Development of a Model to Simulate Radiation Induced Vaginal Stenosis
Radiation induced vaginal stenosis (VS) is characterized by the narrowing or shortening of the vaginal canal following radiotherapy or brachytherapy for the treatment of gynecological malignancies. One of the most prominent gynecological cancers in women is cervical cancer, which has a fairly high survival rate but can have detrimental impacts on the quality of life of those who survive it, mainly due to tissue injury caused by radiation. The current standard of care for the prevention of vaginal stenosis involves the use of vaginal dilators, which usually consist of stiff plastic or silicone rods graded in different sizes to mechanically expand the vaginal canal. Such course of treatment lacks patient adherence and cannot be objectively assessed, as it does not provide monitoring of the progression of the VS syndrome or of dilator use. In order to address this medical need, a vaginal dilation system consisting of an expandable vaginal dilator that can be monitored through pressure measurements was developed. In order to characterize the proposed expandable vaginal dilator prior to its clinical use, a model was developed to simulate different severities of vaginal stenosis, taking into consideration changes in vaginal morphological properties, such as the increase in deposition of stiffer collagen fibers. An established clinical grading criteria for vaginal stenosis was used to modify vaginal dimensions according to a set baseline, which was determined by average vaginal dimensions reported in literature. A combination of 3D printed TPU infill and Ecoflex 30 silicone were used to manufacture graded vaginal phantoms and characterize the pressure of the proposed vaginal dilations in a variety of VS scenarios. A variation in diameter, showcasing different severities of VS according to vaginal dimension, as well as a variation in TPU infill density were explored in relation to dilator pressure. Furthermore, the mechanical properties of porcine vaginal tissue were compared to the mechanical properties of the material used to manufacture the phantom model. It was found that while the mechanical properties of vaginal tissue and the composite material used for the phantoms differed, the dilator pressure recorded in both vaginal tissue and the developed vaginal phantoms showed many similarities and were able to highlight different trends (i.e. increasing pressure with decreasing diameter or increasing infill density) depending on the sizing of the vaginal dilator. Thus, showing that the developed model can be used to characterized the designed expandable dilators, although future considerations should be given to improve both the phantom model and iterate on the dilation system.