Three-Dimensional Parametric Imaging of Bladder by Single-Layered EIT Sensor With Simultaneous Position and Shape Constraints

In lower abdominal radiotherapy, the best time for radiotherapy, which is mainly related to the volume, location, and shape of the bladder, is identified empirically by experienced radiologists after the operation planning, where a monitoring method is still missing to protect healthy tissues from radiation damage as much as possible. In view of the difficulties in attaining the multiple 3-D parameters of the bladder by 3-D imaging with constrained space, this article proposes a monitoring method based on electrical impedance tomography (EIT) with a dedicated single-layered sensor, where a reconstruction algorithm with simultaneous position and shape constraints is proposed. To apply the constraints individually, a parametric shape representation method with undersampling and interpolation under spherical coordinates is devised to extract and compress the 3-D features of the bladder shape, and thus, a 3-D imaging framework is established with the ability to update the priors dynamically. The effectiveness of the proposed method is verified by simulation and ex vivo tank experiments. The results show that the proposed method can effectively reconstruct the 3-D parametric image of the bladder, where the structure similarities of reconstructed images against the bladder phantoms are above 0.81. This manifests that it has a great potential to be applied in the clinical practice of lower abdominal radiotherapy.