AJR 2000; 175:1519-1524
© American Roentgen Ray Society
Role of Computer Technology in Medical Illustration
Frank M. Corl1,
Melissa R. Garland and
Elliot K. Fishman
1
The Russell H. Morgan Department of Radiology and Radiological Science, The
Johns Hopkins Medical Institutions and Johns Hopkins Hospital, 601 N. Caroline
St., Rm. 3254, Baltimore, MD 21287-0801.
Received January 24, 2000;
accepted after revision May 15, 2000.
Address correspondence to E. K. Fishman.
Abstract
OBJECTIVE. Recent improvements of computer technology have resulted
in a new approach to medical illustration and the scientific research process.
The purpose of this manuscript is to define the current state of the art and
to review paths of progress.
CONCLUSION. Using examples, we compared the process of
time-intensive hand-rendered art with current art created using new computer
technology. Specific emphasis was made on the newest technologies and how
high-quality lower cost medical art can now be created. These newly available
tools and illustration methods have resulted in a new approach to research,
creation, and reproduction of medical art.
Introduction
Medical illustrators play a major role in the radiology education process.
Whether used to teach a complex surgical or radiologic procedure, to define
typical or atypical patterns of the spread of disease, or to illustrate normal
or aberrant anatomy, medical illustration significantly impacts learning. Use
of medical illustration is probably as old as medicine itself. However,
significant changes have occurred recently with improvement in computer
software and hardware, resulting in a new approach to research, creation, and
reproduction of medical art. The computer has allowed medical illustrators
greater flexibility and speed when creating most medical illustrations and
multimedia productions. This article discusses many of the differences between
traditional and computer medical illustration, as well as the advantages and
pitfalls of each method. Examples of traditional and computer-generated art
from past publications are used to exemplify these differences.
We compared the process of time-intensive hand-drawn and -rendered
illustration, such as line, tone, or color, with current illustrations created
using new computer technology. The terms "drawing" and
"sketch" refer to the problem-solving stage of the illustration.
The illustrator works out visual problems on paper with a pencil and then
completes a final drawing or sketch that will be rendered.
"Rendering" refers to the final process of painting or inking
(with pen) of the sketch. The illustrations discussed are still images
(nonanimated) used for print purposes. The computer software used is Photoshop
(Adobe Systems, San Jose, CA). Although other painting programs exist,
Photoshop is the professional industry standard for both illustration and
image manipulation of bit map (raster) images and is available for both Apple-
(Apple Computer, Cupertino, CA) and Windows- (Microsoft, Redmond, WA) based
computers.
Specific emphasis is on the newest technologies, the techniques used to
create each illustration, and how high-quality lower cost illustrations can
now be produced. Areas of interest that are being illustrated include general
anatomy, oncologic tumor staging, surgical procedures, and the use of
three-dimensional (3D) helical CT images to develop illustrations.
Computer Versus Traditional Illustration
Time
The time needed to complete a medical illustration varies widely depending
on the experience and speed of the medical illustrator, the complexity of the
content, and the style and method of illustration used. The more complicated
the subject matter, the longer it will take the illustrator to research and
solve a complex visual problem. Different illustration methods and styles can
also have an impact on the time involved in the creation of an
illustration.
Pen-and-ink illustrations are the fastest to produce and the least
expensive to reproduce. Traditional and computer-generated color artwork are
both time intensive and costly to create and reproduce. Contrary to popular
belief, computers and sophisticated graphics software packages do not always
speed up the drawing and rendering processes. If the illustrator is proficient
with graphics software, he or she may have a time advantage, but a software,
hardware, or printer problem may lessen or eliminate this small advantage
(Foerster J, personal communication). When creating one single color
illustration, there is not a significant time-saving advantage of using the
computer over creating traditional artwork. Significant time-saving advantages
of computer-generated art come into play when multiple illustrations with many
steps or versions use the same underlying figure, such as an illustration of a
kidney showing the multiple stages of cancerous tumor growth
[1] (Fig.
