Digital imaging in clinical photography, Part 2

Journal of Audiovisual Media in Medicine 1994; 17: 105-110

Digital imaging in clinical photography, Part 2 SIMON BROWN

Following Part 1 of this article in the previous issue’ in which the technical aspects of the system were explored, Part 2 looks at the use of the digital camera system in the clinical photographic studio.

Technology has provided the means to undertake clinical photography without film - but is it a practical possibility? The digital camera system (DCS) was tested in routine use alongside conventional film-based cameras in the Depart- ment of Medical Illustration at The Hospital for Sick Children, Great Ormond Street to gauge the overall ‘usability’ of the system in a real-life setting.

Use of the DCS during clinical out-patient sessions

The total number of patients photographed annually at The Hospital for Sick Children averages 2400, which equates to over 45 each week. The majority of these patients are sent to the department by the four primary users - ophthalmology, dermatology, plastic surgery and dentistry - but there can be considerable differences in both the number and the style of photographs required by each of these specialities.

No adapters were available to fix the Nikon camera back to any of the eye cameras (Topcon [Tokyo] fundus or Zeiss [Oberkochen, Germany] slit- lamp), so ophthalmic work was limited to the nine positions of gaze and full-face studio pictures as and when requested.

The dermatologists request both prints and transparencies of a wide range of conditions, most of which come to the

Simon Brown, MSc, FIMI, ABIPR RMIR is Direcror, Medical Illustration, Institute of Child Health, 30 Guilford Street, London WClN IEH, UK 0 1994 Butterworth-Heinemann Ltd 01 40-51 IX/94/030105-06

department’s studio with some ward calls also being necessary. Anything from two to 12 views may be requested, the mean being four.

The plastic surgeons often work closely with the dentists and maxillo- facial surgeons, dealing with cleft lip andor palate, facial anomalies and some of the less common syndromes such as Apert’s or Crouzon’s. Many children are seen for several years, undergoing facial, lip and palate reconstruction and alveolar bone grafts. The mean number of views requested by both the dentists and plastic surgeons is seven, the range being three to 13.

The potential number of photographs to be taken during a one-week period is therefore quite high and, as virtually all patients have more than one view requested, the construction of composite photographs on single sheets could be tested repeatedly.

The decision was taken not to attempt photography with the digital camera on location in either wards or operating theatres. Having both digital and silver running concurrently would imply that either one photographer had to use both systems or that two members of staff would have to attend each location. Neither option was desirable at that stage - location work like this has to be carried out quickly and either two photographers in a theatre or cubicle together, or one photographer having to change cameras for each picture, was not considered wise.

Standard photographic procedures

The department normally operates with two medical photographers on duty.

Much of the studio photography is carried out with both photographers in the room together, one using the transparency-film camera, the other using the negative-film camera. If a patient’s request form indi- cates only one output - prints or slides - just one photographer undertakes the work while the other proceeds with other duties. If one is called to a ward or operating theatre, the other has to carry out all the studio work.

It was therefore a simple matter to introduce the digital camera as an additional recording medium. If both photographers were present, one handled the digital camera alone, while the other used either or both of the film-based cameras according to the clinician’s requests. If a photographer was working alone, the decision to use the digital camera was left to them, depending on the cooperation of the child and parents and the ease of photography.

The department was given the use of the DCS 100 by Kodak for a 4-day period in 1993 and the DCS200 for a similar period of time, by IMC (Windsor, UK), later in the year. This was therefore a valuable opportunity to assess the concept of digital imaging as a whole, and to make subjective comparisons between the two systems.

Use of the DCSlOO

When the DCS100 was delivered, a whole day was spent assembling the system, taking ‘snap-shots’ around the department so that the photographers could acquaint themselves with the camera (as the department is normally equip- ped with Nikon FM2s rather than F3s) and checking the calibration of the camera against the ‘normal’ studio

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exposures on ISOlOO film. A degree of unfamiliarity with the camera in the studio was evident during the first few sessions, the photographers feeling a little clumsy with the system, and they expressed both reservations and a dis- tinct aversion to having the DSU (on its trolley) so. close to the operating area. The exposure range was also seen to be quite limited and the LCD monitor had to be closely inspected to verify the accuracy. There was nothing that could be done about the former problem, as the coiled cab!e was an integral part of the system, but a National Television Stand- ard Committee (NTSC)-compatible monitor was added. allowing the photographer t q see a larger image. of far higher quality than the LCD monitor. immediateiy. This produced a marked improvement in exposure accuracy - and those that were incorrect could be deleted instantly - but the main advan- tage was ‘that the children were trans- fixed. The simple bonus of seeing the photograph just taken had a marked effect on the degree of cooperation from both child and parent and the fact that they had been photographed with ’new technology‘ obviously counted for a great deal.

