Maximizing Data Transmission Rate for Implantable Devices Over a Single Inductive Link: Methodological Review

Due to the constantly growing geriatric population and the projected increase of the prevalence of chronic diseases that are refractory to drugs, implantable medical devices (IMDs) such as neurostimulators, endoscopic capsules, artificial retinal prostheses, and brain-machine interfaces are being developed. According to many business forecast firms, the IMD market is expected to grow and they are subject to much research aiming to overcome the numerous challenges of their development. One of these challenges consists of designing a wireless power and data transmission system that has high power efficiency, high data rates, low power consumption, and high robustness against noise. This is in addition to minimal design and implementation complexity. This manuscript concerns a comprehensive survey of the latest techniques used to power up and communicate between an external base station and an IMD. Patient safety considerations related to biological, physical, electromagnetic, and electromagnetic interference concerns for wireless IMDs are also explored. The simultaneous powering and data communication techniques using a single inductive link for both power transfer and bidirectional data communication, including the various data modulation/demodulation techniques, are also reviewed. This review will hopefully contribute to the persistent efforts to implement compact reliable IMDs while lowering their cost and upsurging their benefits.

Capsule endoscopy: The road ahead

Since its introduction into clinical practice 15 years ago, capsule endoscopy (CE) has become the first-line investigation procedure in some small bowel pathologies, and more recently, dedicated esophageal and colon CE have expanded the fields of application to include the upper and lower gastrointestinal disorders. During this time, CE has become increasingly popular among gastroenterologists, with more than 2 million capsule examinations performed worldwide, and nearly 3000 PubMed-listed studies on its different aspects published. This huge interest in CE may be explained by its non-invasive nature, patient comfort, safety, and access to anatomical regions unattainable via conventional endoscopy. However, CE has several limitations which impede its wider clinical applications, including the lack of therapeutic capabilities, inability to obtain biopsies and control its locomotion. Several research groups are currently working to overcome these limitations, while novel devices able to control capsule movement, obtain high quality images, insufflate the gut lumen, perform chromoendoscopy, biopsy of suspect lesions, or even deliver targeted drugs directly to specific sites are under development. Overlooking current limitations, especially as some of them have already been successfully surmounted, and based on the tremendous progress in technology, it is expected that, by the end of next 15 years, CE able to perform both diagnostic and therapeutic procedures will remain the major form of digestive endoscopy. This review summarizes the literature that prognosticates about the future developments of CE.

Wireless endoscopy in 2020: Will it still be a capsule?

Currently, the major problem of all existing commercial capsule devices is the lack of control of movement. In the future, with an interface application, the clinician will be able to stop and direct the device into points of interest for detailed inspection/diagnosis, and therapy delivery. This editorial presents current commercially-available new designs, European projects and delivery capsule and gives an overview of the progress required and progress that will be achieved -according to the opinion of the authors- in the next 5 year leading to 2020.

Colon capsule endoscopy: Current status and future directions

Colon capsule endoscopy (CCE; PillCam Colon; Given Imaging; Yoqneam, Israel) is a minimally invasive wireless technique for the visualization of the colon. With the recent introduction of the second generation colon capsule the diagnostic accuracy of CCE for polyp detection has significantly improved and preliminary data suggest it may be useful to monitor mucosal inflammation in patients with inflammatory bowel disease. Limitations include the inability to take biopsies and the procedural costs. However, given the potentially higher acceptance within an average risk colorectal cancer (CRC) screening population, its usefulness as a screening tool with regard to CRC prevention should be further evaluated.

Current application situation of gastrointestinal endoscopy in China

AIM: To study the current application situation of gastrointestinal (GI) endoscopy in mainland China.

METHODS: From 12 August, 2011 to 15 February, 2012, draft questionnaires were sent by e-mail to 289 hospital-based GI endoscopy units, including units with three levels (provincial, prefecture and county level) in mainland China. All the surveyed GI endoscopy units were state-owned and hospital-based. Proportions were compared using χ² tests. Comparisons between groups were performed using the Mann-Whitney U test. A probability of P < 0.05 was considered to represent a statistically significant difference.

