MRI-based electric properties tomography with a quasi-Newton approach

Rahimov, Anar; Litman, Amélie; Ferrand, Guillaume

doi:10.1088/1361-6420/aa7ef2

Cited by 15 publications

(23 citation statements)

References 39 publications

(78 reference statements)

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“…Moreover, improved permittivity results have very recently been reported by using newly formulated EPT reconstruction methods on

B_{1}^{+}

maps from EM simulations. For example, using a quasi‐Newton approach, Rahimov et al have shown a permittivity precision of ~20% in the brain . In Guo et al, the std in permittivity, converted from the reported interquartile ranges according to the procedure in Wan et al, was ~8 rel.…”

Section: Discussionmentioning

confidence: 99%

“…To date, several techniques for

B_{1}^{+}

field mapping have been used in EPT studies (e.g., standard spin echo, gradient echo, and balanced steady‐state free precession for phase mapping and actual flip angle imaging (AFI) and double‐angle methods for

false| B_{1}^{+} false|

mapping) and numerous algorithms have been proposed to disentangle both properties from the

B_{1}^{+}

field . Based on measured field maps, in vivo conductivity maps have been derived (e.g., see previous works) and also preliminarily tested for clinical oncologic applications, for example, in brain, breast, and uterine cervix .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Accuracy and precision of electrical permittivity mapping at 3T: the impact of three mapping techniques

Gavazzi

Berg

Sbrizzi

et al. 2019

Magnetic Resonance in Med

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Purpose To investigate the sequence‐specific impact of amplitude mapping on the accuracy and precision of permittivity reconstruction at 3T in the pelvic region. Methods maps obtained with actual flip angle imaging (AFI), Bloch–Siegert (BS), and dual refocusing echo acquisition mode (DREAM) sequences, set to a clinically feasible scan time of 5 minutes, were compared in terms of accuracy and precision with electromagnetic and Bloch simulations and MR measurements. Permittivity maps were reconstructed based on these maps with Helmholtz‐based electrical properties tomography. Accuracy and precision in permittivity were assessed. A 2‐compartment phantom with properties and size similar to the human pelvis was used for both simulations and measurements. Measurements were also performed on a female volunteer’s pelvis. Results Accuracy was evaluated with noiseless simulations on the phantom. The maximum bias relative to the true distribution was 1% for AFI and BS and 6% to 15% for DREAM. This caused an average permittivity bias relative to the true permittivity of 7% to 20% for AFI and BS and 12% to 35% for DREAM. Precision was assessed in MR experiments. The lowest standard deviation in permittivity, found in the phantom for BS, measured 22.4 relative units and corresponded to a standard deviation in of 0.2% of the average value. As regards precision, in vivo and phantom measurements were comparable. Conclusions Our simulation framework quantitatively predicts the different impact of mapping techniques on permittivity reconstruction and shows high sensitivity of permittivity reconstructions to sequence‐specific bias and noise perturbation in the map. These findings are supported by the experimental results.

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“…Moreover, improved permittivity results have very recently been reported by using newly formulated EPT reconstruction methods on

B_{1}^{+}

Section: Discussionmentioning

confidence: 99%

“…To date, several techniques for

B_{1}^{+}

false| B_{1}^{+} false|

mapping) and numerous algorithms have been proposed to disentangle both properties from the

B_{1}^{+}

Section: Introductionmentioning

confidence: 99%

Accuracy and precision of electrical permittivity mapping at 3T: the impact of three mapping techniques

Gavazzi

Berg

Sbrizzi

et al. 2019

Magnetic Resonance in Med

View full text Add to dashboard Cite

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“…To further improve the effectiveness of the procedure, additional information (other than spatial priors, such as for example physical feasibility of the achieved EP values [26]) can be exploited. Enforcing these latter can be eventually achieved by modifying the functional to be minimized by adding suitable penalty terms.…”

