Considerable progress has also been made in reducing the radiation dose. Thus, with state-of-the-art equipment, the coronaries can be imaged with a dose of less than 1 mSv.
Dynamic CT angiographies of the heart, as required to assess the success of interventional closure of the left atrial appendage, or CT examinations after interventional repair of the mitral valve are also now successful with a very low radiation dose.
In the past year, clinical research has focused on so-called “kidney-friendly” CT angiography, in which only small amounts of iodine-containing contrast media are used. Here, the specific attenuation behavior of iodine as a function of the energy of the X-ray radiation is exploited.
For example, today only about 20 ml of contrast medium is applied for CT pulmonary angiography to diagnose pulmonary embolism, and ECG-triggered CT angiography of the aorta for planning TAVI (Transcatheter Aortic Valve Implantation) or endovascular intervention is now performed with only 30 ml of contrast medium.
Because of the frequency of renal insufficiency in patients qualifying for TAVI and endoaortic procedures, this reduction in the amount of contrast agent is a great advantage.
Pre-interventional accurate visualization of the anatomy is essential for planning TAVI interventions. CT can be used to measure the aortic annulus as well as the distance between the coronary ostia and the annulus plane with high accuracy, which is crucial for the selection of the correct prosthesis size. In addition, CT allows accurate visualization and quantification of the diameter of the iliac vessels for planning access (femoral vs. transapical).