Navigation in laparoscopy--prototype research platform for improved image-guided surgery

COMPASS: localization in laparoscopic visceral surgery

Tracking of surgical instruments is an essential step towards the modernization of the surgical workflow by a comprehensive surgical landscape guidance system (COMPASS). Real-time tracking of a laparoscopic camera used in minimally-invasive surgery is required for applications in surgical workflow documentation, machine learning, image-localization, and intra-operative visualization. In our approach, an inertial measurement unit (IMU) assists the tool tracking in situations when no line-of-sight is available for infrared (IR) based tracking of the laparoscopic camera. The novelty of this approach lies in the localization method adjusted for the laparoscopic visceral surgery, particularly when the line-of-sight is lost. It is based on IMU tracking and the positioning of the trocar entry point. The trocar entry point is the remote center of motion (RCM), reducing degrees of freedom. We developed a method to tackle localization and a real-time tool for position and orientation estimation. The main error sources are given and evaluated in a test scenario. It reveals that for small changes in penetration length (e.g., pivoting), the IMU’s accuracy determines the error.

Peripheral tumour targeting using open-source virtual bronchoscopy with electromagnetic tracking: a multi-user pre-clinical study

Objectives: The goal was to demonstrate the utility of open-source tracking and visualisation tools in the targeting of lung cancer.Material and methods: The study demonstrates the first deployment of the Anser electromagnetic (EM) tracking system with the CustusX image-guided interventional research platform to navigate using an endobronchial catheter to injected tumour targets. Live animal investigations validated the deployment and targeting of peripheral tumour models using an innovative tumour marking routine.Results: Novel tumour model deployment was successfully achieved at all eight target sites across two live animal investigations without pneumothorax. Virtual bronchoscopy with tracking successfully guided the tracked catheter to 2-12 mm from the target tumour site. Deployment of a novel marker was achieved at all eight sites providing a reliable measure of targeting accuracy. Targeting accuracy within 10 mm was achieved in 7/8 sites and in all cases, the virtual target distance at marker deployment was within the range subsequently measured with x-ray.Conclusions: Endobronchial targeting of peripheral airway targets is feasible using existing open-source technology. Notwithstanding the shortcomings of current commercial platforms, technological improvements in EM tracking and registration accuracy fostered by open-source technology may provide the impetus for widespread clinical uptake of electromagnetic navigation in bronchoscopy.

Accuracy assessment of wireless transponder tracking in the operating room environment

PURPOSE

To evaluate the applicability of the Calypso^® wireless transponder tracking system (Varian Medical Systems Inc., USA) for real-time tumor motion tracking during surgical procedures on tumors in non-rigid target areas. An accuracy assessment was performed for an extended electromagnetic field of view (FoV) of 27.5 × 27.5 × 22.5 cm (which included the standard FoV of 14 × 14 × 19 cm) in which 5DOF wireless Beacon^® transponders can be tracked.

METHODS

Using a custom-made measurement setup, we assessed single transponder relative accuracy, absolute accuracy and jitter throughout the extended FoV at 1440 locations interspaced with 2.5 cm in each orthogonal direction. The NDI Polaris Spectra optical tracking system (OTS) was used as a reference. Measurements were taken in a room without surrounding distorting factors and repeated in an operating room (OR). In the OR, the influence of a carbon fiber and regular stainless steel OR tabletop was investigated.

RESULTS

The calibration of the OTS and transponder system resulted in an average root-mean-square error (RMSE) vector of 0.03 cm. For both the standard and extended FoV, all accuracy measures were dependent on transponder to tracking array (TA) distances and the absolute accuracy was also dependent on TA to OR tabletop distances. This latter influence was reproducible, and after calibrating this, the residual error was below 0.1 cm RMSE within the entire standard FoV. Within the extended FoV, this residual RMSE did not exceed 0.1 cm for transponder to TA distances up to 25 cm.

CONCLUSION

This study shows that transponder tracking is promising for accurate tumor tracking in the operating room. This applies when using the standard FoV, but also when using the extended FoV up to 25 cm above the TA, substantially increasing flexibility.

