Development of length standard phantom for length measurement correction in x-ray image.

Specific tissue lengths or volumes in x-ray images are measured for diagnostic and therapeutic purposes. Measurements are used to make clinical decisions; however, the accuracy of these measurements has not been studied. In this study, based on the sources of uncertainty, an SI-traceable length standard phantom and an x-ray imaging system calibration method are proposed. The uncertainty in the length of the fabricated standard phantom is determined using a toolmaker's microscope. The sources of uncertainty in an x-ray imaging system, such as magnification, pixel-to-millimeter unit conversion, and penumbra effect, are considered, and the lengths of the phantom before and after imaging system calibration were compared. The maximum deviation of length measurements with and without calibration is (-0.11 ± 0.10) and (-3.37 ± 0.15) mm (k = 2, 95% level of confidence), respectively. The proposed phantom and calibration method can be used for calibrating x-ray images and obtaining their length correction values. Furthermore, length correction values are expected to be useful for diagnosis and treatment planning, where precise length measurements are essential.

LEGO-compatible modular mapping phantom for magnetic resonance imaging.

Physical phantoms have been widely used for performance evaluation of magnetic resonance imaging (MRI). Although there are many kinds of physical phantoms, most MRI phantoms use fixed configurations with specific sizes that may fit one or a few different types of radio frequency (RF) coils. Therefore, it has limitations for various image quality assessments of scanning areas. In this article, we report a novel design for a truly customizable MRI phantom called the LEGO-compatible Modular Mapping (MOMA) phantom, which not only serves as a general quality assurance phantom for a wide range of RF coils, but also a flexible calibration phantom for quantitative imaging. The MOMA phantom has a modular architecture which includes individual assessment functionality of the modules and LEGO-type assembly compatibility. We demonstrated the feasibility of the MOMA phantom for quantitative evaluation of image quality using customized module assembly compatible with head, breast, spine, knee, and body coil features. This unique approach allows comprehensive image quality evaluation with wide versatility. In addition, we provide detailed MOMA phantom development and imaging characteristics of the modules.

Truncated Hollow Cone Probe for Assessing Transepidermal Water Loss and Skin Hardness.

This study proposes a skin analysis device using a truncate hollow cone (THC) probe for measuring both transepidermal water loss (TEWL) and skin hardness. Because skin health is closely related to the epidermal barrier function and skin mechanical property, it is important to measure their biophysical indicators at the same time, to understand skin conditions and diagnose skin disorders such as atopic dermatitis and systemic sclerosis. Previous skin analyzers, however, required different probes with different protocols for each biophysical indicators, which makes the measurement inconvenient and increases the measurement uncertainty. The present device consists of a THC probe equipped with humidity and force sensors, and an actuator that simultaneously measure both TEWL and skin hardness which indicate the integrity of the epidermal barrier function and the skin mechanical property, respectively. Using artificial reference skins, the prototype device showed the TEWL with a sensitivity and linearity of 0.011 (%/s)/(g/m2/h) and 99.5%, and the hardness with 0.075 N/(Shore 00) and 97.6%, respectively, which are within the appropriate range for the properties of human skin. The on-body measurement of five subjects showed that the proposed device could measure both the TEWL and skin hardness without any crosstalk from each other. The proposed device has great potential for in-depth analysis of the health status of the skin which could indicate various skin diseases.

Realization of an ultrathin acoustic lens for subwavelength focusing in the megasonic range.

In this study, we report the first experimental realization of an ultrathin (0.14λ, λ = 1.482 mm means wavelength at 1 MHz in the water medium) subwavelength focusing acoustic lens that can surpass the Rayleigh diffraction limit (0.61λ/NA, NA means numerical aperture). It is termed a Super-Oscillatory Acoustic Lens (SOAL), and it operates in the megasonic range. The SOAL represents an interesting feature allowing the achievement of subwavelength focusing without the need to operate in close proximity to the object to be imaged. The optimal layout of the SOAL is obtained by utilizing a systematic design approach, referred to here as topology optimization. To this end, the optimization formulation is newly defined. The optimized SOAL is fabricated using a photo-etching process and its subwavelength focusing performance is verified experimentally via an acoustic intensity measurement system. From these measurements, we found that the proposed optimized SOAL can achieve superior focusing features with a Full Width at Half Maximum (FWHM) of ~0.40λ/NA ≃ 0.84 mm (for our SOAL, NA = 0.707) with the transmission efficiency of 26.5%.

Development of a simulator for the validation of noninvasive blood pressure-monitoring devices.

This research aimed to develop a simulator capable of oscillometric pressure pulses recorded from the participants for the validation of oscillometric noninvasive blood pressure (NIBP) devices. The simulator generates the pressure pulses to the cuff connected to NIBP devices depending on the oscillometric waveforms obtained from the participants. Device readings were compared with auscultatory references (systolic and diastolic blood pressures) of the participants. A total of 94 oscillometric waveforms from participants were used in the simulator for the validation of two automated NIBP devices (Omron HEM-7221 and UA-787Plus). For Omron HEM-7221, the differences between device readings and auscultation references for systolic and diastolic blood pressures were 2.82±7.27 and -4.74±6.73 mmHg, respectively. UA-787Plus showed differences of 3.26±5.69 and -3.53±6.61 mmHg, respectively. Although the number of individual measurements did not fulfill the ISO 81060-2 requirement for clinical validation, criterion 1, where the average of the difference and SD should be lower than ±5 and -8 mmHg, was fulfilled. Although the simulator still needs extensive comparative studies to be verified, it could be a potential candidate for a simple and robust tool for the validation and quality control of NIBP devices.

Fabrication and comparison of PMN-PT single crystal, PZT and PZT-based 1-3 composite ultrasonic transducers for NDE applications.

This paper describes fabrication and comparison of PMN-PT single crystal, PZT, and PZT-based 1-3 composite ultrasonic transducers for NDE applications. As a front matching layer between test material (Austenite stainless steel, SUS316) and piezoelectric materials, alumina ceramics was selected. The appropriate acoustic impedance of the backing materials for each transducer was determined based on the results of KLM model simulation. Prototype ultrasonic transducers with the center frequencies of approximately 2.25 and 5MHz for contact measurement were fabricated and compared to each other. The PMN-PT single crystal ultrasonic transducer shows considerably improved performance in sensitivity over the PZT and PZT-based 1-3 composite ultrasonic transducers.