3320 - Quantitative Magnetic Resonance Imaging to Differentiate Clinically Significant Tumor from Other Tissues in the Prostate

Purpose/Objective(s): Simultaneous integrated boost (SIB) radiation to the intraprostatic clinically significant tumor foci is being used increasingly as a component of external beam radiation therapy to increase biochemical disease-free survival without increasing toxicity. Contouring of intraprostatic tumors in dose-escalated approaches relies on tumor-delineation on image-guided biopsy results and multiparametric (mp-) magnetic resonance imaging (MRI). However, the interpretation of the mp-MRI data is mostly qualitative and varies among institutions and physicians. Quantitative imaging techniques such as magnetic resonance fingerprinting (MRF) provide direct measurements of numerical MRI parameters such as T₁ and T₂ relaxation times. The purpose of this work is to test the utility of MRF in differentiating clinically significant tumor from other tissues in the prostate in patients with prostate cancer (PCa).

Materials/Methods: A total number of ten patients with intermediate and high risk PCa referred for radiation therapy were recruited for a preliminary study. Patients underwent MRF scans and standard-of-care mp-MRI including T₂-weighted MRI, diffusion-weighted MRI and T₁-weighted MRI after contrast, 12-16 core template-based transrectal-ultrasound (TRUS)-guided biopsies with target lesions localized based on MRI reads. Radiation oncologists contoured the prostate, prostate zones (peripheral and transition zone) and clinically significant tumor foci as the potential target for radiation boost on the MRI images. Quantitative MRI parameters including apparent diffusion coefficients (ADC) from diffusion-weighted MRI, T₁ and T₂ values from MRF were calculated for evaluation.

Results: In both the peripheral zone and the central gland of the prostate, T₁, T₂ and ADC values were significantly lower (P<0.05) in the contoured csT foci than other tissues in the same zone of the prostate. Mean and standard deviation of the quantitative outputs (T₁, T₂, and ADC) were listed in Table 1.

Conclusion: Quantitative MRI showed great potential in differentiating clinically significant tumor from other tissues in both the peripheral and transition zone of the prostate in PCa patients. Application of these quantitative imaging techniques into the routine radiation therapy workflow may help to improve the standardization of the process and reduce the variations in treatment target delineation.