Field cycling imaging to characterise breast cancer at low and ultra-low magnetic fields below 0.2 T

This prospective feasibility study explores Field-Cycling Imaging (FCI), a new MRI technology that measures the longitudinal relaxation time across a range of low magnetic field strengths, providing additional information about the molecular properties of tissues. This study aims to assess the performance of FCI and investigate new quantitative biomarkers at low fields within the context of breast cancer.

We conducted a study involving 9 people living with breast cancer (10 tumours in total, mean age, 54 ± 10 years). FCI images were obtained at four magnetic field strengths (2.3 mT to 200 mT). FCI images were processed to generate T1 maps and 1/T1 dispersion profiles from regions of tumour, normal adipose tissue, and glandular tissue. The dispersion profiles were subsequently fitted using a power law model. Statistical analysis focused on comparing potential FCI biomarkers using a Mann-Whitney U or Wilcoxon signed rank test.

We show that low magnetic fields clearly differentiate tumours from adipose and glandular tissues without contrast agents, particularly at 22 mT (1/T₁, median [IQR]: 6.8 [3.9-7.8] s^-1 vs 9.1 [8.9-10.2] s^-1 vs 8.1 [6.2-9.2] s^-1, P < 0.01), where the tumour-to-background contrast ratio was highest (62%). Additionally, 1/T₁ dispersion indicated a potential to discriminate invasive from non-invasive cancers (median [IQR]: 0.05 [0.03-0.09] vs 0.19 [0.09-0.26], P = 0.038).

To the best of our knowledge, we described the first application of in vivo FCI in breast cancer, demonstrating relevant biomarkers that could complement diagnosis of current imaging modalities, non-invasively and without contrast agents.