Puncture Cube Patient-Mounted Navigation System versus Freehand Method for CT-Guided Needle Placement: Study on a Neoprene Covered Elliptical Cylinder Gelatin Phantom.

PURPOSE: The study aims to show how the "Puncture Cube" (PC) (Medical Templates, Egg, Switzerland) compares to the freehand method (FHM) for CT-guided punctures. METHODS: The PC is a patient-mounted disassemblable cube consisting of an upper and lower template with multiple holes each to predefine puncture trajectory. A total of 80 punctures (FHM in-plane, FHM off-plane, PC in-plane, PC off-plane) was performed by 4 radiologists on a target 9.1 cm below surface level of a neoprene covered elliptical cylinder gelatin phantom. The PC was never disassembled. Evaluated parameters were procedure time, number of CT-scans, euclidean distance (ED) and normal distance (ND). Respective parameters of FHM and PC were compared using the Wilcoxon signed-rank test and Levene test with significance levels of 5%. RESULTS: PC achieved smaller ED and ND values after initial needle insertion without corrections for both in-plane and off-plane punctures (P > 0.05). Variance of initial NDs was off-plane significantly larger for FHM. Final ED after needle path corrections was smaller for FHM both in- and off-plane (P < 0.05). Final off-plane ND was significantly lower for FHM with no significant difference in final in-plane ND. FHM off-plane punctures were significantly faster. There was no significant difference in CT-scans between both methods. CONCLUSION: Utilizing the PC may improve initial needle positioning and safety especially off-plane. However, better final needle positioning after correction with the greater freedom of movement method may suggest need for disassembly of the cube.

Evaluation of an augmented reality navigational guidance platform for percutaneous procedures in a cadaver model.

Purpose: The objective of this study is to review the accuracy of an augmented reality navigational guidance system designed to facilitate improved visualization, guidance, and accuracy during percutaneous needle-based procedures including biopsies and ablations. Approach: Using the HoloLens 2, the system registers and projects 3D CT-based models of segmented anatomy along with live ultrasound, fused with electromagnetically tracked instruments including ultrasound probes and needles, giving the operator comprehensive stereoscopic visualization for intraoperative planning and navigation during procedures.Tracked needles were guided to targets implanted in a cadaveric model using the system. Image fusion registration error, the multimodality error measured as the post-registration distance between a corresponding point measured in the stereoscopic CT and tracked ultrasound coordinate systems, and target registration error, the Euclidean distance between needle tip and target after needle placement, were measured as registration and targeting accuracy metrics. A t-distribution was used for statistical analysis. Results: Three operators performed 36 total needle passes, 18 to measure image fusion registration error and 18 to measure target registration error on four targets. The average depth of each needle pass was 8.4 cm from skin to target center. Mean IFRE was 4.4 mm (H0: µ=5 mm, P<0.05). Mean TRE was 2.3 mm (H0: µ=5 mm, P<0.00001). Conclusions: The study demonstrated high registration and targeting accuracy of this AR navigational guidance system in percutaneous, needle-based procedures. This suggests the ability to facilitate improved clinical performance in percutaneous procedures such as ablations and biopsies.

Smartphone application with 3D-printed needle guide for faster and more accurate CT-guided interventions in a phantom.

OBJECTIVE: This study is to determine whether a needle guidance device combining a 3D-printed component with a smartphone would decrease the number of passes and time required to perform a standard CT-guided needle procedure in a phantom study. MATERIALS AND METHODS: A 3D-printed mechanical guide with built-in apertures for various needle sizes was designed and printed. It was mounted on a smartphone and used to direct commercially available spring-loaded biopsy devices. A smartphone software application was developed to use the phone's sensors to provide the real-time location of a lesion in space, based on parameters derived from preprocedural CT images. The physical linkage of the guide, smartphone, and needle allowed the operator to manipulate the assembly as a single unit, with real-time graphical representation of the lesion shown on the smartphone display. Two radiology trainees and 3 staff radiologists targeted 5 lesions with and without the device (50 total procedures). The number of passes and time taken to reach each lesion were determined. RESULTS: Use of the smartphone needle guide decreased the mean number of passes (with guide, 1.8; without guide, 3.4; P < 0.001) and mean time taken (with guide, 1.6 min; without guide, 2.7 min; P = 0.005) to perform a standard CT-guided procedure. On average, the decreases in number of passes and procedure time were more pronounced among trainees (P < 0.001). CONCLUSION: The combination of a mechanical guide and smartphone can reduce the number of needle passes and the amount of time needed to reach a lesion in a phantom for both trainees and experienced radiologists.

