2022-07-01 17:23


Conference: Bucharest University Faculty of Physics 2019 Meeting

Section: Biophysics; Medical Physics

The calibration of relative electron density in radiotherapy treatment planning using computer assisted tomography

Mihai-Ştefan BÂRHALĂ (1), Cristina PETROIU (2), Florin COSTACHE (2)

1) Faculty of Physics, University of Bucharest, Măgurele, Romania

2) MNT Healthcare Europe SRL


Computed Tomography, Relative Electron Density, Houndsfield Units, Phantom

In the modern medicine it is necessary to perform an anatomical diagnostic of the modifications in human body, to obtain as many information as it is necessary, without damaging or harming the body. Physics, generally, Atomic and Nuclear Physics, mainly, offered solutions to do these types of investigations. Significant contributions in medical imagistics appeared in more than a century from the first works done by Roentgen using X-rays. Today, one of the main imagistic method, currently used, on a regular basis, in order to obtain qualitative anatomical information is Computer Assisted Tomography or Computerized Tomography (CT). Afterword, the utility of this method had expanded in many domains, playing an essential role in the radiotherapy, by using the images into the planning session. This raise of popularity and utility was due to the behavior of electromagnetic radiation (for example, X rays) while interacting with matter. By determining the linear coefficient of attenuation, through specialized calculus methods and by digitization of this data into 2D images, it is possible to integrate those images into the planning system. Within this process, the digital images are subjected to different virtual ionizing radiation beams, in order to determine the most suitable geometry and the irradiation method, so that the tumoral tissue can be destroyed completely. At the base of creating a safe treatment plan, from the point of view of the radiation dose absorbed by the patient, stands the electron density calibration curve. This calibration curve links the actual density of a tissue with its characteristic electronic density, used specifically in the planning system. This method of calibration consists of an automatic transformation of raw CT data into information that is used in radiotherapy treatment plans.

I like to thank to Alexandru Jipa, Cristina Petroiu and Florin Costache for the support in all the theoretical and experimental information.