Phantom Images Research Articles

Contrast and quantum noise in single-exposure dual-energy thoracic imaging with photon-counting x-ray detectors

Objective.Photon-counting x-ray detectors (PCDs) can produce dual-energy (DE) x-ray images of lung cancer in a single x-ray exposure. It is important to understand the factors that affect contrast, noise and the contrast-to-noise ratio (CNR). This study quantifies the dependence of CNR on tube voltage, energy threshold and patient thickness in single exposure, DE, bone-suppressed thoracic imaging with PCDs, and elucidates how the fundamental processes inherent in x-ray detection by PCDs contribute to CNR degradation.Approach.We modeled the DE CNR for five theoretical PCDs, ranging from an ideal PCD that detects every primary photon in the correct energy bin while rejecting all scattered radiation to a non-ideal PCD that suffers from charge-sharing and electronic noise, and detects scatter. CNR was computed as a function of tube voltage and high energy threshold for average and larger-than-average patients. Model predictions were compared with experimental data extracted from images acquired using a cadmium telluride (CdTe) PCD with two energy bins and analog charge summing for charge-sharing suppression. The imaging phantom simulated attenuation, scatter and contrast in lung nodule imaging. We quantified CNR improvements achievable with anti-correlated noise reduction (ACNR) and measured the range of exposure rates over which pulse pile-up is negligible.Main Results.The realistic model predicted overall trends observed in the experimental data. CNR improvements with ACNR were approximately five-fold, and modeled CNR-enhancements were on average within 10% of experiment. CNR increased modestly (i.e.<20%) when increasing the tube voltage from 90 kV to 130 kV. Optimal energy thresholds ranged from 50 keV to 70 keV across all tube voltages and patient thicknesses with and without ACNR. Quantum efficiency, electronic noise, charge sharing and scatter degraded CNR by ~50%. Charge sharing and scatter had the largest effect on CNR, degrading it by ~30% and ~15% respectively. Dead-time losses were less than 5% for patient exposure rates within the range of clinical exposure rates.Significance.In this study, we (1) employed analytical and computational models to assess the impact of different factors on CNR in single-exposure DE imaging with PCDs, (2) evaluated the accuracy of these models in predicting experimental trends, (3) quantified improvements in CNR achievable through ACNR and (4) determined the range of patient exposure rates at which pulse pile-up can be considered negligible. To the best of our knowledge, this study represents the first systematic investigation of single-exposure DE imaging of lung nodules with PCDs.

Optimization of reconstruction in quantitative brain PET images: Benefits from PSF modeling and correction of edge artifacts.

Modern PET reconstruction algorithms incorporate point-spread-function (PSF) correction to mitigate partial volume effect. However, PSF correction can introduce edge artifacts that lead to quantification errors. Consequently, current international guidelines advise against using PSF correction in brain PET reconstruction. We aimed to investigate PSF-induced quantification errors in recent digital PET systems and identify conditions that mitigate them. This study utilized brain PET imaging with alginate-based realistic phantoms, simulating lesion-to-background activity ratios of 10:1 and 2:1, with eleven reconstruction parameter sets. Phantoms were prepared using a commercial anthropomorphic head phantom and two homemade inserts. Each insert contained a homogeneous 18F-FDG alginate background with hot spheres of varying diameter (3, 4, 6, 8, 10, 12, and 15mm). PET imaging was conducted on a digital PET-CT system Biograph Vision 600 (Siemens), with a 10 min scan duration. Imaging was performed with and without PSF correction, with 2, 4, 6, 12, 18, or 24 iterations in reconstruction, and with or without additional Gaussian postfiltering. We assessed the recovery coefficient (RC), contrast recovery coefficient (CRC), variability, and CRC-to-variability ratios for each sphere size and reconstruction parameter set. PSF-corrected images of the 10:1 spheres exhibited a nonmonotonic CRC-to-sphere diameter relationship due to edge artifacts overshoot in the 10mm-diameter sphere. In contrast, PSF images of the 2:1 spheres showed a monotonically increasing relationship. Non-PSF images of both phantoms showed an expected monotonically increasing CRC-to-sphere diameter relationship but with lower CRC values compared to PSF images. The nonmonotonic relationship observed with 10:1 spheres was mitigated by applying a 3-mm FWHM Gaussian postfiltering. For both phantoms, reconstructions with 6 iterations, PSF correction, and additional 3-mm FWHM Gaussian postfiltering demonstrated the highest CRC-to-variability ratios. Our findings indicate that Gaussian postfiltering suppresses PSF artifacts. This parameter set corrected the nonmonotonic CRC-to-sphere diameter relationship and improved the CRC-to-variability ratio compared to non-PSF reconstructions. Therefore, to enhance lesion detectability without compromising quantification accuracy, PSF correction coupled with Gaussian postfiltering should be used in brain PET.

