Patient specific treatment planning for systemically administered radiopharmaceuticals using PET/CT and Monte Carlo simulation.

The efficacy of systemically administered radiopharmaceuticals depends on the physiological path of the targeting molecule and the physical characteristics of the attached radionuclide. NM404 is a candidate for patient specific dosimetry because it can be used concurrently for both diagnosis and therapy. Radiolabeling NM404 with [(124)I] affords the possibility of performing noninvasive PET imaging while [(131)I] allows for radiotherapy. Patient specific dosimetry for radiation treatment planning for NM404 uses serial PET/CT data and Monte Carlo. [(124)I]NM404 PET helps to determine the organ at risk by which the maximum injected activity of [(131)I]NM404 will depend. The subsequent work uses a software interface (SCMS) to convert patient PET/CT data of a liver metastasis into a Monte Carlo environment for radiation transport analysis. Thereby, the dosimetry within the liver and tumor during both diagnostic and therapeutic procedures was determined. The results showed that per MBq injected of [(124)I] and [(131)I], the tumor receives an average of 1.2 and 1.5mGy, respectively, while the liver receives 0.031 and 0.022mGy, respectively.