1A,1B,1C,1D).
In each illustration, the kidney remains primarily the same while the tumor
changes shape, size, and color on a separate layer over the kidney. Adobe
Photoshop software supports a function called "layers," which
allows the user to paint over the underlying anatomic structures on separate
layers as if a traditional painter were working on pieces of clear acetate
overlying an image. This digital layering method allows the user to freely
create many adjustable layers over the original underlying image without
changing the original underlying image. To create this series of illustrations
in a traditional fashion, you would have to draw and render four separate
plates, adding significant time and cost to your project.
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Fig. 1A. —Computer-rendered medical illustration series showing staging
of transitional cell carcinoma in kidney. (Reprinted with permission from
[8]) Computer allows
illustrator to freely replace or edit background (three-dimensional CT
reconstruction) and reuse underlying anatomic structures that will remain the
same (i.e., kidney) throughout series. Traditionally, background and other
structures would have to be resketched and rerendered for each stage, adding
substantial time and cost.
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Fig. 1B. —Computer-rendered medical illustration series showing staging
of transitional cell carcinoma in kidney. (Reprinted with permission from
[8]) Computer allows
illustrator to freely replace or edit background (three-dimensional CT
reconstruction) and reuse underlying anatomic structures that will remain the
same (i.e., kidney) throughout series. Traditionally, background and other
structures would have to be resketched and rerendered for each stage, adding
substantial time and cost.
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View larger version (56K):
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Fig. 1C. —Computer-rendered medical illustration series showing staging
of transitional cell carcinoma in kidney. (Reprinted with permission from
[8]) Computer allows
illustrator to freely replace or edit background (three-dimensional CT
reconstruction) and reuse underlying anatomic structures that will remain the
same (i.e., kidney) throughout series. Traditionally, background and other
structures would have to be resketched and rerendered for each stage, adding
substantial time and cost.
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View larger version (56K):
[in this window]
[in a new window]
[as a PowerPoint slide]
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Fig. 1D. —Computer-rendered medical illustration series showing staging
of transitional cell carcinoma in kidney. (Reprinted with permission from
[8]) Computer allows
illustrator to freely replace or edit background (three-dimensional CT
reconstruction) and reuse underlying anatomic structures that will remain the
same (i.e., kidney) throughout series. Traditionally, background and other
structures would have to be resketched and rerendered for each stage, adding
substantial time and cost.
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Using the computer may increase the ease and efficiency of communication
between the medical illustrator and client via email, file transfer protocol
(FTP), or a Web site of electronically scanned sketches and intermediate
versions of the final product.
Quality
As sophisticated as graphic workstations and graphics software have become,
the computer does not do research, visual and scientific problem solving,
drawing, or rendering for the illustrator. The computer does not enable the
lay user to sit down and create an accurate and aesthetically pleasing medical
illustration. All the rules (accurate anatomy, good communication, color,
light, shadow, and form) that are learned by trained medical illustrators must
be applied by the illustrator. The computer will not make a better medical
illustration. The potential for high-quality beautiful illustration exists,
but high-end modern illustration does not have to be produced on the
computer.
Cost
The cost of a medical illustration is primarily based on the time invested
in the illustration, not the mode of production. Most illustrators will charge
the same for one full color image that takes 8 hr to create, regardless of
whether it is illustrated traditionally or electronically. If the same kidney
illustration needs to be reused for a series of illustrations showing a
surgical procedure [2] (Fig.
2A,2B,2C),
it may be much more cost-effective to use the computer and change the tumor
and instrumentation on the same art. Traditionally, this anatomy would have
been reillustrated three separate times, resulting in a less cost-effective
product.
