Medical science in the 19th and 20th centuries was dominated by breakthroughs leading to new diagnostic techniques and surgical interventions. This revolution was driven in part by a better understanding of human anatomy and the engineering of new medical instrumentation. The endoscope was one of the first new medical instruments playing a major role in this revolution. The endoscope enabled novel minimally invasive surgical procedures that improved both the efficacy of the treatment and the outcome for the patient.
History of Endoscopy
The German-Italian physician Philipp Bozzini (1773–1809) is generally credited with the invention of modern endoscopy. His “Lichtleiter,” introduced in 1806 and considered an early example of the endoscope, featured angled mirrors that could be positioned to examine internal body structures and hollow cavities. Less than a decade later, French urologist Antonin Jean Désormeaux (1815–1894) enhanced Bozzini’s invention, permitting physicians to locate the source of disease in patients without having to rely on deductive reasoning or “blind” biopsies.
Subsequent developments by Maximilian Nitze (1848–1906), who created a device with prisms and lenses allowing transurethral visualization of the bladder with a relatively wide field of view, and the addition of a moving “cutting loop” by Maximilian Stern (1877–1946), making transurethral resection possible, further augmented the capabilities of the endoscope.
The improvement of the endoscope did not end there. In the 1950s, physicist Harold Hopkins (1918-1994) modernized the endoscope with a series of cylindrical, self-aligning lenses called rod lenses. This approach solved the physical limitations of the endoscope, allowing surgical tools as well as the illumination to be bundled with the imaging system. Taking this a step further, in 1957, Basil Hirschowitz and Larry Curtiss created the first fiber-optic endoscope, which made it possible to generate clinically useful “moving” images (video), aiding diagnostics and treatment.
The Digital Era
In 1979, at the dawn of the digital era, the invention of the charge-coupled device (CCD) by Willard Boyle and George Smith significantly transformed the design of the endoscope once again. While it was initially developed as a memory device, the ability of the CCD to transfer electric charge, as well as its linearity of response, high sensitivity and instant image production, made it possible to capture high-quality digital images.
The New Era: CMOS Image Sensors
Although complementary metal oxide semiconductor or CMOS technology has been around nearly as long as the CCD, the complex fabrication process of CMOS made CCD, for a while, the dominant sensor technology. However, lithographic developments in the 1990s renewed interest in CMOS. Today, CMOS sensor technology has become mainstream in diverse imaging applications like mobile phones, notebooks, security, automotive, and medical endoscopy.
CMOS image sensors offer high-quality images at faster frame rates and lower fabrication costs due to the reuse of mainstream logic and memory device fabrication. Other advantages of CMOS over CCD include on-chip analog-to-digital conversion, higher noise immunity, on-chip signal processing functions and significantly lower power consumption. CMOS imagers are also immune to magnetic fields generated by medical radiofrequency equipment, eliminating the requirement for shielding and thus simplifying endoscope design.
Advances in CMOS fabrication have led to additional benefits, including the creation of ultra-small imagers that can fit into endoscopes with an outer diameter as small as 1 mm, enabling direct visualization and more detailed examinations of smaller parts of the anatomy. Today, chip-on-tip endoscopes using CMOS technology, combined with illumination fibers or a light-emitting diode (LED) light source, have transformed the possibilities of endoscopic imaging and surgical procedures.
Many commentators see socioeconomic trends as among the main drivers for the growth of endoscopes and catheters. Key trends include an aging population, the increasing prevalence/incidence of diseases that require endoscopic procedures, rising healthcare costs, a more favorable insurance reimbursement scenario for minimally invasive and non-invasive procedures, the increasing number of hospitals and their growing investment in endoscopy and a rising middle class in emerging countries. Legal and commercial issues as well as technological advances are other notable drivers for this exponential growth.
Sterilization and Hygiene
Designed for repeated use, traditional endoscopes require elaborate cleaning and sterilization after each use to avoid cross-contamination. Cross-contamination due to incomplete sterilization is, according to the ECRI Institute (https://www.ecri.org), a nonprofit organization dedicated to improving patient care, one of the “Top 10 Health Technology Hazards.” However, endoscopes employing disposable single-use technology can eliminate many of the disadvantages associated with reusable endoscopes, including the high cost of repairs, pre-procedure testing, and downtime for cleaning and maintenance. The lower per-use cost also drive up demand.
Small, Smaller, Smallest
The transition to ever-smaller image sensor technologies has created a burgeoning market, in part driven by the replacement of conventional open surgeries with minimally invasive procedures. Advanced technology offered by OmniVision Technologies, a leading CMOS sensor provider to global medical markets, has resulted in ultra-small medical image sensors supporting a range of minimally invasive, cost-effective and single-use endoscopic and catheter applications that previously were either done “blind,” using indirect visualization, or were simply not possible to do at all. Endoscopes and catheters featuring these ultra-small imagers are now used in neurology, ophthalmology, cardiology, spinal surgery, urology, and women’s health applications.
The latest medical CMOS image sensors can offer an incredible range of performance capabilities, including: high resolution and frame rates, excellent low-light sensitivity, low noise, low color crosstalk, high sharpness, and high dynamic range. These imagers also have a small number of pins, enabling easy integration, low power consumption, and long drive distances down the endoscope.
Compact, cost-effective wafer level modules can be particularly suitable for cost-sensitive single-use endoscope, catheter and guidewire markets. These modules can provide excellent image quality and optics specially designed for the target procedures. They can also be designed for sterilization and bio-compatibility.
In light of past trends in endoscope development, many commentators expect to see creative use of technologies borrowed from a range of disciplines — biomedical sciences and engineering — help boost the development of novel endoscopic techniques going forward. This in turn could greatly enhance physicians’ ability to diagnose and treat pathologies, improve the quality of care, and reduce patient morbidity while improving recovery and overall health.
Disclaimer: The views expressed herein are solely those of the author and do not necessarily reflect the views of any company or other organization.