Ultrasound Computed Tomography Research Articles

Optimal transport assisted full waveform inversion for multiparameter imaging of soft tissues in ultrasound computed tomography

Ultrasound computed tomography (USCT) has emerged as a promising platform for imaging tissue properties, offering non-ionizing and operator-independent capabilities. In this work, we demonstrate the feasibility of obtaining quantitative images of multiple acoustic parameters (sound speed and impedance) for soft tissues using full waveform inversion (FWI), which are justified with both numerical and experimental cases. A 3D reconstruction based on a series of 2D slice images is presented for the experimental case of ex vivo soft tissues. To improve the robustness of the reconstruction process, a hierarchical FWI strategy is adopted, gradually iterating from low to high frequencies. In parallel, we employ a graph-space optimal transport misfit function, avoiding convergence into local minima and minimizing inversion artifacts caused by skin-related supercritical reflections. Our method first carries out sound speed inversion based on transmitted waves in the low and middle frequency bands, and then uses all types of waves in the high frequency band for simultaneous inversion of both sound speed and impedance. Compared to conventional strategies, the proposed approach can accurately reconstruct physical models consistent with the actual soft tissue sample. These high-resolution ultrasound images of acoustic parameters are promising to allow for quantitative differentiation among different types of tissues (e.g., muscles and fats). These results have significant implications for advancing our understanding of tissue properties and for potentially contributing to disease diagnosis through USCT, which is a flexible and cost-effective alternative to X-ray computed tomography or magnetic resonance imaging at no significant sacrifices for resolution.

Investigating the Use of Traveltime and Reflection Tomography for Deep Learning-Based Sound-Speed Estimation in Ultrasound Computed Tomography.

Ultrasound computed tomography (USCT) quantifies acoustic tissue properties such as the speed-of-sound (SOS). Although full-waveform inversion (FWI) is an effective method for accurate SOS reconstruction, it can be computationally challenging for large-scale problems. Deep learning-based image-to-image learned reconstruction (IILR) methods can offer computationally efficient alternatives. This study investigates the impact of the chosen input modalities on IILR methods for high-resolution SOS reconstruction in USCT. The selected modalities are traveltime tomography (TT) and reflection tomography (RT), which produce a low-resolution SOS map and a reflectivity map, respectively. These modalities have been chosen for their lower computational cost relative to FWI and their capacity to provide complementary information: TT offers a direct SOS measure, while RT reveals tissue boundary information. Systematic analyses were facilitated by employing a virtual USCT imaging system with anatomically realistic numerical breast phantoms. Within this testbed, a supervised convolutional neural network (CNN) was trained to map dual-channel (TT and RT images) to a high-resolution SOS map. Single-input CNNs were trained separately using inputs from each modality alone (TT or RT) for comparison. The accuracy of the methods was systematically assessed using normalized root mean squared error (NRMSE), structural similarity index measure (SSIM), and peak signal-to-noise ratio (PSNR). For tumor detection performance, receiver operating characteristic analysis was employed. The dual-channel IILR method was also tested on clinical human breast data. Ensemble average of the NRMSE, SSIM, and PSNR evaluated on this clinical dataset were 0.2355, 0.8845, and 28.33 dB, respectively.

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.

Envelope Inversion with Source encoding for Ultrasound Computed Tomography

Abstract Ultrasound computed tomography (USCT) is a noninvasive and non-ionizing imaging technique for soft tissue and limb bones. Full waveform inversion (FWI) has received increased interest due to its high resolution. The difficulties in FWI are twofold: high computational burden and poor convergence. To address these issues, an envelope inversion with source coding (EI-SE) algorithm is proposed in this paper. The envelope-based objective function measures the matching degree between the predicted and measured envelopes. It can provide the low-frequency components of the signal that are not available to FWI. Therefore, the EI can provide an accurate solution even when the initial model is far from the ground truth and low-frequency data are missing. The simulations are conducted to demonstrate the validity of the proposed algorithm. The root mean squared error (RMSE) of the proposed algorithm is much smaller than that of conventional FWI. The results show that EI-SE is effective in avoiding cycle skipping.