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Fig. 2A. —Computer-rendered surgical illustration series showing
partial nephrectomy procedure. (Reprinted with permission from
[2]) This illustration shows
reuse of part of original image. By placing specific parts of illustration,
such as background, incision line, tumor, and instruments, on separate layers,
illustrator has flexibility of editing each layer independently or completely
turning each layer on or off. This illustration also incorporates
three-dimensional CT reconstruction on background layer. It would be difficult
to incorporate this CT image with traditional media. Although X-ray film has
been painted over in past, computer allows much more flexibility for this
process. In B, numeral 1 shows tumor removal, 2 indicates repair and
closure of collecting system, and 3 shows injection of methylene blue into
collecting system to detect any leaky areas.
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View larger version (58K):
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Fig. 2B. —Computer-rendered surgical illustration series showing
partial nephrectomy procedure. (Reprinted with permission from
[2]) This illustration shows
reuse of part of original image. By placing specific parts of illustration,
such as background, incision line, tumor, and instruments, on separate layers,
illustrator has flexibility of editing each layer independently or completely
turning each layer on or off. This illustration also incorporates
three-dimensional CT reconstruction on background layer. It would be difficult
to incorporate this CT image with traditional media. Although X-ray film has
been painted over in past, computer allows much more flexibility for this
process. In B, numeral 1 shows tumor removal, 2 indicates repair and
closure of collecting system, and 3 shows injection of methylene blue into
collecting system to detect any leaky areas.
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View larger version (61K):
[in this window]
[in a new window]
[as a PowerPoint slide]
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Fig. 2C. —Computer-rendered surgical illustration series showing
partial nephrectomy procedure. (Reprinted with permission from
[2]) This illustration shows
reuse of part of original image. By placing specific parts of illustration,
such as background, incision line, tumor, and instruments, on separate layers,
illustrator has flexibility of editing each layer independently or completely
turning each layer on or off. This illustration also incorporates
three-dimensional CT reconstruction on background layer. It would be difficult
to incorporate this CT image with traditional media. Although X-ray film has
been painted over in past, computer allows much more flexibility for this
process. In B, numeral 1 shows tumor removal, 2 indicates repair and
closure of collecting system, and 3 shows injection of methylene blue into
collecting system to detect any leaky areas.
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Advantages and Pitfalls
Advantages
Computer.—Control over digital effects, textures, and color
(e.g., colors can be applied over existing colors without unwanted mixing) is
an advantage of using the computer to create art. Adjustments and some
corrections are usually easier to make. Creation of variations using similar
underlying art is less difficult and time-consuming. The computer also allows
easier and safer image shipping and handling because only a printed duplicate
or disk is sent to the printer or client, not the original artwork, which is
often large and delicate. Drawings can be quickly scanned for rendering on the
computer. Also, the illustrator does not come into contact with toxic fumes
from paint and other toxic supplies.
Traditional media.—The comfort and ease of using familiar
media and tools, speed, and lower cost when rendering with pen and ink, and
the aesthetics of looking at handcrafted drawings, paintings, and textures are
advantages of using traditional media to create medical art. Traditional
supplies are less costly, and there is not a need to upgrade expensive
computer equipment and software. Using traditional media, the illustrator can
develop and maintain a method of working for optimal speed and quality.
Outside forces, such as technologic changes and breakdowns, will not change
the illustrator's method of working.
Disadvantages
Computer.—The cost of the computer, monitor, storage
devices, and software that requires constant upgrading is a disadvantage of
using the computer to create art. The illustrator has to constantly learn new
or relearn upgraded software packages that ultimately change the way the
illustrator works and the style of the work. The illustrator is totally
dependent on technology. Equipment failures happen and can add a substantial
amount of time and frustration to any illustration job.
Traditional media.—Less flexibility when making corrections
and changes is a disadvantage of using traditional media to create medical
art. More work and time are required to create multiple variations using
similar underlying art [3]
(Fig.
3A,3B,3C,3D).
