Tomographic Ultrasound Imaging Research Articles

Imaging of ventilation and lung injury with low-frequency tomographic ultrasound.

Mechanical ventilation in the intensive care unit (ICU) is a life-saving technique for patients with acute respiratory failure, but is also associated with a high incidence of complications in the injured lung. Currently, there is no widely used monitoring technique to guide the ventilator setting to facilitate a precision medicine approach or to provide a real-time alert for developing adverse pulmonary conditions. Conventional ultrasound has been used as a thoracic bedside technology, but the lack of signal penetration into lung tissue results in images that often contain more information in their artifacts than in the images themselves. Perhaps the greatest obstacle to using traditional ultrasound in the ICU is the need for highly skilled technicians to perform the data collection. In contrast, low-frequency ultrasound (50-500 kHz) has been shown to penetrate the lung, and can detect air trapping in patients with chronic obstructive pulmonary disease (COPD). Here, we present a method of collecting low-frequency ultrasound computed tomographic (USCT) data in vivo on a mechanically ventilated porcine model and computing tomographic reconstructions of airflow during tidal breathing and induced lung injuries. We evaluate the ability of the novel low-frequency USCT system to image regional changes in sound speed in the thorax due to changes in airflow during tidal breathing and induced lung injuries. This represents the first study of low-frequency tomographic ultrasound imaging in vivo and the first to produce tomographic images of ventilatory changes invivo. USCT and computed tomography (CT) scan data were collected alternately on a mechanically ventilated Landrace pig weighing approximately 75 kg during tidal breathing, induced pneumothorax, atelectasis, and pleural effusion. The pneumothorax was induced by injecting air through a 5 mm thick intrathoracic tube inserted in the 8th posterior intercostal space. After removing the air, atelectasis was induced by ventilating the animal with a high concentration of oxygen and low tidal volumes. The pleural effusion was induced by injecting a saline solution through the tube. The USCT data were collected at 125 kHz using the USCT low-frequency ultrasound tomography (LUFT) system on a transducer belt placed around the animal's thorax. Tomographic reconstructions were computed from the USCT data using a regularized refraction-corrected Gauss-Newton-based time-of-flight reconstructionalgorithm. Cyclic changes in computed lung area during tidal breathing were demonstrated to agree with the respiratory rate on the mechanical ventilator. Reconstructed images computed at time steps during the procedure demonstrate regional changes consistent with what would be expected during the induced lung injury. No ground truth was available for images during the procedures since CT scans could only be taken before and after each established lunginjury. In this work, we have demonstrated in the first in vivo study using a mechanically ventilated porcine animal model that low-frequency ultrasound tomography has the ability to image regional changes in sound speed in the thorax corresponding to changes in airflow during tidal breathing and induced lung injury. The results show promise for using low-frequency USCT as a bedside imaging technique in the future for patients with acute respiratory distresssyndrome.

The use of non-invasive tomographic imaging to monitor lung condition

The development of ultrasound tomography (UST) aimed to significantly enhance the precision and safety of non-invasive UST imaging, particularly for studying crystallization processes in biological tissues. The initiative sought to address the limitations of previous versions by incorporating advanced technological upgrades and providing a more user-friendly interface. The revised system comprises eight four-channel measurement cards interconnected via a high-speed FD CAN bus capable of 8 MBPS data transfer. Each card features a dedicated square wave generator, band-pass filters tailored to specific ultrasonic transducer frequencies, and a sophisticated signal envelope processing unit. The core processing unit is built around a 32-bit STM32G474RE microcontroller, ensuring robust data handling and image reconstruction capabilities. The UST device presented demonstrates improved image clarity and reduced noise interference. The measurement card redesign has achieved a sampling rate of 4 MBPS per channel and includes a two-stage amplification for dynamic range management. Upgraded power components, comprehensive shielding, and the integration of advanced analog switches have led to an enhanced signal-to-noise ratio, pivotal for high-resolution imaging. The advancements presented in the UST device mark a noteworthy progression in ultrasound imaging technology, extending beyond traditional applications. High-speed data collection, precise signal processing, and user-centered design have all come together to make a system that can image crystallization processes more accurately and accurately over and over again.

Ultrasound and diffuse optical tomography-transformer model for assessing pathological complete response to neoadjuvant chemotherapy in breast cancer.

