Sensors and Actuators A 126 (2006) 328–334

TrEndo, a device for tracking minimally invasive surgicalinstruments in training setups

Magdalena K. Chmarra, Niels H. Bakker, Cornelis A. Grimbergen, Jenny Dankelman∗Man–Machine Systems Group, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Delft, The Netherlands

Received 28 June 2005; received in revised form 18 October 2005; accepted 27 October 2005Available online 29 November 2005

Abstract

A novel, four degrees of freedom, low-cost device for tracking minimally invasive surgical instruments (MIS) in training setups was developed.This device consists of a gimbal mechanism with three optical computer mouse sensors. The gimbal guides the MIS instrument, while opticalsensors measure the movements of the instrument. To test the feasibility of using optical mouse sensors to track MIS instruments, the accuracy ofthese sensors was tested depending on three conditions: distance between lens and object, velocity of movements, and surface characteristics. Theresults of this study were used for developing a prototype—TrEndo.

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Tests performed on TrEndo show that the smallest movement that can be recognized by sensors is 0.06 mm for translation and 1.27◦ for rotationf the MIS instrument around its axis. The smallest recognized angle for rotation around incision point is 0.23◦. The accuracy of TrEndo is high

han 95%, and therefore allows tracking the movements of the MIS instrument.2005 Elsevier B.V. All rights reserved.

eywords: Optical sensor; Gimbal; Minimally invasive surgery; Training; Instrument tracking; Objective assessment

. Introduction

Minimally invasive surgery (MIS, endoscopic surgery) is per-ormed using special long instruments that are inserted into theatient’s body through small incisions in the skin. Visual feed-ack of the operating area is obtained by an endoscopic camera,hich provides a 2D image on a monitor. MIS is thus a difficulturgical technique and it takes a relatively long learning curve toaster it fully[1]. To guarantee safe use of instruments, trainingf the operative skills is very important.

Training can be applied in box-trainers, virtual reality trainersVR trainers), animal experiments, and in patients[2–4]. In allonfigurations, objective assessment of a trainee’s skills remainschallenge. Presently, there is no widely used automatic method

o evaluate technical MIS skills during training[5–7]. Mostly, thessessment requires a lot of the teacher’s effort and is subjective

8–11].Most VR trainers provide a scoring system based on infor-

ation about the movements of the instruments[12–15]. They

also provide a database of the previously performed exerwhich can be used for motivating trainees. Unfortunately,trainers do not provide natural instrument–tissue interactionthey do not allow using standard MIS instruments (e.g. graor scissors). To be able to automatically rate surgical pemance in a training setup that uses standard MIS instrumedevice for tracking these instruments is required. Devices aable on the market that can track and record movementsMIS instruments are complex and expensive, some of themthe freedom of movement, and most of them are intendedused in VR environments only[16–19]. The aim of this study ito develop a simple and low-cost device that allows free maulation of a standard MIS instrument either in a box-trainerVR trainer and that tracks its movements.

2. Requirements

The design of a low-cost interface device that tracks the mments of MIS instruments should meet the following requments:

∗ Corresponding author. Tel.: +31 15 27 85 565; fax: +31 15 27 84 717.E-mail address: j.dankelman@wbmt.tudelft.nl (J. Dankelman).

1. Realistic manipulation of the MIS instrument in four degreesof freedom (DOFs): translation of the instrument along its

924-4247/$ – see front matter © 2005 Elsevier B.V. All rights reserved.oi:10.1016/j.sna.2005.10.040

M.K. Chmarra et al. / Sensors and Actuators A 126 (2006) 328–334 329

axis (1st DOF), rotation of the instrument around its axis(2nd DOF), left–right (3rd DOF) and forward–backward(4th DOF) rotations of the instrument around the incisionpoint.

2. Possibility to use with real MIS instruments (Ø 5 mm) in abox-trainer with or without combining with virtual realityenvironments.

3. The level of accuracy and sensitivity suitable to allow reliableassessment of trainees.

4. Low-cost and easy to produce to make a training facilityaffordable for every (training) hospital or private use.

5. “Plug-and-play” in PC – ready to use.6. Small size – in order to be easily carried and mounted, e.g.

on a box-trainer; it should fit on an average work desk.

Based on these requirements, a prototype of the device wasdeveloped.

