Bladder Volume Monitoring Using Electrical Impedance Tomography With Simultaneous Multi-Tone Tissue Stimulation and DFT-Based Impedance Calculation Inside an FPGA

• Published in: IEEE transactions on biomedical circuits and systems Vol. 14; no. 4; pp. 775 - 786
• Main Authors: Rosa, Bruno M. G., Yang, Guang Z.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.08.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adult; Biomedical measurement; Bladder; Bladder volume; Catheterization; Computer applications; Electric Impedance; Electrical impedance; electrical impedance tomography (EIT); Electrodes; embedded electronics; Equipment Design; Experimentation; field programmable gate array (FPGA); Field programmable gate arrays; finite integration technique; Fourier Analysis; Fourier transforms; Gauss-Newton method; Humans; Impedance; Impedance measurement; Inverse problems; Male; Mathematical models; Newton methods; Phantoms, Imaging; Regularization; Signal Processing, Computer-Assisted - instrumentation; Tissues; Tomography; Tomography - instrumentation; Urinary bladder; Urinary Bladder - anatomy & histology; Urinary Bladder - diagnostic imaging; Urinary Bladder - physiology; Volume measurement
• ISSN: 1932-4545; 1940-9990; 1940-9990
• DOI: 10.1109/TBCAS.2020.3008831

In this article, a novel method for measuring the volume of the urinary bladder non-invasively is presented that relies on the principles dictated by Electrical Impedance Tomography (EIT). The electronic prototype responsible for injecting innocuous electrical currents to the lower abdominal region and measuring the developed voltage levels is fully described, as well as the computational models for resolution of the so-called Forward and Inverse Problems in Imaging. The simultaneous multi-tone injection of current provided by a high performance Field Programmable Gate Array (FPGA), combined with impedance estimation by the Discrete Fourier Transform (DFT) constitutes a novelty in Urodynamics with potential to monitor continuously the intravesical volume of patients in a much faster and comfortable way than traditional transurethral catheterization methods. The resolution of the Inverse Problem is performed by the Gauss-Newton method with Laplacian regularization, allowing to obtain a sectional representation of the volume of urine encompassed by the bladder and surrounding body tissues. Experimentation has been carried out with synthetic phantoms and human subjects with results showing a good correlation between the levels of abdominal admittivity acquired by the EIT system and the volume of ingested water.