Abstract
ObjectiveThe objective of our study was to investigate tumor conspicuity and the discrimination potential for tumor aggressiveness on diffusion-weighted magnetic resonance imaging (DW-MRI) with high b value at 3-T.Materials and MethodsThe institutional review board approved this study and waived the requirement for informed consent. A total of 50 patients with prostate cancer (69 cancer foci; 48 in the PZ, 20 in the TZ, and one in whole prostate) who underwent multiparametric prostate MRI including DW-MRI (b values: 0, 1000 s/mm2 and 0, 2000 s/mm2) on a 3-T system were included. Lesion conspicuity score (LCS) using visual assessment (1 = invisible for surrounding normal site; 2 = slightly high intensity; 3 = moderately high; and 4 = very high) and tumor-normal signal intensity ratio (TNR) were assessed, and apparent diffusion coefficient (ADC, ×10−3 mm2/s) of the tumor regions and normal regions were measured.ResultsMean LCS and TNR at 0, 2000 s/mm2 was significantly higher than those at 0, 1000 s/mm2 (p<0.001 for both). In addition, ADC at both 0, 1000 and 0, 2000 s/mm2 was found to distinguish intermediate or high risk cancer with Gleason score ≥7 from low risk cancer with Gleason score ≤6 (p<0.001 for both). Furthermore, ADC of tumor regions correlated with Gleason score at both 0, 1000 s/mm2 (ρ = −0.602; p<0.001) and 0, 2000 s/mm2 (ρ = −0.645; p<0.001).ConclusionsFor tumor conspicuity and characterization of prostate cancer on DW-MRI of 3-T MRI, b = 0, 2000 s/mm2 is more useful than b = 0, 1000 s/mm2.
Highlights
More than 240,000 men in the United States had a diagnosis of prostate cancer in 2012, and the disease is the second most common cause of cancer-related deaths for men in most Western countries [1,2]
For tumor conspicuity and characterization of prostate cancer on diffusion-weighted magnetic resonance imaging (MRI) (DW-MRI) of 3-T MRI, b = 0, 2000 s/mm2 is more useful than b = 0, 1000 s/mm2
Image characteristics of DW-MRI are reflected by differences in the rates of water molecule movement in different biologic tissues, and this movement is inversely correlated with tissue cellularity [6]
Summary
More than 240,000 men in the United States had a diagnosis of prostate cancer in 2012, and the disease is the second most common cause of cancer-related deaths for men in most Western countries [1,2]. A large b value can effectively suppress the T2 shine-through effect, which is otherwise depicted as high signal intensity on DW-MR images independent of diffusion restriction [9,10]. A higher b value can result in stronger diffusion-weighting and greater suppression of signal intensity in benign tissue without a conspicuous decrease in the water molecule diffusion, thereby increasing image contrast between the cancer lesion and benign tissue [11]. The use of higher b values, such as 2000 s/mm might be adapted for the detection and characterization of prostate cancer, since a 3-T MR scanner results in a 2-fold increase in SNR compared to a 1.5-T MR scanner. To clarify the significance of a high b value for the tumor detection, lesion conspicuity and evaluation of tumor aggressiveness, further investigation is necessary
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