A novel method for texture-mapping conoscopic surfaces for minimally invasive image-guided kidney surgery

PURPOSE

Organ-level registration is critical to image-guided therapy in soft tissue. This is especially important in organs such as the kidney which can freely move. We have developed a method for registration that combines three-dimensional locations from a holographic conoscope with an endoscopically obtained textured surface. By combining these data sources clear decisions as to the tissue from which the points arise can be made.

METHODS

By localizing the conoscope's laser dot in the endoscopic space, we register the textured surface to the cloud of conoscopic points. This allows the cloud of points to be filtered for only those arising from the kidney surface. Once a valid cloud is obtained we can use standard surface registration techniques to perform the image-space to physical-space registration. Since our methods use two distinct data sources we test for spatial accuracy and characterize temporal effects in phantoms, ex vivo porcine and human kidneys. In addition we use an industrial robot to provide controlled motion and positioning for characterizing temporal effects.

RESULTS

Our initial surface acquisitions are hand-held. This means that we take approximately 55 s to acquire a surface. At that rate we see no temporal effects due to acquisition synchronization or probe speed. Our surface registrations were able to find applied targets with submillimeter target registration errors.

CONCLUSION

The results showed that the textured surfaces could be reconstructed with submillimetric mean registration errors. While this paper focuses on kidney applications, this method could be applied to any anatomical structures where a line of sight can be created via open or minimally invasive surgical techniques.

Clinical application of a surgical navigation system based on virtual laparoscopy in laparoscopic gastrectomy for gastric cancer

PURPOSE

Knowledge of the specific anatomical information of a patient is important when planning and undertaking laparoscopic surgery due to the restricted field of view and lack of tactile feedback compared to open surgery. To assist this type of surgery, we have developed a surgical navigation system that presents the patient's anatomical information synchronized with the laparoscope position. This paper presents the surgical navigation system and its clinical application to laparoscopic gastrectomy for gastric cancer.

METHODS

The proposed surgical navigation system generates virtual laparoscopic views corresponding to the laparoscope position recorded with a three-dimensional (3D) positional tracker. The virtual laparoscopic views are generated from preoperative CT images. A point-based registration aligns coordinate systems between the patient's anatomy and image coordinates. The proposed navigation system is able to display the virtual laparoscopic views using the registration result during surgery.

RESULTS

We performed surgical navigation during laparoscopic gastrectomy in 23 cases. The navigation system was able to present the virtual laparoscopic views in synchronization with the laparoscopic position. The fiducial registration error was calculated in all 23 cases, and the average was 14.0 mm (range 6.1-29.8).

CONCLUSION

The proposed surgical navigation system can provide CT-derived patient anatomy aligned to the laparoscopic view in real time during surgery. This system enables accurate identification of vascular anatomy as a guide to vessel clamping prior to total or partial gastrectomy.

A Novel Ultrasound-Based Registration for Image-Guided Laparoscopic Liver Ablation

Background Patient-to-image registration is a core process of image-guided surgery (IGS) systems. We present a novel registration approach for application in laparoscopic liver surgery, which reconstructs in real time an intraoperative volume of the underlying intrahepatic vessels through an ultrasound (US) sweep process. Methods An existing IGS system for an open liver procedure was adapted, with suitable instrument tracking for laparoscopic equipment. Registration accuracy was evaluated on a realistic phantom by computing the target registration error (TRE) for 5 intrahepatic tumors. The registration work flow was evaluated by computing the time required for performing the registration. Additionally, a scheme for intraoperative accuracy assessment by visual overlay of the US image with preoperative image data was evaluated. Results The proposed registration method achieved an average TRE of 7.2 mm in the left lobe and 9.7 mm in the right lobe. The average time required for performing the registration was 12 minutes. A positive correlation was found between the intraoperative accuracy assessment and the obtained TREs. Conclusions The registration accuracy of the proposed method is adequate for laparoscopic intrahepatic tumor targeting. The presented approach is feasible and fast and may, therefore, not be disruptive to the current surgical work flow.

