Comparison of dual-head coincidence gamma camera FDG imaging with FDG PET in detection of breast cancer and axillary lymph node metastasis

Dual-head coincidence gamma camera ¹⁸F-fluorodeoxyglucose (FDG) imaging was compared with FDG PET in the detection of breast cancer and axillary lymph node metastasis. Methods: Both coincidence gamma camera FDG imaging and FDG PET were performed in a cylindrical phantom containing spheres of different sizes and activity ratios (5:1, 10:1 and 15:1) and in 30 women (age range 32-78 y) with suspected breast cancer. Biopsies or mastectomies were performed in all patients. Images were visually assessed, and the count ratio between tumor and normal tissue (T/N ratio) was calculated. Results: In the phantom studies, coincidence gamma camera imaging visualized the smallest sphere (1.0 cm) at a ratio of 15:1 but not at ratios of 5:1 and 10:1. Coincidence gamma camera imaging visualized the other spheres (≥1.3 cm) at all ratios. PET visualized all spheres at all ratios. In the clinical studies, 22 of 26 breast carcinomas detected by PET were also detected by coincidence gamma camera imaging. Coincidence gamma camera imaging detected all of the carcinomas ≥2 cm in diameter (n = 10) and 12 of 16 carcinomas <2 cm. In breast carcinomas detected by both PET and coincidence gamma camera imaging, the T/N ratio in non-attenuation-corrected PET (7.12 ± 7.13) was significantly higher than in coincidence gamma camera imaging (2.90 ± 1.47, P < 0.005). Four of 8 axillary lymph node metastases detected by PET were detected by coincidence gamma camera imaging. Of 9 axillary lymph node metastases <1.0 cm in diameter, 7 and 3 were detected by PET and coincidence gamma camera imaging, respectively. Conclusion: Coincidence gamma camera imaging is useful in detecting breast carcinoma ≥2 cm in diameter but is not reliable for breast carcinoma <2 cm in diameter. Coincidence gamma camera imaging may be useless or even dangerous in the detection of axillary lymph node metastasis.