Clinical Ultrasound Imaging System Research Articles

Super‐resolution ultrasound localization microscopy for the non‐invasive imaging of human testicular microcirculation and its differential diagnosis role in male infertility

AbstractTesticular microcirculation is closely related to spermatogenic function and seminiferous tubular function. The diagnosis and monitoring of testicular diseases can be associated with testicular microcirculation; however, there are currently no effective non‐invasive methods for super‐resolution imaging of testicular microcirculation. In this study, we introduced state‐of‐the‐art graph‐based tracking with the Kalman motion model algorithm to non‐invasively image human testicular microcirculation for the first time with a regular frame‐rate clinical ultrasound imaging system (37 Hz). Two distinct testicular vessels with an 81 µm separation were resolved in the testicular vasculature, surpassing all other imaging modalities. In a retrospective study, we performed contrast‐enhanced ultrasound examinations(CEUS) and ultrasound localization microscopy (ULM) processing on the included 76 infertile patients and 15 healthy controls from August 2021 to May 2023 and obtained super‐resolution images of testicular microcirculation with sub‐diffraction resolution. Through the results of one‐way analysis of variance tests and receiver operating characteristic analyses, we found that the ULM‐based parameters hold promise as clinical guidance for differentiating between non‐obstructive and obstructive male infertility. The mean vessel diameter achieved an area under the curve (AUC) of 0.920 (95% confidence interval [CI]: 0.847–0.994, p < .001) with a cut‐off value of 170.9 µm in oligoasthenospermia, and an AUC of 0.952 (95% CI: 0.875–1.000, p < .001) with a cut‐off value of 169.9 µm in azoospermia patients, respectively, addressing a significant clinical challenge.

Panoramic volumetric clinical handheld photoacoustic and ultrasound imaging

Photoacoustic (PA) imaging has gained much attention, providing structural and functional information in combination with clinical ultrasound (US) imaging systems. 2D PA and US imaging is easily implemented, but its heavy dependence on operator skills makes 3D imaging preferable. In this study, we propose a panoramic volumetric clinical PA and US imaging system equipping a handheld imaging scanner weighing 600 g and measuring 70 × 62 × 110 mm3. Multiple PA/US scans were performed to cover a large field-of-view (FOV), and the acquired PA/US volumes were mosaic-stitched after manually correcting the positions and rotations in a total of 6 degrees of freedom. PA and US maximum amplitude projection images were visualized online, while spectral unmixed data was quantified offline. The performance of the system was tested via tissue-mimicking phantom experiments. The system’s potential was confirmed in vivo by panoramically imaging vascular networks in human arms and necks, with FOVs of 331 × 38 and 129 × 120 mm2, respectively. Further, we quantified hemoglobin oxygen saturation levels in the radial artery, brachial artery, carotid artery, and jugular vein. We hope that this system can be applied for various clinical fields such as cardiovascular imaging, dermatology, vascular surgery, internal medicine, and oncology.

Imaging-guided gene delivery: seeing is delivering

Imaging-guided gene delivery: seeing is delivering

Lactoferrin-Conjugated Polylactic Acid Nanobubbles Encapsulated Perfluoropentane as a Contrast Agent for Ultrasound/Magnetic Resonance Dual-Modality Imaging

The development of contrast agents that can be activated by multiple modes is of great significance for tumor diagnosis. In this study, the lactoferrin (Lf)-conjugated polylactic acid (PLLA) nanobubbles (Lf-PLLA NBs) were used to encapsulate liquid perfluoropentane (PFP) with the double emulsion method, creating PFP loaded (PFP/Lf-PLLA) NBs for the ultrasound/magnetic resonance dual-modality imaging of subcutaneous tumor. The particle diameter and stability of nanobubbles were investigated by photon correlation spectroscopy. The biocompatibility of nanobubbles was preliminarily evaluated by cell proliferation and migration assay, hemolysis rate, and blood biochemistry analysis. A B-mode clinical ultrasound real-time imaging system was used to perform ultrasonic imaging in vivo. Magnetic resonance imaging in vivo was applied with a clinical 3.0 T magnetic resonance imaging (MRI) scanner system. The mean particle diameter of PFP/Lf-PLLA NBs was 320.2 ± 4.1 nm with a low polydispersity index (PDI, 0.145 ± 0.025), and the NBs were negatively charged (−11.4 ± 0.4 mV). The transmission electron microscopy (TEM) results showed that PFP/Lf-PLLA NBs exhibited highly monodispersed and possessed an obvious spherical structure of nanocapsules. Nanobubbles had good stability at 4°C. Different concentrations of the PFP/Lf-PLLA NBs solution had no effect on the cell in cytotoxicity and cell migration, and the results of hemolysis rate and blood biochemistry assay also indicated the good biocompatibility of NBs. On the ultrasound/magnetic resonance imaging of tumor-bearing mice, PFP/Lf-PLLA NBs showed significantly enhanced contrast ability of tumor tissue. Therefore, PFP/Lf-PLLA NBs had great potential to be a contrast agent for tumor dual-modality imaging in vivo.

