C. A. Grimbergen

Systems for tracking minimally invasive surgical instruments

Minimally invasive surgery (e.g. laparoscopy) requires special surgical skills, which should be objectively assessed. Several studies have shown that motion analysis is a valuable assessment tool of basic surgical skills in laparoscopy. However, to use motion analysis as the assessment tool, it is necessary to track and record the motions of laparoscopic instruments. This article describes the state of the art in research on tracking systems for laparoscopy. It gives an overview on existing systems, on how these systems work, their advantages, and their shortcomings. Although various approaches have been used, none of the tracking systems to date comes out as clearly superior. A great number of systems can be used in training environment only, most systems do not allow the use of real laparoscopic instruments, and only a small number of systems provide force feedback.

Software design for analysis of multichannel intracardial and body surface electrocardiograms

Analysis of multichannel ECG recordings (body surface maps (BSMs) and intracardial maps) requires special software. We created a software package and a user interface on top of a commercial data analysis package (MATLAB) by a combination of high-level and low-level programming. Our software was created to satisfy the needs of a diverse group of researchers. It can handle a large variety of recording configurations. It allows for interactive usage through a fast and robust user interface, and batch processing for the analysis of large amounts of data. The package is user-extensible, includes routines for both common and experimental data processing tasks, and works on several computer platforms. The source code is made intelligible using software for structured documentation and is available to the users. The package is currently used by more than ten research groups analysing ECG data worldwide.

Fundamental aspects of learning minimally invasive surgical skills.

With the introduction of minimally invasive surgery (MIS) the necessity to develop training methods to learn skills outside the operating room (OR) became clear. Several training simulators have become commercially available. However, fundamental research into the requirements for effective and efficient training in MIS is still lacking. Yet in the literature several learning models have been described that may be used when designing the structure of a training program. While learning skills, three stages can be observed: cognitive, associative and autonomous. The learning cycle also includes different learning styles and, moreover, every trainee has his/her preferred learning style. Furthermore, training should be adapted to the level of behaviour: skill‐based, rule‐based or knowledge‐based. Training of complex skills should include multiple performance objectives, such as just‐in‐time supportive information and part‐task practice. Finally, motivation for training can be created by assessment. In conclusion, several theories on learning can be found in the literature. These theories may help in the development of effective training programs for training MIS skills outside the OR.

The influence of experience and camera holding on laparoscopic instrument movements measured with the TrEndo tracking system

BackgroundEye–hand coordination problems occur during laparoscopy. This study aimed to investigate the difference in instrument movements between the surgeon him- or herself holding the camera and an assistant holding the camera during performance of a laparoscopic task and to check whether experience of the surgeon plays a role in this issue.MethodsThe participants were divided into three groups: experts, residents, and novices. Each participant performed positioning tasks using the right (R) and left (L) hands. During these tasks, the camera was manipulated either by the participant (Cself) or by an assistant (Cassistant). Movements of instruments were recorded with the authors’ new TrEndo tracking system. The performance was analyzed using five kinematic parameters: time, path length, three-dimensional (3D) motion smoothness, 1D motion smoothness (along the axis), and depth perception.ResultsA total of 46 participants contributed. Three tests were performed: test 1-LCself, test 2-LCassistant, and test 3-RCassistant. In all the tests, the experts performed better than the residents and novices in terms of time, path length, and depth perception. The novices performed better in tests 1-LCself and 2-LCassistant than in test 3-RCassistant in terms of path length, 3D motion smoothness, and depth perception.ConclusionsLaparoscopic experience and the camera-holding factor influenced the performance of laparoscopic tasks on the simulator. Time, path length, and depth perception clearly discriminate between different levels of experience in laparoscopy, whereas 3D and 1D motion smoothness play a limited role. Novices experienced more difficulties when an assistant held the camera. Therefore, self-manipulation of the camera seems to improve novices’ eye–hand coordination.

