18F-FDG-PET-based tumor delineation in cervical cancer: threshold contouring and lesion volumes

Rev Esp Med Nucl Imagen Mol. 2013 May-Jun;32(3):162-6. doi: 10.1016/j.remn.2012.06.003. Epub 2012 Jul 24.

Abstract

Objective: To evaluate a semi-automated PET-image tumor segmentation algorithm for gross tumor volume (GTV) delineation in patients with locally advanced cervical cancer.

Material and methods: Thirty-two patients with locally advanced cervical cancer were retrospectively evaluated. Semi-automated PET-image-based GTV delineation was applied using a previous established algorithm (GTV2SD) and 2 fixed threshold-based methods (GTV40% and GTV50%). GTV2SD was determined as the pixel with the mean value plus 2-standard deviation of the liver intensity, and GTV40% and GTV50% with 40% and 50% of the maximum tumor intensity (Tmax), respectively. The derived volumes were then compared with the GTVs generated manually using MR (GTVMR).

Results: The mean value of GTV2SD, GTV40% and GTV50% was 85.3cc, 16.2cc and 24.1cc, respectively. Good agreement was noticed between GTV2SD and GTVMR (ρ=0.88). GTV40% and GTV50% showed weaker correlation with GTVMR (ρ=0.68 and ρ=0.71, respectively).

Conclusions: This study provides preliminary evidence that metabolic tumor volume delineation is feasible using computer-generated measurements in (18)F-FDG PET images. Generation of PET-based tumor volumes is affected by the choice of threshold level used. Metabolic tumor bulk calculated using the pixel with the mean value plus 2-standard deviations of the liver intensity (GTV2SD) correlates better with the MR-derived tumor volumes. The method is a simple and clinically applicable approach to generate PET-derived GTV for radiation therapy planning of cervical cancer.

MeSH terms

  • Adult
  • Aged
  • Algorithms*
  • Female
  • Fluorodeoxyglucose F18*
  • Humans
  • Middle Aged
  • Multimodal Imaging*
  • Positron-Emission Tomography*
  • Radiopharmaceuticals*
  • Retrospective Studies
  • Tumor Burden*
  • Uterine Cervical Neoplasms / diagnosis*

Substances

  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18