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

V. Schulz; I. Nickel; A. Nömayr; A. H. Vija; C. Hocke; J. Hornegger; W. Bautz; W. Römer; T. Kuwert

doi:10.1055/s-0037-1616624

Nuklearmedizin - NuclearMedicine, Table of Contents

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

Authors

V. Schulz

¹Clinic of Nuclear Medicine, Hoffman Estates, USA
I. Nickel

¹Clinic of Nuclear Medicine, Hoffman Estates, USA
A. Nömayr

¹Clinic of Nuclear Medicine, Hoffman Estates, USA
A. H. Vija

²Siemens Medical Solutions, Molecular Imaging, SPECT Research, Hoffman Estates, USA
C. Hocke

¹Clinic of Nuclear Medicine, Hoffman Estates, USA
J. Hornegger

³Chair of Pattern Recognition
W. Bautz

⁴Institute of Diagnostic Radiology, University of Erlangen/ Nürnberg, Erlangen, Germany
W. Römer

¹Clinic of Nuclear Medicine, Hoffman Estates, USA
T. Kuwert

¹Clinic of Nuclear Medicine, Hoffman Estates, USA

Abstract

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

Full Text

References

References
1 Aizer-Dannon A, Bar-Am A, Ron IG. et al. Fused functional-anatomic images of metastatic cancer of cervix obtained by a combined gamma camera and an X-ray tube hybrid system with an illustrative case and review of the 18F-fluorodeoxyglu- cose literature. Gynecol Oncol 2003; 90: 453-7.
2 Bockisch A, Beyer T, Antoch G. et al. Positron emission tomography/computed tomography-imaging protocols, artifacts, and pitfalls. Mol Imaging Biol 2004; 6: 188-99.
3 Case JA, Licho R, King MA. et al. Bone SPECT of the spine: A comparison of attenuation correction techniques. J Nucl Med 1999; 40: 604-13.
4 Celler A, Dixon KL, Chang Z. et al. Problems created in attenuation-corrected SPECT images by artifacts in attenuation maps: a simulation study. J Nucl Med 2005; 46: 335-43.
5 Cohade C, Osman M, Marshall LN. et al. PET-CT: accuracy of PET and CT spatial registration of lung lesions. Eur J Nucl Med Mol Imaging 2003; 30: 721-6.
6 Dresel S, Schwenzer K, Brinkbaumer K. et al. 18F-FDG imaging ofhead and neck tumors: comparison of hybrid PET, dedicated PET and CT. Nuklearmedizin 2001; 40: 172-8.
7 Even-Sapir E, Keidar Z, Sachs J. et al. The new technology of combined transmission and emission tomography in evaluation of endocrine neoplasms. J Nucl Med 2001; 42: 998-1004.
8 Even-Sapir E. Imaging of malignant bone involvement by morphologic, scintigraphic, and hy- bridmodalities. J Nucl Med 2005; 46: 1356-67.
9 Ficaro EP. Should SPET attenuation correction be more widely employed in routine clinical practice?. Eur J Nucl Med Mol Imaging 2002; 29: 409-12.
10 Förster GJ, Laumann C, Nickel O. et al. SPET/CT image co-registration in the abdomen with a simple and cost-effective tool. Eur J Nucl Med Mol Imaging 2003; 30: 32-9.
11 Fricke E, Fricke H, Weise R. et al. Attenuation correction of myocardial SPECT perfusion images with low-dose CT: Evaluation of the method by comparison with perfusion PET. J Nucl Med 2005; 46: 736-44.
12 Fricke H, Fricke E, Weise R. et al. A method to remove artifacts in attenuation-corrected myoc- ardial perfusion SPECT introduced by misalignment between emission scan and CT-derived attenuation maps. JNucl Med 2004; 45: 1619-25.
13 Gregory PL, Batt ME, Kerslake RW. et al. The value of combining single photon emission computerised tomography and computerised tomography in the investigation of spondylolysis. Eur Spine J 2004; 13: 503-9.
14 Groves AM, Bird N, Tabor I. et al. 16-Detector multislice CT-skeletal. scintigraphy image co-registration. Nucl Med Commun 2004; 25: 1151-5.
15 Hendel RC. Attenuation correction: eternal dilemma or real improvement?. Q J Nucl Med Mol Imaging 2005; 49: 30-42.
16 Horger M, Eschmann SM, Pfannenberg C. et al. Evaluation of combined transmission and emission tomography for classification of skeletal lesions. AJRAmJRoentgenol 2004; 183: 655-61.
17 Keidar Z, Israel O, Krausz Y. SPECT/CT in tumor imaging: technical aspects and clinical applications. Semin Nucl Med 2003; 33: 205-18.