Comparing position and orientation accuracy of different electromagnetic sensors for tracking during interventions

PURPOSE

To compare the position and orientation accuracy between using one 6-degree of freedom (DOF) electromagnetic (EM) sensor, or the position information of three 5DOF sensors within the scope of tumor tracking.

METHODS

The position accuracy of Northern Digital Inc Aurora 5DOF and 6DOF sensors was determined for a table-top field generator (TTFG) up to a distance of 52 cm. For each sensor 716 positions were measured for 10 s at 15 Hz. Orientation accuracy was determined for each of the orthogonal axis at the TTFG distances of 17, 27, 37 and 47 cm. For the 6DOF sensors, orientation was determined for sensors in-line with the orientation axis, and perpendicular. 5DOF orientation accuracy was determined for a theoretical 4 cm tumor. An optical tracking system was used as reference.

RESULTS

Position RMSE and jitter were comparable between the sensors and increasing with distance. Jitter was within 0.1 cm SD within 45 cm distance to the TTFG. Position RMSE was approximately 0.1 cm up to 32 cm distance, increasing to 0.4 cm at 52 cm distance. Orientation accuracy of the 6DOF sensor was within 1[Formula: see text], except when the sensor was in-line with the rotation axis perpendicular to the TTFG plane (4[Formula: see text] errors at 47 cm). Orientation accuracy using 5DOF positions was within 1[Formula: see text] up to 37 cm and 2[Formula: see text] at 47 cm.

CONCLUSIONS

The position and orientation accuracy of a 6DOF sensor was comparable with a sensor configuration consisting of three 5DOF sensors. To achieve tracking accuracy within 1 mm and 1[Formula: see text], the distance to the TTFG should be limited to approximately 30 cm.

Image-guided liver surgery: intraoperative projection of computed tomography images utilizing tracked ultrasound

BACKGROUND

Ultrasound (US) is the most commonly used form of image guidance during liver surgery. However, the use of navigation systems that incorporate instrument tracking and three-dimensional visualization of preoperative tomography is increasing. This report describes an initial experience using an image-guidance system with navigated US.

METHODS

An image-guidance system was used in a total of 50 open liver procedures to aid in localization and targeting of liver lesions. An optical tracking system was employed to localize surgical instruments. Customized hardware and calibration of the US transducer were required. The results of three procedures are highlighted in order to illustrate specific navigation techniques that proved useful in the broader patient cohort.

RESULTS

Over a 7-month span, the navigation system assisted in completing 21 (42%) of the procedures, and tracked US alone provided additional information required to perform resection or ablation in six procedures (12%). Average registration time during the three illustrative procedures was <1 min. Average set-up time was approximately 5 min per procedure.

CONCLUSIONS

The Explorer™ Liver guidance system represents novel technology that continues to evolve. This initial experience indicates that image guidance is valuable in certain procedures, specifically in cases in which difficult anatomy or tumour location or echogenicity limit the usefulness of traditional guidance methods.

Interactive development of a CT-based tissue model for ultrasound simulation

The objective of this study was to make an interactive method for development of a tissue model, based on anatomical information in computed tomography (CT) images, for use in an ultrasound simulator for training or surgical pre-planning. The method consisted of (1) comparison of true ultrasound B-mode images with corresponding ultrasound-like images, and (2) modification of tissue properties to decrease the difference between these images. Ultrasound-like images that reproduced many, but not all the properties of corresponding true ultrasound images were generated. The tissue model could be used for real-time simulation of ultrasound-like B-mode images on a moderately priced computer.

