ESTRO 2024 - Abstract Book

S3815

Physics - Image acquisition and processing

ESTRO 2024

Figure 2. Aortic HU curve as a function of time.

Conclusion:

An individually synchronized contrast 4D-CT simulation proved to be feasible and resulted in optimal tumor enhancement and vessels definition over the whole patient’s breathing cycle. The main limitation is that the optimal tumor contrast is highly dependent on the correct calculation of the delay time from contrast injection to CT scan. Nonetheless, our approach improves the accuracy of target volume definition and mitigates uncertainties in radiotherapy planning, by addressing the challenges associated with poor target visibility and respiratory motion. As a result, it allows for the administration of more aggressive doses within SBRT regimens, at the cost of a small investment of resources.

Keywords: Contrast-enhanced, Target Definition, Abdomen SBRT

926

Digital Poster

Does patient size affect the CT-numbers of bones?

Erik Pettersson 1,2 , Ola Norrlid 3 , Christina Vallhagen Dahlgren 4 , Anna Bäck 1,2

1 Department of Medical Radiation Sciences, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. 2 Therapeutic Radiation Physics, Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden. 3 Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden. 4 The Skandion Clinic, ,, Uppsala, Sweden

Purpose/Objective:

The voxel values in single-energy CT (SECT) images are generally displayed as CT numbers which represent photon attenuation relative to water. Dual-energy CT (DECT) can produce new image types where the CT numbers instead represent the physical mass density, electron density or proton stopping power ratio (SPR). Regardless of whether we use SECT or DECT images for the absorbed dose calculation in radiotherapy, we wish them to be independent of the transversal size (i.e., effective diameter) of the patient. In practice, the CT scan protocols are often designed separately for different patient sizes (e.g., head and body) for different treatment sites. This is not optimal when patients’ treatment fields include both the head and shoulders, such as treatment in the head-and-neck region or craniospinal irradiation (CSI). This study uses a novel phantom setup geometry of an electron density phantom with a combined head and body geometry to evaluate how the patient size affects the SECT CT-numbers and DECT SPR images of bone from three CT scanners.

Material/Methods: