Sara Ng Lim, Presenter: Nothing to Disclose

Anil Pradhan, Abstract Co-Author: Nothing to Disclose

Maximiliano Montenegro, Abstract Co-Author: Nothing to Disclose

Sultana N Nahar, Abstract Co-Author: Nothing to Disclose

Erica H Bell, Abstract Co-Author: Nothing to Disclose

Claudia Turro, Abstract Co-Author: Nothing to Disclose

Rolf Frederick Barth MD, Abstract Co-Author: Nothing to Disclose

Yan Yu PhD, MBA, Abstract Co-Author: Nothing to Disclose

  To compare the cell-killing ability of broadband and monochromatic X-ray sources with radiosensitization using a heavy element (high Z) compound/nanoparticle.

  Monte Carlo simulations for X-ray energy absorption and dose deposition in tissue phantoms were carried out using the Geant4 code for 100 kV, 170 kV and 6 MV broadband X-ray sources. The potential dose enhancement factor (DEF) of HZ-radiosensitizers was calculated using a fixed 7μg/ml platinum concentration for the radiosensitized tumor phantom. In-vitro experiments were performed to compare Pt-sensitized cell survival for irradiation using either a 160 kV or a 6 MV broadband source. In addition, Monte Carlo simulations were performed for potential dose enhancement using targeted monochromatic x-rays.

  The simulations show that dose enhancement using platinum are significant only in low energy region of about 40-90 keV, confirming previous simulations for gold nanoparticles. Preliminary in-vitro results has shown more cell death using 160 kV X-rays relative to 6 MV in cells treated with a Pt drug. In addition, irradiation with the 6 MV linac showed no additional cell death above the IC50, while irradiation with the 160 kV showed a decrease in cell survival at the same drug concentration.

  Due to much higher photoelectric cross sections and higher photon flux in the 40-90 keV range, total DEFs for the 160 kV source were much greater than for the 6 MV range. In addition, simulations using monochromatic X-rays have shown several orders of magnitude higher attenuation using a twin beam X-ray tuned to the Kα and the K-edge, suggeting the use of tuned X-rays to be far more effective than broadband sources. 

Using tuned X-rays targeted to heavy element radiosensitizers allow for much greater radiation dose to tumor tissue. Damage to healthy tissue is minimized, yet greater therapeutic effects achieved.

Lim, S, Pradhan, A, Montenegro, M, Nahar, S, Bell, E, Turro, C, Barth, R, Yu, Y, Monochromatic and Broadband X-ray Irradiation of Heavy Element Radiosensitizers: Simulations and In-vitro Studies for Therapeutic Efficacy.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043863.html