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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 17:49 |
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Conference: Bucharest University Faculty of Physics 2022 Meeting
Section: Biophysics; Medical Physics
Title:
The effect of the CT calibration curve on patient dose distributions
Authors:
Marius-Valentin COSTACHE, Tia POPESCU, Ionuț DUMITRU, Vasile BERCU, Leonard GEBAC
*
Affiliation:
MNT Healthcare – Neolife
E-mail
cm.valentin299@gmail.com
Keywords:
Computed tomography, dose distributions, Hounsfield units, TPS
Abstract:
X-ray computed tomography (CT) is the most common source of information about the exact locations of tumor sites. Many factors, such as inhomogeneity and overlapping of patient’s body tissues, can have a major effect on dose distributions. In order to achieve accurate dose distributions in image-based treatment planning for patients undergoing external-beam radiotherapy, it is necessary to obtain the relationship between the CT numbers and electron densities, as the input for the treatment planning system (TPS). The CT number, expressed in Hounsfield units, is a normalized value of the linear attenuation coefficient of each voxel (pixel volume) of a CT image. The corrections of tissue inhomogeneity are obtained by establishing a calibration curve from CT images of an electron density phantom that has various tissue equivalent materials with known physical properties and densities in the range of those of real human tissues. Multiple calibration curves were obtained in order to observe the influence of tube voltages (kVp) and currents (mA) on the measurement of Hounsfield units and the quality of the images. Hence, the Hounsfield units of all the rods with different known electron densities were determined experimentally using a defined region of interest (ROI) for all the measurements. Each ROI was considered in the middle of each material, away from the edges to avoid partial volume effects that could influence the outcome. The results indicated that in low densities, such as lungs and soft tissues, there was no observable difference between the curves, but by increasing the densities and approaching the bone densities, the differences in HU units were revealed.
References:
https://inis.iaea.org/collection/NCLCollectionStore/_Public/43/056/43056417.pdf
https://www.researchgate.net/publication/332755637_Evaluation_of_CT_calibration_curves_from_stoichiometric_and_tissue_substitute_methods_according_to_tissue_characteristics
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