OCT-assisted control of catheter positioning in the urethra of the rabbit – A feasibility study

Abstract Background A fundamental precondition of local radiotherapy by means of 32 P-loaded urethral catheters is a precise position with respect to the target tissue. This feasibility study investigates optical coherence tomography (OCT)-assisted examination of the catheter position and its adherence to the tissue surface. Materials and methods OCT investigations were performed using an animal model (rabbit urethra, n =4). A radial scanning OCT probe located in the lumen of the catheter provided OCT images of the catheter structure as well as of the surrounding tissue. Descriptive evaluation of the OCT images gives information about the fitting, the structure of the catheter, as well as of the surrounding urethral tissue. The dimensions of catheter–tissue separation were determined. Results Radial OCT images provided clear cross-sections of the catheter. The layered structure of the surrounding urethral tissue could be identified and correlated to the histology. Distances between the catheter surface and the tissue could be evaluated indicating gaps of up to 0.4 mm and sector widths of up to 90°. Dosimetric calculations have shown that such changes may reduce the intended β-irradiation dose by 30% in the target tissue depth. Morphological changes (e.g. scar formation), related to wound healing processes after surgical incision, could be observed as well. Conclusion OCT-mediated tissue differentiation through OCT-wavelength transparent catheters shows the potential for identifying morphological changes. The fitting of the catheter to the urethral wall could be verified. Therefore, OCT techniques may improve the control of the radioactive catheter position resulting in an upgrade of dosimetric calculation for local 32 P-β-radiation low-dose brachytherapy.