Construction of novel amphiphilic chitosan-polylactide graft copolymer nanodroplets for contrast enhanced ultrasound tumor imaging.

In this experiment, a new amphiphilic chitosan-poly(lactide) graft copolymer was synthesized and characterized by IR, 1H-NMR, XRD, TGA. The obtained chitosan-poly (lactide) graft copolymer was used as the matrix material to prepare nanodroplets (NDs) encapsulating with liquid PFP by double-emulsion and solvent evaporation method. The resulting NDs were characterized by photon correlation spectroscopy and transmission electron microscopy (TEM). The biocompatibility was explored by cytotoxicity assay, cell migration assay and blood biochemistry analysis. The experiments of ultrasonic imaging in vitro and in vivo were carried out with a B-mode clinical ultrasound imaging system. The results of FI-IR and 1H-NMR confirmed the successful grafting reaction of polylactic acid(PLLA) to chitosan with a graft rate of 365%. The average size of the NDs was 101.1 ± 2.7 nm, with the polydispersity index (PDI) of 0.127 ± 0.020, and the zeta potential was -31.8 ± 1.5 mV. From the TEM results, NDs were highly dispersed and had a spherical shape with a distinct capsule structure. The NDs exhibited good stability during storage at 4°C. The NDs solution with different concentrations did not affect cell growth and showed good biocompatibility in cytotoxicity, cell migration and blood biochemistry studies. Under the irradiation of ultrasonic waves, the NDs formed an ultrasonic high signal, which could significantly enhance the ultrasound imaging of tumor tissue in vivo. Taken together, the NDs hold great potential for ultrasound imaging as a nanosized contrast agent.

Hydrophone Spatial Averaging Correction for Acoustic Exposure Measurements From Arrays-Part I: Theory and Impact on Diagnostic Safety Indexes.

This article reports underestimation of mechanical index (MI) and nonscanned thermal index for bone near focus (TIB) due to hydrophone spatial averaging effects that occur during acoustic output measurements for clinical linear and phased arrays. TIB is the appropriate version of thermal index (TI) for fetal imaging after ten weeks from the last menstrual period according to the American Institute of Ultrasound in Medicine (AIUM). Spatial averaging is particularly troublesome for highly focused beams and nonlinear, nonscanned modes such as acoustic radiation force impulse (ARFI) and pulsed Doppler. MI and variants of TI (e.g., TIB), which are displayed in real-time during imaging, are often not corrected for hydrophone spatial averaging because a standardized method for doing so does not exist for linear and phased arrays. A novel analytic inverse-filter method to correct for spatial averaging for pressure waves from linear and phased arrays is derived in this article (Part I) and experimentally validated in a companion article (Part II). A simulation was developed to estimate potential spatial-averaging errors for typical clinical ultrasound imaging systems based on the theoretical inverse filter and specifications for 124 scanner/transducer combinations from the U.S. Food and Drug Administration (FDA) 510(k) database from 2015 to 2019. Specifications included center frequency, aperture size, acoustic output parameters, hydrophone geometrical sensitive element diameter, etc. Correction for hydrophone spatial averaging using the inverse filter suggests that maximally achievable values for MI, TIB, thermal dose ( t 43 ), and spatial-peak-temporal-average intensity ( [Formula: see text]) for typical clinical systems are potentially higher than uncorrected values by (means ± standard deviations) 9% ± 4% (ARFI MI), 19% ± 15% (ARFI TIB), 50% ± 41% (ARFI t 43 ), 43% ± 39% (ARFI [Formula: see text]), 7% ± 5% (pulsed Doppler MI), 15% ± 11% (pulsed Doppler TIB), 42% ± 31% (pulsed Doppler t 43 ), and 33% ± 27% (pulsed Doppler [Formula: see text]). These values correspond to frequencies of 3.2 ± 1.3 (ARFI) and 4.1 ± 1.4 MHz (pulsed Doppler), and the model predicts that they would increase with frequency. Inverse filtering for hydrophone spatial averaging significantly improves the accuracy of estimates of MI, TIB, t 43 , and [Formula: see text] for ARFI and pulsed Doppler signals.

