New Dual Energy Quantitative Computed Tomography Method for Measuring the Volume Fractions of Fat, Water and Mineral Bone for Bone Marrow Dosimetry

Ziel/Aim This study describes a new phantom-independent dual-energy quantitative computed tomography (PI-DEQCT) method to quantify the volume fractions of fat, water, and mineral bone. This enables the application of patient-specific radionuclide S values in bone marrow dosimetry.

Methodik/Methods First, an equation to calculate Hounsfield Units (HU) based on the parametrization of the photon cross-sections of the elements that make up human tissues in the range of diagnostic x-ray energies was determined using an electron density phantom. Second, the HU for fat tissue, water, and mineral bone were calculated for two typical kilovoltage peak values of clinical (SPECT/)CT systems (80 kVp and 130kVp). Third and last, an empirical function that corrects for beam hardening was estimated. The method was implemented in a (SPECT/)CT system (Intevo Bold, Siemens Healthineers). The quantification of the volume fraction of fat, water, and mineral bone was performed in the spongiosa region of the femoral necks of two bones of an adult boar. The volume fraction measurements were compared with a phantom-dependent DEQCT method (here, a phantom of known fat, water, and mineral bone volume fractions is measured simultaneously with the object under investigation). The calculated effective atomic number (Z_eff) and the effective density (Rho_eff) from the presented PI-DEQCT method were compared with the results obtained with a commercially available tool (syngo.CT DE Rho/Z, Siemens Healthineers).

Ergebnisse/Results The relative errors between both DEQCT methods were 2 %/−1 %, 5 %/4 % and −18 %/−16 % (bone 1/bone 2) for fat, water and mineral bone, respectively. The Z_eff/Rho_eff values showed a good agreement between PI-DEQCT and the Rho/Z tool (relative errors 5 %/-11 % [bone 1] and 5 %/-10 % [bone 2]).

Schlussfolgerungen/Conclusions The good agreement between both DEQCT methods demonstrates that fat, water, and mineral bone can be quantified with an accuracy sufficient for internal dosimetry using a dual-energy (SPECT/)CT system.

Publication History

Article published online:
08 April 2021