It was also realized very early on that the almost-square (5:4) aspect ratio of the DCS 100’s viewfinder meant that there was seldom any need to turn the camera vertically to portrait format. Doing so meant that the image, once transferred to Photoshop, had to be rotated 90” and, as version 2.01 was then current and rotation was very slow indeed. this was a severe time-was1er. Furthermore, little was pained in temis of image size, so all photographs were shot in landscape format, and then cropped as required (a much faster operation) once transferred to the computer.

It also became apparent that the speed of the system, transferring images to the computer and then editing them. was considerably slower than had been beliued - demonstrations are always well rehearsed - and i t was obvious that a substantial change in work practice would have to be undertaken. as well as a massive capital investment. if digital imaging was to be adopted as a standard procedure.

Use of the DCSLOO

The DCS200 was used for a week later in the year and although some of the ‘novelty value’ had worn off, i t was recognized as a significant change from

the previous model. It was neater and had better resolution and far greater portability, although the storage capacity of SO images was noted to be a potential problem during a busy clinical session. It was not unusual for between eight and 15 dental patients to arrive during one clinic and with an average of seven views on each patient it would be necessary to off-load the camera’s disc at some point, even if starting with a blank disc drive, and this procedure could potentially take up to 30 min.

Gone was the ability to preview the image; the photographers disliked this immediately, although they knew full well that they did not have an instant ‘preview’ facility with normal film-based cameras. The camera also ‘went to sleep’ very quickly between photographs - when first switched on. and the shutter lightly pressed, the camera whirred into life and allowed a picture to be taken. If this did not happen within 8 s. the camera powered-down the disc drive and switched off, and the shutter had to be pressed again to reactivate it, incumng a delay of 2-3 s. For paediatric photography this was a major problem, as the photograph often has to taken very rapidly indeed. Furthermore, there had to be a time-delay of around 3 s between exposures as the first was written to disc; this again was seen as a disadvantage, as it is frequently the case that the photographer knows that the subject in question may have moved slightly and therefore wishes to take a second picture quickly.

The biggest problem, however, was the size of the CCD (charge-coupled device), necessitating the use of the 55-mm Micro Nikkor and. even then, at a greater camera-to-subject distance than the 105-mm Micro lens. Accuracy of focus was hard to judge - although practice would no doubt have made this easier - but a photographer of paediatrics gets used to holding the child’s arm, hand. foot or shoulder, and still being close enough to look through the 105-mm lens and compose the photograph. With the extra distance involved (as the 55-mm lens is now the equivalent of using a lens approaching 150-mm focal length on 35-mm format) this was no longer possible.

Nonetheless. the experience was well worthwhile for the whole photographic staff. Some excellent photographs were taken - and a few less successful ones - and interest was still shown in the system by the patients and parents. even if they could not see the images immediately. Examples are shown in Figure 1.

It did not become apparent until later that the f/2.8 55-mm Micro Nikkor was incompatible with the system, producing a magenta iris-shaped artefact in the centre of the frame. All the photographs taken during that week were saved as camera files, some given a cursory inspection, and then stored for later analysis. When the problem with that particular lens was discovered at a later date, several of these files were opened to verify that the defect was occurring on all DCS200 bodies - which it was -, and the majority were deleted. Other patients were then photographed using the new f/2.8 60-mm AF-Micro Nikkor, on which the problem did not occur, and these were more successful. The fact that the lens was now the equivalent focal length of I60 mm exacerbated the photographer-to-subject distance even more, albeit to a minimal extent, and the autofocus facility of the lens was found to be completely useless for medical work and was switched off.

Later trials

Two digital camera trials are now running within the department, one for the dental and plastic surgeons, the other for the craniofacial surgery team.