Ultrasound-Responsive Nanoparticles for Continuous pH Sensing In Vivo

Ultrasound (US) is one of the most commonly used medical imaging techniques. Contrast agents are administered to patients to improve fidelity of US images and for theranostic applications. The majority of current research into US contrast agents relies on microbubbles containing a phospholipid shell surrounding a gaseous core, as this leads to high degree of echogenicity. However, these materials only last for 5-30 minutes in vivo due to diffusion of the gas into the bloodstream. To our knowledge, the combination of ultrasound technology and contrast agents to create in vivo biosensors has not yet been investigated. In this work we designed and produced a pH-sensitive US contrast agent based on core-shell materials. Here we used a silica scaffold coated with Layer-by-Layer (LbL) polymer as the dynamic component (Figure 1). We found that following encapsulation of the hybrid particle in a silica shell, pH changes induced polymer rigidity changes which could be detected using standard clinical and pre-clinical ultrasound imaging systems. Herein we will describe the material design and characterisation, gel phantom ultrasound studies, and real-time in vivo biosensing of pH in the live animal. Such biosensors could find application in biomedical research and clinical diagnostics in deep tissue, providing real-time information without relying on laboratory infrastructure or complex imaging systems.

Towards clinical photoacoustic and ultrasound imaging: Probe improvement and real-time graphical user interface.

Photoacoustic imaging is a non-invasive and non-ionizing biomedical technique that has been investigated widely for various clinical applications. By taking the advantages of conventional ultrasound imaging, hand-held operation with a linear array transducer should be favorable for successful clinical translation of photoacoustic imaging. In this paper, we present new key updates contributed to the previously developed real-time clinical photoacoustic and ultrasound imaging system for improving the clinical usability of the system. We developed a seamless image optimization platform, designed a real-time parameter control software with a user-friendly graphical user interface, performed Monte Carlo simulation of the optical fluence in the imaging plane, and optimized the geometry of the imaging probe. The updated system allows optimizing of all imaging parameters while continuously acquiring the photoacoustic and ultrasound images in real-time. The updated system has great potential to be used in a variety of clinical applications such as assessing the malignancy of thyroid cancer, breast cancer, and melanoma. Impact statement Photoacoustic imaging is a promising biomedical imaging modality that can visualize both structural and functional information of biological tissue. Because of its easiness to be integrated with conventional ultrasound imaging systems, numerous studies have been conducted to develop and apply clinical photoacoustic imaging systems. However, most of the systems were not suitable for general-purpose clinical applications due to one of the following reasons: target specific design, immobility, inaccessible operation sequence, and lack of hand-held operation. This study demonstrates a real-time clinical photoacoustic and ultrasound imaging system, which can overcome the limitations of the previous systems for successful clinical translation.

Quantitative assessment of cervical softening during pregnancy with shear wave elasticity imaging: an in vivo longitudinal study.

We report here the results of a longitudinal study of cervix stiffness during pregnancy. Thirty women, ages ranging from 19 to 37 years, were scanned with ultrasound at five time points beginning at their normal first-trimester screening (8-13 weeks) through term pregnancy (nominally 40 week) using a clinical ultrasound imaging system modified with a special ultrasound transducer and system software. The system estimated the shear wave speed (its square proportional to the shear modulus under idealized conditions) in the cervix. We found a constant fractional reduction (about 4% per week) in shear wave speed with increasing gestational age. We also demonstrated a spatial gradient in shear wave speed along the length of the cervix (softest at the distal end). Results were consistent with our previous ex vivo and in vivo work in women. Shear wave elasticity imaging may be a potentially useful clinical tool for objective assessment of cervical softening in pregnancy.

Noninvasive and quantitative measurement of C4d deposition for the diagnosis of antibody-mediated cardiac allograft rejection.