We evaluate the efficiency of integrating ultrasound (US) and diffuse optical tomography (DOT) images for predicting pathological complete response (pCR) to neoadjuvant chemotherapy (NAC) in breast cancer patients. The ultrasound-diffuse optical tomography (USDOT)-Transformer model represents a significant step toward accurate prediction of pCR, which is critical for personalized treatment planning. We aim to develop and assess the performance of the USDOT-Transformer model, which combines US and DOT images with tumor receptor biomarkers to predict the pCR of breast cancer patients under NAC. We developed the USDOT-Transformer model using a dual-input transformer to process co-registered US and DOT images along with tumor receptor biomarkers. Our dataset comprised imaging data from 60 patients at multiple time points during their chemotherapy treatment. We used fivefold cross-validation to assess the model's performance, comparing its results against a single modality of US or DOT. The USDOT-Transformer model demonstrated excellent predictive performance, with a mean area under the receiving characteristic curve of 0.96 (95%CI: 0.93 to 0.99) across the fivefold cross-validation. The integration of US and DOT images significantly enhanced the model's ability to predict pCR, outperforming models that relied on a single imaging modality (0.87 for US and 0.82 for DOT). This performance indicates the potential of advanced deep learning techniques and multimodal imaging data for improving the accuracy (ACC) of pCR prediction. The USDOT-Transformer model offers a promising non-invasive approach for predicting pCR to NAC in breast cancer patients. By leveraging the structural and functional information from US and DOT images, the model offers a faster and more reliable tool for personalized treatment planning. Future work will focus on expanding the dataset and refining the model to further improve its accuracy and generalizability.

Update on Placenta Accreta Spectrum Diagnosis and Management Challenges

Abstract: Placenta accreta spectrum (PAS) disorders, also known as morbidly adherent placenta (MAP) include anomalous adherence of the placenta to implantation location. : PAS could be classified into 3 categories based on the penetration distance of trophoblasts via the myometrium and serosa of the uterus into placenta accreta, increta, and percreta. : A recent study in 2020 showed that using the introduced model based on 3 parameters; uterovesical vascularity, unusual lacunae (grades 2 and 3), and bladder wall interruption, has 100% accuracy in the diagnosis of PAS. : Accurate diagnosis of morbidly adherent placenta (MAP), helps in multidisciplinary team management at delivery, with better maternal and neonatal outcomes. : PAS could be suspected early in pregnancy by recognizing women with doubted Cesarean scar pregnancy (CSP) because CSP in the first trimester and PAS in the second and third trimesters might denote various stages of a similar pathology. : Gray scale US with or without adding color Doppler and made by transabdominal or trans vaginal route are commonly utilized for prenatal screening and diagnosis of PAS. : In a recent study made by Alalfy et al. in 2021 they revealed the systematic combined approach with the use of Alalfy Simple Criteria for assessment of placenta previa and PAS using 3D TUI (Tomographic Ultrasound Imaging and 3D power Doppler has a high diagnostic value in the diagnosis of PAS from the non-adherent placenta, the estimation of the myometrial thickness and the depth of placental invasion with the determination of different PAS subgroup plus defining diffuse from focal invasion (Figs. 1 and 2).

1115 The Role of Ultrasound and Computer Tomography Imaging in the Management of Suspected Acute Appendicitis at a District General Hospital: A Clinical Audit Evaluating Our Practice Against International Standards

1115 The Role of Ultrasound and Computer Tomography Imaging in the Management of Suspected Acute Appendicitis at a District General Hospital: A Clinical Audit Evaluating Our Practice Against International Standards

Assessment of the Possibilities of Ultrasound Tomographic Imaging of Multi-Layer Composite Materials

Assessment of the Possibilities of Ultrasound Tomographic Imaging of Multi-Layer Composite Materials

Supercomputer Simulations in Designing Medical Ultrasound Tomographic Imaging Devices

Supercomputer Simulations in Designing Medical Ultrasound Tomographic Imaging Devices

Three-Dimensional Transperineal Ultrasound Assessment of the Anal Sphincter Immediately After Vaginal Birth: An Exploratory Study.