Comparative assessment and QA measurement array validation of Monte Carlo and Collapsed Cone dose algorithms for small fields and clinical treatment plans.

Many studies have demonstrated superior performance of Monte Carlo (MC) over type B algorithms in heterogeneous structures. However, even in homogeneous media, MC dose simulations should outperform type B algorithms in situations of electronic disequilibrium, such as small and highly modulated fields. Our study compares MC and Collapsed Cone (CC) dose algorithms in RayStation 12A. Under consideration are 6 MV and 6 MV flattening filter-free (FFF) photon beams, relevant for VMAT plans such as head-and-neck and stereotactic lung treatments with heterogeneities, as well as plans for multiple brain metastases in one isocenter, involving highly modulated small fields. We aim to investigate collimator angle dependence of small fields and performance differences between different combinations of ArcCHECK configuration and dose algorithm. Several verification tests were performed, ranging from simple rectangular fields to highly modulated clinical plans. To evaluate and compare the performance of the models, the agreements between calculation and measurement are compared between MC and CC. Measurements include water tank measurements for test fields, ArcCHECK measurements for test fields and VMAT plans, and film dosimetry for small fields. In very small or narrow fields, our measurements reveal a strong dependency of dose output to collimator angle for VersaHD with Agility MLC, reproduced by both dose algorithms. ArcCHECK results highlight a suboptimal agreement between measurements and MC calculations for simple rectangular fields when using inhomogeneous ArcCHECK images. Therefore, we advocate for the use of homogeneous phantom images, particularly for static fields, in ArcCHECK verification with MC. MC might offer performance benefits for more modulated treatment fields. In ArcCHECK results for clinical plans, MC performed comparable to CC for 6 MV. For 6 MV FFF and the preferred homogeneous phantom image, MC resulted in consistently better results (13%-64% lower mean gamma index) compared to CC.

Quantitative SPECT imaging of 155Tb and 161Tb for preclinical theranostic radiopharmaceutical development.

Element-equivalent matched theranostic pairs facilitate quantitative in vivo imaging to establish pharmacokinetics and dosimetry estimates in the development of preclinical radiopharmaceuticals. Terbium radionuclides have significant potential as matched theranostic pairs for multipurpose applications in nuclear medicine. In particular, 155Tb (t1/2 = 5.32 d) and 161Tb (t1/2 = 6.89 d) have been proposed as a theranostic pair for their respective applications in single photon emission computed tomography (SPECT) imaging and targeted beta therapy. Our study assessed the performance of preclinical quantitative SPECT imaging with 155Tb and 161Tb. A hot rod resolution phantom with rod diameters ranging between 0.85 and 1.70mm was filled with either 155Tb (21.8 ± 1.7 MBq/mL) or 161Tb (23.6 ± 1.9 MBq/mL) and scanned with the VECTor preclinical SPECT/CT scanner. Image performance was evaluated with two collimators: a high energy ultra high resolution (HEUHR) collimator and an extra ultra high sensitivity (UHS) collimator. SPECT images were reconstructed from photopeaks at 43.0keV, 86.6keV, and 105.3keV for 155Tb and 48.9keV and 74.6keV for 161Tb. Quantitative SPECT images of the resolution phantoms were analyzed to report inter-rod contrast, recovery coefficients, and contrast-to-noise metrics. Quantitative SPECT images of the resolution phantom established that the HEUHR collimator resolved all rods for 155Tb and 161Tb, and the UHS collimator resolved rods ≥ 1.10mm for 161Tb and ≥ 1.30mm for 155Tb. The HEUHR collimator maintained better quantitative accuracy than the UHS collimator with recovery coefficients up to 92%. Contrast-to-noise metrics were also superior with the HEUHR collimator. Both 155Tb and 161Tb demonstrated potential for applications in preclinical quantitative SPECT imaging. The high-resolution collimator achieves < 0.85mm resolution and maintains quantitative accuracy in small volumes which is advantageous for assessing sub organ activity distributions in small animals. This imaging method can provide critical quantitative information for assessing and optimizing preclinical Tb-radiopharmaceuticals.