Sound speed imaging of cortical bone and soft tissue based on frequency-domain ultrasound waveform tomography

Abstract As one of the ultrasound computed tomography (UCT) algorithms, full-waveform inversion (FWI) can recover clear and detailed internal structures of bones by iteratively minimizing the misfit between observed and numerical data. However, time domain full-waveform inversion (TDFWI) often lacks sufficient low-frequency information, and the computation of full-time data imposes a significant computational burden. Besides, there are few studies on whole-medium reconstruction that jointly invert the bone and surrounding soft tissues. In this study, an FWI-based frequency-domain UCT (FD-UCT) is utilized for simultaneously imaging the sound speed of bones and soft tissues, which facilitates the inversion efficiency while ensuring the existence of low-frequency information. Simulated studies show that the FD-UCT can both reconstruct bones with large acoustic impedance and distinguish subtle impedance differences within soft tissues to reveal lesions.

Incremental high power radiofrequency ablation with multi-electrodes for small hepatocellular carcinoma: a prospective study

Radiofrequency ablation (RFA) offers a minimally invasive treatment for small hepatocellular carcinoma (HCC), but it faces challenges such as high local recurrence rates. This prospective study, conducted from January 2020 to July 2022, evaluated a novel approach using a three-channel, dual radiofrequency (RF) generator with separable clustered electrodes to improve RFA’s efficacy and safety. The study employed a high-power, gradual, stepwise RFA method on HCCs (≤ 4 cm), utilizing real-time ultrasound-computed tomography (CT)/magnetic resonance imaging (MRI) fusion imaging. Involving 110 participants with 116 HCCs, the study reported no major complications. Local tumor progression (LTP) and intrahepatic remote recurrence (IRR) rates were low, with promising cumulative incidences at 1, 2, and 3 years for LTP (0.9%, 3.6%, 7.0%) and IRR (13.9%, 20.5%, 31.4%). Recurrence-free survival (RFS) rates were similarly encouraging: LTP (99.1%, 96.4%, 93.0%) and IRR (86.1%, 79.5%, 68.6%). This innovative gradual, incremental high-power RFA technique, featuring a dual switching monopolar mode and three electrodes, represents an effective and safer management option for small HCCs.Trial registrationclinicaltrial.gov identifier: NCT05397860, first registered on 26/05/2022.

Three-dimensional trans-rectal and trans-abdominal ultrasound image fusion for the guidance of gynecologic brachytherapy procedures: a proof of concept study

High dose-rate brachytherapy is a treatment technique for gynecologic cancers where intracavitary applicators are placed within the patient’s pelvic cavity. To ensure accurate radiation delivery, localization of the applicator at the time of insertion is vital. This study proposes a novel method for acquiring, registering, and fusing three-dimensional (3D) trans-abdominal and 3D trans-rectal ultrasound (US) images for visualization of the pelvic anatomy and applicators during gynecologic brachytherapy. The workflow was validated using custom multi-modal pelvic phantoms and demonstrated during two patient procedures. Experiments were performed for three types of intracavitary applicators: ring-and-tandem, ring-and-tandem with interstitial needles, and tandem-and-ovoids. Fused 3D US images were registered to magnetic resonance (MR) and computed tomography (CT) images for validation. The target registration error (TRE) and fiducial localization error (FLE) were calculated to quantify the accuracy of our fusion technique. For both phantom and patient images, TRE and FLE across all modality registrations (3D US versus MR or CT) resulted in mean ± standard deviation of 4.01 ± 1.01 mm and 0.43 ± 0.24 mm, respectively. This work indicates proof of concept for conducting further clinical studies leveraging 3D US imaging as an accurate, accessible alternative to advanced modalities for localizing brachytherapy applicators.

