WEB-BASED

'COMPUTER ASSISTED SURGICAL ANATOMY MAPPING'

A. L. A. Kerver, G-J. Kleinrensink

Department of Neuroscience and Anatomy, Erasmus University, ‘s-Gravendijkwal 230, Rotterdam, The Netherlands

N. N. Smit, S. Rabbelier, B. M. W. Sedee, C. P. Botha

EEMCS, TU Delft, Mekelweg 4, Delft, The Netherlands

Keywords: Surgical Complications, Pre-operative Planning, Surgical Education, Computer Assisted Surgical Anatomy

Mapping, Medical Visualisation, VTK, Django.

Abstract: In surgery one of the major problems is a safe approach of the operation site. For surgeons it is paramount to

know the location of surgically relevant nerves and vessels. Especially in surgery of the lateral (outside)

foot, the anatomy is not always completely clear since the location of nerves and vessels is highly variable.

Therefore CASAM is developed by students in Delft and Rotterdam (Netherlands). This web-application is

based on the Django-framework and is a useful tool for three usergroups: 1) Researchers: After

photographing dissected specimen a Thin Plate Spline transformation is used to compute an average foot

and the pictures of individual specimen are warped to match this reference, average-foot. Renditions can be

made to depict relevant surgical anatomy. Finally the researchers can define a zone in the lateral foot in

which it is safe to approach the operation site. 2) Surgeons: Relevant anatomy (gathered by the researcher)

can be warped over the picture of the patient. This pre-operative planning using CASAM assists the surgeon

in determining a ‘tailor made’ safe-zone for each patient. 3) Students: For educational purposes, a drawn

incision line can be compared to the computed location of nerves and vessels, thus providing personal

feedback.

1 INTRODUCTION

In surgery one of the major problems is the safe

approach of the operation site. Exposure of this

operation site is the most important aspect but tissue

sparing is just as important. In order to make a good

evaluation between exposure and tissue sparing the

knowledge of the related human anatomy is of

paramount importance. For surgeons though, it is

impossible to exactly know the anatomy of the

complete human body mainly because:

1) There is an enormous inter- and intra-

individual variety in human anatomy. The

location of nerves, arteries and veins differs

between each patient.

2) Since the dimensions of each specimen are

different (shape, size, length width, etc) it is

impossible to compare the anatomy of

different specimen.

3) As new techniques are being developed to

lessen complications the surgical procedures

themselves often become more complex.

4) Some surgical procedures are very rare and a

surgeon only does three or four of them per

year.

Iatrogenic damage to nerves and vessels and hence

postoperative pain and poor wound healing are a

very common complication in surgery. To avoid

damage of nerves and vessels it is imperative for a

surgeon to know the exact location of important

anatomical structures.

In order to overcome (some of) these problems,

researchers at the Erasmus Medical Centre in

Rotterdam began to map the human anatomy related

to the 25 most current surgical procedures. In

cooperation with the Delft Technical University:

Faculty of Electrical Engineering, Mathematics and

Computer Science; dept. of medical and data

visualisation (head: Dr. C. Botha/ Dr. F.H. Post), a

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L. A. Kerver A., Kleinrensink G., N. Smit N., Rabbelier S., M. W. Sedee B. and P. Botha C.

WEB-BASED ’COMPUTER ASSISTED SURGICAL ANATOMY MAPPING’.

DOI: 10.5220/0002858102440247

In Proceedings of the 6th International Conference on Web Information Systems and Technology (WEBIST 2010), page

ISBN: 978-989-674-025-2

web-based tool was developed. The main focus of

the tool was to be able to compare the anatomy of

different specimen and relate it to a specific patient.

Also, the application needed to be fast, user friendly

and scientifically verifiable. Finally it needed to be

easily accessible for our three main focus groups:

researchers, surgeons, and surgical residents.

Many surgeons have dreamed of a

preoperatively, real time available and easily

accessible database to compare their patients to. The

current web-based system tries to make a step

forward in having this kind of database.