Quantitative in vivo analysis of the kinematics of carpal bones from three‐dimensional CT images using a deformable surface model and a three‐dimensional matching technique

The purpose of this study was to obtain quantitative information of the relative displacements and rotations of the carpal bones during movement of the wrist. Axial helical CT scans were made of the wrists of 11 volunteers. The wrists were imaged in the neutral position with a conventional CT technique, and in 15-20 other postures (flexion-extension, radial-ulnar deviation) with a low-dose technique. A segmentation of the carpal bones was obtained by applying a deformable surface model to the regular-dose scan. Next, each carpal bone, the radius, and ulna in this scan was registered with the corresponding bone in each low-dose scan using a three-dimensional matching technique. A detailed definition of the surfaces of the carpal bones was obtained from the regular-dose scans. The low-dose scans provided sufficient information to obtain an accurate match of each carpal bone with its counterpart in the regular-dose scan. Accurate estimates of the relative positions and orientations of the carpal bones during flexion and deviation were obtained. This quantification will be especially useful when monitoring changes in kinematics before and after operative interventions, like mini-arthrodeses. This technique can also be applied in the quantification of the movement of other bones in the body (e.g., ankle and cortical spine).

Systems approach to reduce errors in surgery

Reducing the number of medical errors significantly is the challenge for the coming decade. In medicine and in surgery, in particular, errors are traditionally treated as being committed by individuals. To reduce human errors, two approaches can be used: the person approach and the systems approach. In the systems approach, the operator is not blamed, but the system is analyzed in order to find the causes of errors. Furthermore, defenses are built into the system so that errors will not result in an adverse outcome anymore. This article aims to provide insight into the systems approach.

Camera and instrument holders and their clinical value in minimally invasive surgery.

During minimally invasive procedures an assistant is controlling the laparoscope. Ideally, the surgeon should be able to manipulate all instruments including the camera him/herself, to avoid communication problems and disturbing camera movements. Camera holders return camera-control to the surgeon and stabilize the laparoscopic image. An additional holder can be used to stabilize an extra laparoscopic instrument for retracting. A literature survey has been carried out giving an overview of the existing “robotic” and passive camera and instrument holders and, if available, results of their clinical value. Benefits and limitations were identified. Most studies showed that camera holders, passive and active, provide the surgeon with a more stable image and enables them to control their own view direction. Only the passive holders were suitable for holding instruments. Comparisons between different systems are reviewed. Both active and passive camera and instrument holders are functional, and may be helpful to perform solo-surgery. The benefits of active holders are questionable in relation to the performance of the much simpler passive designs.

Evaluation of Vascular and Interventional Procedures with Time–Action Analysis: A Pilot Study

PURPOSEnTo provide an objective method to measure the efficiency of vascular and interventional procedures.nnnMATERIALS AND METHODSnThe time-action analysis method is defined for peripheral vascular and interventional procedures. A taxonomy of actions is defined, geared specifically toward these procedures. The actions are: start-up/wrap-up, exchange, navigate, image, diagnose, treat, handle material, wait, compress puncture site, and unclassified. The recording method and analysis techniques are described. To show the type of data that can be obtained, the time-action analysis of 30 procedures is presented.nnnRESULTSnThe results provide a detailed picture of the time spent on various actions. Of all actions, the most time is spent on compressing the puncture site (18.5%), whereas the highest frequency of actions are for exchange of catheters, guide wires, and sheaths (20.4 times per procedure). Radiation exposure can be analyzed in detail, which can yield directions for possible reduction. For instance, 5.2%-8.3% of the total radiation exposure occurs during preparation of imaging to adjust the position of the patient table and set the image intensifier diaphragm.nnnCONCLUSIONnTime-action analysis provides an objective measurement method to monitor and evaluate vascular and interventional procedures. Potential applications and limitations of the technique are discussed.

Retracting and seeking movements during laparoscopic goal-oriented movements. Is the shortest path length optimal?

