Phantom Region Research Articles

Dynamical study of NTADE and SMHDE models within Rastall gravity

This paper is mainly focused to investigate the cosmological implications of Rastall gravity with the help of two dark energy models, i.e., new Tsallis agegraphic dark energy (NTADE) and Sharma-Mittal holographic dark energy (SMHDE). The background of flat FLRW space–time is being considered to develop the dynamical system of equations. To check the viability of these models and to distinguish them, we develop some important cosmological parameters. By constraining the involved model parameters, it is observed that the equation of state (EoS) parameter for the NTADE model lies in the phantom region whereas, for SMHDE, it shows quintom as well as quintessence regions depending on the values of model parameter δ . The deceleration parameter shows the phase transition from decelerating to the accelerating phase for both models. The ω D − ω D ′ pair shows freezing and thawing regions for NTADE, and the freezing region for SMHDE. The pair ( j , s ) for SMHDE indicates a rich behavior as it shows different DE eras, a phantom, the quintessence as well as Chaplygin gas but the NTADE model shows Chaplygin gas behavior only. We conclude that SMHDE is a more efficient model than the NTADE model because it approaches Λ CDM limit and the results for this model lie in a stable region as shown by graphical analysis of the square speed of sound. • This paper investigates the cosmological implications of Rastall gravity via two dark energy models, new Tsallis agegraphic dark energy (NTADE) and Sharma–Mittal holographic dark energy (SMHDE). • The background of flat FLRW space-time is being considered to develop the dynamical system of equations. To check these models’ viability and distinguish them, we develop some important cosmological parameters. • It is observed that the equation of state parameter for the NTADE model lies in the phantom region whereas, for SMHDE, it shows quintom as well as quintessence regions depending on the values of model parameter δ . • The deceleration parameter shows the phase transition from decelerating to accelerating one. • The ω D – ω D ′ pair shows freezing and thawing regions for NTADE and the freezing region for SMHDE. • The (j,s) pair for SMHDE indicates different DE eras; phantom, quintessence, and Chaplygin gas but for the NTADE model, it shows Chaplygin gas behavior only. • We concluded that SMHDE is an efficient model than the NTADE model as Λ CDM limit is approachable in this case and its results found to be stable region.

Tsallis holographic dark energy scenario in viscous f(Q) gravity with tachyon field

This study investigates a bulk viscous fluid anisotropic cosmological model with [Formula: see text] gravity. Here, [Formula: see text] stands for the nonmetricity factor that drives gravitational interaction. We reconstructed the associated parameters with Tsallis holographic dark energy (THDE). We have solved the modified Einstein’s field equations by considering the bulk viscosity factor [Formula: see text]. Under the viscous and nonviscous THDE frameworks, we have obtained the expressions of [Formula: see text] using the power-law form of expansion. We have investigated the nature of various energy conditions for the stability analysis. The positive behavior of DEC and WEC indicates the model’s validation; on the other hand, SEC is violating, indicating the universe’s accelerated expansion. We have also investigated the reconstructed EoS parameter [Formula: see text] for bulk viscosity and obtained the one that lies in both quintessence and phantom regions. We also discussed the correspondence of the tachyon scalar field with THDE energy density in [Formula: see text] gravity. This correspondence permits the reconstruction of potentials and dynamics for scalar field models describing accelerated expansion.

Incorporation of micro-CT-based detailed bone models into ICRP adult mesh-type reference computational phantoms

Objective. The red bone marrow (RBM) and bone endosteum (BE), which are required for effective dose calculation, are macroscopically modeled in the reference phantoms of the international commission on radiological protection (ICRP) due to their microscopic and complex histology. In the present study, the detailed bone models were developed to simplify the dose calculation process for skeletal dosimetry. Approach. The detailed bone models were developed based on the bone models developed at the University of Florida. A new method was used to update the definition of BE region by storing the BE location indices using virtual sub-voxels. The detailed bone models were then installed in the spongiosa regions of the ICRP mesh-type reference computational phantoms (MRCPs) via the parallel geometry feature of the Geant4 code. Main results. Comparing the results between the detailed-bone-installed MRCPs and the original MRCPs with the absorbed dose to spongiosa and fluence-to-dose response function (DRF)-based methods, the DRF-based method showed much smaller but still significant differences. Compared with the values given in ICRP Publications 116 and 133, the differences were very large (i.e. several orders of magnitudes), due mainly to the anatomical improvement of the skeletal system in the MRCPs; that is, spongiosa and medullary cavity are fully enclosed by cortical bone in the MRCPs but not in the ICRP-110 phantoms. Significance. The detailed bone models enable the direct calculation of the absorbed doses to the RBM and BE, simplifying the dose calculation process and potentially improving the consistency and accuracy of skeletal dosimetry.

