As far back as 2500 bc, surgical ‘operations’ were depicted on the tombs of the pharaohs, so that the partnership between medicine and art can be said to be at least 4, 500 years old. The teaching and study of human anatomy has always required illustration. The Flemish anatomist Andreas Vesalius (1514-64), in questioning the infallibility of Galen, elevated the science of human anatomy through direct observation of dissections of the human body. Vesalius sketched the vascular system and the skeleton, and encouraged professional artists to portray the human body. Such eminent artists as Leonardo da Vinci, Michelangelo, Raphael, and Titian joined with physicians to observe and study dissections. Vesalius eventually published his masterpiece De Humani Corporis Fabrica in 1543. It was both a great medical book and a landmark in the history of illustration and printing.
Illustrating the human body in health and disease thus came to be important for teaching and research, and for patient management. Anatomical painting and drawing reached great heights of technical and observational skill. To this day some of the most detailed and accurate drawings of the peripheral vasculature and nerves are to be found in French texts dating from the second half of the 19th century.
The invention of photography
Methods of illustration changed with the invention of photography, which proved to be a turning point not only in medicine but also in scientific research and worldwide visual communication generally. At one stage stereoscopy also became popular, although three-dimensionality is mostly of little intrinsic value for medical illustration.
The impact of photography was profound for medical illustration. The medium's strength lies in its ability to record accurately, rapidly, repeatably, and without excessive cost. It has been argued that the arrival of photography reduced the importance of more traditional medical illustration skills. However, even up to the 1970s (before the advent of reliable high-quality miniaturized camera systems), medical painting was able to be more selective and discriminatory (in terms of colour, conformation, and texture) than photography, and this was particularly so in ophthalmology and endoscopy. Nowadays we are less concerned with the method of production of a picture or image than with its fitness for its purpose.
Cinephotography has played an important part in medicine and physiology; one of the most spectacular examples of its early use was by Eadweard Muybridge in 1901, whose rapid series of single camera exposures shed much light on the nature of human and animal locomotion. The technique was said to have been applied to the recording of the exposed heart of a dog by Reichart in 1887. This may well have been the earliest medical motion picture.
One of the pioneers of medical photography was Frederick T. D. Glendening, a staff photographer at St Bartholomew's Hospital, London, c. 1892-4. He worked in the outpatients department, and his clinical photographs became important for analysis and diagnosis of disease on the surface of the body. Besides its important role in diagnosis and management, photography permitted the circulation of visual records vital to the teaching of medicine. Glendening's work is preserved in the Royal Photographic Society's collection (housed at the National Museum for Photography, Film, and Television in Bradford, England). His work covers an extensive range of physical disorders, including curvature of the spine, clubfoot, smallpox, and the effects of alcoholism.
Specialist systems
Endoscopy. As early as the 1880s there had been much interest in recording images of the interior of the body obtained using endoscopes. Dry photographic plates, replacing the old wet- collodion techniques, simplified endoscopic procedures. In 1884 Brainerd was able to photograph the larynx by reflected sunlight, and in 1894 Nitze produced flash photographs through a cystoscope. Nowadays, ‘endophotographs’, both still and moving, are of high quality. Modern endoscopes are very sophisticated instruments able to incorporate lasers and guide wires etc., to enable procedures to be carried out during an endoscopic examination.
Ophthalmology. Medical photographers often had the task of recording the external condition of the eyes and face, and ophthalmic photography can be considered as an early offshoot of mainstream medical photography. Cinephotography had a special place in the teaching of ophthalmology, to make available to a wide audience procedures that otherwise could be seen only by the surgeon. Slit lamp cameras for taking what amount to ‘optical sections’ of the living eye, and fundus cameras able to photograph the retina, are examples of techniques in ophthalmology that extend the normal scope of medical photography.
X-ray systems. The discovery in 1895 by Röntgen of X-rays employed photography as the best way to retain a permanent record of X-ray images. Today, X-ray systems have become very sophisticated, with computerized tomography (CT) scans able to image sections through the body; and to store large numbers of them in such a way that the data can be called up to produce images of any desired cross-section of the part recorded. A particularly spectacular development in X-ray technology has been in cardiac angiography, the visualization of blood vessels. Real-time X-ray equipment with image enhancement enables the cardiologist to view the heart after contrast medium has been introduced into the coronary arteries to determine any blocked or seriously narrowed vessels. Cardiac catheters are also used for the insertion of stents to hold vessels open mechanically, and for the ‘ballooning’ of vessels to allow more blood to flow through. It is also possible mechanically to ream out vessels that have become blocked. All of this can be visualized by the surgeon (and indeed the patient) with minimal invasiveness, using CCTV, and photographed at each stage.
