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Tensor fields are useful for modeling the structure of biological tissues. The challenge to measure tensor fields involves acquiring sufficient data of scalar measurements that are physically achievable and reconstructing tensors from as few projections as possible for efficient applications in medical imaging. In this paper, we present a filtered back-projection algorithm for the reconstruction of a symmetric second-rank tensor field from directional X-ray projections about three axes. The tensor field is decomposed into a solenoidal and irrotational component, each of three unknowns. Using the Fourier projection theorem, a filtered back-projection algorithm is derived to reconstruct the solenoidal and irrotational components from projections acquired around three axes. A simple illustrative phantom consisting of two spherical shells and a 3D digital cardiac diffusion image obtained from diffusion tensor MRI of an excised human heart are used to simulate directional X-ray projections. The simulations validate the mathematical derivations and demonstrate reasonable noise properties of the algorithm. The decomposition of the tensor field into solenoidal and irrotational components provides insight into the development of algorithms for reconstructing tensor fields with sufficient samples in terms of the type of directional projections and the necessary orbits for the acquisition of the projections of the tensor field.

PURPOSE: The time-of-flight (TOF) information improves signal-to-noise ratio (SNR) for positron emission tomography (PET) imaging. Existing analytical algorithms for TOF PET usually follow a filtered back-projection process on reconstructing images from the sinogram data. This work aims to develop a back-projection-and-filtering-like (BPF-like) algorithm that reconstructs the TOF PET image directly from listmode data rapidly. METHODS: We extended the 2D conventional non-TOF PET projection model to a TOF case, where projection data are represented as line integrals weighted by the one-dimensional TOF kernel along the projection direction. After deriving the central slice theorem and the TOF back-projection of listmode data, we designed a deep learning network with a modified U-net architecture to perform the spatial filtration (reconstruction filter). The proposed BP-Net method was validated via Monte Carlo simulations of TOF PET listmode data with three different time resolutions for two types of activity phantoms. The network was only trained on the simulated full-dose XCAT dataset and then evaluated on XCAT and Jaszczak data with different time resolutions and dose levels. RESULTS: Reconstructed images show that when compared with the conventional BPF algorithm and the MLEM algorithm proposed for TOF PET, the proposed BP-Net method obtains better image quality in terms of peak signal-to-noise ratio, relative mean square error, and structure similarity index; besides, the reconstruction speed of the BP-Net is 1.75 times faster than BPF and 29.05 times faster than MLEM using 15 iterations. The results also indicate that the performance of the BP-Net degrades with worse time resolutions and lower tracer doses, but degrades less than BPF or MLEM reconstructions. CONCLUSION: In this work, we developed an analytical-like reconstruction in the form of BPF with the reconstruction filtering operation performed via a deep network. The method runs even faster than the conventional BPF algorithm and provides accurate reconstructions from listmode data in TOF-PET, free of rebinning data to a sinogram.

Author(s): Tao, Weijie; Sung, Yongjin; Kim, Sally Ji Who; Huang, Qiu; Gullberg, Grant T; Seo, Youngho; Fuller, Michael | Abstract: PurposeIn this work, we present tomographic simulations of a new hardware concept for X-ray phase-contrast interferometry wherein the phase gratings are replaced with an array of Fresnel biprisms, and Moire fringe analysis is used instead of "phase stepping" popular with grating-based setups.MethodsProjections of a phantom consisting of four layers of parallel carbon microfibers is simulated using wave optics representation of X-ray electromagnetic waves. Simulated projections of a phantom with preferential scatter perpendicular to the direction of the fibers are performed to analyze the extraction of small-angle scatter from dark-field projections for the following: (1) biprism interferometry using Moire fringe analysis; (2) grating interferometry using phase stepping with eight grating steps; and (3) grating interferometry using Moire fringe analysis. Dark-field projections are modeled as projections of voxel intensities represented by a fixed finite vector basis set of scattering directions. An iterative MLEM algorithm is used to reconstruct, from simulated projection data, the coefficients of a fixed set of seven basis vectors at each voxel representing the small-angle scatter distribution.ResultsResults of reconstructed vector coefficients are shown comparing the three simulated imaging configurations. The single-exposure Moire fringe analysis shows not only an increase in noise because of one-eighth the number of projection samples but also is obtained with less dose and faster acquisition times. Furthermore, replacing grating interferometry with biprism interferometry provides better contrast-to-noise.ConclusionThe simulations demonstrate the feasibility of the reconstruction of dark-field data acquired with a biprism interferometry system. With the potential of higher fringe visibility, biprism interferometry with Moire fringe analysis might provide equal or better image quality to that of phase stepping methods with less imaging time and lower dose.

