Assessing the conditions for in vivo electrical virtual biopsies in Barrett's oesophagus

Virtual Biopsy by Electrical Impedance Spectroscopy in Barrett's Carcinoma

Purpose

Early detection of adenocarcinomas in the esophagus is crucial for achieving curative endoscopic therapy. Targeted biopsies of suspicious lesions, as well as four-quadrant biopsies, represent the current diagnostic standard. However, this procedure is time-consuming, cost-intensive, and examiner-dependent. The aim of this study was to test whether impedance spectroscopy is capable of distinguishing between healthy, premalignant, and malignant lesions. An ex vivo measurement method was developed to examine esophageal lesions using impedance spectroscopy immediately after endoscopic resection.

Methods

After endoscopic resection of suspicious lesions in the esophagus, impedance measurements were performed on resected cork-covered tissue using a measuring head that was developed, with eight gold electrodes, over 10 different measurement settings and with frequencies from 100 Hz to 1 MHz.

Results

A total of 105 measurements were performed in 60 patients. A dataset of 400 per investigation and a total of more than 42,000 impedance measurements were therefore collected. Electrical impedance spectroscopy (EIS) was able to detect dysplastic esophageal mucosa with a sensitivity of 81% in Barrett’s esophagus.

Conclusion

In summary, EIS was able to distinguish different tissue characteristics in the different esophageal tissues. EIS thus holds potential for further development of targeted biopsies during surveillance endoscopy.

Trial Registration

NCT04046601

Diagnosing early Barrett's neoplasia and oesophageal squamous cell neoplasia by bioimpedance spectroscopy in human tissue

BACKGROUND

Detection of early oesophageal cancer in surrounding normal tissue can be challenging, but detection is essential to determine the subsequent treatment. Dysplastic tissue can be detected by using electrical impedance spectroscopy (EIS).

OBJECTIVE

The aim of the present study was to evaluate the feasibility and value of EIS in the diagnosis of oesophageal neoplasia.

METHODS

This prospective ex-vivo study included 23 patients with early oesophageal cancer (17 with Barrett's cancer and six with early squamous cell cancer). Immediately after endoscopic resection, the electrical properties of the resected specimens were investigated using a pencil probe (5 mm in diameter, frequency range from 100 Hz to 1 MHz). Punch biopsies were taken from the measured site in order to compare the results of EIS with histology.

RESULTS

EIS was able to detect dysplastic oesophageal mucosa with a high rate of accuracy (82% in Barrett's oesophagus and 100% in squamous oesophagus) A total of 54 different sites in 26 tumours were evaluated.

CONCLUSIONS

EIS was able to differentiate reliably between non-neoplastic and neoplastic oesophageal mucosa. Using EIS, it might be possible to use it for targeted biopsies and to avoid unnecessary biopsies during cancer surveillance in future.

Bioimpedance spectroscopy: a new tool to assess early esophageal changes linked to gastroesophageal reflux disease?

Bioimpedance spectroscopy can identify pathological changes related to precancerous lesions of the cervix uteri and esophagus. It therefore has the potential to detect early reflux-related changes in the esophageal mucosa, such as dilated intercellular spaces. The reliable detection of dilated intercellular spaces at the time of endoscopy would yield a significant diagnostic advantage for separating patients with functional heartburn from the large proportion of patients with gastroesophageal reflux symptoms but no macroscopic esophagitis or pathological acid exposure. The bioimpedance of the esophageal mucosa, measured with a small caliber probe, was evaluated in a series of preclinical experiments. First, sections of rabbit esophageal epithelium were mounted in Ussing chambers and exposed to solutions at pH 7.4 or pH 1.5 for 45 minutes. Impedance measurements were taken at varying probe pressures. Second, rabbit esophageal epithelia were perfused for 45 minutes in situ with pH 1.1 or control solutions and impedance measurements taken. Samples from both in vitro and in situ experiments were taken for morphological examination by light microscopy. Finally, esophageal bioimpedance was measured in awake dogs with permanent esophagocutaneous stoma. The in situ experiments demonstrated that morphological changes in the esophageal mucosa could be discerned by the use of bioimpedance spectroscopy. The variability in resistivity was species-independent but was affected by the pressure applied to the probe. The results suggest that evaluation of bioimpedance spectroscopy for use in a clinical setting is warranted. Small morphological differences in the esophageal mucosa may be detected by the use of bioimpedance spectroscopy.

Electrical impedance spectroscopy and diagnosis of tendinitis

There have been a number of studies that investigate the usefulness of bioelectric signals in diagnoses and treatment in the medical field. Tendinitis is a musculoskeletal disorder with a very high rate of occurrence. This study attempts to examine whether electrical impedance spectroscopy (EIS) can detect pathological changes in a tendon and find the exact location of the lesion. Experimental tendinitis was induced by injecting collagenase into one side of the patellar tendons in rabbits, while the other side was used as the control. After measuring the impedance in the tendinitis and intact tendon tissue, the dissipation factor was computed. The real component of impedance and the dissipation factor turned out to be lower in tendinitis than in intact tissues. Moreover, the tendinitis dissipation factor spectrum showed a clear difference from that of the intact tendon, indicating its usefulness as a tool for detecting the location of the lesion. Pathologic findings from the tissues that were obtained after measuring the impedance confirmed the presence of characteristics of tendinitis. In conclusion, EIS is a useful method for diagnosing tendinitis and detecting the lesion location in invasive treatment.