The dental department - together with the medical audit unit - are setting up a networked database system to achieve high-speed access to all patient data, starting with the cleft lip and palate cases. A modem windows-based data system allows a variety of search criteria to be entered and the resultant subsets will show patient, dental and orthodontic data, speech therapy results, photographs of dental casts and clinical photographs. To achieve this, standard clinical views are taken and transferred to the host Macintosh computer for cropping and editing as described in Part 1 of this article. These are then resampled to quarter-screen VGA format (320 X 240 pixels) and saved to a DOS-formatted diskette or removable hard disc and reopened on an IBM-compatible machine using Aldus PhotoStyler (Edin- burgh, UK). This allows the images to be converted to 256 colours - as opposed to the 16.7 million of 24-bit - and resaved to give 77-kbyte files. The final files are then transferred to the dental department’s host computer and indexed within their database system.

The second trial is being undertaken primarily to examine the merits of rapid turn-round of clinical photographs which is really only possible with a digital

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a little breathing space while solving the problem of storage of these images. A 1.2-Gb external hard drive has been partitioned to include a 600-Mb area for archive storage and this will be transferred to CD-ROM as and when it is filled.

Two image database software packages - Kodak’s Shoebox and Aldus Fetch - are currently being evaluated to set up an indexed retrieval system for the images within the Medical Illustration Department.

Figure 1 From top to bottom: a five-picture composite mount for the neurosurgical team; close-up of a viral wart on a finger; close-up of a single eye and a medium close-up demonstrating the hair in Netherton‘s syndrome in an infant. The hospital Trust logo, greyscale and colour patch and sections of the lettering are an integral part of templates on to which resampled and edited digital images are placed

system. At present, the neurosurgeons bring a child (or children) into hospital for the planned operation and clinical photographs are taken that day. The patient(s) may be due for operation within a day or two and it can be difficult to produce finished prints -which are passed around the surgical team at pre-operative discus-

sions - within that time period. With the digital system working efficiently it is possible to place the required photographs on to composite mounts as previously described and to deliver them to the ward within a few hours.

Both these trials are running with limited numbers of patients, which gives

Other uses of the system within medical illustration

Although this article has concentrated on the clinical applications of the digital cameras, the potential use in other areas is too great to ignore and certainly merits a brief discussion.

Photography for publication

Many departments now offer an in-house publishing and page layout service using microcomputers, and these frequently include photographs of the campus, departments and other ‘general’ photographs. Until recently, the only way of achieving high-quality photographs within a booklet was to give good bromides or transparencies to the printer and have them screen the prints or separate the transparencies using their own colour reproduction facilities. With the advent of high-quality scanners, it became a perfectly feasible option to scan one’s own photographs, incorporate them in the publication, and output directly to film for subsequent plate- making by the printers. If monochrome derivatives were needed from colour originals, or if special effects such as duotones were required, it was still far simpler to hand the job over to the printers immediately.

That situation has now changed completely. The digital camera allows photographs of high quality to be produced, colour corrected and cropped as required, resized and resampled to the optimum resolution, reduced to greyscale for monochrome and placed directly into the publication (separated for four-colour or duotonehitone if applicable) and printed straight to film with no loss of quality at all. A booklet for The Hospital for Sick Children’s Cardiac Unit has been produced with duotoned photographs in precisely this manner.

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Reprographic photography tion and longevity - as well as having extremely powerful machine, based on

The image editing and composite-mount production capabilities of images produced with the digital cameras have already been demonstrated. The potential for applying these techniques to reprographic photography is good - radio- graphs, scans, electrophoresis plates. blots and other acknowledged ’difficult’ photographic originals can be enhanced and balanced far more easily than ever before. The time involved in the transfer and individual editing of pictures would be thc main constraint and the sheer volume of work would preclude any storage of such images in the long term.

The ecological aspect

A digital expowre. when compared with a silver-based film. uses no manufac- tured plastic base and no silver. and no chemistry i h needed to see a \,isible result. It does not need t o be sent to a laboratory for processing. saving both time and pollution and. i f printed. the paper appears From an electronic printer rather than a wet photographic process.

These advantages need to be weighed against the waste and pollutants involved in the production of the electrical com- ponents themselves hut these can also he used many times at no extra cost, whereas silver-recovery can be labour- intenhive and uneconomic for the smaller user.