A novel internal target volume definition based on velocity and time of respiratory target motion for external beam radiotherapy.

This study aimed to develop a novel internal target volume (ITV) definition for respiratory motion targets, considering target motion velocity and time. The proposed ITV was evaluated in respiratory-gated radiotherapy. An ITV modified with target motion velocity and time (ITVvt) was defined as an ITV that includes a target motion based on target motion velocity and time. The target motion velocity was calculated using four-dimensional computed tomography (4DCT) images. The ITVvts were created from phantom and clinical 4DCT images. The phantom 4DCT images were acquired using a solid phantom that moved with a sinusoidal waveform (peak-to-peak amplitudes of 10 and 20mm and cycles of 2-6s). The clinical 4DCT images were obtained from eight lung cancer cases. In respiratory-gated radiotherapy, the ITVvt was compared with conventional ITVs for beam times of 0.5-2s within the gating window. The conventional ITV was created by adding a uniform margin as the maximum motion within the gating window. In the phantom images, the maximum volume difference between the ITVvt and conventional ITV was -81.9%. In the clinical images, the maximum volume difference was -53.6%. Shorter respiratory cycles and longer BTs resulted in smaller ITVvt compared with the conventional ITV. Therefore, the proposed ITVvt plan could be used to reduce treatment volumes and doses to normal tissues.

Online MR-guided proton and ion beam radiotherapy: investigation of image quality

Objective.Magnetic resonance (MR) images free of artefacts are of pivotal importance for MR-guided ion radiotherapy. This study investigates MR image quality for simultaneous irradiation in an experimental setup using phantom imaging as well asin-vivoimaging. Observed artefacts are described within the study and their cause is investigated with the goal to find conclusions and solutions for potential future hybrid devices.Approach.An open MR scanner with a field strength of 0.25 T has been installed in front of an ion beamline. Simultaneous magnetic resonance imaging and irradiation using raster scanning were performed to analyze image quality in dedicated phantoms. Magnetic field measurements were performed to assist the explanation of observed artifacts. In addition,in-vivoimages were acquired by operating the magnets for beam scanning without transporting a beam.Main Results.The additional frequency component within the isocenter caused by the fringe field of the horizontal beam scanning magnet correlates with the amplitude and frequency of the scanning magnet steering and can cause ghosting artifacts in the images. These are amplified with high currents and fast operating of the scanning magnet. Applying a real-time capable pulse sequencein-vivorevealed no ghosting artifacts despite a continuously changing current pattern and a clinical treatment plan activation scheme, suggesting that the use of fast imaging is beneficial for the aim of creating high quality in-beam MR images. This result suggests, that the influence of the scanning magnets on the MR acquisition might be of negligible importance and does not need further measures like extensive magnetic shielding of the scanning magnets.Significance.Our study delimited artefacts observed in MR images acquired during simultaneous raster scanning ion beam irradiation. The application of a fast pulse sequence showed no image artefacts and holds the potential that online MR imaging in future hybrid devices might be feasible.

Cherenkov imaging combined with scintillation dosimetry provides real-time positional and dose monitoring for radiotherapy patients with cardiac implanted electronic devices

