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Histological analysis is meaningful in diagnosis only if the targeted tissue is obtained in the biopsy. Often, physicians have to take a tissue sample without accurate information about the location of the instrument tip. A novel biopsy needle with bioimpedance-based tissue identification has been developed to provide data for the automatic classification of the tissue type at the tip of the needle. The aim of this study was to examine the resolution of this identification method and to assess how tissue heterogeneities affect the measurement and tissue classification. Finite element method simulations of bioimpedance measurements were performed using a 3D model. In vivo data of a porcine model were gathered with a moving needle from fat, muscle, blood, liver, and spleen, and a tissue classifier was created and tested based on the gathered data. Simulations showed that very small targets were detectable, and targets of 2 9 2 9 2 mm 3 and larger were correctly measurable. Based on the in vivo data, the performance of the tissue classifier was high. The total accuracy of classifying different tissues was approximately 94%. Our results indicate that local bioimpedance-based tissue classification is feasible in vivo, and thus the method provides high potential to improve clinical biopsy procedures.

Lumbar puncture is a relatively safe procedure, but some serious, even fatal, complications can occur. Needle guidance can increase puncture accuracy, decrease the number of attempts, and make the procedure easier. We tested the feasibility of a bioimpedance-based tissue-sensing technology for needle guidance in clinical use. The Bioimpedance Probe (BIP) Needle has a removable BIP stylet enabling measurement of bioimpedance spectra during the procedure. The BIP Needle is connected to a measurement device that uses tissue-classification software, and the device provides audiovisual feedback when it detects cerebrospinal fluid (CSF). We performed spinal anesthesia with the BIP Needle in 45 patients. The device performance and needle tip location were verified by an experienced anesthesiologist confirming CSF leakage. The device detected CSF in all cases (sensitivity of 100 %). Six cases with false detections lowered the specificity to 81 %, but in practice, most of these were easy to differentiate from true detections because their duration was short and they occurred during backward movement of the needle. The epidural spectrum differentiated as fatty tissue from surrounding tissues, but the ligamentum flavum was not clearly detectable in the data. The BIP Needle is a reliable tool for detecting CSF in lumbar puncture. It can make the puncture procedure smoother, as repeated CSF flow tests are avoided. The correct needle tip location is immediately detected, thus unnecessary needle movements close to spinal nerves are prevented. Physicians could benefit from the information provided by the BIP Needle, especially in patients with obesity or anatomic alterations.

Lumbar puncture is an established clinical procedure to get a diagnostic sample of cerebrospinal fluid (CSF) or to inject anaesthetics or intrathecal therapy into the subarachnoid space (Bonadio et al, 2014;Schulga et al., 2015; Srinisavan et al., 2012). Laboratory analyses of CSF can reveal many severe diseases of the central nervous system, including infections and inflammatory, haemorrhagic or neoplastic diseases.Lumbar puncture is occasionally challenging to perform. Advancing a thin, flexible needle into the spinal canal through narrow spaces between lumbar bony structures without seeing the location of the needle tip or its direction while interpreting the tactile feedback from

Intra-articular glucocorticoid injections are the recommended treatment for active arthritis, but accurate positioning of the needle may be challenging. Inexperienced physicians might decide not to inject because an unsuccessful injection impairs clinical outcome and may lead to complications; however, choosing not to inject may impair or delay the best possible treatment. Here, we address this problem by introducing a novel Bioimpedance Probe (BIP) Needle-guidance method that was tested in a clinical study. The BIP Needle was utilized for detection of synovial fluid. It measures real-time bioimpedance spectra and identifies when the needle tip is in contact with the synovial fluid. Injections into 80 joints with active arthritis were performed by an experienced rheumatologist using the BIP Needle. The location of the BIP Needle was ensured by aspiration of synovial fluid, absence of resistance during injection, and/or using real-time ultrasound imaging. Sensitivity and specificity of the device for synovial fluid detection were 86 % (CI 75-93 %) and 85 % (CI 74-92 %), respectively. The BIP Needles showed high spatial resolution and differentiated the synovial fluid from the surrounding tissues. However, lack of synovial fluid, anatomic variability, and intra-articular structures challenged the technology. The BIP Needles provided adequate results in intra-articular injections. Performance of the device was good even in small joints, which may be the most difficult for inexperienced physicians. Further performance improvement can be expected when more data is collected for mathematical models. Overall, this novel method showed potential to be used in real-time needle guidance.

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 gather in vivo bioimpedance data from human liver and tumor tissues. Approach: We measured human liver and tumor impedance data in vivo from 26 patients who underwent diagnostic ultrasound-guided liver biopsy. Our novel 18G 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 human in vivo liver 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 tissue in vivo and this association is frequency-dependent.

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