Accuracy of electron density, effective atomic number, and iodine concentration determination with a dual‐layer dual‐energy computed tomography system

Hua, Chia‐Ho; Shapira, Nadav; Merchant, Thomas E.; Klahr, Paul; Yagil, Yoad

doi:10.1002/mp.12903

Cited by 98 publications

(125 citation statements)

References 29 publications

(38 reference statements)

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“…Less attention has been paid to other DECT technologies such as rapid kV switching or dual‐layer (DL) detectors, even though the latter allows for projection‐based DECT algorithms, which are potentially superior to image‐based procedures . DL‐DECT has recently been studied by Hua et al . in terms of relative electron density (RED) and effective atomic number (EAN) accuracy and was found comparable to dual‐source DECT.…”

Section: Introductionmentioning

confidence: 99%

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Technical Note: Relative proton stopping power estimation from virtual monoenergetic images reconstructed from dual‐layer computed tomography

et al. 2019

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Purpose: The objective of this technical note was to investigate the accuracy of proton stopping power relative to water (RSP) estimation using a novel dual-layer, dual-energy computed tomography (DL-DECT) scanner for potential use in proton therapy planning. DL-DECT allows dual-energy reconstruction from scans acquired at a single x-ray tube voltage V by using two-layered detectors. Methods: Sets of calibration and evaluation inserts were scanned at a DL-DECT scanner in a custom phantom with variable diameter D (0 to 150 mm) at V of 120 and 140 kV. Inserts were additionally scanned at a synchrotron computed tomography facility to obtain comparative linear attenuation coefficients for energies from 50 to 100 keV, and reference RSP was obtained using a carbon ion beam and variable water column. DL-DECT monoenergetic (mono-E) reconstructions were employed to obtain RSP by adapting the Yang-Saito-Landry (YSL) method. The method was compared to reference RSP via the root mean square error (RMSE) over insert mean values obtained from volumetric regions of interest. The accuracy of intermediate quantities such as the relative electron density (RED), effective atomic number (EAN), and the mono-E was additionally evaluated. Results: The lung inserts showed higher errors for all quantities and we report RMSE excluding them. RMSE for l from DL-DECT mono-E was below 1.9%. For the evaluation inserts at D = 150 mm and V = 140 kV, RED RMSE was 1.0%, while for EAN it was 2.9%. RSP RMSE was below 0.8% for all D and V, which did not strongly affect the results. Conclusions: In this investigation of RSP accuracy from DL-DECT, we have shown that RMSE below 1% can be achieved. It was possible to adapt the YSL method for DL-DECT and intermediate quantities RED and EAN had comparable accuracy to previous publications.

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Section: Introductionmentioning

confidence: 99%

“…In this technical note, we aimed at adapting a methodology for RSP estimation to DL‐DECT data. We employed a different RED formalism than Hua et al . (also used by Ohira et al …”

Section: Introductionmentioning

confidence: 99%

Technical Note: Relative proton stopping power estimation from virtual monoenergetic images reconstructed from dual‐layer computed tomography

et al. 2019

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“…Compton is the predominant interaction throughout the x-ray energy spectrum for all materials with a Z of below about 10-15, whereas photoelectric effect dominates at all x-ray energies for Z of about >15-25 [6]. The effective atomic number (Zeff) of human soft tissue (excluding fat) is close to water and varies very little: water, blood, brain-, heart-, kidney-, liver-, lung-, muscle-, pancreas-and spleen-tissue are all within the Zeff-interval of about 7.33-7.55 [7,8], which means that image contrast between these objects, or between these objects and lesions of similar Zeff, will almost entirely be determined by their often very small density differences, unless CM is used. Some relevant bodily materials with deviating Zeff are fat and non-soft-tissue objects like bone and calcium-based kidney stones with Zeff of about 6, 9-13 and 11-15 respectively [7,9]).…”

Section: Physical Principle Of CMmentioning

confidence: 99%

“…The effective atomic number (Zeff) of human soft tissue (excluding fat) is close to water and varies very little: water, blood, brain-, heart-, kidney-, liver-, lung-, muscle-, pancreas-and spleen-tissue are all within the Zeff-interval of about 7.33-7.55 [7,8], which means that image contrast between these objects, or between these objects and lesions of similar Zeff, will almost entirely be determined by their often very small density differences, unless CM is used. Some relevant bodily materials with deviating Zeff are fat and non-soft-tissue objects like bone and calcium-based kidney stones with Zeff of about 6, 9-13 and 11-15 respectively [7,9]). Figure 2 shows the mass attenuation coefficients for iodine, bone and water (left side) and the estimated more realistic example of attenuation coefficients when taking tissue density and CM concentrations into account (right side).…”

Section: Physical Principle Of CMmentioning

confidence: 99%

“…In Study I, four quasi-anthropomorphic abdominal phantoms (Tissue Equivalent CT Dose Phantoms, CIRS, Norfolk, VA) were used to simulate adult abdomens of sizes (AP×LAT cm) 18.5×24, 22×30, 25×32.5 and 31×38.9, corresponding to a body mass index (BMI) of approximately 7 16, 23, 26 and 35 kg/m 2 respectively ( Figure 6). These phantoms are made of proprietary epoxy that closely mimics the x-ray absorption and scatter properties in the diagnostic energy range.…”