3. Prototype of the tracking system—TrEndo

The main principle of the developed prototype for trackingMIS instruments – TrEndo – is to mimic the incision (pivoting)point by a gimbal mechanism and to track the movements ofthe instrument by means of optical sensors. The gimbal is asimple mechanism that allows the desired degrees of freedom.The optical sensors are the same as those used in a computerm

3

wo-a sora inT isma uced

F MISi e MISi of thei unteo rdingm le ringS

by designing a rectangular rigid body – inner ring – with acylindrical hole. In this hole, standard MIS instruments (∅5 mm) can be inserted, retracted, and rotated in any way thatis possible during MIS (Requirements 1, 2). The middle ringallows the left–right rotation of the inner ring (3rd DOF). Theouter (U-shaped) ring allows forward–backward rotations ofthe middle ring with the instrument (4th DOF). The maximumallowable angles in sideways directions are approximately±70◦.

3.2. Optical sensors

Optical computer mouse sensors enable the contactless mea-suring of the movements of standard instruments in TrEndo. Inthe rectangular rigid body of the gimbal mechanism two sensorsare placed. Sensor 1 measures movements of the MIS instrument(translation along and rotation around its own axis—1st and 2ndDOFs). Sensor 2 is facing a fixed semicircular surface placed onthe middle ring and measures rotations of the inner ring (3rdDOF). Sensor 3 is located on the outer ring of TrEndo. This sen-sor is facing the second fixed semicircular surface placed on themiddle ring and measures the rotations of the middle ring (4thDOF).

In Fig. 2, a schematic drawing of an optical mouse sensorsystem is presented. The sensor measures changes in positiono ith as e( itals hesei eamo r of“ SP iss ed toa ystemi

set pro-d se isa Thec man-a entso ing,c easy(

e tob nt 3i

F( sy ofA

ouse, being thus cheap and easily available.

.1. Gimbal mechanism

TrEndo (Tr, tracking; Endo, endoscopy) consists of a txis gimbal mechanism in which three optical mouse senre incorporated (Fig. 1). The role of the gimbal mechanismrEndo is to guide the MIS instrument. The gimbal mechanllows four DOFs. The 1st and the 2nd DOFs are introd

ig. 1. TrEndo—a prototype of a device for tracking the movements of thenstrument. Sensor 1 tracks the insertion-retraction, and the rotation of thnstrument around its own axis. Sensor 2 tracks the left–right rotationsnstrument by recording movements of a semicircular surface (SCS 1) mon the middle ring. Sensor 3 tracks forward–backward rotations by recoovements of another semicircular surface (SCS 2) mounted on the middensor 3 is located on the outer ring.

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d

.

ver a flat surface by taking surface pictures (frames) wmall CCD chip at high frame rate[20,21]. Images of the surfacFig. 3) are acquired via lens and illumination system. A digignal processor (DSP) by correlation determines from tmages the direction and the magnitude of motions. A strf x and y relative displacement values (given in numbesensor counts” that the camera sees) generated by the Dent to the serial peripheral interface. This signal is convertUSB-signal, which means that optical mouse sensors s

s “plug-and-play” (Requirement 5).Thelow-cost andready to use requirements are met becau

he gimbal mechanism is easy to manufacture and theuction costs are low. Furthermore, the computer moun inexpensive and very common computer input device.ompact appearance of the sensors keeps the devicegeable and portable (Requirement 6). Finally, the elemf the device, such as print circuit board (PCB) housan be designed in such way that the production isRequirement 4).

The accuracy and the sensitivity of the prototype have investigated in order to find out whether Requireme

s met.

ig. 2. Schematic drawing of the optical mouse. PCB, print circuit board[21]©Agilent Technologies, Inc., 2003; reproduced with permission, courtegilent Technologies, Inc.).

330 M.K. Chmarra et al. / Sensors and Actuators A 126 (2006) 328–334

Fig. 3. Example of what the optical mouse sensor sees on a surface (res-olution 16× 16 pixels). Details from top left image are compared withdetails from left down image. The differences in positions between imagesgive information about the position of the mouse. In this case, the mouseis moving down to the right (from: Logitech, The MXTM Optical Engine,http://www.ellenperry.com/logitechepd/i tech.html).

4. Methods

4.1. Tests of the optical sensor

Before the prototype was developed, several conditions thaaffect the accuracy of the optical sensor were investigated. Fothis reason, a series of tests using a standard optical computer mouse sensor, comparable to the smallest available opticmouse sensor (Agilent ADNS-2620), were carried out.