The future prospects of digital imaging for the amateur bodes well. Kodak have already introduced Photo-CD. w,hcrc a processed film can also be stored electronicallj o n CD-ROM at various levels of resolution: as the niar- ket becomes used to viewing their photographs on a domestic television or nion- itor i t is likely that they will lean further in that direction and that the demand for ‘enprint‘ service$ m a y drop. The cumu- lative effect therefore will probably reduce the silver consumption dramat- ically over the next decade. Silver imaging will no doubt remain - probably under the cachet of ‘older and better’ and those with real expertise in printing can look forward to becoming ’minority‘ experts. I t i u the author’s vieu. howe\ier. that by the end of the decade. the difference in quality between a 20 X

Winch portrait produced from 120-size film and one produced to the same size electronically will be indistinguishable. and the latter will hold considerably more potential for repetition. dissemina-

more scope for retouching.

The costs of a digital system

No practical analysis or assessment could be complete without a breakdown of the capital and running costs. This section will certainly be outdated rapidly - while the principles of digital imaging in the clinical studio will probably enjoy an increased following, this will also be due to the changing capital costs of the procedure which, at the time of writing, are very high indeed.

Capital costs

When the DCSIOO was announced, its retail price was in the region of €15 000. A5 the DCS200 came on to the market at around f6000. the price of its predeces- sor fell to the point where a recom- mended price is no longer quoted. It seems likely, however, that the cost of either camera system will be around the 56000 mark until 1995. The analysis of capital costs will therefore be based on this figure for either camera, and on the requirements in the Department of Medi- cal Illustration at The Hospital for Sick Children.

In this department. three pairs of camera bodies are used, two pairs in carrying cases for either studio or location work (one for colour negative, the other for transparency film) and the last two are kept for backup in case of failure or for use with black-and-white or other film types as required. In theory. therefore. each pair could be replaced with one DCS. as the ‘film type‘ becomes irrelevant and the end result can be balanced to any light source. Most of the existing lenses could be used with the DCS - with the obvious exception of the fE.8 55-nim Micro Nikkor as previously described - and so only two new 60-mm Micro Nikkors would be required. Cam- era and lens costs would therefore total around f 19 000.

Printers for the system are dropping rapidly in price at present. The Kodak XLT7720 had a list price around f 16 000. although its successor, the XLS8300. has already appeared with retail prices around half that figure. I t seems likely that the price of a good-to- high-quality dye-sublimation printer will stabilize at around f7000 in 1994.

The ’ideal‘ computer system on which to manage the digital image acquisition and processing would need to be an

the highest-speed processor currently available. In 1994 this would imply the Motorola 68040, the Intel 80486 CPUs or the new PowerPCs. These new RISC (Reduced Instruction Set) CPUs will be of considerable benefit in the coming few years as software such as Photoshop is rewritten for them.

A ‘shopping list’ of the component parts needed to put together a high- speed, high-capacity dedicated computer for digital processing might be as shown below in Table 1. The total cost in the UK would be approximately E45000 excluding value added tax (VAT).

Certainly i t would be possible to use a computer such as the Macintosh IIfx as previously described, or a PC-conipat- ible machine of similar speed and configuration, but the time spent waiting for the image to be processed, compressed and saved to disc would be considerable and frustrating for the operator. With the volume of images involved too, empha- sis must be placed on the mass-storage capabilities of the system and its potential for future expansion.

The total cost for capital items at this stage totals over &70 000.

Running costs

One can compare, for example, the cost of using a full 36-exposure roll of negative film and having it printed, together with a roll of reversal film, against the cost of producing a similar number of pictures on a digital camera and outputting both to print and transparency. In this exercise, all figures have been rounded to the nearest Sop, as costs will obviously vary slightly according t o manufacturer and supplier, and VAT has been excluded as one is concerned with basic relative costs.

A roll of negative film is around f4.00; a ‘package deal’ process-and- print will cost around f l O . O O (and might take anything from 1 day to 8 days for completion depending on laboratory and location). A roll of reversal film is around f6.00, with f3.50 processing. If an average of seven patients are photographed o n the negative film, each allocated around five frames and two card mounts, a total of 14 mounted cards will be produced. This will need to be labelled. Raw materials for this procedure therefore total around f23.50. plus card and labels.

