traumatic injuries, detect areas of occlusion and stenosis in various diseases. Indications for vascular CT are headaches, dizziness, nausea, vomiting, convulsions, focal disorders of sensitivity and movement, hemiplegia, hemiparesis, as well as hearing and vision disorders of presumably neurological nature.
Angiocardiography (CT-coronarography) is used to detect anomalies of development, narrowing and occlusion of coronary vessels, as well as to assess the patency of stents and shunts. Indications are heart pain, ineffectiveness of angina treatment, postinfarction angina, high risk of complications in the treatment of coronary artery disease, the period of preparation for open heart surgery in patients older than 35 years, conditions after stenting or bypass of coronary arteries.
CT angiography of the abdominal cavity is prescribed to detect developmental abnormalities, aneurysms, injuries, thrombosis, atherosclerotic vascular lesions, abdominal aortic dissection, as well as oncological processes. Indications for carrying out are injuries and pathological changes in the vessels of the abdominal cavity as a result of injuries and diseases. In addition, the procedure is carried out during the preparation for angiosurgical operations and after surgical interventions on the vessels of the abdominal cavity.
CT angiography of the extremities is used to detect developmental abnormalities, pathological processes and post-traumatic circulatory disorders in the peripheral arteries and veins. Indications are phlebitis, chronic venous insufficiency, obliterating endarteritis, atherosclerosis, thrombosis of the arteries of the upper and lower extremities, delaminating aneurysm, developmental abnormalities and diabetic foot syndrome. CT of vessels is also performed at the stage of preoperative preparation and after operations on the vessels of the extremities.
CT angiography is not performed during gestation and in childhood (except in cases when the procedure is necessary for vital reasons). The list of contraindications also includes allergy to iodine-containing drugs, taking medications incompatible with iodine-containing drugs, severe general condition of the patient, thyroid diseases, decompensated diabetes mellitus, renal failure, acute heart failure and some diseases of the hematopoiesis system.
Vascular CT is not prescribed for mental disorders accompanied by motor arousal, disorders of intelligence, consciousness and perception that prevent the implementation of doctor’s instructions. In addition, there are restrictions on body weight due to the technical capabilities of the equipment. Most tables are designed for a weight of no more than 120-130 kg. The lactation period is considered as a relative contraindication. The contrast agent is excreted from the body within 2 days, therefore, nursing patients are advised to express milk in advance and refrain from feeding during the specified period.
Methodology of conducting
Within 4-6 hours before the start of diagnosis, the patient is recommended to refrain from eating. If the contrast agent is administered in the axillary or inguinal area, it is necessary to shave the specified area. Before CT angiography, the patient is asked to remove metal objects, placed on a special table and an allergic test is carried out by subcutaneous injection of 0.1 ml of contrast agent. Sedatives can be used to normalize the psychological state. Local anesthesia is usually not required.
The place and method of administration (through a catheter, puncture) are chosen taking into account the studied area. With a portion administration, a dropper is installed. Usually, the contrast agent is injected using a special automatic injector. Before using the injector, the specialist injects a small amount of the drug manually to make sure that the catheter is installed correctly. When the contrast enters the body, the patient may feel cold, warm or a metallic taste in the mouth. These are normal reactions that are not grounds for stopping CT angiography. Nausea, palpitations, itching of the skin and difficulty breathing may indicate intolerance to the drug, such symptoms should be immediately reported to the doctor.
At the end of the CT scan of the vessels, the specialist removes the needle or catheter and puts a pressure bandage on the puncture area. The patient is recommended to drink more fluids to speed up the removal of contrast agent from the body. The doctor examines the data obtained during CT angiography, draws up a conclusion, and then transmits it to the attending physician or patient. Preparation of documents usually takes several hours, with a heavy workload of a specialist, the results of the study may become known the next day.