Progress eras of the universe with spacetime dimensions

In this study, we examine on the expansion history of the universe from the inflationary era to the late-time phantom era in the framework of higher dimensional F(R) gravity. Following the unified first law of thermodynamics method, we find a general entropy expression of the gravity theory for the apparent horizon of the universe. Based on the assumption that the dark energy mystery is closely related to the dimensions of spacetime, we research the progress eras of the universe according to the opening of the space-time dimensionality. In a more general framework, we consider the space time manifold as n+1-dimensional spherically symmetric form and discuss the phases of the universe through the validity of entropy. During the inflation, we obtain a 10 dimensional spacetime model which is estimated by the string theory. However, while in the radiation era it is obtained 5 dimensional Kaluza-Klein spacetime, in the dust era 4 spacetime dimensions within the framework of entropy keep standing. At small curvatures of spacetime, a process occurs in which a metric deformation is observed with the negative value of the equation of the state (EoS) parameter, w<−13. This leads to the release of dark energy from the extra dimensions resulting in a 10 dimensional universe. Since the currently observable universe is in four dimensional spacetime form, this fact indicates that the universe needs to pass into a new phase. Hence, de Sitter phase w=−1 of the universe gives 10 dimensional spherically symmetrical spacetime, but here the deformation disappears. Therewithal, we find that 4 dimensional universe model emerges in the phantom region without disturbing the spherical and symmetrical structure of the universe. This means that the late-time accelerated expansion of the universe could be due to dark energy emanating from the extra dimensions.

A multi-modality physical phantom for mimicking tumor heterogeneity patterns in PET/CT and PET/MRI.

BackgroundHybrid imaging (e.g., positron emission tomography [PET]/computed tomography [CT], PET/magnetic resonance imaging [MRI]) helps one to visualize and quantify morphological and physiological tumor characteristics in a single study. The noninvasive characterization of tumor heterogeneity is essential for grading, treatment planning, and following‐up oncological patients. However, conventional (CONV) image‐based parameters, such as tumor diameter, tumor volume, and radiotracer activity uptake, are insufficient to describe tumor heterogeneities. Here, radiomics shows promise for a better characterization of tumors. Nevertheless, the validation of such methods demands imaging objects capable of reflecting heterogeneities in multi‐modality imaging. We propose a phantom to simulate tumor heterogeneity repeatably in PET, CT, and MRI.MethodsThe phantom consists of three 50‐ml plastic tubes filled partially with acrylic spheres of S1: 1.6 mm, S2: 50%(1.6 mm)/50%(6.3 mm), or S3: 6.3‐mm diameter. The spheres were fixed to the bottom of each tube by a plastic grid, yielding one sphere free homogeneous region and one heterogeneous (S1, S2, or S3) region per tube. A 3‐tube phantom and its replica were filled with a fluorodeoxyglucose (18F) solution for test–retest measurements in a PET/CT Siemens TPTV and a PET/MR Siemens Biograph mMR system. A number of 42 radiomic features (10 first order and 32 texture features) were calculated for each phantom region and imaging modality. Radiomic features stability was evaluated through coefficients of variation (COV) across phantoms and scans for PET, CT, and MRI. Further, the Wilcoxon test was used to assess the capability of stable features to discriminate the simulated phantom regions.ResultsThe different patterns (S1–S3) did present visible heterogeneity in all imaging modalities. However, only for CT and MRI, a clear visual difference was present between the different patterns. Across all phantom regions in PET, CT, and MR images, 10, 16, and 21 features out of 42 evaluated features in total had a COV of 10% or less. In particular, CONV, histogram, and gray‐level run length matrix features showed high repeatability for all the phantom regions and imaging modalities. Several of repeatable texture features allowed the image‐based discrimination of the different phantom regions (p < 0.05). However, depending on the feature, different pattern discrimination capabilities were found for the different imaging modalities.ConclusionThe proposed phantom appears suitable for simulating heterogeneities in PET, CT, and MRI. We demonstrate that it is possible to select radiomic features for the readout of the phantom. Most of these features had been shown to be relevant in previous clinical studies.