Background and purposeCardiac implanted electronic devices (CIED) require dose monitoring during each fraction of radiotherapy, which can be time consuming and may have delayed read-out times. This study explores the potential of Cherenkov imaging combined with scintillation dosimetry as an alternative verification system. Methods and materialsTime-gated, complementary metal–oxide–semiconductor (iCMOS) cameras were used to collect video images of anthropomorphic phantoms and patients undergoing radiation treatment near chest wall cardiac devices. Scintillator discs and optically stimulated luminescence dosimeters (OSLDs) were used for dose measurement. Accuracy of spatial delivery was assessed by overlaying predicted surface dose outlines derived from the treatment planning system (TPS) with the Cherenkov images. Dose measurements from OSLDs and scintillators were compared. ResultsIn phantom studies, Cherenkov images visibly indicated when dose was delivered to the CIED as compared to non-overlapping dose deliveries. Comparison with dose overlays revealed congruence at the planned position and non-congruence when the phantom was shifted from the initial position. Absolute doses derived from scintillator discs aligned well with the OSLD measurements and TPS predictions for three different positions, measuring within 10 % for in-field positions and within 5 % for out-of-field positions. For two patients with CIEDs imaged over 18 fractions, Cherenkov imaging confirmed positional accuracy for all fractions, and dose measured by scintillator discs deviated by <0.015 Gy from the OSLD measurements. ConclusionsCherenkov imaging combined with scintillation dosimetry presents an alternative methodology for CIED monitoring with the added benefit of instantly detecting deviations, enabling timely corrective actions or proper patient triage.

Comprehensive commissioning of a cone beam CT imaging ring for treatment of HDR GYN patients

PurposeA new mobile cone beam computed tomography (CBCT) imaging ring (IRm, Elekta, v2.10.6, Veenendaal, Netherlands) has recently been proposed for brachytherapy to improve procedure efficiency. We describe the commissioning process and end-to-end tests for GYN HDR brachytherapy employing IRm CBCT imaging. Materials and MethodsCommissioning included imaging isocenter test, 3D image quality, 2D imaging quality, image dose, and tube characteristics. CIRS HDR GYN phantom and Venezia CT/MR gynecological applicator were used to perform end-to-end (E2E) tests and optimize workflow. Venezia applicator and four interstitial needles were inserted into the phantom and IRm CBCT images were acquired. Phantom and applicator were scanned with CT scanner (Siemens SOMATOM go.Open Pro) using department's pelvis imaging protocol. MR imaging was performed using 0.35T MR Linac TRUFI pulse sequence. CBCT images were registered to CT and MR using rigid registration to assess image quality and applicator geometry fidelity. ResultsAll physics tests passed within acceptance tolerances. Registration of CBCT images to MR and CT scans was acceptable for applicator placement. Applicator registration of CBCT images to CT demonstrated excellent agreement of most distal source dwell position (<1 mm). Slice thickness was also measured to be 1.25 mm, within 0.5 mm of its nominal value. ConclusionBased on E2E and commissioning results, IRm is an appropriate tool for brachytherapy treatment planning. This study demonstrated good image quality in GYN phantom and Venezia applicator using the IRm. Distal source dwell position agreement between CBCT and CT was acceptable for clinical use.

Small, Fluorinated Mn2+ Chelate as an Efficient 1H and 19F MRI Probe.

We explore the potential of fluorine-containing small Mn2+ chelates as alternatives to perfluorinated nanoparticles, widely used as 19F MRI probes. In MnL1, the cyclohexanediamine skeleton and two piperidine rings, involving each a metal-coordinating amide group and an appended CF3 moiety, provide high rigidity to the complex. This allows for good control of the Mn-F distance (rMnF=8.2±0.2 Å determined from 19F relaxation data), as well as for high kinetic inertness (a dissociation half-life of 1285 h is estimated for physiological conditions). The paramagnetic Mn2+ leads to a ~150-fold acceleration of the longitudinal 19F relaxation, with moderate line-broadening effect, resulting in T2/T1 ratios of 0.8 (9.4 T). Owing to its inner sphere water molecule, MnL1 is a good 1H relaxation agent as well (r1=5.36 mM-1 s-1 at 298 K, 20 MHz). MnL1 could be readily visualized in 19F MRI by using fast acquisition techniques, both in phantom images and living mice following intramuscular injection, with remarkable signal-to-noise ratios and short acquisition times. While applications in targeted imaging or cell therapy monitoring require further optimisation of the molecular structure, these results argue for the potential of such small, monohydrated and fluorinated Mn2+ complexes for combined 19F and 1H MRI detection.

