• The Korean Journal of Pain
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• v.18 no.2
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• pp.263-266
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• 2005

The ganglion impar is a solitary retroperitoneal structure at the caudal end of the paravertebral sympathetic chain. Block of this ganglion has been advocated as a means of managing intractable perineal pain. In 1990, Plancarte et al performed a neurolytic block of the ganglion impar using 4-6 ml of 10% phenol through the intergluteal skin over the anococcygeal ligament. However, technical difficulties are encountered with the placement of the needle while performing this technique, with complications from the injection of phenol also being a possibility. In 1995, a modified approach for blocking the ganglion impar through the sacrococcygeal ligament was introduced by Wemm and Saberski. We used a radiofrequency (RF) lesion generator to create a controlled and localized lesion with a lower incidence of neural damages compared to chemical neurolysis. RF thermocoagulation of the ganglion impar through the sacrococcygeal ligament was performed on a 70-year-old male patient with constant anal pain using a curved TEW electrode. The patient has been relieved of his pain, without serious complication. Therefore, this technique may be an easier and safer approach, which is associated with fewer chances of complications.

• Investigative Magnetic Resonance Imaging
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• v.20 no.1
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• pp.53-60
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• 2016

Purpose: To develop a technique for quantifying the $^{13}C$-metabolites by performing frequency-selective hyperpolarized $^{13}C$ magnetic resonance spectroscopy (MRS) in vitro which combines simple spectrally-selective excitation with spectrally interleaved acquisition. Methods: Numerical simulations were performed with varying noise level and $K_p$ values to compare the quantification accuracies of the proposed and the conventional methods. For in vitro experiments, a spectrally-selective excitation scheme was enabled by narrow-band radiofrequency (RF) excitation pulse implemented into a free-induction decay chemical shift imaging (FIDCSI) sequence. Experiments with LDH / NADH enzyme mixture were performed to validate the effectiveness of the proposed acquisition method. Also, a modified two-site exchange model was formulated for metabolism kinetics quantification with the proposed method. Results: From the simulation results, significant increase of the lactate peak signal to noise ratio (PSNR) was observed. Also, the quantified $K_p$ value from the dynamic curves were more accurate in the case of the proposed acquisition method compared to the conventional non-selective excitation scheme. In vitro experiment results were in good agreement with the simulation results, also displaying increased PSNR for lactate. Fitting results using the modified two-site exchange model also showed expected results in agreement with the simulations. Conclusion: A method for accurate quantification of hyperpolarized pyruvate and the downstream product focused on in vitro experiment was described. By using a narrow-band RF excitation pulse with alternating acquisition, different resonances were selectively excited with a different flip angle for increased PSNR while the hyperpolarized magnetization of the substrate can be minimally perturbed with a low flip angle. Baseline signals from neighboring resonances can be effectively suppressed to accurately quantify the metabolism kinetics.

• Journal of Korean Neurosurgical Society
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• v.37 no.2
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• pp.105-111
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• 2005

Objective: Tremor, either essential tremor or Parkinsonian tremor, has been effectively and safely treated by lesioning the ventral intermediate(Vim) nucleus of the thalamus with or without mircroelectrode recording. The authors evaluate the treatment outcome of sixteen tremor patients who had been treated with thalamotomy without microelectrode. Methods: Between September, 2001, and December, 2003, sixteen tremor patients were treated with thalamotomy without microelectrode recording. Twelve patients suffered from Parkinsonian tremor and four patients were essential tremor patients. The male to female ratio was 1.6 to 1 with median age of 59.6 years (range; 39-74 years). Under local anesthesia, a 3mm hole was made using a hand-held twist drill, and the dura mater was penetrated with a 1.2mm sharp drill beat. Radiofrequency(RF) electrode was placed in the Vim nucleus of thalamus. With intraoperative macrostimulation, RF lesion was made. Postoperative CT scan and/or MR imaging was performed to confirm the localization of the target lesioned. Preoperative and postoperative tremor was evaluated with simple tremor severity scale and the development of complications related with the procedure was closely reviewed at the immediate postoperative period and the last follow-up. Results: It produces immediate relief in up to 98.4% of the patients. There were no development of complications related with procedure, all patients discharged one or two days after surgery. Conclusion: Vim thalamotomy without microelectrode recording is a safe and effective procedure to control the tremor with minimal morbidity. Intraoperative macroelectrode stimulation safely localizes the Vim nucleus target of the thalamus for the treatment of patients with tremor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.214-215
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• 2007

