Accuracy of myocardial viability imaging by cardiac MRI and PET depending on left ventricular function

AIM To compare myocardial viability assessment accuracy of cardiac magnetic resonance imaging(CMR)compared to[^(18)F]-fluorodeoxyglucose(FDG)-positron emission tomography(PET)depending on left ventricular(LV)function.METHODS One-hundred-five patients with known obstructive coronary artery disease(CAD)and anticipated coronary revascularization were included in the study and examined by CMR on a 1.5T scanner.The CMR protocol consisted of cine-sequences for function analysis and late gadolinium enhancement(LGE)imaging for viability assessment in 8 mm long and contiguous short axis slices.All patients underwent PET using[^(18)F]-FDG.Myocardial scars were rated in both CMR and PET on a segmental basis by a 4-point-scale:Score 1=no LGE,normal FDG-uptake;score 2=LGE enhancement<50% of wall thickness,reduced FDG-uptake(≥50% of maximum);score 3=LGE≥50% ,reduced FDG-uptake(<50% of maximum);score 4=transmural LGE,no FDG-uptake.Segments with score 1 and 2 were categorized"viable",scores 3 and 4 were categorized as"non-viable".Patients were divided into three groups based on LV function as determined by CMR:Ejection fraction(EF),<30% :n=45;EF:30% -50% :n=44;EF>50% :n=16).On a segmental basis,the accuracy of CMR in detecting myocardial scar was compared to PET in the total collective and in the three different patient groups.RESULTS CMR and PET data of all 105 patients were sufficient for evaluation and 5508 segments were compared in total.In all patients,CMR detected significantly more scars(score 2-4)than PET:45% vs 40% of all segments(P<0.0001).In the different LV function groups,CMR found more scar segments than PET in subjects with EF<30% (55% vs 46% ;P<0.0001)and EF 30% -50% (44% vs 40% ;P<0.005).However,CMR revealed less scars than PET in patients with EF>50% (15% vs 23% ;P<0.0001).In terms of functional improvement estimation,i.e.,expected improvement after revascularization,CMR identified"viable"segments(score 1 and 2)in 72% of segments across all groups,PET in 80% (P<0.0001).Also in all LV function subgroups,CMR judged less segments viable than PET:EF<30% ,66% vs 75% ;EF=30% -50% ,72% vs 80% ;EF>50% ,91% vs 94% .CONCLUSION CMR and PET reveal different diagnostic accuracy in myocardial viability assessment depending on LV function state.CMR,in general,is less optimistic in functional recovery prediction.

Significance of an additional unenhanced scan in computed tomography angiography of patients with suspected acute aortic syndrome

AIM To assess potential benefits of an additional unenhanced acquisition in computed tomography angiography(CTA) in patients with suspected acute aortic syndrome(AAS).METHODS A total of 103 aortic CTA(non-electrocardiography-gated, 128 slices) performed due to suspected AAS were retrospectively evaluated for acute aortic dissection(AAD), intramural hematoma(IMH), or penetrating aortic ulcer(PAU). Spiral CTA protocol consisted of an unenhanced acquisition and an arterial phase. If AAS was detected, a venous phase(delay, 90 s) was added. Images were evaluated for the presence and extent of AAD, IMH, PAU, and related complications. The diagnostic benefit of the unenhanced acquisition was evaluated concerning detection of IMH.RESULTS Fifty-six(30% women; mean age, 67 years; median, 68 years) of the screened individuals had AAD or IMH. A triphasic CT scan was conducted in 76.8%(n =43). 56% of the detected AAD were classified as Stanford type A, 44% as Stanford type B. 53.8% of the detected IMH were classified as Stanford type A, 46.2% as Stanford type B. There was no significant difference in the involvement of the ascending aorta between AAD and IMH(P = 1.0) or in the average age between AAD and IMH(P = 0.548), between Stanford type A and Stanford type B in general(P = 0.650) and between Stanford type A and Stanford type B within the entities of AAD and IMH(AAD: P = 0.785; IMH: P = 0.146). Only the unenhanced acquisitions showed a significant density difference between the adjacent lumen and the IMH(P = 0.035). Subadventitial hematoma involving the pulmonary trunk was present in 5 patients(16%) with Stanford A AAD. The difference between the median radiation exposure of a triphasic(2737 mGy*cm) compared to a biphasic CT scan(2135 mGy*cm) was not significant(P = 0.135).CONCLUSION IMH is a common and difficult to detect entity of AAS. An additional unenhanced acquisition within an aortic CTA protocol facilitates the detection of IMH.