Showing papers on "Imaging phantom published in 2023"

Photon-counting detector coronary CT angiography: impact of virtual monoenergetic imaging and iterative reconstruction on image quality.

Abstract: OBJECTIVES To assess the impact of low kilo-electronvolt (keV) virtual monoenergetic image (VMI) energies and iterative reconstruction on image quality of clinical photon-counting detector coronary CT angiography (CCTA). METHODS CCTA with PCD-CT (prospective ECG-triggering, 120 kVp, automatic tube current modulation) was performed in a high-end cardiovascular phantom with dynamic flow, pulsatile heart motion, and including different calcified plaques with various stenosis grades and in 10 consecutive patients. VMI at 40,50,60 and 70 keV were reconstructed without (QIR-off) and with all quantum iterative reconstruction (QIR) levels (QIR-1 to 4). In the phantom, noise power spectrum, vessel attenuation, contrast-to-noise-ratio (CNR), and vessel sharpness were measured. Two readers graded stenoses in the phantom and graded overall image quality, subjective noise, vessel sharpness, vascular contrast, and coronary artery plaque delineation on 5-point Likert scales in patients. RESULTS In the phantom, noise texture was only slightly affected by keV and QIR while noise increased by 69% from 70 keV QIR-4 to 40 keV QIR-off. Reconstructions at 40 keV QIR-4 exhibited the highest CNR (46.1 ± 1.8), vessel sharpness (425 ± 42 ∆HU/mm), and vessel attenuation (1098 ± 14 HU). Stenosis measurements were not affected by keV or QIR level (p > 0.12) with an average error of 3%/6% for reader 1/reader 2, respectively. In patients, across all subjective categories and both readers, 40 keV QIR-3 and QIR-4 images received the best scores (p < 0.001). CONCLUSION Forty keV VMI with QIR-4 significantly improved image quality of CCTA with PCD-CT. ADVANCES IN KNOWLEDGE PCD-CT at 40 keV and QIR-4 improves image quality of CCTA.

Reduction of emission time for [68Ga]Ga-PSMA PET/CT using the digital biograph vision: a phantom study

Abstract: The aim of this phantom study was to optimize the [68Ga]Ga-PSMA PET/CT examination in terms of scan time duration and image reconstruction parameters, in combination with PSF and TOF modelling, in a digital Biograph Vision PET/CT scanner.Three types of phantoms were used: 1) soft-tissue tumor phantom consisting of six spheres mounted in a torso phantom; 2) bone-lung tumor phantom; 3) resolution phantom. Phantom inserts were filled with activity concentrations (ACs) that were derived from clinical data. Phantom data were acquired in list-mode at one bed position. Images with emission data ranging from 30 to 210 s in 30-s increments were reconstructed from a reference image acquired with 3.5-min emission. Iterative image reconstruction (OSEM), point-spread-function (PSF) and time-of-flight (TOF) options were applied using different iterations, Gaussian filters, and voxel sizes. The criteria for image quality was lesion detectability and lesion quantification, evaluated as contrast-to-noise ratio (CNR) and maximum AC (peak AC), respectively. A threshold value of CNR above 6 and percentage maximum AC (peak AC) deviation range of ±20% of the reference image were considered acceptable. The proposed single-bed scan time reduction was projected to a whole-body examination (patient validation scan) using the continuous-bed-motion mode.Sphere and background ACs of 20 kBq/mL and 1 kBq/mL were selected, respectively. The optimized single-bed scan time was approximately 60 s using OSEM-TOF or OSEM-TOF+PSF (four iterations, 4.0-mm Gaussian filter and almost isotropic voxel size of 3.0-mm side length), resulting in a PET spatial resolution of 6.3 mm for OSEM-TOF and 5.5 mm for OSEM-TOF+PSF. In the patient validation, the maximum percentage difference in lesion quantification between standard and optimized protocol (whole-body scan time of 15 vs. 5 min) was below 19%.A reduction of single-bed and whole-body scan time for [68Ga]Ga-PSMA PET/CT compared to current recommended clinical acquisition protocols is postulated. Clinical studies are warranted to validate the applicability of this protocol.

Photon-counting CT Material Decomposition: Initial Experience in Assessing Adrenal Adenoma

