Near‐range scintillations in a nonisotropic scattering medium

Abstract Background A gamma probe is a handheld device used for intraoperative interventions following interstitial injection of a radiotracer to locate regional lymph nodes through the external detection of radiation. This work reports on the design and performance evaluation of a novel fully integrated gamma probe (GammaPen), recently developed by our group. Materials and methods GammaPen is an all-in-one pocket gamma probe with low weight and adequate dimensions, consisting of a detector, a control unit and output all together. The detector module consists of a cylindrical Thallium-activated Cesium Iodide [CsI (Tl)] crystal optically coupled to a Silicon photomultiplier (SiPM), shielded using Tungsten housing on side and back faces. The electronics of the probe consists of two small boards to handle signal processing and analog peak detection tasks. A number of parameters, including probe sensitivity in air/water, spatial resolution in air/water, angular resolution in air/water, and side and back shielding effectiveness, were measured to evaluate the performance of the probe based on NEMA NU3-2004 standards. Results The sensitivity of the probe in air at distances of 10, 30, and 50 mm is 18784, 3500, and 1575 cps/MBq. The sensitivity in scattering medium was also measured at distances of 10, 30, and 50 mm as 17,680, 3050, and 1104 cps/MBq. The spatial and angular resolutions in scattering medium were 47 mm and 87 degree at 30 mm distance from the probe, while they were 40 mm and 77 degree in air. The detector shielding effectiveness and leakage sensitivity are 99.91% and 0.09%, respectively. Conclusion The performance characterization showed that GammaPen can be used effectively for sentinel lymph node localization. The probe was successfully used in several surgical interventions by an experienced surgeon confirming its suitability in a clinical setting.

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ASKAP observations of multiple rapid scintillators reveal a degrees-long plasma filament

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab139 ◽

2021 ◽

Vol 502 (3) ◽

pp. 3294-3311

Author(s):

Yuanming Wang ◽

Artem Tuntsov ◽

Tara Murphy ◽

Emil Lenc ◽

Mark Walker ◽

...

Keyword(s):

Physical Properties ◽

Angular Width ◽

Scattering Medium ◽

Central Frequency ◽

Linear Arrangement ◽

Plasma Filament ◽

Kinematic Models ◽

Tidal Stream ◽

First Time ◽

Insight Into

ABSTRACT We present the results from an Australian Square Kilometre Array Pathfinder search for radio variables on timescales of hours. We conducted an untargeted search over a 30 deg2 field, with multiple 10-h observations separated by days to months, at a central frequency of 945 MHz. We discovered six rapid scintillators from 15-min model-subtracted images with sensitivity of $\sim\! 200\, \mu$Jy/beam; two of them are extreme intra-hour variables with modulation indices up to $\sim 40{{\ \rm per\ cent}}$ and timescales as short as tens of minutes. Five of the variables are in a linear arrangement on the sky with angular width ∼1 arcmin and length ∼2 degrees, revealing the existence of a huge plasma filament in front of them. We derived kinematic models of this plasma from the annual modulation of the scintillation rate of our sources, and we estimated its likely physical properties: a distance of ∼4 pc and length of ∼0.1 pc. The characteristics we observe for the scattering screen are incompatible with published suggestions for the origin of intra-hour variability leading us to propose a new picture in which the underlying phenomenon is a cold tidal stream. This is the first time that multiple scintillators have been detected behind the same plasma screen, giving direct insight into the geometry of the scattering medium responsible for enhanced scintillation.

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A study on spatial filtering of a speckle image reflected from a scattering medium in a coherent beam combining system

Journal of the Korean Physical Society ◽

10.1007/s40042-021-00131-0 ◽

2021 ◽

Author(s):

Jaedeok Park ◽

Yunjin Choe ◽

Dong-Il Yeom

Keyword(s):

Spatial Filtering ◽

Coherent Beam ◽

Scattering Medium ◽

Coherent Beam Combining ◽

Speckle Image ◽

Beam Combining

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Locating and Imaging through Scattering Medium in a Large Depth

Sensors ◽

10.3390/s21010090 ◽

2020 ◽

Vol 21 (1) ◽

pp. 90

Author(s):

Shuo Zhu ◽

Enlai Guo ◽

Qianying Cui ◽

Lianfa Bai ◽

Jing Han ◽

...

Keyword(s):

Phase Space ◽

Signal To Noise Ratio ◽

Speckle Pattern ◽

Heuristic Method ◽

Scattering Medium ◽

Scattering Media ◽

Signal To Noise ◽

Practical Applications ◽

Large Depth ◽

Strong Scattering

Scattering medium brings great difficulties to locate and reconstruct objects especially when the objects are distributed in different positions. In this paper, a novel physics and learning-heuristic method is presented to locate and image the object through a strong scattering medium. A novel physics-informed framework, named DINet, is constructed to predict the depth and the image of the hidden object from the captured speckle pattern. With the phase-space constraint and the efficient network structure, the proposed method enables to locate the object with a depth mean error less than 0.05 mm, and image the object with an average peak signal-to-noise ratio (PSNR) above 24 dB, ranging from 350 mm to 1150 mm. The constructed DINet firstly solves the problem of quantitative locating and imaging via a single speckle pattern in a large depth. Comparing with the traditional methods, it paves the way to the practical applications requiring multi-physics through scattering media.

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