Evaluation of Hounsfield Numbers and Electron Density for a CT Simulator and Their Importance for Radiotherapy Treatments

ORIGINAL ARTICLE
Blerim Rrakaqi, Ervis Telhaj, Njomza Elezaj, Ylli Kaçiu, Besim Xhafa, Naser Gjonbalaj, Armend Jashari, Ismet Bajrami, Ardian Kadolli, Bujar Imeri, Florentina Hamidi, Ramiz Ukaj

 
For citation: Rrakaqi B, Telhaj E, Elezaj N, Kaçiu Y, Xhafa B, Gjonbalaj N, Jashari A, Bajrami I, Kadolli A, Imeri B, Hamidi D, Ukaj R. Evaluation of Hounsfield Numbers and Electron Density for a CT Simulator and Their Importance for Radiotherapy Treatments. International Journal of Biomedicine. 2025;15(2):358-363. doi:10.21103/Article15(2)_OA14
 
Originally published June 5, 2025
 

Abstract: 

Since its introduction in the early 1970s, computed tomography (CT) has significantly improved accuracy in radiotherapy planning by enhancing geometric volume definitions and dose calculation distributions. CT scans provide a distribution of attenuation values relative to water, measured in Hounsfield units (HUs), which correlate with the linear attenuation coefficient (μ). These coefficients depend on the electron density and elemental composition of the tissues.
Using fundamental physical information, such as the size, shape, and location of inhomogeneities in anatomical structures combined with HU values from the CT scan, the data is integrated into the treatment-planning system's database. This integration enables precise planning for radiotherapy treatments. To establish the HU scale for our CT simulator, our medical physics department scanned the CIRS phantom. By analyzing the phantom images, we determined the HU calibration curve for our CT-Sim system. Using this calibration, along with data from our medical linear accelerator, we created specific photon treatment beams for radiotherapy applications.

Keywords: 
Hounsfield number • CIRS phantom • CT – Sim • photon beam
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Received March 25, 2025.
Accepted May 26, 2025.
©2025 International Medical Research and Development Corporation.