NEMA characterization of the SAFIR prototype PET insert

BackgroundThe SAFIR prototype insert is a preclinical Positron Emission Tomography (PET) scanner built to acquire dynamic images simultaneously with a 7 T Bruker Magnetic Resonance Imaging (MRI) scanner. The insert is designed to perform with an excellent coincidence resolving time of 194 ps Full Width Half Maximum (FWHM) and an energy resolution of 13.8% FWHM. These properties enable it to acquire precise quantitative images at activities as high as 500 MBq suitable for studying fast biological processes within short time frames (< 5 s). In this study, the performance of the SAFIR prototype insert is evaluated according to the NEMA NU 4-2008 standard while the insert is inside the MRI without acquiring MRI data.ResultsApplying an energy window of 391–601 keV and a coincidence time window of 500 ps the following results are achieved. The average spatial resolution at 5 mm radial offset is 2.6 mm FWHM when using the Filtered Backprojection 3D Reprojection (FBP3DRP) reconstruction method, improving to 1.2 mm when using the Maximum Likelihood Expectation Maximization (MLEM) method. The peak sensitivity at the center of the scanner is 1.06%. The Noise Equivalent count Rate (NECR) is 799 kcps at the highest measured activity of 537 MBq for the mouse phantom and 121 kcps at the highest measured activity of 624 MBq for the rat phantom. The NECR peak is not yet reached for any of the measurements. The scatter fractions are 10.9% and 17.8% for the mouse and rat phantoms, respectively. The uniform region of the image quality phantom has a 3.0% STD, with a 4.6% deviation from the expected number of counts per voxel. The spill-over ratios for the water and air chambers are 0.18 and 0.17, respectively.ConclusionsThe results satisfy all the requirements initially considered for the insert, proving that the SAFIR prototype insert can obtain dynamic images of small rodents at high activities (sim 500 MBq) with a high sensitivity and an excellent count-rate performance.

FRW cosmological models with Barrow holographic dark energy in Brans–Dicke theory

In this paper, we have generalized the behaviors of transit cosmological model under the observational data with Barrow holographic dark energy. We consider the scale factor field as [Formula: see text] to get exact solutions for the field equations in a non-flat FRW universe in Brans–Dicke theory. The values of the model parameters [Formula: see text] and [Formula: see text] are obtained by best fitting of 46 observational Hubble data (OHD) points in the range [Formula: see text]. The derived model exhibits a transition scenario for open, flat and closed universe. The EoS parameter shows a quintom-like behavior, lies both quintessence ([Formula: see text]) and phantom ([Formula: see text]) regions and crosses the phantom divide. The matter and dark energy density parameters [Formula: see text], scalar field [Formula: see text] and other cosmological parameters provide the results consistent with the recent observational datasets. Some other physical and geometrical behaviors of BHDE are also described and the satisfactory behaviors are found with current observations (OHD+JLA).

Deep-learning-based projection-domain breast thickness estimation for shape-prior iterative image reconstruction in digital breast tomosynthesis.

