This study evaluates a fused-data transrectal electrical impedance tomography (TREIT) method for prostate cancer imaging on a set of 22 ex vivo prostates. A previously optimized TREIT algorithm is utilized, and novel validation and fusion approaches leveraging pathology information are considered. Overall, the aim was to increase the sensed volume of a standard 12-core prostate biopsy by adding TREIT imaging. Two TREIT approaches were considered: 1. including prostate boundary information (EIT-P) and 2. including prostate and tumor boundary information (EIT-P+T). Both simple electrical impedance spectroscopy (EIS) metrics and the two imaging approaches (EIT-P and EIT-P+T) were evaluated with respect to biopsy core, 3D (EIT-P) image, and tumor-grade data. Best AUCs of 0.85, 0.84, and 0.83 were found when considering increasing volumes of tissue (0.8%, 2.7%, and 15% of the prostate). The largest measurement volume (15%), which utilized EIT-P, sensed significantly more prostate tissue than the standard biopsy only approach (<1%). These represent large improvement compared to prior clinical EIS biopsy and TREIT studies. Tumor-grade analysis (via EIT-P+T) appears to show promise but more data is required to confirm this. Overall, the study made important strides in developing the TREIT technique and further investigation, likely in an in vivo study, appears merited.

Background:Transcranial temporal interference stimulation (tTIS) is an emerging noninvasive neuromodulation approach that enables focal, frequency-specific modulation of deep brain regions, offering a novel method for investigating therapeutic mechanisms underlying brain and mental health disorders. Pain is a key target because it is a feature of multiple disorders and is increasingly understood to depend on brain circuits. Here, we tested the effects of tTIS on bilateral evoked pain, capitalizing on converging evidence from human and animal studies indicating that the primary motor cortex (M1) contains body-wide inter-effector regions and has descending projections to regions implicated in nociceptive, motivational, and autonomic processing, making it a key cortical target for pain modulation. Methods:We conducted a pre-registered, triple-blind, randomized crossover study (N = 32, 160 study sessions), investigating frequency-dependent effects of tTIS applied to the left M1 on experimentally evoked thermal pain in healthy adults. We tested four stimulation frequencies (10 Hz, 20 Hz, 70 Hz, and sham) on separate days (>10,000 pain trials total). Noxious heat was applied to both the right and left forearms using individually calibrated temperatures both pre- and post-stimulation. Results:Active tTIS produced significant analgesia at all stimulation frequencies (10 Hz, 20 Hz, and 70 Hz) relative to sham (Cohen's d = 0.46-0.82, all p < 0.05). 10 Hz produced the greatest reduction (d = 0.82), and both 10 Hz and 20 Hz produced more analgesia than 70 Hz (d = 0.44 and 0.38, respectively; p < 0.05). Stimulation-related sensations were equivalent across frequencies, and participants were blind to condition. Pain reductions remained stable over a ~40-min post-stimulation period and were bilateral, consistent with stimulation of body-wide inter-effector regions. Conclusions:These results provide the first evidence that tTIS can reliably reduce experimental pain perception in humans in a frequency-dependent manner, providing a foundation for noninvasive pain modulation with tTIS.

This paper describes the design of a small form-factor, low-cost, portable electrical impedance tomography (EIT) system with a custom analog front end and field-programmable gate array (FPGA) controller. Detailed analog and digital design choices are presented and discussed in the context of currently available state-of-the art hardware components and in relation to EIT-driven system requirements. The system is capable of acquisition speeds required for real-time imaging under appropriate acquisition configurations, provides high-SNR measurements over the 100 Hz to 1 MHz target bandwidth, and has customizable acquisition parameters to allow users to optimize the system for a wide variety of imaging applications. Hardware characterization results demonstrate competitive performance relative to existing small form-factor EIT systems, while multi-frequency imaging results demonstrate successful EIT image reconstruction across the evaluated frequency range. The development of this highly configurable, high-performing, portable EIT system provides a significant step toward expanding the practical use of multi-application, real-time EIT imaging.

