Computed Tomography of the Coronary Arteries

Non-invasive coronary computed tomography angiography (CCTA) has become an important tool for visualisation of coronary arteries since the introduction of 64-channel detector CCTA in 2004. It has been proved to be especially beneficial for ruling out coronary artery disease (CAD) in selected patient populations, due to the high negative predictive value (NPV). The aim of this thesis was to study some aspects of the introduction, establishment and development of a new method, retrospectively ECG-gated CCTA with 64-channel detector, to evaluate coronary arteries. In study I the diagnostic capacity and limitation of CCTA was compared to that of invasive coronary angiography (ICA) in a newly established CCTA team. CCTA had a very high NPV but the number of non-diagnostic scans was also high. The main limitations were motion artifacts and vessel calcifications, while short experience in reading CCTA did not affect image interpretation. Study II described the learning-curve effect of the interpretation of 100 CCTA and also compared the diagnostic accuracy of both radiologists and radiographers, after a common introduction. The review time for novices was approximately halved during the first 100 cases, with maintained diagnostic accuracy. There was a learning-curve effect in positive predictive value (PPV) for radiologists, but not for the radiographers. However, the diagnostic accuracy of dedicated radiographers indicated that they might be considered as part of the evaluation team. Study III compared the radiation exposure in retrospectively ECG-gated CCTA and ICA in the same population. Both mean estimated effective dose (ED) and organ doses (skin, breast, lung and oesophagus) were higher in CCTA when compared to ICA. The relatively high radiation dose to breast indicates that bismuth shielding should be used in women when performing CCTA. When using the updated tissue weighting factors provided in ICRP 103 the calculated ED from CCTA were significantly higher than those obtained using outdated ICRP 60. In study IV the image quality and radiation doses were compared when decreasing X-ray tube peak kilovoltage (kVp) from 120 to 100 kVp in patients undergoing CCTA. By reduction of tube voltage the radiation dose was almost halved while the diagnostic image quality was kept at a clinically acceptable level. In conclusion, CCTA is increasingly available throughout the world as an alternative to gold standard ICA, especially due to the excellent capability to rule out CAD. Still, retrospectively ECG-gated 64-channel detector CCTA has limitations such as motion artifacts and vessel calcifications. Another limitation is the high radiation doses required for CCTA compared to ICA. By lowering the kVp from traditionally 120 kVp to 100 kVp the radiation dose is halved while retaining diagnostic accuracy. There is a learning curve effect (regarded PPV and review time) of the interpretation of CCTA. However, more than 100 reviewed CCTA cases are necessary to reach a diagnostic accuracy that is acceptable

Application of Dual-Energy Computed Tomography to the Evalution of Coronary Atherosclerotic Plaque

Atherosclerotic coronary artery disease is responsible for around 50 of cardiovascular deaths in USA. Early detection and characterization of coronary artery atherosclerotic plaque could help prevent cardiac events. Computed tomography (CT) is an excellent modality for imaging calcifications and has higher spatial resolution than other common non-invasive modalities (e.g MRI), making it more suitable for coronary plaque detection. However, attenuation-based classification of non-calcified plaques as fibrous or lipid is difficult with conventional CT, which relies on a single x-ray energy. Dual-energy CT (DECT) may provide additional attenuation data for the identification and discrimination of plaque components. The purpose of this research was to evaluate the feasibility of DECT imaging for coronary plaque characterization and further, to explore the limits of CT for non-invasive plaque analysis. DECT techniques were applied to plaque classification using a clinical CT system. Saline perfused coronary arteries from autopsies were scanned at 80 and 140 kVp, prior to and during injection of iodinated contrast. Plaque attenuation was measured from CT images and matched to histology. Measurements were compared to assess differences among plaque types. Although calcified and non-calcified plaques could be identified and differentiated with DECT, further characterization of non-calcified plaques was not possible. The results also demonstrated that calcified plaque and iodine could be discriminated. The limits of x-ray based non-calcified plaque discrimination were assessed using microCT, a pre-clinical x-ray based high spatial resolution modality. Phantoms and tissues of different composition were scanned using different tube voltages (i.e., different energies) and resulting attenuation values were compared. Better vessel wall visualization and increase in tissue contrast resolution was observed with decrease in x-ray energy. Feasibility of calcium quantification from contrast-enhanced scans by creating virtual n