Etch rates and surface chemistry of phenol formaldehyde-based photoresist after short time $O_2\;and\;N_2O$ radio frequency (RF) plasma treatment depending on exposure time were investigated. It was found that the etch rate of photoresist sharply increased after discharge turn on and reached a limit with increase in plasma exposure time in both gases. X-ray photoelectron spectroscopy (XPS) analysis showed that the surface chemical structure become nearly constant after the treatment of 15 sec. Concentration of surface oxygen-containing groups after processing both in oxygen and in $N_2O$ plasmas is similar.

• Investigative Magnetic Resonance Imaging
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• v.25 no.4
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• pp.229-251
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• 2021

Arteriosclerosis is the leading cause of stroke, with a fatality rate surpassing that of ischemic heart disease. High-resolution vessel wall magnetic resonance imaging is generally recognized as a non-invasive and panoramic method for the evaluation of arterial plaque; however, this method requires improved signal-to-noise ratio and scanning speed. Recent advances in high-density head and neck coil arrays are characterized by broad coverage, multiple channels, and closefitting designs. This review analyzes fast magnetic resonance imaging from the perspective of accelerated algorithms for vessel wall imaging and demonstrates the need for effective algorithms for signal acquisition using advanced radiofrequency system. We summarize different phased-array structures under various experimental objectives and equipment conditions, introduce current research results, and propose prospective research studies in the future.

• Journal of the Korean Wood Science and Technology
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• v.37 no.3
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• pp.192-199
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• 2009

This study was carried out to investigate the performance of a radio-frequency/vacuum dryer combined with a mechanical compressive load (RF/VC) with a scale of about $3m^3$ during drying board of Azobe (Lophira alata) and Korean red pine (Pinus densiflora). The degree of vacuum of the RF/VC system was maintained at 80~105 torr, and wood temperature was increased from $40^{\circ}C$ at the beginning of drying to $60^{\circ}C$ at the end of drying and the radiofrequency generator was operated with schedule of 7 minute-ON and 3 minute-OFF. The wood temperatures near charge plate always remained higher than those of the control during all of the drying stage, whereas the wood temperature near ground plate always remained lower than those of the controlled. As drying time proceeding, the temperature of the wood near ground plate presented lower than those of the control. Whereas the temperature of the wood near charge plate presented higher than those of the controlled. The final average moisture contents of the Azobe boards stacked near the input side of the RF generator showed slightly lower than those near the opposite side. Those of the wood stacked in the layers near the charge plate were lower than those of near the ground plate. The average length of surface checks of the Azobe boards stacked near the charge plate was very slight, whereas that toward the ground plate represented high values. The efficiency of input energy was simliar with the commercial systems.

• Journal of Environmental Health Sciences
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• v.41 no.3
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• pp.182-190
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• 2015

Objectives: To introduce a protocol of Mobi-kids study which was aimed to examine an association between radiofrequency (RF) radiation exposure by mobile phone use and brain tumor risk in children and adolescents. Methods: The Mobi-kids study was a multinational matched case control study using a standardized protocol with the number of subjects targeted about 1,000 cases and 2,000 controls aged 10 to 24. In Mobi-Kids Korea, the source population was restricted to Seoul, Incheon, and Gyeonggi-do province. Eligible cases of primary brain tumor (glioma, meningioma, and others) were diagnosed from January 2012 to June 2015. Eligible controls were appendicitis patients operated during the study period. Two controls were matched on age, gender, and study region for 1 case. Information about pattern and history of mobile phone use and other covariates were obtained by face to face interview by trained interviewer. The Mobi-kids study has been involved in Mobi-expo as a validation study about mobile phone use, XGridmaster to localize tumor in the brain for RF energy calculation, and histological review for validation of diagnosis. Results: The Mobi-kids was the first and largest study in children and adolescents to estimate risk of brain tumor in association with the RF energy absorption in the brain estimated by mobile phone use. Forty-six-cases and 54 controls were collected as of September 2014 in Korea. Conclusions: The meaningful results of the study were expected because of the largest sample size, high validity of EMF exposure assessment as well as the susceptible study populationof children and adolescents.

