Sequential IVIM-Parametric as a Potential Image Biomarker in Evaluating the Radiosensitivity of Human Nasopharyngeal Carcinoma Xenografts

BACKGROUND AND PURPOSE Intravoxel incoherent motion (IVIM) is a considerable functional MR sequence in evaluated the tumor’s response to chemo-radiotherapy. Our aim was to investigate the sequential IVIM parametric in assessing the dynamic changes of histopathological features on nasopharyngeal carcinoma (NPC) xenografts after receiving the fractional radiations. EXPERIMENTAL APPROACH: Sixty BALB/c-nu nude mice were transplanted with NPC cell lines of CNE-1 and CNE-2 to raise xenografts which further received the fractional radiations. On 3.0T MR system, IVIM (14 b-factors: 0~1000 s/mm 2 ) was performed on xegnorafts after radiations. IVIM-parametric of D, f and D* accompanied with the cellularity and necrosis proportion of NPC xenografts were calculated and analyzed respectively. KEY RESULTS NPC xenografts exhibited a larger D and necrosis proportion coupled with a smaller D*, f and cellularity after fractional radiations, and CNE-2 xenografts presented greater changes than CNE-1 xenografts (all P<0.01). Parametric D and f correlated negatively (r=-0.824, P<0.001) while D* correlated positively with f (r=0.758, P<0.001) and D (r=0.625, P=0.042). Moreover, D correlated negatively with cellularity (r s =-0.861, P<0.001) and positively with necrosis proportion (r s =0.952, P<0.001), f behaved a positive correlation with cellularity (r s =0.627, P<0.001) and negative with necrosis proportion (r s =-0.649, P<0.001). CONCLUSIONS AND IMPLICATIONS: Sequential parametric derived from IVIM are valuable in characterizing the dynamic changes in histopathological features of NPC xenografts and can be utilized as a potential image biomarker for non-invasive assessment of tumor’s radiosensitivity.