Objective: Positive margins in oral squamous cell carcinoma (OSCC) resection are common and significantly impact patient outcomes. Electrical impedance tomography (EIT) can be used to intraoperatively distinguish cancer from healthy tissue. The objective of this study was to develop and identify a fused EIT approach to accurately reconstruct a tumor boundary using multiple impedance measurements recorded with a handheld electrical impedance probe. Approach: Simulations and noise analyses were used to investigate the best reconstruction method for fused EIT, and a measured phantom experiment was conducted to evaluate the EIT reconstructions. Main results: Fused approaches successfully and accurately recovered the conductivity boundary location from multiple probe sites, increasing boundary localization to within 0.5 mm of the true boundary for both simulated and experimental results. Simulations and noise analysis revealed that all reconstruction methods maintain strong classification accuracy with added noise on a half-plane boundary scenario and fused difference EIT is the most robust to all types of added noise, due to the high data redundancy in the reconstruction formulation. Significance: The measured multi-site probe experiments represent important steps in the development of an approach that can combine EIT from multiple locations to increase boundary localization accuracy. Overall, this result is a step towards a clinically deployable impedance imaging approach to scanning the entire tumor boundary, which could significantly help to improve surgical outcomes for OSCC.

Transoral robotic surgery (TORS) is a minimally invasive, inside-out technique that, compared with traditional open approaches, provides fewer post-operative complications, shorter hospital stays, and improved survival for early-stage head and neck cancer. However, TORS is limited by its steep learning curve and poor visualization of deep tumor margins. This randomized crossover study evaluated a surgical navigation system’s potential to enhance accuracy and user experience with real-time, instrument-relative feedback. Seven Teflon beads (d = 2.381 mm) were embedded at the tongue base of a porcine pharynx-and-larynx model. Tongue blade compression and retraction were applied to the model to mimic intraoperative tissue deformation, reproducing the anatomical shifts that occur relative to preoperative imaging. Eight participants used the da Vinci Surgical system to localize the beads by placing pins under two conditions: (a) preoperative computed tomography with no navigation; (b) model-based visual navigation with quantitative instrument-to-target metrics. Surgical accuracy was determined by calculating the target localization error (TLE, pin-to-bead Euclidean distance) and the angular error (AE, pin axis trajectory to bead). Accounting for training level and bead depth, surgical navigation reduced TLE by 5.44 mm (95

Accurate endoscope tracking is essential for registering reconstructed 3D models to the surgical view in image-guided robotic procedures. In this preliminary study, we quantitatively evaluated two tracking methods for a da Vinci Xi endoscope: robot kinematics and an external optical tracking system. A known checkerboard pattern was transformed into endoscope left-eye frame using transformations derived from both methods and then reprojected onto left-eye's 2D image plane using camera parameters, and reprojection error was computed against the ground truth detected by OpenCV. Results demonstrate that the optical tracker achieves significantly higher accuracy than kinematics (RMSE: 2.952 pixels < 5.692 pixels, p = 0.0163), providing guidance for tracking strategies in future surgical systems.

In this study we present a beacon-based framework for intraoperative deep-margin localization during transoral surgery (TOS) for oropharyngeal squamous cell carcinoma (OPSCC), designed to operate despite significant macroscopic tissue deformation and topological evolution. The method estimates 3D beacon position from probe measurements using robust plane least-squares fitting and sphere multilateration with sequential filtering, augmented by scale-bias correction and directional regularization to improve stability under noise. In hardware-based simulation with injected noise, the approach consistently achieves submillimeter localization accuracy. We also perform a bench-level verification study localizing a Magseed beacon with a Sentimag probe while optically tracking probe motion with optical tracker and recording the Sentimag display with synchronized video. The pipeline aligns video frames to the optical tracker time base to associate each digit update with the corresponding probe pose in a common reference frame before estimating beacon location. These preliminary results support feasibility for real-time deep-margin tracking and motivate ongoing work on joint optimization of beacon design and probe modality, real-time integration of beacon output into the estimator, deployment strategies, and multi-beacon discrimination using more advanced statistical techniques.

