Table 1.

A summary of the imaging approaches for diagnosis of CAS.

Imaging approaches	Advantages	Disadvantages	References
Coronary angiography (CAG)	Gold standard when performed under provocation testing	Confusion between CAD and CAS	[2, 116, 117, 118]
		Omission in conditions of severe stenosis
Electrocardiogram (ECG)	Convenience, safety, availability, acceptability	Low specificity	[119, 120, 121, 122, 123]
		Omission in resting intervals
Intracoronary imaging approaches	Exhibition of morphological and functional changes despite complex conditions	In theoretical stage	[117, 119, 124, 125, 126, 127, 128]
		High requirements for equipment and operators
OCT	Better image quality and resolution to estimate intima	Interruption of the blood flow	[126, 128]
		Tissue penetration: 2 mm
		Safety worries
IVUS	Deeper penetration (4–8 mm) for accessing perivascular injury without interrupting the blood flow	Less resolution	[126, 129]
Positron emission tomography (PET)	Revelation of coronary vasomotor function and tissue image	Expensive	[109, 130]
		High requirements for equipment
${\mathrm{18}}^F$-PET	Evaluation of inflammation of coronary perivascular adipose tissue	Expensive	[109]
		High requirements for equipment
Myocardial contrast echocardiography (MCE)	Microvascular evaluation	Indirect functional information	[131, 132, 133]
		Ignorance of minor systolic wall move
		Low resolution

OCT, optical coherence tomography; IVUS, intravascular ultrasound.