Optical determination of fatty change of the graft liver with near-infrared time-resolved spectroscopy

In vivo assessment of diet-induced rat hepatic steatosis development by percutaneous single-fiber spectroscopy detects scattering spectral changes due to fatty infiltration

This study explores percutaneous single-fiber spectroscopy (SfS) of rat livers undergoing fatty infiltration. Eight test rats were fed a methionine-choline-deficient (MCD) diet, and four control rats were fed a normal diet. Two test rats and one control rat were euthanized on days 12, 28, 49, and 77 following initiation of the diet, after percutaneous SfS of the liver under transabdominal ultrasound guidance. Histology of each set of the two euthanized test rats showed mild and mild hepatic lipid accumulations on day 12, moderate and severe on day 28, severe and mild on day 49, and moderate and mild on day 77. Livers with moderate or higher lipid accumulation generally presented higher spectral reflectance intensity when compared to lean livers. Livers of the eight test rats on day 12, two of which had mild lipid accumulation, revealed an average scattering power of 0.37±0.14 in comparison to 0.07±0.14 for the four control rats (p<0.01 ). When livers of the test rats with various levels of fatty infiltration were combined, the average scattering power was 0.36±0.15 0.36±0.15 in comparison to 0.14±0.24 of the control rats (0.05<p<0.1). Increasing lipid accumulation in concentration and size seemed to cause an increase of the scattering power prior to increasing total spectral reflectance.

Diffuse reflectance spectroscopy accurately quantifies various degrees of liver steatosis in murine models of fatty liver disease

Background

A real-time objective evaluation for the extent of liver steatosis during liver transplantation is currently not available. Diffuse reflectance spectroscopy (DRS) rapidly and accurately assesses the extent of steatosis in human livers with mild steatosis. However, it is yet unknown whether DRS accurately quantifies moderate/severe steatosis and is able to distinguish between micro- and macrovesicular steatosis.

Methods

C57BL/6JolaHsd mice were fed wit a choline-deficient l-amino acid-defined diet (CD-AA) or a choline-sufficient l-amino acid-defined control diet (CS-AA) for 3, 8, and 20 weeks. In addition B6.V-Lepob/OlaHsd (ob/ob) mice and their lean controls were studied. A total of 104 DRS measurements were performed in liver tissue ex vivo. The degree of steatosis was quantified from the DRS data and compared with histopathological analysis.

Results

When assessed by histology, livers of mice fed with a CD-AA and CS-AA diet displayed macrovesicular steatosis (range 0–74 %), ob/ob mice revealed only microvesicular steatosis (range 75–80 %), and their lean controls showed no steatosis. The quantification of steatosis by DRS correlated well with pathology (correlation of 0.76 in CD-AA/CS-AA fed mice and a correlation of 0.75 in ob/ob mice). DRS spectra did not distinguish between micro- and macrovesicular steatosis. In samples from CD-AA/CS-AA fed mice, the DRS was able to distinguish between mild and moderate/severe steatosis with a sensitivity and specificity of 86 and 81 %, respectively.

Conclusion

DRS can quantify steatosis with good agreement to histopathological analysis. DRS may be useful for real-time objective evaluation of liver steatosis during liver transplantation, especially to differentiate between mild and moderate/severe steatosis.

Intrahepatic triglyceride measurement and estimation of viability in rat fatty livers by near-infrared spectroscopy

AIM

This study investigated the features of fatty livers using near-infrared (NIR) spectroscopy and validated the usefulness of NIR spectroscopy for the measurement of intrahepatic triglyceride (TG) contents and evaluation of viability in fatty livers.

METHODS

In vitro, we examined specific spectra for each purified TG fraction by NIR. In vivo, the differences between the spectra obtained from normal and fatty livers before warm ischemia and the differences between the spectra obtained from each rat liver before and after warm ischemia were subjected to multicomponent analysis.

