Changes of Time-Attenuation Curve Blood Flow Parameters in Patients with and without Carotid Stenosis

BACKGROUND AND PURPOSE:From the time-attenuation curves of DSA flow parameters, maximal intensity, maximal slope, and full width at half maximum of selected vascular points are defined. The study explores the reliability of defining the flow parameters by the time-attenuation curves of DSA.MATERIALS AND METHODS:Seventy patients with unilateral carotid artery stenosis (group A) and 56 healthy controls (group B) were retrospectively enrolled. Fixed contrast injection protocols and DSA acquisition parameters were used with all patients. The M1, sigmoid sinus, and internal jugular vein on anteroposterior view DSA and the M2, parietal vein, and superior sagittal sinus on lateral view DSA were chosen as ROI targets for measuring flow parameters. The difference of time of maximal intensity between 2 target points was defined as the circulation time between the target points.RESULTS:The maximal intensity difference of 2 selected points from the ICA to the M1, sigmoid sinus, internal jugular vein, M2, parietal vein, and superior sagittal sinus was significantly longer in group A than in group B. The maximum slope of M1, M2, and the superior sagittal sinus was significantly lower in group A than in group B. The full width at half maximum of M1 and M2 was significantly larger in group A than in group B. The maximal slope of M1 demonstrated the best diagnostic performance.CONCLUSIONS:The maximal intensity difference of 2 selected points derived from DSA can be used as a definitive alternative flow parameter for intracranial circulation time measurement. Maximal slope and full width at half maximum complement the maximal intensity difference of 2 selected points in defining flow characteristics of healthy subjects and patients with carotid stenosis.

DSA is the standard reference for diagnosing cerebrovascular diseases with its superior temporal and spatial resolution compared with other imaging methods.^1–3 Using different approaches, a number of recent studies have demonstrated the feasibility of quantitative flow parameter measurement by using flat detector DSA.^4–7 Compared with optical flow methods and computer fluid dynamics simulations, flow parameter analysis with the time-attenuation curve (TDC) of DSA images is less demanding in terms of computer power and processing time.^8,9 Clinically, TDCs are used to assess the “real-time” peritherapeutic hemodynamics of various vascular disorders in an angiography suite.^10–12 The TDC represents the dynamic intensity changes of a contrast bolus passing an ROI. It is affected by the bolus characteristics and physiologic and anatomic conditions (eg, arterial stenosis or arteriovenous shunts).^11,13 From the TDC, we may measure the time of maximal intensity (Tmax), maximal slope (MS), and full width at half maximum (FWHM) of any selected vascular point on the DSA image. The time difference to reach maximum intensity (rTmax) of 2 selected vascular points indicates the circulation time between these 2 points. Accordingly, cerebral circulation time is defined as the rTmax between the internal carotid artery and the parietal vein (PV). The PV is closer to the brain parenchyma compared with the transverse sinus or jugular vein and thus better represents the time for blood flow to travel through the brain parenchyma.¹⁴ Circulation time is an objective flow parameter for various vascular disorders (eg, carotid stenosis, carotid cavernous fistula, and peritherapeutic assessment).^10,12,15,16 The aim of the present study was to compare the diagnostic accuracy of rTmax, MS, and FWHM for detecting blood flow property changes by using a large sample of healthy subjects and patients with carotid stenosis.     

MRI-based safety evaluation of the ventrica magnetic coronary anastomotic system

The Ventrica Magnetic Vascular Positioner system is a novel automatic anastomotic coupling device for distal coronary artery anastomosis. There is concern that enormous magnetic fields may negatively affect graft anastomosis or coronary artery blood flow, or that they may lead to disconnection of the magnetic ports. Forty-five domestic swine (26.6 +/- 5.9 kg) underwent magnetic resonance imaging after a single Ventrica anastomosis of the left internal mammary artery to the left anterior descending artery. Group A (n = 15) underwent magnetic resonance imaging immediately after surgery, group B (n = 15) was studied after 1 week, and group C (n = 15) after 2 weeks. The animals were sacrificed and the anastomotic sites were examined. All animals survived the imaging procedure. Mean imaging time was 25 +/- 6 min. Although imaging artifacts occurred in the area surrounding the Ventrica port, there were no disconnections or electrocardiographic signs of ischemia during the study period. Upon sacrifice, all anastomoses were patent without alterations in the alignment of the magnetic components. Clinically relevant tests such as cranial magnetic resonance imaging may be safe after use of the Ventrica system for coronary artery revascularization.