To assess the feasibility of acquiring adequate transperineal ultrasound (TPUS) volumes of the anal sphincter (AS) immediately after vaginal birth, the reproducibility of its measurements, and detecting defects therein. Secondary analysis of TPUS volumes of the AS, acquired immediately after vaginal birth with a transversely oriented convex probe. Two independent experts ranked off-line image quality as "inadequate," "adequate," or "ideal" using the Point-of-Care Ultrasound Image Quality scale. On "adequate" and "ideal" quality volumes, the length of the external AS at 6 and 12 o'clock, and the volume of the external and internal AS were measured. Additionally, volumes were screened for AS defects on tomographic ultrasound imaging. Subsequently, we rated the intra- and interrater agreement on those findings. Of 183 volumes, 162 were considered "adequate" or of "ideal" quality (88.5%). Reasons for "inadequacy" were shadow artifacts (16/21), poor resolution (3/21), incomplete acquisition (1/21), or aberrant AS morphology (1/21). The intrarater reliability of two-dimensional (2D) and three-dimensional (3D) measurements was excellent, whereas interrater reliability was fair to good for 2D measurements and good for 3D measurements. In those tomographic ultrasound imaging (TUI) sequences including AS defects, the intra- and interrater reliability of the defect measurement were excellent [intraclass correlation coefficient (ICC) = 0.92 (0.80-0.94)] and moderate [ICC = 0.72 (0.63-0.79)]. In this cohort, there were only few (4/48; 8.3%) AS defects. However, grading them was poorly reproducible between experts. TPUS of the AS immediately after vaginal birth yields adequate image quality and allows for reproducible measurements. In the few patients with AS defects, there was good agreement on the presence, but it was poor for the extent of defects.

Levator ani muscle avulsion and subsequent vaginal delivery: 8-year longitudinal follow-up.

To assess the evolution of levator ani muscle (LAM) avulsion from 1 year to 8 years after first delivery in women with and those without subsequent vaginal delivery. In addition, to assess whether women with full or partial avulsion 8 years after first delivery have larger LAM hiatal area and more symptoms of pelvic organ prolapse compared to women with normal LAM insertion. In this single-center longitudinal study, 195 women who were primiparous at the start of the study were included and underwent transperineal ultrasound examination 1 year and 8 years after first delivery. Muscle insertion was assessed by tomographic ultrasound imaging in the axial plane. Full LAM avulsion was defined as abnormal muscle insertion in all three central slices. Partial LAM avulsion was defined as abnormal muscle insertion in one or two central slices. Eight years after the first delivery, LAM hiatal area was assessed at rest, during maximum pelvic floor muscle contraction and on maximum Valsalva maneuver. To assess symptoms of pelvic organ prolapse, the vaginal symptoms module of the International Consultation on Incontinence Questionnaire was used. At 1-year follow-up, 25 (12.8%) women showed signs of LAM avulsion, of whom 20 fulfilled the sonographic criteria of full avulsion and five of partial avulsion. Eight years after the first delivery, 35 (17.9%) women were diagnosed with avulsion, of whom 25 were diagnosed with full avulsion and 10 with partial avulsion. No woman with partial or full avulsion at 1 year had improved avulsion status at the 8-year follow-up. Of the 150 women who had subsequent vaginal delivery, 21 (14.0%) women were diagnosed with partial or full LAM avulsion 1 year after first delivery, and 31 (20.7%) women were diagnosed with partial or full avulsion 8 years after first delivery. Of the 45 women without subsequent vaginal delivery, one woman with partial avulsion 1 year after first delivery was diagnosed with full avulsion at the 8-year follow-up. All women with full avulsion at 1-year follow-up were diagnosed with full avulsion at the 8-year follow-up regardless of whether they had subsequent vaginal delivery. At 8-year follow-up, women with full avulsion had statistically significantly larger LAM hiatal area compared to women with normal muscle insertion. Mean ± SD vaginal symptom scores ranged between 5.5 ± 5.7 and 6.0 ± 4.0 and vaginal symptom quality of life scores ranged between 0.9 ± 1.4 and 1.5 ± 2.2 and did not differ significantly between women with normal muscle insertion and women with partial or full avulsion at 8-year follow-up. More LAM avulsions were present 8 years compared with 1 year after first delivery in women with subsequent vaginal delivery. Except for one primipara, all women without subsequent vaginal delivery had unchanged LAM avulsion status between 1 year and 8 years after their first delivery. Larger LAM hiatal area was found in women with full avulsion compared to those with normal muscle insertion at 8-year follow-up. Vaginal symptoms scores were low and did not differ between women with normal muscle insertion and those with partial or full avulsion at 8-year follow-up. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Multimode ultrasound imaging of an anal canal gastrointestinal stromal tumour (GIST).