According to the specification of the manufacturer, theADNS-2620 sensor can track motions up to 12 in./s (305 mm/s[21]. Default resolution of the ADNS-2620 sensor is approx-imately 400 counts/in. (16 counts/mm). This means that the

smallest measured displacement is 65�m. However, the res-olution of the sensor changes when the conditions under whichthe sensor works change[21]. The following conditions wereinvestigated:

• the distance between lens and the tracked surface;• the velocity of the movements;• the surface characteristics of the tracked object.

These conditions were tested using the measuring setupshown inFig. 4. A computer-driven CNC milling machine wasused to accurately control the position of the sensor inx, y, andzdirections (up to 1�m). The milling machine also allows makingmovements with different velocities during the measurements.The sensor was mounted on the arm of the milling machine andmoved 50 mm forward and backward (movement from point Ato B to A). In the ideal situation, the optical sensor measures thesame movement in both directions. In reality, however, this doesnot occur. During this study the relative error is calculated as:

Error = ddif × 100

dtotal(%) (1)

whereddif is the difference between the initial and return positionmeasured by the sensor given in sensor counts anddtotal is thewhole measured distance in sensor counts.

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400,

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ig. 4. Measuring setup for testing the optical sensor. The left picture pras mounted. The right picture presents a more detailed view.

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All tests were repeated five times and data from the seere recorded on a PC with a sample frequency of 10 Hz.

.1.1. Test: distance lens–objectIn order to find the optimal distance lens–object, the dist

etween tracked surface and lensz was changed within the ran.2–4.5 mm. The velocity of the movements during all measents was 1000 mm/min. A sand paper with 1000 parts/in.2 wassed as tracked surface.

.1.2. Test: velocity of movementsTests were performed for five different velocities: 200, 5

000, 3500, and 6000 mm/min. The distance lens–objec

ts the arm of the computer-driven CNC milling machine, on which the opcal senso

M.K. Chmarra et al. / Sensors and Actuators A 126 (2006) 328–334 331

2.4 mm. Sand paper with 1000 parts/in.2 was used as trackedsurface.

4.1.3. Test: surface characteristicsFour different groups of surfaces were investigated: differ-

ent metals (aluminium blasted with glass beads, stainless stealblasted with glass beads, and sandblasted brass), sand papers(2000, 1000, 400, 240, and 40 parts/in.2), one-colour prints, andtwo-colour prints (printed on the laser printer). The distancelens–object was 2.4 mm and the velocity of movements was1000 mm/min.

4.2. Tests of the TrEndo tracking system

To keep the TrEndo device as small as possible, the smallestavailable optical sensors – Agilent ADNS-2620 – were used.The size of the ADNS-2620 footprint is 10 mm× 12.5 mm. Asreferred in Section4.1, the sensor’s resolution depends on dif-ferent factors (e.g. distance lens–object, velocity of movements,surface characteristics)[21]. The calibration of every sensor inTrEndo is thus necessary.

A special print circuit board and a base plate were designedso that they were smaller than those in the original Agilentdesign. The USB controller was separated from the sensor part(including the optical sensor, lens, and the necessary electricalc oveda andt ed fora costsl

after1 s af sure-m urnedo seda in theP

mmd ted tot ove-m stiffb ableo

thed

4and

5 and6

4ties:

1 ter-c l-y

Fig. 5. A schematic view of the measuring setup for tests described in Sections4.2.1–4.2.4. (1) Arm of the milling machine, (2) universal joint, (3) instrument,(4) tracking system, (5) stiff box, and (6) table of the milling machine.

4.2.3. Test: 3rd DOF (left–right)The instrument was rotated in left–right direction around the

incision point. Movements of 22◦ were applied for velocities:2000, 4000, and 6000 mm/min.

4.2.4. Test: 4th DOF (forward–backward)The left–right rotation of the instrument around the incision

point was evaluated in the same way as the left–right rotation.All tests were repeated 20 times. During performing these

tests, all three sensors were continuously turned on. Normally,the Windows System does not distinguish between multiplepointing devices at the application program level (which meansthat all pointer devices control the same cursor). During our testswe needed to differentiate signals from three mouse sensors inorder to deliver the right information to the computer. Therefore,we used a CPNMouse driver and application programming inter-face (API)[22,23] to write a computer program for recordingdata from more than one pointing device – sensor – at the sametime. Data from all sensors were recorded on a PC with a samplefrequency of 100 Hz.