CT Navigation for Percutaneous Needle Placement: How I Do It.

CT navigation (CTN) has recently been developed to combine many of the advantages of conventional CT and CT-fluoroscopic guidance for needle placement. CTN systems display real-time needle position superimposed on a CT dataset. This is accomplished by placing electromagnetic (EM) or optical transmitters/sensors on the patient and needle, combined with fiducials placed within the scan field to superimpose a known needle location onto a CT dataset. Advantages of CTN include real-time needle tracking using a contemporaneous CT dataset with the patient in the treatment position, reduced radiation to the physician, facilitation of procedures outside the gantry plane, fewer helical scans during needle placement, and needle guidance based on diagnostic-quality CT datasets. Limitations include the display of a virtual (vs actual) needle position, which can be inaccurate if the needle bends, the fiducial moves, or patient movement occurs between scans, and limitations in anatomical regions with a high degree of motion such as the lung bases. This review summarizes recently introduced CTN technologies in comparison to historical methods of CT needle guidance. A "How I do it" section follows, which describes how CT navigation has been integrated into the study center for both routine and challenging procedures, and includes step-by-step explanations, technical tips, and pitfalls.

Cone-Beam CT With Enhanced Needle Guidance and Augmented Fluoroscopy Overlay: Applications in Interventional Radiology.

Digital flat-panel detector cone-beam CT (CBCT), introduced in the early 2000s, was historically used in interventional radiology primarily for liver-directed therapies. However, contemporary advanced imaging applications, including enhanced needle guidance and augmented fluoroscopy overlay, have evolved substantially over the prior decade and now work synergistically with CBCT guidance to overcome limitations encountered with other imaging modalities. CBCT with advanced imaging applications has become increasingly used to facilitate a broad range of minimally invasive procedures, particularly relating to pain and musculoskeletal interventions. Potential advantages of CBCT with advanced imaging applications include greater accuracy for complex needle paths, improved targeting in the presence of metal artifact, enhanced visualization during injection of contrast medium or cement, increased ease when space in the gantry is limited, and reduced radiation doses versus conventional CT guidance. Nonetheless, CBCT guidance remains underutilized, partly relating to lack of familiarity with the technique. This article describes the practical implementation of CBCT with enhanced needle guidance and augmented fluoroscopy overlay and depicts the technique's application for an array of interventional radiology procedures, including epidural steroid injections, celiac plexus block and neurolysis, pudendal block, spine ablation, percutaneous osseous ablation fixation and osteoplasty, biliary recanalization, and transcaval type II endoleak repair.

Improving puncture accuracy in percutaneous CT-guided needle insertion with wireless inertial measurement unit: a phantom study.

OBJECTIVES: A novel method applying inertial measurement units (IMUs) was developed to assist CT-guided puncture, which enables real-time displays of planned and actual needle trajectories. The method was compared with freehand and laser protractor-assisted methods. METHODS: The phantom study was performed by three operators with 8, 2, and 0 years of experience in CT-guided procedure conducted five consecutive needle placements for three target groups using three methods (freehand, laser protractor-assisted, or IMU-assisted method). The endpoints included mediolateral angle error and caudocranial angle error of the first pass, the procedure time, the total number of needle passes, and the radiation dose. RESULTS: There was a significant difference in the number of needle passes (IMU 1.2 ± 0.42, laser protractor 2.9 ± 1.6, freehand 3.6 ± 2.0 time, p < 0.001), the procedure time (IMU 3.0 ± 1.2, laser protractor 6.4 ± 2.9, freehand 6.2 ± 3.1 min, p < 0.001), the mediolateral angle error of the first pass (IMU 1.4 ± 1.2, laser protractor 1.6 ± 1.3, freehand 3.7 ± 2.5 degree, p < 0.001), the caudocranial angle error of the first pass (IMU 1.2 ± 1.2, laser protractor 5.3 ± 4.7, freehand 3.9 ± 3.1 degree, p < 0.001), and the radiation dose (IMU 250.5 ± 74.1, laser protractor 484.6 ± 260.2, freehand 561.4 ± 339.8 mGy-cm, p < 0.001) among three CT-guided needle insertion methods. CONCLUSION: The wireless IMU improves the angle accuracy and speed of CT-guided needle punctures as compared with laser protractor guidance and freehand techniques. KEY POINTS: • The IMU-assisted method showed a significant decrease in the number of needle passes (IMU 1.2 ± 0.42, laser protractor 2.9 ± 1.6, freehand 3.6 ± 2.0 time, p < 0.001). • The IMU-assisted method showed a significant decrease in the procedure time (IMU 3.0 ± 1.2, laser protractor 6.4 ± 2.9, freehand 6.2 ± 3.1 min, p < 0.001). • The IMU-assisted method showed a significant decrease in the mediolateral angle error of the first pass and the caudocranial angle error of the first pass.

