• 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.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.1
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• pp.25-32
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• 2019

Purpose: The size, shape, and volume of prosthetic appliance depend on the metal artifacts resulting from dental implant during head and neck treatment with radiation. This reduced the accuracy of contouring targets and surrounding normal tissues in radiation treatment plan. Therefore, the purpose of this study is to obtain the images of metal representing the size of tooth through MVCT, SMART-MAR CT and KVCT, evaluate the volumes, apply them into the proton therapy plan, and analyze the difference of dose distribution. Materials and Methods : Metal A ($0.5{\times}0.5{\times}0.5cm$), Metal B ($1{\times}1{\times}1cm$), and Metal C ($1{\times}2{\times}1cm$) similar in size to inlay, crown, and bridge taking the treatments used at the dentist's into account were made with Cerrobend ($9.64g/cm^3$). Metal was placed into the In House Head & Neck Phantom and by using CT Simulator (Discovery CT 590RT, GE, USA) the images of KVCT and SMART-MAR were obtained with slice thickness 1.25 mm. The images of MVCT were obtained in the same way with $RADIXACT^{(R)}$ Series (Accuracy $Precision^{(R)}$, USA). The images of metal obtained through MVCT, SMART-MAR CT, and KVCT were compared in both size of axis X, Y, and Z and volume based on the Autocontour Thresholds Raw Values from the computerized treatment planning equipment Pinnacle (Ver 9.10, Philips, Palo Alto, USA). The proton treatment plan (Ray station 5.1, RaySearch, USA) was set by fusing the contour of metal B ($1{\times}1{\times}1cm$) obtained from the above experiment by each CT into KVCT in order to compare the difference of dose distribution. Result: Referencing the actual sizes, it was appeared: Metal A (MVCT: 1.0 times, SMART-MAR CT: 1.84 times, and KVCT: 1.92 times), Metal B (MVCT: 1.02 times, SMART-MAR CT: 1.47 times, and KVCT: 1.82 times), and Metal C (MVCT: 1.0 times, SMART-MAR CT: 1.46 times, and KVCT: 1.66 times). MVCT was measured most similarly to the actual metal volume. As a result of measurement by applying the volume of metal B into proton treatment plan, the dose of $D_{99%}$ volume was measured as: MVCT: 3094 CcGE, SMART-MAR CT: 2902 CcGE, and KVCT: 2880 CcGE, against the reference 3082 CcGE Conclusion: Overall volume and axes X and Z were most identical to the actual sizes in MVCT and axis Y, which is in the superior-Inferior direction, was regular in length without differences in CT. The best dose distribution was shown in MVCT having similar size, shape, and volume of metal when treating head and neck protons. Thus it is thought that it would be very useful if the contour of prosthetic appliance using MVCT is applied into KVCT for proton treatment plan.

• 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.