Electronically rotated and translated field‐free line generation for open bore magnetic particle imaging

Top, Can Barış; İlbey, Serhat; Güven, H. Emre

doi:10.1002/mp.12604

Cited by 20 publications

(17 citation statements)

References 37 publications

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“…Here we analyzed the FFL trajectory in a 2D scheme. With the presented hardware, imaging plane can be shifted in the z‐direction by feeding the upper and lower coils asymmetrically . Therefore, slice by slice reconstruction is possible for all trajectories.…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, SF‐y coils generate an FFL in the y‐direction. The details of the coil configuration can be found in Top et al . The currents of these coils are adjusted so that both coil groups create a magnetic field with 1 T/m gradient inside the FOV independently.…”

Section: Methodsmentioning

confidence: 99%

“…

f_{italicSF}

and

f_{italicFF}

are the frequencies of the SF and FF currents, respectively. In the present configuration, the SF coil currents are increased with

r

to compensate for the loss in the gradient . Peak SF coil currents

I_{x} false(r false)

and

I_{y} false(r false)

were calculated as a function of FFL translation distance to obtain 1 T/m gradient in the circular FOV within 160 mm diameter.…”

Section: Methodsmentioning

confidence: 99%

“…In this study, to fill this gap and provide information on the FFL trajectory that achieves the best image quality in minimum scan time considering safety and hardware limitations, we compared Radial, Spiral, Uniform Spiral, and Lissajous trajectories for a large FOV scanning FFL. We used a 2D dot phantom for the simulations to compare the image quality performance of these trajectories with an open FFL coil configuration . We reconstructed the images with two SM reconstruction approaches: (a) Alternating direction method of multipliers (ADMMs) based algorithm to solve l 1 ‐norm and TV minimization, and (b) algebraic reconstruction technique (ART) for a more conventional l 2 ‐norm based regularization.…”

Section: Introductionmentioning

confidence: 99%

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Trajectory analysis for field free line magnetic particle imaging

et al. 2019

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Purpose Magnetic particle imaging (MPI) is a relatively new method to image the spatial distribution of magnetic nanoparticle (MNP) tracers administered to the body with high spatial and temporal resolution using an inhomogeneous magnetic field. The spatial information of the MNP's is encoded using a field free point (FFP), or a field free line (FFL), in which the magnetic field vanishes at a point, or on a line, respectively. FFL scanning has the advantage of improved sensitivity compared to FFP scanning as a result of higher signal‐to‐noise ratio. The trajectory traversed by the FFL or FFP is an important parameter of the MPI system and should be selected to achieve the best imaging quality in minimum scan time, while considering hardware constraints and patient safety. In this study, we analyzed the image quality of different FFL trajectories for a large field of view (FOV) using simulations, to provide a baseline information for FFL scanning MPI system design. Methods We simulated a human‐sized FFL scanning MPI configuration to image a circular FOV with 160 mm diameter, and compared Radial, Spiral, Uniform Spiral, Flower, and Lissajous trajectories with different trajectory densities scanned by the FFL for constant scan time. We analyzed the system matrices of the trajectories in terms of mutual coherence and homogeneity of the spatial sensitivity. We calculated the maximum electric fields induced on a homogeneous conductive body by the selection field (SF) and the focus field (FF) to compare the trajectories based on the nerve stimulation threshold. The images were obtained using the system matrix reconstruction approach with two different image reconstruction methods. In the first one, we used the conventional image reconstruction method, algebraic reconstruction technique (ART), which gives a regularized least‐squares solution. In the second one, we used the state‐of‐the‐art alternating direction method of multipliers (ADMM), which minimizes a weighted sum of the l1‐norm and the total variation (TV) of the images. Results The Radial and Spiral trajectories resulted in a poor imaging performance at low trajectory densities due to relatively high coherency and poor sensitivity of the measurements, respectively. For ART reconstruction, the highest image quality with the lowest trajectory density was achieved with the Uniform Spiral trajectory. Uniform Spiral, Flower, and Lissajous trajectories yielded comparable performance with ADMM reconstruction. The rotating SF induced higher electric field amplitude compared to the FF. Consequently, maximum allowable gradient at the same trajectory density was greater for the Radial trajectory compared to the other trajectories. Conclusions For a large FOV coverage, the Uniform Spiral trajectory offers a good compromise between image quality and imaging time, taking safety and hardware limitations into account. The Radial trajectory, especially using l1‐norm and TV priors in the reconstruction, may be favorable in case the SF induced electric field is higher than that of...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

“…

f_{italicSF}

and

f_{italicFF}

are the frequencies of the SF and FF currents, respectively. In the present configuration, the SF coil currents are increased with

r

to compensate for the loss in the gradient . Peak SF coil currents

I_{x} false(r false)

and

I_{y} false(r false)

were calculated as a function of FFL translation distance to obtain 1 T/m gradient in the circular FOV within 160 mm diameter.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Trajectory analysis for field free line magnetic particle imaging

et al. 2019

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“…In principle, MPI scanners can be designed as open bore or even floating table systems 5 allowing proper access to the investigated object -in the distant future possibly a patient. One promising concept proposed a setup for an open bore FFL MPI scanner without the need for mechanical rotation, where a comparable large field of view (FOV) can be scanned in a sufficient time span, which is needed for clinical usage 6 .…”

mentioning

confidence: 99%

Visualization of spatial and temporal temperature distributions with magnetic particle imaging for liver tumor ablation therapy

Salamon

Dieckhoff

Kaul

et al. 2020

Sci Rep

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temperature-resolved magnetic particle imaging (Mpi) represents a promising tool for medical imaging applications. in this study an approach based on a single calibration measurement was applied for highlighting the potential of Mpi for monitoring of temperatures during thermal ablation of liver tumors. For this purpose, liver tissue and liver tumor phantoms embedding different superparamagnetic iron oxide nanoparticles (SPION) were prepared, locally heated up to 70 °C and recorded with Mpi. optimal temperature Mpi Spions and a corresponding linear model for temperature calculation were determined. the temporal and spatial temperature distributions were compared with infrared (IR) camera results yielding quantitative agreements with a mean absolute deviation of 1 °C despite mismatches in boundary areas.

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