Abstract: HomeRadiologyVol. 306, No. 1 PreviousNext Original ResearchGenitourinary ImagingPhoton-counting CT Material Decomposition: Initial Experience in Assessing Adrenal AdenomaSimon Lennartz , Denise Schoenbeck, Jan Robert Kröger, Jan Borggrefe, Julius Henning NiehoffSimon Lennartz , Denise Schoenbeck, Jan Robert Kröger, Jan Borggrefe, Julius Henning NiehoffAuthor AffiliationsFrom the Institute for Diagnostic and Interventional Radiology, University of Cologne, Faculty of Medicine and University Hospital Cologne, Kerpener Strasse 62, 50937 Cologne, Germany (S.L.); and Department of Radiology, Neuroradiology and Nuclear Medicine, Johannes Wesling University Hospital, Ruhr University Bochum, Bochum, Germany (D.S., J.R.K., J.B., J.H.N.).Address correspondence to S.L. (email: [email protected]).Simon Lennartz Denise SchoenbeckJan Robert KrögerJan BorggrefeJulius Henning NiehoffPublished Online:Aug 23 2022https://doi.org/10.1148/radiol.220919See editorial byAmir PourmortezaMoreSectionsFull textPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In AbstractSee also the editorial by Pourmorteza in this issue.Download as PowerPointReferences1. Rajendran K, Petersilka M, Henning A, et al. First Clinical Photon-counting Detector CT System: Technical Evaluation. Radiology 2022;303(1):130–138. Link, Google Scholar2. Thomsen FSL, Horstmeier S, Niehoff JH, Peña JA, Borggrefe J. Effective Spatial Resolution of Photon Counting CT for Imaging of Trabecular Structures is Superior to Conventional Clinical CT and Similar to High Resolution Peripheral CT. Invest Radiol 2022. https://doi.org/10.1097/RLI.0000000000000873. Published online March 21, 2022. Crossref, Medline, Google Scholar3. Sartoretti T, Mergen V, Higashigaito K, Eberhard M, Alkadhi H, Euler A. Virtual Noncontrast Imaging of the Liver Using Photon-Counting Detector Computed Tomography: A Systematic Phantom and Patient Study. Invest Radiol 2022;57(7):488–493. Crossref, Medline, Google Scholar4. Niehoff JH, Woeltjen MM, Laukamp KR, Borggrefe J, Kroeger JR. Virtual Non-Contrast versus True Non-Contrast Computed Tomography: Initial Experiences with a Photon Counting Scanner Approved for Clinical Use. Diagnostics (Basel) 2021;11(12):2377. Crossref, Medline, Google Scholar5. Mileto A, Nelson RC, Marin D, Roy Choudhury K, Ho LM. Dual-energy multidetector CT for the characterization of incidental adrenal nodules: diagnostic performance of contrast-enhanced material density analysis. Radiology 2015;274(2):445–454. Link, Google Scholar6. Nagayama Y, Inoue T, Oda S, et al. Adrenal Adenomas versus Metastases: Diagnostic Performance of Dual-Energy Spectral CT Virtual Noncontrast Imaging and Iodine Maps. Radiology 2020;296(2):324–332. Link, Google ScholarArticle HistoryReceived: Apr 14 2022Revision requested: May 26 2022Revision received: June 14 2022Accepted: June 24 2022Published online: Aug 23 2022Published in print: Jan 2023 FiguresReferencesRelatedDetailsCited ByAbdominal Imaging in the Coming Decades: Better, Faster, Safer, and Cheaper?Perry J. Pickhardt, 14 March 2023 | Radiology, Vol. 0, No. 0Photon-counting CT to Virtual Noncontrast CT ImagesAmir Pourmorteza, 23 August 2022 | Radiology, Vol. 306, No. 1Photon-counting detector CT: early clinical experience reviewThomasSartoretti, Joachim EWildberger, ThomasFlohr, HatemAlkadhi2023 | The British Journal of RadiologyAccompanying This ArticlePhoton-counting CT to Virtual Noncontrast CT ImagesAug 23 2022RadiologyRecommended Articles Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal AdenomasRadiology2021Volume: 301Issue: 2pp. 360-368Unenhanced Dual-Layer Spectral-Detector CT for Characterizing Indeterminate Adrenal LesionsRadiology2021Volume: 301Issue: 2pp. 369-378Technical and Interpretive Pitfalls in Adrenal ImagingRadioGraphics2020Volume: 40Issue: 4pp. 1041-1060Adrenal Adenomas versus Metastases: Diagnostic Performance of Dual-Energy Spectral CT Virtual Noncontrast Imaging and Iodine MapsRadiology2020Volume: 296Issue: 2pp. 324-332Chemical Shift MR Imaging of the Adrenal Gland: Principles, Pitfalls, and ApplicationsRadioGraphics2016Volume: 36Issue: 2pp. 414-432See More RSNA Education Exhibits No More Doubts About Adrenal Lesions: An OverviewDigital Posters2018Symptomatic Adrenal Glands: The Role of Imaging in Clinical PracticeDigital Posters2019Adrenal Imaging in the Era of Radiomics: Current Indications and Future PerspectiveDigital Posters2019 RSNA Case Collection Non-hemorrhagic adrenal infarctionRSNA Case Collection2021Portal vein thrombosisRSNA Case Collection2020Portal vein varixRSNA Case Collection2021 Vol. 306, No. 1 Metrics Altmetric Score PDF download