The same seven patients photographed on a digital camera can almost certainly be given one composite mount each. The

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Table 1 The ’ideal’ computer configuration for routine digital image processing

Basic computer: Macintosh Quadra ( Apple Computer, Cupertino, California, USA), fitted with 256-Mb on-board memory, a 500-Mb disc drive for application storage and a I-Gb disc drive unit, partitioned to allow high-volume file storage and a 256-Mb section for Photoshop use. A custom card for high-speed JPEG” compression should be fitted.

2 Mb of video RAM to allow 24-bit colour display. Use a standard 14-inch Apple monitor on the built-in socket. Add a Supermac Thunder/24 card and a Supermac two-page display; twin monitors allow viewing of the image on one while control palettes stay on the other. Add a Supermac Thunderstorm accelerator card to speed-up Photoshop.

Use a fast-cache card, SCSI-2 accelerator and a high-capacity drive array. Install a digital audio tape (DAT) system for tape backup, a CD-ROM drive and a rewritable optical drive for archival storage.

Basic system software; Adobe Photoshop (Adobe Systems, Mountain View, California, USA) and others as required for image databasing and retrieval.

Supplies of optical discs and DAT cartridges.

Video display:

Storage:

Software:

Media:

* Joint Photographic Expert Group

images can be edited and ‘comped’ together quickly and will then be printed at a cost (if the printer is purchased) of around f3.50 per sheet, totalling f24.50. If a roll of reversal film is also used, another f9.50 should be added, totalling f34.00.

Looking at the high capital costs, coupled with higher-than-normal running costs, one might be inclined to dismiss the concept of digital imaging as uneconomic. There are other factors, however.

The time element - and specifically turn-round times of clinical photographs - is becoming increasingly important. Many support service departments are required to produce their own ‘Quality Standards’ and these frequently involve the speed with which patient-centred tests and procedures are camed out. There is much reason to suspect that illustration departments will be required to produce photographs for the patients’ notes at much higher speeds in the near future. Digital imaging will allow this, provided the necessary investment is made in fast and reliable hardware.

There is no waste in digital imaging. Inaccurate or poor images are simply deleted. The wastage factor on conventional film has been ignored in this example, but can be significant. It is unusual for every frame of a 36-exposure film to be used, and a percentage must therefore be added to account for that fact.

Confidentiality is a major bonus of keeping the image processing in-house. It is certainly possible to run in-house processing and printing of conventional

film, but the wastage factor is high and many establishments find that it is grossly uneconomic; the price war waged between competing laboratories means that the customer often gets a good deal and has to have a high volume - of the order of hundreds of prints each day - before the prospect of in-house ‘wet’ processing becomes economic.

Summary

Advantages of digital imaging include the immediacy of hard-copy images - either print or transparency - and complete confidentiality if the printing is carried out in-house. With the develop- ment of electronic teaching media within hospital and medical school campuses, a digital store of library images is a valuable resource and can be exploited further.

Great potential exists in the area of reprographics and image enhancement, although these have only been discussed briefly. Image editing software is powerful - and necessary - and is likely to develop still further.

From the user’s point of view, the systems today are still too slow and have limited capacity, as well as being difficult to use, due to the physical size of the CCDs necessitating the use of abnor- mally short focal length lenses.

Future developments

There is no doubt that the progress in digital imaging over the past couple of years has been enormous and there is

also little reason to doubt that it will continue. As a leader in the imaging world for some decades, it is likely that Kodak will keep developing the system, until it surpasses the quality currently attainable with conventional silver imaging. This could come about in several ways.

At present the DCS has limited capacity both in the resolution of the images (due to the pixel size and density of the CCD) and the speed with which it can record and store these images. These latter factors are due to the built-in disc drive, access time to which is measured in milliseconds. Recent developments in solid-state drives show that dynamic random-access memory (DRAM) chips can be used as a substitute for mechan- ical drives. They are more compact, have no moving parts and can have a huge capacity for storage. It is possible, for example, to build 1OOOMb (1 Gb) of DRAM into a casing considerably smaller than an equivalent-sized hard drive and the access time would then be measured in nanoseconds. If a 2-5-Gb solid-state drive were to be built as a belt-pack for the DCS, the photographer would have the capability of shooting hundreds of photographs at any time, swapping belt packs should the capacity be reached.

