• Clinical and Experimental Pediatrics
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• v.52 no.12
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• pp.1364-1369
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• 2009

Purpose : To analyze abnormal ventricular activation in childhood congenital heart disease induced by postoperative changes in ventricular volume and pressure and ventricular scar formation using signal-averaged electrocardiography (SAECG). Methods : Fifty-two patients who had undergone open heart surgery (OHS) were enrolled. Patients were divided into the following 3 groups: right ventricular volume overload (atrial septal defect, group1), left ventricular volume overload (ventricular septal defect, group2), and right ventricular pressure overload (tetralogy of Fallot, group 3). The patients were monitored by standard 12-lead ECG and SAECG before and 2 months after the operation. QRS duration, QT and QTc intervals, filtered QRS (f-QRS), high frequency low amplitude potential (HFLA), and root mean square (RMS) voltage in the terminal 40 ms of SAECG were determined. Results : In the preoperative period, group1 showed significant increase in QRS (P=0.011) compared to those of the other 2 groups. In the postoperative period, group3 showed significant increase in the QTc interval (P=0.004) compared to those in the other 2 groups. SAECG parameters showed no significant differences among the groups in the pre- or postoperative period. Of the 52 patients, 12 (23%) in the preoperative period and 21 (40%) in the postoperative period had at least 1 SAECG abnormality. The prevalence of SAECG abnormalities was significantly higher in the postoperative group 2 and group 3 (preoperative: 20% versus postoperative: 28%, P<0.001, preoperative: 14% versus postoperative: 64%, P<0.001, respectively). Conclusion : Abnormal SAECG patterns may be attributed to postoperative scars, OHS itself, and/or ventricular overload.

• Radiation Oncology Journal
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• v.28 no.3
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• pp.133-140
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• 2010

Purpose: We retrospectively investigated the effect of irradiation using helical tomotherapy in recurrent pelvic tumors that underwent prior irradiation. Materials and Methods: Fourteen patients with recurrent pelvic tumors consisting of rectal cancer (57.1%), cervical cancer (35.7%) and cancer with an unknown origin (7.1%) were treated with tomotherapy. At the time of irradiation, median tumor size was 3.5 cm and 7 patients complained of pain originating from a recurrent tumor. The median radiation dose delivered to the gross tumor volume, clinical target volume, and planning target volume was 50 Gy, 47.8 Gy and 45 Gy, respectively and delivered at 5 fractions per week over the course of 4 to 5 weeks. Treatment response and duration of local disease control were evaluated using the Response Evaluation Criteria in Solid Tumors (ver. 1.0) and the Kaplan-Meyer method. Treatment-related toxicities were assessed through Common Terminology Criteria for Adverse Events (ver. 3.0). Results: The median follow-up time was 17.3 months, while the response rate was 64.3%. Symptomatic improvement appeared in 6 patients (85.7%). The median duration time of local disease control was 25.8 months. The rates of local failure, distant failure, and synchronous local and distant failure were 57.1%, 21.4%, and 7.1%, respectively. Acute toxicities were limited in grade I or II toxicities, except for one patient. No treatment related death or late toxicity was observed. Conclusion: Helical tomotherapy could be suggested as a feasible palliative option in recurrent pelvic tumors with prior radiotherapy. However, to increase treatment effect and overcome the limitation of this outcome, a large clinical study should be performed.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.8
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• pp.739-746
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• 2010