Performance evaluation of the PennPET explorer with expanded axial coverage

Abstract: Objective. This work evaluated the updated PennPET Explorer total-body (TB) PET scanner, which was extended to 6 rings with updated readout firmware to achieve a 142 cm axial field of view (AFOV) without 7.6 cm inter-ring axial gaps. Approach. National Electrical Manufacturers Association (NEMA) NU 2-2018 measurements were performed with modifications including longer phantoms for sensitivity and count-rate measurements and additional positions for spatial resolution and image quality. A long uniform phantom and the clinical trials network (CTN) phantom were also used. Main results. The total sensitivity increased to 140 kcps MBq−1 for a 70 cm line, a gain of 1.8x compared to the same system with axial gaps; an additional 47% increase in total counts was observed with a 142 cm line at the same activity per cm. The noise equivalent count rate (NECR) increased by 1.8x without axial gaps. The peak NECR is 1550 kcps at 25 kBq cc−1 for a 140 cm phantom; due to increased randoms, the NECR is lower than with a 70 cm phantom, for which NECR is 2156 kcps cc−1 at 25 kBq cc−1 and continues increasing. The time-of-flight resolution is 250 ps, increasing by <10 ps at the highest activity. The axial spatial resolution degrades by 0.6 mm near the center of the AFOV, compared to 4 mm resolution near the end. The NEMA image quality phantom showed consistent contrast recovery throughout the AFOV. A long uniform phantom demonstrated axial uniformity of uptake and noise, and the CTN phantom demonstrated quantitative accuracy for both 18F and 89Zr. Significance. The performance evaluation of the updated PennPET Explorer demonstrates significant gains compared to conventional scanners and shows where the current NEMA standard needs to be updated for TB-PET systems. The comparisons of systems with and without inter-ring gaps demonstrate the performance trade-offs of a more cost-effective TB-PET system with incomplete detector coverage.

Bicolor K-edge spectral photon-counting CT imaging for the diagnosis of thoracic endoleaks: A dynamic phantom study.

Abstract: The purpose of this study was to investigate the feasibility of identifying and characterizing the three most common types of endoleaks within a thoracic aorta aneurysm model using bicolor K-edge imaging with a spectral photon-counting computing tomography (SPCCT) system in combination with a biphasic contrast agent injection. Three types of thoracic endoleaks (type 1, 2 and 3) were created in a dynamic anthropomorphic thoracic aorta phantom. Protocol consisted in an injection of an iodinated contrast material followed 80 seconds after an injection of a gadolinium-based contrast agent (GBCA). The phantom was scanned using a clinical prototype SPCCT during bicolor phase imaging consisting in an early distribution of GBCA and a late distribution of iodine. Conventional and spectral images were reconstructed for differentiating between the contrast agents and measuring their respective attenuation values and concentrations inside and outside the stent graft. Conventional images failed to provide specific dynamic imaging contrast agents in the aneurysmal sac and outside the stent graft while spectral images differentiated their specific distribution. In type 1 and 3 thoracic endoleaks, GBCA concentration was measured outside the stent graft at 6.1 ± 3.7 (standard deviation [SD]) mg/mL and 6.0 ± 4.0 (SD) mg/mL, respectively, in favor of an early blood flow. In type 2 thoracic endoleak, iodine was measured outside the stent graft at 24.3 ± 5.5 (SD) mg/mL in favor of a late blood flow in the aneurysmal sac. Bicolor K-edge imaging enabled SPCCT allows a bicolor characterization of thoracic aorta endoleaks in a single acquisition in combination with a biphasic contrast agent injection.

Virtual monochromatic images for coronary artery imaging with a spectral photon-counting CT in comparison to dual-layer CT systems: a phantom and a preliminary human study

Abstract: Abstract Objectives To evaluate the quality of virtual monochromatic images (VMIs) from spectral photon-counting CT (SPCCT) and two energy-integrating detector dual-energy CT (EID-DECT) scanners from the same manufacturer, for the coronary lumen. Methods A 21-cm section of the Mercury v4.0 phantom was scanned using a cardiac CT protocol. VMIs from 40 to 90 keV were reconstructed using high-resolution (HR) parameters for EID-DECT and SPCCT (CB and HRB kernels at 0.67 mm slice thickness, respectively). Ultra-high-resolution (UHR) parameters were used in addition to SPCCT (detailed-2 kernel, 0.43 mm slice thickness). Noise-power-spectrum (NPS), task-based transfer function (TTF), and detectability index ( d′ ) were computed for 2-mm-diameter lumen detection. In consensus, two radiologists analyzed the quality of the images from 8 patients who underwent coronary CTA on both CT systems. Results For all keV images, f peak , f 50 , and d′ were higher with SPCCT. The f peak and f 50 were higher with UHR-SPCCT with greater noise and lower d′ compared to those of the HR-SPCCT images. Noise magnitude was constant for all energy levels (keV) with both systems, and lower with HR images, and d′ decreased as keV decreased. Subjective analysis showed greater lumen sharpness and overall quality for HR and UHR-SPCCT images using all keV, with a greater difference at low keV compared to HR-EID-DECT images. Conclusion HR and UHR-SPCCT images gave greater detectability of the coronary lumen for 40 to 90 keV VMIs compared to two EID-DECT systems, with benefits of higher lumen sharpness and overall quality. Key Points • Compared with 2 dual-energy CT systems, spectral photon-counting CT (SPCCT) improved spatial resolution, noise texture, noise magnitude, and detectability of the coronary lumen. • Use of ultra-high-resolution parameters with SPCCT improved spatial resolution and noise texture and provided high detectability of the coronary lumen, despite an increase in noise magnitude. • In eight patients, radiologists found greater overall image quality with SPCCT for all virtual monochromatic images with a greater difference at low keV, compared with dual-energy CT systems.

