Xiaohua Jian

Three porphyrin derivatives with different ratios of hydrophilic and hydrophobic side chains were successfully synthesized, and then formed into nanoparticles of different sizes via nanoprecipitation as potential photosensitizers.

Background and aims: Transjugular intrahepatic portosystemic shunt (TIPS) is an effective method for reducing portal hypertension in patients with decompensated cirrhosis. However, portal vein puncture is associated with a steep learning curve. Conventional “blind” puncture methods are often imprecise, carry a high risk of complications, and require significant radiation exposure. To increase puncture accuracy, we developed an intravascular navigational ultrasound (IVNU) system. This study aimed to evaluate the feasibility, efficacy, and safety of IVNU for portal vein puncture during TIPS procedures. Methods: In the in vitro experiment, we performed punctures using IVNU in four isolated porcine livers. Subsequently, in the in vivo animal study, eight Bama swine ( Sus scrofa ) were randomly assigned to undergo TIPS using either IVNU (experimental group) or conventional “blind” puncture with the RUPS100 COOK kit (control group). Results: In our in vitro experiment, the IVNU system successfully punctured each lobe. In our in vivo study, all the procedures successfully established portosystemic shunts. The IVNU group exhibited significantly fewer punctures (1.8 ± 0.4 vs. 4.2 ± 1.1), shorter procedure times (32.5 ± 4.2 min vs. 58.7 ± 6.5 min), shorter fluoroscopy times (8.1 ± 1.3 min vs. 20.4 ± 2.1 min), and lower radiation doses (579.5 ± 45.9 mGy vs. 1305.7 ± 50.4 mGy) than the control group (all P < 0.01 ). Puncture-related complications were also significantly reduced in the IVNU group. Conclusions: These findings indicate that IVNU significantly improves portal vein targeting success, reduces the risk of puncture-related complications and radiation exposure, and decreases procedure time, offering clinicians an optimized solution for TIPS creation.

Mechanical scanning with a single transducer is an alternative method for high-frequency ultrasound imaging, which is simple in structure, convenient to implement, and low in cost. However, traditional mechanical scanning ultrasonic imaging introduces additional Doppler shift due to the movement of the transducer, which brings a challenge for blood velocity measurement. An improved mechanical scanning system for high-frequency ultrasonic color Doppler flow imaging is developed in this paper. The mechanical scanning system has a scanning stroke range of 15 mm, a maximum scanning speed of 168 mm/s, and an imaging depth of 20 mm. Since the mechanical scanning of the system is not in uniform motion, motion compensation was applied to achieve high-precision imaging both in B-mode and Doppler mode. The experiment results show that the system imaging resolution can reach about 140 μm in B-mode imaging, the relative velocity error is less than 5% in color Doppler flow imaging at different flow rates, and the CNR of power Doppler flow imaging of this system is greater than 15 dB. The proposed mechanical scanning imaging system can achieve high-resolution structure imaging and color flow imaging, which can provide more diagnostic information for the practical diagnosis and broaden the application range of mechanical scanning ultrasound imaging.

Ultrasound-guided interventional biopsy is becoming an increasingly popular and valuable tool in the clinic. Conventionally, low-frequency (1-5 MHz) ultrasound probes are employed on the patient’s body surface for guiding interventional procedures, leading to low imaging resolution and low puncture accuracy. Several efforts have been made to achieve precise punctures, such as inserting a miniaturized high-frequency phased-array transducer into the patient’s body. However, the interventional devices (introducer biopsy needles) are all separate from those ultrasound probes, which will cause additional damage and operation complexity. Therefore, in this work, a miniature higher frequency phased-array probe integrated with a 0.4 mm intervention working channel is developed, which had 48 array elements and an outer diameter of only 3 mm. The center frequency and -6 dB bandwidth of this probe are measured as 26.2 MHz and 59.6%, respectively. For evaluating its guiding performance, the wire-phantom, ex vivo tissue, and tissue-mimicking phantom experiments were tested. According to the experiments, the axial imaging resolution and lateral resolution can be calculated as 88 and 278 μm at a distance of 2mm far away, respectively, and the effective detecting depth is 12 mm. All these results show that our proposed ultrasound transducer and method can adapt to the works in high-precision interventional guidance.

