• Radiation Oncology Journal
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• v.31 no.4
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• pp.252-259
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• 2013

Purpose: To report the results of dosimetric comparison between intensity-modulated radiotherapy (IMRT) using Tomotherapy and four-box field conformal radiotherapy (CRT) for pelvic irradiation of locally advanced rectal cancer. Materials and Methods: Twelve patients with locally advanced rectal cancer who received a short course preoperative chemoradiotherapy (25 Gy in 5 fractions) on the pelvis using Tomotherapy, between July 2010 and December 2010, were selected. Using their simulation computed tomography scans, Tomotherapy and four-box field CRT plans with the same dose schedule were evaluated, and dosimetric parameters of the two plans were compared. For the comparison of target coverage, we analyzed the mean dose, $V_{nGy}$, $D_{min}$, $D_{max}$, radical dose homogeneity index (rDHI), and radiation conformity index (RCI). For the comparison of organs at risk (OAR), we analyzed the mean dose. Results: Tomotherapy showed a significantly higher mean target dose than four-box field CRT (p = 0.001). But, $V_{26.25Gy}$ and $V_{27.5Gy}$ were not significantly different between the two modalities. Tomotherapy showed higher $D_{max}$ and lower $D_{min}$. The Tomotherapy plan had a lower rDHI than four-box field CRT (p = 0.000). Tomotherapy showed better RCI than four-box field CRT (p = 0.007). For OAR, the mean irradiated dose was significantly lower in Tomotherapy than four-box field CRT. Conclusion: In locally advanced rectal cancer, Tomotherapy delivers a higher conformal radiation dose to the target and reduces the irradiated dose to OAR than four-box field CRT.

• Journal of radiological science and technology
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• v.47 no.4
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• pp.263-270
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• 2024

The objective of this study was to evaluate the accuracy and impact of leaf open time (LOT) and pitch using various machine learning models on EBT film-based delivery quality assurance (DQA) performed on 211 patients of helical tomotherapy (HT). We randomly selected passed (n=191) and failed (n=20) DQA measurements to evaluate the accuracy of the k-nearest neighbor (KNN), support vector machine (SVM), naive Bayes (NB) and logistic regression (LR) models using scale-dependent metrics such as the coefficient of determination (R2), mean squared error (MSE), and root MSE (RMSE). We evaluated the performance of the four prediction models in terms of the accuracy, precision, sensitivity, and F1-score using a confusion matrix, finding the NB and LR models to achieve optimal results. The results of this study are expected to reduce the workload of medical physicists and dosimetrists by predicting DQA results according to LOT and pitch in advance.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.69-76
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• 2017

Purpose: The purpose of this study was to verify dosimetric results and reproducibility of position during craniospinal irradiation (CSI) using tomotherapy (Accuray Incorporated, USA). Also, by comparing with conventional CSI Technique, we confirmed the efficiency of using a Tomotherapy. Materials and Methods: 10 CSI patients who get tomotherapy participate. Patient-specific quality assurances (QA) for each patient are conducted before treatment. When treating, we took Megavoltage Computed Tomography (MVCT) that range of head and neck before treatment, L spine area after treatment. Also we conducted in-vivo dosimetry to check a scalp dose. Finally, we made a 3D conventional radiation therapy(3D-CRT) of those patients to compare dosimetric differences with tomotherapy treatment planning. Results: V107, V95 of brain is 0 %, 97.2 % in tomotherapy, and 0.3 %, 95.1 % in 3D-CRT. In spine, value of V107, V95 is 0.2 %, 18.6 % in tomotherapy and 89.6 %, 69.9 % in 3D-CRT. Except kidney and lung, tomotherapy reduced normal organ doses than 3D-CRT. The maximum positioning error value of X, Y, Z was 10.2 mm, -8.9 mm, -11.9 mm. Through in-vivo dosimetry, the average of scalp dose was 67.8 % of prescription dose. All patient-specific QA were passed by tolerance value. Conclusion: CSI using tomotherapy had a risk of parallel organ such as lung and kidney because of integral dose in low dose area. However, it demonstrated dosimetric superiority at a target and saved normal organ to reduce high dose. Also results of reproducibility were not exceeded margins that estimated treatment planning and invivo dosimetry showed to reduce scalp dose. Therefore, CSI using tomotherapy is considered to efficient method to make up for 3D-CRT.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.2
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• pp.13-24
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• 2019

Purpose: CT scan range is insufficient for various reasons in head and neck Tomotherapy^®. To solve that problem, Re-CT simulation is good because CT scan range affects accurate dose calculations, but there are problems such as increased exposure dose, inconvenience, and a change in treatment schedule. We would like to evaluate the minimum CT scan range required by changing the plan setup parameter of the existing CT scan range. Materials and methods: CT Simulator(Discovery CT590 RT, GE, USA) and In House Head & Neck Phantom are used, CT image was acquired by increasing the image range from 0.25cm to 3.0cm at the end of the target. The target and normal organs were registered in the Head & Neck Phantom and the treatment plan was designed using ACCURAY Precision^®. Prescription doses are Daily 2.2Gy, 27 Fxs, Total Dose 59.4Gy. Target is designed to 95%~107% of prescription dose and normal organ dose is designed according to SMC Protocol. Under the same treatment plan conditions, Treatment plans were designed by using five methods(Fixed-1cm, Fixed-2.5cm, Fixed-5cm, Dynamic-2.5cm Dynamic-5cm) and two pitches(0.43, 0.287). The accuracy of dose delivery for each treatment plan was analyzed by using EBT3 film and RIT(Complete Version 6.7, RIT, USA). Results: The accurate treatment plan that satisfying the prescribed dose of Target and the tolerance dose in normal organs(SMC Protocol) require scan range of at least 0.25cm for Fixed-1cm, 0.75cm for Fixed-2.5cm, 1cm for Dynamic-2.5cm, and 1.75cm for Fixed-5cm and Dynamic-5cm. As a result of AnalysisAnalysis by RIT. The accuracy of dose delivery was less than 3% error in the treatment plan that satisfied the SMC Protocol. Conclusion: In case of insufficient CT scan range in head and neck Tomotherapy^®, It was possible to make an accurate treatment plan by adjusting the FW among the setup parameter. If the parameter recommended by this author is applied according to CT scan range and is decide whether to re-CT or not, the efficiency of the task and the exposure dose of the patient are reduced.