OBJECTIVE:To evaluate a new non-invasive, handheld Electrical Impedance Spectroscopy (EIS) device for assessing oral lesions in real-life surgical scenarios. METHODS:A custom-designed probe with a 33-electrode sensor array was used to collect impedance measurements across multiple frequencies (100 Hz - 100 kHz) from non-consecutive patients undergoing surgical resection of oral cancer. In vivo EIS measurements were recorded from lesion and healthy tissue surfaces before resection, with no clinical decisions based on impedance data. RESULTS:The study included 26 participants (median [IQR] age, 64.3 [59 - 70] years; 11 (42%) female) with oral squamous cell carcinoma. Cancerous tissue was found to have significantly lower resistance and reactance than healthy tissue (p<0.0001). Tissue classification using the permittivity at 40 kHz showed the highest accuracy (88%) with an AUC of 0.88. Multiple impedance parameters achieved AUCs >0.85 for differentiating healthy from malignant tissue. Conclusion & Significance: The study indicates that EIS can effectively differentiate between healthy and cancerous oral mucosa through rapid, non-invasive intraoperative measurements. The data processing pipeline developed demonstrates success in maintaining high data quality amidst the external disturbances presented in intraoperative data collection.

This study investigates external compensation strategies to improve stability and bandwidth of an inverting negative dual configuration (INDC) Howland current source for electrical impedance tomography (EIT) applications. Fifteen compensation schemes were simulated and experimentally tested for an INDC Howland topology designed to output 100-350 mu A across resistive (100 Omega-20 k Omega) and complex (parallel RC) loads. Performance was evaluated based on phase margin, AC peaking, flatness, percent error, and -3-dB bandwidth across 100 Hz-20 MHz. The six best performing topologies were identified and underwent the full analysis. The best performing design incorporates Miller compensation capacitors at three locations (Cf-, Cf+, C-g) with a 5 MHz pole frequency. Simulations demonstrated -3-dB bandwidth >= 1 MHz for loads <= 15 k Omega, with a phase margin >= 60 degrees at 1 MHz for all loads. Experimentally, -3-dB bandwidth >= 1 MHz was maintained up to 3 k Omega, with a phase margin >= 60 degrees at 1 MHz for all loads. Compared with previous literature, our design achieved a > 2x improvement in flatness experimentally (1.86% vs. 4% up to 1 MHz) and extended stable operation to higher frequencies and larger load ranges. External compensation methods improve performance and stability beyond what internal op-amp compensation alone achieves. Performance advantages were validated across a broader frequency and load range than previous INDC Howland implementations. This work establishes a systematic framework for examining broadband current sources for EIT, enabling accurate, stable current injection across clinically relevant impedance ranges and frequencies up to 1 MHz.

Breast cancer is the most frequently diagnosed cancer in women in the United States (excluding skin cancers), and improvements in screening and diagnosis could reduce unnecessary biopsies while enabling earlier detection and better treatment outcomes. Ultrasound tomography (UST) is a novel imaging technique that not only provides structural information but also generates quantitative tissue acoustic maps, such as sound speed and attenuation, which are emerging as valuable biomarkers. While UST improves sensitivity and specificity compared to standard ultrasound, its specificity can be further enhanced by integration with cancer-specific biomarkers. Electrical impedance tomography (EIT), in comparison, provides low-resolution static and dynamic electricalproperty information with promising contrast mechanisms for breast cancer imaging. Incorporating the highresolution structural information from UST can significantly improve EIT reconstructions, overcoming this limitation. Moreover, the geometry of UST ring transducers and EIT electrode arrays allows for straightforward integration of the two modalities into a single system. To the best of our knowledge, this study is the first to explore a combined UST/EIT system and evaluate its performance in a proof-of-principle breast phantom. Our findings show that incorporating boundary information from UST dramatically improves EIT reconstructions, successfully revealing tumor inclusions that were completely obscured without this information. Together, these results suggest that the development of a combined UST/EIT platform offers strong potential as a powerful tool for breast cancer screening and diagnosis.