Digital breast tomosynthesis (DBT) is a technique that can overcome the shortcomings of conventional X-ray mammography and can be effective for the early screening of breast cancer. The compression of the breast is essential during the DBT imaging. However, since the periphery of the breast cannot be compressed to a constant value, nonuniformity of thickness and in-plane shape variation happen. These cause inconvenience in diagnosis, scatter correction, and breast density estimation. In this study, we propose a deep-learning-based methodology for projection-domain breast thickness estimation and demonstrate a shape-prior iterative DBT image reconstruction. We prepared the Euclidean distance map, the thickness map, and the thickness corrected image of the simulated breast projections for thickness and shape estimation. Each pixel of the Euclidean distance map denotes a distance to the closest skin-line. The thickness map is defined as a conceptual projection of ideal breast support that differentiates the inner and outer regions of the breast phantom. The thickness projection map thus represents the X-ray path lengths of a homogeneous breast phantom. We generated the thickness corrected image by dividing the projection image by the thickness map in a pixel-wise manner. We developed a convolutional neural network for thickness estimation and correction. The network utilizes a projection image and a Euclidean distance image together as a dual input. An estimated breast thickness map is then used for constructing the breast shape mask by use of the discrete algebraic reconstruction technique. The proposed network effectively corrected the breast thickness in various simulation situations. Low normalized root-mean-squared error (1.976%) and high structural similarity (99.997%) indicated a good agreement between the network-generated thickness corrected image and the ground truth image. Compared to the existing methods and simple single-input network, the proposed method showed outperformance in breast thickness estimation and accordingly in breast shape recovery for various numerical phantoms without provoking any significant artifact. We have demonstrated that the uniformity of voxel value has improved by the inclusion of a shape prior for the iterative DBT reconstruction. We presented a novel deep-learning-based breast thickness correction and a shape reconstruction method. This approach to estimating the true thickness map and the shape of the breast undergoing compression can benefit various fields such as improvement of diagnostic breast images, scatter correction, material decomposition, and breast density estimation.

Reconstruction of Preclinical PET Images via Chebyshev Polynomial Approximation of the Sinogram

Over the last decades, there has been an increasing interest in dedicated preclinical imaging modalities for research in biomedicine. Especially in the case of positron emission tomography (PET), reconstructed images provide useful information of the morphology and function of an internal organ. PET data, stored as sinograms, involve the Radon transform of the image under investigation. The analytical approach to PET image reconstruction incorporates the derivative of the Hilbert transform of the sinogram. In this direction, in the present work we present a novel numerical algorithm for the inversion of the Radon transform based on Chebyshev polynomials of the first kind. By employing these polynomials, the computation of the derivative of the Hilbert transform of the sinogram is significantly simplified. Extending the mathematical setting of previous research based on Chebyshev polynomials, we are able to efficiently apply our new Chebyshev inversion scheme for the case of analytic preclinical PET image reconstruction. We evaluated our reconstruction algorithm on projection data from a small-animal image quality (IQ) simulated phantom study, in accordance with the NEMA NU 4-2008 standards protocol. In particular, we quantified our reconstructions via the image quality metrics of percentage standard deviation, recovery coefficient, and spill-over ratio. The projection data employed were acquired for three different Poisson noise levels: 100% (NL1), 50% (NL2), and 20% (NL3) of the total counts, respectively. In the uniform region of the IQ phantom, Chebyshev reconstructions were consistently improved over filtered backprojection (FBP), in terms of percentage standard deviation (up to 29% lower, depending on the noise level). For all rods, we measured the contrast-to-noise-ratio, indicating an improvement of up to 68% depending on the noise level. In order to compare our reconstruction method with FBP, at equal noise levels, plots of recovery coefficient and spill-over ratio as functions of the percentage standard deviation were generated, after smoothing the NL3 reconstructions with three different Gaussian filters. When post-smoothing was applied, Chebyshev demonstrated recovery coefficient values up to 14% and 42% higher, for rods 1–3 mm and 4–5 mm, respectively, compared to FBP, depending on the smoothing sigma values. Our results indicate that our Chebyshev-based analytic reconstruction method may provide PET reconstructions that are comparable to FBP, thus yielding a good alternative to standard analytic preclinical PET reconstruction methods.

Interacting Tsallis agegraphic dark energy in DGP braneworld cosmology

The purpose of this paper is to study the Tsallis agegraphic dark energy with an interaction term between dark energy and dark matter in the DGP brane-world scenario. For this, we assume some initial conditions to obtain the dark energy density, deceleration, dark energy EoS, and total EoS parameters. Then, we analyze the statefinder parameters, $\omega'{}_{DE}-\omega_{DE}$ plots, and classical stability features of the model. The results state that the deceleration parameter provides the phase transition from decelerated to accelerated phase. The $\omega_{DE}$ graphs show the phantom behavior, while the $\omega_{tot}$ exhibits the quintessence and phantom during the evolution of the Universe. Following the graphs, the Statefinder analysis shows the quintessence behavior of the model for the past and present. However, it tends to the $\Lambda CDM$ in the following era. The $\omega'{}_{DE}-\omega_{DE}$ plot indicates the thawing or freezing area depending on the type of era and different values of $b^{2}$, $\delta$, and $m$. By the square of the sound speed, we see the model is stable in the past, stable or unstable at the current time, and unstable in the future for selected values of $b^{2}$, $\delta$, and $m$. To test the model, we use the recent Hubble data. We also employ Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) to compare the model with the $\Lambda CDM$ as the reference model. In addition, we test the model using the $H-z$ plot, and we see a turning point in the future time. The results from the best fit values for the $\omega_{tot}$ plot emphasize that the Universe is in the quintessence region in the current time. It will enter the phantom phase, and then it will approach the $\Lambda$ state in the future. But, the $\omega_{DE}$ always stays on the phantom region. The model is unstable in the present and progressive era.