High-frequency ultrasound has developed rapidly in clinical fields such as cardiovascular, ophthalmology, and skin with its high imaging resolution. However, the development of multi-elements high-frequency ultrasonic transducers and multi-channel high-frequency ultrasound imaging systems is extremely challenging. Here, a high-frequency ultrasound imaging system based on mechanical scanning was proposed in this paper. It adopts the method of reciprocating feed mechanism, which can achieve reciprocating scanning in the 14 mm range at 168 mm/s with a small 60 MHz transducer. A single-channel high-frequency ultrasonic imaging system consisting of the transmitting module, analog front end, acquisition module, and FPGA control module was developed. To overcome the non-uniformity of mechanical scanning, the ultrasound images are compensated according to the motion trajectory. The wire target and ex vivo tissue experiments have shown that the system can obtain an imaging resolution of 51 μm, imaging depth of 8 mm, and imaging speed of 12 fps. This high-frequency mechanical scanning ultrasound imaging system has the characteristics of simple structure, high-frequency, real-time, and good imaging performance, which can meet the clinical needs of high-resolution ultrasound images.

High-frequency endoscopic ultrasound (HFEUS) imaging is an important tool commonly used in clinical practice for imaging hollow organs. The virtual source synthetic aperture (VSSA) method is effective in improving the imaging quality of HFEUS. However, interference from the motor control unit severely affects the accuracy of the conventional delay and sum (DAS) method, thus compromising the effectiveness of VSSA. In this article, a new computational method based on phase correction was proposed to overcome these shortcomings, which is named phase-corrected-and-sum (PCAS). Meanwhile, the parameters of coherence factor weighting (CFW) can be obtained from the correlation coefficient of the superimposed signals to further increase the imaging quality. Three kinds of imaging experiments were designed to evaluate the proposed method. Compared with the conventional method, the results show that the PCAS-CFW method improves the lateral resolution by about 10% and the contrast-to-noise ratio (CNR) by about 44%. Therefore, this proposed method is capable of significantly improving HFEUS image quality, and this method can be easily integrated into current HFEUS imaging systems, showing great potential for clinical applications.

In this study, an ultrasonic phased-array transducer was proposed, which could effectively improve the imaging performance by using 1–3 piezocomposite. The piezocomposite consists of PZT and epoxy, with a pitch of 70 μm, kerf of 20 μm, and thickness of 170 μm. The phased-array transducer has 64 elements; the size of each element is 85 μm × 1.3 mm; the pitch of the transducer is 100 μm; and the kerf between the elements is only 15 μm. To minimize the transducer size, the 1–3 composite uses an encase structure, which connects the upper surface of the composite directly to the flexible circuit board bonded to the lower surface as the ground electrode. The size of the final fabricated transducer is 2 mm × 7.4 mm, and the transducer is mounted on a 9 F (3 mm diameter) catheter, which can bend in four directions and is primarily used for intracardiac echocardiography (ICE). The acoustic and electrical properties of the transducer were tested, including impedance, echo sensitivity, center frequency (9 MHz), bandwidth (BW) (55%), and consistency. Finally, the wire phantom experiments were carried out to demonstrate the spatial resolutions and imaging performance. This study shows that this transducer with compact design and construction can bring higher performance for the single-use disposable ICE catheter.

The equivalent circuit simulation plays an important role in the design of ultrasound transducer. However, the existing methods are difficult to achieve the effect of matching and backing layer, and not able to accurately simulate the transducer with cable. Especially in the application of high frequency ultrasound, the long cable has a great influence on the performance of the transducer. To overcome these limitations, this paper proposed an improved equivalent circuit method, which combined Leach model and transmission line model. It can realize the complete simulation of ultrasound transducer with a long cable, matching layer, and backing layer in PSPICE circuit simulation software when the parameters were measured. Its principles were briefly introduced, and ultrasound transducers with different frequencies (12 and 20 MHz), different matching layers, and different cable lengths (0.5–2.5 m) were designed and fabricated to verify the effectiveness of the method, which is also compared with the traditional KLM method using PiezoCAD. The experiment results showed that the long cable, matching layer, and backing layer have a significant impact on the performance of high frequency ultrasound transducers, and this proposed method has good agreement with these results. Moreover, for the simulation of the complete transducer, the effect of this method is better than KLM model. Besides, this method does not need to know the specific equivalent circuit of matching, backing layer, or cable wire, it can accurately predict the impedance and phase of the transducer through the material parameters, which is very helpful for the material selection and optimization of subsequent transducer design and fabrication. The study indicates that this improved equivalent circuit method is suitable to be applied in the general circuit simulation software and provides strong support for the high frequency transducer and system design.