An approach for comparative quantification of myocardial blood flow (0-15-H₂O-PET), perfusion (Tc-99m-tetrofosmin-SPECT), and metabolism (F 18-FDG-PET)

Summary

Aim: In the present study a new approach has been developed for comparative quantification of absolute myocardial blood flow (MBF), myocardial perfusion, and myocardial metabolism in short-axis slices. Methods: 42 patients with severe CAD, referred for myocardial viability diagnostics, were studied consecutively with 0-15-H₂O PET (H₂O-PET) (twice), Tc-99m-Tetrofosmin 5PECT (TT-SPECT) and F-18-FDG PET (FDG-PET). All dato sets were reconstructed using attenuation correction and reoriented into short axis slices. Each heart was divided into three representative slices (base, rnidventricular, apex) and 18 ROIs were defined on the FDG PET images and transferred to the corresponding H₂O-PET and TT-SPECT slices. TT-SPECT and FDG-PET data were normalized to the ROI showing maximum perfusion. MBF was calculated for all left-ventricular ROIs using a single-compartment-model fitting the dynamic H₂O-PET studies. Microsphere equivalent MBF (MBF_micr) was calculated by multiplying MBF and tissue-fraction, a parameter which was obtained by fitting the dynamic H₂O-PET studies. To reduce influence of viability only well perfused areas (>70% TT-SPECT) were used for comparative quantification. Results: First and second mean global MBF values were 0.85 ml × min^-1 × g^-1 and 0.84 ml × min^-1 × g¹, respectively, with a repeatability coefficient of 0.30 ml ÷ min^-1 × g^l. After sectorization mean MBF_micr was between 0.58 ml × min¹ ÷ ml"¹ and 0.68 ml × min^-1 × ml"¹ in well perfused areas. Corresponding TT-SPECT values ranged from 83 % to 91 %, and FDG-PET values from 91 % to 103%. All procedures yielded higher values for the lateral than the septal regions. Conclusion: Comparative quantification of MBF, MBF_micr, TT-SPECT perfusion and FDG-PET metabolism can be done with the introduced method in short axis slices. The obtained values agree well with experimentally validated values of MBF and MBF_micr.

Zusammenfassung

Ziel: Entwicklung eines Verfahrens zur vergleichenden Quantifizierung des absoluten myokardialen Blutflusses (MBF) mit der myokardialen Perfusion und dem myokardialen Metabolismus in herzachsengerecht reorientierten Schnittebenen. Methoden: 42 Patienten mit schwerer KHK wurden konsekutiv mit 0-15-H₂O-PET (H₂O-PET) (zweifach), Tc-99m-Tetrofosmin-SPECT (TT-SPECT) und F-18-FDG-PET (FDG-PET) untersucht. Alle Datensätze wurden schwächungskorrigiert rekonstruiert und herzachsengerecht reorientiert. In drei Kurzachsenschnitten des FDG-PET-Datensatzes (apexnah, mittventrikulär, basisnah) wurden 18 ROIs zirkumferent definiert und auf die korrespondierenden H₂O-PET- und TT-SPECT-Datensätze transferiert. Die TT-SPECT- und FDG-PET-Datensätze wurden auf das Perfusionsmaximum normiert, und der MBF an den H₂O-PET-Datensätzen für das linksventrikuläre Myokard nach einem Ein-Kompartiment-Modell quantifiziert. Aus dem MBF und der ebenfalls bei der MBF-Quantifizie-rung gewonnenen Tissue-fraction konnte der mikro-sphärenäquivalente Blutfluss (MBF_micr) bestimmt werden. Für die vergleichende Quantifizierung wurden nur gut perfundierte Areale (>70% TT-SPECT) herangezogen, um die Methoden innerhalb einer »Vitalitätsklasse« vergleichen zu können. Ergebnisse: Der mittlere globale MBF beträgt 0,85 ml × min"¹ × g"¹ in der ersten und 0,84 ml ÷ min^-1 × g^-1 in der zweiten Messung bei einem Repeatability-Koeffizienten von 0,30 ml × min^-1 × g¹. Der MBF_micr in gut perfundierten Arealen ergibt bei einer Sektorisierung der Kurzachsenschnitte Werte von 0,58-0,68 ml × min^-1 × ml¹. Die entsprechenden TT-SPECT-Werte liegen im Bereich von 83-91%, die FDG-PET-Werte im Bereich von 91-103% mit der für alle drei Verfahren gleichen Tendenz zu höheren Werten in der Seitenwand als im Septum. Schlussfolgerung: Das vorgestellte Verfahren ermöglicht eine vergleichende Quantifizierung von MBF, MBF_micr, TT-SPECT-Perfusion und FDG-PET-Metabolismus in herzachsengerecht reorientierten Schnittebenen. Die ermittelten Werte liegen alle im Bereich tierexperimentell validierter Befunde.

Keywords

Absolute myocardial blood flow - 0-15-H₂O-PET - myocardial perfusion - Te-99m-Tetrofosmin-SPECT - myocardial metabolism - F-18-FDG-PET

Schlüsselwörter

Absoluter myokardialer Blutfluss - 0-15-H₂O-PET - Myokardperfusion - Tc-99m-Tetrofosmin-SPECT - Myokardmetabolismus - F-18-FDG-PET

^* Medizinische Klinik I, Universitätsklinikum der RWTH Aachen, Germany (Direktor: Univ.-Prof. Dr. med. P. Hanrath)

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