Development of a High-Density Piezoelectric Micromachined Ultrasonic Transducer Array Based on Patterned Aluminum Nitride Thin Film.

This study presents the fabrication and characterization of a piezoelectric micromachined ultrasonic transducer (pMUT; radius: 40 µm) using a patterned aluminum nitride (AlN) thin film as the active piezoelectric material. A 20 × 20 array of pMUTs using a 1 µm thick AlN thin film was designed and fabricated on a 2 × 2 mm2 footprint for a high fill factor. Based on the electrical impedance and phase of the pMUT array, the electromechanical coefficient was ~1.7% at the average resonant frequency of 2.82 MHz in air. Dynamic displacement of the pMUT surface was characterized by scanning laser Doppler vibrometry. The pressure output while immersed in water was 19.79 kPa when calculated based on the peak displacement at the resonant frequency. The proposed AlN pMUT array has potential applications in biomedical sensing for healthcare, medical imaging, and biometrics.

High Accuracy Open-Type Current Sensor with a Differential Planar Hall Resistive Sensor.

In this paper, we propose a high accuracy open-type current sensor with a differential Planar Hall Resistive (PHR) sensor. Conventional open-type current sensors with magnetic sensors are usually vulnerable to interference from an external magnetic field. To reduce the effect of an unintended magnetic field, the proposed design uses a differential structure with PHR. The differential structure provides robust performance to unwanted magnetic flux and increased magnetic sensitivity. In addition, instead of conventional Hall sensors with a magnetic concentrator, a newly developed PHR with high sensitivity is employed to sense horizontal magnetic fields. The PHR sensor and read-out integrated circuit (IC) are integrated through a post-Complementary metal-oxide-semiconductor (CMOS) process using multi-chip packaging. The current sensor is designed to measure a 1 A current level. The measured performance of the designed current sensor has a 16 kHz bandwidth and a current nonlinearity of under ±0.5%.

Lordoplasty: an alternative technique for the treatment of osteoporotic compression fracture.

We report here on a new technique using polymethylmethacrylate to manage vertebral osteoporotic compression fractures in three patients. These patients presented with acute back pain that manifested itself after minor trauma. Osteoporotic compression fractures were diagnosed via plain X-ray and magnetic resonance imaging studies. The patients were treated with absolute bed rest and non-steroidal anti-inflammatory drugs. Despite of the conservative treatment, the patients experienced severe, recalcitrant and progressive pain. The vertebrae were collapsed over 50% or kyphotic deformity was seen on the radiologic materials. We performed a new technique called lordoplasty, which is derived from percutaneous vertebroplasty. The patients experienced a reduction in pain after the procedure. The wedge and kyphotic angles of the fractured vertebrae were significantly restored.

Comparison of kyphoplasty and lordoplasty in the treatment of osteoporotic vertebral compression fracture.

STUDY DESIGN: A retrospective study. PURPOSE: To compare the level of restoration of the vertebral height, improvement in the wedge and kyphotic angles, and the incidence of complications in osteoporotic compression fracture in patients treated with either kyphoplasty or lordoplasty. OVERVIEW OF LITERATURE: Kyphoplasty involves recompression of the vertebral bodies. Recently, a more effective method known as lordoplasty was introduced. METHODS: Between 2004 and 2009, patients with osteoporotic thoracolumbar vertebral compression fractures were treated by either kyphoplasty (n = 24) or lordoplasty (n = 12) using polymethylmethacrylate (PMMA) cement, and the results of the two interventions were compared. A visual analogue scale was used to measure the pain status. Preoperative and postoperative radiographs were analyzed to quantify the anterior vertebral height restoration and the wedge and kyphotic alignment correction. RESULTS: All patients in both groups reported a significant decrease in pain. The anterior heights increased 24.2% and 17.5% after the lordoplasty and kyphoplasty procedures, respectively (p < 0.05). Three months after the procedures, there was a larger decrease in the loss of anterior vertebral height in the kyphoplasty group (12.8%) than in the lordoplasty group (6.3%, p < 0.05). The wedge angles decreased after both procedures. The wedge angle in the lordoplasty group maintained its value after 3 months (p < 0.05). The kyphotic angular correction was 11.4 and 7.0° in the lordoplasty and kyphoplasty groups, respectively (p < 0.05). Both kyphotic deformities worsened to a similar degree of 5° after 3 months. CONCLUSIONS: Lordoplasty is more useful than kyphoplasty in terms of the improved anatomic restoration and postoperative maintenance.