CBCT-based navigation system for open liver surgery: Accurate guidance toward mobile and deformable targets with a semi-rigid organ approximation and electromagnetic tracking of the liver.

PURPOSE: The surgical navigation system that provides guidance throughout the surgery can facilitate safer and more radical liver resections, but such a system should also be able to handle organ motion. This work investigates the accuracy of intraoperative surgical guidance during open liver resection, with a semi-rigid organ approximation and electromagnetic tracking of the target area. METHODS: The suggested navigation technique incorporates a preoperative 3D liver model based on diagnostic 4D MRI scan, intraoperative contrast-enhanced CBCT imaging and electromagnetic (EM) tracking of the liver surface, as well as surgical instruments, by means of six degrees-of-freedom micro-EM sensors. RESULTS: The system was evaluated during surgeries with 35 patients and resulted in an accurate and intuitive real-time visualization of liver anatomy and tumor's location, confirmed by intraoperative checks on visible anatomical landmarks. Based on accuracy measurements verified by intraoperative CBCT, the system's average accuracy was 4.0 ± 3.0 mm, while the total surgical delay due to navigation stayed below 20 min. CONCLUSIONS: The electromagnetic navigation system for open liver surgery developed in this work allows for accurate localization of liver lesions and critical anatomical structures surrounding the resection area, even when the liver was manipulated. However, further clinically integrating the method requires shortening the guidance-related surgical delay, which can be achieved by shifting to faster intraoperative imaging like ultrasound. Our approach is adaptable to navigation on other mobile and deformable organs, and therefore may benefit various clinical applications.

A workflow for automated segmentation of the liver surface, hepatic vasculature and biliary tree anatomy from multiphase MR images.

Accurate assessment of 3D models of patient-specific anatomy of the liver, including underlying hepatic and biliary tree, is critical for preparation and safe execution of complex liver resections, especially due to high variability of biliary and hepatic artery anatomies. Dynamic MRI with hepatospecific contrast agents is currently the only type of diagnostic imaging that provides all anatomical information required for generation of such a model, yet there is no information in the literature on how the complete 3D model can be generated automatically. In this work, a new automated segmentation workflow for extraction of patient-specific 3D model of the liver, hepatovascular and biliary anatomy from a single multiphase MRI acquisition is developed and quantitatively evaluated. The workflow incorporates course 4D k-means clustering estimation and geodesic active contour refinement of the liver boundary, based on organ's characteristic uptake of gadolinium contrast agents overtime. Subsequently, hepatic vasculature and biliary ducts segmentations are performed using multiscale vesselness filters. The algorithm was evaluated using 15 test datasets of patients with liver malignancies of various histopathological types. It showed good correlation with expert manual segmentation, resulting in an average of 1.76 ± 2.44 mm Hausdorff distance for the liver boundary, and 0.58 ± 0.72 and 1.16 ± 1.98 mm between centrelines of biliary ducts and liver veins, respectively. A workflow for automatic segmentation of the liver, hepatic vasculature and biliary anatomy from a single diagnostic MRI acquisition was developed. This enables automated extraction of 3D models of patient-specific liver anatomy, and may facilitating better perception of organ's anatomy during preparation and execution of liver surgeries. Additionally, it may help to reduce the incidence of intraoperative biliary duct damage due to an unanticipated variation in the anatomy.

Prospective study on image-guided navigation surgery for pelvic malignancies.

BACKGROUND AND OBJECTIVES: Surgery of advanced tumors and lymph nodes in the pelvis can be challenging due to the narrow pelvic space and vital surrounding structures. This study explores the application of a novel electromagnetic navigation system to guide pelvic surgery. METHODS: This was a prospective study on surgery for malignancies in the pelvis. Preoperatively obtained imaging was used to create a patient-specific three-dimensional (3D) roadmap. In the operating room, the 3D roadmap was registered to an intraoperative computed tomography scan. A tracked pointer was used during surgery for guidance. Primary endpoint was safety and feasibility, secondary endpoints were accuracy and usability. RESULTS: Twenty-eight colorectal, four liposarcomas, and one gynecological patient were included. There were no safety issues. Navigation was feasible in 31 patients. The mean target registration errors of 4.0 and 6.3 mm were achieved for straight and French position, respectively. In seven of seven patients with a locally advanced rectal tumor and in seven of eight patients with recurrences, negative margins were achieved. Thirty-three of 36 target lymph nodes were successfully removed. Surgeons using the system indicated faster localization of the tumor and improved decisiveness. CONCLUSION: This novel surgical navigation system was safe and feasible during pelvic surgery and can facilitate its users.

