Mieke Bus

88 Chapter 6 Table 1: Imaging properties of ELUS and OCT ELUS OCT Contrast mechanism Sound scattering Light scattering Aim Real time imaging of luminal structures Real time information on pathological diagnosis Imaging depth 20-40mm 2-3mm Resolution Axial 200 µm Lateral 200-250 µm Axial 15 µm Lateral 20-40µm Advantage High imaging penetration depth Fast data acquisition High resolution imaging Information on tumor grade and stage Limitations Slow data aquisition speed Low resolution imaging Diminished imaging depth range Finally, the challenge in comparing serially acquired OCT with ELUS data is that no absolute co-localisation can be attained without a second, common imaging modality for co-regis- tration. Rapid co-registration can be achieved by automated pixel intensity based image correlation software. (5) However, due to serial introduction of the OCT and ELUS probe, the imaged ureter tissue can be shifted and altered and subsequently visualized differently. CT based co-registration has the benefit of absolute spatial co-localisation of two inde- pendently acquired datasets. (6) We hypothesize that the high resolution of OCT increases the visibility of small structures and thin layers in the ureter itself, including urothelial layer, while the increased depth imag- ing of ELUS contributes to the visibility of tissue structures beyond 2mm in depth. The first aim of this feasibility study is to investigate the use of CT for optimal co-registration of OCT and ELUS. The second aim of this study is to determine whether co-registered OCT and ELUS could improve visualisation of large (>2mm) upper urinary tract tumors and discriminates between non-invasive and invasive tumors, by performing co-registered OCT and ELUS measurements in five nephroureterectomy specimens of patients with proven UUT-UC. We compared individual OCT and ELUS datasets on their ability to visualize individual tissue layers of the ureter (urothelium, lamina propria, muscularis propria and periureteral fat). This study will be performed in the context of the first stage of the IDEAL model designed for evaluation new surgical techniques (1 Innovation/Idea, 2a Development, 2b Exploration, 3 Assessment, 4 Long-term follow-up). (7, 8) Material & Methods Five complete resected nephroureterectomy specimens including bladder cuff of patients with biopsy confirmed UUT-UC were examined using serial OCT and ELUS measurements combined with co-registered CT (figure 1).