Objective: To investigate the feasibility of using high-sensitivity projection [F]fluoro-deoxyglucose imaging to monitor chemotherapeutic efficacy in BALB/c mice bearing CT-26 tumor implants.
Methods: A planar positron imaging system (PPIS)-4800 and a microPET R4 were used for projection and tomographic imaging, respectively. Six disks filled with different volumes of F-FDG solution were scanned by PPIS for calibration check. Tumor-bearing mice were treated with saline (control) or cyclophosphamide by intraperitoneal injections. Tumor responses were evaluated by both PPIS and microPET imaging.
Results: The disk-activity ratios obtained from PPIS were 1.00: 1.30: 1.98: 2.48: 2.73: 3.53 with corresponding volume ratios of 1.0: 1.5: 2.0: 2.5: 3.0: 3.5. PPIS imaging in tumor-bearing mice showed that the tumor/non-tumor ratios were 1.62, 2.12, 3.03, 4.46, and 3.61 on days 7, 10, 13, 17, and 20, respectively, after tumor inoculation. In addition, PPIS was used to monitor the chemotherapeutic effect of cyclophosphamide on tumor-bearing mice. The correlation coefficients between the tumor sizes and tumor/non-tumor ratios for microPET and PPIS were 0.63 and 0.72, respectively, in the control group, and were 0.98 and 0.81, respectively, in the cyclophosphamide-treated group.
Conclusion: This study showed that PPIS imaging is a feasible modality for monitoring tumor responses. These results suggest that PPIS, a potential high-throughput screening imaging system, may be used for the preclinical evaluation of tumor response to new anticancer drugs using murine tumor models.