• Progress in Medical Physics
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• v.21 no.4
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• pp.340-347
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• 2010

DQA, a patient specific quality assurance in tomotherapy, is usually performed using an ion chamber and a film. The result of DQA is analysed with the treatment planning system called Tomo Planning Station (TomoPS). The two-dimensional dose distribution of film measurement is compared with the dose distribution calculated by TomoPS using the ${\gamma}$-index analysis. In ${\gamma}$-index analysis, the criteria such as 3%/3 mm is used and we verify that whether the rate of number of points which pass the criteria (pass rate) is within tolerance. TomoPS does not provide any quantitative information regarding the pass rate. In this work, a method to get the pass rate of the ${\gamma}$-index analysis was suggested and a software PassRT which calculates the pass rate was developed. The results of patient specific QA of the intensity modulated radiation therapy measured with I'mRT MatriXX (IBA Dosimetry, Germany) and DQA of tomotherapy measured with film were used to verify the proposed method. The pass rate was calculated using PassRT and compared with the pass rate calculated by OmniPro I'mRT (IBA Dosimetry, Germany). The average difference between the two pass rates was 0.00% for the MatriXX measurement. The standard deviation and the maximum difference were 0.02% and 0.02%, respectively. For the film measurement, average difference, standard deviation and maximum difference were 0.00%, 0.02% and 0.02%, respectively. For regions of interest smaller than $24.3{\times}16.6cm^2$ the proposed method can be used to calculate the pass rate of the gamma index analysis to one decimal place and will be helpful for the more accurate DQA in tomotherapy.

• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.65-71
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• 2018

Purpose : Standardized pillow may not support patient's individual cervical spine thoroughly when head and neck radiation therapy with $Tomotherapy^{(R)}$. Therefore, the purpose of this study was to make a comparative analysis for the difference of using standardized pillow only and using customized cervical spine immobilizer with standardized pillow. Materials and Methos : The head and neck cancer patients who are treated image-guided radiation therapy(IGRT) with $Tomotherapy^{(R)}$ were divided into two groups, 20 patients using standardized pillow only, and 20 patients using customized cervical spine immobilizer with standardized pillow. We achieved 20 mega-voltage computed tomography(MVCT) image per patient, compared curvature of the cervical spine in MVCT with curvature of the cervical spine in CT-simulation. Results : Results of comparative analysis were curvature consistency 95.9 %, maximum error of distance 41.9 mm, average distance error per fractionation 19.4 mm, average standard deviation 1.34 mm in case of using standardized pillow only, curvature consistency 98.9 %, maximum error of distance 12.9 mm, average distance error per fractionation 5.8 mm, average standard deviation 0.59 mm in case of using customized cervical spine immobilizer with standardized pillow. Conclusion : Using customized cervical spine immobilizer shows higher reproducibility and low distance error, therefore customized cervical spine immobilizer could be useful for head and neck cancer patients who need radiation therapy.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.2
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• pp.65-74
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• 2019

Purpose: Recently, A Catcher was added to prevent sagging in Radixact^® X9. In this study, We quantitatively compared general couch of Tomo-HDA^® with catcher couch of Radixact^® X9 using the human phantom and evaluated usefulness of catcher. Materials and methods: We used rando phantom for phantom study and set the each iso-center of head and neck region and Pelvis region for region parameter. Furthermore, We used hand made low melting point alloys for weight parameter. MVCT(Mega Voltage Computed Tomography) images were acquired for vertical error and rotation(pitch) error measurement increasing weight(A: 15kg, A+B: 30kg, A+B+C: 45kg). We selected 120 patients who has been treated using Tomotherpy machine for patient study. 60 patients has been treated in Tomo-HDA^® and the other 60 patients treated in Radixact^® X9. In the patient study methods, vertical error and rotation(pitch) error was measured for mean value calculation using MVCT images acquired on first day of radiation therapy. Result: Result of phantom study, Vertical error and rotation(pitch) error was increased proportionally increased as the weight increases in general couch of Tomo-HDA^®. each maximum value was 7.52mm, 0.38° in head and neck region and 11.94mm, 0.92° in pelvis region. However, We could confirm that there was stable error range(0.02~0.1mm, 0~0.04°) in Catcher couch of Radixact^®. Result of patient study, The head and neck region was measured 4.79mm 0.33° lower, and the pelvis region was measured 7.66mm, 0.22° lower in Catcher couch of Radixact^® X9. Conclusion: In this study, Vertical error and rotation(pitch) error was proportionally increased as the weight increases in general couch of Tomo-HDA^®. Especially, The pelvis region error was more increased than the head and neck region error. However, Vertical error and rotation(pitch) error was regularly generated regardless of weight or regions in Catcher^TM couch of Radixact^® X9 that this study's purpose. In conclusion, Catcher^TM couch of Radixact^® X9 can minimize mechanical error that couch sagging. Furthermore, The pelvis region is more efficiency than head and neck region. In radiation therapy using Tomotherapy machine, it is regarded that may contribute to minimizing unadjusted pitch error due to characters of Tomotherapy.

• 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.