Positron emission tomography for assessment of viability

The assessment of microvascular flow and tissue perfusion using ultrasound imaging

Imaging microvascular flow is of diagnostic value for a wide range of diseases including cancer, inflammation, and cardiovascular disease. The introduction of microbubbles as ultrasound contrast agents offers significant signal enhancement to the otherwise weakly scattered signal from blood in the circulation. Microbubbles provide maximum impedance mismatch, but are not linear scatterers. Their complex response to ultrasound has generated research on both their behaviour and their scattered-signal processing. Nearly 20 years ago signal processing started with simple spectral filtering of harmonics showing contrast-enhanced images. More recent pulse encoding techniques have achieved good cancellation of tissue echoes. The good quality contrast-only images enabled ultrasound contrast-imaging applications to be established in microvascular measurements in the liver and the myocardium. The field promises to advance the quantification of microvascular flow kinetics.

Impact of preoperative positron emission tomography in patients with severely impaired LV-function undergoing surgical revascularization

In patients with ischemic cardiomyopathy, coronary artery bypass grafting (CABG) offers an important therapeutic option but is still associated with high perioperative mortality. Although previous studies suggest a benefit from revascularization for patients with defined viability by a non-invasive technique, the role of viability assessment to determine suitability for revascularization in patients with ischemic cardiomyopathy has not yet been defined. This study evaluates the hypothesis that the use of PET imaging in the decision-making process for CABG will improve postoperative patient survival. We reviewed 476 patients with ischemic cardiomyopathy (LV ejection fraction ≤0.35) who were considered candidates for CABG between 1994 and 2004 on the basis of clinical presentation and angiographic data. In a Standard Care Group, 298 patients underwent CABG. In a second PET-assisted management group of 178 patients, 152 patients underwent CABG (PET-CABG) and 26 patients were excluded from CABG because of lack of viability (PET-Alternatives). Primary endpoint was postoperative survival. There were two in hospital deaths in the PET-CABG (1.3%) and 30 (10.1%) in the Standard Care Group (P = 0.018). The survival rate after 1, 5 and 9.3 years was 92.0, 73.3 and 54.2% in the PET-CABG and 88.9, 62.2 and 35.5% in the Standard Care Group, respectively (P = 0.005). Cox-regression analysis revealed a significant influence on long-term survival of patient selection by viability assessment via PET (P = 0.008), of LV-function (P = 0.017), and age >70 (P = 0.016). Preoperative assessment of myocardial viability via PET identifies patients, who will benefit most from CABG.