Application of Field-of-View Optimized and Constrained Undistorted Single Shot (FOCUS) with Intravoxel Incoherent...

Area of Science:

• Radiology
• Oncology
• Medical Imaging

Background:

• Locally advanced rectal cancer (LARC) requires accurate grading for treatment planning.
• Histologic grading is crucial but invasive methods carry risks.
• Non-invasive imaging techniques are needed for precise tumor characterization.

Purpose of the Study:

• To assess the efficacy of FOCUS with IVIM MRI at 3T for grading LARC.
• To determine if IVIM parameters can differentiate tumor grades non-invasively.

Main Methods:

• Retrospective analysis of 88 LARC patients undergoing 3T MRI.
• Acquisition of FOCUS DWI and FOCUS IVIM sequences.
• Analysis of apparent diffusion coefficient (ADC) and IVIM parameters (D, D*, f) in tumor and normal rectal wall.
• Comparison of normalized parameters (ADC_NOR, D_NOR, D*_NOR, f_NOR) between well/moderately and poorly differentiated groups.

Main Results:

• Tumor D and f parameters positively correlated with tumor grade (p < 0.001).
• All normalized parameters (ADC_NOR, D_NOR, D*_NOR, f_NOR) also correlated with tumor grade (p ≤ 0.007).
• The perfusion fraction (f_tumor) was the best discriminator, with an AUC of 0.927, achieving 88.9% sensitivity and 100% specificity at a 22.0% cutoff.

Conclusions:

• FOCUS IVIM-derived parameters, especially normalized ones, are valuable for predicting rectal cancer histologic grade.
• This non-invasive method aids in precise tumor grading and treatment strategy.
• The perfusion fraction (f) shows significant potential for differentiating tumor grades in LARC.