A reconstruction approach for proton computed tomography by modeling the integral depth dose of the scanning proton pencil beam.

To present a proton computed tomography (pCT) reconstruction approach that models the integral depth dose (IDD) of the clinical scanning proton beam into beamlets. Using a multilayer ionization chamber (MLIC) as the imager, the proposed pCT system and the reconstruction approach can minimize extra ambient neutron dose and simplify the beamline design by eliminating an additional collimator to confine the proton beam. Monte Carlo simulation was applied to digitally simulate the IDDs of the exiting proton beams detected by the MLIC. A forward model was developed to model each IDD into a weighted sum of percentage depth doses of the constituent beamlets separated laterally by 1mm. The water equivalent path lengths (WEPLs) of the beamlets were determined by iteratively minimizing the squared L2-norm between the forward projected and simulated IDDs. The final WEPL values were reconstructed to pCT images, that is, proton stopping power ratio (SPR) maps, through simultaneous algebraic reconstruction technique with total variation regularization. The reconstruction process was tested with a digital cylindrical water-based phantom and an ICRP adult reference computational phantom. The mean of SPR within regions of interest (ROIs) and the WEPL along a 4mm-wide beam ( ) were compared with the reference values. The spatial resolution was analyzed at the edge of a cortical insert of the cylindrical phantom. The percentage deviations from reference SPR were within±1% in all selected ROIs. The mean absolute error of the reconstructed SPR was 0.33%, 0.19%, and 0.27% for the cylindrical phantom, the adult phantom at the head and lung region, respectively. The corresponding percentage deviations from reference were 0.48±0.64%, 0.28±0.48%, and 0.22±0.49%. The full width at half maximum of the line spread function (LSF) derived from the radial edge spread function (ESF) of a cortical insert was 0.13cm. The frequency at 10% of the modulation transfer function (MTF) was 6.38cm-1 . The mean signal-to-noise ratio (SNR) of all the inserts was 2.45. The mean imaging dose was 0.29 and 0.25cGy at the head and lung region of the adult phantom, respectively. A new pCT reconstruction approach was developed by modeling the IDDs of the uncollimated scanning proton beams in the pencil beam geometry. SPR accuracy within±1%, spatial resolution of better than 2mm at 10% MTF, and imaging dose at the magnitude of mGy were achieved. Potential side effects caused by neutron dose were eliminated by removing the extra beam collimator.

Classification of Circular Equatorial Orbits around Regular Rotating Black Holes and Solitons with the de Sitter/ Phantom Interiors

We study the basic properties of the circular equatorial orbits for the regular axially symmetric solutions, obtained with using the Gürses–Gürsey formalism which includes the Newman–Janis algorithm, from regular spherically symmetric metrics of the Kerr–Schild class specified by Ttt=Trr. Solutions of this class describe regular rotating black holes and spinning solitons replacing naked singularities. All these objects have the interior de Sitter equatorial disk, and can have two kinds of interiors determined by the energy conditions. One of them contains an additional interior de Sitter vacuum S-surface with the de Sitter disk as a bridge, whose internal cavities are filled with a phantom fluid. We study in detail the innermost equatorial circular orbits and show that in the field of spinning solitons, the innermost orbits exist within ergoregions related to phantom regions. We show also that around spinning solitons there can exist four corotating light rings and around a regular black hole, one corotating light ring, which is stable for a certain class of black holes. For all objects there exists one counterrotating light ring.

A dosimetric comparison of CT- and photogrammetry- generated 3D printed HDR brachytherapy surface applicators.

