Tijl A. van der Velden

Multiparametric MRI With Dynamic Contrast Enhancement, Diffusion-Weighted Imaging, and 31-Phosphorus Spectroscopy at 7 T for Characterization of Breast Cancer.

ObjectivesTo describe and to correlate tumor characteristics on multiparametric 7 tesla (T) breast magnetic resonance imaging (MRI) with prognostic characteristics from postoperative histopathology in patients with breast cancer. Materials and MethodsInstitutional review board approval and written informed consent of 15 women (46–70 years) with 17 malignant lesions were obtained. In this prospective study (March 2013 to March 2014), women were preoperatively scanned using dynamic contrast-enhanced MRI, diffusion-weighted imaging, and 31-phosphorus spectroscopy (31P-MRS). The value of the protocol was assessed to quantify tumor differentiation and proliferation. Dynamic contrast-enhanced MRI was assessed according to the American College of Radiology Breast Imaging Reporting and Data System-MRI lexicon. Apparent diffusion coefficients (ADCs) were calculated from diffusion-weighted imaging. On 31P-MRS, at the location of the tumor, the amount of phosphorus components was obtained in a localized spectrum. In this spectrum, the height of phosphodiester (PDE) and phosphomonoester (PME) peaks was assessed to serve as a measure for metabolic activity, stratifying tumors into a PDE > PME, PDE = PME, or PDE < PME group. Tumor grade and mitotic count from resection specimen were compared with the MRI characteristics using explorative analyses. ResultsOn dynamic contrast-enhanced MRI, the mean tumor size was 24 mm (range, 6–55 mm). An inverse trend was seen between ADC and tumor grade (P = 0.083), with mean ADC of 867 × 10−6 mm2/s for grade 1 (N = 4), 751 × 10−6 mm2/s for grade 2 (N = 6), and 659 × 10−6 mm2/s for grade 3 (N = 2) tumors. Between 31P-MR spectra and mitotic count, a relative increase of PME over PDE showed significant association with increasing mitotic counts (P = 0.02); a mean mitotic count of 6 was found in the PDE greater than PME group (N = 7), 8 in the PDE = PME group (N = 1), and 17 in the PDE < PME group (N = 3). ConclusionsMultiparametric 7 T breast MRI is feasible in clinical setting and shows association between ADC and tumor grade, and between 31P-MRS and mitotic count.

Radiofrequency configuration to facilitate bilateral breast 31P MR spectroscopic imaging and high-resolution MRI at 7 Tesla

High‐resolution MRI combined with phospholipid detection may improve breast cancer grading. Currently, configurations are optimized for either high‐resolution imaging or 31P spectroscopy. To be able to perform both imaging as well as spectroscopy in a single session, we integrated a 1H receiver array into a 1H‐31P transceiver at 7T. To ensure negligible signal loss due to coupling between elements, we investigated the use of a floating decoupling loop to enable bilateral MRI and 31P MRS.

MRI of the carotid artery at 7 Tesla: quantitative comparison with 3 Tesla.

To evaluate the 7 Tesla (T) MRI of the carotid arteries, as quantitatively compared with 3T.

Measuring motion-induced B0 -fluctuations in the brain using field probes.

Fluctuations of the background magnetic field (B0) due to body and breathing motion can lead to significant artifacts in brain imaging at ultrahigh field. Corrections based on real‐time sensing using external field probes show great potential. This study evaluates different aspects of field interpolation from these probes into the brain which is implicit in such methods. Measurements and simulations were performed to quantify how well B0‐fluctuations in the brain due to body and breathing motion are reflected in external field probe measurements.

A comparison of navigators, snap‐shot field monitoring, and probe‐based field model training for correcting B0‐induced artifacts in T2*‐weighted images at 7 T

To compare methods for estimating B0 maps used in retrospective correction of high‐resolution anatomical images at ultra‐high field strength. The B0 maps were obtained using three methods: (1) 1D navigators and coil sensitivities, (2) field probe (FP) data and a low‐order spherical harmonics model, and (3) FP data and a training‐based model.

Fat suppression techniques for obtaining high resolution dynamic contrast enhanced bilateral breast MR images at 7T.