• Investigative Magnetic Resonance Imaging
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• v.22 no.1
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• pp.26-36
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• 2018

Purpose: Children born with single ventricle physiology demonstrate poor growth rate and suffer from malnutrition, which lead to increased morbidity and mortality in this population. We assume that an anabolic steroid, oxandrolone, will promote growth in these infants by improving myocardial energy utilization. The purpose of this paper is to study the efficacy of oxandrolone on myocardial energy consumption in these infants. Materials and Methods: We modeled single ventricle physiology in a lamb by prenatally shunting the aorta to the pulmonary artery and then postnatally, we monitored cardiac energy utilization by quantitatively measuring the first order reaction rate constant, $k_f$ of the creatine-kinase reaction in the heart using magnetization transfer $^{31}P$ magnetic resonance spectroscopy, home built $^1H/^{31}P$ transmit/receive double tuned coil, and transmit/receive switch. We also performed cine MRI to study the structure and dynamic function of the myocardium and the left ventricular chamber. The spectroscopy data were processed using home-developed python software, while cine data were analyzed using Argus software. Results: We quantitatively measured both the first order reaction rate constant and ejection fraction in the control, shunted, and the oxandrolone-treated lambs. Both $k_f$ and ejection fraction were found to be more significantly reduced in the shunted lambs compared to the control lambs, and they are increased in oxandrolone-treated lambs. Conclusion: Some improvement was observed in both the first order reaction rate constant and ejection fraction for the lamb treated with oxandrolone in our preliminary study.

• The Korean Journal of Pain
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• v.29 no.2
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• pp.123-128
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• 2016

Phantom limb pain is a phenomenon in which patients experience pain in a part of the body that no longer exists. In several treatment modalities, spinal cord stimulation (SCS) has been introduced for the management of intractable post-amputation pain. A 46-year-old male patient complained of severe ankle and foot pain, following above-the-knee amputation surgery on the right side amputation surgery three years earlier. Despite undergoing treatment with multiple modalities for pain management involving numerous oral and intravenous medications, nerve blocks, and pulsed radiofrequency (RF) treatment, the effect duration was temporary and the decreases in the patient's pain score were not acceptable. Even the use of SCS did not provide completely satisfactory pain management. However, the trial lead positioning in the cauda equina was able to stimulate the site of the severe pain, and the patient's pain score was dramatically decreased. We report a case of successful pain management with spinal cauda equina stimulation following the failure of SCS in the treatment of intractable phantom limb pain.

• Radiation Oncology Journal
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• v.9 no.2
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• pp.171-176
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• 1991

To evaluate the temperature distribution according to the size of the electorde and the thickness of the phantom using 8MHz radiofrequency capacitive heating device, various sized electrodes and phantoms were used in combination. The radii of the electrodes are 10, 15, 20, 25, and 30 cm and the thickness of cylindrical phantoms with diameter 30 cm were 10, 15, 20, 25, 30, and 35 cm. When the thickness of the phantom was 25 cm or 30 cm, homogenous heating was achieved by using the electrode which diameter was equal to or greater than the thickness of the phantom. When the thickness of the phantom was 20 cm or less. homogenous heating was not achieved by using the electrode which diameter was equal to the thickness of the phantom, but achieved by the larger diameter of the electorode. When the sizes of paired electrodes were not equal, the smaller electrode side was preferentially heated.