• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.83-95
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• 2018

Purpose : After planning the Respiratory Gated Radiotherapy for Lung cancer, the movement and volume change of sparing normal structures nearby target are not often considered during dose evaluation. This study carried out 4-D dose evaluation which reflects the movement of normal structures at certain phase of Respiratory Gated Radiotherapy, by using Deformable Image Registration that is well used for Adaptive Radiotherapy. Moreover, the study discussed the need of analysis and established some recommendations, regarding the normal structures's movement and volume change due to Patient's breathing pattern during evaluation of treatment plans. Materials and methods : The subjects were taken from 10 lung cancer patients who received Respiratory Gated Radiotherapy. Using Eclipse(Ver 13.6 Varian, USA), the structures seen in the top phase of CT image was equally set via Propagation or Segmentation Wizard menu, and the structure's movement and volume were analyzed by Center-to Center method. Also, image from each phase and the dose distribution were deformed into top phase CT image, for 4-dimensional dose evaluation, via VELOCITY Program. Also, Using $QUASAR^{TM}$ Phantom(Modus Medical Devices) and $GAFCHROMIC^{TM}$ EBT3 Film(Ashland, USA), verification carried out 4-D dose distribution for 4-D gamma pass rate. Result : The movement of the Inspiration and expiration phase was the most significant in axial direction of right lung, as $0.989{\pm}0.34cm$, and was the least significant in lateral direction of spinal cord, as -0.001 cm. The volume of right lung showed the greatest rate of change as 33.5 %. The maximal and minimal difference in PTV Conformity Index and Homogeneity Index between 3-dimensional dose evaluation and 4-dimensional dose evaluation, was 0.076, 0.021 and 0.011, 0.0 respectfully. The difference of 0.0045~2.76 % was determined in normal structures, using 4-D dose evaluation. 4-D gamma pass rate of every patients passed reference of 95 % gamma pass rate. Conclusion : PTV Conformity Index was more significant in all patients using 4-D dose evaluation, but no significant difference was observed between two dose evaluations for Homogeneity Index. 4-D dose distribution was shown more homogeneous dose compared to 3D dose distribution, by considering the movement from breathing which helps to fill out the PTV margin area. There was difference of 0.004~2.76 % in 4D evaluation of normal structure, and there was significant difference between two evaluation methods in all normal structures, except spinal cord. This study shows that normal structures could be underestimated by 3-D dose evaluation. Therefore, 4-D dose evaluation with Deformable Image Registration will be considered when the dose change is expected in normal structures due to patient's breathing pattern. 4-D dose evaluation with Deformable Image Registration is considered to be a more realistic dose evaluation method by reflecting the movement of normal structures from patient's breathing pattern.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.163-170
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• 2014

