Noise reduction performance of a deep learning-based reconstruction in brain computed tomography images acquired with organ-based tube current modulation.

We aimed to evaluate the image quality of brain computed tomography (CT) images reconstructed using deep learning-based reconstruction (DLR) in organ-based tube current modulation (OB-TCM) acquisition. An anthropomorphic head phantom and a cylindrical low-contrast phantom were scanned at the standard dose level for adult brain CT in axial volume acquisition without OB-TCM. Moreover, image acquisition with OB-TCM was performed. The radiation dose on the eye lens was measured using a scintillation fibre-optic dosimeter placed on the anthropomorphic phantom's eye surface. The task transfer function (TTF), contrast-to-noise ratio (CNR), and low-contrast object specific CNR obtained from low-contrast phantom images reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR), and two types of DLR (DLRCTA and DLRLCD) were compared. In result, OB-TCM achieved a 32.5% dose reduction in the eye lens. Although HIR, DLRCTA, and DLRLCD showed lower TTF than FBP, the difference in TTF at the highest contributing spatial frequency corresponding to the contrast rod diameter was < 10%. Despite the OB-TCM acquisition, DLRCTA and DLRLCD achieved significantly lower noise and a higher CNR than FBP without OB-TCM (p < 0.05). However, low-contrast object specific CNR was equivalent among all reconstruction methods for the objective diameter of 5 mm and slightly improved in DLRLCD for the objective diameter of 7 mm. DLR with OB-TCM acquisition enabled dose reduction for the eye lens and high CNR image appearance, whereas the low contrast detectability evaluated by low-contrast object specific CNR did not always improve.

Image quality comparison of a nonlinear image-based noise reduction technique with a hybrid-type iterative reconstruction for pediatric computed tomography.

PURPOSE: To compare computed tomography (CT) image properties between a vendor-independent image-based noise reduction technique, Image-space Noise Reduction (iNoir) and a hybrid-type iterative reconstruction technique, Adaptive Statistical Iterative Reconstruction (ASIR). METHODS: A cylindrical water phantom, corresponding to pediatric body size, containing soft-tissue-equivalent rod and 12-mg iodine/ml rod was scanned at size-specific dose estimates of 8.4 and 16.7 mGy. For assessments of image quality and noise texture change, task-based system performance function (SPF) and peak frequency difference (PFD) were compared, respectively, among filtered back projection (FBP), IR image with 50%-blending rate (50%ASIR), 100%ASIR, 50%iNoir, and 100%iNoir. Human observer test for pediatric CT images was performed by radiologists. RESULTS: For the soft-tissue contrast, SPF2 of 100%iNoir was the highest. The average SPF2 between 0.1 and 0.5 cycles/mm for 100%iNoir increased by approximately 70% compared with FBP, while ASIR indicted slight increases in the frequency region of >0.2 cycles/mm. For the iodine contrast, 100%iNoir indicated highest values at the spatial frequencies corresponding pediatric artery diameters. The PFDs of iNoir were negligible and lower than that of ASIR. The results of human observer test supported results of SPF2 and PFD. CONCLUSIONS: Compared with ASIR, iNoir provided better image quality for pediatric abdominal CT without compromising noise texture change.

Radiation dose reduction to the eye lens in head CT using tungsten functional paper and organ-based tube current modulation.

PURPOSE: We investigated whether a tungsten functional paper (TFP) shield and/or organ-based tube current modulation (TCM) can reduce the dose to the eye lens. MATERIALS AND METHODS: All scans were performed using our routine head examination protocol (spiral acquisition, 120 kVp, noise Index 3.5) with an anthropomorphic head phantom. The dose reduction rate was measured by the following methods with a scintillation fiber optic dosimeter: (a) without any dose reduction techniques (Original scan), (b) TFP shield, (c) TCM, and (d) TFP shield plus TCM. Image noise and CT number were obtained and compared between the three groups. In addition, image noise in method (d) was measured with varying distances between the TFP shield and eye lens. RESULTS: The reduction rates using TFP shield, TCM, and TFP shield plus TCM compared with those for the Original scan were 17.8 %, 13.6 %, and 27.7 %, respectively. Image noise (mean ± standard deviation) in the anterior region for the Original scan, TFP shield, TCM, and TFP shield plus TCM were 4.1 ± 0.2, 4.6 ± 0.2, 4.4 ± 0.3, and 5.0 ± 0.2, while the CT numbers were 19.3 ± 0.8, 23.8 ± 0.8, 19.6 ± 0.8, and 24.1 ± 0.8, respectively. Increasing the distance between the TFP and the eye significantly decreased the CT number when using TFP shield plus TCM (p < .05). CONCLUSION: TFP shield plus TCM reduced the dose to the eye lens in head CT while maintaining image quality with an air gap between the TFP and skin surface.

Identification of elemental weight fraction and mass density of humanoid tissue-equivalent materials using dual energy computed tomography.

The purpose of this study was to obtain the fraction by weight of the elemental composition and mass density of a humanoid tissue phantom that includes lung tissue, soft tissue, and bone tissue, by using dual energy computed tomography (DECT). The fraction by weight and the mass density for tissue-equivalent materials were calculated by means of a least-squares method with a linear attenuation coefficient, using monochromatic photon energies of 10-140keV, as obtained from DECT. The accuracy of calculated values for the fractions by weight of H (hydrogen), C (carbon), N (nitrogen), and O (oxygen) as verified by comparing the values with those that were analyzed using the combustion technique. The fraction by weight for other elements was confirmed by comparing with the analyzed values by means of energy dispersive photon spectroscopy. The calculated mass densities for each tissue were compared with those that were obtained by dividing the weight by volume. The calculated values of the fraction by weight that were obtained by means of DECT had differences of 1.9%, 9.2%, 6.6%, 7.8%, 0.8%, and 0.2% at a maximum for H, C, N, O, P (phosphorus), and Ca (calcium), respectively, from the reference values analyzed by the combustion technique and energy dispersive photon spectroscopy. The difference in the mass density for tissue was 0.011g/cm3 at a maximum. This study demonstrated the fraction by weight and the mass density of the humanoid tissue-equivalent materials that were calculated by means of DECT were expected high accuracy.

Complexes of Eu(iii)(hfa)3 with a planar chiral P(iii) ligand (Phanephos): solvent-sensitive sign inversion of circularly polarised luminescence.

Complexes of Eu(iii)(hfa)3 with a C2-symmetric planar P(iii) ligand exhibited intense circularly polarised luminescence (CPL) due to 5D0 → 7F1 and 5D0 → 7F2 transitions, with the signs and shapes of CPL signals depending on the choice of solvent (acetone or chloroform).

Putative host cell receptor for fowl adenovirus detected in gizzard.

This work was done to identify a fowl adenovirus (FAV) binding protein in the gizzard, a known target organ for certain strains of FAV serotype 1. By using a virus overlay protein binding assay (VOPBA), a putative FAV binding protein of approximately 200 kDa expressed in the gizzard was detected.