Mieke Bus

4 55 Figure 1: . A) A C7 Dragonflytm Intravascular Imaging Probe 2.7 Fr (St. Jude Medical, St. Paul, Minnesota, USA). B) OCT Probe position during URS (left). # is papillary lesion, * is OCT probe. C) X-ray taken during OCT probe positioning. Inset shows a thin dark line, indicated by the arrow, to show the OCT probe. The OCT probe was introduced through the working channel of an ureterorenoscope (Karl Storz semi-rigid 9.5Fr, Karl Storz Flex XC, Olympus URF-V), resulting in simultaneous co-registered URS and OCT. Probe position was ensured by X-ray images. OCT imaging was performed at locations with macroscopic presence of tumor growth or suspected lesions during URS (Figures 1B, 1C). Standard pathological report of nephroureterectomy specimen was considered reference standard for comparison with OCT grading and OCT staging. Nephroureterectomy speci- mens were dissected and examined at the pathology department according to standard protocol. The OCT investigator was blinded for pathology results and pre-operative imaging. OCT datasets were subjected to in-house developed staging and grading protocols and compared with histological diagnosis. For staging, each OCT measurement was visually inspected and classified as normal (without visible lesion) or abnormal (with visible lesion). Visible lesions were divided in invasive and non-invasive by identifying the basement membrane that appears as a dark line between the urothelium and lamina propria. Interruption of this dark line was considered invasive. For grading, µ oct was determined in suspected lesions as described before. (3, 5, 19) The decrease of light intensity [mm -1 ] is quantified by fitting OCT data in a manually selected region of interest within a urothelial lesion to a single exponential decay model, after imperatively accounting for system specific calibrations. (20, 21) All suspected lesions were clearly identified through structural differences from normal appearing OCT images. Statistical analysis was performed using SPSS version 19.0 for Windows (Chicago, IL, USA). Because of unequal sample size, the Wilcoxon rank sum test was used to describe differ- ences in µ oct betweengrade 2 and grade 3 lesions. No reporting standards for IDEAL 1 and 2a studies are yet described. We therefore followed standard scientific reporting.