[Application Research of Vector Flow Technique on Convex Array Ultrasonic Probe of Abdomen].

Vector flow imaging (VFI) is an innovative ultrasound flow measurement technology. Compared with the traditional color Doppler and spectral Doppler, VFI has the advantages of independence of angle correction and direct acquisition of real-time amplitude and direction of flow. Transverse oscillation (TO) method is one of the effective methods for vector flow imaging. However, a complete and detailed algorithm validation process based on commercial ultrasound machines is still lacking due to more complex convex probes. This study starts with introducing the imaging process and principle of transverse oscillation vector flow technique, and calculates the error between the set velocity value and the measured velocity value through the simulation experiment, and verifies the error between the set velocity value and the measured velocity value through the Doppler flow phantom experiment. Among them, the velocity value measured by the TO vector flow technique in the simulation experiment is 0.48 m/s and the preset value is 0.50 m/s, the error between them is -4%. The velocity values are 8.33, 11.14, 14.44 and 16.67 cm/s measured by the Doppler flow phantom experiment, the actual velocity values are 7.97, 10.78, 14.06 and 17.34 cm/s, the errors between them are all within ±5%. Both experiments verify the feasibility of using vector flow technique on abdominal convex probe.

Synovial Oxygenation at Photoacoustic Imaging to Assess Rheumatoid Arthritis Disease Activity.

Background Synovial hypoxia is a hallmark of rheumatoid arthritis (RA). Photoacoustic (PA) imaging, based on the use of laser-generated US, can detect the oxygenation status of tissue in individuals with RA. However, large studies are lacking, with few investigating the correlation between oxygenation status and disease activity. Purpose To measure synovial oxygenation status in participants with RA by using a multimodal PA US imaging system and to determine the correlation between PA imaging-measured oxygen saturation (SO2) and disease activity. Materials and Methods In this prospective observational cohort study, multimodal PA US imaging examinations were performed on small joints of consecutive participants with RA, who were treated at two outpatient rheumatology clinics from 2019 to 2021, and healthy controls. The SO2 values of the synovium were measured with dual-wavelength PA imaging and classified into three categories-hyperoxia, intermediate oxygenation status, or hypoxia-based on the signal coloration and clustering analysis of the SO2 values. The correlations of oxygenation status with power Doppler US (PDUS) scoring and clinical disease activity index were evaluated with one-way analysis of variance and the Kruskal-Wallis test with Bonferroni correction. Results A total of 118 participants with RA (median age, 55 years [IQR, 41-62 years]; 92 women) and 15 healthy control participants (median age, 37 years [IQR, 33-41 years]; 11 women) were included. The wrist synovium was categorized as hyperoxic in 36 participants with RA, of intermediate oxygenation status in 48 participants, and hypoxic in 34 participants. All control participants had hyperoxic synovial tissues. For participants with RA, hyperoxic synovium had more affluent Doppler US-depicted vasculature than those with hypoxia and intermediate oxygenation status (mean PDUS grade: hyperoxia, 2.7 ± 0.6 [SD]; intermediate, 1.3 ± 0.7; hypoxia, 1.1 ± 0.8; P < .001). Participants with intermediate status synovium had a lower clinical disease activity index than those with hypoxia (intermediate, 11.0 [IQR, 5.0-21.5] vs hypoxia, 26.0 [IQR, 18.0-39.0]; P = .001). Conclusion Photoacoustic imaging-detected hypoxia in thickened synovium correlated with less vascularization and higher disease activity in participants with rheumatoid arthritis. Clinical trial registration no. NCT04297475 © RSNA, 2022 Online supplemental material is available for this article.

[Research Progress on Vector Flow Imaging of Cardiac Ultrasound].

