High accuracy wide field imaging method in radio interferometry

With the development of modern radio interferometers, wide-field continuum surveys have been planned and undertaken, for which accurate wide-field imaging methods are essential. Based on the widely-used W-stacking method, we propose a new wide-field imaging algorithm that can synthesize visibility data from a model of the sky brightness via degridding, able to construct dirty maps from measured visibility data via gridding. Results carry the smallest approximation error yet achieved relative to the exact calculation involving the direct Fourier transform. In contrast to the original W-stacking method, the new algorithm performs least-misfit optimal gridding (and degridding) in all three directions, and is capable of achieving much higher accuracy than is feasible with the original algorithm. In particular, accuracy at the level of single precision arithmetic is readily achieved by choosing a least-misfit convolution function of width W = 7 and an image cropping parameter of x0 = 0.25. If the accuracy required is only that attained by the original W-stacking method, the computational cost for both the gridding and FFT steps can be substantially reduced using the proposed method by making an appropriate choice of the width and image cropping parameters.

Correlation between Ultra-Wide-Field Retinal Imaging Findings and Vascular Supra-Aortic Changes in Takayasu Arteritis

(1) Background: Takayasu arteritis (TA) is a chronic inflammatory large-vessel vasculitis. Ultra-wide-field imaging allows describing the retinal lesions in these patients and correlating them with vascular supra-aortic stenosis. (2) Methods: In total, 54 eyes of 27 patients diagnosed with TA were included, and a complete ophthalmological examination was performed, including UWF color fundus photography (UWF-CFP), fluorescein angiography (UWF-FA), and computed tomography angiography measuring supra-aortic stenosis. Eleven patients underwent Doppler ultrasound imaging assessing the blood flow velocity (BFV) in the central retinal artery (CRA). (3) Results: Microaneurysms were detected in 18.5% of eyes on fundus examination, in 24.4% of eyes on UWF-CFP, and in 94.4% of eyes on UWF-FA. The number of microaneurysms significantly correlated with the presence of an ipsilateral supra-aortic stenosis (p = 0.026), the presence of hypertension (p = 0.0011), and the duration of the disease (p = 0.007). The number of microaneurysms per eye negatively correlated with the BFV in the CRA (r = −0.61; p = 0.003). (4) Conclusions: UWF-FA improved the assessment of TA-associated retinal findings. The significant correlation between the number of microaneurysms and the BFV in the CRA gives new insight to our understanding of Takayasu retinopathy. The total number of microaneurysms could be used as an interesting prognostic factor for TA.

De-scattering with Excitation Patterning enables rapid wide-field imaging through scattering media

Nonlinear optical microscopy has enabled in vivo deep tissue imaging on the millimeter scale. A key unmet challenge is its limited throughput especially compared to rapid wide-field modalities that are used ubiquitously in thin specimens. Wide-field imaging methods in tissue specimens have found successes in optically cleared tissues and at shallower depths, but the scattering of emission photons in thick turbid samples severely degrades image quality at the camera. To address this challenge, we introduce a novel technique called De-scattering with Excitation Patterning or “DEEP,” which uses patterned nonlinear excitation followed by computational imaging–assisted wide-field detection. Multiphoton temporal focusing allows high-resolution excitation patterns to be projected deep inside specimen at multiple scattering lengths due to the use of long wavelength light. Computational reconstruction allows high-resolution structural features to be reconstructed from tens to hundreds of DEEP images instead of millions of point-scanning measurements.