Author(s): Huh, Yoonsuk; Yang, Jaewon; Dim, Odera U; Cui, Yonggang; Tao, Weijie; Huang, Qiu; Gullberg, Grant T; Seo, Youngho | Abstract: PurposeSingle photon emission computed tomography (SPECT) scanners using cadmium zinc telluride (CZT) offer compact, lightweight, and improved imaging capability over conventional NaI(Tl)-based SPECT scanners. The main purpose in this study is to propose a full-ring SPECT system design with eight large-area CZT detectors that can be used for a broad spectrum of SPECT radiopharmaceuticals and demonstrate the performance of our system in comparison to the reference conventional NaI(Tl)-based two-head Anger cameras.MethodsA newly designed full-ring SPECT system is composed of eight large-area CZT cameras (128nmmn×n179.2nmm effective area) that can be independently swiveled around their own axes of rotation independently and can have radial motion for varying aperture sizes that can be adapted to different sizes of imaging volume. Extended projection data were generated by conjoining projections of two adjacent detectors to overcome the limited field-of-view (FOV) by each CZT camera. Using Monte Carlo simulations, we evaluated this new system design with digital phantoms including a Derenzo hot rod phantom and a Zubal brain phantom. Comparison of performance metrics such as spatial resolution, sensitivity, contrast-to-noise ratio (CNR), and contrast-recovery ratio was made between our design and conventional SPECT scanners having different pixel sizes and radii of rotation (one clinically well-known type and two arbitrary types matched to our proposed CZT-SPECT geometries).ResultsThe proposed scanner could result in up to about three times faster in acquisition time over conventional scan time at same acquisition time per step. The spatial resolution improvement, or deterioration, of our proposed scanner compared to the clinical-type scanner was dependent upon the location of the point source. However, there were overall performance improvements over the three different setups of the conventional scanner particularly in volume sensitivity (approximately up to 1.7 times). Overall, we successfully reconstructed the phantom image for both 99m Tc-based perfusion and 123 I-based dopamine transporter (DaT) brain studies simulated for our new design. In particular, the striatal/background contrast-recovery ratio in 3-to-1 reference ratio was over 0.8 for the 123 I-based DaT study.ConclusionsWe proposed a variable-aperture full-ring SPECT system using combined pixelated CZT and energy-optimized parallel-hole collimator modules and evaluated the performance of this scanner using relevant digital phantoms and MC simulations. Our studies demonstrated the potential of our new full-ring CZT-SPECT design, showing reduced acquisition time and improved sensitivity with acceptable CNR and spatial resolution.

We studied the diversity and regularity of FCV variations in two new feline calicivirus (FCV) isolates QD-7 and QD-164. We compared the genomes of these new strains with 39 from the NCBI database including isolates from China, United States, Germany, South Korea, the United Kingdom and Japan. The nucleotide sequence identities ranged from 75-88 % indicating a high degree of variability. These variations were not related to distributions of the virus by time of isolation and geographical location. Cats that were experimentally infected with the new isolate QD-164 showed typical clinical symptoms of sneezing, fever and conjunctivitis and all recovered within 30 days. In contrast, QD-7 infections were asymptomatic and the virus was cleared within 16 days. These results indicate that QD-7 and QD-164 were naturally attenuated strains. NNS mutations that are characteristic of highly virulent strains at positions 441-443 were absent from QD-7 while QD-164 possessed an N at position 442. This indicated that mutations in regions 441-443 may be linked to disease severity.