Application of Dual-Energy Computed Tomography to the Evalution of Coronary Atherosclerotic Plaque

Atherosclerotic coronary artery disease is responsible for around 50 of cardiovascular deaths in USA. Early detection and characterization of coronary artery atherosclerotic plaque could help prevent cardiac events. Computed tomography (CT) is an excellent modality for imaging calcifications and has higher spatial resolution than other common non-invasive modalities (e.g MRI), making it more suitable for coronary plaque detection. However, attenuation-based classification of non-calcified plaques as fibrous or lipid is difficult with conventional CT, which relies on a single x-ray energy. Dual-energy CT (DECT) may provide additional attenuation data for the identification and discrimination of plaque components. The purpose of this research was to evaluate the feasibility of DECT imaging for coronary plaque characterization and further, to explore the limits of CT for non-invasive plaque analysis. DECT techniques were applied to plaque classification using a clinical CT system. Saline perfused coronary arteries from autopsies were scanned at 80 and 140 kVp, prior to and during injection of iodinated contrast. Plaque attenuation was measured from CT images and matched to histology. Measurements were compared to assess differences among plaque types. Although calcified and non-calcified plaques could be identified and differentiated with DECT, further characterization of non-calcified plaques was not possible. The results also demonstrated that calcified plaque and iodine could be discriminated. The limits of x-ray based non-calcified plaque discrimination were assessed using microCT, a pre-clinical x-ray based high spatial resolution modality. Phantoms and tissues of different composition were scanned using different tube voltages (i.e., different energies) and resulting attenuation values were compared. Better vessel wall visualization and increase in tissue contrast resolution was observed with decrease in x-ray energy. Feasibility of calcium quantification from contrast-enhanced scans by creating virtual n

Clinical applications of cardiac CT angiography

ECG-gated multislice CT provides a cost-effective, non-invasive technology for evaluation of the coronary arteries, as well as for additional clinical applications, which require morphological assessment of the heart and adjacent structures with simultaneous evaluation of the coronary circulation

Coronary spiral CT

This dissertation describes the use and clinical potential of ECG gated multislice spiral computed tomography in patients with coronary artery disease. First the use of other non invasive cardiac imaging, i.e. the previously mentioned electron beam CT and magnetic resonance imaging is reviewed (chapter 2.1). Part 3 contains studies related to the characteristics of multislice spiral CT for the imaging of the heart and coronary arteries, and the diagnostic potential of ECG gated spiral CT coronary angiography to detect and visualize obstructive coronary artery disease in symptomatic patients, using conventional coronary angiography as the standard of reference. Part 4 is focussed on the feasibility and characteristics of coronary wall imaging by CT, including the assessment of non calcified atherosclerotic plaque material. The usefulness of contrast enhanced multislice spiral CT in symptomatic patients who previously underwent coronary artery bypass grafting and percutaneous coronary intervention with stent implantation is discussed in part 5. Finally, the first results with the latest generation 16 slice computed tomography scanners and patient preparation with ~ receptor blockers are described in part 6, including a review and future outlook on the continuing development and clinical use of non invasive coronary angiography with spiral computed tomography

Strategies for radiation dose reduction in nuclear cardiology and cardiac computed tomography imaging: a report from the European Association of Cardiovascular Imaging (EACVI), the Cardiovascular Committee of European Association of Nuclear Medicine (EANM), and the European Society of Cardiovascular Radiology (ESCR).

Cardiolog

Multislice computed tomography coronary angiography

__Abstract__ Computed Tomography (CT) imaging is also known as "CAT scanning" (Computed Axia