Mieke Bus

7 109 (selective) cytology and biopsies, the added value of OCT in clinical practice can be deter- mined. Despite this lack of knowledge, there are several clinical applications conceivable, which are outlined below. First of all, OCT might be of value in improving the quality of resection of urothelial tumours in the ureter. By evaluating the resection margins with OCT, one might be able to know if the resection is complete at time of the operation. Besides evaluating the lateral borders of the resection area, these techniques could also be of benefit in determining the depth of the resection. If OCT measurements of the base of a resection plane confirm urothelial car- cinoma, one can complete the resection in depth, if technically possible. However, an initial study performed on ex-vivo human bladder urothelial biopsies showed that factors typical for ex-vivo settings (e.g. cauterization of bladder tissue specimens) on µ oct -based grading of human bladder cancer were inconclusive but indicative of the need for in-vivo evaluation. (14) More knowledge on the appearance of cauterized urothelium in OCT images is necessary and should be obtained in an in-vivo setting, as cauterization at resection margins might lead to problematic artefacts. (15) Another possible implementation of OCT in a clinical setting could be OCT guided partial ureterectomy. Using OCT can help to precisely determine the tumour margin. This gives the urologist information of the tumour margin, making precise partial ureterectomy possible. In patients with low-grade, low-stage disease and a recurrence shown by OCT to be again low-grade, endoscopic laser fulguration and/or coagulation may be applied. One of the drawbacks of laser treatment is the fact that no specimen for pathology is obtained for defi- nite diagnosis. The risk exists that progression has occurred without being noticed; therefore pathological confirmation of stage and grade is desirable. OCT can provide this confirmation and make laser fulguration a more safely and reliable mode of treatment. Additionally, it is a less invasive determination of disease grade and stage than biopsies. (15) Another interesting future perspective is the merging of OCT with other optical diagnostics techniques like Narrow Band Imaging (NBI). NBI is an optical image enhancement technique designed for endoscopic applications, with demonstrated value in gastroenterology and urology. (16, 17) NBI takes advantage of altered blood vessel morphology of mucosa to enhance contrast between mucosa and microvascular structures. This technique is based on the prin- ciple that the depth of light penetration into the mucosa increases with increasing wave- length. By illuminating the tissue surface with specific wavelengths (blue 415 nm and green 540 nm), both increasingly absorbed by haemoglobin, the vascular structures appear dark brown/green against a pink/white mucosal background. This contrast enhancement can therefore result in improved tumour detection rates compared to white light endoscopy. (18) NBI could be combined with OCT, where NBI could be used first to visualize or target a suspected lesion and OCT could assist in epithelial lesion differentiation by addressing grade and stage as shown by several studies. (19-21)