BackgroundC4d is a specific biomarker for the diagnosis of antibody-mediated rejection (AMR) after cardiac transplantation. Although strongly recommended, routine C4d surveillance is hindered by the invasive nature of endomyocardial biopsy. Targeted ultrasound (US) has high sensitivity, and C4d is abundantly expressed within the graft of patients experiencing AMR, which makes it possible to visualize C4d deposition in vivo using targeted US.MethodsWe designed a serial dilution of C4d-targeted microbubbles (MBC4d) using a streptavidin-biotin conjugation system. A rat model of AMR with C4d deposition was established by pre-sensitization with skin transplantation before cardiac transplantation. MBC4d were injected into recipients and then qualitatively and quantitatively analyzed using the destruction-replenishment method with a clinical US imaging system and analyzed by software.FindingsWe successfully obtained qualitative images of C4d deposition in a wide cardiac allograft section, which, for the first time, reflected real-time C4d distribution. Moreover, normal intensity difference was used for quantitative analysis and exhibited an almost nearly linear correlation with the grade of C4d deposition according to the pathologic evidence. In addition, MBC4d injection did not affect the survival and aggravate injury, which demonstrates its safety.InterpretationThis study demonstrates a noninvasive, quantitative and safe evaluation method for C4d. As contrast-enhanced US has been widely used in clinical settings, this technology is expected to be applied quickly to clinical practice.FundNational Natural Science Foundation of China and Guangdong Province, Leading Scientific Talents of Guangdong special support program, the Science and Technology Project of Guangdong Province and Guangzhou City.

Hand-held, clinical dual mode ultrasound - photoacoustic imaging of rat urinary bladder and its applications.

Urinary bladder imaging is critical to diagnose urinary tract disorders, and bladder cancer. There is a great need for safe, non-invasive, and sensitive imaging technique which enables bladder imaging. Photoacoustic imaging is a rapidly growing imaging technique for various biological applications. It can be combined with clinical ultrasound imaging system for hand-held, dual modal ultrasound-photoacoustic real-time imaging. Structural (bladder wall) and functional (accretion of nanoparticles) bladder imaging is shown here with combined ultrasound and photoacoustic imaging in rats. Photoacoustic images of bladder wall is shown using black ink as the contrast agent. Chicken tissues were stacked on the abdomen of the animal to demonstrate the feasibility of photoacoustic imaging till a depth of 2 cm. Also, the feasibility of photoacoustic imaging for a common bladder disorder, vesicoureteral reflux is studied using urinary tract mimicking phantom. It is also shown that a clinical ultrasound system can be used for photoacoustic imaging of non-invasive clearance study of gold nanorods from circulation by monitoring the gradual accumulation of the gold nanorods in the bladder. The time taken for accumulation of nanorods in the bladder can be used as an indicator of the clearance rate of the nanoparticle circulation from the body.

Hand-held Clinical Photoacoustic Imaging System for Real-time Non-invasive Small Animal Imaging.

Translation of photoacoustic imaging into the clinic is a major challenge. Handheld real-time clinical photoacoustic imaging systems are very rare. Here, we report a combined photoacoustic and clinical ultrasound imaging system by integrating an ultrasound probe with light delivery for small animal imaging. We demonstrate this by showing sentinel lymph node imaging in small animals along with minimally invasive real-time needle guidance. A clinical ultrasound platform with access to raw channel data allows the integration of photoacoustic imaging leading to a handheld real-time clinical photoacoustic imaging system. Methylene blue was used for sentinel lymph node imaging at 675 nm wavelength. Additionally, needle guidance with dual modal ultrasound and photoacoustic imaging was shown using the imaging system. Depth imaging of up to 1.5 cm was demonstrated with a 10 Hz laser at a photoacoustic imaging frame rate of 5 frames per second.

Non‐invasive sentinel lymph node mapping and needle guidance using clinical handheld photoacoustic imaging system in small animal

Translating photoacoustic imaging (PAI) into clinical setup is a challenge. Handheld clinical real-time PAI systems are not common. In this work, we report an integrated photoacoustic (PA) and clinical ultrasound imaging system by combining light delivery with the ultrasound probe for sentinel lymph node imaging and needle guidance in small animal. The open access clinical ultrasound platform allows seamless integration of PAI resulting in the development of handheld real-time PAI probe. Both methylene blue and indocyanine green were used for mapping the sentinel lymph node using 675 and 690 nm wavelength illuminations, respectively. Additionally, needle guidance with combined ultrasound and PAI was demonstrated using this imaging system. Up to 1.5 cm imaging depth was observed with a 10 Hz laser at an imaging frame rate of 5 frames per second, which is sufficient for future translation into human sentinel lymph node imaging and needle guidance for fine needle aspiration biopsy.

