Kitajima Kazuhiro, Kaji Yasushi, Kuroda Kagayaki, Sugimura Kazuro
Department of Radiology, Dokkyo Medical University, Tochigi, Japan.
Magn Reson Med Sci. 2008;7(2):93-9. doi: 10.2463/mrms.7.93.
To determine whether the apparent diffusion coefficient (ADC) obtained using a high b-value (2,000 s/mm2) is superior to that using a standard b-value (1,000 s/mm2) for discriminating malignant from normal peripheral tissue in the prostate.
Twenty-six patients with biopsy-proven prostate cancer underwent 1.5T magnetic resonance (MR) imaging including single-shot, echo-planar diffusion-weighted imaging (DWI) with repetition time/echo time, 3500/88 ms; 4-mm slice thickness; 1-mm interslice gap; 144x128 matrix; field of view, 250x250 mm; number of excitations, 10; and b-values, 0, 1,000, and 2,000 s/mm2. For each patient, ADC values were obtained for malignant and normal tissue using b=1,000 and 2,000 in a monoexponential model. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios in DWI were also evaluated.
At b=1,000, the mean ADC (x10(-3) mm2/s) for malignant tissue was 0.82+/-0.27 (range 0.43-1.29) and for normal tissue, 1.69+/-0.23 (1.31-2.18). At b=2000, the mean ADC for malignant tissue was 0.61+/-0.19 (0.30-0.94) and for normal tissue, 1.01+/-0.14 (0.73-1.35). Significant ADC overlap between the malignant and normal tissue was recognized at b=2000. As b-value increased, the mean SNR within malignant tissue decreased by 21.6%, and mean CNR decreased 17.3%.
Under the same imaging conditions, measuring ADC using a high b-value (2,000 s/mm2) in a monoexponential model has little diagnostic advantage over using the standard b-value (1,000 s/mm2) in discriminating malignant from normal prostate tissue.
确定在鉴别前列腺恶性外周组织与正常外周组织时，使用高b值（2000 s/mm²）获得的表观扩散系数（ADC）是否优于使用标准b值（1000 s/mm²）获得的表观扩散系数。
26例经活检证实为前列腺癌的患者接受了1.5T磁共振（MR）成像，包括单次激发回波平面扩散加权成像（DWI），重复时间/回波时间为3500/88 ms；层厚4 mm；层间距1 mm；矩阵144×128；视野250×250 mm；激励次数10次；b值为0、1000和2000 s/mm²。对于每位患者，在单指数模型中使用b = 1000和2000分别获取恶性组织和正常组织的ADC值。还评估了DWI中的信噪比（SNR）和对比噪声比（CNR）。
在b = 1000时，恶性组织的平均ADC（×10⁻³ mm²/s）为0.82±0.27（范围0.43 - 1.29），正常组织为1.69±0.23（1.31 - 2.18）。在b = 2000时，恶性组织的平均ADC为0.61±0.19（0.30 - 0.94），正常组织为1.01±0.14（0.73 - 1.35）。在b = 2000时，恶性组织与正常组织之间存在明显的ADC重叠。随着b值增加，恶性组织内的平均SNR下降21.6%，平均CNR下降17.3%。
在相同成像条件下，在单指数模型中使用高b值（2000 s/mm²）测量ADC在鉴别前列腺恶性组织与正常组织方面，相比使用标准b值（1000 s/mm²）几乎没有诊断优势。
