Hans-Peter Meinzer

1.38

Impact points

Pitfalls of electromagnetic tracking in clinical routine using multiple or adjacent sensors.

Ingmar Wegner, Dogu Teber, Boris Hadaschik, Sascha Pahernik, Markus Hohenfellner, Hans-Peter Meinzer, Johannes Huber

The international journal of medical robotics + computer assisted surgery : MRCAS. 04/2012;

BACKGROUND: While electromagnetic tracking (EMT) holds great promise, there are substantiated concerns about interference within the clinical environment. The purpose of this study was to address accuracy and isolate pitfalls for using multiple or adjacent EMT sensors in clinical routine. METHODS: A... [more] BACKGROUND: While electromagnetic tracking (EMT) holds great promise, there are substantiated concerns about interference within the clinical environment. The purpose of this study was to address accuracy and isolate pitfalls for using multiple or adjacent EMT sensors in clinical routine. METHODS: A phantom simulating an EMT-guided puncture of the kidney was used to analyse the effects of multiple sensors in the direct vicinity, common clinical environments and the influence of endo-urological instruments. RESULTS: No relevant interference due to the investigated instruments was discovered. However, there was a great decrease in accuracy in the vicinity of a C-arm's image intensifier, especially affecting the precision of two adjacent sensors. CONCLUSION: Endo-urological instruments can be safely used for multi-sensor EMT-guided procedures. When avoiding the immediate proximity of the surgical table and the image intensifier, there is a comfortable accuracy corridor. Thus, EMT-assistance is promising for a wide range of procedures if basic conditions are met. Copyright © 2012 John Wiley & Sons, Ltd.

0.74

Impact points

Teaching on Three-Dimensional Presentation Does Not Improve the Understanding of According CT Images: A Randomized Controlled Study.

Rebecca Metzler, Daniel Stein, Ralf Tetzlaff, Thomas Bruckner, Hans-Peter Meinzer, Markus W Büchler, Martina Kadmon, Beat P Müller-Stich, Lars Fischer

Teaching and learning in medicine. 04/2012; 24(2):140-8.

Background: Randomized studies have already described the advantages of three dimensional (3D) presentations in understanding complex spatial interactions. However, the clinical setting is mainly characterized by presentations of two dimensional (2D) images. Purpose: This study evaluates whether tra... [more] Background: Randomized studies have already described the advantages of three dimensional (3D) presentations in understanding complex spatial interactions. However, the clinical setting is mainly characterized by presentations of two dimensional (2D) images. Purpose: This study evaluates whether training on 3D presentation enhances the understanding of 2D images. Methods: A teaching module was used consisting of one learning part and two examination parts (EP). Students were randomized to training with either 2D or 3D. Results: This study of 73 students showed that training on 3D presentations did not improve the ability to interpret 2D images. Further, the results revealed no significant differences between the results of Week 1 (2D: M = 6.5, SD = 1.8; 3D: M = 6.6, SD = 1.4; p > .95) and Week 2 (2D: M = 6.1, SD = 1.9; 3D: M = 6.0, SD = 1.4; p > .7). There were no significant gender differences. However, students randomized to 2D who completed only the first EP performed significantly worse if compared to students who completed both EP ( p = .04). Conclusions: This randomized controlled study shows that correct interpretation of 2D imaging does not differ in students trained with either 3D or 2D.

MITK Global Tractography

Peter F. Neher, Bram Stieltjes, Marco Reisert, Ignaz Reicht, Hans-Peter Meinzer, Klaus H. Fritzsche

SPIE, San Diego, USA; 01/2012

7.67

Impact points

iPad-assisted percutaneous access to the kidney using marker-based navigation: initial clinical experience.

Jens J Rassweiler, Michael Müller, Markus Fangerau, Jan Klein, Ali S Goezen, Philippe Pereira, Hans-Peter Meinzer, Dogu Teber

European urology. 12/2011; 61(3):628-31.

3.75

Impact points

Convergent Iterative Closest-Point Algorithm to Accomodate Anisotropic and Inhomogenous Localization Error.

