Brief History of Medical Imaging

Medical imaging has played a very significant role in medicine for over the last one hundred years. It is one of the most important diagnostic tools available to doctors and has revolutionized the medical diagnosis of patients. The use of medical imaging has enabled doctors to see inside a patient without having to cut them open. Medical imaging, especially X-ray examinations and sonography which is also known to some as ultrasound, is essential in an everyday medical setting. Preventive medicine as well as healing medicine depends on the proper diagnosis and treatment by physicians, and the use of diagnostic imaging can help evaluate the course of a disease, as well as assess and document the disease in response to the treatment.

Medical imaging has rapidly expanded from the first medical image discovered by Professor Wilhelm Conrad Roentgen. During a late night experiment in November of 1895, Roentgen, a physics professor from Germany, was examining Crookes tubes. He noticed that some light had managed to pass through a tube that he had wrapped in thin black cardboard, reflecting on the wall of his dark laboratory. Upon further investigation he found that the light could also be passed through paper, books, and eventually through human flesh. Unintentionally, he had stumbled upon a very important discovery that led to the discovery of what we now call an X-ray.
One of the very first x-rays was one that Roentgen made was of his wife’s hand. The flesh of the hand looked like a shadow, and around the finger bone the wedding band was visible and solid. This was the first time that bone had been viewed through the skin. Within a few months of the discovery, x-ray machines were produced to be used in the medical field. The x-ray machine was the first tool that allowed the internal anatomy to be made observable without any surgical means. Roentgen’s discovery earned him the first Nobel Prize in physics in 1901.

During the first fifty years of diagnostic imaging, the most common examination involved creating an image by focusing x-rays through the body part of interest and directly onto a single piece of film inside a special cassette. In the earliest days, a head x-ray could entail up to 11 minutes of exposure time. Now x-rays images are made in milliseconds and the x-ray uses is as little as 2% of what it used to take for that 11 minute head exam 100 years ago. Also, the quality of the image has drastically improved from the first x-rays.

The next advance in medical imaging involved use of fluorescent screens and special glasses so that a physician could see x-ray images in real time. This caused the doctor to gaze directly into the x-ray beam, which produced excessive exposure to radiation. So in 1946, George Schoenander, developed a film cassette changer that allowed a sequence of cassettes to be visible at a movie frame rate of 1.5 cassettes per second. By 1953, this technique had been enhanced to allow frame rates up to 6 frames per second by using a special cut film changer.

Another important medical imaging procedure, ultrasound, can be traced back in history to Leonardo da Vinci, who first recorded experiments listening to sound transmitted through water by placing a tube into the sea to evaluate what he could hear. That experiment may have been the launch of sonar research, which is believed to be the precursor to 20th century medical ultrasound. In 1794, Lazzaro Spallanzani, an Italian biologist, theorized about high frequency ultrasound while studying the navigational ability of bats. Throughout the 1800s, physicists around the world conducted investigations into sound that would eventually lay the groundwork that medical sonography was built on.

It wasn’t until the 1960's that the idea of sonar was applied to diagnostic imaging. This procedure involves placing a small device called a transducer, against the skin of the patient near the region of concern. This transducer produces a stream of inaudible, high frequency sound waves that penetrate into the body and bounce off the organs inside. The return of the sound wave to the transducer is just the opposite route. The transducer detects sound waves as they bounce off or echo back from the internal organs. The return sound wave vibrates the transducer, and then the transducer turns the vibrations into electrical pulses that travel to the ultrasonic scanner where they are processed and converted into a digital image, best known as an ultrasound. In physics, the term "ultrasound" relates to all sound waves with a frequency above the audible range of normal human hearing, which is about 20 kHz. The frequencies used in diagnostic ultrasound are typically between 2 and 18 MHz. Unlike other medical imaging procedures such as x-rays, diagnostic ultrasound is considered safe, effective, and easy imaging capable of providing information about most parts of the body in a quick and cost effective fashion.

Medical imaging today is broadly used in clinical diagnosis to help guide therapeutic treatment and surgical intervention and to monitor the course of disease progression, and treatment. A wide array of imaging procedures is currently available to the medical community to provide patients with information about their condition that helps them make informative decisions about treatment for their condition. Research shows that the use of medical imaging may lead to significant reduction in healthcare costs by increasing the speed of diagnosis, avoiding the need for expensive treatments and surgical procedures, and reducing death rate through early screening programs.

Bibliography

http://en.wikipedia.org/wiki/Medical_ultrasonography http://www.imaginis.com/faq/history-of-medical-diagnosis-and-diagnostic-imaging http://www.bl.uk/learning/artimages/bodies/xray/roentgen.html
http://www.who.int/diagnostic_imaging/en/