Bioimpedance analysis is a promising technology for real-time surgical margin assessment (SMA) during prostate cancer surgery, but its clinical adoption is hindered by bulky analog front-end (AFE) hardware. This paper introduces a hardware-efficient algorithm for SMA that relaxes the AFE requirements, allowing for significant miniaturization. The algorithm was evaluated on bioimpedance measurements of e chi vivo prostate tissue, where it achieved an AUROC of 0.84 in detecting cancerous regions of 2.33 mm or larger. The proposed AFE and algorithm would occupy an estimated chip area of 4 mm(2), which is small enough for integration into an SMA probe head. This offers a path to a real-time, intraoperative solution for surgical margin assessment during radical prostatectomy.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique with growing potential for pain modulation. However, previous studies have often been limited by small sample sizes, limited outcome reliability, and blinding issues. Pre-registered randomized trials are needed to establish efficacy and reproducibility. Here, we report results from a pre-registered, triple-blind, randomized within-subject crossover trial (N = 50), investigating the effects of left motor cortex (M1) tDCS on experimentally evoked thermal pain in healthy adults. Participants underwent individualized pain calibration, then received anodal, cathodal, and sham M1-tDCS in counterbalanced order on separate visits 4 or more days apart. We assessed post-tDCS thermal pain, potential blinding, side effects, and reaction time during pain rating. Anodal tDCS significantly reduced pain compared with cathodal and sham stimulation ( P < 0.001, Cohen's d = 0.93 and 0.85, respectively; P < 0.001). Cathodal tDCS increased pain relative to sham (Cohen's d = 0.34, P < 0.01). These effects remained stable throughout the 35-minute post-tDCS pain testing period, with no evidence of decay over time. Blinding assessments confirmed that participants were unable to reliably identify the sham session. Anodal tDCS also modestly increased reaction time in the left (ipsilateral) hand ( P < 0.05, Cohen's d = 0.16), consistent with interhemispheric inhibition, which was uncorrelated with analgesia ( P > 0.10). This study provides strong evidence for reliable and polarity-dependent modulation of experimental pain by M1-tDCS.

OBJECTIVE:This study evaluates the potential of complex 3D Electrical Impedance Tomography (EIT) for intraoperative surgical margin assessment (SMA) using an ex vivo bovine model. METHODS:A custom electrode array was used to collect impedance data across multiple frequencies (100 Hz-1 MHz) from 57 tissue samples. An optimal pressure range was identified to ensure proper electrode contact with minimal tissue deformation (2 kPa to 5 kPa) and a saline calibration was used to minimize model-data mismatch. A novel best fit factor, β, was introduced to scale the reference data of difference EIT and initial guess for absolute EIT to eliminate inversions in permittivity. The accuracy of complex EIT reconstructions were investigated using pixel-based tissue classification. RESULTS:Experimental difference EIT, particularly for conductivity (σ) at 100 Hz, achieved high sensitivity (0.92) and specificity (0.90) with fast reconstruction speeds of 1.67 seconds. While absolute EIT performed slightly better in quantitative metrics for σ imaging (AUC = 0.90, Accuracy = 0.86), difference EIT was found to be more suitable for real-time applications due to its faster processing time. Simulations suggested that permittivity (ϵ) has sufficient contrast for classifying muscle and adipose tissue. However, experimental ϵ reconstructions exhibited lower performance, suggesting the need for hardware improvements. CONCLUSION:Difference EIT is the most promising method for real-time applications, balancing high accuracy with reconstruction speeds. Absolute EIT, while slightly more accurate, is less feasible due to longer processing times (150.6 seconds). SIGNIFICANCE:This study advances the potential for real-time intraoperative SMA using a novel complex EIT reconstruction method.