In this study, we investigate whether an acceptable dosimetric plan can be obtained for a brachytherapy surface applicator designed using photogrammetry and compare the plan quality to a CT-derived applicator. The nose region of a RANDO anthropomorphic phantom was selected as the treatment site due to its high curvature. Photographs were captured using a Nikon D5600 DSLR camera and reconstructed using Agisoft Metashape while CT data was obtained using a Canon Aquillion scanner. Virtual surface applicators were designed in Blender and printed with PLA plastic. Treatment plans with a prescription dose of 3.85Gy × 10 fractions with 100% dose to PTV on the bridge of the nose at 2mm depth were generated separately using AcurosBV in the Varian BrachyVision TPS. PTV D98%, D90% and V100%, and OAR D0.1cc, D2cc and V50% dose metrics and dwell times were evaluated, with the applicator fit assessed by air-gap volume measurements. Both types of surface applicators were printed with minimal defects and visually fitted well to the target area. The measured air-gap volume between the photogrammetry applicator and phantom surface was 44% larger than the CT-designed applicator, with a mean air gap thickness of 3.24 and 2.88mm, respectively. The largest difference in the dose metric observed for the PTV and OAR was the PTV V100% of - 1.27% and skin D0.1cc of - 0.28%. PTV D98% and D90% and OAR D2cc and V50% for the photogrammetry based plan were all within 0.5% of the CT based plan. Total dwell times were also within 5%. A 3D printed surface applicator for the nose was successfully constructed using photogrammetry techniques. Although it produced a larger air gap between the surface applicator and phantom surface, a clinically acceptable dose plan was created with similar PTV and OAR dose metrics to the CT-designed applicator. Additional future work is required to comprehensively evaluate its suitability in a clinically environment.

Suitability Assessment of an Indigenous Heterogeneous Thoracic Phantom for Patient-Specific Quality Assurance in Radiotherapy.

Objective: Patient-specific quality assurance (PSQA) assumes a vital role in precise and accurate radiation delivery to cancer patients. Since the patient body comprises heterogeneous media, the present study aimed to fabricate a heterogeneous thoracic phantom for PSQA. Materials and Methods: Heterogeneous thoracic (HT) phantom was fabricated using rib cage made up of bone equivalent material, kail-wood to mimic lungs and wax to mimic the various body parts. The physical density of all these materials used in phantom fabrication was measured and compared with that of the corresponding part of the actual human thorax. One beam was planned on the computed tomography (CT) images of the phantom and actual patient thorax region. Dose distribution in both the plans was measured and analyzed. Results: The estimated densities of heart, lung, ribs, scapula, spine, and chest wall tissues were 0.804 ± 0.007, 0.186 ± 0.010, 1.796 ± 0.061, 2.017 ± 0.026, 2.106 ± 0.029 and 0.739 ± 0.028 respectively in case of HT phantom while 1.038 ± 0.010, 0.199 ± 0.031, 1.715 ± 0.040, 2.006 ± 0.019, 1.929 ± 0.065 and 0.816 ± 0.028 g/cc, respectively in case of actual human thorax region.The depths of isodose curves in HT phantom were also comparable to the isodose curve’s depths in real patient. The PSQA results were within ± 3% for flat beam (FB) and flattening filtered free beam (FFFB) of 6 megavolts (MV) energy.Conclusion: The density and the dose distribution pattern in the HT phantom were similar to that in the actual human thorax region. Thus, fabricated HT phantom can be utilized for radiation dosimetry in thoracic cancer patients. The materials used to develop HT phantom are easily available in the market at an affordable price and easy to craft.

Study of the phantom size and ferromagnetic core of Ni-Cu alloy on the amount of induction heating in the Thermotherapy process by Comsol Multyphysics Software