Depending on the medium used, waiting for the medium to dry can add to the
time and cost involved. Drawings have to be transferred by hand to board or
paper for final rendering, which may add time to the process. Original images
have to be shipped and scanned for printing, which can sometimes result in
damaged or lost work.
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Fig. 3A. —Traditionally rendered illustrations show many types of
soft-tissue and muscular infections. (Reprinted with permission from
[3]) This is only part of
series of illustrations in which illustrator could have used same cross
section of thigh anatomy to illustrate and simplify this concept. By creating
this image with computer and Photoshop (Adobe Systems, San Jose, CA),
illustrator would have to draw and paint normal anatomy only once. Each
subsequent illustration would be produced by placing normal thigh onto bottom
layer and adding abnormal changes on separate top layer. Also, by using same
anatomic data for foundation, viewer can quickly look at important information
in each illustration without having to reorient to each new anatomic detail,
such as in certain muscles or layers of fascia.
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View larger version (127K):
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Fig. 3B. —Traditionally rendered illustrations show many types of
soft-tissue and muscular infections. (Reprinted with permission from
[3]) This is only part of
series of illustrations in which illustrator could have used same cross
section of thigh anatomy to illustrate and simplify this concept. By creating
this image with computer and Photoshop (Adobe Systems, San Jose, CA),
illustrator would have to draw and paint normal anatomy only once. Each
subsequent illustration would be produced by placing normal thigh onto bottom
layer and adding abnormal changes on separate top layer. Also, by using same
anatomic data for foundation, viewer can quickly look at important information
in each illustration without having to reorient to each new anatomic detail,
such as in certain muscles or layers of fascia.
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View larger version (82K):
[in this window]
[in a new window]
[as a PowerPoint slide]
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Fig. 3C. —Traditionally rendered illustrations show many types of
soft-tissue and muscular infections. (Reprinted with permission from
[3]) This is only part of
series of illustrations in which illustrator could have used same cross
section of thigh anatomy to illustrate and simplify this concept. By creating
this image with computer and Photoshop (Adobe Systems, San Jose, CA),
illustrator would have to draw and paint normal anatomy only once. Each
subsequent illustration would be produced by placing normal thigh onto bottom
layer and adding abnormal changes on separate top layer. Also, by using same
anatomic data for foundation, viewer can quickly look at important information
in each illustration without having to reorient to each new anatomic detail,
such as in certain muscles or layers of fascia.
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View larger version (79K):
[in this window]
[in a new window]
[as a PowerPoint slide]
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Fig. 3D. —Traditionally rendered illustrations show many types of
soft-tissue and muscular infections. (Reprinted with permission from
[3]) This is only part of
series of illustrations in which illustrator could have used same cross
section of thigh anatomy to illustrate and simplify this concept. By creating
this image with computer and Photoshop (Adobe Systems, San Jose, CA),
illustrator would have to draw and paint normal anatomy only once. Each
subsequent illustration would be produced by placing normal thigh onto bottom
layer and adding abnormal changes on separate top layer. Also, by using same
anatomic data for foundation, viewer can quickly look at important information
in each illustration without having to reorient to each new anatomic detail,
such as in certain muscles or layers of fascia.
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Future Directions
Computers will continue to be an important tool for the medical
illustrator. Software advances now allow the illustrator to create
two-dimensional and 3D work that appears to be traditionally painted. With
increased computer power comes increased speed of production and the ability
to create and manipulate larger high-resolution illustrations, digital
radiologic images, scanned radiographic film, scanned traditional art, highend
3D models, broadcast-quality animation, digital video, and audio. These
digital media can be used to create multimedia programs, Web sites, and
computer or traditional scientific exhibits from a single desktop computer.
Still images and text can be combined in one page-layout program to create a
scientific poster that can be printed or used as a page layout for an entire
book, journal article, or magazine. Still images, sound, animation, multimedia
programs, and text can be combined and organized in multimedia development
software for CD-ROM or can be used in Web development software, then uploaded
to create a Web site or Web-based exhibit.
