“…However, the relatively high cost associated with PET imaging means that it has limited clinical application because of the requirement for either onsite/nearby cyclotrons or expensive generators [ 1 ]. Other methods that could serve as good diagnostic tools for obstructive and non-obstructive coronary disease visualisation and MBF reserve are adenosine stress magnetic resonance imaging (MRI) with measurement of fractional flow reserve [ 10 ], and transthoracic Doppler echocardiographic CFR measurement with adenosine or dipyridamole in the left anterior descending (LAD) coronary artery flow [ 1 , 11 ]. Further studies are needed to assess whether non-invasive and invasive quantitative assessment of CFR can be applied for monitoring disease progression in these patient populations and to evaluate the clinical impact of early diagnosis and therapy facilitated by non-invasive and invasive coronary flow quantification [ 1 , 12 ].…”