Echocardiogram is vital for the diagnosis of cardiac disease. The heart has complex hemodynamics requiring an advanced ultrasound imaging mode. Cardiac ultrasound vector flow imaging is capable of measuring the actual magnitude and direction of the blood flow velocity, obtaining the quantitative parameters of hemodynamics, and then providing more information for clinical research and diagnosis. This study mainly reviewed several different vector flow imaging techniques for cardiac flow and presented the implementation difficulties, and proposed a diverging wave based high frame rate cardiac ultrasound vector flow imaging. The study discussed the limitation of current ultrasound technology used in the cardiac flow measurement, analyzed and demonstrated the specific reasons for these implementation difficulties and the potential future development.

[Calculation and Comparison of the Resistance Index Based on Vector Velocities and Correction Method Studies].

Resistance Index (RI) is one of the indicators for ultrasound evaluation of hemodynamic changes. The purpose of this study is to evaluate the reliability of V Flow, which is a new ultrasound examination, when calculating this index. Data were collected from six positions of the bilateral common carotid artery (CCA) at the beginning, middle, and end of 10 healthy volunteers. The result shows that the RI error between V Flow and PW is about 12%. After angle correction for PW results both the relative error and its variance is reduced. Based on V Flow, users can directly obtain the actual flow velocity without manually correcting the angle. In addition to RI, blood flow velocity angle at different times can be compared to more intuitively to understand the hemodynamic details.

Multimodal photoacoustic/ultrasonic imaging system: a promising imaging method for the evaluation of disease activity in rheumatoid arthritis.

OBJECTIVES: We aimed to assess the clinical value of multimodal photoacoustic/ultrasound (PA/US) articular imaging scores, a novel imaging method which can reflect the micro-vessels and oxygenation level of inflamed joints of rheumatoid arthritis (RA). METHODS: Seven small joints were examined by the PA/US imaging system. A 0-3 scoring system was used to semi-quantify the PA and power-Doppler (PD) signals, and the sums of PA and PD scores (PA-sum and PD-sum scores) of the seven joints were calculated. The relative oxygen saturation (SO2) values of the inflamed joints were measured and classified into 3 PA+SO2 patterns. The correlations between the PA/US imaging scores and the disease activity scores were assessed. RESULTS: Thirty-one patients of RA and a total of 217 joints were examined using the PA/US system. The PA-sum had high positive correlations with the standard clinical scores of RA (DAS28 [ESR] ρ = 0.754, DAS28 [CRP] ρ = 0.796, SDAI ρ = 0.836, CDAI ρ = 0.837, p < 0.001), which were superior to the PD-sum (DAS28 [ESR] ρ = 0.651, DAS28 [CRP] ρ = 0.676, SDAI ρ = 0.716, CDAI ρ = 0.709, p < 0.001). For the patients with high PA-sum scores, significant differences between hypoxia and hyperoxia were identified in pain visual analog score (p = 0.020) and patient's global assessment (p = 0.026). The PA+SO2 patterns presented moderate and high correlation with PGA (ρ = 0.477, p = 0.0077) and VAS pain score (ρ = 0.717, p < 0.001). CONCLUSION: The PA scores have significant correlations with standard clinical scores for RA, and the PA+SO2 patterns are also related with clinical scores that reflect pain severity. PA may have clinical potential in evaluating RA. KEY POINTS: • Multimodal photoacoustic/ultrasound imaging is a novel method to assess micro-vessels and oxygenation of local lesions. • Significant correlations between multimodal imaging parameters and clinical scores of RA patients were verified. • The multimodal PA/US system can provide objective imaging parameters, including PA scores of micro-vessels and relative SO2 value, as a supplementary to disease activity evaluation.

[Quantitative Ultrasound Measurements of Blood Flow Velocity and Turbulence].

The paper described the hemodynamics of blood flow based on fluid mechanics and its corresponding formulas, and revealed the limitation of blood flow velocity measurement for non-laminar flow when using the conventional pulse wave Doppler. The paper demonstrated the calculation of turbulence for blood flow based on velocity directions and quantified the turbulence according to the presented formulas. Two methods were introduced and the simulated results were analyzed. An example using real data based on ultrasound vector flow imaging for calculating the turbulence of blood flow was presented in the end.

