Overactive bladder (OAB) is defined by the International Continence Society as urinary frequency and urgency, with or without urge urinary incontinence. The burden of OAB on the American public is immense in both human and financial terms. Despite this burden, there is a lack of effective diagnostic and treatment modalities for OAB. Other than two-dimensional video urodynamics, which has remained relatively unchanged for decades, there is a lack of diagnostic modalities that will allow investigators to characterize subtypes of OAB and measure the effects of treatment on bladder physiology. Newer imaging techniques are desperately needed to help guide treatment and predict and improve outcomes of different treatment modalities. Intravesical botulinum toxin is a minimally invasive treatment for OAB refractory to medical therapy. Despite the widespread use of intravesical botulinum toxin injection for OAB refractory to medical therapy, to date the optimal placement of the drug has not been determined. Typically ten injections are given, either dispersed evenly across the bladder or in two rows of five injections. However, it remains unknown which injection method will optimize outcomes and reduce the risk of urinary retention after Botox®. This lack of knowledge is a direct result of the fact that there has been no mechanism to study the effect of Botox® on bladder filling and emptying in a three-dimensional fashion. CineMRI-UDS will provide this mechanism, and has the potential to significantly improve care and urologic education by enhancing the understanding of bladder physiology.