RESULTS

In vitro experiments revealed a specific peak at 925 nm in major TG fractions, and NIR spectroscopy precisely detected changes in TG volume. In vivo experiments revealed that NIR spectroscopy detected TG content changes in rat fatty livers induced by a choline-deficient diet following the addition of purified TG spectrum for NIR spectroscopic analysis in least square curve fitting. The TG level in the fatty livers measured by NIR spectroscopy significantly correlated with the morphometric measurement of lipid content in the livers. NIR spectroscopy also revealed decreased levels of total hemoglobin (Hb) and oxidized Hb and maintenance of homeostasis in cytochrome redox states in fatty livers under normal condition. However, NIR spectroscopy showed irreversible deterioration of hepatic microcirculation, Hb oxygenation and homeostasis of the cytochrome redox states in fatty livers after 60-min warm ischemia reperfusion.

CONCLUSION

These studies demonstrated that NIR spectroscopy can quantitatively measure the intrahepatic TG content in addition to simultaneously evaluating microcirculation and Hb oxygenation.

Validation of interventional fiber optic spectroscopy with MR spectroscopy, MAS-NMR spectroscopy, high-performance thin-layer chromatography, and histopathology for accurate hepatic fat quantification

OBJECTIVES

To validate near-infrared (NIR)-based optical spectroscopy measurements of hepatic fat content using a minimally invasive needle-like probe with integrated optical fibers, enabling real-time feedback during percutaneous interventions. The results were compared with magnetic resonance spectroscopy (MRS) as validation and with histopathology, being the clinical gold standard. Additionally, ex vivo magic angle spinning nuclear magnetic resonance spectroscopy and high-performance thin-layer chromatography were performed for comparison.

MATERIALS AND METHODS

Ten mice were used for the study, of which half received a regular chow diet and the other half received a high-fat diet to induce obesity and hepatosteatosis. The mice were imaged with a clinical 3-Tesla MR to select a region of interest within the right and left lobes of the liver, where MRS measurements were acquired in vivo. Subsequently, optical spectra were measured ex vivo at the surface of the liver at 6 different positions immediately after resection. Additionally, hepatic fat was determined by magic angle spinning nuclear magnetic resonance spectroscopy and high-performance thin-layer chromatography. Histopathologic analyses were performed and used as the reference standard. Pearson correlation and linear regression analyses were performed to assess the correlation of the various techniques with NIR. A 1-way analysis of variance including post hoc Tukey multiple comparison tests was used to study the difference in fat estimation between the various techniques.

RESULTS

For both the mice groups, the estimated fat fractions by the various techniques were significantly similar (P = 0.072 and 0.627 for chow diet and high-fat diet group, respectively). The Pearson correlation value between NIR and the other techniques for fat determination showed the same strong linear correlation (P above 0.990; P < 0.001), whereas for histopathologic analyses, which is a rather qualitative measure, the Pearson correlation value was slightly lower (P = 0.925, P < 0.001) . Linear regression coefficient computed to compare NIR with the other techniques resulted in values close to unity with MRS having the narrowest confidence interval (r = 0.935, 95% confidence interval: 0.860-1.009), demonstrating highly correlating results between NIR and MRS.

CONCLUSIONS

NIR spectroscopy measurements from a needle-like probe with integrated optical fibers for sensing at the tip of the needle can quickly and accurately determine hepatic fat content during an interventional procedure and might therefore be a promising novel diagnosing tool in the clinic.

Transcutaneous detection and direct approach to the sentinel node using axillary compression technique in ICG fluorescence-navigated sentinel node biopsy for breast cancer

BACKGROUND

Indocyanine green (ICG) fluorescence navigation is a useful option in sentinel node biopsy (SNB) for breast cancer. However, several technical difficulties still exist. Since the sentinel node (SN) cannot be recognized over the skin, subcutaneous lymphatic vessels (LVs) must be carefully dissected without injury. In addition, the dissecting procedures are often interrupted by turning off the operating light during fluorescence observation. In this report, we introduce a new approach using the axillary compression technique to overcome these problems.