The purposes of this study are 1) to develop an advanced chamber system within ${\pm}10%$ of air velocity at the particulate matter (PM) collection area, 2) to research theoretical characteristics of PM10 and PM2.5 samplers, 3) to assess the performance characteristics of PM10 and PM2.5 samplers through chamber experiments. The total six one-hour experiments were conducted using the cornstarch with an mass median aerodynamic diameter (MMAD) of $20\;{\mu}m$ and an geometric standard deviation of 2.0 at the two different air velocity conditions of 0.67 m/s and 2.15 m/s in the chamber. The aerosol samplers used in the present study are one APM PM10 and one PM2.5 samplers accordance with the US federal reference methods and specially designed three mini-volume aerosol samplers (two for PM10 and one for PM2.5). The overall results indicate that PM10 and PM2.5 mini-volume samplers need correction factors of 0.25 and 0.39 respectively when APM PM samplers considered as reference samplers and there is significant difference between two mini-volume aerosol samplers when a two-way analysis of variance is tested using the measured PM10 mass concentrations. The PM10 and PM2.5 samplers with the cutpoints and slopes (PM10: $10{\pm}0.5\;{\mu}m$ and $1.5{\pm}0.1$, PM2.5: $2.5{\pm}0.2\;{\mu}m$ and $1.3{\pm}0.03$) theoretically collect the ranges of 86~114% and 64~152% considering the cornstarch characteristics used in this research. Furthermore, the calculated mass concentrations of PM samplers are higher than the ideal mass concentrations when the airborne MMADs for the cornstarch used are smaller than the cutpoints of PM samplers and the PM samplers collected less PM in another case. The chamber experiment also showed that PM10 and PM2.5 samplers had the bigger collection ranges of 37~158% and 55~149% than the theocratical calculated mass concentration ranges and the relatively similar mass concentration ranges were measured at the air velocity of 2.15 m/s comparing with the 0.67 m/s.

• Journal of radiological science and technology
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• v.36 no.2
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• pp.123-129
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• 2013

This study investigated the rate of setup variance by the rotating unbalance of gantry in image-guided radiation therapy. The equipments used linear accelerator(Elekta Synergy TM, UK) and a three-dimensional volume imaging mode(3D Volume View) in cone beam computed tomography(CBCT) system. 2D images obtained by rotating $360^{\circ}$and $180^{\circ}$ were reconstructed to 3D image. Catpan503 phantom and homogeneous phantom were used to measure the setup errors. Ball-bearing phantom was used to check the rotation axis of the CBCT. The volume image from CBCT using Catphan503 phantom and homogeneous phantom were analyzed and compared to images from conventional CT in the six dimensional view(X, Y, Z, Roll, Pitch, and Yaw). The variance ratio of setup error were difference in X 0.6 mm, Y 0.5 mm Z 0.5 mm when the gantry rotated $360^{\circ}$ in orthogonal coordinate. whereas rotated $180^{\circ}$, the error measured 0.9 mm, 0.2 mm, 0.3 mm in X, Y, Z respectively. In the rotating coordinates, the more increased the rotating unbalance, the more raised average ratio of setup errors. The resolution of CBCT images showed 2 level of difference in the table recommended. CBCT had a good agreement compared to each recommended values which is the mechanical safety, geometry accuracy and image quality. The rotating unbalance of gentry vary hardly in orthogonal coordinate. However, in rotating coordinate of gantry exceeded the ${\pm}1^{\circ}$ of recommended value. Therefore, when we do sophisticated radiation therapy six dimensional correction is needed.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.21-25
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• 2010

Purpose: For better PET imaging with accuracy the transmission scanning is inevitably required for attenuation correction. The attenuation is affected by condition of acquisition and patient position, consequently quantitative accuracy may be decreased in emission scan imaging. In this paper, the present study aims at providing the measurement for attenuation varying with the positions of the patient's arm in whole body PET/CT, further performing the comparative analysis over its SUV changes. Materials and Methods: NEMA 1994 PET phantom was filled with $^{18}F$-FDG and the concentration ratio of insert cylinder and background water fit to 4:1. Phantom images were acquired through emission scanning for 4min after conducting transmission scanning by using CT. In an attempt to acquire image at the state that the arm of the patient was positioned at the lower of ahead, image was acquired in away that two pieces of Teflon inserts were used additionally by fixing phantoms at both sides of phantom. The acquired imaged at a were reconstructed by applying the iterative reconstruction method (iteration: 2, subset: 28) as well as attenuation correction using the CT, and then VOI was drawn on each image plane so as to measure CT number and SUV and comparatively analyze axial uniformity (A.U=Standard deviation/Average SUV) of PET images. Results: It was found from the above phantom test that, when comparing two cases of whether Teflon insert was fixed or removed, the CT number of cylinder increased from -5.76 HU to 0 HU, while SUV decreased from 24.64 to 24.29 and A.U from 0.064 to 0.052. And the CT number of background water was identified to increase from -6.14 HU to -0.43 HU, whereas SUV decreased from 6.3 to 5.6 and A.U also decreased from 0.12 to 0.10. In addition, as for the patient image, CT number was verified to increase from 53.09 HU to 58.31 HU and SUV decreased from 24.96 to 21.81 when the patient's arm was positioned over the head rather than when it was lowered. Conclusion: When arms up protocol was applied, the SUV of phantom and patient image was decreased by 1.4% and 9.2% respectively. With the present study it was concluded that in case of PET/CT scanning against the whole body of a patient the position of patient's arm was not so much significant. Especially, the scanning under the condition that the arm is raised over to the head gives rise to more probability that the patient is likely to move due to long scanning time that causes the increase of uptake of $^{18}F$-FDG of brown fat at the shoulder part together with increased pain imposing to the shoulder and discomfort to a patient. As regarding consideration all of such factors, it could be rationally drawn that PET/CT scanning could be made with the arm of the subject lowered.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.122-125
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• 2004