Real-world efficacy of a teriparatide biosimilar (RGB-10) compared with reference teriparatide on bone mineral density, trabecular bone score, and bone parameters assessed using quantitative ultrasound, 3D-SHAPER® and high-resolution peripheral computer tomography in postmenopausal women with osteoporosis and very high fracture risk.

To compare the therapeutic efficacy of a teriparatide biosimilar (RGB-10) with reference teriparatide for the treatment of osteoporosis in postmenopausal women at very high fracture risk. A retrospective analysis of 25 postmenopausal female patients treated for osteoporosis with RGB-10 for 24months and a matched cohort of 25 patients treated with reference teriparatide. The following outcomes were assessed at baseline, 12 and 24months: bone mineral density (BMD) at the lumbar spine, femoral neck and total hip using dual-energy x-ray absorptiometry (DXA) and integral, trabecular and cortical volumetric and surface BMD using 3D-SHAPER® imaging, trabecular bone score (TBS), quantitative ultrasound (QUS) measurements, and high-resolution peripheral quantitative computed tomography (HRpQCT) imaging of the radius and tibia. No significant differences were observed between treatment groups in any of the measured parameters of BMD or bone health at baseline as well as in any timepoint when assessed using these various diagnostic methods. Both compounds provided equivalent significant improvements from baseline in measures of osteoporosis and fracture risk. The results of the analysis demonstrate the therapeutic equivalence of the teriparatide biosimilar (RGB-10) to reference teriparatide for the treatment of osteoporosis in postmenopausal women at very high risk of fracture.

Cross-correlation adjustment full-waveform inversion with source encoding in ultrasound computed tomography

Full-waveform inversion (FWI) is one of the leading-edge techniques in ultrasound computed tomography (USCT). FWI reconstructs the images of sound speed by iteratively minimizing the difference between the predicted and measured signals. The challenges of FWI are to improve its stability and reduce its computational cost. In this paper, a new USCT algorithm based on cross-correlation adjustment FWI with source encoding (CCAFWI-SE) is proposed. In this algorithm, the gradient is adjusted using the intermediate signals as the inversion target rather than the measured signals during iteration. The intermediate signals are generated using the travel time difference calculated by cross-correlation. In the case of conventional FWI failure, using the proposed algorithm, the estimated sound speed can converge toward the ground truth. To reduce the computational cost, an intermittent update strategy is implemented. This strategy only requires one time for the calculation of the travel time difference per stage, so that the source encoding can be used. Simulation and laboratory experiments are implemented to validate this approach. The experiment results show it has successfully recovered the sound speed model, while conventional FWI failed when the initial model greatly differed from the ground truth. This verifies that our approach improves the stability of the reconstruction in USCT. In practice, additional computational costs can be reduced by combining our approach with existing methods. The proposed approach increases the robustness of the FWI and expands its application.

Assessment of real-time US-CT/MR-guided percutaneous gold fiducial marker implementation in malignant hepatic tumors for stereotactic body radiation therapy

Backgrounds/Aims: This study explored the initial institutional experience of using gold fiducial markers for stereotactic body radiotherapy (SBRT) in treating malignant hepatic tumors using real-time ultrasound-computed tomography (CT)/magnetic resonance (MR) imaging fusion-guided percutaneous placement.Methods: From May 2021 to August 2023, 19 patients with 25 liver tumors that were invisible on pre-contrast CT received fiducial markers following these guidelines. Postprocedural scans were used to confirm their placement. We assessed technical and clinical success rates and monitored complications. The implantation of fiducial markers facilitating adequate treatment prior to SBRT, which was achieved in 96% of the cases (24 of 25 tumors), was considered technical success. Clinical success was the successful completion of SBRT without evidence of marker displacement and was achieved in 88% of cases (22 of 25 tumors). Complications included one major subcapsular hematoma and marker migration into the right atrium in two cases, which prevented SBRT.Results: Among the treated tumors, 20 of 24 (83.3%) showed a complete response, three of 24 (12.5%) remained stable, and one of 24 (4.2%) progressed during an average 11.7-month follow-up (range, 2-32 months).Conclusions: This study confirms that percutaneous gold fiducial marker placement using real-time CT/MR guidance is effective and safe for SBRT in hepatic tumors, but warns of marker migration risks, especially near the hepatic veins and in subcapsular locations. Using fewer markers than traditionally recommended-typically two per patient, the outcomes were still satisfactory, particularly given the increased risk of migration when markers were placed near major hepatic veins.