Toward mechatronic MRI-guided focal laser ablation of the prostate: Robust registration for improved needle delivery.

BACKGROUND: Multiparametric MRI (mpMRI) is an effective tool for detecting and staging prostate cancer (PCa), guiding interventional therapy, and monitoring PCa treatment outcomes. MRI-guided focal laser ablation (FLA) therapy is an alternative, minimally invasive treatment method to conventional therapies, which has been demonstrated to control low-grade, localized PCa while preserving patient quality of life. The therapeutic success of FLA depends on the accurate placement of needles for adequate delivery of ablative energy to the target lesion. We previously developed an MR-compatible mechatronic system for prostate FLA needle guidance and validated its performance in open-air and clinical 3T in-bore experiments using virtual targets. PURPOSE: To develop a robust MRI-to-mechatronic system registration method and evaluate its in-bore MR-guided needle delivery accuracy in tissue-mimicking prostate phantoms. METHODS: The improved registration multifiducial assembly houses thirty-six aqueous gadolinium-filled spheres distributed over a 7.3 × 7.3 × 5.2 cm volume. MRI-guided needle guidance accuracy was quantified in agar-based tissue-mimicking prostate phantoms on trajectories (N = 44) to virtual targets covering the mechatronic system's range of motion. 3T gradient-echo recalled (GRE) MRI images were acquired after needle insertions to each target, and the air-filled needle tracks were segmented. Needle guidance error was measured as the shortest Euclidean distance between the target point and the segmented needle trajectory, and angular error was measured as the angle between the targeted trajectory and the segmented needle trajectory. These measurements were made using both the previously designed four-sphere registration fiducial assembly on trajectories (N = 7) and compared with the improved multifiducial assembly using a Mann-Whitney U test. RESULTS: The median needle guidance error of the system using the improved registration fiducial assembly at a depth of 10 cm was 1.02 mm with an interquartile range (IQR) of 0.42-2.94 mm. The upper limit of the one-sided 95% prediction interval of needle guidance error was 4.13 mm. The median (IQR) angular error was 0.0097 rad (0.0057-0.015 rad) with a one-sided 95% prediction interval upper limit of 0.022 rad. The median (IQR) positioning error using the previous four-sphere registration fiducial assembly was 1.87 mm (1.77-2.14 mm). This was found to be significantly different (p = 0.0012) from the median (IQR) positioning error of 0.28 mm (0.14-0.95 mm) using the new registration fiducial assembly on the same trajectories. No significant difference was detected between the medians of the angular errors (p = 0.26). CONCLUSION: This is the first study presenting an improved registration method and validation in tissue-mimicking phantoms of our remotely actuated MR-compatible mechatronic system for delivery of prostate FLA needles. Accounting for the effects of needle deflection, the system was demonstrated to be capable of needle delivery with an error of 4.13 mm or less in 95% of cases under ideal conditions, which is a statistically significant improvement over the previous method. The system will next be validated in a clinical setting.

Real-time three-dimensional fluoroscopy-navigated percutaneous pelvic screw placement for fragility fractures of the pelvis in the hybrid operating room.

