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Nuklearmedizin 2007; 46(01): 38-42
DOI: 10.1055/s-0037-1616624
Original Article
Schattauer GmbH

Effect of CT-based attenuation correction on uptake ratios in skeletal SPECT

Effekt der CT-basierten Schwächungskorrektur auf den Uptake im Skelett-SPECT
V. Schulz
1   Clinic of Nuclear Medicine, Hoffman Estates, USA
,
I. Nickel
1   Clinic of Nuclear Medicine, Hoffman Estates, USA
,
A. Nömayr
1   Clinic of Nuclear Medicine, Hoffman Estates, USA
,
A. H. Vija
2   Siemens Medical Solutions, Molecular Imaging, SPECT Research, Hoffman Estates, USA
,
C. Hocke
1   Clinic of Nuclear Medicine, Hoffman Estates, USA
,
J. Hornegger
3   Chair of Pattern Recognition
,
W. Bautz
4   Institute of Diagnostic Radiology, University of Erlangen/ Nürnberg, Erlangen, Germany
,
W. Römer
1   Clinic of Nuclear Medicine, Hoffman Estates, USA
,
T. Kuwert
1   Clinic of Nuclear Medicine, Hoffman Estates, USA
› Author Affiliations
Further Information

Publication History

Received: 17 August 2006

accepted in revised form: 17 October 2006

Publication Date:
08 January 2018 (online)

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Summary

The aim of this study was to determine the clinical relevance of compensating SPECT data for patient specific attenuation by the use of CT data simultaneously acquired with SPECT/CT when analyzing the skeletal uptake of polyphosphonates (DPD). Furthermore, the influence of misregistration between SPECT and CT data on uptake ratios was investigated. Methods: Thirty-six data sets from bone SPECTs performed on a hybrid SPECT/CT system were retrospectively analyzed. Using regions of interest (ROIs), raw counts were determined in the fifth lumbar vertebral body, its facet joints, both anterior iliacal spinae, and of the whole transversal slice. ROI measurements were performed in uncorrected (NAC) and attenuation-corrected (AC) images. Furthermore, the ROI measurements were also performed in AC scans in which SPECT and CT images had been misaligned by 1 cm in one dimension beforehand (ACX, ACY, ACZ). Results: After AC, DPD uptake ratios differed significantly from the NAC values in all regions studied ranging from 32% for the left facet joint to 39% for the vertebral body. AC using misaligned pairs of patient data sets led to a significant change of whole-slice uptake ratios whose differences ranged from 3,5 to 25%. For ACX, the average left-to-right ratio of the facet joints was by 8% and for the superior iliacal spines by 31% lower than the values determined for the matched images (p <0.05). Conclusions: AC significantly affects DPD uptake ratios. Furthermore, misalignment between SPECT and CT may introduce significant errors in quantification, potentially also affecting leftto- right ratios. Therefore, at clinical evaluation of attenuation- corrected scans special attention should be given to possible misalignments between SPECT and CT.

Zusammenfassung

Ziel dieser Studie war es, die klinische Relevanz der Schwächungskorrektur von SPECT-Daten im Rahmen der Skelettszintigraphie herauszufinden. Für die Schwächungskorrektur wurden mittels SPECT/CT gewonnene CTDaten verwendet. Zusätzlich wurde der Einfluss einer Verschiebung zwischen SPECT- und CT-Datensatz auf die DPDUptake- Verhältnisse untersucht. Methoden: Die Datensätze von 36 DPD-SPECTs wurden analysiert, die an einem SPECT/CT-Hybridsystem erhoben worden waren. Unter Verwendung von ROIs (regions of interest) wurden die Zählraten im fünften Lendenwirbelkörper, dessen Facettengelenken, den beiden Spinae iliacae ant. sup. und der gesamten transversalen Schicht bestimmt. Für die Messungen wurden die unkorrigierten (NAC) und schwächungskorrigierten (AC) Bilder verwendet. Außerdem erfolgten ROI-Messungen an schwächungskorrigierten Datensätzen, bei denen vor der Schwächungskorrektur die SPECT- und CT-Daten manuell um 1 cm gegeneinander in einer Dimension verschoben worden waren (ACX, ACY, ACZ). Ergebnisse: Die schwächungskorrigierten Uptake-Verhältnisse von DPD unterschieden sich in allen ausgewerteten Regionen signifikant von den unkorrigierten Werten. Die prozentuale Abweichung reichte von 32% im linken Facettengelenk bis 39% im Wirbelkörper. Eine Schwächungskorrektur, die mit verschobenen Datenpaaren durchgeführt wurde, führte zu einer signifikanten änderung der Uptake-Verhältnisse der gesamten Schicht im Bereich von 3,5-25%. Für ACX war der durchschnittliche Links/Rechts-Quotient der Facettengelenke um 8% und der der Spinae iliacae ant. sup. um 31% niedriger als die Werte, die für optimal registrierte Datensätze gemessen wurden (p <0,05). Schlussfolgerung: Die Schwächungskorrektur beeinflusst DPD-Uptake- Verhältnisse in signifikanter Weise. Außerdem kann eine Verschiebung zwischen SPECT und CT signifikante Fehler in der Quantifizierung bewirken und potenziell die Links/ Rechts-Quotienten verändern. Bei der klinischen Auswertung von schwächungskorrigierten Daten sollte deshalb speziell auf mögliche Verschiebungen zwischen SPECT und CT geachtet werden.

Keywords

SPECT/ CT - image fusion - hybrid imaging - attenuation correction - bone scintigraphy

Schlüsselwörter

SPECT/CT - Bildfusion - Hybridbildgebung - Schwächungskorrektur - Knochenszintigraphie
 

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