Ultrasound Carotid Plaque Score and Severity of Coronary Artery Disease Assessed by Computed Tomography Angiography in Patients with Arterial Hypertension.

The aim of the study was to assess the relationship between the presence of atherosclerotic lesions in the carotid arteries detected by ultrasound and the occurrence of atherosclerosis in the coronary arteries determined by computed tomography (CT) in patients with arterial hypertension (HTA). A total of 83 patients with HTA were qualified for the study (age: 71.3 ± 8.5 years). All subjects underwent carotid arteries ultrasound and coronary arteries CT. The carotid plaque score was assessed using ultrasound. The studied group was divided into two subgroups: a subgroup with the carotid plaque score ≤ 1 (A) and a subgroup with carotid plaque score ≥2 (B). Coronary arteries CT assessed coronary artery calcium score (CACS) and degree of coronary stenosis based on CAD-RADS. In subgroup B, a significantly higher CACS (411.3 ± 70.1 vs. 93.5 ± 31.8) and significantly higher grade in the CAD-RADS classification were demonstrated than in subgroup A (CAD-RADS ≥ 3: 21.8 vs. 6.0%). The regression analysis showed that carotid plaque score and age are independent risk factors for the severity of atherosclerotic lesions in the coronary arteries. In summary, ultrasound assessment of the carotid plaque score in patients with HTA could be considered as surrogate indicator of the risk and severity of atherosclerotic changes in the coronary arteries, but further studies are necessary to corroborate these results.

Full waveform inversion using frequency shift envelope-based global correlation norm for ultrasound computed tomography

Many studies have been carried out on ultrasound computed tomography (USCT) for its ability to offer quantitative measurements of tissue sound speed. Full waveform inversion (FWI) is a technique for reconstructing high-resolution sound speed images by iteratively minimizing the difference between the observed ultrasound data and the synthetic data based on the waveform equation. However, FWI suffers from cycle-skipping, which usually causes FWI convergence at a local minimum. Cycle-skipping occurs when the phase difference between the observed data and the synthetic data exceeds half a cycle. The simplest way to avoid cycle-skipping is to use low-frequency information for reconstruction. Nevertheless, in imaging systems, the response bandwidth of the probe is limited, and reliable low-frequency information often exceeds the response band. Therefore, it is a challenge to perform FWI imaging and avoid cycle-skipping problems without low-frequency information. In this paper, we propose a frequency shift envelope-based global correlation norm (FSEGCN), where an artificial source wavelet with a lower frequency is adopted to calculate synthetic data. FSEGCN compared with FWI, envelope inversion (EI), global correlation norm (GCN), envelope-based global correlation norm (EGCN) through concentric circle phantom without low-frequency information. The experimental results demonstrated the capability of the proposed method to recover the sound speed close to the exact model in the absence of low-frequency information, whereas FWI, EI, GCN, and EGCN cannot. Experiments on phantoms of the human head and calf show that artificial source wavelets can reduce image artifacts and enhance reconstruction robustness, when original low-frequency information is absent.

