Tissue heterogeneity in IMRT dose calculation for lung cancer

Katia Pasciuti, Giuseppe Iaccarino, Lidia Strigari, Tiziana Malatesta, Marcello Benassi, Anna Maria Di Nallo, Alessandra Mirri, Valentina Pinzi, Valeria Landoni

Research output: Contribution to journalArticlepeer-review


The aim of this study was to evaluate the differences in accuracy of dose calculation between 3 commonly used algorithms, the Pencil Beam algorithm (PB), the Anisotropic Analytical Algorithm (AAA), and the Collapsed Cone Convolution Superposition (CCCS) for intensity-modulated radiation therapy (IMRT). The 2D dose distributions obtained with the 3 algorithms were compared on each CT slice pixel by pixel, using the MATLAB code (The MathWorks, Natick, MA) and the agreement was assessed with the γ function. The effect of the differences on dose-volume histograms (DVHs), tumor control, and normal tissue complication probability (TCP and NTCP) were also evaluated, and its significance was quantified by using a nonparametric test. In general PB generates regions of over-dosage both in the lung and in the tumor area. These differences are not always in DVH of the lung, although the Wilcoxon test indicated significant differences in 2 of 4 patients. Disagreement in the lung region was also found when the Γ analysis was performed. The effect on TCP is less important than for NTCP because of the slope of the curve at the level of the dose of interest. The effect of dose calculation inaccuracy is patient-dependent and strongly related to beam geometry and to the localization of the tumor. When multiple intensity-modulated beams are used, the effect of the presence of the heterogeneity on dose distribution may not always be easily predictable.

Original languageEnglish
Pages (from-to)219-227
Number of pages9
JournalMedical Dosimetry
Issue number2
Publication statusPublished - 2011


  • Dose calculation algorithms
  • IMRT
  • NTCP
  • TCP

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology


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