BACKGROUND: The prognosis of conservative treatment for fragility fracture of the pelvis (FFP) in the older patients remains poor. Percutaneous pelvic screw placement (PPSP), which aids in the treatment of FFP, can be challenging to perform using fluoroscopy alone because of the proximity of blood vessels and neuroforamina. Hence, this study aimed to investigate the accuracy and clinical outcomes of PPSP using real-time 3D fluoroscopic navigation for FFP in the hybrid operating room. METHODS: This study included 41 patients with FFP who underwent PPSP in a hybrid operating room between April 2016 and December 2020. Intraoperative C-arm cone-beam CT was performed under general anesthesia. Guidewire trajectory was planned using a needle guidance system. The guidewire was inserted along the overlaid trajectory using 3D fluoroscopic navigation, and a 6.5 mm cannulated cancellous screw (CCS) was placed. The clinical outcomes and accuracy of the screw placement were then investigated. RESULTS: A total of 121 screws were placed. The mean operative time was 84 ± 38.7 minutes, and the mean blood loss was 7.6 ± 3.8 g. The mean time to wheelchair transfer was 2 days postoperatively. Pain was relieved in 35 patients. Gait ability from preoperative and latest follow-up after surgery was maintained in 30 (73%) patients. All 41 patients achieved bone union. Of the 121 screws, 119 were grade 0 with no misplacement; only 2 patients had grade 1 perforations. CONCLUSION: PPSP using real-time 3D fluoroscopic navigation in a hybrid operating room was accurate and useful for early mobilization and pain relief among older patients with FFP with an already-installed needle biopsy application.

Value-assessment of computer-assisted navigation strategies during percutaneous needle placement.

PURPOSE: Navigational strategies create a scenario whereby percutaneous needle-based interventions of the liver can be guided using both pre-interventional 3D imaging datasets and dynamic interventional ultrasound (US). To score how such technologies impact the needle placement process, we performed kinematic analysis on different user groups. METHODS: Using a custom biopsy phantom, three consecutive exercises were performed by both novices and experts (n = 26). The exercise came in three options: (1) US-guidance, (2) US-guidance with pre-interventional image-registration (US + Reg) and (3) US-guidance with pre-interventional image-registration and needle-navigation (US + Reg + Nav). The traveled paths of the needle were digitized in 3D. Using custom software algorithms, kinematic metrics were extracted and related to dexterity, decision making indices to obtain overall performance scores (PS). RESULTS: Kinematic analysis helped quantifying the visual assessment of the needle trajectories. Compared to US-guidance, novices yielded most improvements using Reg (PSavg(US) = 0.43 vs. PSavg(US+Reg) = 0.57 vs. PSavg(US+Reg+Nav) = 0.51). Interestingly, the expert group yielded a reversed trend (PSavg(US) = 0.71 vs PSavg(US+Reg) = 0.58 vs PSavg(US+Reg+Nav) = 0.59). CONCLUSION: Digitizing the movement trajectory allowed us to objectively assess the impact of needle-navigation strategies on percutaneous procedures. In particular, our findings suggest that these advanced technologies have a positive impact on the kinematics derived performance of novices.

The Use of a New Device-Assisted Needle Guidance versus Conventional Approach to Perform Ultrasound Guided Brachial Plexus Blockade: A Randomized Controlled Study.

Purpose: Ultrasound guidance during nerve blockade poses the challenge of maintaining in-plane alignment of the needle tip. The needle guidance device maintains needle alignment and assists with in-plane needle visualization. The purpose of this study is to evaluate the utility of this device by comparing procedure performance during brachial plexus blockade with the conventional approach. Methods: After the Institutional Review Board approval and obtaining informed consent, 70 patients receiving either interscalene or supraclavicular nerve blocks were randomly assigned into 2 groups, a conventional approach versus utilizing the needle guidance device. An independent observer recorded: total procedure time; needle insertion time; number of unplanned redirections; and number of reinsertions. Additionally, physician satisfaction and ease of needle visualization were assessed. Results: Data from seventy patients were analyzed. The median [25th percentile-75th percentile] time to complete the block by the device assisted needle guidance group was 3 (2-3.75) minutes and 4 (3-6) minutes in the conventional approach group (p < 0.001). Additionally, subgroup analyses were performed in the supraclavicular block and interscalene block. Supraclavicular blockade, needle insertion time (median [25th percentile-75th percentile] in seconds) (106 [92-162] vs 197 [140-278]), total procedure time (3 [2-3] vs 4.5 [4-6] in minutes) and unplanned needle redirections (2 [1-5] vs 5.5 [3-9]) were significantly lower in needle guidance group (p < 0.001). With interscalene blockade, needle insertion time (86 [76-146] vs 126 [94-295]) and unplanned needle redirections (2 [1-3] vs 4 [2-8.5]) were significantly lower with needle guidance (p < 0.001), but total procedure time was similar. All the physicians reported that they would use the needle guidance again, and 90% would prefer it for in-plane blocks. Conclusion: Performing regional blocks using the needle guidance device reduces needle insertion time and unplanned needle redirections in brachial plexus blockade. Moreover, physician satisfaction also improved compared to the use of the conventional technique.