Ultrasound Computed Tomography Reflection Imaging with Coherence-Factor Beamforming for Breast Tumor Early Detection

Breast cancer is a global health concern, emphasizing the need for early detection. However, current mammography struggles to effectively image dense breasts. Breast ultrasound can be an adjunctive method, but it is highly dependent on operator skill. Ultrasound computed tomography (USCT) reflection imaging provides high-quality 3D images, but often uses delay-and-sum (DAS) beamforming, which limits its image quality. This article proposes the integration of coherence-factor (CF) beamforming into ultrasound computed tomography (USCT) reflection imaging to enhance image quality. CF assesses the focus quality of beamforming by analyzing the signal coherence across different channels, assigning higher weights to high-quality focus points and thereby improving overall image quality. Numerical simulations and phantom experiments using our built USCT prototype were conducted to optimize the imaging parameters and assess and compare the image quality of CF and DAS beamforming. Numerical simulations demonstrated that CF beamforming can significantly enhance image quality. Phantom experiments with our prototype revealed that CF beamforming significantly improves image resolution (from 0.35 mm to 0.14 mm) and increases contrast ratio (from 24.54 dB to 63.28 dB). The integration of CF beamforming into USCT reflection imaging represents a substantial improvement in image quality, offering promise for enhanced breast cancer detection and imaging capabilities.

Rare-earth-based polymeric nanobubbles as tri-modal imaging contrast agent

Medical imaging plays an important role in providing sufficient guidance for disease diagnosis and treatment. Among them, multimodal contrast agents can combine with a variety of imaging technologies to obtain comprehensive information on the lesion. It is an important development direction of medical imaging for accurate diagnosis of most diseases. In this study, we have designed and prepared a novel nanocomposite (i.e. NaGdF4:Eu@PLGA NBs) by combining sulfur hexafluoride (SF6) loaded polylactic acid-co-glycolic acid (PLGA) nanobubbles (NBs) with NaGdF4:Eu nanoparticles (NPs), which is the first research work on the composite assembly of ultrasound contrast bubbles with rare earth nanomaterials. Results show that NaGdF4:Eu@PLGA NBs with a diameter of appropriately 220 nm had uniform size and good in vitro stability. Combined with PLGA NBs’ superior ultrasound (US) imaging characteristics and NaGdF4:Eu NPs’ excellent magnetic resonance imaging (MRI) and computed tomography (CT) imaging characteristics, NaGdF4:Eu@PLGA NBs have exhibited significant and long-term in vitro US imaging, MRI and CT tri-modal contrast enhancement capability. Taken together, NaGdF4:Eu@PLGA NBs have great potential to be utilized in biomedical applications of US/MRI/CT tri-modal imaging.

Stepped frequency ultrasound computed tomography with waveform inversion

Routine US (ultrasound) scans for breast imaging run on a conventional console suffer from machine and operator dependence and are subject to personal interpretation. Recently, the framework of USCT (ultrasound computed tomography) has emerged as a safe, powerful and operator independent alternative to diagnostic US scans and x-rays mammography. The most known systems employ one circular array or a combination of transmitters and receivers by exploiting reflection, diffraction and transmission data. These systems are based on a pulsed transmission. Following propagation in tissue, the signals are usually recorded with a direct RF sampling scheme and stored as digital time-series. Image reconstruction is performed in the frequency domain in the 400 kHz–1 MHz bandwidth over a limited number of discrete frequencies. In this paper, we propose a new architecture based on the stepped frequency continuous waveform (SFCW) principle. In this scheme, the transmission is a continuous one and the received waveforms undergo a homo-dyne stage. By sequentially transmitting single tones at different frequencies, data can be collected directly in the frequency domain at specific frequencies, with programmable frequency steps and with any desired SNR. We describe in detail the transmitter and the receiver paths and compare with a conventional pulsed USCT architecture. Finally, we highlight the benefits of a SFCW-USCT device and comment on SNR, absorbed power, data fidelity and data storage.

Diagnosis and treatment experience of atypical hepatic cystic echinococcosis type 1 at a tertiary center in China.