Gastrointestinal stromal tumours (GISTs) can develop throughout the entire gastrointestinal tract, but these tumours are usually found in the stomach and small intestine. In this case, a rare GIST arising from the anal canal was investigated using high-frequency endoanal ultrasound and external three-dimensional ultrasound with tomographic ultrasound imaging. The endoanal approach revealed the inner structure of the tumour. External ultrasound was used to determine the relationship between the lesion and surrounding tissues. In the limited reports of anal canal GISTs, no other lesions have been correctly diagnosed preoperatively or displayed in detail on imaging. The multilayer structure of the anal sphincter and these lesions can be clearly displayed by a variety of ultrasound imaging methods, which are nonradiative, low-cost and easily accessible.Modern ultrasound has the potential for broad application in anal canal tumour diagnosis and surveillance.

Coronal Plane Assessment for Levator Trauma.

Levator avulsion is a major etiological factor of pelvic organ prolapse (POP) and is primarily diagnosed on tomographic axial plane imaging. Two-dimensional imagingcan also image the levator. The objective was to test reproducibility and validity of coronal plane assessment for diagnosis of levator trauma by assessing the coronal plane obtained on tomographic ultrasound imaging. A retrospective study of women who had undergone an interview, POPQ and four-dimensional translabial ultrasound at a tertiary urogynecological unit. Post-processing of archived volume data was performed for assessment; and levator muscle area and estimate of remnant muscle mass in the coronal plane. Interobserver reproducibility of the latter two measures and associations between various measures of levator trauma and POP were tested. Interobserver agreement was good for percentage estimates (ICC 0.743), but fair for area measurements (ICC 0.482). Six hundred and twenty four women were seen, 468 (75%) had significant clinical prolapse. Full levator avulsions were diagnosed in 137 (22%). Mean TTS was 2.7 (range 0-12). On coronal plane assessment average muscle area was 1.47 (SD 0.76) cm2 and 1.55 (SD 0.74) cm2 on the right and left, respectively (P = .005). It was 76% and 79% for average estimates of muscle mass (P = .021). Both measures were strongly associated with POP; however, they were not superior to TTS in predicting POP. Coronal plane assessment in volume data is reproducible and valid for evaluation of levator trauma. Muscle mass estimate may be a better measure than muscle area.

Diagnostic value of TVS, 3.0TMRI, and tomographic ultrasound imaging in EP.

Diagnostic value of TVS, 3.0TMRI, and tomographic ultrasound imaging in EP.

Comparison of diagnostic values between 2D three-section ultrasound and 3D tomographic ultrasound imaging for fetal cleft palate at 11–13+6 weeks

ObjectiveTo assess diagnostic values of 2D three-section ultrasound including central sagittal section of the face, axial section of the superior alveolar process, and coronal section of the posterior triangle of the nose and 3D tomographic ultrasound imaging (TUI) in fetal cleft palate at 11–13+6 weeks. Methods21 cleft palate fetuses who were delivered or induced in our hospital from January 2018 to May 2021 were enrolled. All fetuses with cleft palate underwent nuchal translucency (NT) measurement and screening at 11–13+6 weeks. Relevant findings of cleft palate detected by 2D and 3D TUI during NT screening were retrospectively analyzed. The cleft palate detection rate was compared between two groups. ResultsThe detection rates of 3D TUI and 2D three-section ultrasound for cleft palate were 0.857 (18/21) and 0.810 (17/21), with no statistical significance (P > 0.05). The detection rates on triangular coronal section of the posterior nose were by 2-D three-section ultrasound was 81.0%, significantly higher than 52.3% (11/21) and 66.6% (14/21) on the central sagittal section and axial section of the superior alveolar process (both P < 0.05). ConclusionBoth 2D three-section ultrasound and 3D TUI yield high diagnostic value for cleft palate at 11–13+6 weeks. The detection rate of cleft palate on the coronal section of the posterior triangle of the nose by 2D three-section ultrasound is higher compared with those on the remaining two planes.

AI-Enhanced Analysis Reveals Impact of Maternal Diabetes on Subcutaneous Fat Mass in Fetuses without Growth Alterations.

