Mieke Bus

96 Chapter 6 In the OCT imaging datasets tumor invasion could not be assessed in two of the five patients because tumor thickness hampered OCT interpretation. Tumor thickness up to ~2 mm could be reliable assessed with OCT (table 3). In our ELUS imaging datasets exact staging was not possible, due to the increased imaging depth. However ELUS provided a better overview of the lesions compared to OCT. Discussion This paper demonstrates the first results of one to one comparison of ELUS and OCT data of the human ureter. It shows that OCT permits high-resolution imaging of the upper urinary tract and UUT-UC whereas ELUS provides more depth information. These results warrant hardware integration of both technologies in order to optimize the diagnosis of UUT-UC. The combination of OCT and ELUS allows for high-resolution imaging and greater imaging depth at the same time. This study demonstrates the potential of co-registered OCT and ELUS to visualize anatomical layers of the human upper urinary tract and the potential to dis- criminate between normal and suspected areas in an ex-vivo setting. However, the greater imaging depth obtained using ELUS did not result in improved staging of UUT-UC, since the imaging resolution of ELUS is too low to render reliable staging. Optical Coherence Tomography of the upper urinary tract. This study has shown that visualization of the urothelium, lamina propria and muscularis propria is feasible with OCT in normal appearing tissue. The imaging depth of ~2mm even allows imaging into the peri-ureteral fat layer. However, the imaging depth is a clear limita- tion when assessing a papillary lesion, impeding visualization of the lesion base and under- lying layers, which is needed for an accurate estimation of tumor invasiveness. The ability of OCT to distinguish the different anatomical layers of porcine and human ureter has been demonstrated and the potential to qualitatively differentiate between non-invasive and invasive UUT-UC has also been shown. (4, 11, 12) This gives OCT the potential to stage UUT-UC. In addition, OCT has the potential to grade UUT-UC by quantification of the optical atten- uation coefficient (µ oct ). (4, 12-16) Malignant tissue manifests as an increased amount of mito- chondria and an increased nuclear/cytoplasm ratio. As a result, malignant tissue has different scattering properties compared to benign tissue, allowing visible lesions to be graded in OCT images by analyzing the decay of light in tissue expressed as µ oct . Although OCT could be used for staging of small lesions, large lesions exceeded OCT imaging depth range, making staging not possible for lesions larger than ~2mm in-depth. Merging OCT with an imaging modality with a larger imaging depth range overcomes this important limitation of OCT, while the ability of OCT to grade lesions remains.