Outside the visible spectrum
Beyond the violet, at the short wave end of the spectrum, are ultraviolet (UV) and X-radiation and beyond the red, at the long wave end, infrared (IR). Medical photography was quick to exploit these wavelengths outside the area of visible light.
UV. Energetic UV radiation waves make many substances fluoresce, that is, give off visible light, usually blue or greenish yellow. UV fluorescence photography is used in dentistry to record the presence of artificial teeth and is useful in recording dermatological conditions such as psoriasis, and fungal infections of the skin, such as ringworm.
IR. Silver halide emulsions sensitive to IR wavelengths are also useful in medical photography. Most of the IR radiation is reflected from the skin surface. Of the remainder, some is scattered and some absorbed by subcutaneous vessels. Infrared photography can thus be used to determine and record peripheral vascular patterns in venous thrombosis, varicose veins, and varicose ulcers.
The development of IR technology underwent a dramatic change at the end of the 1960s when IR-sensitive military scanning systems became available for medical work. Since that time scanners and the electronic images they produce have become more reliable, and can be accurately calibrated in terms of temperature in the scene being scanned. The use of thermal imaging systems has been a great success in industrial applications such as process control, preventive maintenance, energy conservation, etc. These scanners operate within two separate wavebands, the shorter about 2-6 microns and the longer 10-14 microns, the latter corresponding to human body temperature. The IR radiation from the human body is sufficient to produce accurate ‘maps’ of the skin surface temperature. In medicine and physiology thermal imaging finds application in a wide range of conditions where temperature can be related to subcutaneous blood flow, and to its neurological control. Rheumatology, dermatology, diabetic neuropathy, pain syndromes, and genetic inherited diseases are just a few of the areas where research has identified an important role for thermal imaging in clinical diagnosis and management.
Digital imaging
The effect of digital techniques on photography and related imaging has been profound. It is no longer necessary to use film to record and store images. Equally important, digital analysis methods can enhance and manipulate images to produce more information than ever before. Whereas medical imaging has traditionally dealt with visible light, and with some UV, IR, and X-ray images, nowadays it is possible for CT and magnetic resonance imaging (MRI) scans together with ultrasound to be combined with digital visual techniques in spectacular ways. For example, CT and MRI scans can look through the human body and produce slices that are similar to the individual pages of a book. (MRI is a more complicated type of tomography that produces images of soft tissues rather than hard ones such as bone.) Perhaps one of the most notable projects is the Visible Human Dataset, a large atlas of digital images of the human body. When complete, it will consist of about 20, 000 images from horizontal sections of a complete male and female cadaver. The male data set consists of axial MRI images of the head and neck taken at 4 mm intervals and longitudinal sections of the rest of the body also at 4 mm intervals. The CT data consist of axial CT scans of the entire body taken at 1 mm intervals at a resolution of 512 × 512 pixels, each pixel being made up of twelve bits of grey tone that can be rendered in colour. The anatomical cross-sections are also at 1 mm intervals and coincide with the CT axial images. There are 1, 871 cross-sections for each mode, CT and anatomy, obtained from the male cadaver. The data set from the female cadaver will, when complete, have the same characteristics as that from the male cadaver, with one exception. The axial anatomical images will be obtained at 0.33 mm intervals instead of 1 mm intervals. This will result in over 5, 000 anatomical images. The data set is expected to be about 40 gigabytes in size—a truly monumental task.
Such digital images can be deconstructed and reconstructed to give views from any angle. A further advance is that images from several imaging methods taken in the normal course of clinical investigation can be treated in the same way. They can be combined and animated to allow the observer to ‘fly through’ any part of the body. Flying through blood vessels can identify the size and position of obstructions and narrowed areas with great precision. Flying through the colon can identify, in great detail, polyps that require surgery, and the image sequences can help to plan it accurately. The technique is exceptionally useful in the teaching of surgery.
Conclusion
There is now a case for medical imaging to embrace all the traditional uses of medical photography, as well as new methods such as MRI, CT, X-ray angiography, ultrasound, and thermography, even though practitioners using these techniques are often cardiologists, radiologists, physicians, and surgeons. In some countries medical thermal imaging does have specially trained practitioners called thermographers. The distinction between photography and imaging continues to diminish now that digital imaging has developed so spectacularly. Specialist computer programmers can now claim to be medical imagers.
Imaging has been one of the great successes in medicine and physiology during the latter part of the 20th century. The pace of development and innovation continues to increase and to provide tremendous benefits in the diagnosis, management, and treatment of a huge range of diseases, and to contribute to better medical care for very many people. One of photography's most important attributes is its permanence, so that it not only provides durable pictorial records, but can be used to record longitudinal studies of progressive chronic conditions, as well as the progress of their cure.
— Raymond P. Clark
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