Evaluation of optical tracking and augmented reality for needle navigation in sacral nerve stimulation.

BACKGROUND AND OBJECTIVE: Sacral nerve stimulation (SNS) is a minimally invasive procedure where an electrode lead is implanted through the sacral foramina to stimulate the nerve modulating colonic and urinary functions. One of the most crucial steps in SNS procedures is the placement of the tined lead close to the sacral nerve. However, needle insertion is very challenging for surgeons. Several x-ray projections are required to interpret the needle position correctly. In many cases, multiple punctures are needed, causing an increase in surgical time and patient's discomfort and pain. In this work we propose and evaluate two different navigation systems to guide electrode placement in SNS surgeries designed to reduce surgical time, minimize patient discomfort and improve surgical outcomes. METHODS: We developed, for the first alternative, an open-source navigation software to guide electrode placement by real-time needle tracking with an optical tracking system (OTS). In the second method, we present a smartphone-based AR application that displays virtual guidance elements directly on the affected area, using a 3D printed reference marker placed on the patient. This guidance facilitates needle insertion with a predefined trajectory. Both techniques were evaluated to determine which one obtained better results than the current surgical procedure. To compare the proposals with the clinical method, we developed an x-ray software tool that calculates a digitally reconstructed radiograph, simulating the fluoroscopy acquisitions during the procedure. Twelve physicians (inexperienced and experienced users) performed needle insertions through several specific targets to evaluate the alternative SNS guidance methods on a realistic patient-based phantom. RESULTS: With each navigation solution, we observed that users took less average time to complete each insertion (36.83 s and 44.43 s for the OTS and AR methods, respectively) and needed fewer average punctures to reach the target (1.23 and 1.96 for the OTS and AR methods respectively) than following the standard clinical method (189.28 s and 3.65 punctures). CONCLUSIONS: To conclude, we have shown two navigation alternatives that could improve surgical outcome by significantly reducing needle insertions, surgical time and patient's pain in SNS procedures. We believe that these solutions are feasible to train surgeons and even replace current SNS clinical procedures.

Technical feasibility and efficacy of a standard needle magnetization system for ultrasound needle guidance in thyroid nodule-targeting punctures: a phantom study.

PURPOSE: The aim of this study was to assess the feasibility and efficacy of an ultrasound needle guidance system (NGS) based on standard needle magnetization in a phantom study of thyroid nodule (TN)-targeting punctures. METHODS: Six trainees and a staff radiologist performed TN-targeting punctures with or without the NGS in phantom models (group 1, experience <50 cases; group 2, experience ≥50 cases and <100 cases; group 3, experience ≥100 cases of TN-targeting punctures). The feasibility, technical success rate, number of punctures, and procedure time were recorded. RESULTS: The feasibility of NGS was 98.6% (138/140). In group 1, the technical success rate increased from 60.0%±8.2% to 80.0%±8.2% when the NGS was used (P=0.046), with a reduction in the number of punctures from 2.2 to 1.2 (P=0.005). In group 2, the rate changed from 95.0%±5.8% to 100.0%±0.0% with the NGS (P=0.157), with a minimal decrease in the number of punctures from 1.1 to 1.0 (P=0.157). The procedure time significantly decreased in both groups (P=0.041 and P=0.010, respectively) when the NGS was used. In group 3, there were no significant differences in the technical success rate and the number of punctures according to whether the NGS was used (P=0.317 and P=0.317, respectively). CONCLUSION: NGS using standard needle magnetization is technically feasible and has potential to improve the efficacy of TN-targeting punctures for less-experienced operators, especially beginners, according to the findings of this phantom study.

Computer-aided Veress needle guidance using endoscopic optical coherence tomography and convolutional neural networks.

During laparoscopic surgery, the Veress needle is commonly used in pneumoperitoneum establishment. Precise placement of the Veress needle is still a challenge for the surgeon. In this study, a computer-aided endoscopic optical coherence tomography (OCT) system was developed to effectively and safely guide Veress needle insertion. This endoscopic system was tested by imaging subcutaneous fat, muscle, abdominal space, and the small intestine from swine samples to simulate the surgical process, including the situation with small intestine injury. Each tissue layer was visualized in OCT images with unique features and subsequently used to develop a system for automatic localization of the Veress needle tip by identifying tissue layers (or spaces) and estimating the needle-to-tissue distance. We used convolutional neural networks (CNNs) in automatic tissue classification and distance estimation. The average testing accuracy in tissue classification was 98.53 ± 0.39%, and the average testing relative error in distance estimation reached 4.42 ± 0.56% (36.09 ± 4.92 µm).

