Jeong Han Yi

Measurement of Two-Dimensional Photon Beam Distributions Using a Fiber-Optic Radiation Sensor for Small Field Radiation Therapy

In this study, a fiber-optic radiation sensor with an organic scintillator is fabricated to measure high-energy photon beam from a clinical linear accelerator (CLINAC) and a fiberoptic sensor array is also fabricated to measure two-dimensional, high-resolution and real-time dose distributions for small field radiotherapy dosimetry. The scintillating lights generated from each organic sensor probe embedded and arrayed in a water phantom are guided by 10 m plastic optical fibers to the light- measuring device. The two-dimensional photon beam distributions in a water phantom are measured with different energies and field sizes of photon beams. Also, percent depth dose curves for 6 and 15 MV photon beams are obtained.

Measurement of two-dimensional photon beam distributions using a fiber-optic radiation sensor for small field radiation therapy

In this study, we fabricated a fiber-optic radiation sensor with an organic scintillator to measure the high-energy photon beam from a clinical linear accelerator, and a two-dimensional fiber-optic sensor array to measure high-resolution and real-time dose distributions for small field radiotherapy dosimetry. The scintillating lights generated from each organic sensor probe embedded and arrayed in a water phantom are guided by 10 m plastic optical fibers to the light-measuring device. Two-dimensional photon beam distributions in a water phantom were measured for photon beams with different energies and field sizes. Also, percent depth dose curves for 6 and 15 MV photon beams were obtained.

Feasibility Study of Development of Plastic Optical Fiber Temperature Sensor Using Thermosensitive Clouding Material

In this paper, we describe the feasibility of developing a new plastic optical fiber temperature sensor using a thermosensitive clouding material (TSCM) that changes its light transmittance with temperature. The temperature change in the TSCM gives rise to change in the turbidity of the TSCM, and the transmittance of the TSCM is altered according to the turbidity change. Light with a selected wavelength is transmitted to the TSCM, and the optical power of the reflected light from a reflector is measured using a Y-coupler made of plastic optical fibers.

Development of an MR-Compatible ECG Amplifier

The purpose of the present study is to develop a magnetic resonance (MR)-compatible electrocardiogram (ECG) amplifier. If ECG signals are measured simultaneously with the acquisition of MR images, there can be a mutual interference effect. The present system was designed to block noises caused by the main magnetic field, gradient magnetic field and radiofrequency (RF) pulse when MR images are acquired. It uses analogue elements in order to remove any possible effect on MR images. In addition, a radio-frequency-interference (RFI)-free optical data link using the pulse-width modulation (PWM) technique is adopted in order to transmit ECG signals measured inside the MR room.

Evaluation of Optical Properties for Development of Ultrahigh-Resolution Flexible Contact Endoscope

In this study, a new flexible contact endoscope that is similar to a fiber-optic ultrathin endoscope is examined. Using a new optical design with a 0.23 pitch gradient index lens and an ultrathin fiber-optic image guide, we have obtained 228 line pairs/mm ultrahigh-resolution images. The resolution and magnification of the obtained images are measured and analyzed. Also, the relationship between magnification and the working distance from the target to the gradient index (GRIN) lens using GRIN lenses of different pitch lengths is determined. Finally, we have taken an image of red blood corpuscles of 6–9 µm average size.

MEASUREMENTS OF HIGH ENERGY X-RAY DOSE DISTRIBUTIONS USING MULTI-DIMENSIONAL FIBER-OPTIC RADIATION DETECTORS

In this study, we have fabricated multi-dimensional fiber-optic radiation detectors with organic scintillators, plastic optical fibers and photo-detectors such as photodiode array and a charge-coupled device. To measure the X-ray dose distributions of the clinical linear accelerator in the tissue-equivalent medium, we have fabricated polymethylmethacrylate phantoms which have one-dimensional and two-dimensional fiber-optic detector arrays inside. The one-dimensional and two-dimensional detector arrays can be used to measure percent depth doses and surface dose distributions of high energy X-ray in the phantom respectively.

A Simple Finger Stimulator for Simultaneous Vibration and Heat Stimulation

In this study, we developed a simple finger stimulator that can simultaneously control vibration and heat stimulation. The newly developed stimulator consists of three parts, namely the control unit, drive unit, and an actuator. The control unit controls the stimulation type, frequency, intensity, and time. The drive unit amplifies the stimulation signal that drives the actuator. The actuator displays the vibration and heat stimuli quantitatively and simultaneously. Although the developed stimulator is simple, it has a wide frequency range of 0-400 Hz comprising 40 levels, and vibration stimulation intensity comprising 50 levels. The control temperature and stimulation temperature used for heat stimulation comprise four and eight levels, respectively. In addition, the developed stimulator has many advantages in terms of the overall system, stimulation control, and safety. Therefore, the developed stimulator can be used for integrative tactile perception and cognition studies on various vibration and heat sensations.

A Study on the Characteristics of a Vibrator Using Flat PCB-Coil

In this study, we developed and evaluateda vibrator using a flat PCB-coil. The flat PCB-coil vibrator was fabricated on a printed circuit board using and etching process. The spiral pattern was etched on a fiberglass cloth with an epoxy resin. To evaluatethe flat PCB-coil vibrator, we generated a sine wave, saw-tooth, and square wave through a custom made wave generator and amplified the waveforms using a power amplifier. A three-axis accelerometer was used to evaluate the performance of the developed vibrator. Even though the developed vibrator is simple, it has a wide range of vibration frequency (50~500 Hz) and vibration amplitude (0~5 V). The vibration amplitude does not change due to frequency change. It is expected that the developed vibrator can be used in a wide variety of applications such as in a tactile stimulator, in elastography, energy harvesting, and in a cooling system.

Wireless Grip and Acceleration Measurement System for Putting Stroke Analysis

Putting stroke accounts for 40∼50% of total strokes during a golf rounding. Grasping force of putter griping and motion of wrists during a putting stroke are the most important factors for evaluation of the putting event. In this paper, we developed a wireless grip and acceleration measurement system using force sensors and accelerometers for detection and analysis of the golf putting.

A MR-Compatible Finger Stimulator for Simultaneous Pressure and Heat Stimulation

In this study, a Magnetic Resonance (MR)-compatible finger stimulator was developed that can display pressure and heat stimulation simultaneously. The developed finger stimulator consists of three parts: a main controller, drive units, and tactors. The main controller controls stimulation parameters such as stimulation intensity and time. The drive units operate pressure and heat tactors in response to commands from the main controller. The tactors display various pressure and heat stimulation quantitatively and simultaneously. The developed stimulator has many advantages in overall system, stimulation control, and tactor aspects. The new stimulator operated stably in MR circumstance without affecting MR images. Therefore, it can be used for the various intra-and inter-finger functional magnetic resonance imaging (fMRI) studies on pressure and heat sensation.