CT angiography
The CT angiography (computed tomographic angiography, CTA) is an imaging technique in medicine, by means of which blood vessels can be represented in the body. The examination uses modern multi-line computed tomography . With the help of fast computers, the arteries or veins are segmented from the computed tomographic layer images and displayed in freely rotatable 3D representations. Modern so-called volume renderings are often colored (the raw images are always black and white). The vessels that can be represented are z. B. the arteries and veins in the brain, lungs, liver, spleen, kidneys and the vessels in the extremities. Fast scanners can also produce angiographic images of the coronary vessels on the beating heart.
The administration of approx. 80 to 100 ml x - ray contrast medium containing iodine is necessary, as in classical angiography , in order to contrast the blood vessels with the surrounding tissue. In contrast to X-ray angiography, however, the substance does not have to be injected directly into the vessels to be visualized, but only into an arm vein. The recording sequence is started manually or automatically with the first passage of the contrast agent bolus through the vascular region of interest and usually lasts only a few seconds.
CTA examinations are technically simpler and lower risk than X-ray angiography. However, the detail resolution of even the most modern CT scanners is even lower (typical voxel size: 0.5–1 mm³) than that of X-ray films, so that their use, especially on the heart and brain, has not yet become generally accepted. For therapeutic interventions on the investigated vessel ( balloon angioplasty , angioplasty , stenting , aneurysm - coiling ) the conventional angiography is still required.
The radiation exposure is relatively high with a CTA (up to 13 mSv ). Competing alternatives to CTA are duplex sonography and magnetic resonance imaging MR angiography .
Indications
Typical indications for CT angiography are:
- Pulmonary embolism is suspected
- Suspected aneurysm in the head, aorta , or other arteries
- Narrowing of the arteries of the extremities ( arterial occlusive disease )
- Narrowing of the arteries supplying the brain
- Narrowing of the renal arteries ( renal artery stenosis )
Risks
The risks relate primarily to the use of iodinated contrast media :
- allergic reaction
- Worsening of kidney function if you have kidney failure or diabetes mellitus
- thyrotoxic crisis with pre-existing thyroid autonomy
Contraindications
- During pregnancy, the benefits and risks - including those of the use of ionizing radiation - must be carefully weighed against each other
- Renal failure
- Plasmacytoma
- Known allergy to contrast media containing iodine
- Hyperthyroidism
literature
- Mathias Prokop, Michael Galanski (Eds.): Spiral and Multislice Computed Tomography of the Body . Thieme, Stuttgart New York 2003, ISBN 3-13-116481-6 ( limited preview in the Google book search).
- Roland C. Bittner, Khaled Hazim, Klaus Helmig: CT, EBT, MRT and angiography: radiological examination technology for MTAR and doctors . Urban & Fischer, Munich Jena 2003, ISBN 3-437-46000-5 ( limited preview in the Google book search).