: Metasurfaces—subwavelength arrays of phase-shifting elements—present new pos-sibilities for polarization optics and polarimetry. In particular, a periodic, polarization-sensitive metasurface diffraction grating can enable full-Stokes imaging polarimetry with a single polarization-sensitive component. In this work, we show that a suitably-designed metasurface grating can serve as a polarimetric “attachment” to an existing intensity-only imaging system, converting it into one capable of full-Stokes imaging polarimetry. Design rules and tradeoffs governing this adaptation are described and demonstrated using a machine vision imaging system as an example.

Imaging polarimetry through metasurface polarization gratings

: All-optical ultrasound (OpUS) has emerged as an imaging paradigm well-suited to minimally invasive imaging due to its ability to provide high resolution imaging from miniaturised fibre optic devices. Here, we report a fibre optic device capable of concurrent laser interstitial thermal therapy (LITT) and real-time in situ all-optical ultrasound imaging for lesion monitoring. The device comprised three optical fibres: one each for ultrasound transmission, reception and thermal therapy light delivery. This device had a total lateral dimension of < 1 mm and was integrated into a medical needle. Simultaneous LITT and monitoring were performed on ex vivo lamb kidney with lesion depth tracked using M-mode OpUS imaging. Using one set of laser energy parameters for LITT (5 W, 60 s), the lesion depth varied from 3.3 mm to 8.3 mm. In all cases, the full lesion depth could be visualised and measured with the OpUS images and there was a good statistical agreement with stereomicroscope images acquired after ablation (t = 1.36, p = 0.18). This work demonstrates the feasibility and potential of OpUS to guide LITT in tumour resection.

Miniaturised dual-modality all-optical ultrasound probe for laser interstitial thermal therapy (LITT) monitoring

: Photoacoustic (PA) endoscopy has shown significant potential for clinical diagnosis and surgical guidance. Multimode fibres (MMFs) are becoming increasingly attractive for the development of miniature endoscopy probes owing to their ultrathin size, low cost and diffraction-limited spatial resolution enabled by wavefront shaping. However, current MMF-based PA endomicroscopy probes are either limited by a bulky ultrasound detector or a low imaging speed that hindered their usability. In this work, we report the development of a highly miniaturised and high-speed PA endomicroscopy probe that is integrated within the cannula of a 20 gauge medical needle. This probe comprises a MMF for delivering the PA excitation light and a single-mode optical fibre with a plano-concave microresonator for ultrasound detection. Wavefront shaping with a digital micromirror device enabled rapid raster-scanning of a focused light spot at the distal end of the MMF for tissue interrogation. High-resolution PA imaging of mouse red blood cells covering an area 100 µ m in diameter was achieved with the needle probe at ∼ 3 frames per second. Mosaicing imaging was performed after fibre characterisation by translating the needle probe to enlarge the field-of-view in real-time. The developed ultrathin PA endomicroscopy probe is promising for guiding minimally invasive surgery by providing functional, molecular and microstructural information of tissue in real-time.

Ultrathin, high-speed, all-optical photoacoustic endomicroscopy probe for guiding minimally invasive surgery

Toxoplasma gondii (T. gondii) is an intracellular protozoan parasite that causes the disease Toxoplasmosis. Acute infection of T. gondii in pregnant women is dangerous because the parasite can transmit into developing foetus and can cause congenital toxoplasmosis. To assess the prevalence of T. gondii infection, its association with pregnancy and the impact of this parasite on generating oxidative stress, ninety-two pregnant women and sixty-five age matched non-pregnant control subjects were enrolled in this study. Using an immunological assay with a rapid test cassette, T. gondii specific IgG antibody was detected in 25% pregnant women while it was found only 9.2% in non-pregnant healthy control subjects, suggesting that a higher percentage of pregnant women carried chronic T. gondii infection compared to control subjects. Anti-T. gondii IgM was also tested and found to be positive in only 3.3 % pregnant women as compared to control. Polymerase Chain Reaction analysis was carried out with the DNA isolated from blood of both anti-T. gondii IgM and IgG positive pregnant women and was found to be negative for T. gondii REP-529 gene, suggesting a chronic infection. Our data suggest that pregnant women who were in contact with cat in their third trimester of pregnancy demonstrated a significantly higher association with acquiring infection. Furthermore, to determine any association of T. gondii infection with oxidative stress in pregnant women, oxidative stress markers were assessed in plasma samples. The total oxidative stress was found to be higher in T. gondii positive subjects compared to T. gondii negative samples whereas total antioxidant defence was observed to be slightly decreased in T. gondii positive pregnant women. It can primarily be said that chronic T. gondii infection in pregnant women may increase oxidative stress and this, therefore, may act as a risk factor for congenital toxoplasmosis.

Toxoplasma gondii enhances oxidative stress in pregnant women: a case-control study

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Papers

Imaging polarimetry through metasurface polarization gratings

Miniaturised dual-modality all-optical ultrasound probe for laser interstitial thermal therapy (LITT) monitoring

Ultrathin, high-speed, all-optical photoacoustic endomicroscopy probe for guiding minimally invasive surgery

Toxoplasma gondii enhances oxidative stress in pregnant women: a case-control study