Lena Maier-Hein, Alfred Michael Franz, Thiago R Dos Santos, Mirko Schmidt, Markus Fangerau, Hans-Peter Meinzer, J Michael Fitzpatrick

IEEE transactions on pattern analysis and machine intelligence. 12/2011;

The Iterative Closest Point (ICP) algorithm has become one of the most well-known methods for fine geometric alignment of 3D models that can be represented by point sets. It iteratively establishes point correspondences given the current alignment of the data and computes a rigid transform according... [more] The Iterative Closest Point (ICP) algorithm has become one of the most well-known methods for fine geometric alignment of 3D models that can be represented by point sets. It iteratively establishes point correspondences given the current alignment of the data and computes a rigid transform accordingly. From a statistical point of view, however, it implicitly assumes that the points are observed with isotropic Gaussian noise. In this paper, we show that this assumption may lead to errors and generalize the ICP such that it can account for anisotropic and inhomogenous localization errors in the input data. We (1) provide a formal description of the algorithm, (2) extend it to registration of partially overlapping surfaces, (3) prove its convergence, (4) derive the required covariance matrices for a set of selected applications, and (5) present means for optimizing the run-time of the algorithm. An evaluation on publically available surface meshes as well as on a set of meshes extracted from medical imaging data shows a dramatic increase in accuracy compared to the standard ICP, especially in the case of partial surface registration. As surface matching is a central component in various applications, the potential impact of the proposed method is extremely high.

1.75

Impact points

Augmented reality visualization during laparoscopic radical prostatectomy.

Tobias Simpfendörfer, Matthias Baumhauer, Michael Müller, Carsten N Gutt, Hans-Peter Meinzer, Jens J Rassweiler, Selcuk Guven, Dogu Teber

Journal of endourology / Endourological Society. 12/2011; 25(12):1841-5.

We present an augmented reality (AR) navigation system that conveys virtual organ models generated from transrectal ultrasonography (TRUS) onto a real laparoscopic video during radical prostatectomy. By providing this additional information about the actual anatomy, we can support surgeons in their ... [more] We present an augmented reality (AR) navigation system that conveys virtual organ models generated from transrectal ultrasonography (TRUS) onto a real laparoscopic video during radical prostatectomy. By providing this additional information about the actual anatomy, we can support surgeons in their working decisions. This work reports the system's first in-vivo application. The system uses custom-developed needles with colored heads that are inserted into the prostate as soon as the organ surface is uncovered. These navigation aids are once segmented in three-dimensional (3D) TRUS data that is acquired right after the placement of the needles and then continuously tracked in the laparoscopic video images by the surgical navigation system. The navigation system traces the navigation aids in real time and computes a registration between TRUS image and laparoscopic video based on the two-dimensional-three dimensional (2D-3D) point correspondences. With this registration, the system correctly superimposes TRUS-based 3D information on an additional AR monitor placed next to the normal laparoscopic screen. Surgical navigation guidance took place until the prostate was removed from the rectal wall. Finally, the navigation aids were removed together with the specimen inside the specimen bag. The initial human in-vivo application of the surgical navigation system was successful. No complications occurred, the prostate was removed together with the navigation aids, and the system supported the surgeons as intended with an AR visualization in real time. In case of tissue deformations, changes in the spatial configuration of the navigation aids are detected, which preserves the system from erroneous navigation visualization. Feasibility of the navigation system was shown in the first in-vivo application. TRUS information could be superimposed via AR in real time. To show the benefit for the patient, results obtained from a larger number of trials are needed.

2.70

Impact points

An electromagnetic navigation system for transbronchial interventions with a novel approach to respiratory motion compensation.

Ingmar Gergel, Jan Hering, Ralf Tetzlaff, Hans-Peter Meinzer, Ingmar Wegner

Medical physics. 12/2011; 38(12):6742-53.

Bronchoscopic interventions, such as transbronchial needle aspiration (TBNA), are commonly performed procedures to diagnose and stage lung cancer. However, due to the complex structure of the lung, one of the main challenges is to find the exact position to perform a biopsy and to actually hit the b... [more] Bronchoscopic interventions, such as transbronchial needle aspiration (TBNA), are commonly performed procedures to diagnose and stage lung cancer. However, due to the complex structure of the lung, one of the main challenges is to find the exact position to perform a biopsy and to actually hit the biopsy target (e.g., a lesion). Today, most interventions are accompanied by fluoroscopy to verify the position of the biopsy instrument, which means additional radiation exposure for the patient and the medical staff. Furthermore, the diagnostic yield of TBNA is particularly low for peripheral lesions. To overcome these problems the authors developed an image-guided, electromagnetic navigation system for transbronchial interventions. The system provides real time positioning information for the bronchoscope and a transbronchial biopsy instrument with only one preoperatively acquired computed tomography image. A twofold respiratory motion compensation method based on a particle filtering approach allows for guidance through the entire respiratory cycle. In order to evaluate our system, 18 transbronchial interventions were performed in seven ventilated swine lungs using a thorax phantom. All tracked bronchoscope positions were corrected to the inside of the tracheobronchial tree and 80.2% matched the correct bronchus. During regular respiratory motion, the mean overall targeting error for bronchoscope tracking and TBNA needle tracking was with compensation on 10.4 ± 1.7 and 10.8 ± 3.0 mm, compared to 14.4 ± 1.9 and 13.3 ± 2.7 mm with compensation off. The mean fiducial registration error (FRE) was 4.2 ± 1.1 mm. The navigation system with the proposed respiratory motion compensation method allows for real time guidance during bronchoscopic interventions, and thus could increase the diagnostic yield of transbronchial biopsy.

