ADC Mapping With 12 b Values: Can We Improve Image Quality In The Diffusion Sequence of Prostate MRI?

Author(s): Lucas Scatigno Saad, George De Queiroz Rosas, Homero José De Farias E Melo, Jacob Szejnfeld.

Introduction: Prostate cancer (PCa) is one of the most prevalent tumors in male population. Multiparametric magnetic resonance imaging (mp-MRI) of the prostate is of great importance in the diagnosis of PCa, with particular emphasis on diffusion-weighted sequences. Nevertheless, diffusion-weighted imaging (DWI) sometimes exhibits limited definition and sharpness, hindering characterization of suspect lesions and normal anatomy. To address this challenge in obtaining clearer images, was developed a DWI protocol with 12 b values. Objectives: To compare the sharpness and conspicuity of images obtained by DWI sequences with 4 versus 12 b values in the detection of PCa by mp-MRI. Secondarily, to validate the use of this new sequence in clinical practice by quantitative and comparative analysis of apparent diffusion coefficient (ADC) values, and correlate ADC values with the PI-RADS classification and Gleason score of identified tumors. Methods: A total of 158 mp-MRI scans were evaluated. In all scans, two diffusion sequences were performed, with 4 and 12 b values, and ADC maps were calculated for each (ADC4 and ADC12 respectively). Individual and comparative analyses of image sharpness and quality were done, followed by assessment of correlation with PI-RADS. A sensitivity comparison was also performed for the diagnosis of PCa and the degree of tumor differentiation (Gleason score). Results: Mean ADC4 and ADC12 values in normal tissues (ADC4, 1793.3×10-6 mm2/s; ADC12, 1100×10-6 mm2/s) were significantly higher than in areas of tumor (ADC4, 1105.9×10-6 mm2/s; ADC12, 689.4×10- 6 mm2/s) (p<0.001). ADC values correlated well with the PI-RADS classification, distinguishing scores 3, 4 and 5 and with ADC tending to decline as the Gleason grade (tumor aggressiveness) increased. The conspicuity of the images obtained on ADC12 maps was consistent with greater sharpness compared to ADC4 maps, with high inter-observer agreement and statistical relevanc