A contrast-oriented algorithm for FDG-PET-based delineation of tumour volumes for the radiotherapy of lung cancer: derivation from phantom measurements and validation in patient data

  • Andrea SchaeferEmail author
  • Stephanie Kremp
  • Dirk Hellwig
  • Christian Rübe
  • Carl-Martin Kirsch
  • Ursula Nestle
Original Article



An easily applicable algorithm for the FDG-PET-based delineation of tumour volumes for the radiotherapy of lung cancer was developed by phantom measurements and validated in patient data.


PET scans were performed (ECAT-ART tomograph) on two cylindrical phantoms (phan1, phan2) containing glass spheres of different volumes (7.4–258 ml) which were filled with identical FDG concentrations. Gradually increasing the activity of the fillable background, signal-to-background ratios from 33:1 to 2.5:1 were realised. The mean standardised uptake value (SUV) of the region-of-interest (ROI) surrounded by a 70% isocontour (mSUV70) was used to represent the FDG accumulation of each sphere (or tumour). Image contrast was defined as:\(C = {{\left( {{\text{mSUV}}_{{\text{70}}} - {\text{BG}}} \right)} \mathord{\left/ {\vphantom {{\left( {{\text{mSUV}}_{{\text{70}}} - {\text{BG}}} \right)} {{\text{BG}}}}} \right. \kern-\nulldelimiterspace} {{\text{BG}}}}\) where BG is the mean background − SUV. For the spheres of phan1, the threshold SUVs (TS) best matching the known sphere volumes were determined. A regression function representing the relationship between TS/(mSUV70 − BG) and C was calculated and used for delineation of the spheres in phan2 and the gross tumour volumes (GTVs) of eight primary lung tumours. These GTVs were compared to those defined using CT.


The relationship between TS/(mSUV70 − BG) and C is best described by an inverse regression function which can be converted to the linear relationship \({\text{TS}} = a \times {\text{mSUV}}_{70} + b \times {\text{BG}}\). Using this algorithm, the volumes delineated in phan2 differed by only −0.4 to +0.7 mm in radius from the true ones, whilst the PET-GTVs differed by only −0.7 to +1.2 mm compared with the values determined by CT.


By the contrast-oriented algorithm presented in this study, a PET-based delineation of GTVs for primary tumours of lung cancer patients is feasible.


Volume delineation 18F-FDG PET Lung cancer GTV definition Radiotherapy Physics PET oncology therapy PET/CT 



We gratefully acknowledge the valuable help of Dipl. Ing. P. Donsch who constructed the phantoms. Furthermore, we thank Andrew Page for his help in the wording of the manuscript.

Conflict of interest statement

None of the authors has any conflict between his or his family’s financial interest and the content of this manuscript.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Andrea Schaefer
    • 1
    Email author
  • Stephanie Kremp
    • 2
  • Dirk Hellwig
    • 1
  • Christian Rübe
    • 2
  • Carl-Martin Kirsch
    • 1
  • Ursula Nestle
    • 1
  1. 1.Department of Nuclear MedicineSaarland University Medical CenterHomburgGermany
  2. 2.Department of RadiotherapySaarland University Medical CenterHomburgGermany

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