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The cosmological nature of gamma-ray bursts (GRBs) implies that a small portion of them could be gravitationally lensed by foreground objects during their propagation. The gravitational lensing effect on the GRB prompt emission and on-axis afterglows has been discussed, and some candidates have been found in the literature. In this work, considering the high detection rate of GRB orphan afterglows in future wide-field survey era, we investigate the gravitationally lensed orphan afterglows in view of three lens models, i.e., the point-mass model, the singular isothermal sphere model, and the Chang-Refsdal model. The structure of the GRB jet itself is also incorporated in calculating the lensed afterglow light curves. It is found that lensed optical/X-ray orphan afterglows in principle could be diagnosed through their temporal characteristics, and the optical band is the best band to observe the galaxy-lensed orphan afterglows. Moreover, the event rate for galaxy-lensed orphan afterglows is estimated to be $\lesssim$ 1.8 $\text{yr}^{-1}$ for the whole sky. If most orphan afterglows could be identified (from other transients in the survey data), the optimistic detection rates of the 2.5m Wide Field Survey Telescope of China and 8.4m Vera Rubin Observatory Legacy Survey of Space and Time for galaxy-lensed orphan afterglows in the optical band are $\lesssim$ 0.01$\sim$0.02 $\text{yr}^{-1}$ and $\lesssim$ 0.04$\sim$0.08 $\text{yr}^{-1}$, respectively., 13 pages, 10 figures, Accepted for publication in MNRAS

Objective. We are developing a portable, ‘RF-penetrable’, brain-dedicated time of flight (TOF)-PET insert (PETcoil) for simultaneous PET/MRI. Approach. In this paper, we evaluate the PET performance of two fully assembled detector modules for this insert design outside the MR room. Main results. The global coincidence time resolution, global 511 keV energy resolution, coincidence count rate, and detector temperature achieved over 2 h data collection were 242.2 ± 0.4 ps full width at half maximum (FWHM), 11.19% ± 0.02% FWHM, 22.0 ± 0.1 kcps, and 23.5 °C ± 0.3 °C, respectively. The intrinsic spatial resolutions in the axial and transaxial directions were 2.74 ± 0.01 mm FWHM and 2.88 ± 0.03 mm FWHM, respectively. Significance. These results demonstrate excellent TOF capability and the performance and stability necessary for scaling up to a full ring comprising 16 detector modules.

1.1 Background Hand-pose is one of the most important communication tools in human’s daily life. In a situation when people from different countries are trying to communicate, they may be able to roughly express their thought through hand-poses or hand-gestures. During an oral presentation, a presenter may use hand-poses as an auxiliary tool to convey his or her idea for technical communication. In practice, the use of “sign language” is a typical example that provides an effective mechanism for exchanging information among deaf people and the hearing society. In essence, “sign language” can be considered as a combination of many hand-poses that define the actual information. With the continuous advances of speech, image, and video processing techniques, humanmachine interaction is constantly making progress over the past decades. For example, speech recognition systems (Cooke et al., 2001; Gales, 1998) are designed to recognize and translate human’s speech to text. Handwritten recognition systems (Liu et al., 2003; Palacios & Gupta, 2002; Zhai & Kristensson, 2003) are designed to recognize and translate human’s handwritten to text. A palmprint identification system (Zhang et al. 2003) is a biometric approach to recognize human’s palmprint for personal identification. A safety vehicle system (Trivedi et al., 2007) can be used to estimate the situation around a vehicle and convey information to warn the driver for potential dangers such that the vehicle safety could be improved. In summary, many of these systems have been found to be feasible in enhancing the human-machine interaction and integrated in daily applications (e.g., cell phones, notebooks, security system, etc.).

Supplemental Information

Currently, clinical permanently-integrated PET/MRI systems are available. However, their high cost impedes the wide dissemination of PET/MR imaging. To address this, we have proposed an RF-penetrable time of flight (TOF)-PET insert to achieve simultaneous PET/MRI at a lower cost with no performance compromise; this system can be inserted into any existing MR system and is TOF-capable. This paper evaluates performance of two detector modules. The coincidence timing resolution (CTR) for all positions was in the range from 244.3 ± 0.7 to 260.5 ± 0.9 ps. The energy resolution was from 13.45 ± 0.02 % to 13.64 ± 0.01 %. The error bars for all performance parameters were less than 1%. The results demonstrate the TOF capability of the system and the performance stability to scale up to a full ring.

Purpose An "RF-penetrable" PET insert that allows the MR body coil to be used for RF transmission was developed to make it easier for an existing MR center to achieve simultaneous PET/MRI. This study focuses on experiments and analyses to study PET/RF coil configurations for simultaneous PET/MR studies. Methods To investigate the appropriate RF coil design, a transmit/receive (TX/RX) birdcage coil and an RX-only phased-array coil (TX from body coil), both fitting inside the PET ring were built and characterized. For MR performance evaluation, B1 field uniformity and MR image SNR were calculated. PET photon attenuation due to each coil was studied by means of CT-based attenuation maps and reconstructed PET images. Results When using the RX-only phased-array coil (TX from body coil), compared with the TX/RX birdcage coil, the B1 field uniformity and the MR image (gradient echo and fast spin echo) SNR increased by 2.4±4.8%, 386.1±62.3%, and 205.0±56.5%, respectively. Although some components of the coil were distributed within the PET FOV, no significant PET photon attenuation was shown in the CT-based attenuation map and reconstructed PET images. Conclusion RF coil configurations for an RF-penetrable PET insert for simultaneous PET/MRI were studied. The RX-only phased-array coil (TX from body coil) outperformed the TX/RX birdcage coil with improved MR performance as well as negligible PET photon attenuation.

Hybrid positron emission tomography (PET)/magnetic resonance imaging (MRI) has risen to the cutting edge of medical imaging technology as it allows simultaneous acquisition of structural, functional, and molecular information of the patient. A PET insert that can be installed into existing MR systems can in principle reduce the cost barriers for an existing MR site to achieve simultaneous PET/MRI compared to procuring an integrated PET+MRI system. The PET insert systems developed so far for PET/MRI require the radio-frequency (RF) transmitter coil to reside inside the PET ring as those PET inserts block the RF fields from the MRI system. Here we report for the first time on the performance of a full-ring brain-sized “RF-penetrable” PET insert we have recently completed. This insert allows the RF fields generated by the built-in body coil to penetrate the PET ring. The PET insert comprises a ring of 16 detector modules employing electro-optical coupled signal transmission and a multiplexing framework based on compressed sensing. Energy resolution, coincidence timing resolution (CTR), photopeak position, and coincidence count rate were acquired outside and inside a 3-Tesla MRI system under simultaneous acquisition to evaluate the impact of MRI on the PET performance. Coincidence count rate performance was evaluated by acquiring a cylinder source with high initial activity decaying over time. Tomographic imaging of two phantoms, a custom 6.5-cm diameter resolution phantom with hot rods of four different sizes (2.8-, 3.2-, 4.2-, and 5.2-mm diameter) and a 3-D Hoffman brain phantom, were performed to evaluate the imaging capability of the PET insert. The energy resolution at 511 keV and CTR acquired by the PET insert were 16.2 ± 0.1% and 5.3 ± 0.1 ns full width at half maximum, respectively, and remained stable during MRI operation except when the echo planar imaging (EPI) sequence was applied. The PET system starts to show saturation in coincidence count rate at 2.76 million photon counts per second. Most of the 2.8-mm diameter hot rods and main features of the 3-D Hoffman brain phantom were resolved by the PET insert, demonstrating its high spatial resolution and capability to image a complex tracer distribution mimicking that seen in the human brain.