Vector flow imaging techniques: An innovative ultrasonographic technique for the study of blood flow.

Doppler ultrasonography is routinely used to identify abnormal blood flow. Nevertheless, conventional Doppler can be used to determine only the axial component of blood flow velocity and is angle dependent. A new method of multidimensional angle-independent estimation of flow velocity, called Vector Flow Imaging (VFI), has been proposed. It quantitatively evaluates the true velocity vector's amplitude and direction at any location into a vessel and displays a more intuitive depiction of the flow movements. High frame rate VFI, based on plane wave imaging, allows a detailed dynamic visualization of complex flow by showing even transient events, otherwise undetectable. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 45:582-588, 2017.

Validation of photoacoustic/ultrasound dual imaging in evaluating blood oxygen saturation.

Photoacoustic imaging (PAI) was performed to evaluate oxygen saturation (sO2) of blood-mimicking phantoms, femoral arteries in beagles, and radial arteries in humans at various sO2 plateaus. The accuracy (root mean square error, RMSE) of PAI sO2 compared with reference sO2 was calculated. In blood-mimicking phantoms, PAI achieved an accuracy of 1.49% and a mean absolute error (MAE) of 1.09% within 25 mm depth, and good linearity (R = 0.968; p < 0.001) was obtained between PAI sO2 and reference sO2. In canine femoral arteries, PAI achieved an accuracy of 2.16% and an MAE of 1.58% within 8 mm depth (R = 0.965; p < 0.001). In human radial arteries, PAI achieved an accuracy of 3.97% and an MAE of 3.28% in depth from 4 to 14 mm (R = 0.892; p < 0.001). For PAI sO2 evaluation at different depths in healthy volunteers, the RMSE accuracy of PAI sO2 increased from 2.66% to 24.96% with depth increasing from 4 to 14 mm. Through the multiscale method, we confirmed the feasibility of the hand-held photoacoustic/ultrasound (PA/US) in evaluating sO2. These results demonstrate the potential clinical value of PAI in evaluating blood sO2. Consequently, protocols for verifying the feasibility of medical devices based on PAI may be established.

Functional photoacoustic/ultrasound imaging for the assessment of breast intraductal lesions: preliminary clinical findings.

This study aimed to identify features of breast intraductal lesions in photoacoustic/ultrasound (PA/US) imaging and compare PA/US with color Doppler flow/ultrasound (CDFI/US) in the evaluation of breast intraductal lesions. In the nine patients with 10 breast intraductal lesions and 8 patients with 8 benign lesions, total vessel scores evaluated from PA/US are significantly greater than those from CDFI/US (p=0.005). PA internal vessel scores and oxygen saturation (SO2) score are significantly increased in breast intraductal lesions than in benign lesions (p=0.016, p=0.006). With a cutoff PA score (sum of PA internal vessel score and SO2 score) of 2.5, we obtained a sensitivity of 90% and a specificity of 87.5% in differentiation of two groups. PA/US upgraded 40% of breast intraductal lesions, and downgraded 50% of benign lesions from the Breast Imaging Reporting and Data System grading results based on CDFI/US. PA/US functional imaging has the potential in differentiating breast intraductal lesions.

Ultra-microangiography in evaluating the disease activity of rheumatoid arthritis and enhancing the efficacy of ultrasonography: A preliminary study.

