Journal of the Korean Physical Society

, Volume 66, Issue 2, pp 295–300 | Cite as

Clinical assessment of the jaw-tracking function in IMRT for a brain tumor

  • Jin-Young Kim
  • Shin-Wook Kim
  • Bo-Young Choe
  • Tae-Suk Suh
  • Sung-Kwang Park
  • Sun-Mi Jo
  • Won-Yong Oh
  • Jung-Wook Shin
  • Gyu-Seok Cho
  • Sang-Hee Nam
  • Jin-Beom Chung
  • Jung-Ki Kim
  • Young-Kyu Lee
Article

Abstract

Intensity-modulated radiotherapy (IMRT) improves dose conformity and saves critical organs. IMRT is widely used in cases of head and neck, prostate, and brain cancer due to the close location of the targets to critical structures. However, because IMRT has a larger amount of radiation exposure than 3 dimensional-conformal radiation therapy (3D-CRT), it has disadvantages such as increases in the low dose irradiation to normal tissues and in the accumulated dose for the whole volume due to leakage and transmission of the multi-leaf collimator (MLC). The increased accumulated dose and the larger low dose may increase the occurrence of secondary malignant neoplasms. For these reasons, the jaw-tracking function of the TrueBeam (Varian Medical Systems, Palo Alto, CA) was developed to reduce the leakage and the transmission dose of the MLC with linear accelerators. However, the change in the superficial dose has not been verified with a quantitative analysis of the dose reduction in a brain tumor. Therefore, in the present study, we intended to verify the clinical possibility of utilizing the jaw-tracking function for a brain tumor by comparing treatment plans and superficial doses. To accomplish this, we made three types of original treatment plans using Eclipse11 (Varian Medical Systems, Palo Alto, CA): 1) farther than 2 cm from the organs at risk (OAR); 2) within 2 cm of the OAR; and 3) intersecting with the OAR. Jaw-tracking treatment plans were also made with copies of the original treatment plan using Smart LMC Version 11.0.31 (Varian Medical Systems, Palo Alto, CA). A comparison between the original treatment plans and jaw-tracking treatment plans was performed using the difference of the mean dose and maximum dose to the OARs in cumulative Dose Volume Histogram (DVH). In addition, the dependencies of the effects of transmission and the scattering doses according to jaw motion were assessed through the difference in the surface doses. In the DVH comparison, a maximum dose difference of 0.4% was observed between the planning methods in the case of over 2 cm distance, and the maximum dose of 0.6% was obtained for within the 2 cm distance. For the case intersecting with the OAR, the maximum dose difference of 2.3% was achieved. According to these results, the differences in the mean doses and the maximum doses to the OARs ware larger when the OARs and the planning target volume (PTV) were closer. In addition, small differences in the surface dose measurements were observed. In the case of the inside field, the differences were under 2% of the prescription dose while the difference was under 0.1% in the case of the outside field. Therefore, treatment plans with the jaw-tracking function consistently affected the dose reduction for a brain tumor, and the clinical possibility could be verified as the surface dose was not increased.

Keywords

Jaw-tracking IMRT Treatment planning Dose reduction 

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Copyright information

© The Korean Physical Society 2015

Authors and Affiliations

  • Jin-Young Kim
    • 1
    • 2
  • Shin-Wook Kim
    • 3
  • Bo-Young Choe
    • 1
    • 5
  • Tae-Suk Suh
    • 1
    • 5
  • Sung-Kwang Park
    • 4
  • Sun-Mi Jo
    • 2
  • Won-Yong Oh
    • 2
  • Jung-Wook Shin
    • 6
  • Gyu-Seok Cho
    • 6
  • Sang-Hee Nam
    • 6
  • Jin-Beom Chung
    • 7
  • Jung-Ki Kim
    • 8
  • Young-Kyu Lee
    • 9
  1. 1.Department of Biomedical EngineeringCatholic University of KoreaSeoulKorea
  2. 2.Department of Radiation Oncology, Haeundae Paik HospitalInje UniversityBusanKorea
  3. 3.Department of Radiation Oncology, Incheon St. Mary’s Hospital, College of MedicineCatholic University of KoreaIncheonKorea
  4. 4.Department of Radiation Oncology, Busan Paik HospitalInje UniversityBusanKorea
  5. 5.Research Institute of Biomedical EngineeringCatholic University of KoreaSeoulKorea
  6. 6.Department of Biomedical EngineeringInje UniversityGimhaeKorea
  7. 7.Department of Radiation OncologySeoul National University Bundang HospitalSeongnamKorea
  8. 8.Department of Research CenterDongnam Institute of Radiological & Medical SciencesBusanKorea
  9. 9.Department of Radiation Oncology, Seoul St. Mary’s HospitalCatholic University of KoreaSeoulKorea

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