The CCD itself will certainly improve. The 4500 X 3000 pixel grid advocated by Kilboume2 is unlikely to be attained within the next 1-2 years, but the new M6 chip from Kodak with a 3000X 2000 matrix (and close to a 24 X 36-mm CCD) has been shown and tested, at which point the resolution of the device

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is perfectly acceptable and the camera's normal lenses become usable.

File sizes will increase still further as a result of this: the M6 chip delivers 18-Mb images. However, as computer CPUs become faster, and with compression techniques constantly developing, images occupying 18-50Mb will no longer be unworkable and will each be compressed to around 50 kb as a matter of course.

Image database software is extremely important. At the time that this work was completed, the author had managed only a brief look at t\vo packages but could see that they had great potential. Minia- ture 'thumbnails' of images can be browsed rapidly, descriptive text and index number3 can be attached to spe- cific images and found at relatively high speed. With the thousands of images produced by illustration departments throughout the UK each year. a system such as this would be indispensable.

The cost of computer hardware con- tinues to fall. As a comparison. in 1982. the author purchased ten 1-kb 'chips' to upgrade an Acorn Atom computer from its standard 2kb to 12 kb. Each chip cost E12.00 (present equivalent value around E l 0 0 each). The 16-Mb upgrade for the Macintosh Ilfx cost €400.00 in 1993. which is a significant reduction in relative terms.

Hard storage. in terms of disc drives. has also dropped in price. to the point where 1 Gb internal drives are now commonplacc and affordable. By the year 2000, a 10-Gb camera will be standard. ax will personal computers addressing upwards of 2 Gb internal memory and storing files on high-speed solid-state drives. the capacity of which can only be imagined. Initial costs are

bound to be high, but market demand and competition from other manufac- turers will always force prices down to realistic levels.

Educating the photographers

There is a huge interest in the concept of digital imaging which, until recently, has been 'from the sidelines', with many photographers watching and waiting. The journal of the British Institute of Professional Photography, The Photo- grcrpher, has run a monthly column on the subject, enthusiastically written and illustrated by John Henshall, their former President. He has demonstrated quite convincingly that digital pictures can be as easy to take as those on conventional film and his section is one of the few - and among the first ever - to publish full four-colour separations from digital originals.

The interest in the subject shown on the MSc course in Medical Illustration at the University Hospital of Wales has shown the extent to which photographers know how trends are developing. North- East Surrey College of Technology (NESCOT) now runs a BTEC HND Course in Electronic Imaging and the author understands that great interest has been shown. It is unlikely to be the only college running such a course for long.

Some dealers which used to be 'Pho- tographic-only' establishments, now stock the digital camera systems and the computers necessary to run them, and run training and tuition on the digital systems.

The medical illustrator

Most professionally-qualified medical photographers already have the know-

ledge to use the digital systems and many departments already have the computer equipment. Much interest is now being shown in the subject as the advantages become clear and the disadvan- tages become understood. For most potential users, the only unanswered question is 'When?'

Acknowledgements

The author would like to thank Applied and Digital Imaging at Kodak Limited, Hemel Hempstead (Tel: 0442 61 I22), for the initial loan of the DCS100; IMC in Windsor (Tel: 0753 830999) and KJP at Drummond Street, London (Tel: 07 1 380 1144), for subsequent loans of the DCS200 and for their continued help and advice during this work. Additional thanks goes to KJP for their generous financial support in the reproduction of the colour illustrations in Part 1. Thanks too, to all staff in the Department of Medical Illustration at the Institute of Child Health and Great Ormond Street Hospital for Children NHS Trust - their constant enthusiasm and support has helped a great deal. Finally, thank you to Sarah Dennehy who 'modelled' for the initial DCS tests and whose face and eyes appeared in the sample images on diskette.

References

1. Brown S. Digital imaging in clinical photography, Part 1. J Audiov Media Med 1994; 17: 53-65.

2. Kilbourne S. A primer on digital imaging - post production for still photography: Part 1. Journal of Biolog- ical Photography 1991; 59: 43-8.

I For more information, please contact Messe-und Ausstellungs-Ges.m.b.H. Koln, Messeplatz 1, D- 50679 Koln. Germany. Tel: +221 8210 or Fax: +221 821 2574. I

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Documents

Digital imaging in clinical photography, Part 2