Some hydatid cysts of cystic echinococcosis type 1 (CE1) lack well-defined cyst walls or distinctive endocysts, making them difficult to differentiate from simple hepatic cysts. To investigate the diagnostic methods for atypical hepatic CE1 and the clinical efficacy of laparoscopic surgeries. The clinical data of 93 patients who had a history of visiting endemic areas of CE and were diagnosed with cystic liver lesions for the first time at the People's Hospital of Xinjiang Uygur Autonomous Region (China) from January 2018 to September 2023 were retrospectively analyzed. Clinical diagnoses were made based on findings from serum immunoglobulin tests for echinococcosis, routine abdominal ultrasound, high-frequency ultrasound, abdominal computed tomography (CT) scan, and laparoscopy. Subsequent to the treatments, these patients underwent reexaminations at the outpatient clinic until October 2023. The evaluations included the diagnostic precision of diverse examinations, the efficacy of surgical approaches, and the incidence of CE recurrence. All 93 patients were diagnosed with simple hepatic cysts by conventional abdominal ultrasound and abdominal CT scan. Among them, 16 patients were preoperatively diagnosed with atypical CE1, and 77 were diagnosed with simple hepatic cysts by high-frequency ultrasound. All the 16 patients preoperatively diagnosed with atypical CE1 underwent laparoscopy, of whom 14 patients were intraoperatively confirmed to have CE1, which was consistent with the postoperative pathological diagnosis, one patient was diagnosed with a mesothelial cyst of the liver, and the other was diagnosed with a hepatic cyst combined with local infection. Among the 77 patients who were preoperatively diagnosed with simple hepatic cysts, 4 received aspiration sclerotherapy of hepatic cysts, and 19 received laparoscopic fenestration. These patients were intraoperatively diagnosed with simple hepatic cysts. During the follow-up period, none of the 14 patients with CE1 experienced recurrence or implantation of hydatid scolices. One of the 77 patients was finally confirmed to have CE complicated with implantation to the right intercostal space. Abdominal high-frequency ultrasound can detect CE1 hydatid cysts. The laparoscopic technique serves as a more effective diagnostic and therapeutic tool for CE.

Learned Full Waveform Inversion Incorporating Task Information for Ultrasound Computed Tomography.

Ultrasound computed tomography (USCT) is an emerging imaging modality that holds great promise for breast imaging. Full-waveform inversion (FWI)-based image reconstruction methods incorporate accurate wave physics to produce high spatial resolution quantitative images of speed of sound or other acoustic properties of the breast tissues from USCT measurement data. However, the high computational cost of FWI reconstruction represents a significant burden for its widespread application in a clinical setting. The research reported here investigates the use of a convolutional neural network (CNN) to learn a mapping from USCT waveform data to speed of sound estimates. The CNN was trained using a supervised approach with a task-informed loss function aiming at preserving features of the image that are relevant to the detection of lesions. A large set of anatomically and physiologically realistic numerical breast phantoms (NBPs) and corresponding simulated USCT measurements was employed during training. Once trained, the CNN can perform real-time FWI image reconstruction from USCT waveform data. The performance of the proposed method was assessed and compared against FWI using a hold-out sample of 41 NBPs and corresponding USCT data. Accuracy was measured using relative mean square error (RMSE), structural self-similarity index measure (SSIM), and lesion detection performance (DICE score). This numerical experiment demonstrates that a supervised learning model can achieve accuracy comparable to FWI in terms of RMSE and SSIM, and better performance in terms of task performance, while significantly reducing computational time.

Early cancer screening surveillance in one medical center of China.