Nickel-copper ferromagnetic core is used for interstitial local thermotherapy techniques to treat a deep-seated tumors such as brain tumors and prostatic tumors. In the present study, the effective parameters on the amount of induction heating in the ferromagnetic core and determining the optimal conditions before performing laboratory processes was investigated by the Comsol Multiphysics 5.4 software. The model consisted of a single Nickel-Copper ferromagnetic core(70.4-29.6;wt%) in the two different size that placed in the central region of a cylindrical water phantom with different radius between 20 mm up to 60 mm. For the study of the thermal distribution due to the electromagnetic induction was used from a finite-element analysis method. The temperature profiles of the ferromagnetic core in the electromagnetic field with a frequency of 75- 350 kHz and the magnetic field of strength (H0) with 200-500 Oe up to 30 minutes showed the possibility of temperature control at the thermo-seed for producing the desired temperature in the thermotherapy process. The decreased phantom radius, as well as increase in the volume of the ferromagnetic core led to a rise in the induction temperature of the core due to the increase in the amount of induced field at the center of the phantom in the constant current and frequency. The results showed that the induced temperature in the core was increased due to the rise of the magnetic field in the fixed frequency or the increase of the frequency in the fixed magnetic field.type, which is within most of us interested.

A size-adaptive 32-channel array coil for awake infant neuroimaging at 3Tesla MRI.

Functional magnetic resonance imaging (fMRI) during infancy poses challenges due to practical, methodological, and analytical considerations. The aim of this study was to implement a hardware-related approach to increase subject compliance for fMRI involving awake infants. To accomplish this, we designed, constructed, and evaluated an adaptive 32-channel array coil. To allow imaging with a close-fitting head array coil for infants aged 1-18 months, an adjustable head coil concept was developed. The coil setup facilitates a half-seated scanning position to improve the infant's overall scan compliance. Earmuff compartments are integrated directly into the coil housing to enable the usage of sound protection without losing a snug fit of the coil around the infant's head. The constructed array coil was evaluated from phantom data using bench-level metrics, signal-to-noise ratio (SNR) performances, and accelerated imaging capabilities for both in-plane and simultaneous multislice (SMS) reconstruction methodologies. Furthermore, preliminary fMRI data were acquired to evaluate the in vivo coil performance. Phantom data showed a 2.7-fold SNR increase on average when compared with a commercially available 32-channel head coil. At the center and periphery regions of the infant head phantom, the SNR gains were measured to be 1.25-fold and 3-fold, respectively. The infant coil further showed favorable encoding capabilities for undersampled k-space reconstruction methods and SMS techniques. An infant-friendly head coil array was developed to improve sensitivity, spatial resolution, accelerated encoding, motion insensitivity, and subject tolerance in pediatric MRI. The adaptive 32-channel array coil is well-suited for fMRI acquisitions in awake infants.

Real-Time Visualization of a Focused Ultrasound Beam Using Ultrasonic Backscatter.

Focused ultrasound (FUS) therapies induce therapeutic effects in localized tissues using either temperature elevations or mechanical stresses caused by an ultrasound wave. During an FUS therapy, it is crucial to continuously monitor the position of the FUS beam in order to correct for tissue motion and keep the focus within the target region. Toward the goal of achieving real-time monitoring for FUS therapies, we have developed a method for the real-time visualization of an FUS beam using ultrasonic backscatter. The intensity field of an FUS beam was reconstructed using backscatter from an FUS pulse received by an imaging array and then overlaid onto a B-mode image captured using the same imaging array. The FUS beam visualization allows one to monitor the position and extent of the FUS beam in the context of the surrounding medium. Variations in the scattering properties of the medium were corrected in the FUS beam reconstruction by normalizing based on the echogenicity of the coaligned B-mode image. On average, normalizing by echogenicity reduced the mean square error between FUS beam reconstructions in nonhomogeneous regions of a phantom and baseline homogeneous regions by 21.61. FUS beam visualizations were achieved, using a single diagnostic imaging array as both an FUS source and an imaging probe, in a tissue-mimicking phantom and a rat tumor in vivo with a frame rate of 25–30 frames/s.

Performance Evaluation of SimPET-X, a PET Insert for Simultaneous Mouse Total-Body PET/MR Imaging.

