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Importance of Attenuation Correction (AC) for Small Animal PET Imaging
Cluster for Molecular Imaging, Faculty of Health Sciences & Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, University of Copenhagen, Blegdamsvej 3, Copenhagen DK-2200, Denmark
* Author to whom correspondence should be addressed.
Received: 17 August 2012; in revised form: 13 September 2012 / Accepted: 8 October 2012 / Published: 9 October 2012
Abstract: The purpose of this study was to investigate whether a correction for annihilation photon attenuation in small objects such as mice is necessary. The attenuation recovery for specific organs and subcutaneous tumors was investigated. A comparison between different attenuation correction methods was performed. Methods: Ten NMRI nude mice with subcutaneous implantation of human breast cancer cells (MCF-7) were scanned consecutively in small animal PET and CT scanners (MicroPETTM Focus 120 and ImTek’s MicroCATTM II). CT-based AC, PET-based AC and uniform AC methods were compared. Results: The activity concentration in the same organ with and without AC revealed an overall attenuation recovery of 9–21% for MAP reconstructed images, i.e., SUV without AC could underestimate the true activity at this level. For subcutaneous tumors, the attenuation was 13 ± 4% (9–17%), for kidneys 20 ± 1% (19–21%), and for bladder 18 ± 3% (15–21%). The FBP reconstructed images showed almost the same attenuation levels as the MAP reconstructed images for all organs. Conclusions: The annihilation photons are suffering attenuation even in small subjects. Both PET-based and CT-based are adequate as AC methods. The amplitude of the AC recovery could be overestimated using the uniform map. Therefore, application of a global attenuation factor on PET data might not be accurate for attenuation correction.
Keywords: attenuation correction; small animal; PET imaging; MicroPET; molecular imaging
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El Ali, H.H.; Bodholdt, R.P.; Jørgensen, J.T.; Myschetzky, R.; Kjaer, A. Importance of Attenuation Correction (AC) for Small Animal PET Imaging. Diagnostics 2012, 2, 42-51.
El Ali HH, Bodholdt RP, Jørgensen JT, Myschetzky R, Kjaer A. Importance of Attenuation Correction (AC) for Small Animal PET Imaging. Diagnostics. 2012; 2(4):42-51.
El Ali, Henrik H.; Bodholdt, Rasmus Poul; Jørgensen, Jesper Tranekjær; Myschetzky, Rebecca; Kjaer, Andreas. 2012. "Importance of Attenuation Correction (AC) for Small Animal PET Imaging." Diagnostics 2, no. 4: 42-51.