yfwfG@45 2  2019N3z
      Original Article
EQuality assurance of CT number|relative electron density conversion table for dose calculation using CT images with single energy projection-based MAR technique
    Shogo Hatanaka, et al.i2019.3.8j
    i@SFy[WɌf@PWKvł
     
     


 

Original Article

 

Quality assurance of CT number–relative electron density
conversion table for dose calculation using CT images with single
energy projection-based MAR technique

Shogo Hatanaka 1j, Kazutoshi Kodama 1j, Tetsuya Watanabe 1j,
Masatsugu Hariu1j, Rikana Soda1j, Kana Washizu1j, Nobuko Utsumi 1,2j,
Takafumi Yamano 1j, Keiichiro Nishimura 1j, Keisuke Todoroki 1j,
Katsuhito Hosaka 1j, Munefumi Shimbo 1j, Takeo Takahashi 1j

1jDepartment of Radiation Oncology, Saitama Medical Center, Saitama Medical University
2jDepartment of Radiology, JCHO Tokyo Shinjuku Medical Center


 

Abstract
@A metal artifact reductioniMARjtechnique can reduce beam hardening and streak artifacts caused by metal in the body on computed tomographyiCTj. In this study, we evaluated a CT number–relative electron densityiCT-rEDjconversion table in dose calculation using CT images with MAR technique. Materials and methods: CT images of a RMI-467 cylinder-type solid water phantom, 16 normal rods irED: 0.28 to 1.69j, a titanium rodi3.79jand a stainless-steel rodi6.58jwere acquired for the CT-rED table. Four CT-rED tables were created using the CT images with single energy projection-based MAR techniques: normalrawiwithout MARj, normal, normal + titanium and normal + titanium + stainless steel. The CT numbers were compared between CT-rED tables normalraw and normal. CT images of 23 patientsi36 plans and 159 beams in totaljwere used. Monitor unitiMUjcalculations were performed using each CT-rED table and each patient’s data. The differences of the MUs acquired using the high-density material data relative to those of the MUs acquired using normal CT-rED table were calculated. Results: The changes in CT number due to MAR were very smalli0.1 ± 3.2 HUj. The greater the maximum rED input to the CT-rED table, the greater the variation of the calculated dose. Nevertheless, all relative differences were within 1%. Conclusion: The creation of a dedicated CT-rED conversion table for the CT images with single energy projection-based MAR techniques might not be necessary.

Key words :
Radiation therapy, computed tomography, CT number–relative electron density conversion table, metal artifact reduction technique

  Received December 10th, 2018 / Accepted after revision February 3rd, 2019

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