Purpose : If electron, chosen for superficial oncotherapy, was applied with bolus, it could work as an important factor to a therapy result by showing a drastic change in surface dose. Hence the calculation value and the actual measurement value of surface dose of Treatment Planning System (TPS) according to four variables influencing surface dose when using bolus on an electron therapy were compared and analyzed in this paper. Materials and Methods : Four variables which frequently occur during the actual therapies (A: bolus thickness - 3, 5, 10 mm, B: field size - $6{\time}6$, $10{\time}10$, $15{\time}15cm2$, C: energy - 6, 9, 12 MeV, D: gantry angle - $0^{\circ}$, $15^{\circ}$) were set to compare the actual measurement value with TPS(Pinnacle 9.2, philips, USA). A computed tomography (lightspeed ultra 16, General Electric, USA) was performed using 16 cm-thick solid water phantom without bolus and total 54 beams where A, B, C, and D were combined after creating 3, 5 and 10 mm bolus on TPS were planned for a therapy. At this moment SSD 100 cm, 300 MU was investigated and measured twice repeatedly by placing it on iso-center by using EBT3 film(International Specialty Products, NJ, USA) to compare and analyze the actual measurement value and TPS. Measured film was analyzed with each average value and standard deviation value using digital flat bed scanner (Expression 10000XL, EPSON, USA) and dose density analyzing system (Complete Version 6.1, RIT, USA). Results : For the values according to the thickness of bolus, the actual measured values for 3, 5 and 10 mm were 101.41%, 99.58% and 101.28% higher respectively than the calculation values of TPS and the standard deviations were 0.0219, 0.0115 and 0.0190 respectively. The actual values according to the field size were $6{\time}6$, $10{\time}10$ and $15{\time}15cm2$ which were 99.63%, 101.40% and 101.24% higher respectively than the calculation values and the standard deviations were 0.0138, 0.0176 and 0.0220. The values according to energy were 6, 9, and 12 MeV which were 99.72%, 100.60% and 101.96% higher respectively and the standard deviations were 0.0200, 0.0160 and 0.0164. The actual measurement value according to beam angle were measured 100.45% and 101.07% higher at $0^{\circ}$ and $15^{\circ}$ respectively and standard deviations were 0.0199 and 0.0190 so they were measured 0.62% higher at $15^{\circ}$ than $0^{\circ}$. Conclusion : As a result of analyzing the calculation value of TPS and measurement value according to the used variables in this paper, the values calculated with TPS on 5 mm bolus, $6{\time}6cm2$ field size and low-energy electron at $0^{\circ}$ gantry angle were closer to the measured values, however, it showed a modest difference within the error bound of maximum 2%. If it was beyond the bounds of variables selected in this paper using electron and bolus simultaneously, the actual measurement value could differ from TPS according to each variable, therefore QA for the accurate surface dose would have to be performed.

• Progress in Medical Physics
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• v.29 no.1
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• pp.1-7
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• 2018

The $TomoTherapy^{(R)}$ beam-delivery method creates helical beam-junctioning patterns in the dose distribution within the target. In addition, the dose discrepancy results in the particular region where the resonance by pattern of dose delivery occurs owing to the change in the position and shape of internal organs with a patient's respiration during long treatment times. In this study, we evaluated the dose pattern of the longitudinal profile with the change in respiration. The superior-inferior motion signal of the programmable respiratory motion phantom was obtained using AbChes as a four-dimensional computed tomography (4DCT) original moving signal. We delineated virtual targets in the phantom and planned to deliver the prescription dose of 300 cGy using field widths of 1.0 cm, 2.5 cm, and 5.0 cm. An original moving signal was fitted to reflecting the beam delivery time of the $TomoTherapy^{(R)}$. The EBT3 film was inserted into the phantom movement cassette, and static, without the movement and with the original movement, was measured with signal changes of 2.0 s, 4.0 s, and 5.0 s periods, and 2.0 mm and 4.0 mm amplitudes. It was found that a dose fluctuation within ${\pm}4.0%$ occurred in all longitudinal profiles. Compared with the original movement, the region of the gamma index above 1 partially appeared within the target and the border of the target when the period and amplitude were changed. Gamma passing rates were 95.00% or more. However, cases for a 5.0 s period and 4.0 mm amplitude at a field width of 2.5 cm and for 2.0 s and 5.0 s periods at a field width of 5.0 cm have gamma passing rates of 92.73%, 90.31%, 90.31%, and 93.60%. $TomoTherapy^{(R)}$ shows a small difference in dose distribution according to the changes of period and amplitude of respiration. Therefore, to treat a variable respiratory motion region, a margin reflecting the degree of change of respiration signal is required.

• Journal of Oral Medicine and Pain
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• v.35 no.3
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• pp.193-202
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• 2010