Quantitative ultrasound for tumour characterization and a priorichemotherapy response prediction

Previous studies have demonstrated that quantitative ultrasound (QUS) is an effective tool for monitoring breast cancer patients undergoing neoadjuvant chemotherapy. Here, for the first time, we demonstrate the clinical utility of pre-treatment QUS texture features in predicting the response of breast cancer patients to NAC. Using a 6 MHz center frequency clinical ultrasound imaging system, radiofrequency breast ultrasound data were acquired from 92 locally advanced breast cancer patients prior to their NAC treatment. QUS spectral parameters including mid-band fit, spectral slope, and spectral intercept, and average acoustic concentration and average scatterer diameter were computed from regions of interest in the tumor core and its margin. Subsequently, gray-level co-occurrence matrix textural features were extracted from the parametric images as potential predictive indicators. Results were compared with the clinico-pathological response of each patient determined at their treatment end. A composite QUS...

Three-Dimensional Needle Steering Using Automated Breast Volume Scanner (ABVS)

Robot-assisted and ultrasound-guided needle insertion systems assist in achieving high targeting accuracy for different applications. In this paper, we introduce the use of Automated Breast Volume Scanner (ABVS) for scanning different soft tissue phantoms. The ABVS is a commercial ultrasound transducer used for clinical breast scanning. A preoperative scan is performed for three-dimensional (3D) target localization and shape reconstruction. The ultrasound transducer is also adapted to be used for tracking the needle tip during steering toward the localized targets. The system uses the tracked needle tip position as a feedback to the needle control algorithm. The bevel-tipped flexible needle is steered under ABVS guidance toward a target while avoiding an obstacle embedded in soft tissue phantom. We present experimental results for 3D reconstruction of different convex and non-convex objects with different sizes. Mean Absolute Distance (MAD) and Dice’s coefficient methods are used to evaluate the 3D shape reconstruction algorithm. The results show that the mean MAD values are 0.30[Formula: see text][Formula: see text]0.13[Formula: see text]mm and 0.34[Formula: see text][Formula: see text]0.17[Formula: see text]mm for convex and non-convex shapes, respectively, while mean Dice values are 0.87[Formula: see text]0.06 (convex) and 0.85[Formula: see text]0.06 (non-convex). Three experimental cases are performed to validate the steering system. Mean targeting errors of 0.54[Formula: see text][Formula: see text]0.24, 1.50[Formula: see text][Formula: see text]0.82 and 1.82[Formula: see text][Formula: see text]0.40[Formula: see text]mm are obtained for steering in gelatin phantom, biological tissue and a human breast phantom, respectively. The achieved targeting errors suggest that our approach is sufficient for targeting lesions of 3[Formula: see text]mm radius that can be detected using clinical ultrasound imaging systems.

High frame rate photoacoustic imaging at 7000 frames per second using clinical ultrasound system.

Photoacoustic tomography, a hybrid imaging modality combining optical and ultrasound imaging, is gaining attention in the field of medical imaging. Typically, a Q-switched Nd:YAG laser is used to excite the tissue and generate photoacoustic signals. But, such photoacoustic imaging systems are difficult to translate into clinical applications owing to their high cost, bulky size often requiring an optical table to house such lasers. Moreover, the low pulse repetition rate of few tens of hertz prevents them from being used in high frame rate photoacoustic imaging. In this work, we have demonstrated up to 7000 Hz photoacoustic imaging (B-mode) and measured the flow rate of a fast moving object. We used a ~140 nanosecond pulsed laser diode as an excitation source and a clinical ultrasound imaging system to capture and display the photoacoustic images. The excitation laser is ~803 nm in wavelength with ~1.4 mJ energy per pulse. So far, the reported 2-dimensional photoacoustic B-scan imaging is only a few tens of frames per second using a clinical ultrasound system. Therefore, this is the first report on 2-dimensional photoacoustic B-scan imaging with 7000 frames per second. We have demonstrated phantom imaging to view and measure the flow rate of ink solution inside a tube. This fast photoacoustic imaging can be useful for various clinical applications including cardiac related problems, where the blood flow rate is quite high, or other dynamic studies.