Elastic scattering spectroscopy for detection of cancer risk in Barrett's esophagus: experimental and clinical validation of error removal by orthogonal subtraction for increasing accuracy

Elastic scattering spectroscopy (ESS) may be used to detect high-grade dysplasia (HGD) or cancer in Barrett's esophagus (BE). When spectra are measured in vivo by a hand-held optical probe, variability among replicated spectra from the same site can hinder the development of a diagnostic model for cancer risk. An experiment was carried out on excised tissue to investigate how two potential sources of this variability, pressure and angle, influence spectral variability, and the results were compared with the variations observed in spectra collected in vivo from patients with Barrett's esophagus. A statistical method called error removal by orthogonal subtraction (EROS) was applied to model and remove this measurement variability, which accounted for 96.6% of the variation in the spectra, from the in vivo data. Its removal allowed the construction of a diagnostic model with specificity improved from 67% to 82% (with sensitivity fixed at 90%). The improvement was maintained in predictions on an independent in vivo data set. EROS works well as an effective pretreatment for Barrett's in vivo data by identifying measurement variability and ameliorating its effect. The procedure reduces the complexity and increases the accuracy and interpretability of the model for classification and detection of cancer risk in Barrett's esophagus.

Electrical bioimpedance readings increase with higher pressure applied to the measuring probe

Electrical bioimpedance spectroscopy (EBIS) is a technique that uses a probe to calculate the transfer impedance from tissues. This transfer impedance can give information about the normal or pathological condition of the tissue. To take readings, pressure has to be applied to the probe in order to get a good contact between the electrodes and the tissue. We have been using EBIS to investigate the early diagnosis of dysplasia and cancer in the human cervix, oesophagus and bladder. We have found that, with increasing pressure (range used here was approximately 1 kPa to approximately 50 kPa), the resistivity readings increase in a consistent way up to 80%. In this paper, we show how this is a case in three different tissue types (oesophageal, gastric and vesical samples). These increases can be higher than those associated with the pathological changes that we are investigating (non-inflamed columnar tissue, for instance, shows values 50% higher than dysplastic columnar tissue). Finite-element modelling was also used to investigate the effect of volume reduction in the connective tissue or stroma. This simulation suggests no strong correlation between reduction of this structure and increase in resistivity. We hypothesize therefore that these changes may be mainly associated with the squeezing of water from the extracellular space. Finally, as pressure is difficult to control by hand, we raise the issue of the necessity of considering this variable when making EIS measurements.

Low frequency electrical bioimpedance for the detection of inflammation and dysplasia in Barrett's oesophagus

Biological tissues undergoing inflammation and dysplasia seem to exhibit changes in the intercellular space that can be sensed using low frequency electrical impedance methods. Basically, low frequency electric current flows through this space and its widening as well as the disruption of the tight junction decrease the resistance, facilitating current flow. The electrical changes accompanying structural changes from columnar tissue to adenocarcinoma in Barrett's metaplastic mucosa and gastric tissue are illustrated using resected tissue from 32 patients. Two hundred and fifty-eight biopsies were analysed, correlating their electrical resistivity (R) at 9.6 kHz and their histopathological interpretation. Compared to non-inflamed non-dysplastic columnar tissue (R = 4.9 ohms m), the results suggest a small but statistically significant decrease of electrical impedance in columnar tissue showing inflammation (R = 4.2 ohms m, p = 0.016) and a larger decrease when dysplasia is present (R = 3.4 ohms m, p = 0.040). If this method is validated further, this technique could be used to obtain guided biopsies from patients undergoing surveillance programmes for Barrett's oesophagus. We aim to refine this technique using a new system with lower frequencies and, possibly, in vitro (cultured cells) and in vivo (rats) models of Barrett's oesophagus.

Resistivity changes in conductive silicone sheets under stretching

This paper reports a preliminary finding associated with an investigation of how tissues respond to mechanical stress. The stress distribution within the tissue may be the result of normal function, for example, joint forces, or it may result from interventions such as tissue suturing during or after surgery. We sought to combine electrical and mechanical computational models in order to better understand the interaction between the two. For example, if mechanical stress is applied to tissue this may change the cell arrangements within the tissue matrix and hence change the electrical properties. If this interaction could be determined, then it should be possible to use electrical impedance tomography measurements to identify stress patterns in tissues. Measurements of resistivity changes have been made in conductive silicone rubber sheets when subject to a uniaxial stress of up to 10%. Relatively large changes in resistivity are produced (up to 200%). These changes are far larger than those predicted arising from topological changes alone. It is suggested that under stress the conductive islands of carbon within the silicone rubber sheet undergo a reversible disassociation from their neighbours and that the material's electrical properties change under load. If similar stress-resistivity relationships occur within biological materials it may be possible to recover the stress fields within tissues from transfer impedance measurements and thereby predict if actions such as inappropriate suture tension will compromise tissue viability.