Accredited graduate programs in medical illustration have quickly
incorporated these digital tools into their curriculum. Although the rules of
clear communication and information architecture have not changed, the
delivery of the content has. Medical illustrators have become digital
biocommunicators, dealing with digital video, audio, 3D graphics,
two-dimensional and 3D animation, and Web development. Medical illustrators do
and will continue to play an important role in the development of medical
content on the Web. Content, architecture, and design are seamlessly tied when
developing Web-based medical communications. The medical illustrator should be
an expert on the subject matter or content being developed, the architecture
of that content, and the instructional and graphic design.
With new CT scanning technology and affordable graphic workstations,
illustrators now have access to 3D volume-rendered radiologic images as an
anatomic reference [4,
5] (Fig.
4A,4B,4C).
Illustrators have routinely used anatomy atlases of conventional cadaveric
illustrations as their sole reference. Analysis of illustrated anatomic
references alone may be inadequate for ensuring anatomic accuracy
[6]. Three-dimensional
volume-rendered images are a useful, clear, and accurate reference of in vivo
human anatomy and reduce the need to use purely illustrated and cadaveric
anatomy as the only reference for medical illustration. Illustrators need to
pay careful attention to the accuracy of 3D images. Although the pathways and
branching of vasculature may be correct, the vessel size may be distorted
depending on the 3D rendering method and parameters used. Imaging technology
continues to improve (e.g., multidetector CT), providing biocommunicators
access to new and improved imaging tools. Computers make it easy to adapt
these radiologic images into actual illustrations, which was once difficult if
not impossible to do with purely traditional illustration methods.
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Fig. 4B. —Volume-rendered CT images and computer-rendered medical
illustration. Three-dimensional volume-rendered CT reference of transplanted
kidney shows anastomosis of renal and iliac veins. Traditional sketch was
drawn from printed reference and then scanned for rendering on computer.
(Reprinted with permission from
[4])
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Fig. 4C. —Volume-rendered CT images and computer-rendered medical
illustration. Computer-rendered illustration shows position of kidney after
transplantation into pelvic region. This figure also shows use of combination
of computer software to create electronic image that looks like traditionally
rendered illustration. (Reprinted with permission from
[5])
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Applications of 3D volume-rendered images in medical illustration are
useful beyond the scope of anatomic reference. These images can be used as
anatomic templates or backgrounds for a medical illustration. Volume-rendered
images can be saved as tagged image file format (TIFF) files on the
workstation and then opened in a graphics program in which they can be used as
part of an illustration or multimedia project. These images can be animated,
colorized, texturized, or painted over.
These 3D volume-rendered images may also be used to form multilayered
illustrations, allowing the user to interactively view, hide, or combine each
layer. A multilayer illustrated image may show diagnostic images in layers
with different opacities, show or hide different label layers, or allow
different layers of illustration to either show through or obscure the
diagnostic images [7]. These
image layers could be viewed with a wide variety of applications, including
QuickTime Virtual Reality (Apple Computer), or be used with a Web-based
interactive multimedia application to expose or hide image layers. QuickTime
Virtual Reality interactive movies can be developed using the QuickTime VR
Authoring Studio (Apple Computer).
Conclusion
With many recent changes resulting in faster and more powerful computer
hardware and improved software, illustrators have electronic tools they could
only have dreamed about 5 years ago. Computers allow medical illustrators
greater flexibility and speed when creating and editing most medical
illustration and multimedia products. The newly available tools and
illustration methods have resulted in a new approach to research, creation,
and reproduction of medical art and have forever changed the traditional style
and presentation of medical art. In the future, these tools will allow the
illustrator to provide the client with a variety of types and styles of
communication products. What was previously illustrated as a simple textbook
diagram will be a clear and elegant animation or interactive multimedia
product.
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Abstract
Introduction
