Quantitative positron emission tomography imaging in the presence of iodinated contrast media using electron density quantifications from dual‐energy computed tomography

• Published in: Medical physics (Lancaster) 2021-01, Vol.48 (1), p.273-286
• Main Authors: Shapira, Nadav, Scheuermann, Joshua, Perkins, Amy E., Kim, Johoon, Liu, Leening P, Karp, Joel S., Noël, Peter B.
• Format: Article
• Language: English
• Subjects: Biomarkers; Contrast Media; Electrons; IM‐ CT: {Dual Energy and Spectral; IM‐ PET: {Development (new technology and techniques); Iodine; Multi‐modality CT‐PET; Phantoms, Imaging; Positron Emission Tomography Computed Tomography; Positron-Emission Tomography; Quantitative imaging/analysis; Tomography, X-Ray Computed
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1002/mp.14589

Purpose As preparation for future positron emission tomography (PET)/dual‐energy computed tomography (DECT)T imaging modality and new possible clinical applications, the study aimed to evaluate the utility of clinically available spectral results from a DECT system for improving attenuation corrections of PET acquisitions in the presence of iodinated contrast media. The dependence of the accuracy of PET quantification values, reconstructed with conventional and spectral‐based attenuation corrections, was examined as a function of the amount of iodine content and x‐ray radiation exposure. Methods Measurements were performed on commercial PET/CT and DECT systems, using a semi‐anthropomorphic phantom with seven centrifuge tubes in its bore. Five different configurations of tube contents were scanned by both PET/CT and DECT. With the aim of mimicking clinically observed concentrations, in all phantom configurations the center tube contained a high concentration of radionuclide while the peripheral tubes contained a lower concentration of radionuclide. Iodine content was incrementally increased between phantom configurations by replacing iodine‐free tubes with tubes that contained the original radionuclide concentration within a 10 mg/ml iodine dilution. DECT‐based attenuation correction maps were generated by scaling electron density spectral results into corresponding 511 keV photon linear attenuation coefficients. Results Mean SUV values obtained from the nominal PET reconstruction, using conventional CT images as input for the attenuation correction, demonstrate a monotonic increase of 8.6% when the water and radionuclide mixtures were replaced by iodine, water, and radionuclide (same level of activity) mixture. Mean SUV values obtained from the DECT‐based reconstruction, in which the attenuation correction utilizes electron density values as input, demonstrate different, more stable behavior across all iodine insert configurations, with a standard deviation to mean ratio of less than 1%. This observed behavior was independent of the area size used for measurement. A minor radiation dose dependency of the electron density values (below 0.5%) was observed. This resulted in consistent (iodine independent) PET quantification behavior, which persisted even at the lowest radiation dose levels tested in our experiment, that is, 25% of the radiation dose utilized for CT acquisition in the clinical PET/CT protocol. Conclusions Utilization of DECT‐generated electron