title: Calculating prescription doses for new sources by biologically effective dose matching.
abstract: OBJECTIVE
  In current clinical practice, single isotopes, such as (125)I or (103)Pd, are used as single sources in prostate seed implants. A mixture of two radionuclides in the seeds has been proposed for prostate cancer treatment. This study investigates a method for determining the prescription dose for these new seeds using the biological effective dose (BED).
  
  
  METHODS
  Ten prostate cancer cases previously treated using single radionuclide seeds were selected for this study. The BED distribution for these cases was calculated. Plans using other radionuclides were then calculated based on this BED distribution. Prescription values could then be obtained for the calculated plans. The method was verified by calculating the prescription dose for (103)Pd and (125)I and comparing to clinical values. The method was then applied to a hybrid seed that consisted of a mixture of (125)I and (103)Pd radionuclides, which deliver equal dose to 1cm from the source in water (50/50D@1 cm). A prescription BED value was also calculated.
  
  
  RESULTS
  A prescription BED of 110 Gy was found to correlate to a prescription dose of 145, 120, and 137 Gy for (125)I, (103)Pd, and 50/50D@1 cm hybrid seeds, respectively.
  
  
  CONCLUSIONS
  The method introduced in this article allows one to calculate the prescription dose for new and novel sources in brachytherapy. The method was verified by calculating a prescription dose for (125)I and (103)Pd radionuclides that coincides with values used clinically.
authors.affiliation: Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL 33612, USA.
authors.forename: Jakub
authors.initials: J
authors.lastname: Pritz
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Forster
authors.forename: Amarjit S
authors.initials: AS
authors.lastname: Saini
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Biagioli
authors.forename: Geoffrey G
authors.initials: GG
authors.lastname: Zhang
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D010165:Palladium / Q000627:therapeutic use*; D055656:Prescriptions; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011868:Radioisotopes / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D007457:Iodine Radioisotopes; D011868:Radioisotopes; D010165:Palladium