Characterisation of fibrosis in chemically-induced rat mammary carcinomas using multi-modal endogenous contrast MRI on a 1.5T clinical platform

Bimodal magnetic resonance and optical imaging of extracellular matrix remodelling by orthotopic ovarian tumours

BACKGROUND

The extracellular matrix modulates the development of ovarian tumours. Currently, evaluation of the extracellular matrix in the ovary is limited to histological methods. Both magnetic resonance imaging (MRI) and two-photon microscopy (2PM) enable dynamic visualisation and quantification of fibrosis by endogenous contrast mechanisms: magnetisation transfer (MT) MRI and second-harmonic generation (SHG) 2PM, respectively.

METHODS

Here, we applied the MT-MRI protocol for longitudinal imaging of the stroma in orthotopic human ovarian cancer ES-2 xenograft model in CD1 athymic nude mice, and for orthotopically implanted ovarian PDX using a MR-compatible imaging window chamber implanted into NSG mice.

RESULTS

We observed differences between ECM deposition in ovarian and skin lesions, and heterogeneous collagen distribution in ES-2 lesions. An MR-compatible imaging window chamber enabled visual matching between T2 MRI maps of orthotopically implanted PDX grafts and anatomical images of their microenvironment acquired with a stereomicroscope and SHG-2PM intravital microscopy of the collagen. Bimodal MRI/2PM imaging allowed us to quantify the fibrosis within the same compartments, and demonstrated the consistent results across the modalities.

CONCLUSIONS

This work demonstrates a novel approach for measuring the stromal biomarkers in orthotopic ovarian tumours in mice, on both macroscopic and microscopic levels.

Stromal Collagen Content in Breast Tumors Correlates With In Vivo Diffusion-Weighted Imaging: A Comparison of Multi b-Value DWI With Histologic Specimen From Benign and Malignant Breast Lesions

BACKGROUND

Increased deposition and reorientation of stromal collagen fibers are associated with breast cancer progression and invasiveness. Diffusion-weighted imaging (DWI) may be sensitive to the collagen fiber organization in the stroma and could provide important biomarkers for breast cancer characterization.

PURPOSE

To understand how collagen fibers influence water diffusion in vivo and evaluate the relationship between collagen content and the apparent diffusion coefficient (ADC) and the signal fractions of the biexponential model using a high b-value scheme.

STUDY TYPE

Prospective.

SUBJECTS/SPECIMENS

Forty-five patients with benign (n = 8), malignant (n = 36), and ductal carcinoma in situ (n = 1) breast tumors. Lesions and normal fibroglandular tissue (n = 9) were analyzed using sections of formalin-fixed, paraffin-embedded tissue stained with hematoxylin, erythrosine, and saffron.

FIELD STRENGTH/SEQUENCE

MRI (3T) protocols: Protocol I: Twice-refocused spin-echo echo-planar imaging with: echo time (TE) 85 msec; repetition time (TR) 9300/11600 msec; matrix 90 × 90 × 60; voxel size 2 × 2 × 2.5 mm³ ; b-values: 0 and 700 s/mm² . Protocol II: Stejskal-Tanner spin-echo echo-planar imaging with: TE: 88 msec; TR: 10600/11800 msec, matrix 90 × 90 × 60; voxel size 2 × 2 × 2.5 mm³ ; b-values [0, 200, 600, 1200, 1800, 2400, 3000] s/mm² .

ASSESSMENT

Area fractions of cellular and collagen content in histologic sections were quantified using whole-slide image analysis and compared with the corresponding DWI parameters.

STATISTICAL TESTS

Correlations were assessed using Pearson's r. Univariate analysis of group median values was done using the Mann-Whitney U-test.

RESULTS

Collagen content correlated with the fast signal fraction (r = 0.67, P < 0.001) and ADC (r = 0.58, P < 0.001) and was lower (P < 0.05) in malignant lesions than benign and normal tissues. Cellular content correlated inversely with the fast signal fraction (r = -0.67, P < 0.001) and ADC (r = -0.61, P < 0.001) and was different (P < 0.05) between malignant, benign, and normal tissues.

DATA CONCLUSION

Our findings suggest stromal collagen content increases diffusivity observed by MRI and is associated with higher ADC and fast signal fraction of the biexponential model.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;51:1868-1878.