Humanin vivoliver and tumor bioimpedance measured with biopsy needle.

Objective.Liver biopsy is an essential procedure in cancer diagnostics but targeting the biopsy to the actual tumor tissue is challenging. Aim of this study was to evaluate the clinical feasibility of a novel bioimpedance biopsy needle system in liver biopsy and simultaneously to gatherin vivobioimpedance data from human liver and tumor tissues.Approach.We measured human liver and tumor impedance datain vivofrom 26 patients who underwent diagnostic ultrasound-guided liver biopsy. Our novel 18 G core biopsy needle tip forms a bipolar electrode that was used to measure bioimpedance during the biopsy in real-time with frequencies from 1 kHz to 349 kHz. The needle tip location was determined by ultrasound. Also, the sampled tissue type was determined histologically.Main results.The bioimpedance values showed substantial variation between individual cases, and liver and tumor data overlapped each other. However, Mann-Whitney U test showed that the median bioimpedance values of liver and tumor tissue are significantly (p < 0.05) different concerning the impedance magnitude at frequencies below 25 kHz and the phase angle at frequencies below 3 kHz and above 30 kHz.Significance.This study uniquely employed a real-time bioimpedance biopsy needle in clinical liver biopsies and reported the measured humanin vivoliver and tumor impedance data. Impedance is always device-dependent and therefore not directly comparable to measurements with other devices. Although the variation in tumor types prevented coherent tumor identification, our study provides preliminary evidence that tumor tissue differs from liver tissuein vivo,and this association is frequency-dependent.

Mixed Reality Needle Guidance Application on Smartglasses Without Pre-procedural CT Image Import with Manually Matching Coordinate Systems.

PURPOSE: To develop and assess the accuracy of a mixed reality (MR) needle guidance application on smartglasses. MATERIALS AND METHODS: An MR needle guidance application on HoloLens2, without pre-procedural CT image reconstruction or import by manually matching the spatial and MR coordinate systems, was developed. First, the accuracy of the target locations in the image overlay at 63 points arranged on a 45 × 35 × 21 cm box and needle angles from 0° to 80°, placed using the MR application, was verified. The needle placement errors from 12 different entry points in a phantom by seven operators (four physicians and three non-physicians) were compared using a linear mixed model between the MR guidance and conventional methods using protractors. RESULTS: The average errors of the target locations and needle angles placed using the MR application were 5.9 ± 2.6 mm and 2.3 ± 1.7°, respectively. The average needle insertion error using the MR guidance was slightly smaller compared to that using the conventional method (8.4 ± 4.0 mm vs. 9.6 ± 5.1 mm, p = 0.091), particularly in the out-of-plane approach (9.6 ± 3.5 mm vs. 12.3 ± 4.6 mm, p = 0.003). The procedural time was longer with MR guidance than with the conventional method (412 ± 134 s vs. 219 ± 66 s, p < 0.001). CONCLUSION: MR needle guidance without pre-procedural CT image import is feasible when matching coordinate systems, and the accuracy of needle insertion is slightly better than that of the conventional method.

Intraoperative disc level marking with needle: a technical note and prospective study on 30 patients.

BACKGROUND: Wrong-level surgery is a rare but unresolved issue in spine surgery. Some proposed protocols with high success rates, but it remains a risk with potential complications for the patient. Surgical navigation offers more accurate surgery, without additional irradiation related to the imaging device, in order to optimize the surgical guidance. METHODS: We describe our institutional technique with a needle placed under fluoroscopy at 3 cm from the incision line at the disc level to be operated, in order to guide the surgical approach; and we report a prospective evaluation of all patients during a six-month period operated by microdiscectomy for symptomatic lumbar discus hernia, whose hernia level was landmarked with this technique. We collected demographic, clinical-such as visual analog scale (VAS) of pain and Oswestry disability index (ODI) scores-operative and irradiation data for effective dose calculation. RESULTS: Thirty patients were included in the study. No wrong-level procedure was performed. Mean time for landmarking was 2.22 [1-5] minutes. Average operative time was 54.5 [30-150] minutes. The effective dose related to the imaging device use was 0.032 (0.007-0.092) mSv. The effective dose was also correlated to body mass index and disc level (P=0.05). The operative duration, complication rate and postoperative VAS and ODI scores were similar to the current literature. CONCLUSIONS: We advocate the use of percutaneous needle guidance, avoiding wrong-level microdiscectomy and helping the surgeon as a "navigation-like" device with minimal additional irradiation for the patient.