MATERIALS AND METHODS

In the original procedure of the ICG fluorescence method, the subcutaneous lymphatic drainage pathway from the breast to the axilla was observed in fluorescence images, but no signal could be obtained in the axilla. When the axillary skin was compressed against the chest wall using a plastic device, the signals from the deeper lymphatic structures could be observed. By tracing the compression-inducible fluorescence signal towards the axilla, transcutaneous detection and direct approach to the SN were achieved. The benefit of this approach is that there is no risk of injury of LVs, and the procedures are interrupted less frequently by fluorescence observation. The axillary compression technique was used in 50 patients with early breast cancer.

RESULTS

SNs were successfully removed in all patients. Transcutaneous detection and direct approach were possible in 47 patients. This approach was also effective in obese patients.

CONCLUSIONS

Axillary compression technique is a simple way to facilitate the surgical procedures of ICG fluorescence-navigated SNB for breast cancer.

Electrical and optical spectroscopy for quantitative screening of hepatic steatosis in donor livers

Macro-steatosis in deceased donor livers is increasingly prevalent and is associated with poor or non-function of the liver upon reperfusion. Current assessment of the extent of steatosis depends upon the macroscopic assessment of the liver by the surgeon and histological examination, if available. In this paper we demonstrate electrical and optical spectroscopy techniques which quantitatively characterize fatty infiltration in liver tissue. Optical spectroscopy showed a correlation coefficient of 0.85 in humans when referenced to clinical hematoxylin and eosin (H&E) sections in 20 human samples. With further development, an optical probe may provide a comprehensive measure of steatosis across the liver at the time of procurement.

The smart Petri dish: a nanostructured photonic crystal for real-time monitoring of living cells

The intensity of light scattered from a porous Si photonic crystal is used to monitor physiological changes in primary rat hepatocytes. The cells are seeded on the surface of a porous Si photonic crystal that has been filled with polystyrene and treated with an O2 plasma. Light resonant with the photonic crystal is scattered by the cell layer and detected as an optical peak with a charge-coupled-device spectrometer. It is demonstrated that exposure of hepatocytes to the toxins cadmium chloride or acetaminophen leads to morphology changes that cause a measurable increase in scattered intensity. The increase in signal occurs before traditional assays are able to detect a decrease in viability, demonstrating the potential of the technique as a complementary tool for cell viability studies. The scattering method presented here is noninvasive and can be performed in real time, representing a significant advantage compared to other techniques for in vitro monitoring of cell morphology.

Broadband reflectance measurements of light penetration, blood oxygenation, hemoglobin concentration, and drug concentration in human intraperitoneal tissues before and after photodynamic therapy

We evaluate Photofrin-mediated photodynamic therapy (PDT) in a phase 2 clinical trial as an adjuvant to surgery to treat peritoneal carcinomatosis. We extract tissue optical [reduced scattering (mu(s)'), absorption (mu(a)), and attenuation coefficients (mu(eff))] and physiological [blood oxygen saturation (%S(t)O2), total hemoglobin concentration (THC), and photosensitizer concentration (c(Photofrin))] properties in 12 patients using a diffuse reflectance instrument and algorithms based on the diffusion equation. Before PDT, in normal intraperitoneal tissues %S(t)O2 and THC ranged between 32 to 100% and 19 to 263 microM, respectively; corresponding data from tumor tissues ranged between 11 to 44% and 61 to 224 microM. Tumor %S(t)O2 is significantly lower than oxygenation of normal intraperitoneal tissues in the same patients. The mean (+/-standard error of mean) penetration depth (delta) in millimeters at 630 nm is 4.8(+/-0.6) for small bowel, 5.2 (+/-0.67) for large bowel, 3.39(+/-0.29) for peritoneum, 5.19(+/-1.4) for skin, 1.0(+/-0.1) for liver, and 3.02(+/-0.66) for tumor. c(Photofrin) in micromolars is 4.9(+/-2.3) for small bowel, 4.8(+/-2.3) for large bowel, 3.0 (+/-1.0) for peritoneum, 2.5(+/-0.9) for skin, and 7.4(+/-2.8) for tumor. In all tissues examined, mean c(Photofrin) tends to decrease after PDT, perhaps due to photobleaching. These results provide benchmark in-vivo tissue optical property data, and demonstrate the feasibility of in-situ measurements during clinical PDT treatments.