2.70

Impact points

Computer-assisted trajectory planning for percutaneous needle insertions.

Alexander Seitel, Markus Engel, Christof M Sommer, Boris A Radeleff, Caroline Essert-Villard, Claire Baegert, Markus Fangerau, Klaus H Fritzsche, Kwong Yung, Hans-Peter Meinzer, Lena Maier-Hein

Medical physics. 06/2011; 38(6):3246-59.

Computed tomography (CT) guided minimally invasive interventions such as biopsies or ablation therapies often involve insertion of a needle-shaped instrument into the target organ (e.g., the liver). Today, these interventions still require manual planning of a suitable trajectory to the target (e.g.... [more] Computed tomography (CT) guided minimally invasive interventions such as biopsies or ablation therapies often involve insertion of a needle-shaped instrument into the target organ (e.g., the liver). Today, these interventions still require manual planning of a suitable trajectory to the target (e.g., the tumor) based on the slice data provided by the imaging modality. However, taking into account the critical structures and other parameters crucial to the success of the intervention--such as instrument shape and penetration angle--is challenging and requires a lot of experience. To overcome these problems, we present a system for the automatic or semiautomatic planning of optimal trajectories to a target, based on 3D reconstructions of all relevant structures. The system determines possible insertion zones based on so-called hard constraints and rates the quality of these zones by so-called soft constraints. The concept of pareto optimality is utilized to allow for a weight-independent proposal of insertion trajectories. In order to demonstrate the benefits of our method, automatic trajectory planning was applied retrospectively to n = 10 data sets from interventions in which complications occurred. The efficient (graphics processing unit-based) implementation of the constraints results in a mean overall planning time of about 9 s. The examined trajectories, originally chosen by the physician, have been rated as follows: in six cases, the insertion point was labeled invalid by the planning system. For two cases, the system would have proposed points with a better rating according to the soft constraints. For the remaining two cases the system would have indicated poor rating with respect to one of the soft constraints. The paths proposed by our system were rated feasible and qualitatively good by experienced interventional radiologists. The proposed computer-assisted trajectory planning system is able to detect unsafe and propose safe insertion trajectories and may especially be helpful for interventional radiologist at the beginning or during their interventional training.

MITK-ToF--range data within MITK.

Alexander Seitel, Kwong Yung, Sven Mersmann, Thomas Kilgus, Anja Groch, Thiago R dos Santos, Alfred M Franz, Marco Nolden, Hans-Peter Meinzer, Lena Maier-Hein

International journal of computer assisted radiology and surgery. 05/2011; 7(1):87-96.

The time-of-flight (ToF) technique is an emerging technique for rapidly acquiring distance information and is becoming increasingly popular for intra-operative surface acquisition. Using the ToF technique as an intra-operative imaging modality requires seamless integration into the clinical workflow... [more] The time-of-flight (ToF) technique is an emerging technique for rapidly acquiring distance information and is becoming increasingly popular for intra-operative surface acquisition. Using the ToF technique as an intra-operative imaging modality requires seamless integration into the clinical workflow. We thus aim to integrate ToF support in an existing framework for medical image processing. MITK-ToF was implemented as an extension of the open-source C++ Medical Imaging Interaction Toolkit (MITK) and provides the basic functionality needed for rapid prototyping and development of image-guided therapy (IGT) applications that utilize range data for intra-operative surface acquisition. This framework was designed with a module-based architecture separating the hardware-dependent image acquisition task from the processing of the range data. The first version of MITK-ToF has been released as an open-source toolkit and supports several ToF cameras and basic processing algorithms. The toolkit, a sample application, and a tutorial are available from http://mitk.org. With the increased popularity of time-of-flight cameras for intra-operative surface acquisition, integration of range data supports into medical image processing toolkits such as MITK is a necessary step. Handling acquisition of range data from different cameras and processing of the data requires the establishment and use of software design principles that emphasize flexibility, extendibility, robustness, performance, and portability. The open-source toolkit MITK-ToF satisfies these requirements for the image-guided therapy community and was already used in several research projects.

3.31

Impact points

Multimedia article. Navigated renal access using electromagnetic tracking: an initial experience.

