Microsphere-assisted super-resolved hyperspectral microscopy.

Hyperspectral microscopy (HSM) combines conventional microscopy with basic hyperspectral imaging and results in 3D microscopic spatio-spectral information. The combination comes along with a variety of applications, such as detection and classification of different material properties through spectral fingerprints, which otherwise cannot be detected with a color camera alone. However, similar to other microscopies, the resolution of HSM is limited by diffraction. In recent years microsphere (MS)-assisted microscopy has attracted intensive attention for resolution enhancement. Here, we extend the MS idea into HSM. We show that MS-HSM reveals extra hyperspectral information about the specimen which is lost without it. Moreover, the insertion of MS results in super-resolved images. The resolution enhancement and obtaining the extra hyperspectral information can be tuned by the MS size.

Ultrahigh-dynamic-range wavefront sensor based on absolute double-slit interferometry.

This Letter reports a new, to the best of our knowledge, technique for the quality testing of steep optical samples by introducing an absolute interferometry method based on a double-slit interference experiment. We determine the quality of the sample with an ultrahigh-dynamic-range wavefront sensor by determining the deformation of the central fringe of the double-slit interferometer recorded for two different separations of the slits. The transmission function of the double slit is implemented on an amplitude spatial light modulator. Therefore, the slits' location can be easily displaced over the entire area of the sample's wavefront. We applied the proposed method on two samples: a microscope slide and a conventional ophthalmic lens, and maximum absolute phase variations of 0.33 and 26.7 rad were measured, respectively. Our estimation shows that an absolute phase variation of about 700 rad can be measured with this method.

Absolute interferometric testing of a flat surface based on the Laplacian method.

In the present study, a method is introduced for absolute interferometric testing. An interferometer is used to measure the phase difference distributions at five positions of the reference surface with respect to the test surface. The Laplacian of the phase distribution is calculated from the measured phase difference distributions. Then, the reference phase distribution is reconstructed by solving the Laplacian equation by the Fourier method. The accuracy of the method with respect to the amount of the displacement and noise is investigated by simulation and compared with the conjugate differential method. It is shown that the spatial frequencies of the phase distributions reconstructed by the Laplacian method are less filtered out with respect to the conjugate differential methods. Finally, the experimental result is presented.

Accurate testing of aspheric surfaces using the transport of intensity equation by properly selecting the defocusing distance.

In the last decade, the transport of intensity has been increasingly used in microscopy, wavefront sensing, and metrology. In this study, we verify by simulation and experiment the use of the transport of intensity equation (TIE) in the accurate testing of optical aspheric surfaces. Guided by simulation results and assuming that the experimental setup parameters and the conic constants are known, one can estimate an appropriate defocusing distance Δz that leads to an accurate solution of the TIE. In this paper, this method is verified through the construction of a non-nulled experiment for testing the 2D profile of an aspheric surface. The theoretical method and experimental results are compared to validate the results. Finally, to validate the TIE methodology, the phase distribution obtained by TIE is compared with the phase distribution obtained by a Shack-Hartmann sensor.

Fully automated, high speed, tomographic phase object reconstruction using the transport of intensity equation in transmission and reflection configurations.

While traditional transport of intensity equation (TIE) based phase retrieval of a phase object is performed through axial translation of the CCD, in this work a tunable lens TIE is employed in both transmission and reflection configurations. These configurations are extended to a 360° tomographic 3D reconstruction through multiple illuminations from different angles by a custom fabricated rotating assembly of the phase object. Synchronization circuitry is developed to control the CCD camera and the Arduino board, which in its turn controls the tunable lens and the stepper motor to automate the tomographic reconstruction process. Finally, a MATLAB based user friendly graphical user interface is developed to control the whole system and perform tomographic reconstruction using both multiplicative and inverse radon based techniques.

Application of transport-of-intensity equation in fringe analysis.

The transport-of-intensity equation (TIE) is applied in the reconstruction of two interfering wavefronts by analyzing the interference patterns and their derivatives along their common propagation directions. The TIE is extended from one wave to two waves and is then applied to calculate the phase of the interference field. Finally, the phase shift concept is applied to reconstruct the phase distribution of two waves. The consistency of the method is verified by simulation.

Cardioprotection by mild hypothermia during ischemia involves preservation of ERK activity.

