Autofluorescence lifetime augmented reality as a means for real-time robotic surgery guidance in human patients.

Due to loss of tactile feedback the assessment of tumor margins during robotic surgery is based only on visual inspection, which is neither significantly sensitive nor specific. Here we demonstrate time-resolved fluorescence spectroscopy (TRFS) as a novel technique to complement the visual inspection of oral cancers during transoral robotic surgery (TORS) in real-time and without the need for exogenous contrast agents. TRFS enables identification of cancerous tissue by its distinct autofluorescence signature that is associated with the alteration of tissue structure and biochemical profile. A prototype TRFS instrument was integrated synergistically with the da Vinci Surgical robot and the combined system was validated in swine and human patients. Label-free and real-time assessment and visualization of tissue biochemical features during robotic surgery procedure, as demonstrated here, not only has the potential to improve the intraoperative decision making during TORS but also other robotic procedures without modification of conventional clinical protocols.

Effect of endogenous estradiol levels on bone resorption and bone mineral density in healthy postmenopausal women: a prospective study.

OBJECTIVE: To investigate the effect of endogenous estrogens on bone mineral density (BMD) and bone markers in postmenopausal women over 24 months. METHODS: Fifty out of 99 postmenopausal women seen previously were re-assessed after 24 months. Levels of BMD, bone markers, serum estradiol (E(2)) and total testosterone were determined. RESULTS: BMD decreased in the femoral neck ( approximately 2%) (p < 0.008), but remained stable in the other skeletal areas; E(2) and serum Crosslaps (sCTX) decreased by 34% (p < 0.001) and 21% (p < 0.003), respectively. Women aged < or = 65 years exhibited decreased BMD only in the femoral neck (2%, p < 0.01), without changes in bone markers. Women aged > 65 years exhibited a decrease in sCTX levels and stable BMD values at all skeletal sites. E(2) levels decreased similarly in both groups ( approximately 35%). Women with baseline E(2) levels > or = 10 pg/ml showed stable BMD in spite of their E(2) levels decreasing by 42% (p < 0.001); sCTX decreased by 21% (p < 0.01). Women with baseline E(2) levels < 10 pg/ml showed a 2% decrease (p < 0.001) in femoral neck BMD and a 19% decrease (p < 0.002) in E(2) levels, without changes in bone markers. CONCLUSION: Although endogenous E(2) decreased to around 7 pg/ml in these menopausal women, this level would seem to be sufficient to maintain BMD in almost all skeletal areas, and to be more effective in older women.

Low levels of endogenous estradiol protect bone mineral density in young postmenopausal women.

OBJECTIVE: Low levels of endogenous estrogens may play a role in the protection of bone mineral density (BMD) in healthy postmenopausal women. The aim of this study was to evaluate the effect of endogenous estradiol and testosterone on bone mass in young and older healthy postmenopausal women. METHODS: The study involved 99 postmenopausal women aged 55-75 years. The BMDs of the lumbar spine, proximal femur and total skeleton were determined. Measurements were taken of serum calcium, bone alkaline phosphatase, Crosslaps, estradiol, estrone, sex hormone binding globulin, testosterone, bioavailable testosterone and urine calcium. Estradiol was measured using a sensitive assay with a lower detection limit at 5 pg/ml. RESULTS: A multivariate analysis showed that the BMD of the lumbar spine was significantly predicted by estradiol (p < 0.05), and testosterone (p < 0.0001). Likewise, testosterone was found to be an independent predictor of the BMD of the total femur (p < 0.001) and the total skeleton (p < 0.001). The population was divided into two groups: < or = 65 (Group 1) and > 65 years (Group 2) of age and also stratified according to estradiol levels: > 10 and < or = 10 pg/ml. Significant differences in BMD were found in women in Group 1 in whom estradiol levels higher than 10 pg/ml were associated with a higher BMD of the lumbar spine (+ 14%, p < 0.01), proximal femur (+ 6%, p < 0.05) and total skeleton (+ 7%, p < 0.05) compared with women with estradiol levels below 10 pg/ml. Bone alkaline phosphatase levels (p < 0.05) and serum Crosslaps (not significant) were lower in women in Group 1 with a level of estradiol more than 10 pg/ ml. CONCLUSION: Endogenous estradiol levels higher than 10 pg/ml and testosterone protected bone mass in healthy postmenopausal women under 65 years of age. These results were not observed in the group of older women.

Polarization-modulated second harmonic generation imaging: method for quantitative assessment of disorganization in anulus.

An experimental method for quantifying disorder within the anulus fibrosus is described based on polarization-modulated second harmonic generation imaging (PM-SHG-I). This method is demonstrated by imaging the anular lamellar architecture of a mouse model of compressive loading. Results were consistent with those obtained in an earlier study where organization was quantified directed secants image analysis on photomicrographs. In this study the orientation within individual lamellia is quantified by average orientation of the collagen molecules within a defined volume of a single lamellar as measured by the PM-SHG-I. Lamellar boundaries can be identified through the SHG intensity images, and confirmed through co-registration with photomicrographs of the same region. The orientation within the lamellar is quantified by the polarization angle of the maximum second harmonic intensity. PM-SHG-I offers several advantages as compared with the method of directed secants: first, it is nondestructive, allowing repeated measurements of the same tissue; second, images are captured on the order of seconds and capable of obtaining information up to a depth of 200-300 microns, thus allowing for real-time assessment of load damage; third, organization is measured at a much higher resolution, as it is based on disorder within the molecular arrays of a single lamella.

Molecular engineering of polymer films for amplitude and phase measurements of Ti:sapphire femtosecond pulses.

Using second-harmonic frequency-resolved optical gating and a tricyanovinylaniline polymer thin film, we have measured the amplitude and the phase of mode-locked Ti:sapphire laser pulses as short as 13 fs. These thin films are ideally suited for ultrashort-pulse diagnostics because they eliminate the angle tuning associated with birefringent phase-matched crystals, minimize pulse distortions introduced by group-velocity dispersion, and exhibit excellent photochemical stability.

400-Hz mechanical scanning optical delay line.

We have developed a simple, high-speed, nearly vibration-free, mechanically scanned, optical delay line suitable for femtosecond time-resolved signal-averaging measurements. We demonstrate a 2-ps time window autocorrelator with a display updated at 400 Hz. The delay line uses a dithering planar mirror as a time-varying linear phase ramp in the spectral plane of a modified grating-lens femtosecond pulse shaper. The time delay is linearly proportional to the angular deviation of the mirror. The high speed and low vibration are a result of the extremely small angular changes required to generate a large time delay.