Small, Fluorinated Mn2+ Chelate as an Efficient 1H and 19F MRI Probe

AbstractWe explore the potential of fluorine‐containing small Mn2+ chelates as alternatives to perfluorinated nanoparticles, widely used as 19F MRI probes. In MnL1, the cyclohexanediamine skeleton and two piperidine rings, involving each a metal‐coordinating amide group and an appended CF3 moiety, provide high rigidity to the complex. This allows for good control of the Mn−F distance (rMnF=8.2±0.2 Å determined from 19F relaxation data), as well as for high kinetic inertness (a dissociation half‐life of 1285 h is estimated for physiological conditions). The paramagnetic Mn2+ leads to a ~150‐fold acceleration of the longitudinal 19F relaxation, with moderate line‐broadening effect, resulting in T2/T1 ratios of 0.8 (9.4 T). Owing to its inner sphere water molecule, MnL1 is a good 1H relaxation agent as well (r1=5.36 mM−1 s−1 at 298 K, 20 MHz). MnL1 could be readily visualized in 19F MRI by using fast acquisition techniques, both in phantom images and living mice following intramuscular injection, with remarkable signal‐to‐noise ratios and short acquisition times. While applications in targeted imaging or cell therapy monitoring require further optimisation of the molecular structure, these results argue for the potential of such small, monohydrated and fluorinated Mn2+ complexes for combined 19F and 1H MRI detection.

Light-weight neural network for intra-voxel structure analysis.

We present a novel neural network-based method for analyzing intra-voxel structures, addressing critical challenges in diffusion-weighted MRI analysis for brain connectivity and development studies. The network architecture, called the Local Neighborhood Neural Network, is designed to use the spatial correlations of neighboring voxels for an enhanced inference while reducing parameter overhead. Our model exploits these relationships to improve the analysis of complex structures and noisy data environments. We adopt a self-supervised approach to address the lack of ground truth data, generating signals of voxel neighborhoods to integrate the training set. This eliminates the need for manual annotations and facilitates training under realistic conditions. Comparative analyses show that our method outperforms the constrained spherical deconvolution (CSD) method in quantitative and qualitative validations. Using phantom images that mimic in vivo data, our approach improves angular error, volume fraction estimation accuracy, and success rate. Furthermore, a qualitative comparison of the results in actual data shows a better spatial consistency of the proposed method in areas of real brain images. This approach demonstrates enhanced intra-voxel structure analysis capabilities and holds promise for broader application in various imaging scenarios.

Parameter optimisation for image acquisition and stacking in carbon dioxide digital subtraction angiography.

The aim of this study was to optimise the vessel angle as well as the stack number from the profiles of carbon dioxide digital subtraction angiography (CO2-DSA) images of a water phantom containing an artificial vessel tilted at different angles which imitate arteries in the body. The artificial vessel was tilted at 0°, 15°, and 30° relative to the horizontal axis with its centre as the pivot point, and CO2-DSA images were acquired at each vessel tilt angle. The maximum opacity method was used to stack up to four images of the next frame one by one. The signal-to-noise ratio (SNR) was determined from the profile curves. The Wilcoxon rank sum test was used to evaluate whether the profile curve and SNR differed depending on the vessel tilt angle or stack number, and a p-value of less than 0.05 was considered statistically significant. Images acquired at 0° had a significantly lower SNR than images acquired at 15° (p = 0.10). When the vessel angle was 30°, the profile curves were significantly improved (p < 0.05) when two or more images were stacked over the original image. Images with a good SNR were acquired at the vessel tilt angle of 15°, and the shape of the profile curve was improved when two or more images were stacked on the original image. This study demonstrates that the quality of images acquired using CO2-DSA can be significantly improved through parameter optimisation for image acquisition and post-processing.

Label-free 3D molecular imaging of living tissues using Raman spectral projection tomography

The ability to image tissues in three dimensions (3D) with label-free molecular contrast at the mesoscale would be a valuable capability in biology and biomedicine. Here, we introduce Raman spectral projection tomography (RSPT) for volumetric molecular imaging with optical sub-millimeter spatial resolution. We have developed a RSPT imaging instrument capable of providing 3D molecular contrast in transparent and semi-transparent samples. We also created a computational pipeline for multivariate reconstruction to extract label-free spatial molecular information from Raman projection data. Using these tools, we demonstrate imaging and visualization of phantoms of various complex shapes with label-free molecular contrast. Finally, we apply RSPT as a tool for imaging of molecular gradients and extracellular matrix heterogeneities in fixed and living tissue-engineered constructs and explanted native cartilage tissues. We show that there exists a favorable balance wherein employing Raman spectroscopy, with its advantages in live cell imaging and label-free molecular contrast, outweighs the reduction in imaging resolution and blurring caused by diffuse photon propagation. Thus, RSPT imaging opens new possibilities for label-free molecular monitoring of tissues.