In this study, a small animal PET insert (SimPET-X, Brightonix Imaging Inc.) for simultaneous PET/MR imaging studies is presented. This insert covers an 11-cm-long axial field-of-view (FOV) and enables imaging of mouse total-bodies and rat heads. SimPET-X comprises 16 detector modules to yield a ring diameter of 63 mm and an axial FOV of 110 mm. The detector module supports four detector blocks, each comprising two 4 × 4 SiPM arrays coupled with a 20 × 9 array of LSO crystals (1.2 × 1.2 × 10 mm3). The physical characteristics of SimPET-X were measured in accordance with the NEMA NU4-2008 standard protocol. In addition, we assessed the compatibility of SimPET-X with a small animal-dedicated MRI (M7, Aspect Imaging) and conducted phantom and animal studies. The radial spatial resolutions at the center based on 3D OSEM without and with the warm background were 0.73 mm and 0.99 mm, respectively. The absolute peak sensitivity of the system was 10.44% with an energy window of 100-900 keV and 8.27% with an energy window of 250-750 keV. The peak NECR and scatter fraction for the mouse phantom were 348 kcps at 26.2 MBq and 22.1% with an energy window of 250-750 keV, respectively. The standard deviation of pixel value in the uniform region of an NEMA IQ phantom was 4.57%. The spillover ratios for air- and water-filled chambers were 9.0% and 11.0%, respectively. In the hot-rod phantom image reconstructed using 3D OSEM-PSF, all small rods were resolved owing to the high spatial resolution of the SimPET-X system. There was no notable interference between SimPET-X and M7 MRI. SimPET-X provided high-quality mouse images with superior spatial resolution, sensitivity, and counting rate performance. SimPET-X yielded a remarkably improved sensitivity and NECR compared with SimPETTM.

Automated segmentation of an intensity calibration phantom in clinical CT images using a convolutional neural network.

In quantitative computed tomography (CT), manual selection of the intensity calibration phantom's region of interest is necessary for calculating density (mg/cm3) from the radiodensity values (Hounsfield units: HU). However, as this manual process requires effort and time, the purposes of this study were to develop a system that applies a convolutional neural network (CNN) to automatically segment intensity calibration phantom regions in CT images and to test the system in a large cohort to evaluate its robustness. This cross-sectional, retrospective study included 1040 cases (520 each from two institutions) in which an intensity calibration phantom (B-MAS200, Kyoto Kagaku, Kyoto, Japan) was used. A training dataset was created by manually segmenting the phantom regions for 40 cases (20 cases for each institution). The CNN model's segmentation accuracy was assessed with the Dice coefficient, and the average symmetric surface distance was assessed through fourfold cross-validation. Further, absolute difference of HU was compared between manually and automatically segmented regions. The system was tested on the remaining 1000 cases. For each institution, linear regression was applied to calculate the correlation coefficients between HU and phantom density. The source code and the model used for phantom segmentation can be accessed at https://github.com/keisuke-uemura/CT-Intensity-Calibration-Phantom-Segmentation . The median Dice coefficient was 0.977, and the median average symmetric surface distance was 0.116mm. The median absolute difference of the segmented regions between manual and automated segmentation was 0.114 HU. For the test cases, the median correlation coefficients were 0.9998 and 0.999 for the two institutions, with a minimum value of 0.9863. The proposed CNN model successfully segmented the calibration phantom regions in CT images with excellent accuracy.

Absorption of Electromagnetic Radiation on Human Lower Back Region

In this paper a simulation study is conducted on lower back region of human phantom to observe the absorption of electromagnetic (EM) radiation. To investigate the effectiveness, EM radiation with different frequencies (1-100 GHz) is administrated step by step in different tissue thickness (up to 25 mm) of lower back region of human phantom and using EM simulator HFSS, return loss (RL) is recorded at every stage. From the results, it is found that when radiation with frequency 0.899 GHz to 1. 089 GHz (~1 GHz) is applied return loss is varies from 0.413 dB to 1.022 dB in different thicknesses. This indicates that only 1.1 % of the incident power is absorbed maximally. When radiation of 9.899 GHz to 10.099 GHz (~10 GHz) frequency is applied, the return loss value obtained is 6.731 dB to 6.280 dB for different tissue thicknesses. This indicates that only 10.1 % power is absorbed maximally. Finally, when radiation with frequency 99.899 GHz to 100.1 GHz (~ 0.1 THz) is applied, the return loss value is found ranging from 26.902 dB to 26.429 dB in different thicknesses which indicates that almost 99.9% of the incident radiation is absorbed by the human tissue i.e. almost 100% of the incident radiation is absorbed in human lower back region in THz range. From therapeutic point of view, almost the entire incident radiation is attenuated to the lower back region with THz radiation which is clinically very useful in treating chronic low back pain.