The purpose of this study was to determine the sites of narrowing/obstruction and to measure the regional severity of narrowing through the evaluation of dynamic changes in upper-airway of healthy subjects. The selected 9 subjects were proved not to have any sleep-related disorder such as snoring or obstructive sleep apnea through clinical examination, radiological examination, sleep study with a portable recording system. Afterward, the Electron Beam Tomography was performed during the waking and sleeping state of subjects, with their mandible in resting and protruded position. Intravenous injection of Dormicum$^{(R)}$ was used for the induction of sleep. The maximum and minimum cross-sectional areas at each airway level during tidal ventilation were measured and the Collapsibility Index for each level of cross-section was also computed. In a comparison with results under variable conditions, the result was showed that the significant difference between each airway level divided with upper, middle, lower region of upper airway is not observed in the average minimum cross-sectional areas and Collapsibility Index. The significant difference only between in wake and sleep state was observed in the average minimum cross-sectional area at the lower region. Also, in wake state, the significant difference between resting and protrusive position of mandible for the average minimum was also observed in cross-sectional area at middle region. In sleep state, no significant difference between resting and protrusive position of mandible was observed in cross-sectional area and the Collapsibility Index.

• The Journal of Korean Society for Radiation Therapy
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• v.27 no.2
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• pp.157-166
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• 2015

Purpose : Cyber-Knife tumor tracking system, based on the correlation relationship between the position of a tumor which moves in response to the real time respiratory cycle signal and respiration was obtained by the LED marker attached to the outside of the patient, the location of the tumor to predict in advance, the movement of the tumor in synchronization with the therapeutic device to track real-time tumor, is a system for treating. The purpose of this study, in the cyber knife tumor tracking radiation therapy, trying to evaluate the accuracy of tumor tracking radiation therapy system due to the change in the form of unpredictable sudden breathing due to cough and sleep. Materials and Methods : Breathing Log files that were used in the study, based on the Respiratory gating radiotherapy and Cyber-knife tracking radiosurgery breathing Log files of patients who received herein, measured using the Log files in the form of a Sinusoidal pattern and Sudden change pattern. it has been reconstituted as possible. Enter the reconstructed respiratory Log file cyber knife dynamic chest Phantom, so that it is possible to implement a motion due to respiration, add manufacturing the driving apparatus of the existing dynamic chest Phantom, Phantom the form of respiration we have developed a program that can be applied to. Movement of the phantom inside the target (Ball cube target) was driven by the displacement of three sizes of according to the size of the respiratory vertical (Superior-Inferior) direction to the 5 mm, 10 mm, 20 mm. Insert crosses two EBT3 films in phantom inside the target in response to changes in the target movement, the End-to-End (E2E) test provided in Cyber-Knife manufacturer depending on the form of the breathing five times each. It was determined by carrying. Accuracy of tumor tracking system is indicated by the target error by analyzing the inserted film, additional E2E test is analyzed by measuring the correlation error while being advanced. Results : If the target error is a sine curve breathing form, the size of the target of the movement is in response to the 5 mm, 10 mm, 20 mm, respectively, of the average $1.14{\pm}0.13mm$, $1.05{\pm}0.20mm$, with $2.37{\pm}0.17mm$, suddenly for it is variations in breathing, respective average $1.87{\pm}0.19mm$, $2.15{\pm}0.21mm$, and analyzed with $2.44{\pm}0.26mm$. If the correlation error can be defined by the length of the displacement vector in the target track is a sinusoidal breathing mode, the size of the target of the movement in response to 5 mm, 10 mm, 20 mm, respective average $0.84{\pm}0.01mm$, $0.70{\pm}0.13mm$, with $1.63{\pm}0.10mm$, if it is a variant of sudden breathing respective average $0.97{\pm}0.06mm$, $1.44{\pm}0.11mm$, and analyzed with $1.98{\pm}0.10mm$. The larger the correlation error values in both the both the respiratory form, the target error value is large. If the motion size of the target of the sine curve breathing form is greater than or equal to 20 mm, was measured at 1.5 mm or more is a recommendation value of both cyber knife manufacturer of both error value. Conclusion : There is a tendency that the correlation error value between about target error value magnitude of the target motion is large is increased, the error value becomes large in variation of rapid respiration than breathing the form of a sine curve. The more the shape of the breathing large movements regular shape of sine curves target accuracy of the tumor tracking system can be judged to be reduced. Using the algorithm of Cyber-Knife tumor tracking system, when there is a change in the sudden unpredictable respiratory due patient coughing during treatment enforcement is to stop the treatment, it is assumed to carry out the internal target validation process again, it is necessary to readjust the form of respiration. Patients under treatment is determined to be able to improve the treatment of accuracy to induce the observed form of regular breathing and put like to see the goggles monitor capable of the respiratory form of the person.