Photon Counting Detector CT-Based Virtual Noniodine Reconstruction Algorithm for In Vitro and In Vivo Coronary Artery Calcium Scoring: Impact of Virtual Monoenergetic and Quantum Iterative Reconstructions

Abstract: Objectives The aim of this study was to evaluate the impact of virtual monoenergetic imaging (VMI) and quantum iterative reconstruction (QIR) on the accuracy of coronary artery calcium scoring (CACS) using a virtual noniodine (VNI) reconstruction algorithm on a first-generation, clinical, photon counting detector computed tomography system. Materials and Methods Coronary artery calcium scoring was evaluated in an anthropomorphic chest phantom simulating 3 different patient sizes by using 2 extension rings (small: 300 × 200 mm, medium: 350 × 250 mm, large: 400 × 300 mm) and in patients (n = 61; final analyses only in patients with coronary calcifications [n = 34; 65.4 ± 10.0 years; 73.5% male]), who underwent nonenhanced and contrast-enhanced, electrocardiogram-gated, cardiac computed tomography on a photon counting detector system. Phantom and patient data were reconstructed using a VNI reconstruction algorithm at different VMI (55–80 keV) and QIR (strength 1–4) levels (CACSVNI). True noncontrast (TNC) scans at 70 keV and QIR “off” were used as reference for phantom and patient studies (CACSTNC). Results In vitro and in vivo CACSVNI showed strong correlation (r > 0.9, P < 0.001 for all) and excellent agreement (intraclass correlation coefficient > 0.9 for all) with CACSTNC at all investigated VMI and QIR levels. Phantom and patient CACSVNI significantly increased with decreasing keV levels (in vitro: from 475.2 ± 26.3 at 80 keV up to 652.5 ± 42.2 at 55 keV; in vivo: from 142.5 [7.4/737.7] at 80 keV up to 248.1 [31.2/1144] at 55 keV; P < 0.001 for all), resulting in an overestimation of CACSVNI at 55 keV compared with CACSTNC at 70 keV in some cases (in vitro: 625.8 ± 24.4; in vivo: 225.4 [35.1/959.7]). In vitro CACS increased with rising QIR at low keV. In vivo scores were significantly higher at QIR 1 compared with QIR 4 only at 60 and 80 keV (60 keV: 220.3 [29.6–1060] vs 219.5 [23.7/1048]; 80 keV: 152.0 [12.0/735.6] vs 142.5 [7.4/737.7]; P < 0.001). CACSVNI was closest to CACSTNC at 60 keV, QIR 2 (+0.1%) in the small; 55 keV, QIR 1 (±0%) in the medium; 55 keV, QIR 4 (−0.1%) in the large phantom; and at 60 keV, QIR 1 (−2.3%) in patients. Conclusions Virtual monoenergetic imaging reconstructions have a significant impact on CACSVNI. The effects of different QIR levels are less consistent and seem to depend on several individual conditions, which should be further investigated.

An X-Ray C-Arm Guided Automatic Targeting System for Histotripsy

Abstract: Histotripsy is an emerging noninvasive, nonionizing and nonthermal focal cancer therapy that is highly precise and can create a treatment zone of virtually any size and shape. Current histotripsy systems rely on ultrasound imaging to target lesions. However, deep or isoechoic targets obstructed by bowel gas or bone can often not be treated safely using ultrasound imaging alone. This work presents an alternative x-ray C-arm based targeting approach and a fully automated robotic targeting system.The approach uses conventional cone beam CT (CBCT) images to localize the target lesion and 2D fluoroscopy to determine the 3D position and orientation of the histotripsy transducer relative to the C-arm. The proposed pose estimation uses a digital model and deep learning-based feature segmentation to estimate the transducer focal point relative to the CBCT coordinate system. Additionally, the integrated robotic arm was calibrated to the C-arm by estimating the transducer pose for four preprogrammed transducer orientations and positions. The calibrated system can then automatically position the transducer such that the focal point aligns with any target selected in a CBCT image.The accuracy of the proposed targeting approach was evaluated in phantom studies, where the selected target location was compared to the center of the spherical ablation zones in post-treatment CBCTs. The mean and standard deviation of the Euclidean distance was 1.4 ±0.5 mm. The mean absolute error of the predicted treatment radius was 0.5 ±0.5 mm.CBCT-based histotripsy targeting enables accurate and fully automated treatment without ultrasound guidance.The proposed approach could considerably decrease operator dependency and enable treatment of tumors not visible under ultrasound.

A Surgical Robotic Framework for Safe and Autonomous Data-Driven Learning and Manipulation of an Unknown Deformable Tissue With an Integrated Critical Space

Abstract: Aside from reliable robotic hardware and sensing technologies, to successfully transition from teleoperation to an autonomous and safe minimally invasive robotic surgery on unknown Deformable Tissues (U-DTs), various challenges need to be simultaneously considered and tackled to ensure safety and accuracy of the procedure. These challenges mainly include but are not limited to online modeling and reliable tracking of a U-DT with integrated critical tissues as well as development of reliable and fast control algorithms to enable safe, accurate, and autonomous surgical procedures. To collectively and simultaneously address these challenges and toward performing an autonomous and safe minimally invasive robotic surgery in a confined environment, in this paper, we present a surgical robotic framework with (i) real-time vision-based detection algorithm based on a Convolutional Neural Network (CNN) architecture that enables tracking the time-varying deformation of a critical tissue located within a U-DT and (ii) a complementary data-driven adaptive constrained optimization approach that learns deformation behavior of a U-DT while autonomously manipulating it within a time-varying constrained environment defined based on the output of the CNN detection algorithm. To thoroughly evaluate the performance of the proposed framework, we used the da Vinci Research Kit (dVRK) and performed various experiments on a custom-designed U-DT phantom with an arbitrary deformable vessel embedded within the phantom’s body (serving as the U-DT’s integrated critical space). Various experiments were conducted and analyzed to demonstrate the performance of the proposed framework and ensure robustness and safety while performing an autonomous surgical procedure.