Image Quality of Cardiac Silicon Photomultiplier PET/CT Using an Infant Phantom of Extremely Low Birth Weight.

The lack of pediatrics-specific equipment for nuclear medicine imaging has resulted in insufficient diagnostic information for newborns, especially low-birth-weight infants. Although PET offers high spatial resolution and low radiation exposure, its use in newborns is limited. This study investigated the feasibility of cardiac PET imaging using the latest silicon photomultiplier (SiPM) PET technology in infants of extremely low birth weight (ELBW) using a phantom model. Methods: The study used a phantom model representing a 500-g ELBW infant with brain, cardiac, liver, and lung tissues. The cardiac tissue included a 3-mm-thick defect mimicking myocardial infarction. Organ tracer concentrations were calculated assuming 18F-FDG myocardial viability scans and 18F-flurpiridaz myocardial perfusion scans and were added to the phantom organs. Imaging was performed using an SiPM PET/CT scanner with a 5-min acquisition. The data acquired in list mode were reconstructed using 3-dimensional ordered-subsets expectation maximization with varying iterations. Image evaluation was based on the depiction of the myocardial defect compared with normal myocardial accumulation. Results: Increasing the number of iterations improved the contrast of the myocardial defect for both tracers, with 18F-flurpiridaz showing higher contrast than 18F-FDG. However, even at 50 iterations, both tracers overestimated the defect accumulation. A bull's-eye image can display the flow metabolism mismatch using images from both tracers. Conclusion: SiPM PET enabled cardiac PET imaging in a 500-g ELBW phantom with a 1-g heart. However, there were limitations in adequately depicting these defects. Considering the image quality and defect contrast,18F-flurpiridaz appears more desirable than 18F-FDG if only one of the two can be used.

RF coil that minimizes electronic components while enhancing performance for rodent MRI at 7 Tesla.

This study introduces a novel volume coil design that features two slotted end-plates connected by six rungs, resembling the traditional birdcage coil. The end rings are equipped with six evenly distributed circular slots, inspired by Mansfield's cavity resonator theory, which suggests that circular slots can generate a baseline resonant frequency. One notable advantage of this proposed coil design is its reduced reliance on electronic components compared to other volume coils, making it more efficient. Additionally, the dimensions of the coil can be theoretically computed in advance, enhancing its practicality. To evaluate the performance and safety of the coil, electromagnetic field and specific absorption rate simulations were simulated using a cylindrical saline phantom and the finite element method. Furthermore, a transceiver coil prototype optimized for 7 Tesla and driven in quadrature was constructed, enabling whole-body imaging of rats. The resonant frequency of the coil prototype obtained through experimental measurements closely matched the theoretical frequency derived from Mansfield's theory. To validate the coil design, phantom images were acquired to demonstrate its viability and assess its performance. These images also served to validate the magnetic field simulations. The experimental results aligned well with the simulation findings, confirming the reliability of the proposed coil design. Importantly, the prototype coil showcased significant improvements over a similarly-sized birdcage coil, indicating its potential for enhanced performance. The noise figure was lower in the prototype versus the birdcage coil (NFbirdcage-NFslotcage= 0.7). Phantom image data were also used to compute the image SNR, giving SNRslotcage/SNRbirdcage= 34.36/24.34. By proving the feasibility of the coil design through successful rat whole-body imaging, the study provides evidence supporting its potential as a viable option for high-field MRI applications on rodents.

Detection of malignant breast tissue using SAR observation with microwave imaging and convolutional neural network

The research paper introduces a deep learning approach for distinguishing between benign and malignant breast tissues using Ultra Wide Band (UWB) microwave imaging. A multi-resonant monopole microstrip patch antenna was crafted and placed on a female breast phantom model containing a tumor. The phantom’s dielectric properties were adjusted to mimic those of benign and malignant tissues. The Specific Absorption Rate (SAR) was analyzed by rotating the antenna at various angles throughout the phantom’s trajectory. Images capturing the SAR distribution over the breast phantom at different antenna resonances were obtained. The popular Convolutional Neural Network (CNN) based AlexNet model was employed for autonomous feature learning from SAR images. To address the challenge of overfitting with a limited dataset, the study utilized image augmentation and transfer learning methods. The proposed model achieved an impressive 98.59% accuracy in classifying benign and malignant breast phantom images, surpassing the performance of three other CNN models—VggNet16, GoogleNet, and ResNet. Notably, this microwave imaging system based on SAR images detected tumors as small as 1 mm with an accuracy of 97.08% outperforming existing malignancy screening techniques.

