Accurate Localization of In-Body Medical Implants Based on Spatial Sparsity

Abstract

Wearable and implantable wireless communication devices have in recent years gained increasing attention for medical diagnostics and therapeutics. In particular, wireless capsule endoscopy has become a popular method to visualize and diagnose the human gastrointestinal tract. Estimating the exact position of the capsule when each image is taken is a very critical issue in capsule endoscopy. Several approaches have been developed by researchers to estimate the capsule location. However, some unique challenges exist for in-body localization, such as the severe multipath issue caused by the boundaries of different organs, inconsistency of signal propagation velocity and path loss parameters inside the human body, and the regulatory restrictions on using high-bandwidth or high-power signals. In this paper, we propose a novel localization method based on spatial sparsity. We directly estimate the location of the capsule without going through the usual intermediate stage of first estimating time-of-arrival or received-signal strength, and then a second stage of estimating the location. We demonstrate the accuracy of the proposed method through extensive Monte Carlo simulations for radio frequency emission signals within the required power and bandwidth range. The results show that the proposed method is effective and accurate, even in massive multipath conditions.

Localization and Tracking of Implantable Biomedical Sensors

“…In addition to the technological challenges mentioned above, another essential point to take into account in localization system design for WBSs is the regulatory safety standards [4,57,58]. The band or power level of the signals to be used for biomedical sensor localization are upper-bounded by such standards, e.g., the Medical Implant Communication Service (MICS) standard asserts use of the 402–405 MHz frequency band for communication with medical implants [4,58].…”

“…The band or power level of the signals to be used for biomedical sensor localization are upper-bounded by such standards, e.g., the Medical Implant Communication Service (MICS) standard asserts use of the 402–405 MHz frequency band for communication with medical implants [4,58]. In order to decrease the interference among signals within the allowed band, the channel bandwidth is limited to 300 kHz.…”

Tracking systems for intracranial medical devices: A review

“…Nevertheless, a few works on narrow spectra have been published, as the representation of the effective depth of magnetic field penetration for half of the radio frequencies [10–500 MHz] (Figure ; Röschmann, ); the measurement of the refractive index of the skin epidermis and dermis for the visible spectrum [187–999 THz] (Ding, Lu, Wooden, Kragel, & Hu, ); or the energy absorption build‐up factor of different tissues for the very high frequencies [2–480 EHz] (Manohara, Hanagodimath, & Gerward, ). The head multitissue structure creates reflections at interfaces, which directly impact the localization measurement by creating fake positions (Figure ; Pourhomayoun, Jin, & Fowler, ). Tracking systems will be discussed by dividing them into three subfamilies with sufficient penetrability: radio, optical and very high frequencies (X‐ray and gamma ray).…”

Hardware Implementation of a RSS Localization Algorithm for Wireless Capsule Endoscopy

“…There exist many methods for the localization of wireless endoscopic capsules [2], [3], ranging from those based on measuring magnetic field strength, to various types of RF localization, to other miscellaneous proposed methods, such as magnetic resonance imaging (MRI), ultrasound, accelerometer or visual odometry, etc. We focus on RF localization since it involves reusing the electromagnetic signal radiated by the wireless capsule endoscope without the need for any additional equipment.…”