PHSOR10 Presentation Time: 1:15 PM: Dosimetry Comparison Platform for Diffusing Alpha Emitters Radiation Therapy (DaRT) in Focal Prostate Brachytherapy

Abstract

<h3>Purpose</h3> Dosimetry calculation for diffusing alpha emitters radiation therapy (DaRT) is challenging because it needs to combine both diffusion modelling and radiation transport computation. We have developed a 3D dosimetry platform to compare standard focal Ir-192 HDR and Ra-224 DaRT dosimetry for real prostate focal brachytherapy cases. <h3>Materials and Methods</h3> For DaRT dose calculation, diffusion length data on prostate tumors was based on autoradiography measurements performed 4-5 days post treatment. Leakage probability was inferred from blood and urine measurements from DaRT patients. The MIM Symphony software (MIM Software Inc, Cleveland, OH) was installed for dosimetry calculation for both standard Ir-192 source and DaRT needles (AphaTAU Medical, Jerusalem, Israel) for treatment planning. For testing purposes, the dose calculation was performed on 5 focal prostate brachytherapy cases using the standard focal dosimetry technique. <h3>Results</h3> For DaRT dose calculation, TG-43 parameters were calculated in prostate for permanent implantation of 3 microCi needles: anisotropy function, dose-rate constant, radial-dose function and geometry function. For standard dose calculation, parameters used in MIM Symphony were validated with our clinical Oncentra platform. For 5 patients, standard focal HDR brachytherapy dosimetry calculation was performed retroactively. Prescription doses were 13 or 15 Gy at the PTV. Doses to organs at risk were also evaluated: Urethra D10% (16-91%) and Rectum V75cc (0-0,6 cc), for example. <h3>Conclusions</h3> A 3D dose calculation technique was developed for DaRT based on diffusion modelling and radiation transport. With the use of this technique integrated into the MIM Symphony treatment planning software, we have developed a 3D dosimetry comparison platform for DaRT and standard (HDR or LDR) prostate brachytherapy. The advantage of DaRT for OAR protection can thus be retrospectively studied with this platform on a cohort of prostate patients from our clinic.