Persimmon ( Diospyros kaki L.) leaves are extensively used in Chinese medicine and are also excellent source of dietary polyphenols. Here we investigated the antiproliferative and pro-apoptotic activity of the total flavonoids extracted from persimmon leaves (FPL) in PC-3 cells. After treating cells with different concentration of FPL, Quercetin or Rutin for 24 h, MTT and flow cytometry were used to measure the cytotoxicity, apoptotic rate and cell cycle arrest. Compared with Quercetin and Rutin, FPL showed higher cytotoxicity at 12.5 and 25 μg/ml concentrations and also presented lower IC 50 in PC-3 cells. In addition, FPL induced PC-3 cells apoptosis by activation of oxidative stress, as detected by ROS, MDA, nitrite and iNOS activity, and increased mitochondrial membrane permeability. Morphological changes, inactivation of Bcl-2, upregulation of BAX, release of cytochrome c and activation of downstream apoptotic signaling in FPL-treated PC-3 cells also suggested apoptotic death. Meanwhile, FPL significantly inhibited migration of PC-3 cells. Therefore, FPL inhibited proliferation, migration and induced apoptosis of PC-3 cells by activation of oxidative stress and mitochondrial-related apoptosis.

This paper presents a unique preclinical positron emission tomography (PET) detector constructed with a monolithic scintillator ring (MSR) and two rings of silicon photomultipliers (SiPM). The inner diameter, outer diameter and length of the MSR were 48.5 mm, 58.5 mm, and 25.1 mm, respectively. The two SiPM rings, constructed with 46 SiPMs, were air-coupled to the two ends of the MSR detector. The center of gravity (COG) and artificial neural network (ANN) methods were adapted to decode the positions of the gamma interactions in the circumferential (θ) and axial (Z) directions, respectively. Collimating systems, consisting of a tungsten collimator and a high-precision displacement and rotating platform, were constructed to assess the decoding accuracies of the MSR detector in both θ and Z directions. The average intrinsic full-width half maximums (FWHMs) and mean absolute errors (MAEs) of the decoding accuracies were 0.94 mm and 0.33 mm in the circumferential direction, 2.45 mm and 1.08 mm in the axial direction. An energy resolution of 10.7% was measured at 511 keV. The scintillating photons generated by a pair of coincidence gamma photons overlap with each other, and cause circumferential parallax errors in the lines of response (LOR). The experimental results show that the average FWHM errors in the θ direction increased slightly from 0.94 mm to 1.14 mm when Δθ of the two single events was larger than 70°. The imaging performance of the MSR detector was also initially assessed with a Derenzo phantom filled with 18F-FDG. The rods with a diameter larger than 1.2 mm can be resolved. The energy resolutions were 12.3% at 511 keV (single events), and 11.4% at 1022 keV (coincidence events). We concluded that it is feasible to construct the high-performance preclinical PET scanners using one or multiple MSR detectors.

Increasing the image quality of positron emission tomography (PET) is an essential topic in the PET community. For instance, thin-pixelated crystals have been used to provide high spatial resolution images but at the cost of sensitivity and manufacture expense. In this paper, we proposed an approach to enhance the PET image resolution and noise property for PET scanners with large pixelated crystals. To address the problem of coarse blurred sinograms with large parallax errors associated with large crystals, we developed a data-driven, single-image super-resolution (SISR) method for sinograms, based on the novel deep residual convolutional neural network (CNN). Unlike the CNN-based SISR on natural images, periodically padded sinogram data and dedicated network architecture were used to make it more efficient for PET imaging. Moreover, we included the transfer learning scheme in the approach to process cases with poor labeling and small training data set. The approach was validated via analytically simulated data (with and without noise), Monte Carlo simulated data, and pre-clinical data. Using the proposed method, we could achieve comparable image resolution and better noise property with large crystals of bin sizes $4\times $ of thin crystals with a bin size from $1\times 1\,\,mm^{2}$ to $1.6\times 1.6\,\,mm^{2}$ . Our approach uses external PET data as the prior knowledge for training and does not require additional information during inference. Meanwhile, the method can be added into the normal PET imaging framework seamlessly, thus potentially finds its application in designing low-cost high-performance PET systems.

