³¹P MRSI and ¹H MRS at 7 T: initial results in human breast cancer

Abstract

This study demonstrates the feasibility of the noninvasive determination of important biomarkers of human (breast) tumor metabolism using high-field (7-T) MRI and MRS. (31) P MRSI at this field strength was used to provide a direct method for the in vivo detection and quantification of endogenous biomarkers. These encompass phospholipid metabolism, phosphate energy metabolism and intracellular pH. A double-tuned, dual-element transceiver was designed with focused radiofrequency fields for unilateral breast imaging and spectroscopy tuned for optimized sensitivity at 7 T. T(1) -weighted three-dimensional MRI and (1) H MRS were applied for the localization and quantification of total choline compounds. (31) P MRSI was obtained within 20 min per subject and mapped in three dimensions over the breast with pixel volumes of 10 mL. The feasibility of monitoring in vivo metabolism was demonstrated in two patients with breast cancer during neoadjuvant chemotherapy, validated by ex vivo high-resolution magic angle spinning NMR and compared with data from an age-matched healthy volunteer. Concentrations of total choline down to 0.4 mM could be detected in the human breast in vivo. Levels of adenosine and other nucleoside triphosphates, inorganic phosphate, phosphocholine, phosphoethanolamine and their glycerol diesters detected in glandular tissue, as well as in tumor, were mapped over the entire breast. Altered levels of these compounds were observed in patients compared with an age-matched healthy volunteer; modulation of these levels occurred in breast tumors during neoadjuvant chemotherapy. To our knowledge, this is the first comprehensive MRI and MRS study in patients with breast cancer, which reveals detailed information on the morphology and phospholipid metabolism from volumes as small as 10 mL. This endogenous metabolic information may provide a new method for the noninvasive assessment of prognostic and predictive biomarkers in breast cancer treatment.

7 Tesla MR Imaging: Opportunities and Challenges

“…Their results demonstrated a 5.7-fold increase in intrinsic SNR in the center of the breast at 7 T compared to 3 T. This strong gain in SNR is probably attributable to a combination of the increase of the magnetic field strength as well as optimization of the applied RF coils at 7 T. The modifications of the RF coil at 7 T include a change in alignment from parallel (at 3 T) to orthogonal (at 7 T) and a +/-45°an-gle with respect to the breast instead of a 0°angle at 3 T. This allows for a reduction of the relative distance from the conductors to the breasts at 7 T, enabling a more efficient filling factor of the coil [60]. The successful assessment of biomarkers for breast tumor metabolism at 7 T was also confirmed in further studies on ultrahigh-field breast MRS [61,62] Fig. 7).…”

“…Wijnen et al and Klomp et al investigated 31P (Phosphorus-31) MRS for the in-vivo detection and quantification of total choline compounds as well as levels of further biologic markers. They could show altered levels in patients with breast cancer and modulations under neoadjuvant therapy [61,62]. Hence, these biomarkers may bear the potential for the noninvasive assessment of prognostic and predictive biomarkers in breast cancer treatment.…”

Padé optimization of noise-corrupted magnetic resonance spectroscopic time signals from fibroadenoma of the breast

“…Contrary to these expectations, however, the diagnostic accuracy of MRS in distinguishing benign breast lesions from breast cancer was not found to be superior in studies using 3 T scanners [53,54] compared to those using 1.5 T scanners [51]. There have been some published data using even higher field (4 or 7 T) MR scanners [52,[55][56][57][58][59]. Whereas tCho levels were significantly elevated in breast cancer in an investigation [56] of 500 in vivo breast spectra using a 4 T scanner, tCho was also reported as being present in many benign breast lesions and in normal breast.…”

Detection of microcalcifications by characteristic magnetic susceptibility effects using MR phase image cross‐correlation analysis

“…Breast MR images were acquired using an Achieva 7 T (Philips Healthcare, Cleveland, OH) with a local transmit/receive breast coil 34 for unilateral focused transmission/reception using two circular elements 15 cm in diameter, orthogonally aligned and driven in quadrature. 35 A 3D gradient echo sequence with ProSet fat suppression (a selective excitation technique that employs a frequency and spatially selective excitation pulse to dephase fat and water proton signal) was used to obtain images sensitive to the phase signature of microcalcifications with a clinically practical acquisition time limit of 12 min and two spatial resolutions.…”