Attenuation correction for myocardial perfusion imaging

S. Graf; A. Khorsand; G. Stix; S. Nekolla; A. Becherer; K. Kletter; R. Dudczak; H. Sochor; G. Maurer; G. Porenta

doi:10.1055/s-0038-1625112

Nuklearmedizin - NuclearMedicine, Table of Contents

Nuklearmedizin 2006; 45(04): 171-176
DOI: 10.1055/s-0038-1625112

Original Articles

Schattauer GmbH

Attenuation correction for myocardial perfusion imaging

A comparison between SPECT and PET imaging by polar map analysisMyokardperfusionsszintigraphie mit Schwächungskorrekturein Vergleich zwischen SPECT und PET mittels Polar-Map-Analyse

S. Graf

¹Department of Cardiology (Head: Gerald Maurer MD)

,

A. Khorsand

¹Department of Cardiology (Head: Gerald Maurer MD)

,

G. Stix

¹Department of Cardiology (Head: Gerald Maurer MD)

,

S. Nekolla

²Technical University of Munich (Head: Markus Schwaiger MD), Germany

,

A. Becherer

³Nuclear Medicine (Head: Robert Dudczak MD), Medical University of Vienna, Austria

,

K. Kletter

³Nuclear Medicine (Head: Robert Dudczak MD), Medical University of Vienna, Austria

,

R. Dudczak

³Nuclear Medicine (Head: Robert Dudczak MD), Medical University of Vienna, Austria

,

H. Sochor

¹Department of Cardiology (Head: Gerald Maurer MD)

,

G. Maurer

¹Department of Cardiology (Head: Gerald Maurer MD)

,

G. Porenta

⁴Department of Nuclear Medicine (Head: Gerold Porenta MD), Rudolfinerhaus, Vienna, Austria

› Author Affiliations

Abstract

Summary

Aim: We investigated the impact of photon attenuation in myocardial perfusion imaging with SPECT and PET in patients with coronary artery disease. In fact, the regional tracer distribution can be quantitatively assessed by polar map analysis if the effects of photon attenuation are accounted for. PET imaging permits accurate measurement of and correction for photon attenuation, whereas results of attenuation correction in SPECT imaging have been inconsistent. Patients, methods: We compared photon attenuation in resting perfusion imaging studies with SPECT (^99mTc-sestamibi) and PET (¹³N-ammonia) from 21 patients. Transaxial images were reconstructed with and without attenuation correction and reoriented into short axis images. Polar map analysis was utilized to generate regional tracer uptake in six anatomical segments. Results: Average segmental photon attenuation calculated as the ratio of counts in corrected and uncorrected images was 7.2 ± 1.4 in SPECT and 14.0 ± 3.1 in PET imaging (p <0.01). This attenuation factor was significantly related to body mass index for both methods (p <0.001). While attenuation correction for SPECT imaging did compensate for attenuation effects in the inferior wall (from –15% to +6% vs. PET), relative tracer uptake in the anterior wall in SPECT images was significantly reduced after attenuation correction (from –2% to –18% vs. PET, p <0.01). Conclusion: Differential effects of attenuation correction for myocardial SPECT perfusion imaging need to be considered when algorithms designed to compensate effects of photon attenuation in SPECT imaging are employed in clinical practice.

Zusammenfassung

Ziel: Wir untersuchten das Ausmaß der Photonenattenuation bei Myokardperfusionsstudien mittels SPECT und PET. Beide Methoden erlauben eine Quantifizierung der regionalen Isotopverteilung mit Hilfe der Polar Map Analyse, sofern die Effekte der Weichteilattenuation berücksichtigt werden. Während PET eine akkurate Messung der Photonenattenuation und demzufolge eine verlässliche Attenuationskorrektur erlaubt, sind die Resultate der Attenuationskorrektur mittels SPECT inkonsistent. Patienten, Methoden: Wir verglichen die Photonenattenuation von SPECT (^99mTc-Sestamibi) und PET (¹³N-Ammonika) Myokardperfusionsstudien in 21 Patienten mit koronarer Herzerkrankung. Transaxiale Bilder wurden mit und ohne Attenuationskorrektur rekonstruiert und in Kurzachsen Schnitte reorientiert. Unter Anwendung der Polar Map Analyse wurde die regionale Isotopverteilung in sechs anatomischen Segmenten untersucht. Ergebnisse: Die durchschnittliche segmentale Photonenattenuation (Verhältnis der Zählrate in korrigierten zu unkorrigierten Bildern) betrug 7.2 ± 1.4 in den SPECT Studien und 14.0 ± 3.1 in den PET Studien (p <0.01). Dieser Attenuationsfaktor korrelierte bei beiden Methoden signifikant mit der Körperoberfläche (p <0.001). Während die Attenuationskorrektur mittels SPECT die Effekte der Attenuation der inferioren Wand kompensierte (von –15% auf +6% im Vergleich zu PET), war die relative Isotopaufnahme nach Attenuationskorrektur in der Vorderwand signifikant herabgesetzt (von –2% auf –18% im Vergleich zu PET, p <0.01). Schlussfolgerung: Die unterschiedlichen Effekte der Attenuationskorrektur bei Myokardperfusionsstudien mittels SPECT müssen beim klinischen Einsatz von Algorithmen zur Kompensation von Attenuationsartefakten berücksichtigt werden.

Keywords

Myocardial perfusion imaging - SPECT - PET - attenuation correction - polar map analysis

Schlüsselwörter

Myokardperfusion - SPECT - PET - Schwächungskorrektur - Polar- Map-Analyse

Full Text

References

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