Abstract 14662: Targeted Delivery of an Anti-miR to Cardiomyocytes Using Ultrasound and Microbubbles Suppresses Hypertrophy

Introduction: MicroRNAs (miRs) are dysregulated in various cardiovascular diseases and anti-miRs have been developed to therapeutically inhibit the activity of specific miRs. An anti-miR against miR-23a suppressed hypertension-induced cardiac hypertrophy in preclinical models, but clinical translation is limited by a lack of targeted cardiac delivery systems. Ultrasound (US) targeted microbubble (MB) destruction (UTMD) is a novel therapeutic delivery platform that utilizes MBs as nucleic acid carriers. We hypothesized that UTMD-mediated delivery of anti-miR-23a suppresses cardiomyocyte hypertrophy and assessed UTMD-mediated functional delivery of anti-miR-23a to cultured cardiomyocytes (CMs) in vitro to lay the groundwork for future in vivo translational studies. Methods: Neonatal CMs were isolated from hearts of 1 to 2 day old Sprague Dawley rats. MBs were loaded with LNA-modified negative control anti-miR (NC) or anti-miR-23a, added to CM cultures (anti-miR concentration 300 pM) and insonified with a clinical US imaging system (1.3 MHz, MI setting=1.6). CMs were exposed to 100 μM phenylephrine (PE) to induce hypertrophy. Levels of miR-23a and FOXO3a (miR-23a target) were assessed by qRT-PCR 48 hr after UTMD and normalized to that in NC treated CMs. To quantify hypertrophy, CM surface areas pre- and post-PE were measured by a blinded observer. Results: UTMD treatment with anti-miR-23a knocked down CM miR-23a levels by 51 ± 24% compared to UTMD treatment with NC (N=5-6 per group, p < 0.01). Expression of FOXO3a mRNA (miR-23a target) was 47 ± 16% higher following UTMD-mediated anti-miR-23a delivery compared to NC (N=3 per group, p < 0.05). The increase in CM surface area upon PE exposure was 22 ± 13% less with UTMD-mediated anti-miR-23a delivery compared to NC (N=3 per group, p < 0.05). Conclusions: To our knowledge, this is the first study of UTMD-mediated modulation of miR levels in cardiac tissue with an anti-miR. UTMD mediated delivery of anti-miR-23a to CMs caused knockdown of miR-23a levels, restored expression of downstream target mRNA levels, and suppression of CM hypertrophy. These results lay important groundwork for future in vivo studies leading to targeted clinical strategies to therapeutically modulate miRNA activity in the human heart.

In-plane ultrasonic needle tracking using a fiber-optic hydrophone.

Accurate and efficient guidance of needles to procedural targets is critically important during percutaneous interventional procedures. Ultrasound imaging is widely used for real-time image guidance in a variety of clinical contexts, but with this modality, uncertainties about the location of the needle tip within the image plane lead to significant complications. Whilst several methods have been proposed to improve the visibility of the needle, achieving accuracy and compatibility with current clinical practice is an ongoing challenge. In this paper, the authors present a method for directly visualizing the needle tip using an integrated fiber-optic ultrasound receiver in conjunction with the imaging probe used to acquire B-mode ultrasound images. Needle visualization and ultrasound imaging were performed with a clinical ultrasound imaging system. A miniature fiber-optic ultrasound hydrophone was integrated into a 20 gauge injection needle tip to receive transmissions from individual transducer elements of the ultrasound imaging probe. The received signals were reconstructed to create an image of the needle tip. Ultrasound B-mode imaging was interleaved with needle tip imaging. A first set of measurements was acquired in water and tissue ex vivo with a wide range of insertion angles (15°-68°) to study the accuracy and sensitivity of the tracking method. A second set was acquired in an in vivo swine model, with needle insertions to the brachial plexus. A third set was acquired in an in vivo ovine model for fetal interventions, with insertions to different locations within the uterine cavity. Two linear ultrasound imaging probes were used: a 14-5 MHz probe for the first and second sets, and a 9-4 MHz probe for the third. During insertions in tissue ex vivo and in vivo, the imaged needle tip had submillimeter axial and lateral dimensions. The signal-to-noise (SNR) of the needle tip was found to depend on the insertion angle. With the needle tip in water, the SNR of the needle tip varied with insertion angle, attaining values of 284 at 27° and 501 at 68°. In swine tissue ex vivo, the SNR decreased from 80 at 15° to 16 at 61°. In swine tissue in vivo, the SNR varied with depth, from 200 at 17.5 mm to 48 at 26 mm, with a constant insertion angle of 40°. In ovine tissue in vivo, within the uterine cavity, the SNR varied from 46.4 at 25 mm depth to 18.4 at 32 mm depth, with insertion angles in the range of 26°-65°. A fiber-optic ultrasound receiver integrated into the needle cannula in combination with single-element transmissions from the imaging probe allows for direct visualization of the needle tip within the ultrasound imaging plane. Visualization of the needle tip was achieved at depths and insertion angles that are encountered during nerve blocks and fetal interventions. The method presented in this paper has strong potential to improve the safety and efficiency of ultrasound-guided needle insertions.

