Effect of patient size on image quality in radiotherapy kV planar verification imaging: a phantom study

J Med Radiat Sci. 2020 Mar;67(1):34-42. doi: 10.1002/jmrs.355. Epub 2019 Oct 16.


Introduction: This study aimed to determine a maximal pelvic separation and waist circumference in pelvic patients to guide radiation therapists in acquiring kilovoltage (kV) planar images of acceptable quality for treatment verification.

Methods: A pelvic anthropomorphic phantom modified with different bolus thicknesses was imaged at various default kV exposure settings. Radiation therapists rated image quality and acceptance/rejection of these images for treatment verification.

Results: Sixteen radiation therapists participated in the study. Image quality was inversely proportional to phantom size. AP and lateral kV images were acceptable for treatment verification up to a waist circumference of 143 cm.

Conclusions: Exposure settings for kV image verification of large patients should be individualised to avoid unnecessary patient radiation dose through repeated imaging.

Keywords: image interpretation; image-guided radiotherapy; phantoms; waist circumference.

MeSH terms

  • Female
  • Humans
  • Male
  • Observer Variation
  • Pelvis / diagnostic imaging
  • Phantoms, Imaging / standards
  • Radiotherapy, Image-Guided / instrumentation
  • Radiotherapy, Image-Guided / standards*
  • Reproducibility of Results
  • Tomography, X-Ray Computed / instrumentation
  • Tomography, X-Ray Computed / standards*
  • Waist Circumference*