In radiotherapy of tumors in liver, enough planning target volume (PTV) margins are necessary to compensate breathing-related movement of tumor volumes. To overcome the problems, this study aims to obtain patients' body movements by using a moving phantom and an ultrasonic sensor, and to develop respiration gating techniques that can adjust patients' beds by using reversed values of the data obtained. The phantom made to measure patients' body movements is composed of a microprocessor (BS II, 20 MHz, 8K Byte), a sensor (Ultra-Sonic, range 3 cm ${\sim}$3 m), host computer (RS232C) and stepping motor (torque 2.3Kg) etc., and the program to control and operate it was developed. The program allows the phantom to move within the maximum range of 2 cm, its movements and corrections to take place in order, and x, y and z to move successively. After the moving phantom was adjusted by entering random movement data(three dimensional data form with distance of 2cm), and the phantom movements were acquired using the ultra sonic sensor, the two data were compared and analyzed. And then, after the movements by respiration were acquired by using guinea pigs, the real-time respiration gating techniques were drawn by operating the phantom with the reversed values of the data. The result of analyzing the acquisition-correction delay time for the three types of data values and about each value separately shows that the data values coincided with one another within 1% and that the acquisition-correction delay time was obtained real-time (2.34 ${\times}$ 10$^{-4}$sec). This study successfully confirms the clinic application possibility of respiration gating techniques by using a moving phantom and an ultra sonic sensor. With ongoing development of additional analysis system, which can be used in real-time set-up reproducibility analysis, it may be beneficially used in radiotherapy of moving tumors.

• Progress in Medical Physics
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• v.18 no.1
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• pp.27-34
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• 2007

Respiration sating radiotherapy technique developed In consideration of the movement of body surface and Internal organs during respiration, is categorized into the method of analyzing the respiratory volume for data processing and that of keeping track of fiducial landmark or dermatologic markers based on radiography. However, since these methods require high-priced equipments for treatment and are used for the specific radiotherapy. Therefore, we should develop new essential method whilst ruling out the possible problems. This study alms to obtain body surface motion by using the couch based computer-controlled motion phantom (CBMP) and US sensor, and to develop respiration gating techniques that can adjust patients' beds by using opposite values of the data obtained. The CBMP made to measure body surface motion is composed of a BS II microprocessor, sensor, host computer and stopping motor etc. And the program to control and operate It was developed. After the CBMP was adjusted by entering random movement data, and the phantom movements were acquired using the sensors, the two data were compared and analyzed. And then, after the movements by respiration were acquired by using a rabbit, the real-time respiration gating techniques were drawn by operating the phantom with the opposite values of the data. The result of analysing the acquisition-correction delay time for the data value shows that the data value coincided within 1% and that the acquistition-correction delay time was obtained real-time $(2.34{\times}10^{-4}sec)$. And the movement was the maximum movement was 6 mm In Z direction, In which the respiratory cycle was 2.9 seconds. This study successfully confirms the clinical application possibility of respiration gating techniques by using a CBWP and sensor.