OBJECTIVE: Ultra-microangiography (UMA) is a novel Doppler technique that has high sensitivity for low-velocity blood flows. In this study, a distinctive imaging feature, penetrating blood vessels on the surface of eroded bones within the inflamed joints, was observed on UMA. We aimed to investigate the feasibility of UMA in assessing disease activity and identify the clinical value of the UMA feature for evaluating rheumatoid arthritis (RA). METHODS AND MATERIALS: Power-Doppler ultrasound (PDUS) and UMA were performed on small joints of RA patients. The semiquantitative scores of PDUS and UMA of the joints were assessed and compared. The UMA imaging feature of penetrating vessels on the surface of eroded bones was evaluated, and the patients were divided into three groups based on imaging features. (Group 1: no inflammatory signs; Group 2: inflammatory US features but no UMA features; and Group 3: detected UMA features). The correlations between the groups and clinical parameters were assessed. RESULTS: A total of 52 patients with RA were recruited, with 364 joints (MCP, PIP, MTP and wrist) scanned. Synovial blood vessel signals were detected for 68 by PDUS and for 93 by UMA (display rate of blood vessel signals: 18.68 % VS 25.55 %). UMA presented better display capability of blood vessels within the inflamed regions than that of PDUS in overall. Significant differences were detected in clinical scores (P < 0.0001 for DAS28 [ESR], DAS28 [CRP], SDAI, CDAI, CRP P = 0.0303, SJC P = 0.0059, and TJC P = 0.0423) between Group 2 and 3. Significant correlations between the groups and clinical parameters were also observed (DAS28 [ESR] ρ=0.750; DAS28 [CRP] ρ=0.762; SDAI ρ=0.778; CDAI ρ=0.773; CRP ρ= 0.524; SJC ρ=0.742; TJC ρ=0.693, P < 0.0001), indicating that the UMA feature was related to high disease activity. CONCLUSIONS: UMA can help enhance the detection rate of micro-vascularization. The UMA feature of the penetrating vessels on the surface of eroded bones is likely to be associated with severe disease activity.

Exploring the diagnostic value of photoacoustic imaging for breast cancer: the identification of regional photoacoustic signal differences of breast tumors.

We examined 14 benign and 26 malignant breast nodules by a handheld dual-modal PA/US imaging system and analyzed the data using the quantitative and semi-quantitative method. The PA signal spatial density and PA scores of different regions of the benign and malignant nodules were compared, and the diagnostic performances of two diagnostic methods based on PA parameters were evaluated. For both quantitative and semi-quantitative results, significant differences in the distributions of PA signals in different regions of benign and malignant breast lesions were identified. The PA parameters showed good performance in diagnosing breast cancer, indicating the potential of PAI in clinical utilization.

Multimodal VEGF-Targeted Contrast-Enhanced Ultrasound and Photoacoustic Imaging of Rats with Inflammatory Arthritis: Using Dye-VEGF-Antibody-Loaded Microbubbles.

Owing to the heavy health burdens from rheumatoid arthritis, a sensitive and objective imaging method is needed for early diagnosis and accurate evaluation of the disease. We aimed to fabricate vascular epithelial growth factor (VEGF)-targeted microbubbles (MBs) to evaluate the expression levels of VEGF within the inflammatory lesions of rats with adjuvant-induced arthritis (AIA) using a multimodal photoacoustic (PA)/ultrasound (US) imaging system. Fluorescein isothiocyanate-biotin double-labeled vascular endothelial growth factor receptor 2 antibodies and Cy5.5-biotin double-labeled VEGF2 antibodies were added to the avidin-labeled MBs to synthesize VEGF-targeted MBs. The antibodies could specifically bind to the MBs according to the flow cytometry and fluorescence imaging. In vitro experiments on the cellular uptake of the target MBs also validated the interaction of the VEGF antibodies and the MBs. Multimodal contrast-enhanced US (CEUS)/PA imaging was performed in sequence on the inflamed paws of the AIA rats with a single PA/US imaging system after the injection of the targeted MBs. The CEUS and PA signals were then quantified and verified by the pathologic results. A CEUS pattern of fast wash in and slow washout was observed in the AIA rats after injection of targeted MBs. Compared with AIA rats injected with unconnected VEGF antibodies and naked MBs, AIA rats injected with targeted MBs presented a higher peak intensity (p = 0.0079 and 0.0079 respectively) and a longer time to peak (p = 0.0117 and 0.0117, respectively). The PA signals were also significantly enhanced after injection of targeted MBs (p = 0.0112 and 0.0119, respectively), which was in accordance with the pathologic and immunohistochemical results. In conclusion, VEGF-targeted MBs can be used as agents for multimodal CEUS/PA imaging and to detect VEGF expression in the inflammatory lesions of AIA rats in vivo. This strategy may be useful in imaging evaluation of arthritis by identifying inflammation-related molecules in different imaging modes.