Section: Phantomsmentioning

confidence: 99%

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Is sub-mSv CT for evaluation of non-specific findings in bone scintigraphy of oncological patients feasible?

et al. 2019

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Computed tomography (CT) was introduced to medicine in the early 1970s, which brought slice imaging into wide use for the first time. Today, CT is an essential part of radiological diagnostics, and is used for a wide range of clinical applications. One downside of CT imaging is the health risks related to the ionizing radiation. In the 80s it was believed that CT would soon be replaced completely by MRI due, in part, to the ionizing radiation required in CT. A further downside are the health risks related to the use of iodine-based contrast media. Both radiation-and contrast media dose have a trade-off with image quality. However, many technical advances have been made, and progress is still ongoing, to improve and broaden the applications of CT. Such advances necessitate a re-evaluation of imaging protocols and continued optimization of radiation dose, contrast media dose and imaging quality. This is the subject of this PhD project.Study I: The aim of this study was to evaluate the potential of low-kV dual-source (DS) and dual-energy (DE) to reduce CM-doses while maintaining soft-tissue and iodine CNR in phantoms of varying size, and to quantify the corresponding radiation dose increases. It was found that low-kV dual-source imaging could be used to reduce CM doses by 44-53% with maintained iodine-, soft tissue-and other materials CNR in a wide range of abdominal sizes, to the cost of about 20-100% increased radiation dose, depending on size. The dual-energy technique allowed a reduction of CM dose by 20% at similar radiation dose as the standard 120 kV protocol.Study II: The aim of this study was to implement and evaluate a scanning regimen, based on the results from Study I, to reduce CM-doses for patients believed to be at risk of CIN. It was concluded that the protocols from Study I could be used to reduce CM doses by 40-50%, depending on patient size, with maintained CNR in patients with a BMI-range of 15-36 kg/m 2 . The size-specific dose estimates increased by 70%.Study III: The aim of this study was to compare the outcome in image noise and radiation dose in the subsequent CT scan following a single anterior-posterior (AP) vs a combined lateral plus AP (LAT+AP) localizer when using automatic tube-current modulation (ATCM). The results suggested that using LAT+AP localizer yields more consistent noise and radiation dose than a single AP. The effect was small, except for a subgroup of females with laterally protruding breast tissue, which may have been overexposed by about 57% in the thorax region.Study IV: The aim of this study was to evaluate if standard-dose CT can be replaced with low-dose CT for characterization of non-specific findings bone in scintigraphy. Based on these results, sub-mSv CT seems feasible for morphological characterization of skeletal changes in areas with increased tracer uptake on bone scintigraphy, although a larger study is needed.

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Spectral CT quantification stability and accuracy for pediatric patients: A phantom study

Shapira

Mei

Noël

2021

J Applied Clin Med Phys

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Background: Spectral computed tomography (spectral CT) provides access to clinically relevant measures of endogenous and exogenous materials in patients. For pediatric patients, current spectral CT applications include lesion characterization, quantitative vascular imaging, assessments of tumor response to treatment, and more. Objective: The aim of this study is a comprehensive investigation of the accuracy and stability of spectral quantifications from a spectral detector-based CT system with respect to different patient sizes and radiation dose levels relevant for the pediatric population. Materials and methods: A spectral CT phantom with tissue-mimicking materials and iodine concentrations relevant for pediatric imaging was scanned on a spectral detector CT system using a standard pediatric abdominal protocol at 100%, 67%, 33% and 10% of the nominal radiation dose level. Different pediatric patient sizes were simulated using supplemental 3D-printed extension rings. Virtual mono-energetic, iodine density, effective atomic number, and electron density results were analyzed for stability with respect to radiation dose and patient size. Results: Compared to conventional CT imaging, a pronounced improvement in the stability of attenuation measurements across patient size was observed when using virtual mono-energetic images. Iodine densities were within 0.1 mg/ml, effective atomic numbers were within 0.26 atomic numbers and electron density quantifications were within AE1.0% of their respective nominal values. Relative to the nominal dose clinical protocol, differences in attenuation of all tissue-mimicking materials were maintained below 1.6 HU for a 33% dose reduction, below 2.7 HU for a 67% dose reduction and below 3.7 HU for a 90% dose reduction, for all virtual mono-energetic energies equal to or greater than 50 keV. Iodine, and effective atomic number quantifications were stable to within 0.1 mg/ml and 0.06 atomic numbers, respectively, across all measured dose levels. Conclusion: Spectral CT provides accurate and stable material quantification with respect to radiation dose reduction (up to 90%) and differing pediatric patient size. The observed consistency is an important step towards quantitative pediatric imaging at low radiation exposure levels.

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Accuracy of electron density, effective atomic number, and iodine concentration determination with a dual‐layer dual‐energy computed tomography system

Cited by 98 publications

References 29 publications

Technical Note: Relative proton stopping power estimation from virtual monoenergetic images reconstructed from dual‐layer computed tomography

Technical Note: Relative proton stopping power estimation from virtual monoenergetic images reconstructed from dual‐layer computed tomography

Is sub-mSv CT for evaluation of non-specific findings in bone scintigraphy of oncological patients feasible?

Spectral CT quantification stability and accuracy for pediatric patients: A phantom study

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