Speeding up PET/MR for cancer staging of children and young adults.

Objective: Combining F-FDG PET with whole-body MR for paediatric cancer staging is practically feasible if imaging protocols can be streamlined. We compared F-FDG PET/STIR with accelerated F-FDG PET/FSPGR for whole-body tumour imaging in children and young adults.

Methods: Thirty-three children and young adults (17.5 ± 5.5 years, range 10-30) with malignant lymphoma or sarcoma underwent a F-FDG PET staging examination, followed by ferumoxytol-enhanced STIR and FSPGR whole-body MR. F-FDG PET scans were fused with MR data and the number and location of tumours on each integrated examination were determined. Histopathology and follow-up imaging served as standard of reference. The agreement of each MR sequence with the reference and whole-body imaging times were compared using Cohen's kappa coefficient and Student's t-test, respectively.

Results: Comparing F-FDG PET/FSPGR to F-FDG PET/STIR, sensitivities were 99.3 % for both, specificities were statistically equivalent, 99.8 versus 99.9 %, and the agreement with the reference based on Cohen's kappa coefficient was also statistically equivalent, 0.989 versus 0.992. However, the total scan-time for accelerated FSPGR of 19.8 ± 5.3 minutes was significantly shorter compared to 29.0 ± 7.6 minutes for STIR (p = 0.001).

Conclusion: F-FDG PET/FSPGR demonstrated equivalent sensitivities and specificities for cancer staging compared to F-FDG PET/STIR, but could be acquired with shorter acquisition time.

Key Points: • Breath-hold FSPGR sequences shorten the data acquisition time for whole-body MR and PET/MR. • Ferumoxytol provides long-lasting vascular contrast for whole-body MR and PET/MR. • F-FDG PET/FSPGR data provided equal sensitivity and specificity for cancer staging compared to F-FDG PET/STIR.