Pregnant women with diabetes often present impaired fetal growth, which is less common if maternal diabetes is well-controlled. However, developing strategies to estimate fetal body composition beyond fetal growth that could better predict metabolic complications later in life is essential. This study aimed to evaluate subcutaneous fat tissue (femur and humerus) in fetuses with normal growth among pregnant women with well-controlled diabetes using a reproducible 3D-ultrasound tool and offline TUI (Tomographic Ultrasound Imaging) analysis. Additionally, three artificial intelligence classifier models were trained and validated to assess the clinical utility of the fetal subcutaneous fat measurement. A significantly larger subcutaneous fat area was found in three-femur and two-humerus selected segments of fetuses from women with diabetes compared to the healthy pregnant control group. The full classifier model that includes subcutaneous fat measure, gestational age, fetal weight, fetal abdominal circumference, maternal body mass index, and fetal weight percentile as variables, showed the best performance, with a detection rate of 70%, considering a false positive rate of 10%, and a positive predictive value of 82%. These findings provide valuable insights into the impact of maternal diabetes on fetal subcutaneous fat tissue as a variable independent of fetal growth.

Real-time 3-D reconstruction from multiple simultaneous ultrasound scans for enhanced imaging

Ultrasound imaging offers numerous benefits compared to other modalities, including portability, affordability, and real-time volumetric imaging capabilities. However, its limited field of view hinders image interpretation, significantly limiting its potential clinical applications. This study focuses on creating tomographic ultrasound imaging by automatically registering partially overlapping 3-D ultrasound volumes (coarsely localized in space). This approach can be used to gather a comprehensive field of view of the anatomical area imaged and to enhance the acquired image information. Potential applications involve both tomographic/wide-view imaging using conventional ultrasound probes and future technologies, where multiple ultrasound probes will be able to scan simultaneously the anatomy of interest. This work describes the development of advanced artificial intelligence and image analysis methods to create real-time 3-D anatomical reconstructions of a designated area of interest. Simultaneously (or quasi simultaneously) acquired ultrasound volumes with partial overlap can be spatially aligned using rigid registration, because they present geometrically similar information. We used novel supervised and unsupervised transformers and compared the results with more traditional methods such as mutual information and cross-correlation. This application contributes to creating new imaging processing techniques for ultrasound imaging and making this complex modality more user-friendly and clinically usable.

Vaginal wall thickness as potential biomarker of vaginal health. A proposal for standardized ultrasound measurement using three-dimensional transvaginal ultrasound.

Vaginal wall thickness could be used as a biomarker of vaginal health. We propose a standardized method using three-dimensional (3D) ultrasound for measuring vaginal wall thickness. Fill the vagina with gel. Insert the endovaginal transducer into the vagina up to the middle third. In the sagittal plane, visualizing the cervix and vaginal fornices, capture a 3D volume of the upper third of the vagina. Using tomographic ultrasound imaging function in the sagittal plane and the posterior vaginal fornix as the reference obtain at least three axial planes of the vagina, separated by 1 cm. Measure the vaginal wall thickness at a distance of 2 cm from the posterior vaginal fornix at 12, 3, 6, and 9 o'clock. The reproducibility of measurements was high. Measurements of vaginal wall thickness can be reliably performed.

Research progress in pelvic floor ultrasound for assessing the morphology and function of levator ani muscle in women.

Pelvic floor ultrasound can clearly visualize the position and morphology of pelvic floor organs, observe the pelvic organ prolapse in real-time, and quantify and analyze the degree of the levator ani muscle injury, which is the most common imaging method to assess the morphology and function of the levator ani muscle to date. The different ultrasound imaging techniques provide a variety of indicators, each with its own advantages and limitations.Furthermore, two-dimensional ultrasound is the basis of imaging, but it fails to detect cross-sectional images of the pelvic floor; three-dimensional ultrasound can acquire the axial plane of the levator hiatus; tomographic ultrasound imaging allows real-time observation of the levator ani muscle injury; shear wave elastography can provide a quantitative assessment of the contractility and elastic characteristics of the levator ani muscle in real-time. It is of great significance to summarize the basic principles of various ultrasound imaging techniques, summarize the ultrasound image characteristics of levator ani muscle and its hiatus in different populations and different states, and explore the cut-off values and diagnostic criteria-related ultrasound parameters for improving the diagnostic efficiency of pelvic floor ultrasound for levator ani muscle injury, leading to reducing missed diagnosis and misdiagnosis of lesions.