Objective.Occult hemorrhage (OH) can emerge subtly post-trauma, especially when internal bleeding is not yet severe enough to result in noticeable hemodynamic changes or shock. Despite normal appearances of traditional vital signs like heart rate (HR) and blood pressure (BP), clinically significant OH may be present, posing a critical diagnostic challenge. Early detection of OH, before vital signs begin to deteriorate, is vital as delays in identifying such conditions are linked to poorer patient outcomes. We analyze the performance of poly-anatomic multivariate technologies-including electrical impedance tomography (EIT), near-infrared spectroscopy (NIRS), electrical impedance spectroscopy (EIS), plethysmography (Pleth), and ECG-in a porcine model of OH. The goal was to detect OH without the need to know the subject's pre-established normal baseline.Approach.Forty female swine were bled at slow rates to create an extended period of subclinical hemorrhage, during which the animals' HR and BP remained stable before hemodynamic deterioration. Continuous vital signs, Pleth, and continuous non-invasive data were recorded and analyzed with the objective of developing an improved means of detecting OH. This detection was set up as a supervised voting classification problem where the measurement of each technology (minimally transformed) was used to train a classifier. A soft majority voting classification technique was then used to detect the existence of OH.Main Results.When comparing the prediction performance of the most significant univariate technology (EIT) to that of a poly-anatomic multivariate approach, the latter achieved higher area-under-the-curve (AUC) values from receiver operating characteristic analyses in almost every observation interval duration. In particular, after 21 min of continuous observation, the best AUC of the multivariate approach was 0.98, while that of the univariate approach was 0.92. The best multivariate technologies, in descending order, appeared to be EIT on the thorax, NIRS on the abdomen, and EIS on the thorax.Significance.In this clinically relevant porcine model of clinically OH, multivariate non-invasive measurements may be superior to univariate ones in detecting OH. Advanced technologies such as EIT, NIRS, and EIS exhibit considerably greater potential to accurately predict OH than standard physiological measurements. From a practical standpoint, our approach would not require the medical device to have prior access to non-hemorrhage baseline data for each patient. Early detection of OH using these technologies could improve patient outcomes by allowing for timely intervention before vital signs begin to deteriorate.

e18100 Background: Oral squamous cell carcinoma (OSCC) is a prevalent, lethal cancer representing 4.6% of global cancer-related deaths. 60% of oral cancers are diagnosed at advanced stages with a 5-year survival rate of only 40%. Primary treatment for oral cancers often involves surgical resection. However, this approach can be limited by the presence of positive resection margins, which occur in nearly 13% of cases. Previous research has demonstrated the utility of electrical impedance spectroscopy (EIS) in detecting variations in the electrical properties of tissue and has applications in the setting of oral cancers. This study used an impedance sensing probe to evaluate differences in electrical impedance between healthy, dysplastic, and malignant oral tissue intraoperatively on ex-vivo sample tissue. Methods: 86 total patients undergoing OSCC resection (n=67) and biopsy (n=19) at Dartmouth-Hitchcock Medical Center were enrolled under an IRB-approved protocol. Many patients had multiple abnormal tissue sites resulting in 187 total samples. Electrical impedance was measured using a custom-designed 11mm diameter electrode array with a 3D-printed probe, capturing data from ex-vivo lesions and healthy tissue. Sample resistance, reactance, phase, and impedance magnitude were recorded at 31 logarithmically spaced frequencies between 0.1-100kHz and analyzed using MATLAB. Unpaired t-tests compared impedance parameters between tissue groups: healthy, cancer, dysplasia (low, moderate, high). Results were validated against pathologic assessments at each probe site. Reporting of interim data results approved by the study’s Data and Safety Monitoring Committee. Results: Reactance and resistance are significantly lower in malignant tissue compared to healthy tissue (p<0.0001) for most frequencies. AUCs for resistance and reactance were 0.85 at 500Hz and 0.87 at 6.3kHz, respectively. Resistance is significantly lower (p<0.005) in malignant tissue compared to healthy tissue for all frequencies except 12.6kHz. Resistance significantly differentiated between and healthy tissue for only two frequencies (p<0.005). Reactance is significantly lower (p<0.05) in malignant tissue compared to healthy tissue and dysplastic tissue for all frequencies except for 100kHz. Conclusions: This study demonstrates the feasibility and efficacy of EIS in differentiating oral cavity tissues based on their electrical characteristics. Analysis of resistance and reactance measurements yielded an AUC>0.85, indicating a strong ability to discriminate between healthy, dysplastic, and malignant tissues. These findings suggest that EIS may have potential as a non-invasive and objective diagnostic tool for intraoperative use. This data can be used for development of EIS technology for eventual outpatient utilization. Clinical trial information: NCT05430477 .

The contrast in the electrical properties of healthy and malignant lung tissue could provide a methodology for intraoperative surgical margin assessment to reduce positive margins and improve clinical outcomes. However, the tissue is often compressed and deformed during intraoperative procedures. This study explores the impact applied pressure has on the electrical properties of ex vivo human lung tissue. Impedance spectra spanning 100 Hz to 10 MHz were recorded from freshly resected lung tissue specimens including lesion (n=3), perilesion (n=3), and healthy (n=4) samples, under an applied load and converted into resistivity. A linear regression was performed for each resistivity-pressure curve for all tissue types. A significant difference (p<0.05) was found between regression coefficients of lesion and perilesion tissues and both regression coefficient and constant for lesion and healthy tissue. No significant differences were found between the perilesion and healthy tissue coefficient or constant. These finding suggests that resistivity increases with pressure at different rates for malignant and healthy tissue that may be sufficient for surgical margin assessment.