Johannes Huber, Ingmar Wegner, Hans-Peter Meinzer, Peter Hallscheidt, Boris Hadaschik, Sascha Pahernik, Markus Hohenfellner

Surgical endoscopy. 04/2011; 25(4):1307-12.

Navigation systems are promising tools for improving efficacy and safety in surgical endoscopy and other minimally invasive techniques. The aim of the current study is to investigate electromagnetic tracking (EMT) for navigated renal access in a porcine model. For our proof-of-principle study we mod... [more] Navigation systems are promising tools for improving efficacy and safety in surgical endoscopy and other minimally invasive techniques. The aim of the current study is to investigate electromagnetic tracking (EMT) for navigated renal access in a porcine model. For our proof-of-principle study we modified a recently established porcine ex vivo model. Via a ureteral catheter which was placed into the desired puncture site, a small sensor was introduced and located by EMT. Then, a tracked needle was navigated into the collecting system in a "rendezvous" approach. A total of 90 renal tracts were obtained in six kidneys using EMT, with a maximum of three punctures allowed per intervention. For each puncture, number of attempts to success, final distance to probe, puncture time, and localization were assessed. We compared absolute and relative frequencies using the chi-square test and applied the Mann-Whitney U-test for continuous variables. No major problems were encountered performing the experiment. Access to the collecting system was successfully obtained after a single puncture in 91% (82/90) and within a second attempt in the remaining 9% (8/90). Thus, a 100% success rate was reached after a maximum of two punctures. Location of the calyx did not have a significant effect on success rate (p = 0.637). After a learning phase of 30 punctures, higher success rate (96% versus 83%; p = 0.041) was accomplished within shorter puncture time (14 versus 17 s; p = 0.049) and with higher precision (1.7 versus 2.8 mm; p < 0.001). With respect to other established techniques, use of EMT seems to decrease the number of attempts and procedural time remarkably. This might contribute to greater safety and efficacy when applied clinically. The presented approach appears to be promising, especially in difficult settings, provided that in vivo data support these initial results.

1.57

Impact points

Liver tissue sparing resection using a novel planning tool.

Frank Pianka, Matthias Baumhauer, Daniel Stein, Boris Radeleff, Bruno M Schmied, Hans-Peter Meinzer, Sascha A Müller

Langenbeck's archives of surgery / Deutsche Gesellschaft für Chirurgie. 02/2011; 396(2):201-8.

Accurate preoperative prediction of liver function, volume, and vessel anatomy is essential in preventing postoperative liver failure, optimizing safety, and ensuring optimal outcome in patients undergoing hepatic surgery. We propose that preoperative resection planning provides useful anatomical an... [more] Accurate preoperative prediction of liver function, volume, and vessel anatomy is essential in preventing postoperative liver failure, optimizing safety, and ensuring optimal outcome in patients undergoing hepatic surgery. We propose that preoperative resection planning provides useful anatomical and volumetric data, allowing for sparing of liver tissue in surgical resections. The purpose of the present study was to evaluate the use of a novel resection planning tool. Thirteen patients undergoing hemihepatectomy were included. Preoperative resection planning was performed using the commercially available software Mint Liver. During resection planning, virtual resections were calculated based on Couinaud classification, Cantlie's line (standard), and individually by the operating surgeon (individual). Intraoperatively, volume and weight of the resected specimen were measured. A 14-day follow-up was conducted, and laboratory parameters were collected. Statistical analysis was performed, comparing virtual resection volumes (i.e., standard vs. individual) and secondarily virtual vs. actual resection volume. We found a significant difference (p = 0.001) in the comparison of standard vs. individual in all 13 cases, with an average 92.8 mL smaller resected volume, sparing 11.3% of liver parenchyma with virtual resection. No patients suffered from acute liver failure. Perioperative mortality was 0%. Mint Liver is capable of acquiring exact anatomical and volumetric knowledge prior to hepatic resections. Liver parenchyma can be spared by preoperative assessment of the resection plan. We propose that this tool could be an important addition to preoperative patient evaluation, especially in complex liver surgery and living donor liver transplantation where precise volumetry is the decisive factor.

Extending the

Thiago R. dos Santos, Hans-Peter Meinzer, Lena Maier-Hein

Int. J. Comput. Geometry Appl. 01/2011; 21:467-494.

Computer aided planning of patches and conduits for surgery in congenital heart disease

Eugenié Riesenkampff, Michael Huebler, Urte Rietdorf, Tobias Heimann, Tobias Schwarz, Hans-Peter Meinzer, Felix Berger, Titus Kuehne

Journal of Cardiovascular Magnetic Resonance. 01/2011;