The future of Intelligent Transportation Systems (ITS) relies on a properly constructed Control Transportation System (CTS) based on a dynamically accurate localisation system. To ensure quality of the localisation system data-fusion algorithms are applied to enhance trueness and precision of the provided locations. But that quality is directly related to the accuracy of the Global Navigation Satellite System (GNSS) receiver. Nowadays Global Position System (GPS) is not the functional GNSS system over Asia. Even though the second generation of China’s BeiDou Navigation Satellite System (BDS), also known as COMPASS, is still under construction on a global coverage, it provides service since the beginning of 2013 to the Asia-Pacific region. Focusing on urban scenarios applications, this paper analyses the accuracy of BDS receivers to provide location for localisation systems in urban scenarios, comparing it with GPS and the combination of both in a Multi-GNSS system, using a Differential GNSS (DGNSS) as a reference for the accuracy results. From the accuracy limits results further reliability analysis by means of trueness and precision for tangential and perpendicular coordinates in the dynamic frame of vehicles were proposed. The results show that a circular error probable (CEP) approach is not a realistic representation of the dynamic behaviour of the receivers. So the new Mahalanobis Ellipses Filter (MEF) approach was tested and proven to be a better dynamic accuracy representation for land vehicles, making it the best approach to describe accuracy requirements for BDS-based urban land vehicle localisation systems for safety-relevant ITS.

Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) is a novel approach for performing liver resection, and the number of clinical applications of this technique has rapidly increased within recent years. ALPPS is important in patients who have insufficient residual liver volume and cannot undergo radical hepatic resection. The most common postoperative complications of ALPPS include biliary fistula and infection. To date, postoperative acute kidney injury following ALPPS has not been reported. The current study reports the case of a 63-year-old patient with hepatitis B-induced cirrhosis who underwent the first stage of ALPPS without completion of the second step. The patient developed postoperative acute kidney injury following ALPPS. The present case study suggests that the use of ALPPS in patients at risk of chronic renal damage should be approached with caution in order to avoid postoperative acute kidney injury. Furthermore, improvements in surgical techniques and skills of the surgeons performing the procedure are required to reduce the surgery duration and improve patient outcomes.

PURPOSE In brain imaging, the spherical PET system achieves the highest sensitivity when the solid angle is concerned. However, it is not practical. In this work, we designed an alternative sphere-like scanner, the dodecahedral scanner, which has a high sensitivity in imaging and a high feasibility to manufacture. We simulated this system and compared the performance with a few other dedicated brain PET systems. METHODS Monte Carlo simulations were conducted to generate data of the dedicated brain PET system with the dodecahedral geometry (11 regular pentagon detectors). The data were then reconstructed using the in-house developed software with the fully three-dimensional maximum-likelihood expectation maximization (3D-MLEM) algorithm. RESULTS Results show that the proposed system has a high-sensitivity distribution for the whole field of view (FOV). With a depth-of-interaction (DOI) resolution around 6.67 mm, the proposed system achieves the spatial resolution of 1.98 mm. Our simulation study also shows that the proposed system improves the image contrast and reduces noise compared with a few other dedicated brain PET systems. Finally, simulations with the Hoffman phantom show the potential application of the proposed system in clinical applications. CONCLUSIONS In conclusion, the proposed dodecahedral PET system is potential for widespread applications in high-sensitivity, high-resolution PET imaging, to lower the injected dose.

Rationale: Gallbladder perforation is a relatively uncommon complication of alcoholic liver cirrhosis and may happen with or without gallstones. Patient concerns: Here we report a 52-year-old male patient who was diagnosed as gallbladder perforation with chronic liver cirrhosis and asymptomatic gallstones. The patient was admitted with acute and severe abdominal pain during weight-bearing physical labor. He had a history of alcoholic liver cirrhosis but no chronic abdominal pain or gallstones. The patient presented with localized peritoneal irritation, and abdominal puncture showed non-clotting blood. A preliminary clinical diagnosis was made as hepatocellular carcinoma rupture based on imaging findings. However, this diagnosis changed to gangrenous cholecystitis with gallbladder perforation by the laparotomy examination. Diagnoses: He was diagnosed with gangrenous cholecystitis with gallbladder perforation. Interventions and outcomes: The patient performed well postoperatively. Lessons: This case suggests that gallbladder perforation should be considered as a potential cause of acute abdominal pain even without evidence of gallstones. Early examination with a laparotomy examination can help achieve a timely diagnosis.