OBJECTIVES To compare water selective excitation (WSE) and Dixon fat suppression in the context of high-resolution dynamic contrast enhanced MRI of the breast at 7T. METHODS Ten healthy volunteers and one patient with a malignant breast lesion were scanned at 7T. The MRI protocol contained 3D T1-weighted gradient echo images obtained with both WSE fat suppression, multi echo Dixon fat suppression, and without fat suppression. Images were acquired at a (0.8mm)(3) or (0.7mm)(3) isotropic resolution with equal field of view and optimized such to obtain a maximal SNR. Image quality was scored qualitatively on overall image quality, sharpness of anatomical details, presence of artifacts, inhomogeneous fat suppression and the presence of water-fat shift. A quantitative scoring was obtained from the signal to noise ratio and contrast to noise ratio. RESULTS WSE scored significantly better in terms of overall image quality and the absence of artifacts. No significant difference in contrast to noise ratio was found between the two fat suppression methods. CONCLUSION When maximizing temporal and spatial resolution of high resolution DCE MRI of the breast, water selective excitation provides better image quality than multi echo Dixon at 7T.

Shortening of apparent transverse relaxation time of inorganic phosphate as a breast cancer biomarker

Phosphorus MRS offers a non‐invasive tool for monitoring cell energy and phospholipid metabolism and can be of additional value in diagnosing cancer and monitoring cancer therapy. In this study, we determined the transverse relaxation times of a number of phosphorous metabolites in a group of breast cancer patients by adiabatic multi‐echo spectroscopic imaging at 7 T. The transverse relaxation times of phosphoethanolamine, phosphocholine, inorganic phosphate (Pi), glycerophosphocholine and glycerophosphatidylcholine were 184 ± 8 ms, 203 ± 17 ms, 87 ± 8 ms, 240 ± 56 ms and 20 ± 10 ms, respectively. The transverse relaxation time of Pi in breast cancer tissue was less than half that of healthy fibroglandular tissue. This effect is most likely caused by an up‐regulation of glycolysis in breast cancer tissue that leads to interaction of Pi with the GAPDH enzyme, which forms part of the reversible pathway of exchange of Pi with gamma‐adenosine tri‐phosphate, thus shortening its apparent transverse relaxation time. As healthy breast tissue shows very little glycolytic activity, the apparent T2 shortening of Pi due to malignant transformation could possibly be used as a biomarker for cancer.

Improved fat suppression of the breast using discretized frequency shimming

Robust fat suppression is essential in bilateral breast MRI at 7 Tesla. The lack of good fat suppression can result in errors when calculating the enhancement curve from dynamic contrast‐enhanced acquisitions. In this work we propose discretized frequency shimming to improve the quality of fat suppression by exploiting the capabilities of a parallel transmit setup.

Feasibility of 7-T fluorine magnetic resonance spectroscopic imaging ( 19 F MRSI) for TAS-102 metabolite detection in the liver of patients with metastatic colorectal cancer

Trifluridine/tipiracil (TAS-102) has shown a significant overall survival benefit in patients with heavily pre-treated metastatic colorectal cancer. However, predicting treatment response and toxicity in individual patients remains challenging. Fluorine (19F)-containing drugs can be detected with magnetic resonance spectroscopy (MRS) to determine the metabolic rates and the biodistribution of the drug in normal and tumour tissue, which are related to treatment efficacy and toxicity. This is the first study to investigate the potential of 7-T 19F-MRS to detect TAS-102 metabolites in humans. We demonstrate that, with the used setup, TAS-102 is not detectable in liver metastases of metastatic colorectal cancer patients on a normal treatment schedule. Therefore, 19F-MRS TAS-102 metabolite detection is not yet useful for the clinical early prediction of treatment response. As 19F-MRS is able to detect TAS-102 in phantom and murine models, the use of 19F-MRS remains a potential tool to noninvasively detect and possibly monitor the metabolism when higher dosages of TAS-102 are administered, for example in organoid and animal studies.

Erratum to: Dynamic contrast-enhanced breast MRI at 7T and 3T: an intra-individual comparison study

[This corrects the article DOI: 10.1186/s40064-015-1654-7.].