ABSTRACT:Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulatory technique with the potential to provide pain relief. However, tDCS effects on pain are variable across existing studies, possibly related to differences in stimulation protocols and expectancy effects. We investigated the independent and joint effects of contralateral motor cortex tDCS (anodal vs cathodal) and socially induced expectations (analgesia vs hyperalgesia) about tDCS on thermal pain. We employed a double-blind, randomized 2 × 2 factorial cross-over design, with 5 sessions per participant on separate days. After calibration in Session 1, Sessions 2 to 5 crossed anodal or cathodal tDCS (20 minutes 2 mA) with socially induced analgesic or hyperalgesic expectations, with 6 to 7 days between the sessions. The social manipulation involved videos of previous "participants" (confederates) describing tDCS as inducing a low-pain state ("analgesic expectancy") or hypersensitivity to sensation ("hyperalgesic expectancy"). Anodal tDCS reduced pain compared with cathodal stimulation (F(1,19.9) = 19.53, P < 0.001, Cohen d = 0.86) and analgesic expectancy reduced pain compared with hyperalgesic expectancy (F(1,19.8) = 5.62, P = 0.027, Cohen d = 0.56). There was no significant interaction between tDCS and social expectations. Effects of social suggestions were related to expectations, whereas tDCS effects were unrelated to expectancies. The observed additive effects provide novel evidence that tDCS and socially induced expectations operate through independent processes. They extend clinical tDCS studies by showing tDCS effects on controlled nociceptive pain independent of expectancy effects. In addition, they show that social suggestions about neurostimulation effects can elicit potent placebo effects.

This study aimed to determine an optimal model involving thoracic electrical impedance tomography (EIT) metrics and patient geometric information to best correlate to standard pulmonary function test (PFT) measures in a cohort of 32 ALS patients and 32 age-matched healthy controls. Thoracic EIT is a non-invasive technology in which an electrode belt chest allows for real-time impedance imaging of respiratory function. The optimal form of the model was determined via a genetic algorithm a novel technique for model generation in EIT applications. Combining multiple metrics yielded optimal r2 values of 0.62 and 0.66 for 1- and 2-term regression models optimized. The results appear very promising and further refinement of the technology appears warranted.

This study aimed to develop and validate a Computed Tomography (CT)/Magnetic Resonance Imaging (MRI)-compatible polymer oral retractor system to enable intraoperative image guidance for transoral robotic surgery (TORS). The retractor was designed based on standard-of-care metallic retractors and 3D (three-dimensional) printed with carbon fiber composite and nylon. The system was comprehensively evaluated in bench-top and cadaveric experiments in terms of its ability to enable intraoperative CT/MR images during TORS, functionality including surgical exposure and working volume, usability, compatibility with da Vinci surgical systems, feasibility for disinfection or sterilization, and robustness over an extended period of time. The polymer retractor system enabled the acquisition of high-resolution and artifact-free intraoperative CT/MR images during TORS. With an inter-incisive distance of 42.55 mm and a working volume of 200.09 cm3, it provided surgical exposure comparable to standard-of-care metallic retractors. The system proved intuitive and compatible with da Vinci S, Xi, and Single Port systems, enabling successful mock surgical tasks performed by surgeons and residents. The retractor components could be effectively disinfected or sterilized for clinical use without significant compromise in material strength, with STERRAD considered the optimal method. Throughout a 2 h mock procedure, the retractor system showed minimal displacements (<1.5 mm) due to surrounding tissue deformation, with insignificant device deformation. The 3D-printed polymer retractor system successfully enabled artifact-free intraoperative CT/MR imaging in TORS for the first time and demonstrated feasibility for clinical use. This breakthrough opens the door to surgical navigation with intraoperative image guidance in TORS, offering the potential to significantly improve surgical outcomes and patients’ quality of life.