Influence of total-body mass on the scaling of S-factors for patient-specific, blood-based red-marrow dosimetry

A. C. Traino, M. Ferrari, M. Cremonesi, M. G. Stabin

Research output: Contribution to journalArticlepeer-review


To perform patient-specific, blood-based red-marrow dosimetry, dose conversion factors (the S factors in the MIRD formalism) have to be scaled by patients' organ masses. The dose to red marrow includes both self-dose and cross-irradiation contributions. Linear mass scaling for the self-irradiation term only is usually applied as a first approximation, whereas the cross-irradiation term is considered to be mass independent. Recently, the need of a mass scaling correction on both terms, not necessarily linear and dependent on the radionuclide, has been highlighted in the literature. S-factors taking into account different mass adjustments of organs are available in the OLINDA/EXM code. In this paper, a general algorithm able to fit the mass-dependent factors Srm←tb and Srm←rm is suggested and included in a more general equation for red-marrow dose calculation. Moreover, parameters to be considered specifically for therapeutic radionuclides such as 131I, 90Y and 177Lu are reported. The red-marrow doses calculated by the traditional and new algorithms are compared for 131I in ablation therapy (14 pts), 177Lu- (13 pts) and 90Y- (11 pts) peptide therapy for neuroendocrine tumours, and 90Y-Zevalin therapy for NHL (21 pts). The range of differences observed is as follows: -36% to -10% for 131I ablation, -22% to 5% for 177Lu-DOTATATE, -9% to 11% for 90Y-DOTATOC and -8% to 6% for 90Y-Zevalin. All differences are mostly due to the activity in the remainder of the body contributing to cross-irradiation. This paper quantifies the influence of mass scaling adjustment on usually applied therapies and shows how to derive the appropriate parameters for other radionuclides and radiopharmaceuticals.

Original languageEnglish
Pages (from-to)5231-5248
Number of pages18
JournalPhysics in Medicine and Biology
Issue number17
Publication statusPublished - Sep 7 2007

ASJC Scopus subject areas

  • Biomedical Engineering
  • Physics and Astronomy (miscellaneous)
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology


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