During tests of the prototype the relative errors were deter-mined in two ways: moving from point A to B (A–B) and frompoint A to B to A (A–B–A). The relative errors of the tests werecalculated by:

E(dX real − dX meas) × 100

w ly,f ndd B–A,r

ionso Endot wasp per-f itieso ativee latedm an bei thei error

omponents). The superfluous parts of the lens were remnd a smaller LED was used. The print circuit boards

he base plates were designed such that they can be usll three sensors in the prototype, keeping production

ow.Normally, optical mouse sensors go in a sleeping mode

s of no movement[21]. Getting the sensor awake takeew milliseconds delay, which causes errors during meaents. Therefore, the sleeping mode of the sensor was tff. Unfortunately, turning off the sleeping mode function cautemperature rise of the sensors. To prevent this, holesCB housing were necessary for cooling.During the tests the MIS instrument was simulated by a 5

iameter sandblasted brass stick. This stick was conneche arm of the milling machine. In order to guarantee free ments of the stick, the prototype was mounted on a high andox (Fig. 5). The box was clamped to the computer driven tf the milling machine.

To determine the accuracy and sensitivity of TrEndo forifferent movements the following tests were performed.

.2.1. Test: 1st DOF (translation)The instrument was translated along its axis 50 mm up

0 mm down, using three different velocities: 2000, 4000,000 mm/min.

.2.2. Test: 2nd DOF (rotation)The instrument was rotated around its axis with veloci

0, 30, and 60 rotations/min in both clockwise and counlockwise directions. A rotation of 360◦ was recorded and anased.

rror =dX real

(%) (2)

heredX real is the distance (A–B and A–B–A, respectiveor the test) in millimeters given by the milling machine aX measis the distance measured by the sensor (A–B and A–espectively, for the test) in millimeters.

To compute the distances in millimeters, the resolutf the sensors should be determined by a calibration. Tr

racks motions in four DOFs, so the calibration of sensorserformed independently for each DOF. Calibrations were

ormed on the first four tests and averaged over all velocf motion. The mean and the standard deviation of the relrrors were computed on the rest (16) of the tests. The calcuean errors and standard deviations for both types of tests c

nterpreted differently. The mean error of test A–B–A givesnformation about possible systematic errors. The mean

332 M.K. Chmarra et al. / Sensors and Actuators A 126 (2006) 328–334

of test A–B is caused by a sum of two effects: the same phe-nomenon that caused the mean error in test A–B–A, and the useof a wrong resolution. The standard deviation gives in both casesinformation about the random error.

5. Results

5.1. Results of the optical sensor

5.1.1. Test: distance lens–objectThe results of this test are presented inFig. 6. The relative

error was smallest when the distance lens–object was within therange 2.25–3 mm.

5.1.2. Test: velocity of movementsThe dependency of the sensor’s resolution on velocity is

small. The largest difference in measured number of sensorcounts while moving from A to B with different velocities wasless than 1%.

Fig. 7shows the results of velocity test. The test shows thatthe mean relative error increases with the velocity. The highestobtained error was for the highest velocity. During minimallyinvasive surgery a velocity of 6000 mm/min is achieved only

F lensa

Fig. 7. Relative error (mean± S.D.) as a function of the velocity of the move-ments.

when the surgeon pulls out the instrument from the patient’sbody. In the normal working range (velocity of movementsmaller than 6000 mm/min) the error is less than 0.5%.

5.1.3. Test: surface characteristicsThe results of surface characteristics test show that the small-

est errors were obtained for sandblasted brass, sand papers, andtwo-coloured prints. Therefore, a sand paper (400 parts/in.2) wasused as a surface for sensors 2 and 3 in the prototype. One-colourprints did not work at all. The reason is that the sensor measureschanges in position over a flat surface by taking images and in thecase of one-colour prints, every image taken by the camera looksthe same. So, the sensor does not recognize any movements onone-colour prints without texture.

5.2. Results of the TrEndo tracking system

Results of the prototype test are presented inTable 1.

