Hyperpolarized (HP) MRI uses an exogenous contrast agent that has been polarized ~10,000x greater than thermal equilibrium polarization. Therefore, there is effectively no background signal, resulting in very high SNR data that can be used to non-invasively measure in vivo metabolism [1]. [1-¹³C] pyruvate has been used to study the conversion of pyruvate to lactate in human breast cancer cells [2], and the feasibility and safety of HP [1-¹³C] pyruvate has been demonstrated in prostate cancer patients [3]. In this first in woman study, we demonstrate the feasibility of acquiring dynamic 2D HP ¹³C spectra in breast cancer patients.

A 46-year-old woman with biopsy-confirmed invasive ductal carcinoma (NOS) was imaged prior to treatment using a dynamic 2D 13C spectroscopy sequence. The patient was imaged twice to assess repeatability. GMP [1-¹³C] pyruvic acid (Isotec) was mixed with a stable organic free radical (15 mM, GLP AH11501 sodium salt, GE Healthcare) under sterile conditions and laser welded in a sterile fluid-path (GE Healthcare). Following dissolution, the free radical was filtered out and the resulting solution was tested in a QA module. The patient was injected with 0.43 mL/kg followed by a 20 mL saline flush.

All MR data were acquired on a 3 T wide-bore scanner (GE Healthcare). Anatomic reference images were acquired with the body coil and ¹³C data were acquired using a clamshell transmit coil (GE Healthcare) and a 4-channel paddle coil (GE Healthcare) positioned anterior to the breast while the patient was prone. A 2D dynamic EPSI sequence was initiated upon completion of the injection, with a 4.3 s temporal resolution. The EPSI waveform was designed to acquire 16 spectra across a 16 cm FOV. Phase encoding was used to acquire 1x1x2 cm³ voxels.

The QC results were 247 mM pyruvate, pH 7.3, 2.7 µM free radical, 36.5°C, 19.0% polarization. The injection began 50 s following dissolution. The acquired spectrum shows pyruvate and lactate signal localized in the lesion (Figure 1). A map of the area under the lactate curve is shown overlaid on a T1-weighted anatomic reference image acquired with the body coil. The high signal in the pyruvate map is agrees well with the location of the tumor on the T1-weighted image.We have demonstrated the feasibility of acquiring hyperpolarized ¹³C spectra in breast cancer patients. Further study is warranted to optimize timing of the acquisition to account for the delivery of pyruvate to the breast and optimal sampling schemes to efficiently utilize the hyperpolarized signal. Observing the conversion of pyruvate to lactate in breast lesions may be useful for assessing treatment response.