Fast-scanning reflection-mode integrated photoacoustic and optical-coherence microscopy

We previously demonstrated that multimodal microscopy combining photoacoustic microscopy and optical coherence tomography can provide comprehensive insight into biological tissue at μm-level resolution by exploiting both optical absorption and scattering contrasts. Recently, we have developed a second-generation integrated photoacoustic and optical-coherence microscope, which can potentially be adapted for clinical applications. In this new system, we can perform photoacoustic and optical-coherence imaging simultaneously at a speed of 5,000 A-lines per second with real-time on-screen display. Also, both modalities now work in reflection mode instead of transmission mode, allowing easy access to various anatomical locations of interest. Imaging of skin and eye has been demonstrated in living small animals

Label-free photoacoustic ophthalmic angiography

We present label-free functional photoacoustic imaging of the ocular microvasculature in living animals. The anterior segment of an adult mouse was imaged with a laser exposure level well within the American National Standards Institute safety standards. Individual red blood cells traveling along the iris capillaries were clearly resolved, and the hemoglobin oxygen saturation in the iris microvasculature was imaged spectrally. We believe that photoacoustic imaging has the potential to advance the diagnosis and treatment of ocular diseases in humans

Integrated photoacoustic, confocal, and two-photon microscope

The invention of green fluorescent protein and other molecular fluorescent probes has promoted applications of confocal and two-photon fluorescence microscopy in biology and medicine. However, exogenous fluorescence contrast agents may affect cellular structure and function, and fluorescence microscopy cannot image nonfluorescent chromophores. We overcome this limitation by integrating optical-resolution photoacoustic microscopy into a modern Olympus IX81 confocal, two-photon, fluorescence microscope setup to provide complementary, label-free, optical absorption contrast. Automatically coregistered images can be generated from the same sample. Imaging applications in ophthalmology, developmental biology, and plant science are demonstrated. For the first time, in a familiar microscopic fluorescence imaging setting, this trimodality microscope provides a platform for future biological and medical discoveries

In vivo, dual-modality imaging of mouse eyes: optical coherence tomography and photoacoustic microscopy within a single instrument

Optical-resolution photoacoustic microscopy (OR-PAM) provides superb optical absorption contrast for red blood cells (RBCs), which makes it ideal for in vivo microvasculature imaging. In comparison, optical coherence tomography (OCT), widely used for tissue microstructure imaging, provides high optical scattering contrast. The two contrast mechanisms are highly complementary. In this work, we combined OR-PAM and OCT into a single, dual-modality imaging instrument for in vivo mouse eye imaging. We demonstrated in vivo dual-modality imaging of the anterior segment of mouse eyes with laser pulse energy within the ANSI laser safety standard

Training needs assessment in Malaysia: Exercise held at Kuala Lampur and Kota Bharu from 13th October 1989

Training / Irrigation / Evaluation / Malaysia

The angular spectrum of the scattering coefficient map reveals subsurface colorectal cancer

Abstract Colorectal cancer diagnosis currently relies on histological detection of endoluminal neoplasia in biopsy specimens. However, clinical visual endoscopy provides no quantitative subsurface cancer information. In this ex vivo study of nine fresh human colon specimens, we report the first use of quantified subsurface scattering coefficient maps acquired by swept-source optical coherence tomography to reveal subsurface abnormities. We generate subsurface scattering coefficient maps with a novel wavelet-based-curve-fitting method that provides significantly improved accuracy. The angular spectra of scattering coefficient maps of normal tissues exhibit a spatial feature distinct from those of abnormal tissues. An angular spectrum index to quantify the differences between the normal and abnormal tissues is derived, and its strength in revealing subsurface cancer in ex vivo samples is statistically analyzed. The study demonstrates that the angular spectrum of the scattering coefficient map can effectively reveal subsurface colorectal cancer and potentially provide a fast and more accurate diagnosis

Six-Minute Walk Test Performance in Healthy Adult Pakistani Volunteers

Objective: To determine the six-minute walking distance (6MWD) for healthy Pakistanis, identify factors affecting 6MWD, compare published equations with the local data and derive an equation. Study Design: Cross-sectional study. Place and Duration of Study: Two medical institutes of Karachi, from January to May 2011. Methodology: Subjects between 15 and 65 years were prospectively enrolled after screening. A standardized 6MWT was administered. SpO2, HR, BP and dyspnoea scores were determined pre- and post-test. Results: Two hundred and eleven (71%) men and 85 (29%) women participated. Mean 6MWD was 469.88 ± 101.24 m: men walked 502.35 ± 92.21 m and women walked 389.28 ± 74.29 m. On univariate analysis, gender, height, weight and age showed a significant relationship with the 6MWD. Gender and age were identified as independent factors in multiple regression analysis, and together explained 33% of the variance. The gender-specific prediction equations were: 6MWD (m) for men = 164.08 + (78.06*1) - (1.90*age in years) + (1.95*height in cms) 6MWD (m) for women = 164.08 - (1.90*age in years) + (1.95*height in cms). Conclusion: 6MWDs among the volunteer subjects were shorter than predicted by reference equations in literature. Height, gender and weight combined explained 33% of the variance. The moderate over-estimation of the 6MWD in Pakistani subject. The proposed equation gives predicted (mean) 6MWDs for adult Pakistani naïve to the test when employing standardized protocol