Design and validation of an MRI-compatible mechatronic system for needle delivery to localized prostate cancer.

PURPOSE: Prostate cancer is the most common non-cutaneous cancer among men in the United States and is the second leading cause of cancer death in American men. (Siegel et al. [2019] CA: A Cancer J Clin.69(1):7-34.) Focal laser ablation (FLA) has the potential to control small tumors while preserving urinary and erectile function by leaving the neurovascular bundles and urethral sphincters intact. Accurate needle guidance is critical to the success of FLA. Multiparametric magnetic resonance images (mpMRI) can be used to identify targets, guide needles, and assess treatment outcomes. The purpose of this work was to design and evaluate the accuracy of an MR-compatible mechatronic system for in-bore transperineal guidance of FLA ablation needles to localized lesions in the prostate. METHODS: The mechatronic system was constructed entirely of non-ferromagnetic materials, with actuation controlled by piezoelectric motors and optical encoders. The needle guide hangs between independent front and rear two-link arms, which allows for horizontal and vertical translation as well as pitch and yaw rotation of the guide with a 6.0 cm range of motion in each direction. Needles are inserted manually through a chosen hole in the guide, which has been aligned with the target in the prostate. Open-air positioning error was evaluated using an optical tracking system (0.25 mm RMS accuracy) to measure 125 trajectories in free space. Correction of systematic bias in the system was performed using 85 of the trajectories, and the remaining 40 were used to estimate the residual error. The error was calculated as the horizontal and vertical displacement between the axis of the desired and measured trajectories at a typical needle insertion depth of 10 cm. MR-compatibility was evaluated using a grid phantom to assess image degradation due to the presence of the system, and induced force, heating, and electrical interference in the system were assessed qualitatively. In-bore positioning error was evaluated on 25 trajectories. RESULTS: Open-air mean positioning error at the needle tip was 0.80 ± 0.36 mm with a one-sided 95% confidence interval of 1.40 mm. The mean deviation of needle trajectories from the planned direction was 0.14 ± 0.06∘ . In the MR bore, the mean positioning error at the needle tip was 2.11 ± 1.05 mm with a one-sided 95% prediction interval of 3.84 mm. The mean angular error was 0.49 ± 0.26∘ . The system was found to be compatible with the MR environment under the specified gradient-echo sequence parameters used in this study. CONCLUSION: A complete system for delivering needles to localized prostate tumors was developed and described in this work, and its compatibility with the MR environment was demonstrated. In-bore MRI positioning error was sufficiently small for targeting small localized prostate tumors.

Smartphone- versus smartglasses-based augmented reality (AR) for percutaneous needle interventions: system accuracy and feasibility study.

PURPOSE: To compare the system accuracy and needle placement performance of smartphone- and smartglasses-based augmented reality (AR) for percutaneous needle interventions. METHODS: An AR platform was developed to enable the superimposition of annotated anatomy and a planned needle trajectory onto a patient in real time. The system accuracy of the AR display on smartphone (iPhone7) and smartglasses (HoloLens1) devices was evaluated on a 3D-printed phantom. The target overlay error was measured as the distance between actual and virtual targets (n = 336) on the AR display, derived from preprocedural CT. The needle overlay angle was measured as the angular difference between actual and virtual needles (n = 12) on the AR display. Three operators each used the iPhone (n = 8), HoloLens (n = 8) and CT-guided freehand (n = 8) to guide needles into targets in a phantom. Needle placement error was measured with post-placement CT. Needle placement time was recorded from needle puncture to navigation completion. RESULTS: The target overlay error of the iPhone was comparable to the HoloLens (1.75 ± 0.59 mm, 1.74 ± 0.86 mm, respectively, p = 0.9). The needle overlay angle of the iPhone and HoloLens was similar (0.28 ± 0.32°, 0.41 ± 0.23°, respectively, p = 0.26). The iPhone-guided needle placements showed reduced error compared to the HoloLens (2.58 ± 1.04 mm, 3.61 ± 2.25 mm, respectively, p = 0.05) and increased time (87 ± 17 s, 71 ± 27 s, respectively, p = 0.02). Both AR devices reduced placement error compared to CT-guided freehand (15.92 ± 8.06 mm, both p < 0.001). CONCLUSION: An augmented reality platform employed on smartphone and smartglasses devices may provide accurate display and navigation guidance for percutaneous needle-based interventions.