Cooling the ischemic heart by just a few degrees protects it from infarction without affecting its mechanical function, but the mechanism of this protection is unknown. We investigated whether signal transduction pathways might be involved in the anti-infarct effect of mild hypothermia (35°C). Isolated rabbit hearts underwent 30 min of coronary artery occlusion/2 h of reperfusion. They were either maintained at 38.5°C or cooled to 35°C just before and only during ischemia. Infarct size was measured. The effects of the protein kinase C inhibitor chelerythrine, the nitric oxide synthase inhibitor N (ω)-nitro-L: -arginine methyl ester (L: -NAME), the phosphatidylinositol 3-kinase antagonist wortmannin, or either of the mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitors PD98059 or U0126 on cooling's protection were examined. Myocardial ATP assays were performed and the level of phosphorylation of extracellular signal-regulated kinase (ERK) and MEK was examined by western blotting. To investigate an effect of cooling on protein phosphatase (PPase), a PPase inhibitor cantharidin was tested in the infarct model and the effect of mild hypothermia on PP2A activity in vitro was measured. Infarct size was 34.4 ± 2.2% of the ischemic zone in normothermic (38.5°C) hearts, but only 15.6 ± 8.7% in hearts cooled to 35°C during ischemia. Mechanical function was unaffected. Neither chelerythrine, L: -NAME, nor wortmannin had any effect, but both PD98059 and U0126 completely eliminated protection. Ischemia rather than reperfusion was the critical time when ERK had to be active to realize protection. Phosphorylation of ERK and MEK fell during normothermic ischemia, but during hypothermic ischemia phosphorylation of ERK remained high while that of MEK was increased. Cooling only slightly delayed the rate at which ATP fell during ischemia, and ERK inhibition did not affect that attenuation suggesting ATP preservation was unrelated to protection. Cantharidin, like cooling, also protected during ischemia but not at reperfusion, and its protection was dependent on ERK phosphorylation. However, mild hypothermia had a negligible effect on PP2A activity in an in vitro assay. Hence, mild hypothermia preserves ERK and MEK activity during ischemia which somehow protects the heart. While a PPase inhibitor mimicked cooling's protection, a direct effect of cooling on PP2A could not be demonstrated.

Prophylactic use of manual thrombectomy in ST-segment elevation myocardial infarction.

OBJECTIVE: We sought to evaluate the effects of manual thrombectomy on myocardial reperfusion performed during percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI). BACKGROUND: Complete reperfusion after primary PCI is compromised by the presence of intraluminal thrombus. Thus effective and safe extraction of thrombus in a timely fashion is important for successful reperfusion. METHODS: Thirty-two patients (age 51+/-12 years, males 78%) with STEMI and angiographic evidence of intraluminal thrombus underwent thrombectomy during an 18-month period. Thrombectomy was performed after the presence of thrombus was confirmed angiographically by the operator either before or after primary angioplasty. Thrombectomy was performed using the 6F Export Aspiration Catheter (Medtronic Corporation, Santa Rosa, CA, USA). Myocardial reperfusion using Thrombolysis in Myocardial Infarction (TIMI) flow and myocardial blush grade was assessed by two independent observers. RESULTS: The infarct-related artery was left anterior descending (59%), right coronary artery (19%), saphenous venous graft (19%), or left circumflex artery (3%). The coronary lesion was Type B in 62% and Type C in 37% patients, with an average length of 18.2+4.6 mm and reference vessel diameter of 3.2+/-0.4 mm. The preprocedural TIMI flow was 0 in 62%, 1 in 12%, 2 in 22%, and 3 in 3% of patients. The postprocedural TIMI flow was 0 in 3%, 1 in 6%, 2 in 25%, and 3 in 56% of patients. The postprocedural myocardial blush grade was 0 in 6%, 1 in 9%, 2 in 35%, and 3 in 48% of patients. The in-hospital mortality was 0 and the 30-day mortality was 3%. CONCLUSION: Manual thrombectomy using an Export catheter is safe and effective in establishing myocardial reperfusion after STEMI.

Reduced exercise capacity and stress-induced pulmonary hypertension in patients with scleroderma.

OBJECTIVES: We sought to determine the incidence of stress-induced pulmonary artery (PA) systolic hypertension in a referral population of patients with scleroderma, and to examine the relation between stress-induced pulmonary systolic hypertension and exercise capacity in this population. BACKGROUND: Early detection of patients with scleroderma at risk for pulmonary hypertension (PHTN) could lead to more timely intervention and thus reduce morbidity and improve mortality. The change in PA systolic pressure (PASP) with exercise provides a possible tool for such detection. METHODS: Sixty-five patients with scleroderma (9 men and 56 women; mean age 51 +/- 12 years [SD]), normal resting PASP, and normal resting left ventricular function underwent exercise Doppler echocardiography using a standard Bruce protocol. Tricuspid regurgitation velocity was measured before and after exercise. Exercise variables including workload achieved in metabolic equivalents (METS), total exercise time, percentage of target heart rate achieved, and PASP at rest and within 60 s after exercise were recorded. RESULTS: Thirty patients (46%) demonstrated an increase in PASP to > 35 mm Hg plus an estimated right atrial pressure of 5 mm Hg. Postexercise PASP inversely correlated to both the maximum workload achieved (r = - 0.34, p = 0.006) and exercise time (r = - 0.31, p = 0.01). In women, the correlation was more significant (r = - 0.38, p = 0.003). Patients in the lowest quartile of exercise time, with the least cardiac workload achieved, produced the highest postexercise PASP. CONCLUSION: Stress-induced PHTN is common in patients with scleroderma, even when resting PASP is normal. Stress Doppler echocardiography identifies scleroderma patients with an abnormal rise in PASP during exertion. Peak PASP is linearly related to exercise time and maximum workload achieved. Measurement of PASP during exercise may prove to be a useful tool for the identification of future resting PHTN.