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

摘要

>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.