Novel lactoferrin-conjugated amphiphilic poly(aminoethyl ethylene phosphate)/poly(L-lactide) copolymer nanobubbles for tumor-targeting ultrasonic imaging.

In the study reported here, a novel amphiphilic poly(aminoethyl ethylene phosphate)/poly(L-lactide) (PAEEP-PLLA) copolymer was synthesized by ring-opening polymerization reaction. The perfluoropentane-filled PAEEP-PLLA nanobubbles (NBs) were prepared using the O1/O2/W double-emulsion and solvent-evaporation method, with the copolymer as the shell and liquid perfluoropentane as the core of NBs. The prepared NBs were further conjugated with lactoferrin (Lf) for tumor-cell targeting. The resulting Lf-conjugated amphiphilic poly(aminoethyl ethylene phosphate)/poly(L-lactide) nanobubbles (Lf-PAEEP-PLLA NBs) were characterized by photon correlation spectroscopy, polyacrylamide gel electrophoresis, Fourier transform infrared spectroscopy, and transmission electron microscopy. The average size of the Lf-PAEEP-PLLA NBs was 328.4±5.1 nm, with polydispersity index of 0.167±0.020, and zeta potential of −12.6±0.3 mV. Transmission electron microscopy imaging showed that the Lf-PAEEP-PLLA NBs had a near-spherical structure, were quite monodisperse, and there was a clear interface between the copolymer shell and the liquid core inside the NBs. The Lf-PAEEP-PLLA NBs also exhibited good biocompatibility in cytotoxicity and hemolysis studies and good stability during storage. The high cellular uptake of Lf-PAEEP-PLLA NBs in C6 cells (low-density lipoprotein receptor-related protein 1-positive cells) at concentrations of 0–20 µg/mL indicated that the Lf provided effective targeting for brain-tumor cells. The in vitro acoustic behavior of Lf-PAEEP-PLLA NBs was evaluated using a B-mode clinical ultrasound imaging system. In vivo ultrasound imaging was performed on tumor-bearing BALB/c nude mice, and compared with SonoVue® microbubbles, a commercial ultrasonic contrast agent. Both in vitro and in vivo ultrasound imaging indicated that the Lf-PAEEP-PLLA NBs possessed strong, long-lasting, and tumor-enhanced ultrasonic contrast ability. Taken together, these results indicate that Lf-PAEEP-PLLA NBs represent a promising nano-sized ultrasonic contrast agent for tumor-targeting ultrasonic imaging.

Hybrid-modality ocular imaging using a clinical ultrasound system and nanosecond pulsed laser.

Hybrid optical modality imaging is a special type of multimodality imaging significantly used in the recent past in order to harness the strengths of different imaging methods as well as to furnish complementary information beyond that provided by any individual method. We present a hybrid-modality imaging system based on a commercial clinical ultrasound imaging (USI) system using a linear array ultrasound transducer (UST) and a tunable nanosecond pulsed laser as the source. The integrated system uses photoacoustic imaging (PAI) and USI for ocular imaging to provide the complementary absorption and structural information of the eye. In this system, B-mode images from PAI and USI are acquired at 10Hz and about 40Hz, respectively. A linear array UST makes the system much faster compared to other ocular imaging systems using a single-element UST to form B-mode images. The results show that the proposed instrumentation is able to incorporate PAI and USI in a single setup. The feasibility and efficiency of this developed probe system was illustrated by using enucleated pig eyes as test samples. It was demonstrated that PAI could successfully capture photoacoustic signals from the iris, anterior lens surface, and posterior pole, while USI could accomplish the mapping of the eye to reveal the structures like the cornea, anterior chamber, lens, iris, and posterior pole. This system and the proposed methodology are expected to enable ocular disease diagnostic applications and can be used as a preclinical imaging system.