AimsMinimally invasive surgery (MIS) requires a high degree of eye–hand coordination from the surgeon. To facilitate the learning process, objective assessment systems based on analysis of the instruments’ motion are being developed. To investigate the influence of performance on motion characteristics, we examined goal-oriented movements in a box trainer. In general, goal-oriented movements consist of a retracting and a seeking phase, and are, however, not performed via the shortest path length. Therefore, we hypothesized that the shortest path is not an optimal concept in MIS.MethodsParticipants were divided into three groups (experts, residents, and novices). Each participant performed a number of one-hand positioning tasks in a box trainer. Movements of the instrument were recorded with the TrEndo tracking system. The movement from point A to B was divided into two phases: A-M (retracting) and M-B (seeking). Normalized path lengths (given in %) of the two phases were compared.ResultsThirty eight participants contributed. For the retracting phase, we found no significant difference between experts [median (range) %: 152 (129–178)], residents [164 (126–250)], and novices [168 (136–268)]. In the seeking phase, we find a significant difference (<0.001) between experts [180 (172–247)], residents [201 (163–287)], and novices [290 (244–469)]. Moreover, within each group, a significant difference between retracting and seeking phases was observed.ConclusionsGoal-oriented movements in MIS can be split into two phases: retracting and seeking. Novices are less effective than experts and residents in the seeking phase. Therefore, the seeking phase is characteristic of performance differences. Furthermore, the retracting phase is essential, because it improves safety by avoiding intermediate tissue contact. Therefore, the shortest path length, as presently used during the assessment of basic MIS skills, may be not a proper concept for analyzing optimal movements and, therefore, needs to be revised.

A novel approach to mammographic breast compression: Improved standardization and reduced discomfort by controlling pressure instead of force

PURPOSEnIn x-ray mammography, flattening of the breast improves image quality and reduces absorbed dose. Current mammographic compression guidelines are based on applying a standardized force to each breast. Because breast size is not taken into consideration, this approach leads to large variations in applied pressure (force applied per unit contact area). It is the authors hypothesis that a pressure-controlled compression protocol, which takes contact area into account, (1) improves standardization across the population in terms of physiological conditions in the compressed breast (blood pressure), and (2) reduces discomfort and pain, particularly the number of severe pain complaints, (3) with limited effects on image quality and absorbed glandular dose (AGD).nnnMETHODSnA prospective observational study including 291 craniocaudal (CC) and 299 mediolateral oblique (MLO) breast compressions in 196 women following the authors hospitals standard compression protocol with 18 decanewton (daN) target force was performed. Breast thickness, applied force, area of contact between breast and compression paddle, and mean pressure were recorded during the entire compression. Pain scores before and after breast compressions were obtained using an 11-point numerical rating scale (NRS). Scores of 7 and higher were considered to indicate severe pain. The authors analyzed differences between the CC and MLO compressions, correlation coefficients (ρ) between compression parameters, and odds-ratios (OR) for all parameters as possible predictors for experiencing severe pain using multivariate logistic regression. The observed data were used in two models to estimate what breast thickness, required force, and pain score would be for pressure-controlled compression protocols with target pressures ranging from 4 to 28 kilopascal (kPa). For a selection of 79 mammograms having a 10% or more thickness difference with respect to the prior mammogram, the authors performed a retrospective observer study to assess whether such thickness differences have significant effects on image quality or AGD.nnnRESULTSnIn a standard 18 daN force-controlled compression protocol, the authors observed an average pressure of 21.3 kPa±54% standard deviation for CC compressions and 14.2 kPa±32% for MLO compressions. Women with smaller breasts endured higher pressures and experienced more pain, as indicated by a significant negative correlation (ρ=-0.19, p<0.01) between contact area and pain score. Multivariate regression showed that contact area is a strong and significant predictor for severe pain (ORNRS≥7 (CC)=0.10/dm2, p<0.05), as is the case with any pain already present before compression (ORNRS≥7 (CC)=1.61 per NRS-point, p<0.05). Model estimations showed that mammographic breast compression with a standardized pressure of 10 kPa, corresponding with normal arterial blood pressure, may significantly reduce the number of severe pain complaints with an average increase in breast thickness of 9% for small breasts and 2% for large breasts. For an average 16.5% thickness difference in prior-current mammogram pairs, the authors found no differences in image quality and AGD CONCLUSIONS: Model estimations and an observer study showed that pressure-controlled mammographic compression protocols may improve standardization and reduce discomfort with limited effects on image quality and AGD.