Computed tomography myocardial perfusion vs (15)O-water positron emission tomography and fractional flow reserve

Objectives: Computed tomography (CT) can perform comprehensive cardiac imaging. We compared CT coronary angiography (CTCA) and CT myocardial perfusion (CTP) with ¹⁵O-water positron emission tomography (PET) and invasive coronary angiography (ICA) with fractional flow reserve (FFR). Methods: 51 patients (63 (61–65) years, 80 % male) with known/suspected coronary artery disease (CAD) underwent 320-multidetector CTCA followed by “snapshot” adenosine stress CTP. Of these 22 underwent PET and 47 ICA/FFR. Obstructive CAD was defined as CTCA stenosis >50 % and CTP hypoperfusion, ICA stenosis >70 % or FFR <0.80. Results: PET hyperaemic myocardial blood flow (MBF) was lower in obstructive than non-obstructive territories defined by ICA/FFR (1.76 (1.32–2.20) vs 3.11 (2.44–3.79) mL/(g/min), P < 0.001) and CTCA/CTP (1.76 (1.32–2.20) vs 3.12 (2.44–3.79) mL/(g/min), P < 0.001). Baseline and hyperaemic CT attenuation density was lower in obstructive than non-obstructive territories (73 (71–76) vs 86 (84–88) HU, P < 0.001 and 101 (96–106) vs 111 (107–114) HU, P 0.001). PET hyperaemic MBF corrected for rate pressure product correlated with CT attenuation density (r = 0.579, P < 0.001). There was excellent per-patient sensitivity (96 %), specificity (85 %), negative predictive value (90 %) and positive predictive value (94 %) for CTCA/CTP vs ICA/FFR. Conclusion: CT myocardial attenuation density correlates with ¹⁵O-water PET MBF. CTCA and CTP can accurately identify obstructive CAD. Key Points: •CT myocardial perfusion can aid the assessment of suspected coronary artery disease. • CT attenuation density from “snapshot” imaging is a marker of myocardial perfusion. • CT myocardial attenuation density correlates with ¹⁵O-water PET myocardial blood flow. • CT attenuation density is lower in obstructive territories defined by invasive angiography. • Diagnostic accuracy of CTCA+CTP is comparable to invasive angiography + fractional flow reserve

Industry Specialization, Diversity and the Efficiency of Regional Innovation Systems

Innovation processes are characterized by a pronounced division of labor between actors. Two types of externality may arise from such interactions. On the one hand, a close location of actors affiliated to the same industry may stimulate innovation (MAR externalities). On the other hand, new ideas may be born by the exchange of heterogeneous and complementary knowledge between actors, which belong to different industries (Jacobs externalities). We test the impact of both MAR as well as Jacobs externalities on innovative performance at the regional level. The results suggest an inverted u-shaped relationship between regional specialization in certain industries and innovative performance. Further key determinants of the regional innovative performance are private sector R&D and university-industry collaboration