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Journal of Nuclear Medicine Technology Volume 32, Number 4, 2004 190-197
© 2004 by Society of Nuclear Medicine

Coincidence Imaging Using 2 Dual-Head {gamma}-Camera Systems, With and Without Attenuation Correction

Einat Even-Sapir, MD, DSc1, Bella Yuzefovich, DSc2, Elka Miller, MD3, Jean-Paul Bouhnik, PhD2, Osnat Zak, MSc2, Hedva Lerman, MD1, Genady Lievshitz, MD1 and Charles Levin, MD3

1 Department of Nuclear Medicine, Tel-Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel;
2 Division of Functional Imaging, General Electric Medical System, Haifa, Israel;
3 Department of Radiology, Tel-Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel

Objective: Coincidence imaging enhances the potential for imaging a greater number of patients with 18F-FDG in centers that do not have dedicated PET systems. The purpose of this study was to compare, in a clinical setting, coincidence imaging for tumor detection using 2 dual-head {gamma}-camera systems, one equipped with a 5/8-in. (16 mm) detector (CoDe5) and the other equipped with a newly designed 1-in. (25.4 mm) detector (CoDe8) with an x-ray tube installed in its gantry.

Methods: Thirty consecutive patients were studied by both systems during the same visit and had 4 image sets for comparison: CoDe5 without attenuation correction (CoDe5NC), CoDe8 with (CoDe8AC) and without (CoDe8NC) attenuation correction, and fused coincidence-CT images. The target-to-background ratio (T/Bg ratio) and target-to-nontarget ratio (T/NT ratio) were calculated for each tumor site.

Results: On visual assessment, 61 tumor sites were detected on CoDe8AC images. Of these, 59 (97%) were detected on CoDe8NC and 54 (88%) were detected on CoDe5NC images. Fused images improved image interpretation in 10 patients (33%) compared with coincidence images alone. Data added by fusion were of clinical relevance in 6 patients (20%). On quantitative assessment, the number of accepted events by the CoDe8 was significantly higher than that by CoDe5 (5.21 ± 1.46 million vs. 1.27 ± 0.36 million, P < 0.001). When comparing CoDe5 with CoDe8 images without attenuation correction, the T/Bg and T/NT ratios were significantly higher on the CoDe8 images (P < 0.0005 and P < 0.0005, respectively). When comparing CoDe8 images with and without attenuation correction, the T/Bg ratio was better on the attenuation-corrected images (P < 0.0005).

Conclusion: Coincidence imaging with 1-in. detectors and attenuation correction improve image quality and, to a lesser extent, the tumor detection rate compared with the 5/8-in. detectors and noncorrected images. The data added by fusion of coincidence images to CT findings were clinically relevant in 20% of the patients.

Key Words: coincidence imaging; 18F-FDG; {gamma}-camera; PET; neoplasms






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