Simulated accuracy assessment of small footprint body-mounted probe alignment device for MRI-guided cryotherapy of abdominal lesions.

PURPOSE: Magnetic resonance imaging (MRI)-guided percutaneous cryotherapy of abdominal lesions, an established procedure, uses MRI to guide and monitor the cryoablation of lesions. Methods to precisely guide cryotherapy probes with a minimum amount of trial-and-error are yet to be established. To aid physicians in attaining precise probe alignment without trial-and-error, a body-mounted motorized cryotherapy-probe alignment device (BMCPAD) with motion compensation was clinically tested in this study. The study also compared the contribution of body motion and organ motion compensation to the guidance accuracy of a body-mounted probe alignment device. METHODS: The accuracy of guidance using the BMCPAD was prospectively measured during MRI-guided percutaneous cryotherapies before insertion of the probes. Clinical parameters including patient age, types of anesthesia, depths of the target, and organ sites of target were collected. By using MR images of the target organs and fiducial markers embedded in the BMCPAD, we retrospectively simulated the guidance accuracy with body motion compensation, organ motion compensation, and no compensation. The collected data were analyzed to test the impact of motion compensation on the guidance accuracy. RESULTS: Thirty-seven physical guidance of probes were prospectively recorded for sixteen completed cases. The accuracy of physical guidance using the BMCPAD was 13.4 ± 11.1 mm. The simulated accuracy of guidance with body motion compensation, organ motion compensation, and no compensation was 2.4 ± 2.9 mm, 2.2 ± 1.6 mm, and 3.5 ± 2.9 mm, respectively. Data analysis revealed that the body motion compensation and organ motion compensation individually impacted the improvement in the accuracy of simulated guidance. Moreover, the difference in the accuracy of guidance either by body motion compensation or organ motion compensation was not statistically significant. The major clinical parameters impacting the accuracy of guidance were the body and organ motions. Patient age, types of anesthesia, depths of the target, and organ sites of target did not influence the accuracy of guidance using BMCPAD. The magnitude of body surface movement and organ movement exhibited mutual statistical correlation. CONCLUSIONS: The BMCPAD demonstrated guidance accuracy comparable to that of previously reported devices for CT-guided procedures. The analysis using simulated motion compensation revealed that body motion compensation and organ motion compensation individually impact the improvement in the accuracy of device-guided cryotherapy probe alignment. Considering the correlation between body and organ movements, we also determined that body motion compensation using the ring fiducial markers in the BMCPAD can be solely used to address both body and organ motions in MRI-guided cryotherapy.

Smartphone Augmented Reality CT-Based Platform for Needle Insertion Guidance: A Phantom Study.

OBJECTIVE: To develop and assess the accuracy of an augmented reality (AR) needle guidance smartphone application. METHODS: A needle guidance AR smartphone application was developed using Unity and Vuforia SDK platforms, enabling real-time displays of planned and actual needle trajectories. To assess the application's accuracy in a phantom, eleven operators (including interventional radiologists, non-interventional radiology physicians, and non-physicians) performed single-pass needle insertions using AR guidance (n = 8) and CT-guided freehand (n = 8). Placement errors were measured on post-placement CT scans. Two interventional radiologists then used AR guidance (n = 3) and CT-guided freehand (n = 3) to navigate needles to within 5 mm of targets with intermediate CT scans permitted to mimic clinical use. The total time and number of intermediate CT scans required for successful navigation were recorded. RESULTS: In the first experiment, the average operator insertion error for AR-guided needles was 78% less than that for CT-guided freehand (2.69 ± 2.61 mm vs. 12.51 ± 8.39 mm, respectively, p < 0.001). In the task-based experiment, interventional radiologists achieved successful needle insertions on each first attempt when using AR guidance, thereby eliminating the need for intraoperative CT scans. This contrasted with 2 ± 0.9 intermediate CT scans when using CT-guided freehand. Additionally, average procedural times were reduced from 13.1 ± 6.6 min with CT-guided freehand to 4.5 ± 1.3 min with AR guidance, reflecting a 66% reduction. CONCLUSIONS: All operators exhibited superior needle insertion accuracy when using the smartphone-based AR guidance application compared to CT-guided freehand. This AR platform can potentially facilitate percutaneous biopsies and ablations by improving needle insertion accuracy, expediting procedural times, and reducing radiation exposures.