Demonstration of the reproducibility of free-breathing diffusion-weighted MRI and dynamic contrast enhanced MRI in children with solid tumours: a pilot study

OBJECTIVES: The objectives are to examine the reproducibility of functional MR imaging in children with solid tumours using quantitative parameters derived from diffusion-weighted (DW-) and dynamic contrast enhanced (DCE-) MRI. METHODS: Patients under 16-years-of age with confirmed diagnosis of solid tumours (n = 17) underwent free-breathing DW-MRI and DCE-MRI on a 1.5 T system, repeated 24 hours later. DW-MRI (6 b-values, 0-1000 sec/mm(2)) enabled monoexponential apparent diffusion coefficient estimation using all (ADC(0-1000)) and only ≥100 sec/mm(2) (ADC(100-1000)) b-values. DCE-MRI was used to derive the transfer constant (K(trans)), the efflux constant (k(ep)), the extracellular extravascular volume (v(e)), and the plasma fraction (v(p)), using a study cohort arterial input function (AIF) and the extended Tofts model. Initial area under the gadolinium enhancement curve and pre-contrast T(1) were also calculated. Percentage coefficients of variation (CV) of all parameters were calculated. RESULTS: The most reproducible cohort parameters were ADC(100-1000) (CV = 3.26 %), pre-contrast T(1) (CV = 6.21 %), and K(trans) (CV = 15.23 %). The ADC(100-1000) was more reproducible than ADC(0-1000), especially extracranially (CV = 2.40 % vs. 2.78 %). The AIF (n = 9) derived from this paediatric population exhibited sharper and earlier first-pass and recirculation peaks compared with the literature’s adult population average. CONCLUSIONS: Free-breathing functional imaging protocols including DW-MRI and DCE-MRI are well-tolerated in children aged 6 - 15 with good to moderate measurement reproducibility. KEY POINTS: • Diffusion MRI protocol is feasible and well-tolerated in a paediatric oncology population. • DCE-MRI for pharmacokinetic evaluation is feasible and well tolerated in a paediatric oncology population. • Paediatric arterial input function (AIF) shows systematic differences from the adult population-average AIF. • Variation of quantitative parameters from paired functional MRI measurements were within 20 %.