• Progress in Medical Physics
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• v.21 no.3
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• pp.291-297
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• 2010

This study examined the dosimetric influence of implanted gold markers in proton therapy and the effects of their positions in the spread-out Bragg peak (SOBP) proton beam. The implanted cylindrical gold markers were 3 mm long and 1.2 mm in diameter. The dosimetric influence of the gold markers was determined with markers at various locations in a proton-beam field. Spatial dose distributions were measured using a three-dimensional moving water phantom and a stereotactic diode detector with an effective diameter of 0.5 mm. Also, a film dosimetry was performed using Gafchromic External Beam Treatment (EBT) film. The GEANT4 simulation toolkit was used for Monte-Carlo simulations to confirm the measurements and to construct the dose-volume histogram with implanting markers. Motion data were obtained from the portal images of 10 patients to investigate the effect of organ motions on the dosimetric influence of markers in the presence of a rectal balloon. The underdosed volume due to a single gold marker, in which the dose was less than 95% of a prescribed amount, was 0.15 cc. The underdosed volume due to the presence of a gold marker is much smaller than the target volume. However, the underdosed volume is inside the gross tumor volume and is not smeared out due to translational prostate motions. The positions of gold markers and the conditions of the proton-beam field give different impacts on the dose distribution of a target with implanted gold markers, and should be considered in all clinical proton-based therapies.

• Progress in Medical Physics
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• v.26 no.1
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• pp.42-51
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• 2015

In proton therapy, verification of proton dose distribution is important to treat cancer precisely and to enhance patients' safety. To verify proton dose distribution, in a previous study, our team incorporated a vertically-aligned one-dimensional array detection system. We measured 2D prompt-gamma distribution moving the developed detection system in the longitudinal direction and verified similarity between 2D prompt-gamma distribution and 2D proton dose distribution. In the present, we have developed two-dimension prompt-gamma measurement system consisted of a 2D parallel-hole collimator, 2D array-type NaI(Tl) scintillators, and multi-anode PMT (MA-PMT) to measure 2D prompt-gamma distribution in real time. The developed measurement system was tested with $^{22}Na$ (0.511 and 1.275 MeV) and $^{137}Cs$ (0.662 MeV) gamma sources, and the energy resolutions of 0.511, 0.662 and 1.275 MeV were $10.9%{\pm}0.23p%$, $9.8%{\pm}0.18p%$ and $6.4%{\pm}0.24p%$, respectively. Further, the energy resolution of the high gamma energy (3.416 MeV) of double escape peak from Am-Be source was $11.4%{\pm}3.6p%$. To estimate the performance of the developed measurement system, we measured 2D prompt-gamma distribution generated by PMMA phantom irradiated with 45 MeV proton beam of 0.5 nA. As a result of comparing a EBT film result, 2D prompt-gamma distribution measured for $9{\times}10^9$ protons is similar to 2D proton dose distribution. In addition, the 45 MeV estimated beam range by profile distribution of 2D prompt gamma distribution was $17.0{\pm}0.4mm$ and was intimately related with the proton beam range of 17.4 mm.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.1
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• pp.29-35
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• 2014