Detectability of Small Low-Attenuation Lesions With Deep Learning CT Image Reconstruction: A 24-Reader Phantom Study

Abstract: Detectability of Small Low-Attenuation Lesions With Deep Learning CT Image Reconstruction: A 24-Reader Phantom StudyGiuseppe V. Toia, MD, MS1, David A. Zamora, MS2, Michael Singleton, PhD3, Arthur Liu, MS4, Edward Tan, BS4, Shuai Leng, PhD5, William P. Shuman, MD2, Kalpana M. Kanal, PhD2 and Achille Mileto, MD5Audio Available | Share Claim CREDIT

Comparison of image quality of two versions of deep-learning image reconstruction algorithm on a rapid kV-switching CT: a phantom study

Abstract: Abstract Background To assess the impact of the new version of a deep learning (DL) spectral reconstruction on image quality of virtual monoenergetic images (VMIs) for contrast-enhanced abdominal computed tomography in the rapid kV-switching platform. Methods Two phantoms were scanned with a rapid kV-switching CT using abdomen-pelvic CT examination parameters at dose of 12.6 mGy. Images were reconstructed using two versions of DL spectral reconstruction algorithms (DLSR V1 and V2) for three reconstruction levels. The noise power spectrum (NSP) and task-based transfer function at 50% (TTF 50 ) were computed at 40/50/60/70 keV. A detectability index (d') was calculated for enhanced lesions at low iodine concentrations: 2, 1, and 0.5 mg/mL. Results The noise magnitude was significantly lower with DLSR V2 compared to DLSR V1 for energy levels between 40 and 60 keV by -36.5% ± 1.4% (mean ± standard deviation) for the standard level. The average NPS frequencies increased significantly with DLSR V2 by 23.7% ± 4.2% for the standard level. The highest difference in TTF 50 was observed at the mild level with a significant increase of 61.7% ± 11.8% over 40−60 keV energy with DLSR V2. The d' values were significantly higher for DLSR V2 versus DLSR V1. Conclusions The DLSR V2 improves image quality and detectability of low iodine concentrations in VMIs compared to DLSR V1. This suggests a great potential of DLSR V2 to reduce iodined contrast doses.

Low dose pediatric chest computed tomography on a photon counting detector system – initial clinical experience

Abstract: With the clinical release of a photon counting detector-based computed tomography (CT) system, the potential benefits of this new technology need to be evaluated clinically. Literature concerning this new generation of detector is sparse, especially in the field of pediatric radiology. Therefore, this study outlines our initial experience with ultra-low dose chest CT imaging on the new photon counting CT system.A pediatric phantom (1-year old, CIRS ATOM phantom, model 704 [CIRS-computerized imaging reference system, Norfolk, VA]) was scanned at different dose levels and different image quality levels to define a protocol for clinical examinations. Next, 20 consecutive pediatric non-contrast ultra-low dose chest CT examinations were evaluated for radiation dose and diagnostic image quality using a 4-point Likert-scale-1 = excellent, 4 = bad image quality-by two radiologists in a consensus reading. This retrospective analysis was approved by the local research ethics committee.Chest CT examinations performed at ultra-low radiation dose (effective dose 0.19 ± 0.07 mSv; size-specific dose estimate 0.45 ± 0.14 mGy) in pediatric patients ages (2.6 ± 1.8 years) show good to excellent image quality for lung structures (1.4 ± 0.4) and moderate image quality for soft tissue structures (2.8 ± 0.2).Pediatric ultra-low dose chest CT examinations are feasible with the new generation photon counting detector-based CT system. The benefits of this technology must be evaluated for pediatric patients from the outset.

A Hybrid Mock Circulatory Loop for Fluid Dynamic Characterization of 3D Anatomical Phantoms

Abstract: This work presents the development of a Hybrid Mock Circulatory Loop (HMCL) to simulate hemodynamics at patient-specific level in terms of both 3D geometry and inlet/outlet boundary conditions.Clinical data have been processed to define the morphological and functional patient-specific settings. A piston pump is used to impose a parametric flow rate profile at the inlet of the hemodynamic circuit. In order to guarantee the physiological pressure and flow conditions, a specific hybrid chamber system including a real-time control has been designed and implemented. The developed system was validated firstly in a single outlet branch model and, secondly, on a 3D printed patient-specific multi-branch phantom. Finally, for the 3D phantom, the outlet flow profiles were compared with the corresponding in-vivo flow data.Results showed that the root mean squared error between the prescribed setpoint and the measured pressures was always below 3 mmHg (about 2.5%) for all cases. The obtained flow profiles for the patient-specific model were in agreement with the related functional in-vivo data.The capability to reproduce physiological hemodynamics condition, with high-fidelity, plays a significant role in the cardiovascular research. The developed platform can be used to assess the performances of cardiovascular devices, to validate numerical simulations, and to test imaging systems.