Intraoperative 3D Navigation for Single or Multiple 125I-Seed Localization in Breast-Preserving Cancer Surgery.

BACKGROUND: Mammographic screening has led to the identification of more women with nonpalpable breast cancer, many of them to be treated with breast-preserving surgery. To accomplish radical tumor excision, adequate localization techniques such as radioactive seed localization (RSL) are required. For RSL, a radioactive I-seed is implanted central in the tumor to enable intraoperative localization using a γ-probe. In case of extensive tumor or multifocal carcinoma, multiple I-seeds can be used to delineate the involved area. Preoperative imaging is performed different from surgical positioning; therefore, exact I-seed depth remains unknown during surgery. PATIENTS AND METHODS: Twenty patients (mean age, 56.8 years) with 25 implanted I-seeds scheduled for RSL were included. Sixteen patients had 1 I-seed implanted in the primary lesion, 3 patients had 2 I-seeds, and 1 patient had 3 I-seeds. Freehand SPECT localized I-seeds by measuring γ-counts from different directions, all registered by an optical tracking system. A reconstruction and visualization algorithm enabled 3-dimensional (3D) navigation toward the I-seeds. RESULTS: Freehand SPECT visualized all I-seeds in primary tumors and provided preincision depth information. The deviation, mean (SD), between the freehand SPECT depth and the surgical depth estimation was 1.9 (2.1) mm (range, 0-7 mm). Three-dimensional freehand SPECT was especially useful identifying multiple implanted I-seeds because the conventional γ-probe has more difficulty discriminating I-seeds transcutaneous. CONCLUSIONS: Freehand SPECT with 3D navigation is a valuable tool in RSL for both single and multiple implanted I-seeds in breast-preserving cancer surgery. Freehand SPECT provides continuous updating 3D imaging with information about depth and location of the I-seeds contributing to adequate excision of nonpalpable breast cancer.

Improved Accuracy and Reproducibility Using a Training Protocol for Freehand-SPECT 3D Mapping in Radio-Guided Surgery.

PURPOSE: Freehand single-photon emission computed tomography (SPECT) (fh-SPECT) for optical tracked 3-dimensional radioactivity mapping raises popularity for sentinel node biopsy and other radio-guided procedures. However, the device seems to be complex, requiring both training and a standardized scan protocol. Therefore, the aim of this study was to compare handling reproducibility between novice and expert users; subsequently, using additional scans, we evaluated a standardized scan protocol to be tested in novice users after receiving training. MATERIALS AND METHODS: Three groups (untrained novices, experts, and trained novices), each one composed of 5 fh-SPECT users, were given the same short introduction and the assignment to perform 3 fh-SPECT scans with the same time per scan. For the scans, a reproducible phantom with an iodine-125 point source was used. Furthermore, we performed probe-trajectory evaluation including pattern, speed, and length of scans based on recorded videos and digital target tracking. RESULTS: The training period encompasses 30 minutes per novice user. The mean error in 3 directions based on 45 measurements was 7.4 mm for untrained novices and 3.2 mm for expert users. The trained novice group had a mean error of 2.9 mm (a significant 61% reduction), comparable to the expert group. The reproducibility values, expressed in SD, were 4.1 mm for the untrained novice group, 1.3 mm for the expert group, and 1.1 mm for the trained novices (73% improvement). The standardized scan protocol was demonstrated by means of trajectory evaluation, a scan path better systematized. CONCLUSION: Scanning with fh-SPECT for radio-guided surgery requires a specific training period to increase handling and reproducibility of 3-dimensional imaging, and to enhance its accuracy in the operating room.

Heading toward radioactive seed localization in non-palpable breast cancer surgery? A meta-analysis.

