Real-time, image-based slice-to-volume registration for ultrasound-guided spinal intervention

[Comparison of screw placement guided by O-arm navigation and ultrasound volume navigation in minimally invasive transforaminal lumbar interbody fusion]

Objective

To compare the effectiveness of O-arm navigation and ultrasound volume navigation (UVN) in guiding screw placement during minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) surgery.

Methods

Sixty patients who underwent MIS-TLIF surgery for lumbar disc herniation between June 2022 and June 2023 and met the selection criteria were included in the study. They were randomly assigned to group A (screw placement guided by UVN during MIS-TLIF) or group B (screw placement guided by O-arm navigation during MIS-TLIF), with 30 cases in each group. There was no significant difference in baseline data, including gender, age, body mass index, and surgical segment, between the two groups ( P>0.05). Intraoperative data, including average single screw placement time, total radiation dose, and average single screw effective radiation dose, were recorded and calculated. Postoperatively, X-ray film and CT scans were performed at 10 days to evaluate screw placement accuracy and assess facet joint violation. Pearson correlation and Spearman correlation analyses were used to observe the relationship between the studied parameters (average single screw placement time and screw placement accuracy grading) and BMI.

Results

The average single screw placement time in group B was significantly shorter than that in group A, and the total radiation dose of single segment and multi-segment and the average single screw effective radiation dose in group B were significantly higher than those in group A ( P<0.05). There was no significant difference in the total radiation dose between single segment and multiple segments in group B ( P>0.05), while the total radiation dose of multiple segments was significantly higher than that of single segment in group A ( P<0.05). No significant difference was found in the accuracy of screw implantation between the two groups ( P>0.05). In both groups, the grade 1 and grade 2 screws broke through the outer wall of the pedicle, and no screw broke through the inner wall of the pedicle. There was no significant difference in the rate of facet joint violation between the two groups ( P>0.05). In group A, both the average single screw placement time and screw placement accuracy grading were positively correlated with BMI ( r=0.677, P<0.001; r=0.222, P=0.012), while in group B, neither of them was correlated with BMI ( r=0.224, P=0.233; r=0.034, P=0.697).

Conclusion

UVN-guided screw placement in MIS-TLIF surgery demonstrates comparable efficiency, visualization, and accuracy to O-arm navigation, while significantly reducing radiation exposure. However, it may be influenced by factors such as obesity, which poses certain limitations.

Wearable Mechatronic Ultrasound-integrated AR Navigation System for Lumbar Puncture Guidance

As one of the most commonly performed spinal interventions in routine clinical practice, lumbar punctures are usually done with only hand palpation and trial-and-error. Failures can prolong procedure time and introduce complications such as cerebrospinal fluid leaks and headaches. Therefore, an effective needle insertion guidance method is desired. In this work, we present a complete lumbar puncture guidance system with the integration of (1) a wearable mechatronic ultrasound imaging device, (2) volume-reconstruction and bone surface estimation algorithms and (3) two alternative augmented reality user interfaces for needle guidance, including a HoloLens-based and a tablet-based solution. We conducted a quantitative evaluation of the end-to-end navigation accuracy, which shows that our system can achieve an overall needle navigation accuracy of 2.83 mm and 2.76 mm for the Tablet-based and the HoloLens-based solutions, respectively. In addition, we conducted a preliminary user study to qualitatively evaluate the effectiveness and ergonomics of our system on lumbar phantoms. The results show that users were able to successfully reach the target in an average of 1.12 and 1.14 needle insertion attempts for Tablet-based and HoloLens-based systems, respectively, exhibiting the potential to reduce the failure rates of lumbar puncture procedures with the proposed lumbar-puncture guidance.

The Feasibility of Haar Feature-Based Endoscopic Ultrasound Probe Tracking for Implanting Hydrogel Spacer in Radiation Therapy for Pancreatic Cancer

Purpose

We proposed a Haar feature-based method for tracking endoscopic ultrasound (EUS) probe in diagnostic computed tomography (CT) and Magnetic Resonance Imaging (MRI) scans for guiding hydrogel injection without external tracking hardware. This study aimed to assess the feasibility of implementing our method with phantom and patient images.

Materials and Methods

Our methods included the pre-simulation section and Haar features extraction steps. Firstly, the simulated EUS set was generated based on anatomic information of interpolated CT/MRI images. Secondly, the efficient Haar features were extracted from simulated EUS images to create a Haar feature dictionary. The relative EUS probe position was estimated by searching the best matched Haar feature vector of the dictionary with Haar feature vector of target EUS images. The utilization of this method was validated using EUS phantom and patient CT/MRI images.

Results

In the phantom experiment, we showed that our Haar feature-based EUS probe tracking method can find the best matched simulated EUS image from a simulated EUS dictionary which includes 123 simulated images. The errors of all four target points between the real EUS image and the best matched EUS images were within 1 mm. In the patient CT/MRI scans, the best matched simulated EUS image was selected by our method accurately, thereby confirming the probe location. However, when applying our method in MRI images, our method is not always robust due to the low image resolution.

Conclusions

Our Haar feature-based method is capable to find the best matched simulated EUS image from the dictionary. We demonstrated the feasibility of our method for tracking EUS probe without external tracking hardware, thereby guiding the hydrogel injection between the head of the pancreas and duodenum.

The state-of-the-art in ultrasound-guided spine interventions

During the last two decades, intra-operative ultrasound (iUS) imaging has been employed for various surgical procedures of the spine, including spinal fusion and needle injections. Accurate and efficient registration of pre-operative computed tomography or magnetic resonance images with iUS images are key elements in the success of iUS-based spine navigation. While widely investigated in research, iUS-based spine navigation has not yet been established in the clinic. This is due to several factors including the lack of a standard methodology for the assessment of accuracy, robustness, reliability, and usability of the registration method. To address these issues, we present a systematic review of the state-of-the-art techniques for iUS-guided registration in spinal image-guided surgery (IGS). The review follows a new taxonomy based on the four steps involved in the surgical workflow that include pre-processing, registration initialization, estimation of the required patient to image transformation, and a visualization process. We provide a detailed analysis of the measurements in terms of accuracy, robustness, reliability, and usability that need to be met during the evaluation of a spinal IGS framework. Although this review is focused on spinal navigation, we expect similar evaluation criteria to be relevant for other IGS applications.

Augmented Reality Guided Needle Biopsy of Soft Tissue: A Pilot Study

Percutaneous biopsies are popular for extracting suspicious tissue formations (primarily for cancer diagnosis purposes) due to the: relatively low cost, minimal invasiveness, quick procedure times, and low risk for the patient. Despite the advantages provided by percutaneous biopsies, poor needle and tumor visualization is a problem that can result in the clinicians classifying the tumor as benign when it was malignant (false negative). The system developed by the authors aims to address the concern of poor needle and tumor visualization through two virtualization setups. This system is designed to track and visualize the needle and tumor in three-dimensional space using an electromagnetic tracking system. User trials were conducted in which the 10 participants, who were not medically trained, performed a total of 6 tests, each guiding the biopsy needle to the desired location. The users guided the biopsy needle to the desired point on an artificial spherical tumor (diameters of 30, 20, and 10 mm) using the 3D augmented reality (AR) overlay for three trials and a projection on a second monitor (TV) for the other three trials. From the randomized trials, it was found that the participants were able to guide the needle tip 6.5 ± 3.3 mm away from the desired position with an angle deviation of 1.96 ± 1.10° in the AR trials, compared to values of 4.5 ± 2.3 mm and 2.70 ± 1.67° in the TV trials. The results indicate that for simple stationary surgical procedures, an AR display is non-inferior a TV display.