Cancer screening aims to detect and treat malignant lesions at an early stage and to prolong patients' lifetime. There is still a lack of effective cancer screening programs in China. We initiated a screening project in 2018 and this study presented the cancer screening status in China. We conducted a cross-sectional study in one cancer-care medical center of China. The screening program included routine blood tests, plasma tumor markers, gastric endoscopy, colonoscopy, ultrasound, and computed tomography (CT) scans. Screening results were presented as sensitivity, specificity and positive predictive values (PPVs). Twenty-three (1.46%) out of 1,576 participants were eventually diagnosed with malignant tumors or high-grade intraepithelial neoplasia (HGIN). A family history of malignancy (78.26% in diagnosed cancer and HGIN vs. 46.36% in the others) was the only statistically significant parameter associated with cancer detection (p = 0.002). None of the common tumor markers were associated with the cancers screened. Except for colonoscopy (50.00%) and ultrasound for renal cancer (66.67%), the sensitivities of most screening methods were 100%. The specificities of all the screening means were above 96%. Most PPVs ranged from 30-60%. We emphasized risk stratification for early cancer screening, such as a family history of cancer. The survey illustrated that gastric endoscopy, colonoscopy, ultrasound, and lung CT for early cancer screening had high specificity, reasonable sensitivity, and PPV. We anticipated this report would motivate larger-sample studies to estimate the risk-to-benefit ratio of cancer screening and urge the establishment of a native Chinese screening project and even guidelines.

Navigated ultrasound bronchoscopy with integrated positron emission tomography-A human feasibility study.

Patients suspected to have lung cancer, undergo endobronchial ultrasound bronchoscopy (EBUS) for the purpose of diagnosis and staging. For presumptive curable patients, the EBUS bronchoscopy is planned based on images and data from computed tomography (CT) images and positron emission tomography (PET). Our study aimed to evaluate the feasibility of a multimodal electromagnetic navigation platform for EBUS bronchoscopy, integrating ultrasound and segmented CT, and PET scan imaging data. The proof-of-concept study included patients with suspected lung cancer and pathological mediastinal/hilar lymph nodes identified on both CT and PET scans. Images obtained from these two modalities were segmented to delineate target lymph nodes and then incorporated into the CustusX navigation platform. The EBUS bronchoscope was equipped with a sensor, calibrated, and affixed to a 3D printed click-on device positioned at the bronchoscope's tip. Navigation accuracy was measured postoperatively using ultrasound recordings. The study enrolled three patients, all presenting with suspected mediastinal lymph node metastasis (N1-3). All PET-positive lymph nodes were displayed in the navigation platform during the EBUS procedures. In total, five distinct lymph nodes were sampled, yielding malignant cells from three nodes and lymphocytes from the remaining two. The median accuracy of the navigation system was 7.7 mm. Our study introduces a feasible multimodal electromagnetic navigation platform that combines intraoperative ultrasound with preoperative segmented CT and PET imaging data for EBUS lymph node staging examinations. This innovative approach holds promise for enhancing the accuracy and effectiveness of EBUS procedures.

Ultrasound computed tomography image reconstruction with multi-mode aperture matching of ring array

Ultrasound computed tomography (USCT) imaging with a ring array holds significant potential for the inspection of small animals, breast tissue, and industrial components. Despite its promise, current techniques face challenges in terms of image quality. This paper presents a multi-mode aperture matching method for USCT image reconstruction with a ring array, aiming to enhance imaging performance. The proposed method utilizes a full ring transducer to transmit signals with a designated sub-aperture, while the receiving sub-aperture is adjusted based on the reference center element. By altering the transmitting and receiving sub-apertures under different conditions, specific imaging effects can be achieved. Experimental validation was conducted using a hair strand of 0.03 mm diameter placed at both center and eccentric positions within the ring array, in conjunction a breast phantom. Image resolution and contrast were assessed using full width at half maximum and contrast-to-noise ratio metrics. The results identified optimal transmitting and receiving sub-aperture matching modes for imaging the hair strand at various positions, and demonstrated the impact of this method on imaging targets at different positions within the breast phantom. These findings and experimental validations provide significant implications for enhancing imaging performance in USCT with a ring array.