Where Next for The Endoscope?

Abstract and Introduction

Abstract

The concept of examining the body's interior and its organs dates back to ancient times. The roots of modern endoscopy lie in early nineteenth century Europe, and the intervening centuries have seen a steady evolution of devices and techniques. Nowadays, a wide variety of urinary tract disorders are successfully managed in a minimally invasive manner thanks to the endoscope and related technologies. Distal-sensor, 'digital', endoscopes have the potential to revolutionize the field, and change the way in which we use and think about endoscopy. Virtual endoscopy, capsule endoscopy, and a range of other techniques derived from physics and molecular biology all promise great improvements in visualization of the urinary tract and other urologic structures. Ultimately, the continued improvement of these minimally invasive technologies will enhance the quality of care that we can offer our patients.

Introduction

Endourologic treatment has advanced greatly in recent years, driven by technologic improvements in endoscopic visualization of urological structures and the development of ever-smaller endoscopes. The vast majority of urologic surgery and treatment, which once relied on invasive techniques and large open incisions, can currently be performed using minimally invasive techniques based on endoscopy. Throughout history, the field of urology has been a leader in surgical innovation and the application of minimally invasive techniques. Today, it continues to lead the cutting-edge application of endoscopy. In this Perspectives article, we review the evolution of contemporary endoscopy, highlight the most recent additions to the urologist's endoscopic armamentarium, and speculate about the bright future of urologic endoscopy.

Table 1. Urologic diseases commonly managed by endoscopic technique
Organ	Benign	Malignant
Kidney	Stone Stricture or obstruction Hematuria	Selected superficial urothelial tumors
Ureter	Stone Stricture	Selected superficial urothelial tumors
Bladder	Stone Selected diverticula	Superficial urothelial tumors
Prostate	Hyperplasia	Obstruction due to prostate cancer
Urethra	Stone Stricture	Superficial neoplasms

Box 1. CCD and CMOS chips in endoscopy
Digital image capturing is possible through sensor array technologies such as those based on CCD and CMOS chips. Digital sensors are composed of millions of photodiodes, which convert photons into electric current that is later transformed into voltage, amplified and converted to a digital form.
CCD chips have a photoactive region (an epitaxial layer of silicon), and a transmission region. An image is projected through a lens onto the photoactive region, and each capacitor accumulates an electric charge proportional to the light intensity at that location. A control circuit then causes each photoactive region to transfer its contents to its neighbor. This circuit operates as a shift register, transferring the electric charge sequentially, row by row, column by column, to a common output structure that converts the charge to a voltage.^[39]
The color accuracy of the CCD camera allows enhanced visualization of reproduced images.^[40] Other advantages of the CCD camera are the improved resolution and quality of the images achieved when three chips are present (one each for red, blue, and green light).^[41] Most small endoscopes use a single chip in which these color distinctions are created by filters.
CMOS chips, likewise, are capable of electronic registration of images projected onto their surface through the lens of a camera, and also provide image capture to a grid of pixels formed by photoelectric elements. The resultant electric charges are 'read' by a sensor, and a process of analog to digital signal conversion is required to produce images that can be stored. in a CMOS sensor, each pixel acts as its own independent amplifier of the image signal, which limits noise as the charge-to-voltage conversion takes place within each pixel. On both types of chips, the information is transferred to a controller box for image presentation or storage.
Compared with CCD chips, CMOS technology offers improved integration (more functions on the chip), lower energy consumption and less heat production. Additionally, CMOS technology requires fewer electronic components, which allows such chips to be smaller and more compact. However, to date, the advantages of CMOS chips often come at the expense of image quality and device cost.^[42] CMOS cameras still generally require companion chips to optimize image quality, which increases cost and power consumption.
Technological developments have enabled the production of a CMOS sensor with high energy efficiency, high spatial resolution, high speed, low power consumption and low cost.^[43] in the future, CMOS camera endoscopes might reduce device costs and facilitate the spread of distal sensor endoscopy.
Abbreviations: CCD, charge-coupled device; CMOS, complementary metal oxide semiconductor.

Box 1. CCD and CMOS chips in endoscopy

Digital image capturing is possible through sensor array technologies such as those based on CCD and CMOS chips. Digital sensors are composed of millions of photodiodes, which convert photons into electric current that is later transformed into voltage, amplified and converted to a digital form.

CCD chips have a photoactive region (an epitaxial layer of silicon), and a transmission region. An image is projected through a lens onto the photoactive region, and each capacitor accumulates an electric charge proportional to the light intensity at that location. A control circuit then causes each photoactive region to transfer its contents to its neighbor. This circuit operates as a shift register, transferring the electric charge sequentially, row by row, column by column, to a common output structure that converts the charge to a voltage.^[39]

The color accuracy of the CCD camera allows enhanced visualization of reproduced images.^[40] Other advantages of the CCD camera are the improved resolution and quality of the images achieved when three chips are present (one each for red, blue, and green light).^[41] Most small endoscopes use a single chip in which these color distinctions are created by filters.

CMOS chips, likewise, are capable of electronic registration of images projected onto their surface through the lens of a camera, and also provide image capture to a grid of pixels formed by photoelectric elements. The resultant electric charges are 'read' by a sensor, and a process of analog to digital signal conversion is required to produce images that can be stored. in a CMOS sensor, each pixel acts as its own independent amplifier of the image signal, which limits noise as the charge-to-voltage conversion takes place within each pixel. On both types of chips, the information is transferred to a controller box for image presentation or storage.

Compared with CCD chips, CMOS technology offers improved integration (more functions on the chip), lower energy consumption and less heat production. Additionally, CMOS technology requires fewer electronic components, which allows such chips to be smaller and more compact. However, to date, the advantages of CMOS chips often come at the expense of image quality and device cost.^[42] CMOS cameras still generally require companion chips to optimize image quality, which increases cost and power consumption.

Technological developments have enabled the production of a CMOS sensor with high energy efficiency, high spatial resolution, high speed, low power consumption and low cost.^[43] in the future, CMOS camera endoscopes might reduce device costs and facilitate the spread of distal sensor endoscopy.

Abbreviations: CCD, charge-coupled device; CMOS, complementary metal oxide semiconductor.