TR

T nce A–Ba A–Ba A–B–Ab

Mean relative error± S.D. (%) Mean relative error± S.D. (%)

T m 2.56± 0.82 0.23± 0.52m −1.54± 0.74 0.01± 0.41m

C

L

F

ig. 6. Relative errors (mean± S.D.) as a function of the distance betweennd object.

able 1esults of testing tracking system

est Speed Dista

ranslationc 2000 (mm/min) 50 m4000 (mm/min) 50 m6000 (mm/min) 50 m

lockwise and counter-clockwise rotationd 10 (rpm) 360◦30 (rpm) 360◦60 (rpm) 360◦

eft–right rotationc 2000 (mm/min) 22◦

4000 (mm/min) 22◦6000 (mm/min) 22◦

orward–backward rotationc 2000 (mm/min) 22◦4000 (mm/min) 22◦6000 (mm/min) 22◦

a Tests A–B: movement from point A to B in the shortest possible way.b Tests A–B–A: movement from point A to B to A in the shortest possible wac Mean was calculated on 16 repeated tests.d Mean was calculated on 32 repeated tests.

−1.05± 0.83 −0.20± 0.95

1.27± 1.8 –−1.12± 2.04 –−1.71± 1.72 –

0.02± 2.11 −0.39± 1.58−0.24± 1.28 0.04± 1.10−0.50± 1.22 −0.30± 0.75

0.51± 0.10 −0.04± 0.76−0.42± 1.25 −0.25± 0.9

0.09± 1.40 0.21± 0.95

y.

M.K. Chmarra et al. / Sensors and Actuators A 126 (2006) 328–334 333

Fig. 8. Examples of results of tests A–B and A–B–A. Presented results A–B (left) and A–B–A (right) were performed for the translation of the instrumentalong itsaxis with velocity of 4000 mm/min. Each test was repeated 20 times.

5.2.1. Test: 1st DOF (translation)For the translation of the instrument along its axis the cal-

ibration resulted in a resolution of 17 counts/mm. This meansthat the smallest displacement that can be seen by TrEndo is60�m. The maximal mean error during translation was for testA–B and occurred for the lowest velocity (Table 1). Examplesof the results of tests are shown inFig. 8.

5.2.2. Test: 2nd DOF (rotation)For the rotation of the instrument around its axis the calibra-

tion resulted in a sensor resolution of 459 cpi. This means thatthe smallest rotation that can be observed by TrEndo is 1.27◦.

5.2.3. Test: 3rd DOF (left–right)During left–right rotation of the instrument around the inci-

sion point no clear relation between velocity and error was found.Mean relative errors of test A–B are small (less than 0.5%). Thecalibration for this test resulted in a sensor resolution of 475 cpi.This means that the smallest angle recognized by TrEndo inleft–right direction is 0.22◦.

5.2.4. Test: 4th DOF (forward–backward)The test results for forward–backward rotation of the instru-

ment around the incision point do not show any trends. Thecalibration for this test resulted in a sensor resolution of 535 cpi.This means that TrEndo recognizes angles bigger than 0.23◦ inf

6

vice( ISs at thf wert

1 ect;23

d inT ana

The design based on the combination of the gimbalmechanism with three optical mouse sensors results ina simple and inexpensive system, which can follow andrecord movements of the standard MIS instrument in fourDOFs.

During performing MIS, small movements in the incisionpoint can result in large movements of the tip of the MIS instru-ment. Therefore, sensors that record instrument’s movements atthe incision point should be able to recognize small movements.The smallest movement in 1st DOF (translation of the instrumentalong its axis) that can be recognized by the sensor in TrEndois 0.06 mm. The smallest angle in 2nd DOF (rotation of theinstrument around its axis) that can be recognized by TrEndo is1.27◦. These results were obtained using a 5 mm diameter sand-blasted brass stick. Normally, the surface of MIS instruments isshiny and black. Therefore, modification of this surface is nec-essary. This can be easily done by roughing the surface withsand paper.

Additionally, the diameter of standard MIS instrumentsdoes not always equal 5 mm. For example the diameter ofan endoscopic camera equals 10 mm. Moreover, many timesthe diameter of MIS instruments is not constant over thewhole working length of the instrument. This could affect themeasurements of the movements because the resolution ofthe sensor depends on the distance lens–object. A solution tothis problem can be to design a tube, in which the instrumentw ace,n thep sings of thet ent,s yT

ithv tiono ces-s saryo

cesb geons[ highe

orward–backward direction.

. Discussion

The objective of this study was to design and build a deTrEndo) that tracks MIS instruments during training of Mkills. The tests of the optical mouse sensor have shown thollowing characteristics give the smallest errors (totally lohan 5%):

. a distance of 2.25–3 mm between lens and tracked obj

. a velocity of movements up to 5000 mm/min;

. a rough surface or a patterned surface.