2 APPLICATION

One of the surgical procedures that illustrates these

problems is the lateral (outside) approach of the

calcaneus (heel bone) for fractured ankles. Up to

15% post-operative pain due to damage of the

nerves and up to 10% wound necrosis due to damage

of the arteries is reported (Poeze, 2008). As a

fracture of the calcaneus is rare (Barei, 2000)

surgeons on average only perform four of these

surgical procedures per year.

2.1 User Groups

This application can benefit three user-groups:

2.1.1 Researchers

A Thin Plate Spline transformation is used to project

each picture of each individual specimen to match a

reference, average-foot. Renditions can then be

made to depict the relevant surgical anatomy (figure

1). As an additional feature, the Point Distribution

Model can display variations within anatomical

structures. Using these tools the members of our

CASAM research project group can define a zone in

the lateral foot in which it is safe to approach the

operation site.

2.1.2 Surgeons

A simplified intuitive version of the web-application

allows the surgeon to upload a picture of the ankle

of his specific patient, after which he can warp the

relevant anatomy (provided by the CASAM research

group) over the picture of his patient (figure 1). In

this way the surgeon has an easily accessible

database at his disposal to optimise his pre-operative

planning and determine a ‘tailor made’ safe zone in

each patient.

Figure 1: A patients lateral ankle depicting the surgically

relevant anatomy of ten dissected sural nerves and six

posterior tibial arteries.

2.1.3 Surgical Residents

Another version of the web-application allows the

resident/student to upload a reference picture (for

example real time, during an anatomy course) of a

drawn incision line. Then, for educational purposes,

this incision line can be compared to the gold

standard or the computed location of nerves and

vessels, thus providing personal feedback and hence

making his /her learning curve steeper (figure 1 and

figure 2).

Figure 2: CASAM-generated image, depicting an average

leg in which 43 incisions drawn by 23 surgeons were

evaluated. Red area: Incisions that were marked as

‘wrong’ (N=32). Green area: Incisions that were marked

as ‘good’ (N=9).

Within each of these groups rights can be assigned

to different users, to allow access to specific projects

for specified users only. Also it is possible to

differentiate between 'read-write' and 'read-only'

WEB-BASED 'COMPUTER ASSISTED SURGICAL ANATOMY MAPPING'

245

access. A time-out for inactivity prevents

unauthorized use of the data.

2.2 Features

Our software enables users to do their work in an

efficient and intuitive manner. After log-in the user

is presented with available projects (figure 3).

Figure 3: The project selection screen in the web interface.

After selecting a project the main work area is

shown where the user can view and edit (only when

permitted) existing data or add new data (figure 4).

Implemented features include:

Figure 4: The web-interface work-area for researchers.

Adding tags to projects for easy project reference;

 Adding relevant scientific papers and URLs to

projects;

 Fast adding and editing of shape-defining and

anatomical landmarks;

 Accurate landmark-placement with the zoom-

function;

 Transparency sliders for layered viewing and

comparing of multiple images and overlays;

 Drawing bitmap overlays in any color to

highlight structures of interest;

 Saving compositions of images, landmarks and

bitmaps as states;

 Exporting project data to a zip- or CSV-file.

3 IMPLEMENTATION

3.1 Technologies

At the heart of this project Python, the Visualization

Toolkit (VTK) and Python Imaging Library (PIL)

were used for the required image processing

techniques. Also the Web framework Django was

used. Its Object-relational mapper allowed to define

our datamodels in Python and allow for dynamic

database-access. The built-in automatic admin

interface saved a lot of work. The present

application also uses JavaScript and two JavaScript

frameworks: Scriptaculous for some visual effects

and Prototype for easy class-driven development and

Ajax. For the webpage itself HTML and CSS was

used. For the drawing application Flash was used.

Django was extensively used, especially its

database and templating capabilities. This allowed

for testing using a simple SQLite Database, whilst

MySQL was used when deploying the system on a

server. Another advantage of Django's database

features is that no SQL queries had to be written,

since Django handles these. This made it possible to

write expressive queries, whose purpose is clear

from looking at them. Django's templating system

made it easy to separate the HTML code from the

Python code. This results in a separation between

logic and presentation, which is considered to be

good coding practice.

