Zero Echo Time-Based PET/MRI Attenuation Correction in Patients With Oral Cavity Cancer: Initial Experience

The aims of this study were to demonstrate the feasibility of zero echo time (ZTE) MRI for jawbone identification, and to evaluate the quantitative performance of F-FDG PET/MRI with ZTE-based attenuation correction (ZTE-AC) compared with PET/CT and PET/MRI with Dixon MR-based AC (Dixon-AC) in patients with oral cavity cancer (OCC).

Thirteen OCC patients underwent whole-body F-FDG PET/CT and subsequent regional PET/MRI with Dixon-AC and ZTE-AC in 1 day. SUVs of the primary OCC and metastatic cervical lymph nodes (CLNs) were measured on PET/CT (SUVCT), PET/MRI with Dixon-AC (SUVDixon), and ZTE-AC (SUVZTE). The SUVs were then compared.

The ZTE MRI scans minimized the effects of metal artifacts from dentures, and ZTE-AC maps correctly delineated the jawbones. SUVDixon and SUVZTE had significant positive correlations with SUVCT (Pearson r = 0.97 and r = 0.99 for OCC, and r = 0.98 and r = 0.98 for CLNs, respectively). The mean ± SD of SUVCT, SUVDixon, and SUVZTE were 14.4 ± 8.0, 14.5 ± 8.6, and 15.6 ± 8.8 for OCC, and 6.3 ± 3.0, 8.0 ± 4.0, and 7.6 ± 3.9 for CLNs, respectively. For OCCs, SUVZTE was significantly higher than SUVCT (P < 0.05), whereas there was no significant difference between SUVCT and SUVDixon or between SUVDixon and SUVZTE. For CLNs, SUVDixon and SUVZTE were significantly higher than SUVCT (P < 0.01 and P < 0.05, respectively), and SUVDixon was significantly higher than SUVZTE (P < 0.01).

ZTE MRI can correctly identify jawbones while minimizing the effects of metal artifacts. The ZTE-AC method in F-FDG PET/MRI reduces the underestimation of tracer uptake due to Dixon-AC jawbone errors and improves the quantitative performance of PET for OCC patients.