Technical background of a novel detector-based approach to dual-energy computed tomography

Hokamp, Nils Große; Maintz, David; Shapira, Nadav; Chang, De Hua; Noël, Peter B.

doi:10.5152/dir.2019.19136

Cited by 63 publications

(48 citation statements)

References 7 publications

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Section: Introductionmentioning

confidence: 99%

“…Dual-energy CT has been extensively researched in the last decade and enables reconstruction of virtual non-contrast (VNC) images, which can be understood as image interpolations from which the iodine-specific signal has been subtracted [17][18][19]. Such VNC images are available for all clinical implementations of DECT as proprietary reconstruction algorithm based upon three-material decomposition [17,20]. Previous studies demonstrated a high reliability of dualenergy CT-derived VNC images and excellent correlations between attenuation values in VNC and true non-contrast images irrespective of iodine concentration [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

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Evaluating anemia using contrast-enhanced spectral detector CT of the chest in a large cohort of 522 patients

et al. 2020

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Objectives The blood of patients with anemia demonstrates distinctly lower attenuation in unenhanced CT images. However, the frequent usage of intravenous contrast hampers evaluation of anemia. Spectral detector computed tomography (SDCT) allows for reconstruction of virtual non-contrast images (VNC) from contrast-enhanced data (CE). The purpose of this study was to evaluate whether VNC allow for prediction of anemia. Methods Five hundred twenty-two patients with CE-SDCT of the chest and accessible serum hemoglobin (HbS) were retrospectively included. Patients were assigned to three groups (severe anemia, moderate/mild anemia, and healthy) based on recent lab tests (≤ 7 days) for HbS following gender and the WHO definition of anemia. CT attenuation was determined using two ROI in the left ventricular lumen and one ROI in the descending thoracic aorta. ROI were placed on CE and copied to VNC. ANOVA, linear regression, and receiver operating characteristics were used for statistic evaluation. Results Average HbS was 11.6 ± 2.4 g/dl. Attenuation on VNC showed significant differences between healthy patients, patients with mild/moderate anemia, and severely anemic patients (all p ≤ 0.05). Applying cutoffs of 39.2/37.6 HU and 33.6/32.7 HU allowed to differentiate between healthy, mild/moderately, and severely anemic men/women (AUC 0.857/0.833 and 0.879/0.932). A linear relationship between HbS and attenuation on VNC was established (r2 = 0.54, HbS = − 0.875 + 0.329 × HU). Conclusions An approximation of HbS and presence of anemia can be conducted based on simple attenuation measurements in contrast-enhanced SDCT examinations enabled by VNC imaging. Key Points • While the attenuation of blood is a previously described biomarker for anemia in non-contrast images, virtual non-contrast images from spectral detector CT circumvent this limitation and allow for diagnosis of anemia in contrast-enhanced scans. • Attenuation of blood in virtual non-contrast images derived from spectral detector CT shows a moderate correlation to serum hemoglobin levels. • Presence of anemia be estimated in virtual non-contrast images using proposed cutoffs of 39.2 HU and 37.6 HU for men and women, respectively, to differentiate between healthy and anemic patients.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluating anemia using contrast-enhanced spectral detector CT of the chest in a large cohort of 522 patients

et al. 2020

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“…Detector materials and thicknesses were designed to result in equal noise levels for scans of typical body sizes. Spectral information with sufficient energy separation is acquired at every 120 or 140 kVp scan, eliminating the need to prospectively modify scan parameters in order to enable a DECT acquisition mode 53 . Several spectral results are available both prospectively and retrospectively.…”

Section: Methodsmentioning

confidence: 99%

“…Spectral information with sufficient energy separation is acquired at every 120 or 140 kVp scan, eliminating the need to prospectively modify scan parameters in order to enable a DECT acquisition mode. 53 Several spectral results are available both prospectively and retrospectively. These include virtual mono-energetic images (VMI) at photon energy levels of 40 to 200 keV, iodine density maps, Virtual Non-Contrast images, effective atomic number images, and ED images.…”

Section: A Scannersmentioning

confidence: 99%

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

et al. 2020

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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 density estimations for attenuation correction benefit PET quantification consistency in the presence of iodine and at nominal and low DECT radiation exposure levels. The ability to correctly account for iodinated contrast media in PET acquisitions will allow the development of new clinical applications that rely on the quantitative capabilities of spectral CT technologies and modern PET systems.

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“…Furthermore, tumor vascularization is an important diagnostic aspect in assessment of treatment response in some tumors [7][8][9]. Dual-energy computed tomography (DECT) allows for an accurate and reliable quantification of iodine and therefore provides information regarding the distribution of iodinated contrast media [10][11][12][13][14][15]. Accuracy of iodine quantification has been demonstrated for all different technical approaches to DECT [12,16,17].…”

Section: Introductionmentioning

confidence: 99%

Quantitative distribution of iodinated contrast media in body computed tomography: data from a large reference cohort

et al. 2020

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Objectives Dual-energy computed tomography allows for an accurate and reliable quantification of iodine. However, data on physiological distribution of iodine concentration (IC) is still sparse. This study aims to establish guidance for IC in abdominal organs and important anatomical landmarks using a large cohort of individuals without radiological tumor burden. Methods Five hundred seventy-one oncologic, portal venous phase dual-layer spectral detector CT studies of the chest and abdomen without tumor burden at time point of imaging confirmed by > 3-month follow-up were included. ROI were placed in parenchymatous organs (n = 25), lymph nodes (n = 6), and vessels (n = 3) with a minimum of two measurements per landmark. ROI were placed on conventional images and pasted to iodine maps to retrieve absolute IC. Normalization to the abdominal aorta was conducted to obtain iodine perfusion ratios. Bivariate regression analysis, t tests, and ANOVA with Tukey-Kramer post hoc test were used for statistical analysis. Results Absolute IC showed a broad scatter and varied with body mass index, between different age groups and between the sexes in parenchymatous organs, lymph nodes, and vessels (range 0.0 ± 0.0 mg/ml–6.6 ± 1.3 mg/ml). Unlike absolute IC, iodine perfusion ratios did not show dependency on body mass index; however, significant differences between the sexes and age groups persisted, showing a tendency towards decreased perfusion ratios in elderly patients (e.g., liver 18–44 years/≥ 64 years: 0.50 ± 0.11/0.43 ± 0.10, p ≤ 0.05). Conclusions Distribution of IC obtained from a large-scale cohort is provided. As significant differences between sexes and age groups were found, this should be taken into account when obtaining quantitative iodine concentrations and applying iodine thresholds. Key Points • Absolute iodine concentration showed a broad variation and differed between body mass index, age groups, and between the sexes in parenchymatous organs, lymph nodes, and vessels. • The iodine perfusion ratios did not show dependency on body mass index while significant differences between sexes and age groups persisted. • Provided guidance values may serve as reference when aiming to differentiate healthy and abnormal tissue based on iodine perfusion ratios.

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Technical background of a novel detector-based approach to dual-energy computed tomography

Cited by 63 publications

References 7 publications

Evaluating anemia using contrast-enhanced spectral detector CT of the chest in a large cohort of 522 patients

Evaluating anemia using contrast-enhanced spectral detector CT of the chest in a large cohort of 522 patients

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

Quantitative distribution of iodinated contrast media in body computed tomography: data from a large reference cohort

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