Energy subtraction angiography is comparable to digital subtraction angiography in terms of iodine Rose SNR

Burton, Christiane Sarah; Mayo, John R.; Cunningham, Ian

doi:10.1118/1.4962651

Cited by 10 publications

(23 citation statements)

References 53 publications

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“…. Similarly, the

E (t, b)

terms were calculated for LE and HE hardened beams using values from previous studies and matching to the spectrum effective energies . Both

α (t, b)

and

E (t, b)

were inserted into Eq.…”

Section: Methodsmentioning

confidence: 99%

“…Similarly, the Eðt; bÞ terms were calculated for LE and HE hardened beams using values from previous studies and matching to the spectrum effective energies. 34,45 Both aðt; bÞ and Eðt; bÞ were inserted into Eq. (A18) to calculate theoretical weighting factor for each bone and soft-tissue thickness pairs in the range [0-6 cm] and [0-30 cm], respectively.…”

Section: B Simulation and Validation Of Parameters Affecting Weighmentioning

confidence: 99%

“…In the case where b 0 = 0, that is, when bone is replaced with air, the x is reduced to This is the weighting factor expression commonly referred in the literature. 34,36 In the case where b 0 ¼ b; that is, when bone is replaced with soft-tissue with the same thickness, the x is…”

Section: A1 Monoenergetic Casementioning

confidence: 99%

“…The weighting factor in the subtraction method plays a critical role in determining the success of DE imaging in terms of both tissue cancelation and noise propagation. Some previous studies used

ω = μ_{H}^{b} / μ_{L}^{b}

to create soft‐tissue‐only image, where

μ_{H}^{b}

and

μ_{L}^{b}

are bone linear attenuation coefficients for HE and LE, respectively . However, this equation is only valid for monoenergetic beams and does not include polyenergetic beam hardening effects, and thus, effective

μ

values may be used as an approximation.…”

Section: Introductionmentioning

confidence: 99%

“…H and l b L are bone linear attenuation coefficients for HE and LE, respectively. 29,31,34,35 However, this equation is only valid for monoenergetic beams and does not include polyenergetic beam hardening effects, and thus, effective l values may be used as an approximation. Some other studies empirically determined the weighting factors which may only apply to a particular patient thickness for given LE and HE beams.…”

Section: Introductionmentioning

confidence: 99%

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Patient‐specific pixel‐based weighting factor dual‐energy x‐ray imaging system using a priori CT data

2019

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Purpose The purpose of this study was to develop a novel patient‐specific pixel‐based weighting factor dual‐energy (PP‐DE) algorithm to effectively suppress bone throughout the image and overcome the limitation of the conventional DE algorithm with constant weighting factor which is restricted to regions with uniform patient thickness. Additionally, to derive theoretical expressions to describe the dependence of the weighting factors on several imaging parameters and validate them with measurement. Methods A step phantom was constructed consisting of slabs of solid water and bone materials. Thicknesses of bone ranged [0–6] cm in one direction and solid water [5–30] cm in the other direction. Projection images at 60 and 140 kVp were acquired using a clinical imaging system. Optimal weighting factors were found by iteratively varying it in the range [0–1.4], where bone and soft‐tissue contrast‐to‐noise ratio (CNR) reached zero. Bone and soft‐tissue digitally reconstructed thicknesses were created using computed tomography (CT) images of a Rando phantom and ray tracing techniques. A weighting factor image (ω) was calculated using digitally reconstructed thicknesses (DRTs) and precalculated weighting factors from the step phantom. This ω image was then used to generate a PP‐DE image. The PP‐DE image was compared to the conventional DE image which uses a constant weighting factor throughout the image. The effect of the misaligned ω image on PP‐DE images was investigated by acquiring LE and HE images at various shifts of Rando phantom. A rigid registration was used based on mutual information algorithm in Matlab. The signal‐to‐noise ratios (SNR) were calculated in the step phantom for the PP‐DE image and compared to that of conventional DE technique. Analytical expressions for theoretical weighting factors were derived which included various effects such as beam hardening, scatter, and detector response. The analytical expressions were simulated in Spektr3.0 for different bone and solid water thicknesses as per the step phantom. A tray of steel pins was constructed and used with the step phantom to remove the scattered radiation. The simulated theoretical weighting factors were validated by comparing to those from the step phantom measurement. Results Optimal weighting factor values for the step phantom varied from 0.633 to 1.372 depending on region thickness. Thicker regions required larger weighting factors for bone cancellation. The PP‐DE image of the Rando phantom favorably cancelled both ribs and spine, whereas in the conventional DE image, only one could be cancelled at a time. The misaligned ω image was less effective in removing all bones indicating the importance of alignment as part of the PP‐DE algorithm implementation. The SNRs for the PP‐DE image was larger than those of the conventional DE images for regions which required smaller weighting factors for bone suppression. Comparisons of measured and simulated weighting factors demonstrated a 3% agreement for all bone overlapped regions except for the thicke...