Abstract P3007: Rosuvastatin-eluting Gold-nanoparticle-loaded Perivascular Wrap For Enhanced Arteriovenous Fistula Maturation In A Murine Model

Background: Arteriovenous fistulas (AVFs) are a vital form of arteriovenous access for patients requiring hemodialysis, but they are linked to overall morbidity and mortality when they fail to mature. The most common cause of AVF non-maturation is neointimal hyperplasia (NIH). To minimize the effects of NIH, a perivascular wrap composed of polycaprolactone (PCL), rosuvastatin (ROSU), and gold nanoparticles (AuNPs) was created. Objectives: This study assessed the impact of ROSU-eluting, radiopaque resorbable perivascular wraps on pathologic NIH in a chronic kidney disease (CKD) rodent model of AVF. Methods: Electrospun PCL wraps containing AuNPs and/or ROSU were monitored for in vitro AuNP release, ROSU elution, and cell viability. The wraps were implanted around an AVF in a CKD rodent model for in vivo ultrasound (US) and micro-computed tomography (mCT) imaging. AVF specimens were collected for histological analyses. Results: Cell viability was preserved in the presence of both AuNP- and ROSU-containing wraps. In vitro release of ROSU and AuNPs correlated with in vivo findings of decreasing radiopacity on mCT over time. AuNP-loaded wraps had increased radiopacity compared with PCL-alone wraps and control AVFs without wraps. The addition of ROSU decreased US and histologic measurements of NIH. Conclusions: The reduced NIH seen with ROSU-loaded perivascular wraps suggests a synergistic effect between mechanical support and anti-hyperplasia medication. Furthermore, AuNP loading increased wrap radiopacity. Together, our results show that AuNP- and ROSU-loaded PCL wraps induce AVF maturation and suppress NIH while facilitating optimal implanted device visualization.

Ultrasound examination of the pelvic floor during active labor: A longitudinal cohort study.

There is limited evidence about changes in the pelvic floor during active labor. We aimed to investigate changes in hiatal dimensions during the active first stage of labor and associations with fetal descent and head position. We conducted a longitudinal, prospective cohort study at the National University Hospital of Iceland, from 2016 to 2018. Nulliparous women with spontaneous onset of labor, a single fetus in cephalic presentation, and gestational age ≥37 weeks were eligible. Fetal position was assessed with transabdominal ultrasound and fetal descent was measured with transperineal ultrasound. Three-dimensional volumes were acquired from transperineal scanning at the start of the active phase of labor and in late first stage or early second stage. The largest transverse hiatal diameter was measured in the plane of minimal hiatal dimensions. The levator urethral gap was measured as the distance between the center of the urethra and the levator insertion using tomographic ultrasound imaging. Measurements of the levator urethral gap were made in the plane of minimal hiatal dimensions and 2.5 and 5 mm cranial to this. The final study population comprised 78 women. The mean transverse hiatal diameter increased 12.4% between the two examinations, from 39.4 ± 4.1 mm (±standard deviation) at the first examination to 44.3 ± 5.8 mm at the last examination (p < 0.01). We found a moderate correlation between the transverse hiatal diameter and fetal station at the last examination (r = 0.44, r2 = 0.19; p < 0.01; regression equation y = 2.71 + 0.014x), and a weak correlation between the change in transverse hiatal diameter and change in fetal station (r = 0.29; r2 = 0.08; p = 0.01; regression equation y = 0.24 + 0.012x). Levator urethral gap increased significantly in all three planes on both the left and right sides. Head position was not associated with hiatal measurements after adjusting for fetal station. We found a significant, but only modest, increase of the hiatal dimensions during the first stage of labor. The risk of levator ani trauma will therefore be low during this stage. The change in transverse hiatal diameter was associated with fetal descent but not with head position.

Open-UST: An Open-Source Ultrasound Tomography Transducer Array System.

Fast imaging methods are needed to promote clinical adoption of ultrasound tomography (UST), and more widely available UST hardware could support the experimental validation of new measurement configurations. In this work, an open-source 256-element transducer ring array was developed (morganjroberts.github. io/open-UST) and manufactured using rapid prototyping, for only £2k. Novel manufacturing techniques were used, resulting in a 1.17° mean beam axis skew angle, a [Formula: see text] mean element position error, and a [Formula: see text] deviation in matching layer thickness. The nominal acoustic performance was measured using hydrophone scans and watershot data, and the 61.2 dB signal-to-noise ratio (SNR), 55.4° opening angle, 10.2 mm beamwidth, and 54% transmit-receive bandwidth (-12 dB) were found to be similar to existing systems and compatible with state-of-the-art full-waveform-inversion image reconstruction methods. The interelement variation in acoustic performance was typically < 10% without using normalization, meaning that the elements can be modeled identically during image reconstruction, removing the need for individual source definitions based on hydrophone measurements. Finally, data from a phantom experiment were successfully reconstructed. These results demonstrate that the open-UST system is accessible for users and is suitable for UST imaging research.