Furthermore, results of the prototype test (presenteable 1) show that errors are smaller than 5%, resulting inccuracy of more than 95%.

e

ill be placed and fixed. If this tube has a rough surfo modification of the instrument surface to improveerformance of the sensor will be needed. Moreover, uuch a tube has one more advantage; since the diameterube will be bigger than the diameter of the MIS instrummaller angles than 1.27◦ in the 2nd DOF will be recognized brEndo.

Under different conditions the optical sensors track warying resolution. To avoid these difficulties, a calibraf the device before using it in a training setup is neary. Our results indicate that this calibration is only necesnce.

In the literature we found that there are large differenetween trajectories of experienced and inexperienced sur

24]. Hence, the sensitivity of the device is expected to benough.

334 M.K. Chmarra et al. / Sensors and Actuators A 126 (2006) 328–334

7. Conclusions

A novel low-cost tracking device that can be used duringtraining of minimally invasive surgical skills – TrEndo – wasdeveloped. This device allows free manipulation of standardMIS instruments in a training setup, such as box and virtual real-ity. Due to the use of optical sensors from a computer mouse,TrEndo is simple to use and gives easy access to the computer viaa standard USB port. The experiments show that MIS instrumentcan be accurately tracked by the system.

Acknowledgements

The authors would like to thank Medical Technology Devel-opment department from Academic Medical Center Amsterdamfor help in designing and manufacturing of the prototype.

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Biographies

Magdalena K. Chmarra was born in Warsaw, Poland, in 1975. She receivedher MSc degree in mechatronics from the Warsaw University of Technologyin 2002, with specialisation in biocybernetic and biomedical engineering.She is currently a PhD student at Man–Machine Systems Group, Faculty ofMechanical, Maritime, and Materials Engineering at the Delft University ofTechnology. Her research concerns training and assessment of the technicalskills in minimally invasive surgery.

Niels H. Bakker was born in Dormaa Ahenkro, Ghana, in 1969. After obtain-ing his MSc in mechanical engineering at the Delft University of Technologyin the Man–Machine Systems Group in 1995 he worked for a year as researchscientist at the Department of Transportation and Logistic. In 1996, he starteda four-year PhD project in mechanical engineering in cooperation with theTNO Human Factors Research Institute resulting in a degree in February2001. From 2001, he worked as a postdoc at the Medical Technology Groupo g asa

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objective, Br. Med. J. 318 (1999) 887–888.[9] J.A. Martin, et al., Objective structured assessment of technical

(OSATS) for surgical residents, Br. J. Surg. 84 (1997) 273–278.10] K. Moorthy, et al., Objective assessment of technical skills in sur

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ings of the International Workshop on Medical Imaging and AugmeReality (MIAR’01), 2001, pp. 5–9.

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13] A.G. Gallagher, et al., Objective psychomotor skills assessment ofrienced, junior, and novice laparoscopists with virtual reality, WorSurg. 25 (2001) 1478–1483.

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Procedures, United States Patent Number 6,654,000 B2.

-

-

-

f the Academic Medical Centre in Amsterdam. Currently he is workinclinical scientist at Philips Medical Systems in Best.

ornelis A. Grimbergen was born in Leiden, The Netherlands, in 19fter receiving his Ir. degree in electrical engineering at the Delft Univef Technology he was active in research in solid-state physics, semuctor technology, resulting in a PhD degree in 1977 from the Univef Groningen. From 1977, he has been with the Laboratory of Mehysics of the Faculty of Medicine of the University of Amsterdam w

ng as an assistant professor. From 1991, he is a part-time profeshe Measurement & Control Department of the Faculty of Mechaniche Delft University of Technology. From 1995, he is also professoedical Technology at the Academic Medical Center of the Universitmsterdam (AMC). His interests and research projects are in thef medical image processing, minimally invasive techniques and safet

raining.

enny Dankelman was born in Ommen, The Netherlands, in 1961.btained her degree in mathematics, with specialisation in system and cngineering, in 1984 at the University of Groningen. Her PhD degreebtained in 1989 at the Man–Machine Systems Group, Faculty of Mechaaritime, and Materials Engineering, Delft University of Technology (Dn her research of the dynamics of the coronary circulation. This workerformed in close co-operation with the Department of Medical Physi

he Academic Medical Center, University of Amsterdam. She continueesearch on the coronary circulation for 3 years as postdoc at both univeince 1992, she is researcher at Man–Machine Systems Group, DUince 2001 professor in biomedical engineering. Her interests and rerojects are in the fields of medical instruments, patient safety, and min

nvasive techniques.