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“…. Similarly, the

E (t, b)

terms were calculated for LE and HE hardened beams using values from previous studies and matching to the spectrum effective energies . Both

α (t, b)

and

E (t, b)

were inserted into Eq.…”

Section: Methodsmentioning

confidence: 99%

Section: B Simulation and Validation Of Parameters Affecting Weighmentioning

confidence: 99%

Section: A1 Monoenergetic Casementioning

confidence: 99%

ω = μ_{H}^{b} / μ_{L}^{b}

to create soft‐tissue‐only image, where

μ_{H}^{b}

and

μ_{L}^{b}

μ

values may be used as an approximation.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Patient‐specific pixel‐based weighting factor dual‐energy x‐ray imaging system using a priori CT data

2019

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Assessment of quantification accuracy and image quality of a full‐body dual‐layer spectral CT system

Ehn

Sellerer

Muenzel

et al. 2017

J Applied Clin Med Phys

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The performance of a recently introduced spectral computed tomography system based on a dual‐layer detector has been investigated. A semi‐anthropomorphic abdomen phantom for CT performance evaluation was imaged on the dual‐layer spectral CT at different radiation exposure levels (CTDI vol of 10 mGy, 20 mGy and 30 mGy). The phantom was equipped with specific low‐contrast and tissue‐equivalent inserts including water‐, adipose‐, muscle‐, liver‐, bone‐like materials and a variation in iodine concentrations. Additionally, the phantom size was varied using different extension rings to simulate different patient sizes. Contrast‐to‐noise (CNR) ratio over the range of available virtual mono‐energetic images (VMI) and the quantitative accuracy of VMI Hounsfield Units (HU), effective‐Z maps and iodine concentrations have been evaluated. Central and peripheral locations in the field‐of‐view have been examined. For all evaluated imaging tasks the results are within the calculated theoretical range of the tissue‐equivalent inserts. Especially at low energies, the CNR in VMIs could be boosted by up to 330% with respect to conventional images using iDose/spectral reconstructions at level 0. The mean bias found in effective‐Z maps and iodine concentrations averaged over all exposure levels and phantom sizes was 1.9% (eff. Z) and 3.4% (iodine). Only small variations were observed with increasing phantom size (+3%) while the bias was nearly independent of the exposure level (±0.2%). Therefore, dual‐layer detector based CT offers high quantitative accuracy of spectral images over the complete field‐of‐view without any compromise in radiation dose or diagnostic image quality.

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Theoretical feasibility of dual‐energy radiography for structural and functional imaging of chronic obstructive pulmonary disease

et al. 2020

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Purpose Chronic obstructive pulmonary disease (COPD) affects ∼200 million people worldwide. We propose two‐dimensional (2D) dual‐energy (DE) x‐ray imaging of lung structure and function for the assessment of COPD, and investigate the resulting image quality theoretically. Methods We investigated xenon‐enhanced DE (XeDE) radiography for functional imaging of COPD and unenhanced DE radiography for structural imaging of COPD. We modeled the ability of human observers to detect ventilation defects in XeDE images and emphysema in (unenhanced) DE images using the detectability index (d′) as a figure of merit. We accounted for the extent of emphysematous destruction and functional impairment as a function of disease severity, defect/lesion contrast, spatial resolution, x‐ray scatter, quantum noise, anatomic noise, and the efficiency of human observers. Whether or not disease was detectable was determined based on a detectability threshold of two. For (unenhanced) DE imaging of emphysema, we compared detectability with that of single‐energy (SE) imaging. Models of signal and noise were compared to published data. Results Models of signal and noise agreed well with published data, and model predictions of the detectability of emphysema by SE radiography were consistent with poor sensitivity (i.e., d′<1) to mild to moderate COPD but moderate sensitivity (i.e., d′>1.5) to severe COPD. The detectability of emphysema by DE radiography was greater than that of SE radiography, but did not cross the threshold of detectability for mild to moderate COPD. The detectability index for XeDE imaging exceeded the detectability threshold for mild, moderate, and severe COPD. Conclusions Dual‐energy radiography may offer modest improvements in the detection of emphysema relative to SE imaging, but will unlikely enable detecting mild and moderate COPD. However, XeDE radiography may enable detection of functional abnormalities associated with mild, moderate and severe COPD at x‐ray exposures typical of those used in conventional chest radiography, thus warranting further investigation as a low‐dose, low‐cost alternative to CT‐ and MRI‐based approaches for functional imaging of COPD.

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Energy subtraction angiography is comparable to digital subtraction angiography in terms of iodine Rose SNR

Cited by 10 publications

References 53 publications

Patient‐specific pixel‐based weighting factor dual‐energy x‐ray imaging system using a priori CT data

Patient‐specific pixel‐based weighting factor dual‐energy x‐ray imaging system using a priori CT data

Assessment of quantification accuracy and image quality of a full‐body dual‐layer spectral CT system

Theoretical feasibility of dual‐energy radiography for structural and functional imaging of chronic obstructive pulmonary disease

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