Proof of Concept of a Multimodal Intravital Molecular Imaging System for Tumour Transpathology Investigation

Abstract Background: Transpathology highlights the interpretation of underlying physiology behind molecular imaging. However, it remains challenging due to the discrepancies between in vivo and in vitro measurements and difficulties of precise co-registration between multi-scaled images. This study aims to develop a multimodal intravital molecular imaging (MIMI) system as a tool for in vivo tumour transpathology investigation. Methods: The proposed MIMI system integrates high-resolution positron imaging, magnetic resonance imaging (MRI) and microscopic imaging on a dorsal skin window chamber on a nude rat. The window chamber frame was designed to be compatible with multimodal imaging and its fiducial markers were customized for precise physical alignment among modalities. The co-registration accuracy was evaluated based on phantoms with thin catheters. For proof of concept, the human colorectal adenocarcinoma cell line HT-29 was imaged. The tissue within the window chamber was sectioned, fixed, hematoxylin-eosin (HE) stained for comparison with multimodal in vivo imaging. Results: With the physical alignment via fiducial markers, the co-registration errors of the MIMI system were 0.18 ± 0.27 mm between MRI and positron imaging, 0.19 ± 0.22 mm between positron imaging and microscopic imaging, and 0.15 ± 0.27 mm between MRI and microscopic imaging. A pilot test demonstrated that the MIMI system provides an integrative visualization of the tumour anatomy, perfusion and metabolism of the in vivo tumour microenvironment. Conclusions: The established MIMI system provided a co-registered in vivo platform for trans-scale and transparent investigation of the underlying pathology behind imaging, which has the potential to enhance the translation of molecular imaging.