High accuracy of mesoscopic epi-fluorescence tomography for non-invasive quantitative volume determination of fluorescent protein-expressing tumours in mice

Objectives To compare mesoscopic epi-fluorescence tomography (MEFT) and EPRI-illumination reflectance imaging (EPRI) for quantitative tumour size assessment in mice. Methods Tumour xenografts of green/red fluorescent protein (GFP/RFP)-expressing colon cancer cells were measured using MEFT, EPRI, ultrasound (US) and micro computed tomography (μCT) at day 14 post-injection (n06). Results from MEFT and EPRI were correlated with each other and with US and μCT (reference methods). Tumour volumes were measured ex vivo by GFP and RFP fluorescence imaging on cryoslices and compared with the in vivo measurements. Results High correlation and congruency were observed between MEFT, US and μCT (MEFT/US: GFP: r200.96; RFP: r200.97, both P<0.05; MEFT/μCT: GFP: r200.93; RFP: r200.90; both P<0.05). Additionally, in vivo MEFT data were highly correlated and congruent with ex vivo cryoslice imaging results (GFP: r200.96; RFP: r200.99; both P<0.05). In comparison, EPRI significantly overestimated tumour volumes (P<0.05), although there was a significant correlation with US and μCT (EPRI/US: GFP: r200.95; RFP: r200.94; both P<0.05; EPRI/μCT GFP: r200.86; RFP: r200.86; both P<0.05). Conclusions Fluorescence distribution reconstruction using MEFT affords highly accurate three-dimensional (3D) tumour volume data showing superior accuracy compared to EPRI. Thus, MEFT is a very suitable technique for quantitatively assessing fluorescence distribution in superficial tumours at high spatial resolution. Key Points ̇ Mesoscopic epi-fluorescence tomography (MEFT) is an important new molecular imaging technique. ̇ MEFT allows accurate size determination of superficial tumours with high resolution. ̇ MEFT is a suitable technique for longitudinal assessment of tumour growth. ̇ MEFT allows 3D reconstruction and quantification of fluorescence distributions.