Adaptive Wall Shear Stress Imaging in Phantoms, Simulations and In Vivo

Abstract: WSS measurement is challenging since it requires sensitive flow measurements at a distance close to the wall. The aim of this study is to develop an ultrasound imaging technique which combines vector flow imaging with an unsupervised data clustering approach that automatically detects the region close to the wall with optimally linear flow profile, to provide direct and robust WSS estimation. The proposed technique was evaluated in phantoms, mimicking normal and atherosclerotic vessels, and spatially registered Fluid Structure Interaction (FSI) simulations. A relative error of 6.7% and 19.8% was obtained for peak systolic (WSS _PS ) and end diastolic (WSS _ED ) WSS in the straight phantom, while in the stenotic phantom, a good similarity was found between measured and simulated WSS distribution, with a correlation coefficient, R, of 0.89 and 0.85 for WSS _PS and WSS _ED , respectively. Moreover, the feasibility of the technique to detect pre-clinical atherosclerosis was tested in an atherosclerotic swine model. Six swines were fed atherogenic diet, while their left carotid artery was ligated in order to disturb flow patterns. Ligated arterial segments that were exposed to low WSS _PS and WSS characterized by high frequency oscillations at baseline, developed either moderately or highly stenotic plaques (p < 0.05). Finally, feasibility of the technique was demonstrated in normal and atherosclerotic human subjects. Atherosclerotic carotid arteries with low stenosis had lower WSS _PS as compared to control subjects (p < 0.01), while in one subject with high stenosis, elevated WSS was found on an arterial segment, which coincided with plaque rupture site, as determined through histological examination.

Mn5+ Lifetime‐Based Thermal Imaging in the Optical Transparency Windows Through Skin‐Mimicking Tissue Phantom

Abstract: Lifetime‐based luminescence thermometry has been shown to enable accurate deep‐tissue monitoring of temperature changes – even at the in vivo level – in a minimally invasive way. However, major limiting factors to the performance of this approach are short lifetimes and poor brightness. These are characteristics, respectively, of semiconductor nanocrystals and lanthanide‐doped nanoparticles, of which most luminescent nanothermometers are made. To address these limitations, the composition of luminescent nanothermometers co‐doped with transition metal (Mn5+) and Er3+ ions are designed and optimized. The salient features of these nanothermometers are strong, near‐infrared emission and long, temperature‐dependent photoluminescence lifetime. The potential of these luminescent nanophosphors for thermal sensing is then showcased by monitoring a thermal gradient using a one‐of‐a‐kind piece of equipment designed for lifetime‐based luminescence thermometry measurements. The combination of the newly developed nanothermometers and the custom‐made instrument allows for obtaining 2D thermal maps both in the absence and presence of tissue phantoms mimicking the optical properties of the skin. The results presented in this study thus provide credible foundations for the deployment of lifetime‐based thermometry for accurate deep‐tissue thermal mapping at the preclinical level.

Lateral Strain Imaging Using Self-Supervised and Physically Inspired Constraints in Unsupervised Regularized Elastography

Abstract: Convolutional Neural Networks (CNN) have shown promising results for displacement estimation in UltraSound Elastography (USE). Many modifications have been proposed to improve the displacement estimation of CNNs for USE in the axial direction. However, the lateral strain, which is essential in several downstream tasks such as the inverse problem of elasticity imaging, remains a challenge. The lateral strain estimation is complicated since the motion and the sampling frequency in this direction are substantially lower than the axial one, and a lack of carrier signal in this direction. In computer vision applications, the axial and the lateral motions are independent. In contrast, the tissue motion pattern in USE is governed by laws of physics which link the axial and lateral displacements. In this paper, inspired by Hooke’s law, we, first propose Physically Inspired ConsTraint for Unsupervised Regularized Elastography (PICTURE), where we impose a constraint on the Effective Poisson’s ratio (EPR) to improve the lateral strain estimation. In the next step, we propose self-supervised PICTURE (sPICTURE) to further enhance the strain image estimation. Extensive experiments on simulation, experimental phantom and in vivo data demonstrate that the proposed methods estimate accurate axial and lateral strain maps.

A Slotted Patch Antenna Design and Analysis for Detecting Breast Cancer

Abstract: Breast cancer, a common and deadly cancer for woman, is gradually increasing each year. Magnetic resonance imaging, mammography, tomography, ultrasound, and biopsy are some of the medical technologies that can be used to identify breast cancer. However, none of them are as simple and effective as a microwave imaging (MI) technique. MI is a non-ionizing, non-invasive, tumor-sensitive, low-cost approach. The performance of MI is primarily determined by the antenna employed in the system. Here, we propose a new partial ground plane and slots-based miniature patch antenna designed for breast tumor detection within the FCC's authorized range (3.1 GHz – 10.6 GHz). The dimension of this antenna is 30 × 20 mm2. High-frequency structure simulator (HFSS) software is used to design a breast phantom with and without a tumor, and the antenna is separately simulated on both the tumored and tumor-free breast phantoms. The presence of a tumor within the breast is clearly depicted by the changes in return loss, VSWR, current density, electric field, and magnetic field strengths. The findings demonstrate that the proposed antenna is a suitable sensor which can detect a very tiny breast tumor (2 mm) due to its compact size and broad bandwidth.

