VOL: 96, ISSUE: 45, PAGE NO: 9
Garry Swann, BA, FRPS, MIMI, RMIP, is head of medical photography and graphic design, Doncaster Royal Infirmary and Montagu Hospital NHS Trust, Doncaster
The clinical photograph has long been recognised as a useful aid in the treatment of pressure ulcers and other wounds. A series of photographs of the same area, taken at appropriate intervals, provides a visual reference showing the progress of treatment that cannot be matched by either memory or written description, especially over an extended period (Figs 1-3).
In addition to providing a record for the patient’s notes, images can be a valuable aid to teaching. They may also be used to support research projects, for reporting on the efficacy of a treatment regime, as an aid to audit, as evidence in litigation and for publication.
However, images are of limited value if they are not sharp, clear and free of extraneous detail. They must be correctly dated, and if they are part of a series be comparable over time.
Positioning the patient
When taking a photograph, routine ward procedures should always be a priority. If possible, take advantage of the wound dressing timetable so that the patient will not be inconvenienced more than is necessary. It may also be useful to photograph the wound site both before and after wound cleansing procedures.
The assistance of a nurse or support worker is essential. If barrier nursing is in use, the photographer will need to comply with the hospital’s infection control protocol and should not touch the patient or the bedding.
Any repositioning of the patient should be done by trained ward staff at the photographer’s direction. When photographing the sacral area, for example, the patient may need to be rolled over onto one side. Gentle tension on excess body tissue or the separation of the buttocks may be necessary to reveal the depth of a cavity (Figs 4, 5), and a leg may need to be raised when photographing the heel or toes.
Decisions on patient positioning for photography can be made only with regard to a specific patient and the particular view required. It may be necessary to take more than one photograph to produce an adequate view of a wound site. A wound that extends around the calf, for example, will need to be photographed from the front and back (Figs 6, 7). Lateral views of both the outer and inner calf may also be needed. A large lesion on the sacrum may require a general view to place it and a close-up to show detail (Figs 8, 9).
Framing the picture
Having positioned the patient, the photographer needs to adopt an appropriate position to frame the picture. What matters is the correct alignment of the subject matter in the camera’s viewfinder.
Although the patient’s body may be difficult to move, the camera is not. The photographer must therefore hold the camera so that, as far as is possible, the area of the body being photographed is aligned as though the patient were standing up and presenting his or her wound squarely to the camera. This may necessitate the photographer crouching, kneeling, standing on a raised platform or lying on the floor.
The sacral area, for example, should be aligned so that the spinal column runs in a straight line from one side of the frame to the opposite side (Fig 10), whether the picture is framed horizontally or vertically.
Heels are often difficult to photograph and the most appropriate camera position is the one that provides the best view of the lesion, but a single picture may not be enough (Fig 11). Elbows can also be awkward, but the same north-south/east-west, anatomically correct alignment can usually be achieved.
In medical photography it is vital to show a clean and tidy wound site that is free of distracting detail. The preservation of the patient’s privacy and dignity are paramount, and the face and genitalia should be excluded wherever possible. The edges of underclothes, creased or soiled clothing or rumpled bedding can ruin a good photograph.
Clean, white hospital sheets make a good photographic background. The sheet should be placed behind the area to be photographed in such a way that the whole area framed by the camera has a background of white. Any text, motif or security stripe on the sheet should be hidden.
Soiled bedding can be covered by the sheet, which should be tucked under the area to be photographed and pulled taut to get rid of folds and creases.
Legs and feet can be isolated by placing the sheet between the limbs and taking separate photographs of each. Elbows can be isolated from the trunk in the same way.
The plantar surface of the foot is a particularly awkward area to photograph, even under studio conditions. But with care it is possible to organise a tidy background. One sheet is placed beneath the foot and another laid across the lower leg, a neat join being made where the two sheets meet. Taking care to smooth out any creases, the other end of the upper sheet is raised to create a continuous white background to the foot (Fig 12).
The closer the white background is to the area being photographed, the better will be the delineation of the limb or affected area.
When looking through the camera, observe not only the wound site but also every part of the picture framed in the viewfinder, from side to side and corner to corner. If there is anything in the frame that is not wanted or detracts from the wound, put it right before taking the picture.
