Gated metabolic myocardial imaging, a surrogate for dual perfusion-metabolism imaging by positron emission tomography.

OBJECTIVE: Perfusion-metabolism mismatch pattern on positron emission tomography (PET) predicts hibernating myocardium. We assess the ECG-gated metabolic PET as a surrogate for the perfusion-metabolism mismatch pattern on PET imaging. METHODS: 13N-Ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) are respectively perfusion and metabolism PET tracers. We used ECG gating to acquire FDG-PET to collect wall thickening (mechanical) data. These allow detection of metabolic activity in regions with reduced contraction (metabolism-mechanical mismatch pattern). We had two data sets on each patient: perfusion-metabolism and metabolism-mechanical data sets. We tested the hypothesis that metabolism-mechanical pattern on PET could predict perfusion-metabolism mismatch pattern. RESULTS: We studied 55 patients (48 males), mean age 62 years. All were in sinus rhythm, and had impaired left ventricular contraction. Perfusion-metabolism mismatch pattern was found in 26 patients. Metabolism-mechanical mismatch pattern was found in 25 patients. The results were concordant in 52 patients (95%). As a surrogate for perfusion-metabolism mismatch pattern, demonstration of metabolism-mechanical mismatch pattern is highly sensitive (92%) and specific (97%). In this cohort, the positive and negative predictive accuracy of the new method are 96% and 93%, respectively. CONCLUSION: Metabolism-mechanical mismatch pattern could predict perfusion-metabolism mismatch pattern in patients with myocardial viability criteria on PET. Prospective validation against the gold standard of improved myocardial contraction after revascularisation is needed.

Characterization of viability, scarring and hibernation of the myocardium supplied by epicardial coronary arteries with low flow grades.

OBJECTIVE: The aim of this study was to analyse the relationship between reduced coronary artery flow and myocardial viability, scarring and hibernation. PATIENTS AND METHODS: Coronary flow grades and collateral vessels were scored using the thrombolysis in myocardial infarction trial (TIMI) and the Rentrop and Cohen scoring systems, respectively. N-ammonia and fluorine-18-fluorodeoxyglucose (F-FDG) are the perfusion and metabolic markers on PET, respectively. The left ventricle was divided into three coronary territories. The area with the highest N-ammonia uptake was considered the reference region. Myocardial regions with F-FDG uptake of at least 50% of the reference region were considered viable and those with F-FDG uptake less than 50% of the reference region were considered scarred. Hibernation was considered present if the viable myocardium had significant wall motion abnormality. RESULTS: There were 80 (71 males) patients with 240 myocardial territories. TIMI 2-3 arteries supplied 151 regions (group A), and 89 regions were supplied by TIMI 0-1 arteries (group B). Viable myocardium was present in 140 (93%) regions of group A and in 76 (85%) regions of group B (P=0.068). Scarring was present in 40 (26%) regions in group A and in 49 (55%) regions in group B (P<0.0001). Wall motion data were available in 215 regions: 133 regions in group A and 82 regions in group B. Hibernating myocardium was predicted in 36 (28%) regions in group A and in 34 (41%) regions in group B (P<0.05). CONCLUSION: Myocardial regions supplied by arteries with TIMI 0-1 are characterized by significantly increased incidence of hibernation and scarring. Video abstract: http://links.lww.com/NMC/A115.

An enzymatic route to 5-deoxy-5-[18F]fluoro-D-ribose, a [18F]-fluorinated sugar for PET imaging.

An efficient two-step, one-pot, biotransformation involving the fluorinase enzyme is described for the synthesis of 5-deoxy-5-[(18)F]fluororibose, a novel [(18)F]-fluorinated sugar suitable for positron emission tomography (PET) applications.

The relationship between vascular and metabolic characteristics of primary breast tumours.

The objective of this study was to investigate the relationship between vascular and metabolic characteristics of breast tumours in vivo, using contrast-enhanced dynamic MRI and 2-[(18)F] fluoro-2-deoxy- d-glucose (FDG) PET imaging. Twenty patients with large or locally advanced primary breast cancers were imaged prior to therapy. MRI data were acquired using a dynamic gradient echo sequence and analysed using two pharmacokinetic models. Static PET data were acquired in 2D mode. A significant association ( P<0.05) was observed between the calculated exchange rate constants of both pharmacokinetic models and calculated PET FDG dose uptake ratios (DUR). Statistical analysis showed that the exchange rate constants can explain between 27 and 44% of the variance observed in the PET FDG uptake ratios. A relationship was demonstrated between the vascular and metabolic characteristics of primary breast tumours showing that any assessment of tumour metabolic activity using PET may be controlled at least in part by delivery of uptake agent due to the vascular characteristics of the tumour. MRI and PET provide methods of assessing breast tumour vascularity and metabolism in vivo using the exchange rate constants of dynamic MRI, and DUR of PET, respectively, these measures being related but not equivalent.