Real-time in vivo assessment of radiofrequency ablation of human colorectal liver metastases using diffuse reflectance spectroscopy.

BACKGROUND: The success of radiofrequency (RF) ablation is limited by the inability to assess thermal tissue damage achieved during or immediately after the procedure. The goal of this proof-of-principle study was to investigate whether diffuse reflectance (DR) spectroscopy during and after RF ablation of liver tumours could aid in detecting complete tissue ablation. MATERIAL AND METHODS: DR spectra were acquired in vivo in eight patients undergoing RF ablation for unresectable colorectal liver metastases, using a disposable spectroscopy needle. Intraoperative ultrasound imaging was used for accurate positioning of the RF electrode and the spectroscopy needle. Spectral changes were quantified and correlated to tissue histopathology and follow-up CT imaging. RESULTS: For the lesions in which ablation was monitored by DR spectroscopy (N = 8), median tumour size was 1.6 cm (range 0.8-3.3 cm). We found an excellent correlation (97-99%) between thermal damage suggested by spectral changes and histology. DR spectroscopy allowed discrimination between non-ablated and ablated tissue, regardless whether the needle was placed in tumour tissue or in surrounding liver tissue. Additional measurements performed continuously during ablation confirmed that the magnitude of spectral change correlates with the histochemical degree of thermal damage. CONCLUSIONS: Diffuse reflectance spectroscopy allows accurate quantification of thermal tissue damage during and after RF ablation. Real-time feedback by DR spectroscopy could improve the accuracy and quality of the RF procedures by lowering incomplete ablation rates.

Differentiation of healthy and malignant tissue in colon cancer patients using optical spectroscopy: A tool for image-guided surgery.

BACKGROUND: Surgery for colorectal cancer aims for complete tumor resection. Optical-based techniques can identify tumor and surrounding tissue through the tissue specific optical properties, absorption and scattering, which are both influenced by the biochemical and morphological composition of the tissue. OBJECTIVE: To evaluate the feasibility of dual-modality Diffuse Reflectance Spectroscopy-Fluorescence Spectroscopy (DRS-FS) for discrimination between healthy and malignant tissue in colorectal surgery. METHODS: Surgical specimens from colorectal cancer patients were measured immediately after resection using a fiber-optic needle capable of dual-modality DRS-FS. Model-based analyses were used to derive scattering and absorption coefficients and intrinsic fluorescence. Volume fractions of chromophores were estimated. Furthermore, optical data were recorded along a trajectory from healthy tissue towards tumor. RESULTS: Spectral characteristics were identified in 1,273 measured spectra from 21 specimens. Combined DRS and FS discriminated tumor from surrounding tissue with a sensitivity of 95% and a specificity of 88%. Significant spectral changes were seen along the trajectory from healthy tissue to tumor. CONCLUSION: This study demonstrates that dual-modality DRS-FS can identify colorectal cancer from surrounding healthy tissue. The quantification of comprehensible parameters allows robust classification and facilitates extrapolation towards the clinical setting. The technique, here demonstrated in a needle like probe, can be incorporated into surgical tools for optically guided surgery in the near future. Lasers Surg. Med. 47:559-565, 2015. © 2015 Wiley Periodicals, Inc.

Near-infrared fluorescence (NIRF) imaging in breast-conserving surgery: assessing intraoperative techniques in tissue-simulating breast phantoms.

PURPOSE: Breast-conserving surgery (BCS) results in tumour-positive surgical margins in up to 40% of the patients. Therefore, new imaging techniques are needed that support the surgeon with real-time feedback on tumour location and margin status. In this study, the potential of near-infrared fluorescence (NIRF) imaging in BCS for pre- and intraoperative tumour localization, margin status assessment and detection of residual disease was assessed in tissue-simulating breast phantoms. METHODS: Breast-shaped phantoms were produced with optical properties that closely match those of normal breast tissue. Fluorescent tumour-like inclusions containing indocyanine green (ICG) were positioned at predefined locations in the phantoms to allow for simulation of (i) preoperative tumour localization, (ii) real-time NIRF-guided tumour resection, and (iii) intraoperative margin assessment. Optical imaging was performed using a custom-made clinical prototype NIRF intraoperative camera. RESULTS: Tumour-like inclusions in breast phantoms could be detected up to a depth of 21 mm using a NIRF intraoperative camera system. Real-time NIRF-guided resection of tumour-like inclusions proved feasible. Moreover, intraoperative NIRF imaging reliably detected residual disease in case of inadequate resection. CONCLUSION: We evaluated the potential of NIRF imaging applications for BCS. The clinical setting was simulated by exploiting tissue-like breast phantoms with fluorescent tumour-like agarose inclusions. From this evaluation, we conclude that intraoperative NIRF imaging is feasible and may improve BCS by providing the surgeon with imaging information on tumour location, margin status, and presence of residual disease in real-time. Clinical studies are needed to further validate these results.