Effect of body mass index on shifts in ultrasound-based image-guided intensity-modulated radiation therapy for abdominal malignancies

Mehee Choi, Clifton D. Fuller, Samuel J. Wang, Ather Siddiqi, Adrian Wong, Charles R. Thomas, Martin Fuss

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Background and purpose: We investigated whether corrective shifts determined by daily ultrasound-based image-guidance correlate with body mass index (BMI) of patients treated with image-guided intensity-modulated radiation therapy (IG-IMRT) for abdominal malignancies. The utility of daily image-guidance, particularly for patients with BMI > 25.0, is examined. Materials and methods: Total 3162 ultrasound-directed shifts were performed in 86 patients. Direction and magnitude of shifts were correlated with pretreatment BMI. Bivariate statistical analysis and analysis of set-up correction data were performed using systematic and random error calculations. Results: Total 2040 daily alignments were performed. Average 3D vector of set-up correction for all patients was 12.1 mm/fraction. Directional and absolute shifts and 3D vector length were significantly different between BMI cohorts. 3D displacement averaged 4.9 mm/fraction and 6.8mm/fraction for BMI ≤ 25.0 and BMI > 25.0, respectively. Systematic error in all axes and 3D vector was significantly greater for BMI > 25.0. Differences in random error were not statistically significant. Conclusions: Set-up corrections derived from daily ultrasound-based IG-IMRT of abdominal tumors correlated with BMI. Daily image-guidance may improve precision of IMRT delivery with benefits assessed for the entire population, particularly patients with increased habitus. Requisite PTV margins suggested in the absence of daily image-guidance are significantly greater in patients with BMI > 25.0.

Original languageEnglish (US)
Pages (from-to)114-119
Number of pages6
JournalRadiotherapy and Oncology
Issue number1
StatePublished - Apr 2009
Externally publishedYes


  • Body mass index (BMI)
  • Image-guided radiotherapy (IGRT)
  • Intensity-modulated radiation therapy (IMRT)
  • Patient positioning
  • Ultrasound

ASJC Scopus subject areas

  • Hematology
  • Oncology
  • Radiology Nuclear Medicine and imaging


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