الفهرس 
Anatomical considerations of the coronary arteriesOnly 14 pages are availabe for public view
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Abstract
Ischaemic heart disease most commonly due to coronary artery disease is still one of the most frequent cause of death in Europe and worldwide.To analyze coronary arteries a systemic approach should be followed. It is recommended that the coronary segments are evaluated in a sequential order from segment 1 to segment 15 following the standard report of the American Heart Association.
The interpretation of coronary arteries include:
1) Assessment of stenosis severity,
2) Vessel wall morphology and composition
3) Total occlusions
4) Bypass graft and stent.
Whilst invasive angiography will remain the clinical gold standard for coronary artery visualization for the foreseeable future, CTCA has an important role in the evaluation of patients with suspected coronary disease. Computed Tomography Coronary Angiography (CTCA) is an emerging tool for the non-invasive assessment of coronary artery disease (CAD). CTCA does have some potential advantages over invasive angiography: the 3D volume acquisition allows an excellent appreciation of anatomy of the coronary vessels and their relationships to other structures as well as providing an opportunity to identify other pathologies that may present with coronary type chest pain.
CT based evaluation for significant coronary artery stenosis has been shown to decrease the number of unnecessary hospital admissions, without reducing the rates of appropriate admissions, by ruling out the absence of acute coronary syndrome.
With the emergence of multislice CT and subsequent technological improvements that have increased the spatial and temporal resolution of resulting imaging, Several meta-analyses of studies on the use of 64-slice CT reported mean sensitivities ranging from 85 to 99% and specificities ranging from 86 to 96%.
Further technical developments of multislice CT scanners, such as the emergence of wide-area detector CT, enabled greater coverage per gantry rotation. Expansion of multislice CT systems from 64- to 128-, 256- and 320-slice systems has allowed for the accurate assessment of stenosis severity and atherosclerotic plaque compositionor even the acquisition of whole-heart coverage in one gantry rotation Moreover, with protocol modification, CTCA can be used to concomitantly assess the thoracic aorta, exclude pulmonary emboli and visualise the lung parenchyma.
Indications of CTCA:
1) Acute chest pain in emergency department(ED)
2) Follow-Up of Percutaneous Coronary Intervention
3) Follow-Up After Bypass Surgery
4) Anomalous origin of the coronary arteries
5) Assessment of ventricular function
6) Coronary artery fistulas
7) Coronary artery aneurysms
8) Coronary artery dissection
9) Compression of the left main coronary artery (LMCA)
10) Deep myocardial bridging
Challenges and artifacts in CT coronary angiography:
Motion related artifacts, which includes:
Respiratory and voluntary motion related artifacts & Heart Rate & Heart Rate Variability Motion related artifacts.
Beam hardening and structure related artifacts.
Artifacts caused by technical errors and limitations.Controlled heart rate and good breath holding help to reduce cardiac and respiratory motion artifacts respectively.
Retrospective ECG gating and proper choice of the reconstruction window significantly improves the examination quality.
Recently, third-generation dual-source 192-slice CT was introduced, which is characterised by another acceleration of table feet to 737 mm/s and a gantry rotation time of 250 ms (compared with 280 ms of second-generation dual-source CT), allowing for ECG-gated CT at a temporal resolution of 66 ms. Based on these technical features, it is expected that CTCA with third-generation dual source 192-slice CT may be feasible at higher heart rates.
Contraindications to CTCA:
1) irregular heartbeats(arrhythmias).
2) contra-indications to iodinated contrast material
including allergy, renal insufficiency and hyperthyroidism.
3) Contraindications to radiation exposure, pregnancy, respiratory impairment, and marked heart failure.