Optical analysis of cirrhotic liver by near infrared time-resolved spectroscopy

The severity of liver cirrhosis was related with the optical properties of liver tissue. Various grades of liver cirrhosis were produced in rats by intraperitoneal injection of thioacetamide (TAA) for different periods: 4 weeks, 8 weeks, 12 weeks, and 16 weeks. Optical properties of the liver, absorption coefficient (μa) and scattering coefficient (μs'), were measured by near-infrared time-resolved spectroscopy. Histological examination confirmed cirrhotic changes in the liver, which were more severe in rats with TAA administration for longer periods. The μa increased in 4- and 8-week rats, and then decreased in 12- and 16-week rats. The μa of blood-free liver decreased as liver cirrhosis progressed. The hemoglobin content in the liver calculated from the μa values increased in 4- and 8-week rats and decreased in 12- and 16-week rats. The μs' decreased in the cirrhotic liver, probably reflecting the decrease in the mitochondria content. It was shown that μa and μs' determination is useful to assess the severity of liver cirrhosis. © 1999 Society of Photo-Optical Instrumentation Engineers.

Application of near-infrared time-resolved spectroscopy to rat liver--a preliminary report for surgical application

The applicability of near-infrared time-resolved spectroscopy to rat liver surgery was investigated. First, the technical reliability in determining the absorption coefficient (mu(a)) and reduced scattering coefficient (mu'(s)) of the liver was checked. Next, boundary effects in determining mu(a) and mu'(s) of the rat liver were examined. Finally, changes in mu(a) and mu'(s) of rat liver with ischaemia were directly measured by TRS. Our TRS system showed that the mu(a) value held a linear correlation with the ink concentration in a lipid emulsion until mu(a) reached 1.2 cm(-1), while the mu'(s) was fairly independent. The mu(a) values of blood-free rat liver and blood-containing rat liver at 780 nm were observed to be 0.43 cm(-1) and 0.67 cm(-1) by using the matching method, indicating that TRS is reliable in determining mu(a) and mu'(s) of the liver. Possible errors in mu(a) and mu'(s) determination due to the boundary effects of the rat liver were as small as 7%, when the mu(a) value was as high as observed for the liver. The oxygen saturation of haemoglobin (SO2) was changed from 64.9% to 8.0%, and the haemoglobin content (THB) from 189.1 microM to 131.6 microM by ischaemia. Mu'(s) dynamically changed in the range 7.06 cm(-1) to 11.36 cm(-1). We conclude that time-resolved measurement is applicable in the high-mu(a) region observed in the liver, and can give quantitative estimations of SO2 and THB in the liver.

Compact tissue oximeter based on dual-wavelength multichannel time-resolved reflectance

We developed a compact dual-wavelength multichannel tissue oximeter based on the time-correlated single-photon counting (TCSPC) technique. The light sources are two pulsed diode lasers (output wavelengths of 672 and 818 nm, an average power of 1 mW, a pulse duration of 100 ps, and a pulse-repetition rate as high as 80 MHz). The time-resolved reflectance photons are detected by a multianode photomultiplier, and the output signals are redirected by a router to different memory blocks of the TCSPC personal computer board. The system's accuracy in determining the absorption microa and the reduced-scattering micros' coefficients and in reconstructing absorber concentrations in diffusive media was tested on phantoms. Preliminary in vivo tissue-oxygenation measurements were performed on healthy volunteers under different physiological conditions with a minimum acquisition time of 100 ms and an injected power of less than 100 microW.