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

Abstract

Objective Combining 18F-FDG PET with whole-body MR for paediatric cancer staging is practically feasible if imaging protocols can be streamlined. We compared 18F-FDG PET/STIR with accelerated 18F-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 years) with malignant lymphoma or sarcoma underwent a 18F-FDG PET staging exam, followed by ferumoxytol-enhanced STIR and FSPGR whole-body MR. 18F-FDG PET scans were fused with MR data and the number and location of tumours on each integrated exam was determined. Histopathology and follow-up imaging served as standard of reference. The agreement of each MR sequence with the reference and the whole-body imaging times were compared using Cohen’s kappa coefficient and student t-test, respectively. Results Comparing 18F-FDG PET/FSPGR to 18F-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 18F-FDG PET/FSPGR demonstrated equivalent sensitivities and specificities for cancer staging compared to 18F-FDG PET/STIR, but could be acquired with shorter acquisition time.

How to Provide Gadolinium-Free PET/MR Cancer Staging of Children and Young Adults in Less than 1 h: the Stanford Approach

“…Previous PET/MR studies in pediatric patients evaluated the head to mid thighs with T2-weighted sequences in 60 and 45 min, respectively [8, 14]. We covered the same area in 24 min, using axial ferumoxytol-enhanced T1-weighted sequences, which are faster, provide better vessel delineation and anatomical information at a resolution that better matched a PET/CT scan [31]. To cover the whole body head to toe, we added additional beds depending on the patient height, which resulted in additional 4–12 min of scan time.…”

Current and potential imaging applications of ferumoxytol for magnetic resonance imaging

“…Integrated ferumoxytol-enhanced WB-DW MR images provided equal sensitivities and specificities for cancer staging compared to 18F-FDG-PET/ CT (28). More recent developments marry advantages of both imaging technologies towards 18F-FDG- PET/MR applications wherein ferumoxytol-enhanced anatomical T1-weighted MR images are merged with 18F-FDG-PET images (112). On 18F-FDG-PET/MR scans, ferumoxytol can help to differentiate malignant lymph nodes (18F-FDG positive, no iron uptake) from benign, inflammatory nodes (18F-FDG positive and iron uptake) as well as neoplastic bone marrow disease (18F-FDG positive, no iron uptake) from normal hypercellular hematopoietic marrow (18F-FDG positive and iron uptake) WB-DW=whole-body diffusion-weighted.…”

Ten Things You Might Not Know about Iron Oxide Nanoparticles

“…By contrast, due to their large size, iron oxide nanoparticles do not extravasate in most tissues. This can be harnessed for MR angiography ( 7 , 8 ), long-lasting vascular enhancement in whole-body MR imaging and positron emission tomography/MR imaging tumor staging ( 82 , 83 ), MR imaging of vascular malformations ( 84 ), MR imaging of inflammation ( 31 , 85 ), and interestingly, MR detection of early tumor necrosis ( 10 , 85 ). Due to a lower degree and rate of extravasation and a higher drug concentration gradient between vessels and tissues, T1-based steady-state angiography can be performed with iron oxide doses of 1 mg of iron per kilogram or less ( 24 ).…”