Background: optimal stent selection and placement would be expected to improve clinical outcomes. Coronary computed tomography angiography (CCTA) may permit better preprocedural planning.
Objectives: to assess the impact of incorporating coronary computed tomography angiogaphy guidance in defining reference value for stent length and diameter on angiographic and clinical outcomes in comparison to quantitative coronary angiography and its effect on incidence of instent restenosis. 
Methods: the study was conducted on 153 diabetic patients with stable coronary artery disease. Patients were divided into two groups: group A and group B according to PCI guidance either with quantitative computed tomography angiography (QCTA) datasets or quantitative computed tomography (QCA) datasets respectively. Follow up clinically for six months to assess incidence of major adverse cardiac events (MACE) and angiographically by coronary angiography at six months or before if clinically indicated to assess incidence of instent restenosis (primary end point).
Results: QCTA was associated with longer lesions (p=0.001) and larger reference vessel diameter (p=0.001) than that measured by invasive QCA in group A. No statistical significant difference between group A and group B regarding restenosis rate, minimum lumen diameter at follow up and incidence of MACE.
Conclusions: CCTA guided percutaneous coronary intervention (PCI) is a safe and effective strategy for treatment of coronary artery disease however it didn't add a beneficial role in reducing incidence of instent restenosis or MACE in comparison to angiographic guidance alone.