Navigated laparoscopic ultrasound in abdominal soft tissue surgery: technological overview and perspectives

PURPOSE

Two-dimensinal laparoscopic ultrasound (LUS) is commonly used for many laparoscopic procedures, but 3D LUS and navigation technology are not conventional tools in the clinic. Navigated LUS can help the user understand and interpret the ultrasound images in relation to the laparoscopic view and preoperative images. When combined with information from MRI or CT, navigated LUS has the potential to provide information about anatomic shifts during the procedure. In this paper, we present an overview of the ongoing technological research and development related to LUS combined with navigation technology, The purpose of this overview is threefold: (1) an introduction for those new to the field of navigated LUS; (2) an overview for those working in the field and; and (3) as a reference for those searching for literature on technological developments related to navigation in ultrasound-guided laparoscopic surgery.

METHODS

Databases were searched to identify relevant publications from the last 10 years.

RESULTS

We were able to identify 18 key papers in the area of navigated LUS for the abdomen, originating from about 10-11 groups. We present the literature overview, including descriptions of our own experience in the field, and a discussion of the important clinical and technological aspects related to navigated LUS.

CONCLUSIONS

LUS integrated with miniaturized tracking technology is likely to play an important role in guiding future laparoscopic surgery.

Comparative evaluation of laparoscopic liver resection for posterosuperior and anterolateral segments

Background

Totally laparoscopic liver resection of lesions located in the posterosuperior segments is reported to be technically challenging. This study aimed to define whether these technical difficulties affect the surgical outcome.

Methods

A total of 220 patients underwent laparoscopic liver resection during 244 procedures from August 1998 to December 2010. The patients who underwent primary minor single liver resection for malignant tumors affecting either posterosuperior segments 1, 7, 8, and, 4a (group 1) or anterolateral segments 2, 3, 5, 6, and 4b (group 2) were included in the study. Seventy-five procedures found to be eligible for the study, including 28 patients in group 1 and 47 patients in group 2. Intraoperative unfavorable incidents were graded on the basis of the Satava approach and postoperative complications were graded in agreement with the Accordion classification.

Results

The operative time (median, 127 min) and blood loss (median, 200 ml) were equivalent in the two groups. The rates for blood transfusions and intraoperative accidents did not differ statistically between the groups. A tumor-free margin resection was achieved in 94.7% of the procedures, equivalently in both groups. The postoperative course was similar in the two groups. Postoperative complications developed in 2 cases (7.1%) in group 1 and 2 cases (4.3%) in group 2 (p = 0.626). The median hospital stay was 2 days in both groups.

Conclusions

Laparoscopic liver resection for lesions located in posterosuperior segments represents certain technical challenges. However, appropriate adjustment of surgical techniques and optimal patient positioning enables the laparoscopic technique to provide safe and effective parenchyma-sparing resections for lesions located in both posterosuperior and anterolateral segments.

Navigated ultrasound in laparoscopic surgery

Laparoscopic surgery is performed through small incisions that limit free sight and possibility to palpate organs. Although endoscopes provide an overview of organs inside the body, information beyond the surface of the organs is missing. Ultrasound can provide real-time essential information of inside organs, which is valuable for increased safety and accuracy in guidance of procedures. We have tested the use of 2D and 3D ultrasound combined with 3D CT data in a prototype navigation system. In our laboratory, micro-positioning sensors were integrated into a flexible intraoperative ultrasound probe, making it possible to measure the position and orientation of the real-time 2D ultrasound image as well as to perform freehand 3D ultrasound acquisitions. Furthermore, we also present a setup with the probe optically tracked from the shaft with the flexible part locked in one position. We evaluated the accuracy of the 3D laparoscopic ultrasound solution and obtained average values ranging from 1.6% to 3.6% volume deviation from the phantom specifications. Furthermore, we investigated the use of an electromagnetic tracking in the operating room. The results showed that the operating room setup disturbs the electromagnetic tracking signal by increasing the root mean square (RMS) distance error from 0.3 mm to 2.3 mm in the center of the measurement volume, but the surgical instruments and the ultrasound probe added no further inaccuracies. Tracked surgical tools, such as endoscopes, pointers, and probes, allowed surgeons to interactively control the display of both registered preoperative medical images, as well as intraoperatively acquired 3D ultrasound data, and have potential to increase the safety of guidance of surgical procedures.