RESULTS: Based on satisfactory replies, 169/279 (60.6%) of units were enrolled in the survey, which covered 28 provinces (90.3%, 28/31) in mainland China. Compared with published survey data, the number of GI endoscopes per unit has increased by nearly three times (from 2.9 to 9.3) in the past decade. About 33 of 169 (19.5%) endoscopy units possessed an X-ray machine, which was mainly owned by provincial endoscopy units (43.2%, 19/44). Video capsule endoscopes, which were almost unavailable ten years ago, were owned by 20.7% (35/169) of GI endoscopy units. Endoscopic submucosal dissection could be performed by 36.4% (19/44) of the provincial units, which was significantly higher than the prefecture level (9.9%, P < 0.01) and county level (0.0%, P < 0.01) units, respectively.

CONCLUSION: Rapid development in GI endoscopy has been made in mainland China, and major diagnostic endoscopes and therapeutic endoscopy procedures are predominantly used in large endoscopy units.

10 years of capsule endoscopy: an update

Capsule endoscopy (CE) has evolved in a few short years to become a first-line, noninvasive diagnostic technique for the small bowel. CE is now being utilized worldwide to assess patients for obscure gastrointestinal bleeding, possible Crohn's disease, celiac disease and small bowel tumors. The device is now used in tandem with balloon enteroscopy to direct therapeutic interventions. Alterations and improvements in CE have also led to the evaluation of both the esophagus and colon. It can be anticipated that in the near future pan CE of the entire GI tract will be performed, as well as possible tissue acquisition, drug delivery and therapeutic interventions.

Small bowel capsule endoscopy in 2007: indications, risks and limitations

Capsule endoscopy has revoluzionized the study of the small bowel by providing a reliable method to evaluate, endoscopically, the entire small bowel. In the last six years several papers have been published exploring the possible role of this examination in different clinical conditions. At the present time capsule endoscopy is generally recommended as a third examination, after negative bidirectional endoscopy, in patients with obscure gastrointestinal bleeding. A growing body of evidence suggests also an important role for this examination in other clinical conditions such as Crohn's disease, celiac disease, small bowel polyposis syndromes or small bowel tumors. The main complication of this examination is the retention of the device at the site of a previously unknown small bowel stricture. However there are also some other open issues mainly due to technical limitations of this tool (which is not driven from remote control, is unable to take biopsies, to insufflate air, to suck fluids or debris and sometimes to correctly size and locate lesions). The recently developed double balloon enteroscope, owing to its capability to explore a large part of the small bowel and to take targeted biopsies, although being invasive and time consuming, can overcome some limitations of capsule endoscopy. At the present time, in the majority of clinical conditions (i.e. obscure GI bleeding), the winning strategy seems to be to couple these two techniques to explore the small bowel in a painless, safe and complete way (with capsule endoscopy) and to define and treat the lesions identified (with double balloon enteroscopy).

Wireless capsule endoscopy: from diagnostic devices to multipurpose robotic systems

In the recent past, the introduction of miniaturised image sensors with low power consumption, based on complementary metal oxide semiconductor (CMOS) technology, has allowed the realisation of an ingestible wireless capsule for the visualisation of the small intestine mucosa. The device has received approval from Food and Drug Administration and has gained momentum since it has been more successful than traditional techniques in the diagnosis of small intestine disorders. In 2004 an esophagus specific capsule was launched, while a solution for colon is still under development. However, present solutions suffer from several limitations: they move passively by exploiting peristalsis, are not able to stop intentionally for a prolonged diagnosis, they receive power from an internal battery with short length, and their usage is restricted to one organ, either small bowel or esophagus. However the steady progresses in many branches of engineering, including microelectromechanical systems (MEMS), are envisaged to affect the performances of capsular endoscopy. The near future foreshadows capsules able to pass actively through the whole gastrointestinal tract, to retrieve views from all organs and to perform drug delivery and tissue sampling. In the long term, the advent of robotics could lead to autonomous medical platforms, equipped with the most advanced solutions in terms of MEMS for therapy and diagnosis of the digestive tract. In this review, we discuss the state of the art of wireless capsule endoscopy (WCE): after a description on the current status, we present the most promising solutions.