Improved quantification in single-pinhole and multiple-pinhole SPECT using micro-CT information
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The purpose of this study was to demonstrate the feasibility of accurate quantification in pinhole SPECT using micro-CT information.
Pinhole SPECT scans were performed using a clinical dual-head gamma camera. Each pinhole SPECT scan was followed by a micro-CT acquisition. Functional and anatomical images were coregistered using six point sources visible with both modalities. Pinhole SPECT images were reconstructed iteratively. Attenuation correction was based on micro-CT information. Scatter correction was based on dual and triple-energy window methods. Phantom and animal experiments were performed. A phantom containing nine vials was filled with different concentrations of 99mTc. Three vials were also filled with CT contrast agent to increase attenuation. Activity concentrations measured on the pinhole SPECT images were compared with activity concentrations measured by the dose calibrator. In addition, 11 mice were injected with 99mTc-labelled Nanobodies. After acquiring functional and anatomical images, the animals were killed and the liver activity was measured using a gamma-counter. Activity concentrations measured on the reconstructed images were compared with activity concentrations measured with the gamma counter.
The phantom experiments demonstrated an average error of −27.3 ± 15.9% between the activity concentrations measured on the uncorrected pinhole SPECT images and in the dose calibrator. This error decreased significantly to −0.1 ± 7.3% when corrections were applied for nonuniform attenuation and scatter. The animal experiment revealed an average error of −18.4 ± 11.9% between the activity concentrations measured on the uncorrected pinhole SPECT images and measured with the gamma counter. This error decreased to −7.9 ± 10.4% when attenuation and scatter correction was applied.
Attenuation correction obtained from micro-CT data in combination with scatter correction allows accurate quantification in pinhole SPECT.
KeywordsAttenuation correction attenuation maps CT Molecular imaging Small-animal imaging Reconstruction pinhole SPECT
Tony Lahoutte is a Senior Clinical Investigator of the Research Foundation – Flanders (Belgium) (FWO). This work was supported by the Inter-University Attraction Poles Programme 6-38 of the Belgian Science Policy and by grant G.0569.08 from the Fonds Wetenschappelijk Onderzoek Vlaanderen.
- 5.Matsumura A, Mizokawa S, Tanaka M, Wada Y, Nozaki S, Nakamura F, et al. Assessment of microPET performance in analyzing the rat brain under different types of anesthesia: comparison between quantitative data obtained with microPET and ex vivo autoradiography. Neuroimage 2003;20(4):2040–50.PubMedCrossRefGoogle Scholar
- 8.Chantler CT, Olsen K, Dragoset RA, Chang J, Kishore AR, Kotochigova SA, et al. X-ray form factor, attenuation, and scattering tables (version 2.1). Physics Laboratory, Physical Reference Data. Gaithersburg, MD: National Institute of Standards and Technology; 2005. http://physics.nist.gov/ffast.
- 23.Ogawa K, Chuga A, Ichihara T, Kuba A, Hashimoto S. Quantitative image reconstruction using position-dependent scatter correction in single photon emission CT. Conference record. 1992 Nuclear Science Symposium and Medical Imaging Conference, Orlando, 1993. p. 1011–1013.Google Scholar