Tumour size measurement in a mouse model using high resolution MRI

Area of Science:

• Biomedical Imaging
• Cancer Research
• Preclinical Studies

Background:

• Animal models are crucial for evaluating new cancer treatments.
• Magnetic Resonance Imaging (MRI) allows non-invasive, in vivo monitoring of tumor tissue for longitudinal studies.
• MRI-based tumor size measurements require validation for small tumors (10-2 to 10-1 g).

Purpose of the Study:

• To assess the accuracy of MRI-based tumor size measurements in small mouse tumors.
• To compare the efficacy of 2D and 3D MRI techniques for tumor volume assessment.
• To determine the optimal MRI acquisition parameters for accurate tumor quantification.

Main Methods:

• Acquisition of 2D and 3D T2-weighted RARE MRI images in tumor-bearing mice using a 7T animal MR system.
• Varied image resolution for 3D acquisitions.
• Tumor mass determination via in-house software (assuming 1 g/cm³ density) and comparison with necropsy weights.

Main Results:

• Strong correlation observed between MRI-determined and necropsy-determined tumor masses.
• 3D acquisition showed slightly higher accuracy than 2D for very small tumors (<0.2 g) regarding inter- and intraobserver variation.
• Increased voxel size in 3D images (up to 2403 μm³) did not significantly impact results, reducing acquisition time.

Conclusions:

• 2D MRI is adequate for accurate tumor size measurement.
• 3D MRI acquisition is necessary for small tumors (<0.2 g) to minimize interobserver variation.
• Efficient MRI acquisition times (15-50 minutes) enable further investigations like perfusion or diffusion within the same session.