Respiratory-gated PET imaging with reduced scanning time superior to ungated imaging for suspect malignancies

Respiratory gating in PET imaging can improve lesion presentation and detectability but requires a longer imaging time. Guobing Liu from the Shanghai Institute of Medical Imaging, Shanghai, China, and colleagues conducted the single-centre study to look into the performance of respiratory-gating imaging with reduced acquisition time using PET/CT scanner.

For this purpose, the authors analyzed data of 71 patients with suspect malignancies who underwent total-body 2-[18F]-fluoro-2-deoxy-D-glucose PET/CT for 15 min with respiration recorded studied. Four reconstructions were performed for each examination: Ungated-5, using data from the first 5 min; Ungated-15, using all coincidences; Gated-6 using data of the first 6 min with respiratory gating; and Gated-15, using all coincidences but with respiratory gating. Image quality was evaluated, lesions were quantified, and a comparison was drawn between both in four image sets.

The study led to the following findings:

• The authors found 390 lesions in the thorax and upper abdomen.
• Lesion detectability was remarkably higher in gated-15 (97.2%) than in ungated-15 (93.6%) and ungated-5 (92.3%) but comparable to Gated-6 (95.9%). For quantitative analyses, a total of 131 lesions were selected.
• Lesions in Gated-15 presented notably larger standardized uptake values, tumour-to-liver ratio, and tumour-to-blood ratio but smaller metabolic tumor volume than those in Ungated-15 and Ungated-5. These differences were more evident in small lesions and lesions from sites other than mediastinum/retroperitoneum. These indices were, however, comparable between Gated-6 and Gated-15.
• In gated images, higher but acceptable image noise was identified than in ungated images.

"Our findings revealed that the total-body PET scanner allows respiratory-gated imaging with clinically acceptable and reduced scanning time," the authors concluded.

Reference:

Liu, G., Chen, S., Hu, Y. et al. Respiratory-gated PET imaging with reduced acquisition time for suspect malignancies: the first experience in application of total-body PET/CT. Eur Radiol (2022). https://doi.org/10.1007/s00330-022-09369-z