Amide proton transfer imaging of the human breast at 7T: development and reproducibility

Abstract

Chemical exchange saturation transfer (CEST) can offer information about protons associated with mobile proteins through the amide proton transfer (APT) effect, which has been shown to discriminate tumor from healthy tissue and, more recently, has been suggested as a prognosticator of response to therapy. Despite this promise, APT effects are small (only a few percent of the total signal); and APT imaging is often prone to artifacts resulting from system instability. Here we present a procedure that enables the detection of APT effects in the human breast at 7 T while mitigating these issues. Adequate signal-to-noise ratio (SNR) was achieved via an optimized quadrature RF breast coil and 3D acquisitions. To reduce the influence of fat, effective fat suppression schemes were developed that did not degrade SNR. To reduce the levels of ghosting artifacts, dummy scans have been integrated into the scanning protocol. Compared to results obtained at 3 T, the standard deviation of the measured APT effect was reduced by a factor of four at 7 T, allowing for the detection of APT effects with a standard deviation of 1% in the human breast at 7 T. Together, these results demonstrate that the APT effect can be reliably detected in the healthy human breast with a high level of precision at 7 T.

Simulation, phantom validation, and clinical evaluation of fast pH‐weighted molecular imaging using amine chemical exchange saturation transfer echo planar imaging (CEST‐EPI) in glioma at 3 T

“…The maximum pulse length achievable on our MR system was approximately 100 ms, similar to those in other studies . However, it remains unclear whether pulse trains consisting of higher numbers of short pulses, such as those suggested in recent studies, are preferable to a lower number of pulses with longer saturation duration. To determine the dependence of MTR asym at 3.0 ppm on pH for different saturation pulse durations for NAWM, glioma, and CSF, RF saturation pulses with a total saturation of approximately 300 ms per repetition were examined under four scenarios: (A) 12 × 25 ms pulses; (B) 6 × 50 ms pulses; (C) 3 × 100 ms pulses; (D) 1 × 300 ms pulse.…”

Multiparametric MR Imaging of Breast Cancer

“…These include 23 Na sodium MRI and blood oxygen level-dependent (BOLD) MRI, described briefly below, as well as other techniques such as MR elastography (89), chemical exchange saturation transfer (CEST) (90, 91), and high spectral spatial resolution (HiSS) imaging (92) that are beyond the scope of this article.…”

Applying protein-based amide proton transfer MR imaging to distinguish solitary brain metastases from glioblastoma

“…The APTw signals are mainly related to cell density and endogenous mobile proteins and peptides [15–18]. APTw imaging has emerged as a valuable tool for grading brain tumors[18–20] and other cancers that occur in the prostate [21], breast [22; 23] and neck [24; 25]; for distinguishing tumor recurrence from radiation necrosis [26], distinguishing pseudo-progression from true progression in gliomas [27], and differentiating between primary central nervous system lymphomas and glioma [15]; and for characterizing cerebral ischemia [28–30]and Parkinson’s disease [31]. However, this technique has not been used to compare SBMs and GBMs.…”