Study on the best acquisition time of^99mTc-PSMA SPECT for the prostate cancer imaging

Objectives: Prostate specific membrane antigen (PSMA) is a transmembrane glycoprotein that is highly expressed in prostate cancer. 68Ga-PSMA PET/CT has been commonly used in the diagnosis, curative effect evaluation of prostate cancer, but the cost of examination is too high, which limits its use. Compared with that, the advantages of ^99mTc-PSMA SPECT imaging are relatively obvious. Not only are SPECT imaging relatively popular and inexpensive, but Technetium 99m is easy to obtain, and the imaging repeatability also is longer than Gallium 68. However, there are few studies on the optimal imaging time of ^99mTc-PSMA SPECT imaging. In this study, ^99mTc-PSMA SPECT plane imaging of prostate cancer was performed at multiple time points after injection and image analysis was performed to obtain the best acquired time point.

Methods: Prostate cancer patients after ^99mTc-PSMA injection was given SPECT whole-body plane imaging under the same acquisition conditions at 30 minute, 1 hour, 2 hours, and 3 hours after injection, and the target/non-target (T/NT) ratios of the parotid gland, liver, kidney, metastatic lymph node, and bone metastasis were calculated using computerized region of interest (ROI technology).

Results: In the T/NT ratio, the liver uptake was highest in 2 hours, and the parotid gland, kidney, metastatic lymph nodes, and bone metastases were highest in 3 hours. The image result showed that the 3-hour time point was of good quality, with the highest lesion uptake.

Conclusions: For the ^99mTc-PSMA SPECT imaging of prostate cancer, 3-hour imaging time point seem to be better than other points.

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