Quantitative analysis of breast tumours aided by three-dimensional photoacoustic/ultrasound functional imaging.

In this pilot study, we explored a quantitative method to analyse characteristics of breast tumours using 3D volumetric data obtained from a three-dimensional (3D) photoacoustic/ultrasound (PA/US) functional imaging system. Imaging results from 24 Asian patients with maximum tumour diameters less than 2 cm, including 8 benign tumours, 16 T1 stage invasive breast cancers (IBCs), and 22 normal breasts, were analysed. We found that the volumetric mean oxygenation saturation (SO2) in tumour regions of T1 stage IBCs was 7.7% lower than that of benign tumours (P = 0.016) and 3.9% lower than that of healthy breasts (P = 0.010). The volumetric mean SO2 in tumour surrounding regions of T1 stage IBCs was 4.9% lower than that of benign tumours (P = 0.009). For differentiating T1 stage IBCs and benign tumours, with a cut-off SO2 value of 78.2% inside tumours, we obtained a sensitivity of 100%, a specificity of 62.5%, and an AUC of 0.81; with a cut-off SO2 value of 77.9% in regions surrounding tumours, we obtained a sensitivity of 100%, a specificity of 75% and an AUC of 0.84. Our preliminary results demonstrate that 3D PA/US functional imaging has the potential to provide valuable quantitative physiological information that may be useful for the detection and evaluation of breast tumours.

3-D Contrast-Enhanced Ultrasound Fusion Imaging: A New Technique to Evaluate the Ablative Margin of Radiofrequency Ablation for Hepatocellular Carcinoma.

To investigate the feasibility of assessing the ablative margin (AM) of radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC) with 3-D contrast-enhanced ultrasound fusion imaging (3-DCEUS-FI), pre- and post-RFA 3-DCEUS images of 84 patients with HCC were fused for two radiologists to independently assess the AMs. The success rate, duration and influencing factors for registration; inter-observer agreement for AM classification; and local tumor progression (LTP) rate were evaluated. The success rate of the automatic registration (AR), which was completed within 4-12 s, was 57.1% (48/84). The duration and success rate of the interactive registration (IR) were 4.2 ± 1.8 min and 91.7% (77/84) for radiologist A and 4.8 ± 2.1 min and 91.7% (77/84) for radiologist B, respectively. The multivariate analysis demonstrated that the pre-RFA image quality, number of vessels (≥3 mm) and presence of acoustic shadow were independent factors for AR (p < 0.05), while the number of vessels was an independent factor for IR (p = 0.001). The agreement between observers was excellent (kappa = 0.914). LTP rate was significantly higher for AMs <5 mm than for AMs ≥5 mm (p = 0.024). Quantitatively evaluating the AM immediately after RFA for HCC with 3-DCEUS-FI was feasible.

Photoacoustic/ultrasound dual imaging of human thyroid cancers: an initial clinical study.

We reported an initial clinical study of in vivo human thyroid by a photoacoustic/ultrasound handheld probe. Our dual-modality system is based on a high-end clinical ultrasound machine. Both healthy and cancerous thyroids were imaged non-invasively, and we compared the photoacoustic imaging with color Doppler ultrasound. The results of photoacoustic thyroid imaging could reveal many blood vessels that were not sensitive for Doppler ultrasound. Our study demonstrated that photoacoustic imaging could provide important complementary information for traditional ultrasound thyroid examination, which has a great potential for clinical diagnosis.