Technical note: Multi‐receiver combination method for phase‐based electrical property tomography of the breast

Abstract

Background: Phase-based electrical property tomography (EPT) is a technique that allows conductivity reconstruction with only phase of the B 1 field under the assumption that the magnitude of the B 1 fields are homogeneous. The more this assumption is violated, the less accurate the reconstructed conductivity. Thus, a method that ensures homogeneity of |B − 1 | field is important for breast image using multi-receiver coil. Purpose: To develop a method for multi-receiver combination for phase-based EPT usable for breast EPT imaging in the clinic. Methods: Theory of the proposed method is presented. To validate the proposed method, the phantom and in-vivo experiments were conducted. Conductivity images were reconstructed using the transceive phase of the combined image and results were compared with another combination method. Results: The proposed method's conductivity results were more stable than those of the previous method when |B + 1 | was not homogeneous and when the homogeneous contrast region was small. The phantom and in-vivo results indicate that the proposed method produces improved conductivity images than the previous method. The proposed combination method also increased the conductivity contrast between benign and cancerous tissues. Conclusion:The proposed method produced more stable multi-receiver combination for phase-based EPT of the breast in a clinical environment.

Data‐driven electrical conductivity brain imaging using 3 T MRI

“…Secondly, the proposed method was implemented based on the premise of the transceive phase assumption. Since the transceive phase assumption typically holds for birdcage coils, in this study, the transceive phase was approximated from the multi‐RX coil by using the multi‐RX combination method (Kim et al, 2022). Although the use of birdcage coils may facilitate access to transceive phase information, multi‐RX coils may be preferred in clinical settings for SNR or compatibility with parallel imaging techniques.…”

“…The scans were performed under the approval of the local institutional review board (Yonsei University Gangnam Severance Hospital, IRB, no: 3‐2022‐0443). For all in‐vivo datasets, the multi‐channel receive (multi‐RX) coil combination method (Kim et al, 2022) was performed as a coil combination method to approximate the transceive phase information from the clinical settings with the multi‐RX head coil. In addition, since there is no knowledge of the ground‐truth tissue conductivity values for in‐vivo brain, conductivity values reconstructed using the Poly‐Fit method (Lee et al, 2016) were used for comparison purposes.…”

Problem Solving MRI to Reduce False‐Positive Biopsy Related to Breast US: Conductivity vs. DWI vs. Abbreviated Contrast‐Enhanced MRI

“…6 However, we used a B À 1 -based coil combination technique that did not use a homogeneous segment and improved the quality of conductivity images compared with previous image-based coil combination techniques. 26 Nevertheless, further technical development is required to obtain stable conductivity images of dense breasts.…”

“…Phase‐based EPT allowed conductivity reconstruction with only the phase of the transceive field under the assumption that the magnitude of the transceive field would be homogeneous. Given that for breast MRI a multi‐receiver coil is typically used, we applied a ‐based coil combination technique to reduce the heterogeneity of the receive magnetic field (), estimated using ESPIRiT 26,27 . Next, a weighted polynomial fitting technique with a 25 × 25 two‐dimensional kernel was applied to reduce the noise and boundary errors 28 …”

“…Given that for breast MRI a multi-receiver coil is typically used, we applied a B À 1 -based coil combination technique to reduce the heterogeneity of the receive magnetic field (B À 1 ), estimated using ESPIRiT. 26,27 Next, a weighted polynomial fitting technique with a 25 Â 25 twodimensional kernel was applied to reduce the noise and boundary errors. 28 Abbreviations: CHESS = chemical shift selective; DWI = diffusion-weighted imaging; MIP = maximum intensity projection; MPR = multiplanar reconstruction; SPAIR = spectral attenuated inversion recovery; T2WI = T2 weighted imaging; TE = echo time; TR = repetition time.…”