Using a scale
The inclusion of a scale in the photograph provides an immediate visual reference to the size of the lesion. The scale must be clearly legible and placed adjacent and parallel to the wound site (Fig 13). Because of the laws of perspective, a scale that tapers off at an angle to the edge of the frame does not provide a true indication of size.
The following factors should be borne in mind when using a scale:
- It should not occupy more than a narrow band at the bottom of the picture;
- It should be long enough to allow it to be held against the area to be photographed without including the fingers holding it in the picture;
- The graduations should be of high contrast, that is white on a black background or black on a white background, and it should not have any other markings;
- Rules with metal or glossy surfaces are not suitable because they reflect the light of the flash;
- It should have a washable surface that can be cleaned and sterilised after use;
- For small areas, for example 150mm by 100mm, a scale graduated in millimetres is suitable;
- For large areas, a centimetre scale with bold divisions is recommended.
No other item, such as a finger, a pen, a coin or a surgical instrument, should be used as an indicator of size in a clinical photograph.
Scales that are used for medical photography should be kept solely for this purpose, but disposable ones printed on a self-adhesive flexible tape are available.
The best and most convenient type of camera for medical photography is a 35mm single-lens reflex camera. The main advantage of the SLR is that the photograph records what is seen through the viewfinder, so it is easy to tell whether the picture is correctly focused.
Compact cameras and most instant cameras use a viewfinder that functions separately from the camera’s lens so there is a discrepancy, known as parallax, between what is seen through the viewfinder and what the camera photographs. The closer the camera is to the subject, the greater the discrepancy between these two.
Also, the closest focusing distance of many compact and simple cameras is about one metre. For most pictures of wounds, the photographer needs to be nearer than this.
The SLR camera should be fitted with a macro lens, which is designed for close-up work, that has a camera-to-subject distance of less than a metre. A macro lens has the added advantage of having the magnifications or ratios of reproduction inscribed on its barrel. These are usually shown as 1:10, 1:6, 1:4 or 1:2, meaning one-tenth, one-sixth, one-quarter or half scale.
This is particularly convenient if a series of pictures is to be taken. The magnification used on the first occasion should be noted so that it can be reproduced on each subsequent photograph.
The common focal lengths of macro lenses are between 50mm and 60mm, and 90mm and 105mm. The longest focal lengths are most useful for smaller areas, that is those covering about 15cm by 10cm, as they give a good image size from a convenient distance with little distortion. The shorter focal lengths can encompass larger areas, that is about 36cm by 24cm, from the same distance.
A standard 35mm-format lens with a focal length of about 50mm is adequate, although this will introduce distortion when it is used close-up. Wide-angle lenses should be avoided as they can result in unacceptable levels of distortion.
A reasonably priced zoom lens with a focal length of 28-105mm, for example, would be a good choice, especially if it has a macro facility, but the picture quality is likely to be inferior to that of a true macro lens.
Instant-picture systems are convenient but do not produce a negative so it is difficult to get extra copies or enlargements. Most instant cameras are also unable to focus at distances of less than about 0.7m, so they are not suitable for close-up photography.
Digital cameras are convenient, but much of what has been said about compact cameras applies equally to them and the quality achieved by the less expensive digital cameras is not yet equal to that of a good 35mm SLR.
They are becoming increasingly common, however, and offer a wide range of facilities. The photographs are loaded directly into a computer and can then be used in a variety of ways. For example, they can be printed out, pasted into reports, used as projected images for teaching or placed on the internet.
The temptation to manipulate digital images, which is a relatively simple procedure, should be resisted. Tidying up the background for publication may be convenient, but if a picture is to be used during litigation the photographer usually has to certify that it has not been touched up.
Choosing the film
A wide range of film stock is available, such as colour negative for prints and colour transparency for slides. Black-and-white film is hardly ever used in clinical photography.
Colour balance can vary between different makes of film, so if a series of photographs is to be taken it is a good idea to use the same type of film each time.
Even then, processing and printing can create differing results. The only way to overcome this is to include in each photograph a set of standard colour patches, which can be obtained from certain film manufacturers, and to have the pictures printed to this standard by a specialist processing laboratory. This is expensive.
High-speed film is not necessary if you are working fairly close to the subject and using a flash with a reasonable output, so a medium-speed film (ISO 100/21°) is recommended. This should give adequately exposed negatives and sharp, grain-free prints.