Purpose : This study has already started commercial Gated RapidArc automation equipment which was not previously in the Gated radiation therapy can be performed simultaneously with the VMAT Gated RapidArc radiation therapy to the accuracy of the analysis to evaluate the usability, Amplitude mode applied to the patient. Materials and Methods : The analysis of the distribution of radiation dose equivalent quality solid water phantom and GafChromic film was used Film QA film analysis program using the Gamma factor (3%, 3 mm). Three-dimensional dose distribution in order to check the accuracy of Matrixx dosimetry equipment and Compass was used for dose analysis program. Periodic breathing synchronized with solid phantom signals Phantom 4D Phantom and Varian RPM was created by breathing synchronized system, free breathing and breath holding at each of the dose distribution was analyzed. In order to apply to four patients from February 2013 to August 2013 with liver cancer targets enough to get a picture of 4DCT respiratory cycle and then patients are pratice to meet patient's breathing cycle phase mode using the patient eye goggles to see the pattern of the respiratory cycle to be able to follow exactly in a while 4DCT images were acquired. Gated RapidArc treatment Amplitude mode in order to create the breathing cycle breathing performed three times, and then at intervals of 40% to 60% 5-6 seconds and breathing exercises that can not stand (Fig. 5), 40% While they are treated 60% in the interval Beam On hold your breath when you press the button in a way that was treated with semi-automatic. Results : Non-respiratory and respiratory rotational intensity modulated radiation therapy technique absolute calculation dose of using computerized treatment plan were shown a difference of less than 1%, the difference between treatment technique was also less than 1%. Gamma (3%, 3 mm) and showed 99% agreement, each organ-specific dose difference were generally greater than 95% agreement. The rotational intensity modulated radiation therapy, respiratory synchronized to the respiratory cycle created Amplitude mode and the actual patient's breathing cycle could be seen that a good agreement. Conclusion : When you are treated Non-respiratory and respiratory method between volumetric intensity modulated radiation therapy rotation of the absolute dose and dose distribution showed a very good agreement. This breathing technique tuning volumetric intensity modulated radiation therapy using a rotary moving along the thoracic or abdominal breathing can be applied to the treatment of tumors is considered. The actual treatment of patients through the goggles of the respiratory cycle to create Amplitude mode Gated RapidArc treatment equipment that does not automatically apply to the results about 5-6 seconds stopped breathing in breathing synchronized rotary volumetric intensity modulated radiation therapy facilitate could see complement.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.305-312
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• 2014

Purpose : The purpose of this study is to analyze the mechanical and leaf speed accuracy of the dynamic multileaf collimator (DMLC) and determine the appropriate period of quality assurance (QA). Materials and Methods : The quality assurance of the DMLC equipped with Millennium 120 leaves has been performed total 92 times from January 2012 to June 2014. The the accuracy of leaf position and isocenter coincidence for MLC were checked using the graph paper and Gafchromic EBT film, respectively. The stability of leaf speed was verified using a test file requiring the leaves to reach maximum leaf speed during the gantry rotation. At the end of every leaf speed QA, dynamic dynalog files created by MLC controller were analyzed using dynalog file viewer software. This file concludes the information about the planned versus actual position for all leaves and provides error RMS (root-mean square) for individual leaf deviations and error histogram for all leaf deviations. In this study, the data obtained from the leaf speed QA were used to screen the performance degradation of leaf speed and determine the need for motor replacement. Results : The leaf position accuracy and isocenteric coincidence of MLC was observed within a tolerance range recommanded from TG-142 reports. Total number of motor replacement were 56 motors over whole QA period. For all motors replaced from QA, gradually increased patterns of error RMS values were much more than suddenly increased patterns of error RMS values. Average error RMS values of gradually and suddenly increased patterns were 0.298 cm and 0.273 cm, respectively. However, The average error RMS values were within 0.35 cm recommended by the vendor, motors were replaced according to the criteria of no counts with misplacement > 1 cm. On average, motor replacement for gradually increased patterns of error RMS values 22 days. 28 motors were replaced regardless of the leaf speed QA. Conclusion : This study performed the periodic MLC QA for analyzing the mechanical and leaf speed accuracy of the dynamic multileaf collimator (DMLC). The leaf position accuracy and isocenteric coincidence showed whthin of MLC evaluation is observed within the tolerance value recommanded by TG-142 report. Based on the result obtained from leaf speed QA, we have concluded that QA protocol of leaf speed for DMLC was performed at least bimonthly in order to screen the performance of leaf speed. The periodic QA protocol can help to ensure for delivering accurate IMRT treatment to patients maintaining the performance of leaf speed.