Determination of scattered radiation dose for radiological staff during portable chest examinations of COVID-19 patients

Abstract: The COVID-19 pandemic has resulted in a large increase in the number of patients admitted to hospitals. Radiological technologists (RTs) are often required to perform portable chest X-ray radiography on these patients. Normally, when performing a portable X-ray, radiation protection equipment is critical as it reduces the scatter radiation dose to hospital workers. However, during the pandemic, the use of a lead shield caused a heavy weight burden on workers who were responsible for a large number of patients. This study aimed to investigate scatter radiation doses received at various distances, directions, and positions. Radiation measurements were performed using the PBU-60 whole body phantom to determine scatter radiation doses at 100-200 cm and eight different angles around the phantom. The tests were conducted with and without lead shielding. Additionally, the doses were compared using the paired t test (p < 0.005) to determine suitable positions for workers who did not wear lead protection that adhered to radiation safety requirements. Scatter radiation doses of all 40 tests showed a highest and lowest value of 1285.5 nGy at 100 cm in the anteroposterior (AP) semi upright position and 134.7 nGy at 200 cm in the prone position, respectively. Correlation analysis between the dosimeter measurement and calculated inverse square law showed good correlation, with an R2 value of 0.99. Without lead shielding, RTs must stay at a distance greater than 200 cm from patients for both vertical and horizontal beams to minimize scatter exposure. This would allow for an alternative way of performing portable chest radiography for COVID-19 patients without requiring lead shielding.

Impact of γ factor in the penalty function of Bayesian penalized likelihood reconstruction (Q.Clear) to achieve high-resolution PET images

Abstract: The Bayesian penalized likelihood PET reconstruction (BPL) algorithm, Q.Clear (GE Healthcare), has recently been clinically applied to clinical image reconstruction. The BPL includes a relative difference penalty (RDP) as a penalty function. The β value that controls the behavior of RDP determines the global strength of noise suppression, whereas the γ factor in RDP controls the degree of edge preservation. The present study aimed to assess the effects of various γ factors in RDP on the ability to detect sub-centimeter lesions.All PET data were acquired for 10 min using a Discovery MI PET/CT system (GE Healthcare). We used a NEMA IEC body phantom containing spheres with inner diameters of 10, 13, 17, 22, 28 and 37 mm and 4.0, 5.0, 6.2, 7.9, 10 and 13 mm. The target-to-background ratio of the phantom was 4:1, and the background activity concentration was 5.3 kBq/mL. We also evaluated cold spheres containing only non-radioactive water with the same background activity concentration. All images were reconstructed using BPL + time of flight (TOF). The ranges of β values and γ factors in BPL were 50-600 and 2-20, respectively. We reconstructed PET images using the Duetto toolbox for MATLAB software. We calculated the % hot contrast recovery coefficient (CRChot) of each hot sphere, the cold CRC (CRCcold) of each cold sphere, the background variability (BV) and residual lung error (LE). We measured the full width at half maximum (FWHM) of the micro hollow hot spheres ≤ 13 mm to assess spatial resolution on the reconstructed PET images.The CRChot and CRCcold for different β values and γ factors depended on the size of the small spheres. The CRChot, CRCcold and BV increased along with the γ factor. A 6.2-mm hot sphere was obvious in BPL as lower β values and higher γ factors, whereas γ factors ≥ 10 resulted in images with increased background noise. The FWHM became smaller when the γ factor increased.High and low γ factors, respectively, preserved the edges of reconstructed PET images and promoted image smoothing. The BPL with a γ factor above the default value in Q.Clear (γ factor = 2) generated high-resolution PET images, although image noise slightly diverged. Optimizing the β value and the γ factor in BPL enabled the detection of lesions ≤ 6.2 mm.

Validate your white matter tractography algorithms with a reappraised ISMRM 2015 Tractography Challenge scoring system

Abstract: Abstract Since 2015, research groups have sought to produce the ne plus ultra of tractography algorithms using the ISMRM 2015 Tractography Challenge as evaluation. In particular, since 2017, machine learning has made its entrance into the tractography world. The ISMRM 2015 Tractography Challenge is the most used phantom during tractography validation, although it contains limitations. Here, we offer a new scoring system for this phantom, where segmentation of the bundles is now based on manually defined regions of interest rather than on bundle recognition. Bundles are now more reliably segmented, offering more representative metrics for future users. New code is available online. Scores of the initial 96 submissions to the challenge are updated. Overall, conclusions from the 2015 challenge are confirmed with the new scoring, but individual tractogram scores have changed, and the data is much improved at the bundle- and streamline-level. This work also led to the production of a ground truth tractogram with less broken or looping streamlines and of an example of processed data, all available on the Tractometer website. This enhanced scoring system and new data should continue helping researchers develop and evaluate the next generation of tractography techniques.