The use of JavaScript makes our system highly

interactive. Prototype allowed for creating a number

of different classes within this system, so that users

could be allowed to easily drag-and-drop the

different landmarks, change the order of the

different images, and even undo the (re)placement of

the landmarks. Prototype also allows for easy access

to Ajax-calls, so that most changes can be stored in

the database, through the use of Django's mapper,

without the users noticing it.

3.2 Image processing

The first feature is a calculation of the Point

Distribution Model (PDM), as developed by Tim

Cootes, given a set of landmarks. This is a part of

the Active Shape Model Cootes developed (Cootes,

2000). This model gives an overview of the average

positions of the landmarks and local variations.

The second feature is an improvement of the

original morphing technique. By defining several

shape defining landmarks (for example, bony

landmarks: anatomical landmarks that are palpable)

per specimen all the drawn overlays can be morphed

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to the selected specimen, which serves as a 'gold

standard specimen'. The morphing is done using a

Thin Plate Spline (Bookstein, 1989) transformation.

The end result is an image of the target specimen

and the drawn overlays of other specimens morphed

to the target specimen.

3.3 Exporting Data

Lastly, an export feature is provided, which makes it

possible to export all data from the system into an

archive. This archive can then be backed up to disk,

and restored later in the event of a disk failure or

similar. These imports can also be restored on

another system, allowing for an easy way to

exchange data between different researchers.

Additionally, a method is provided to export

landmarks as a comma separated value (CSV) file,

which enables other researchers such as statisticians

to work with the data.

4 DISCUSSION

All variations of a nerve or vessel cannot be

mapped, as this would require an immense number

of human specimen. Therefore CASAM cannot

provide a definitive safe-zone. It can however make

the range for safe approach to the surgical area more

precise and hence decrease the occurrence of

postoperative pain and wound management

problems due to unintended iatrogenic lesions of

nerves and vessels

As the CASAM method relies on extended

image adjustments and computer calculations it is

not 100% accurate. However, the CASAM method

proved to be a great asset to visualize the complex

anatomy and can be used in addition to conventional

means of anatomy data gathering.

In this paper, the surgically relevant anatomy of

the lateral (outside) foot and the surgical approach to

the calcaneus were used as an example of the

successful use of the application. The CASAM

method, however, can be very useful for any 2D

anatomy research.

At the moment the website with the CASAM

database is improved to be more user-friendly and

easily accessible to surgeons and residents around

the world. Currently, several projects are performed

to extend CASAM to a tool used for 3-D anatomy

mapping .

5 CONCLUSIONS

The web-based CASAM method can prove to be a

great asset to visualize the complex anatomy of the

human body and can be used in addition to

conventional means of anatomy data gathering. The

gathered data is also more applicable for surgeons

than the current situation. The data can easily be

related to an individual patient and ‘tailor made’ safe

zones and advised incision lines might prove to

lessen surgical complications. Students might

benefit from more accurate safe zones and personal

feedback on drawn incision lines might reduce the

learning curve of modern complex surgeries.

Several improvements are planned for the web-

application. Features we are still working on

include:

 Compatibility with file formats other than

JPEG;

 Use of multiple colors in one image in the

drawing application;

 Replacing the Flash drawing application with a

canvas implementation;

 Storing statistical data with landmarks;

 Measuring distances within images;

 Creating new graphical user interfaces for

surgeons and students;

 Multi-level zooming.

 Verification of all anatomical data in embalmed

specimen.

 Determine the clinical significance and

functionality of the CASAM system.

REFERENCES

Barei, D.P., 2000. Fractures of the calcaneus. Orthopedic

Clinics of North America 2000

Poeze M, Verbruggen JP, Brink PR. The relationship

between the outcome of operatively treated calcaneal

fractures and institutional fracture load. A systematic

review of the literature. J Bone Joint Surg Am. 2008

May;90(5):1013-21.

Bookstein, F.L., 1989. Principal warps: Thin-plate splines

and the decomposition of deformations. In IEEE

Transactions on pattern analysis and machine

intelligence 11-6.

Cootes, T., 2000. An introduction to active shape models.

In Image Processing and Analysis. Oxford University

Press.

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