A 16-Channel Receive, Forced Current Excitation Dual-Transmit Coil for Breast Imaging at 7T

To enable high spatial and temporal breast imaging resolution via combined use of high field MRI, array coils, and forced current excitation (FCE) multi channel transmit.A unilateral 16-channel receive array insert was designed for use in a transmit volume coil optimized for quadrature operation with dual-transmit RF shimming at 7 T. Signal-to-noise ratio (SNR) maps, g-factor maps, and high spatial and temporal resolution in vivo images were acquired to demonstrate the utility of the coil architecture.The dual-transmit FCE coil provided homogeneous excitation and the array provided an increase in average SNR of 3.3 times (max 10.8, min 1.5) compared to the volume coil in transmit/receive mode. High resolution accelerated in vivo breast imaging demonstrated the ability to achieve isotropic spatial resolution of 0.5 mm within clinically relevant 90 s scan times, as well as the ability to perform 1.0 mm isotropic resolution imaging, 7 s per dynamics, with the use of bidirectional SENSE acceleration of up to R = 9.The FCE design of the transmit coil easily accommodates the addition of a sixteen channel array coil. The improved spatial and temporal resolution provided by the high-field array coil with FCE dual-channel transmit will ultimately be beneficial in lesion detection and characterization

Predicting breast cancer response to neoadjuvant treatment using multi-feature MRI: results from the I-SPY 2 TRIAL.

Dynamic contrast-enhanced (DCE) MRI provides both morphological and functional information regarding breast tumor response to neoadjuvant chemotherapy (NAC). The purpose of this retrospective study is to test if prediction models combining multiple MRI features outperform models with single features. Four features were quantitatively calculated in each MRI exam: functional tumor volume, longest diameter, sphericity, and contralateral background parenchymal enhancement. Logistic regression analysis was used to study the relationship between MRI variables and pathologic complete response (pCR). Predictive performance was estimated using the area under the receiver operating characteristic curve (AUC). The full cohort was stratified by hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status (positive or negative). A total of 384 patients (median age: 49 y/o) were included. Results showed analysis with combined features achieved higher AUCs than analysis with any feature alone. AUCs estimated for the combined versus highest AUCs among single features were 0.81 (95% confidence interval [CI]: 0.76, 0.86) versus 0.79 (95% CI: 0.73, 0.85) in the full cohort, 0.83 (95% CI: 0.77, 0.92) versus 0.73 (95% CI: 0.61, 0.84) in HR-positive/HER2-negative, 0.88 (95% CI: 0.79, 0.97) versus 0.78 (95% CI: 0.63, 0.89) in HR-positive/HER2-positive, 0.83 (95% CI not available) versus 0.75 (95% CI: 0.46, 0.81) in HR-negative/HER2-positive, and 0.82 (95% CI: 0.74, 0.91) versus 0.75 (95% CI: 0.64, 0.83) in triple negatives. Multi-feature MRI analysis improved pCR prediction over analysis of any individual feature that we examined. Additionally, the improvements in prediction were more notable when analysis was conducted according to cancer subtype

Bleeding Complications After Breast Core-needle Biopsy—An Approach to Managing Patients on Antithrombotic Therapy

Abstract Image-guided core-needle breast and axillary biopsy (CNB) is the standard-of-care procedure for the diagnosis of breast cancer. Although the risks of CNB are low, the most common complications include bleeding and hematoma formation. Post-procedural bleeding is of particular concern in patients taking antithrombotic therapy, but there is currently no widely established standard protocol in the United States to guide antithrombotic therapy management. In the face of an increasing number of patients taking antithrombotic therapy and with the advent of novel classes of anticoagulants, the American College of Radiology guidelines recommend that radiologists consider cessation of antithrombotic therapy prior to CNB on a case-by-case basis. Lack of consensus results in disparate approaches to patients on antithrombotic therapy undergoing CNB. There is further heterogeneity in recommendations for cessation of antithrombotic therapy based on the modality used for image-guided biopsy, target location, number of simultaneous biopsies, and type of antithrombotic agent. A review of the available data demonstrates the safety of continuing antithrombotic therapy during CNB while highlighting additional procedural and target lesion factors that may increase the risk of bleeding. Risk stratification of patients undergoing breast interventional procedures is proposed to guide both pre-procedural decision-making and post-procedural management. Radiologists should be aware of antithrombotic agent pharmacokinetics and strategies to minimize post-procedural bleeding to safely manage patients

In vivo SNR profiles.

<p>Images of the right breast sagittal slice from a volunteer obtained with A) the FCE coil in T/R mode, B) the transmit FCE coil with the 16-channel receive array insert (different windowing was used compared to (A) due to the very high SNR values close to the array elements) and C) a comparison of the respective profiles. The <i>in vivo</i> results demonstrate comparable SNR gains to the phantom data; there is approximately a 3.5× improvement in mean SNR throughout the breast.</p

Noise correlation matrix of the 16 channel receive elements.

<p>Noise correlation matrix from the 16-channel receive array acquired with the uniform phantom. The mean correlated value is 6.6%, with a minimum of 3.6% and a maximum of 17.7%.</p

Photographs of the coil.

<p>A) the 16-channel receive array with external boards connected as viewed from the bottom of the hemisphere, B) the dual-transmit FCE volume coil showing one of the common voltage points and C) the final configuration with the receive array inside the transmit coil and patient support structure.</p

Overview of transmit and receive coil setup.

<p>A) Rendering of transmit coil (in orange, i.d. = 153 mm, depth = 110 mm) with 16-channel receive array insert (in blue), and B) Schematic overview of FCE detuning circuitry utilizing λ/4 transmission lines to open-circuit each transmit coil element when diodes at the common voltage point (CVP) are biased.</p

16-channel unilateral breast receive array.

<p>A) Layout of overlapped receive elements (as observed from the bottom of the hemisphere), highlighting each element's position and size (70 mm loops in blue, 59 mm loops in gray). There are 3 rows of coils in the anterior-posterior direction, each row having 1, 6, or 9 coils, respectively. B) Circuit schematic of a single receive element including preamplifier chain. Each element is segmented by six breaks, with a passive and active detuning trap around the tune and match capacitors, respectively. C) Detachable board including the active detuning trap, balun, and cable connection to 16-channel interface box.</p

Comparison of SNR maps in a phantom between the 16-channel receive array and volume coil.

<p>Improvements in SNR when using close-fitting 16-channel array. SNR maps acquired with A) the FCE volume coil alone and B) the 16-channel receive array. The sagittal view through the middle of a hemispherical homogenous canola oil phantom is shown (a.u. SNR). C) SNR ratio between the 16-channel receive array and the volume coil demonstrates a mean SNR improvement of a factor of 3.3 over the entire area of the phantom, with a mean SNR gain of 2.1× in the middle of the phantom marked by the black ROI in (A). The periphery of the phantom experiences a local high (up to 10-fold) increase in SNR.</p