Section: New Estimation Of Eps Via Mri/ct Based Projectionmentioning

confidence: 99%

“…In fact, up to now they have been proved to be effective only for over-simplified scenarios consisting of at most three biological tissues. Another example of regularization based on MRI/CT spatial priors is introduced in [26]. However, in this latter the EPs tomography is performed by processing the signal from MRI scanner by means a Newton-Kantorovich inversion scheme, which requires both the solution of several forward problems as well as the solution of several linearized inverse problems.…”

Section: Introductionmentioning

confidence: 99%

A Method for Effective Permittivity and Conductivity Mapping of Biological Scenarios via Segmented Contrast Source Inversion

Bevacqua¹,

Bellizzi²,

Isernia³

et al. 2019

PIER

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Quantitative estimation of both conductivity and permittivity of biological tissues is essential in many biomedical applications, ranging from therapeutic treatments to safety assessment of medical devices and dosimetry. Typically, the electromagnetic field distribution inside the body is predicted based on available ex-vivo measured electrical properties. Unfortunately, these values may be quite different from the ones measured in-vivo and cannot account for the differences among individuals. As a result, their use can introduce significant errors affecting therapeutic treatments and dose estimation. To cope with this problem, in this paper a new approach for estimation of effective electrical properties of human tissues is introduced. The proposed strategy is based on the solution of an inverse scattering problem (by means of a contrast source inversion scheme) and the use of an effective representation of the unknowns based on spatial priors derived by magnetic resonance imaging or computed tomography. The approach is tested in controlled conditions against simulated single frequency data and realistic and anthropomorphic head and neck phantoms. Moreover, the inherent advantages have been assessed in the framework of hyperthermia treatment planning.

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“…Inverse ept approaches are generally based on global integral forms of Maxwell's equations and obtain the eps by iteratively minimizing a cost function measuring the discrepancy between the "measured" B + 1 and modelled B + 1 [109][110][111][112][113][114][115][116][117][118]. Many contributions have solved this inverse problem with the contrast source inversion (csi) method [109,[114][115][116][117][118] and are reviewed in [119].…”

Section: Inverse Eptmentioning

confidence: 99%

Technical developments for MR-based electrical property mapping

Gavazzi¹

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Purpose: To demonstrate the feasibility of transceive phase mapping with the planet method and its application for conductivity reconstruction in the brain. Methods: Accuracy and precision of transceive phase (φ ±) estimation with planet, an ellipse fitting approach to phase-cycled balanced steady state free precession (bssfp) data, were assessed with simulations and measurements and compared to standard bssfp. Measurements were conducted on a homogeneous phantom and in the brain of healthy volunteers at 3T. Conductivity maps were reconstructed with Helmholtz-based electrical properties tomography (ept). In measurements, planet was also compared to a reference technique for transceive phase mapping, i.e. spin echo (se). Results: Accuracy and precision of φ ± estimated with planet depended on the chosen flip angle (FA) and TR. planet-based φ ± was less sensitive to perturbations induced by off-resonance effects and partial volume (e.g. white matter + myelin) than bssfp-based φ ±. For FA = 25 • and TR = 4.6 ms, planet showed an accuracy comparable to that of reference se but a higher precision than bssfp and se (factor of 2 and 3, respectively). The acquisition time for planet was 5 min; 2 min faster than se and 8 times slower than bssfp. However, planet simultaneously reconstructed T 1 , T 2 , B 0 maps besides mapping φ ±. In the phantom, planet-based conductivity matched the true value and had the smallest spread of the three methods. In vivo, planet-based conductivity was similar to se-based conductivity. Conclusion: Provided that appropriate sequence parameters are used, planet delivers accurate and precise φ ± maps, which can be used to reconstruct brain tissue conductivity while simultaneously recovering T 1 , T 2 and B 0 maps.

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MRI-based electric properties tomography with a quasi-Newton approach

Cited by 15 publications

References 39 publications

Accuracy and precision of electrical permittivity mapping at 3T: the impact of three mapping techniques

Accuracy and precision of electrical permittivity mapping at 3T: the impact of three mapping techniques

A Method for Effective Permittivity and Conductivity Mapping of Biological Scenarios via Segmented Contrast Source Inversion

Technical developments for MR-based electrical property mapping

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