Inter- and intrafractional localisation errors in cone-beam CT guided stereotactic radiation therapy of tumours in the liver and lung

Acta Oncol. 2010 Oct;49(7):1177-83. doi: 10.3109/0284186X.2010.498435.


Background: Localisation errors in cone-beam CT (CBCT) guided stereotactic body radiation therapy (SBRT) were evaluated and compared to positioning using the external coordinates of a stereotactic body frame (SBF) alone. Possible correlations to patient- or treatment-specific factors such as body mass index (BMI), planning time, treatment delivery time, and distance between tumour and spinal cord were explored to determine whether they influenced on the benefit of image-guidance.

Material and methods: A total of 34 patients received SBRT (3 fractions) for tumours in the liver (15 patients) or the lung (19 patients). Immobilisation and positioning was obtained with a SBF. Pre- and post-treatment CBCT scans were registered with the bony anatomy of the planning CT to find inter- and intrafractional patient positioning errors (PPE). For lung tumour patients, matching was also performed on the tumours to find the tumour positioning errors (TPE) and baseline shifts relative to bony anatomy.

Results: The mean inter- and intrafractional 3D vector PPE was 4.5 ± 2.7 mm (average ± SD) and 1.5 ± 0.6 mm, respectively, for the combined group of patients. For lung tumours, the interfractional misalignment was 5.6 ± 1.8 mm. The baseline shift was 3.9 ± 2.0 mm. Intrafractional TPE and baseline shifts were 2.1 ± 0.7 mm and 1.9 ± 0.6 mm, respectively. The magnitude of interfractional baseline shift was closely correlated with the distance between the tumour and the spinal cord. Intrafractional errors were independent of patient BMI, age or gender.

Conclusion: Image-guidance reduced setup errors considerably. The study demonstrated the benefit of CBCT-guidance regardless of patient specific factors such as BMI, age or gender. Protection of the spinal cord was facilitated by the correlation between the tumour position relative to the spinal cord and the magnitude of baseline shift.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bile Duct Neoplasms / diagnostic imaging
  • Bile Duct Neoplasms / pathology
  • Bile Duct Neoplasms / secondary
  • Bile Duct Neoplasms / surgery
  • Bile Ducts, Intrahepatic / diagnostic imaging
  • Bile Ducts, Intrahepatic / pathology
  • Carcinoma, Non-Small-Cell Lung / diagnostic imaging
  • Carcinoma, Non-Small-Cell Lung / surgery
  • Cholangiocarcinoma / diagnostic imaging
  • Cholangiocarcinoma / pathology
  • Cholangiocarcinoma / secondary
  • Cholangiocarcinoma / surgery
  • Cohort Studies
  • Cone-Beam Computed Tomography / methods*
  • Cone-Beam Computed Tomography / standards
  • Diagnostic Errors
  • Dose Fractionation, Radiation
  • Female
  • Humans
  • Image Processing, Computer-Assisted / methods
  • Imaging, Three-Dimensional / methods
  • Liver Neoplasms / diagnostic imaging*
  • Liver Neoplasms / pathology
  • Liver Neoplasms / secondary
  • Liver Neoplasms / surgery
  • Lung Neoplasms / diagnostic imaging*
  • Lung Neoplasms / pathology
  • Lung Neoplasms / secondary
  • Lung Neoplasms / surgery
  • Male
  • Radiosurgery / methods*
  • Radiotherapy Planning, Computer-Assisted / methods*
  • Tumor Burden / radiation effects