18 Kim JH, Czernin J, Allen-Auerbach MS. et al. Comparison between 18F-FDG PET, in-line PET/ CT, and software fusion for restaging of recurrent colorectal cancer. J Nucl Med 2005; 46: 587-95.
19 Matsunari I, Böning G, Ziegler SI. et al. Effects of misalignment between transmission and emission scans on attenuation-corrected cardiac SPECT. J Nucl Med 1998; 39: 411-6.
20 Moreira AP, Duarte LH, Vieira F. et al. Value of SPET/CT image fusion in the assessment of neuroendocrine tumours with 111In-pentetreotide scintigraphy. Rev Esp Med Nucl 2005; 24: 14-8.
21 Nakamoto Y, Tatsumi M, Cohade C. et al. Accuracy of image fusion of normal upper abdominal organs visualized with PET/CT. Eur J Nucl Med Mol Imaging 2003; 30: 597-602.
22 Nömayr A, Römer W, Hothorn T. et al. Anatomical accuracy oflesion localization. Retrospective interactive rigid image registration between 18F-FDG-PET and X-ray CT. Nuklearmedizin 2005; 44: 149-55.
23 Nömayr A, Römer W, Strobel D. et al. Anatomical accuracy ofhybrid SPECT/spiral CT in the lower spine. Nucl Med Commun 2006; 27: 521-8.
24 Pfannenberg AC, Eschmann SM, Horger M. et al. Benefit of anatomical-functional image fusion in the diagnostic work-up of neuroendocrine neoplasms. Eur J Nucl Med Mol Imaging 2003; 30: 835-43.
25 Römer W, Beckmann MW, Forst R. et al. SPECT/ Spiral-CT hybrid imaging in unclear foci of increased bone metabolism: acase report. Rontgen- praxis 2005; 55: 234-7.
26 Römer W, Fiedler E, Pavel M. et al. Attenuation correction of SPECT images based on separately performed CT: Effect on the measurement of regional uptake values. Nuklearmedizin 2005; 44: 20-8.
27 Römer W, Nömayr A, Uder M. et al. SPECT- guided CT for evaluating foci of increased bone metabolism classified as indeterminate on SPECT in cancer patients. J Nucl Med 2006; 47: 1102-6.
28 Römer W, Reichel N, Vija HA. et al. Isotropic reconstruction of SPECT data using OSEM3D: correlation with CT. Acad Radiol 2006; 13: 496-502.
29 Schillaci O, Danieli R, Manni C. et al. Is SPECT/ CT with a hybrid camera useful to improve scintigraphic imaging interpretation?. Nucl Med Commun 2004; 25: 705-10.
30 Schillaci O, Simonetti G. Fusion imaging in nuclear medicine-applications of dual-modality systems in oncology. Cancer Biother Radiopharm 2004; 19: 1-10.
31 Schillaci O, Spanu A, Madeddu G. 99mTc-sestami- bi and 99mTc-tetrofosmin in oncology: SPET and fusion imaging in lung cancer, malignant lymphomas and brain tumors. Q J Nucl Med Mol Imaging 2005; 49: 133-44.
32 Schillaci O. Functional-anatomical image fusion in neuroendocrine tumors. Cancer Biother Radio- pharm 2004; 19: 129-34.
33 Schillaci O. Hybrid SPECT/CT: a new era for SPECT imaging?. Eur J Nucl Med Mol Imaging 2005; 32: 521-4.
34 Stodilka RZ, Kemp BJ, Prato FS. et al. Importance of bone attenuation in brain SPECT quantification. J Nucl Med 1998; 39: 190-7.
35 Tang HR, Brown JK, DaSilva AJ. et al. Implementation of a combined CT scintillation camera system for localizing andmeasuring radionuclide uptake: experiments in phantoms and patients. IEEE Trans Nucl Sci 1999; 46: 551-7.
36 Tatsch K, Asenbaum S, Bartenstein P. et al. European Association of Nuclear Medicine Procedure Guidelines for Brain Perfusion SPET using 99mTc- labelled radiopharmaceuticals. Eur J Nucl Med Mol Imaging 2002; 29: BP36-42.
37 Tharp K, Israel O, Hausmann J. et al. Impact of 131I-SPECT/CT images obtained with an integrated system in the follow-up of patients with thyroid carcinoma. Eur J Nucl Med Mol Imaging 2004; 31: 1435-42.
38 Townsend DW, Beyer T, Blodgett TM. PET/CT scanners: a hardware approach to image fusion. Semin Nucl Med 2003; 33: 193-204.
39 Utsonomiya D, Shiraishi S, Imuta M. et al. Added value of SPECT/CT fusion in assessing suspected bone metastasis: comparison with scintigraphy alone and nonfused scintigraphy and CT. Radiology 2006; 238: 264-71.
40 Zaidi H, Hasegawa B. Determination of the attenuation map in emission tomography. J Nucl Med 2003; 44: 291-315.