Bladder Boundary Estimation by Gravitational Search Algorithm Using Electrical Impedance Tomography

The noninvasive method for monitoring urine collection in the bladder is highly recommended for paraplegia patients. These patients are unable to discharge urine at the right time due to a weaker sensation for bladder volume. If the urine is not discharged in time, then the bladder size will increase and affect the neighboring organs and tissues. Electrical impedance tomography (EIT) is a noninvasive alternative method that can be used for bladder status monitoring. Size estimation of the bladder with EIT can clarify the bladder status. The bladder is a nonuniform structure with complex shape; therefore, higher order Fourier series is needed to represent the true shape. In estimating the higher order Fourier coefficients, the performance of a conventional modified Newton-Raphson (mNR) algorithm does not give the desired performance. In this article, the gravitational search algorithm (GSA) that is known for solving optimization problems in high-dimensional search space is proposed for the shape estimation of the bladder. GSA is a global optimization algorithm that has fast convergence and does not require the computation of Jacobian. Numerical experiments and phantom studies are performed to estimate the bladder size, and the results showed good performance.