• Progress in Medical Physics
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• v.25 no.1
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• pp.46-52
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• 2014

Liquid ionization chamber is filled with liquid equivalent material unlike air filled ionization chamber. The high density material allow very small-volume chamber to be constructed that still have a sufficiently high sensitivity. However liquid ionization chamber should be considered for both initial recombination and general recombination. We, therefore, studied using the Co-60 beam as the continuous beam and the microLion chamber (PTW) for comparing the ion collection efficiency by Greening theory, two-dose rate method and our experiment method. The measurements were carried out using Theratron 780 as the cobalt machine and water phantom and 0.6 cc Farmer type ionization chamber was used with microLion chamber in same condition for measuring the charge of microLion chamber according to the dose rates. Dose rate was in 0.125~0.746 Gy/min and voltages applied to the microLion chamber were +400, +600 and +800 V. As the result, the collection efficiency by three method was generally less than 1%. In particular, our experimental collection efficiency was in good agreement within 0.3% with Greening theory except the lowest two dose rates. The collection efficiency by two-dose rate method also agreed with Greening theory generally less than 1%, but the difference was about 4% when the difference of two dose rates were lower. The ion recombination correction factors by Greening theory, two-dose rate method and our experiment were 1.0233, 1.0239 and 1.0316, respectively, in SSD 80 cm, depth 5 cm recommended by TRS-398 protocol. Therefore we confirmed that the loss by ion recombination was about 3% in this condition. We think that our experiment method for ion recombination correction will be useful tool for radiation dosimetry in continuous beam.

• Radiation Oncology Journal
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• v.21 no.2
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• pp.174-181
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• 2003

Purpose: The target volume for the three field technique in breast cancer include the breast tangential and supraclavicular areas. The techniques rotating the gantry and couch angles, to match these two areas, will geometrically produce mismatching of the posterior edge between the medial and lateral tangential beams. This mismatch was confirmed by film dosimetry and three-dimensional computer planning. The correction methods of this mismatching were studied in this article. Materials and Methods: After the supraclavicular field was simulated using a half beam block and the medial and lateral tangential fields, by the rotation of the couch and gantry, we compared the following two methods to correct the mismatch. The first method was the rotation of coillmator until a line drawn on the posterior edge of tangential beams before the rotation of couch aligned the line drawn on the posterior edge after the rotation. The second method was the rotation of collimator according to the formula developed by the author as follows; Co=$2sin^{-1}${$sin\{theta}\{cdot}sin(C/2)$} (Co: collimator angle, $\theta$: angle between tangential beam and table, C: couch angle) Results: The film dosimetry showed the mismatching of posterior edges of the medial and lateral tangential fields prior to the rotation of collimator, while the posterior edges matched well after the rotation of collimator according to the formula. The three-dimensional computer plan also showed that the posterior edges matched well after the rotation of collimator accordingly. The DVH of the ipsilateral lung with the proper rotation of collimator angle was better than that without the rotation of collimator angle. Conclusion: The mismatching of the posterior edges of the medial and lateral tangential fields can be recognized on the three fileld technique in breast irradiation when the gantry and couch are simultaneously rotated and can be corrected with the proper rotation of the collimator angle. The radiation dose to the ipsilateral lung could be lowered with this technique.

• Radiation Oncology Journal
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• v.22 no.4
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• pp.316-324
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• 2004

Purpose : In radiotherapy of tumors in liver, enough planning target volume (PTV) margins are necessary to compensate breathing-related movement of tumor volumes. To overcome the problems, this study aims to obtain patients' body movements by using a moving phantom and an ultrasonic sensor, and to develop respiration sating techniques that can adjust patients' beds by using reversed values of the data obtained. Materials and Methods : The phantom made to measure patients' body movements is composed of a microprocessor (BS II, 20 MHz, 8K Byte), a sensor (Ultra-Sonic, range $3\~3$ m), host computer (RS232C) and stepping motor (torque 2.3 Kg) etc., and the program to control and operate it was developed. The program allows the phantom to move within the maximum range of 2 cm, its movements and corrections to take place In order, and x, y and z to move successively. After the moving phantom was adjusted by entering random movement data (three dimensional data form with distance of 2 cm), and the phantom movements were acquired using the ultra sonic sensor, the two data were compared and analyzed. And then, after the movements by respiration were acquired by using guinea pigs, the real-time respiration gating techniques were drawn by operating the phantom with the reversed values of the data. Results : The result of analyzing the acquisition-correction delay time the three types of data values and about each value separately shows that the data values coincided with one another within $1\%$ and that the acquisition-correction delay time was obtained real-time $(2.34{\times}10^{-4}sec)$. Conclusion : This study successfully confirms the clinic application possibility of respiration gating techniques by using a moving phantom and an ultrasonic sensor. With ongoing development of additional analysis system, which can be used in real-time set-up reproducibility analysis, it may be beneficially used in radiotherapy of moving tumors.