High-quality FLORET UTE imaging for clinical translation.

To develop a robust 3D ultrashort-TE (UTE) protocol that can reproducibly provide high-quality images, assessed by the ability to yield clinically diagnostic images, and is suitable for clinical translation. Building on previous work, a UTE sampled with Fermat looped orthogonally encoded trajectories (FLORET) was chosen as a starting point due to its shorter, clinically reasonable scan times. Modifications to previous FLORET implementations included gradient waveform frequency limitations, a new trajectory ordering scheme, a balanced SSFP implementation, fast gradient spoiling, and full inline reconstruction. FLORET images were collected in phantoms and humans on multiple scanners and sites to demonstrate these improvements. The updates to FLORET provided high-quality images in phantom, musculoskeletal, and pulmonary applications. The gradient waveform modifications and new trajectory ordering scheme significantly reduced visible artifacts. Fast spoiling reduced acquisition time by 20%-28%. Across the various scanners and sites, the inline image quality was consistent and of diagnostic quality. Total image acquisition plus reconstruction time was less than 4 min for musculoskeletal and pulmonary applications with reconstructions taking less than 1 min. Recently developed improvements for the FLORET sequence have enabled robust, high-quality UTE acquisitions with short acquisition and reconstruction times. This enables clinical UTE imaging as demonstrated by the implementation of the sequence and acquisition on five MRI scanners, at three different sites, without the need for any additional system characterization or measurements.

Line-field confocal optical coherence tomography based on tandem interferometry with a focus-tunable lens.

This article introduces an innovative line-field confocal optical coherence tomography (LC-OCT) system based on tandem interferometry, featuring a focus-tunable lens for dynamic focusing. The principle of tandem interferometry is first recalled, and an analytical expression of the interferometric signal detected is established in order to identify the influence of key experimental parameters. The LC-OCT system is based on a Linnik-type imaging interferometer with a focus-tunable lens for focus scanning, coupled to a Michelson-type compensating interferometer using a piezoelectric linear translation stage for coherence plane scanning. The system achieves axial and lateral image resolutions of approximately 1 µm over the entire imaging depth (400 µm), in line with conventional LC-OCT. Vertical section images (B-scans) of skin acquired at 14.3 fps reveal distinguishable structures within the epidermis and dermis. Using refocusing and stitching, images of a tissue phantom were obtained with an imaging depth superior to 1.4 mm. The system holds promise for LC-OCT miniaturization, along with enhanced imaging speed and extended imaging depth.

Design of a kidney phantom for ultrasound imaging

Design of a kidney phantom for ultrasound imaging

Enhancing Image Contrast in Breast USCT Reflection Imaging Using Coherence Factor Beamforming

Abstract Breast cancer is the most common cancer worldwide, and early screening is essential. Existing breast ultrasound is affordable and convenient, but its 2D image quality is poor, and it heavily relies on the doctor’s skills. The novel breast ultrasound computed tomography (USCT) can use a ring array probe to implement hundreds of single transducer emission for full-view focusing synthetic aperture reflection imaging, thereby obtaining high-resolution 3D images. However, single transducer emission results in low acoustic intensity, which further leads to low signal-to-noise ratio and low contrast of reflection images. To improve image contrast, this study incorporated beamforming with coherence factor (CF) into reflection imaging using ring transducers, promising to produce high-contrast USCT reflection images. For evaluation, we developed a USCT prototype with 2048 elements and conducted phantom experiments. We conducted phantom experiments. Results showed that the contrast achieved by the coherence factor method of the breast phantom image is improved from 24.54 dB to 63.18 dB, and the artifacts are significantly suppressed. It can be seen that the CF method could significantly improve the contrast of the breast USCT reflection image.