Colour film is balanced to give natural looking results in only one kind of light - usually daylight. Since the quality of light on a ward or in a clinic cannot be guaranteed it is vital to use a consistent light source, namely an electronic flash.
An electronic flash matches the colour temperature of daylight, so it can be used with daylight film without the need to introduce colour correction filters on the camera lens.
A small electronic flash unit mounted on the camera is adequate, but at distances of less than a metre, the manufacturers’ advice on camera settings becomes unreliable. The only way to achieve consistently good results is to carry out tests with the flash at various distances, for example one metre, 0.75m and 0.25m, taking careful notes of the camera settings used for each and comparing the results after processing. This should make it possible to draw up a table of camera-to-subject distances with the appropriate camera settings for the flash used.
A flash that can be separated from the camera and positioned to illuminate the wound, especially if there is a cavity, is preferable. This technique requires a more sophisticated camera with a flash socket and a flash synchronising lead, but it allows the photographer to achieve a certain amount of modelling of the subject to show skin texture, the depth of a cavity or surface undulations.
Only partial modelling of the subject can be achieved using a single light source, and a flash mounted over the lens will not show any modelling effect at all.
Professional medical photographers always prefer to take pictures under controlled studio conditions, using several flash heads firing simultaneously, with the subject properly lit against a plain background (Fig 14).
Operating theatre lights, treatment room examination lights, general fluorescent room lighting or bedside lamps should never be used for photography.
Aperture and shutter speed
Apart from focusing, two camera controls are significant - aperture, which is sometimes called ‘the f. number’, and shutter speed. These are set in conjunction with one another and are directly related to the brightness of the light and the speed (ISO rating) of the film being used.
The aperture is adjusted using an iris in the body of the lens. In general smaller apertures, such as f.16 or f.22, are recommended because they produce a sharp image over a deeper area (depth of field). This is particularly important in close-ups.
The shutter speed can be varied from as little as 1/1,000 of a second to several seconds, but most cameras cannot synchronise the flash with a shutter speed of less than 1/125 of a second. Pictures taken with a hand-held camera at shutter speeds of more than 1/30 of a second are likely to lack sharpness as a result of camera shake.
In practice, therefore, flash pictures are usually taken at the ‘X’ setting on the shutter-speed dial, which is usually about 1/80 of a second.
Simple cameras with built-in flashes are usually automatic or have no means of self-adjustment. At best, variable results can be expected when using these.
A specialist photographic laboratory, particularly one that is accustomed to dealing with medical subjects, is the best choice. Local high-street processing agencies are not set up to develop this type of subject matter and may not be happy about handling it.
It is always best to notify the processors about the nature of the pictures and to ask whether your prints can be kept separate from other customers’ work.
If a local high-street dealer is used, it is even more important that the patient cannot be identified from the photographs.
Most departments of medical photography operate a patient consent scheme. If the patient is in a fit state to give his or her consent, it should be obtained.
A patient’s inability to give consent need not preclude the taking of a picture because, as a record of progress, it will form part of the patient’s treatment. The consent of a relative, or in the case of a minor a parent or guardian, is equally acceptable.
As with any other aspect of treatment, the patient has the right to refuse to be photographed and this must be respected.
Consent should be obtained on each occasion that a patient is photographed and consent forms should be filed with the photographic record or in the patient’s notes.
Nurses who do not have access to a hospital medical photography department, such as those working in the community, but wish to record the appearance or progress of their patients’ wounds are advised to obtain their patients’ consent to photography on an official form (see box).
If consent has not been obtained for any reason, this should be noted.
Filing the photographs
As the pictures are taken, complete a brief record card showing the patient’s details, the date and time the photograph was taken, the magnification and exposure details and a cross-reference to any other photographs of the same patient. Keep this record card with the consent form.
As soon as the photographs return from processing, identify each negative and print and store the record card, negatives and prints methodically. Confidentiality is as important at this stage of the procedure as in the earlier stages.
Various inexpensive storage systems are available for negatives and prints and a careful and methodical approach when the pictures are taken and processed will be worth the effort.
Although quality photographic equipment is generally available and automatic cameras appear to enable people to take good pictures, many considerations need to be taken into account when taking photographs in a clinical setting. If nurses have access to a professional medical photographer this is always preferable to a do-it-yourself approach.