Wire-guided localization is the most commonly used technique for intraoperative localization of non-palpable breast cancer. Radioactive seed localization (RSL) is becoming more popular and seems to be a reliable alternative for intraoperative lesion localization. The purpose of the present meta-analysis was to evaluate the use of RSL. Primary study outcomes were irradicality and re-excision rates. In total 3168 patients were included. The clinical adaptation shows growing confidence in RSL and further growth is expected.

Radio-guided seed localization for breast cancer excision: an ex-vivo specimen-based study to establish the accuracy of a freehand-SPECT device in predicting resection margins.

PURPOSE: Radioactive seed localization (RSL) uses an iodine-125 ((125)I) seed as a marker for tumour location. The (125)I seed is implanted into the tumour and enables intraoperative localization with a conventional gamma probe. However, specimen margins in relation to the (125)I seed are estimated on the basis of gamma-probe readings only. A novel device, freehand SPECT, is capable of measuring the distance from the resection plane to the (125)I seed. The aim of this feasibility study was to establish the accuracy of this device in predicting resection margins in ex-vivo tumour specimens excised with RSL guidance. PATIENTS AND METHODS: In this feasibility study 10 patients with nonpalpable breast cancer scheduled for wide local excision with RSL were included. After surgery, the specimens containing the breast tumour and the (125)I seed were scanned using freehand SPECT. Measurements from five directions were taken and compared with distances measured by means of an ex-vivo computed tomographic (CT) scan and related to the pathology report. RESULTS: The difference between freehand SPECT and CT measurements was 2.9±2.7 mm (mean±SD). One patient had a positive margin based on freehand SPECT. This specimen contained a focal irradical resection ventral of the tumour based on the pathology report. The smallest distance to the (125)I seed was 4 mm for the freehand SPECT and 5 mm for the CT scan. CONCLUSION: Accurate ex-vivo measurements of the tumour resection margins using (125)I seeds and freehand SPECT are feasible in patients undergoing breast-conserving surgery. Incorporation of the freehand-SPECT device in RSL protocols may enable a real-time estimation of resection margins, which may be useful for surgeons to adjust resection planes.

Feasibility of preoperative (125)I seed-guided tumoural tracer injection using freehand SPECT for sentinel lymph node mapping in non-palpable breast cancer.

BACKGROUND: This study was designed to explore the feasibility of replacing the conventional peri-/intratumoural ultrasound (US)-guided technetium-99m albumin nanocolloid ((99m)Tc-nanocolloid) administration by an injection of the same tracer guided by a freehand single-photon emission computed tomography (SPECT) device in patients with non-palpable breast cancer with an iodine-125 ((125)I) seed as tumour marker, who are scheduled for a sentinel lymph node biopsy (SLNB). This approach aimed to decrease the workload of the radiology department, avoiding a second US-guided procedure. METHODS: In ten patients, the implanted (125)I seed was primarily localised using freehand SPECT and subsequently verified by conventional US in order to inject the (99m)Tc-nanocolloid. The following 34 patients were injected using only freehand SPECT localisation. In these patients, additional SPECT/CT was acquired to measure the distance between the (99m)Tc-nanocolloid injection depot and the (125)I seed. In retrospect, a group of 21 patients with US-guided (99m)Tc-nanocolloid administrations was included as a control group. RESULTS: The depth difference measured by US and freehand SPECT in ten patients was 1.6 ± 1.6 mm. In the following 36 (125)I seeds (34 patients), the average difference between the (125)I seed and the centre of the (99m)Tc-nanocolloid injection depot was 10.9 ± 6.8 mm. In the retrospective study, the average distance between the (125)I seed and the centre of the (99m)Tc-nanocolloid injection depot as measured in SPECT/CT was 9.7 ± 6.5 mm and was not significantly different compared to the freehand SPECT-guided group (two-sample Student's t test, p = 0.52). CONCLUSION: We conclude that using freehand SPECT for (99m)Tc-nanocolloid administration in patients with non-palpable breast cancer with previously implanted (125)I seed is feasible. This technique may improve daily clinical logistics, reducing the workload of the radiology department.