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Use of segmented CT transmission map to avoid metal artifacts in PET images by a PET-CT device

Siroos Mirzaei12*, Michel Guerchaft3, Christopher Bonnier1, Peter Knoll2, Michel Doat1 and Peter Braeutigam1

Author Affiliations

1 Centre National PET, Clinique Ste. Thérèse, Luxembourg

2 Wilhelminenspital, Institute of Nuclear Medicine, Vienna, Austria

3 Philips Medical Systems, BeNeLux

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BMC Nuclear Medicine 2005, 5:3  doi:10.1186/1471-2385-5-3

Published: 14 June 2005

Abstract

Background

Attenuation correction is generally used to PET images to achieve count rate values independent from tissue densities. The goal of this study was to provide a qualitative comparison of attenuation corrected PET images produced by a PET-CT device (CT, 120 kV, 40 mAs, FOV 600 mm) with and without segmentation of transmission data (ACseg+ and ACseg-respectively). Methods: The reconstructed images were compared to attenuation corrected images obtained with a high-energy transmission source (Cs-137 – 662 keV).

Thirty oncologic patients were studied using CT and 137Cs for attenuation correction. All image data were acquired using the Gemini PET-CT scanner (Philips Medical Systems). It is an open PET-CT system that consists of the MX8000 multislice CT and the Allegro PET scanner arranged in a separable configuration. Images with ACseg+ and ACseg- were analyzed simultaneously in coronal, sagittal and transaxial planes. Two nuclear medicine physicians reviewed the image sets. Results: The image quality in the area of metal implants was better with ACseg+ than ACseg-, without metal induced artifacts generally observed in CT corrected images. Further the images with ACseg+ were qualitatively comparable to those obtained with 137Cs attenuation correction. Conclusions: In case of metal implants, PET studies corrected by CT should preferably use the ACseg+ method to avoid the image artifacts.