Tissue diagnosis during colorectal cancer surgery using optical sensing: an in vivo study.

BACKGROUND: In colorectal cancer surgery there is a delicate balance between complete removal of the tumor and sparing as much healthy tissue as possible. Especially in rectal cancer, intraoperative tissue recognition could be of great benefit in preventing positive resection margins and sparing as much healthy tissue as possible. To better guide the surgeon, we evaluated the accuracy of diffuse reflectance spectroscopy (DRS) for tissue characterization during colorectal cancer surgery and determined the added value of DRS when compared to clinical judgement. METHODS: DRS spectra were obtained from fat, healthy colorectal wall and tumor tissue during colorectal cancer surgery and results were compared to histopathology examination of the measurement locations. All spectra were first normalized at 800 nm, thereafter two support vector machines (SVM) were trained using a tenfold cross-validation. With the first SVM fat was separated from healthy colorectal wall and tumor tissue, the second SVM distinguished healthy colorectal wall from tumor tissue. RESULTS: Patients were included based on preoperative imaging, indicating advanced local stage colorectal cancer. Based on the measurement results of 32 patients, the classification resulted in a mean accuracy for fat, healthy colorectal wall and tumor of 0.92, 0.89 and 0.95 respectively. If the classification threshold was adjusted such that no false negatives were allowed, the percentage of false positive measurement locations by DRS was 25% compared to 69% by clinical judgement. CONCLUSION: This study shows the potential of DRS for the use of tissue classification during colorectal cancer surgery. Especially the low false positive rate obtained for a false negative rate of zero shows the added value for the surgeons. Trail registration This trail was performed under approval from the internal review board committee (Dutch Trail Register NTR5315), registered on 04/13/2015, https://www.trialregister.nl/trial/5175 .

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.

Fat/water ratios measured with diffuse reflectance spectroscopy to detect breast tumor boundaries.

Recognition of the tumor during breast-conserving surgery (BCS) can be very difficult and currently a robust method of margin assessment for the surgical setting is not available. As a result, tumor-positive margins, which require additional treatment, are not found until histopathologic evaluation. With diffuse reflectance spectroscopy (DRS), tissue can be characterized during surgery based on optical parameters that are related to the tissue morphology and composition. Here we investigate which optical parameters are able to detect tumor in an area with a mixture of benign and tumor tissue and hence which parameters are most suitable for intra-operative margin assessment. DRS spectra (400-1600 nm) were obtained from 16 ex vivo lumpectomy specimens from benign, tumor border, and tumor tissue. One mastectomy specimen was used with a custom-made grid for validation purposes. The optical parameter related to the absorption of fat and water (F/W-ratio) in the extended near-infrared wavelength region (~1000-1600 nm) provided the best discrimination between benign and tumor sites resulting in a sensitivity and specificity of 100 % (excluding the border sites). Per patient, the scaled F/W-ratio gradually decreased from grossly benign tissue towards the tumor in 87.5 % of the specimens. In one test case, based on a predefined F/W-ratio for boundary tissue of 0.58, DRS produced a surgical resection plane that nearly overlapped with a 2-mm rim of benign tissue, 2 mm being the most widely accepted definition of a negative margin. The F/W-ratio provided excellent discrimination between sites clearly inside or outside the tumor and was able to detect the border of the tumor in one test case. This work shows the potential for DRS to guide the surgeon during BCS.

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.

Optical sensing for tumor detection in the liver.

BACKGROUND: There is an increasing trend for optical guidance techniques in surgery. Optical imaging using Diffuse Reflectance Spectroscopy (DRS) can distinguish different tissue types through a specific "optical fingerprint". We investigated whether DRS could discriminate metastatic tumor tissue from normal liver tissue and thus if this technique would have potential for further implementation into surgical instruments or radiological intervention tools. METHODS: A miniaturized optical needle was developed able to collect DRS spectra between 500 and 1600 nm. Liver specimen of 24 patients operated for colorectal liver metastases were analyzed with DRS immediately after resection. Multiple measurements were performed and DRS results were compared to the histology analysis of the measurement locations. In addition, normal liver tissue was scored for the presence or absence of steatosis. RESULTS: A total of 780 out of the 828 optical measurements were correctly classified into either normal or tumor tissue. The resulting sensitivity and specificity were both 94%. The results of the analysis for each patient individually showed an accuracy of 100%. The Spearman's rank correlation of DRS-estimated percentages of hepatic steatosis in liver tissue compared to that of the pathologist was 0.86. CONCLUSIONS: DRS demonstrates a high accuracy in discriminating normal liver tissue from colorectal liver metastases. DRS can also predict the degree of hepatic steatosis with high accuracy. The technique, here demonstrated in a needle like probe, may as such be incorporated into surgical tools for optical guided surgery or percutaneous needles for radiological interventions.

Application of nonperiodic phase structures in optical systems.

Wide, nonperiodic stepped phase structures are studied to correct various parameter-dependent wave-front aberrations in optical systems. The wide nature of these phase structures makes them easy to manufacture with sufficient compensation of the wave-front aberrations. Wave-front aberration correction for both continuous and discrete parameter variations are studied. An analytical method is derived for the discrete parameter variations to find the optimal phase structure. Both theoretical and experimental results show that these nonperiodic phase structures can be used to make (1) lenses athermal (defocus and spherical aberration compensated), (2) lenses achromatic, (3) lenses with a large field of view, (4) lenses with a reduced field curvature, and (5) digital versatile disk objective lenses for optical recording that are compatible with compact disk readout.

Optical tolerances of an actively tilted high-numerical-aperture two-lens objective for optical recording.

Analytical expressions for the primary wave-front aberrations of an actively tilted two-lens objective are derived, and expressions for the higher-order wave-front aberrations for disk tilt of this lens system are presented. This analysis is important because the two-lens objective opens the way to achieving higher-numerical-aperture systems for optical recording with acceptable tolerances that cannot be achieved with a single-lens objective. To test whether the conclusions drawn from the analytically derived results remain valid for high numerical apertures, we compare the results with those obtained by ray tracing: It is shown not only that the two-lens system is tolerant of disk-thickness variations and decentering of the lenses but that it can also be made tolerant of disk tilt when the lens facing the disk is actively tilted.