Experimental Evaluation of a 3-D CZT Imaging Spectrometer for Potential Use in Compton-Enhanced PET Imaging

Abstract: We constructed a prototype positron emission tomography (PET) system and experimentally evaluated large-volume 3-D cadmium zinc telluride (CZT) detectors for potential use in Compton-enhanced PET imaging. The CZT spectrometer offers sub-0.5-mm spatial resolution, an ultrahigh energy resolution (~1% @ 511 keV), and the capability of detecting multiple gamma-ray interactions that simultaneously occurred. The system consists of four CZT detector panels with a detection area of around 4.4 cm $\times$ 4.4 cm. The distance between the front surfaces of the two opposite CZT detector panels is ~80 mm. This system allows us to detect coincident annihilation photons and Compton interactions inside the detectors and then, exploit Compton kinematics to predict the first Compton interaction site and reject chance coincidences. We have developed a numerical integration technique to model the near-field Compton response that incorporates Doppler broadening, detector’s finite resolutions, and the distance between the first and second interactions. This method was used to effectively reject random and scattered coincidence events. In the preliminary imaging studies, we have used point sources, line sources, a custom-designed resolution phantom, and a commercial image quality (IQ) phantom to demonstrate an imaging resolution of approximately 0.75 mm in PET images, and Compton-based enhancement.

A self-biased, low-frequency, miniaturized magnetoelectric antenna for implantable medical device applications

Abstract: Low-frequency (LF) magnetoelectric (ME) antennas are of great importance in implantable medical device (IMD) applications compared to their electromagnetic (EM) counterparts as they can potentially offer appropriate size miniaturization and lower path loss and higher efficiency. In this work, a self-biased, miniaturized LF ME antenna is proposed, which operates at its electromechanical resonant frequency of 49.9 kHz, with the size scaled down to only 1.75 mm3, which is significantly smaller than that of a comparable EM antenna. The proposed antenna that constitutes of a piezoelectric layer sandwiched between two magnetostrictive layers is characterized in both air and an optimized three-layered human tissue-mimicking phantom media to demonstrate the potential applications in deep-body communications. The near field radiation pattern of the ME antenna is measured experimentally. The maximum received power obtained at a distance of 1.2 m in air and phantom media is 20 and 8 nW, respectively. The proposed antenna has significantly lower path loss of 0.57 dB/m as compared to its higher frequency counterparts. Due to the lower path loss and smaller size, the proposed ME antenna can be suitable in several miniaturized IMD applications.

A Drop-in Gamma Probe for Minimally Invasive Sentinel Lymph Node Dissection in Prostate Cancer

Abstract: Purpose This study evaluated the performance of a drop-in gamma probe for prostate cancer (PCa) sentinel lymph node dissection (SLND) in a pelvic phantom, porcine model, and in PCa patients as part of an ongoing prospective multicenter clinical trial. Methods Two design variants of the drop-in gamma probe (SENSEI; Lightpoint Medical Ltd) were assessed in the pelvic phantom, and the preferred design was evaluated in a porcine model with clinically representative volumes and 99mTc activities. In the clinical trial, radical prostatectomy, SLND, and extended pelvic lymph node dissection were performed the day after 99mTc-nanocolloid injection and imaging. Sentinel lymph nodes (SLNs) were detected with the drop-in probe and a rigid laparoscopic gamma probe (RLGP). An interim analysis was performed after 10 patients were recruited. Results The narrow field of view probe design outperformed the wide field of view design in the pelvic phantom (detection rate, 100% vs 50%). In the porcine model, all activity concentrations could be successfully detected. The drop-in gamma probe successfully detected SLNs in all 10 patients (detection rate, 100%). Two of the SLNs identified by the drop-in gamma probe could not be found with the RLGP. No false-negative cases and no adverse events related to the SLND procedure or the drop-in gamma probe occurred. Conclusion The drop-in gamma probe meets the usability and performance requirements for SLND in PCa and provides performance advantages over the RLGP. The final clinical study results will confirm the performance of the technique across multiple sites.

A Sub-Pixel Accurate Quantification of Joint Space Narrowing Progression in Rheumatoid Arthritis

Abstract: Rheumatoid arthritis (RA) is a chronic autoimmune disease that primarily affects peripheral synovial joints, like fingers, wrists and feet. Radiology plays a critical role in the diagnosis and monitoring of RA. Limited by the current spatial resolution of radiographic imaging, joint space narrowing (JSN) progression of RA for the same reason above can be less than one pixel per year with universal spatial resolution. Insensitive monitoring of JSN can hinder the radiologist/rheumatologist from making a proper and timely clinical judgment. In this paper, we propose a novel and sensitive method that we call partial image phase-only correlation which aims to automatically quantify JSN progression in the early RA. The majority of the current literature utilizes the mean error, root-mean-square deviation and standard deviation to report the accuracy at pixel level. Our work measures JSN progression between a baseline and its follow-up finger joint images by using the phase spectrum in the frequency domain. Using this study, the mean error can be reduced to 0.0130 mm when applied to phantom radiographs with ground truth, and 0.0519 mm standard deviation for clinical radiography. With the sub-pixel accuracy far beyond usual manual measurements, we are optimistic that the proposed work is a promising scheme for automatically quantifying JSN progression.