Evaluation of different mathematical models and different b-value ranges of diffusion-weighted imaging in peripheral zone prostate cancer detection using b-value up to 4500 s/mm²

<div><p>Objectives</p><p>To evaluate the diagnostic performance of different mathematical models and different b-value ranges of diffusion-weighted imaging (DWI) in peripheral zone prostate cancer (PZ PCa) detection.</p><p>Methods</p><p>Fifty-six patients with histologically proven PZ PCa who underwent DWI-magnetic resonance imaging (MRI) using 21 b-values (0–4500 s/mm²) were included. The mean signal intensities of the regions of interest (ROIs) placed in benign PZs and cancerous tissues on DWI images were fitted using mono-exponential, bi-exponential, stretched-exponential, and kurtosis models. The b-values were divided into four ranges: 0–1000, 0–2000, 0–3200, and 0–4500 s/mm², grouped as A, B, C, and D, respectively. ADC, , D*, f, DDC, α, D_app, and K_app were estimated for each group. The adjusted coefficient of determination (R²) was calculated to measure goodness-of-fit. Receiver operating characteristic curve analysis was performed to evaluate the diagnostic performance of the parameters.</p><p>Results</p><p>All parameters except D* showed significant differences between cancerous tissues and benign PZs in each group. The area under the curve values (AUCs) of ADC were comparable in groups C and D (<i>p</i> = 0.980) and were significantly higher than those in groups A and B (<i>p</i>< 0.05 for all). The AUCs of ADC and K_app in groups B and C were similar (<i>p</i> = 0.07 and <i>p</i> = 0.954), and were significantly higher than the other parameters (<i>p</i>< 0.001 for all). The AUCs of ADC in group D was slightly higher than K_app (<i>p</i> = 0.002), and both were significantly higher than the other parameters (<i>p</i>< 0.001 for all).</p><p>Conclusions</p><p>ADC derived from conventional mono-exponential high b-value (3200 s/mm²) models is an optimal parameter for PZ PCa detection.</p></div

Evaluation of different mathematical models and different b-value ranges of diffusion-weighted imaging in peripheral zone prostate cancer detection using b-value up to 4500 s/mm² - Fig 3

<p><b>Boxplot of diffusion parameters calculated using different b-value ranges (groups A, B, C and D)</b>. (a-b, d-g), the mean values of ADC, , f, DDC, α, and D_app were significantly lower in cancerous tissues than in benign PZs in each group (h). The K_app in cancerous tissues was significantly higher than in benign PZs in each group. The value of D*, which had a large standard deviation, showed no significant difference between cancerous tissues and benign PZs in groups A and D but was significantly different in groups B and C(c).</p

Prostate cancer in a 61-year-old patient with high serum PSA level of 19.43 ng/ml.

<p>(a)Transverse T2-weighted anatomical image shows a hypointense lesion (white arrow) in the right middle peripheral zone of the prostate; (b) A series of b-value images are shown with the corresponding location to the transverse T2-weighted (unites, s/mm²); (c) Measured signal and fitted curves of cancerous tissue and the opposite side benign tissue using maximum b-value of 4500 s/mm² (group D).</p

Diagnostic performance of parameters calculated with different b-value ranges.

<p>Diagnostic performance of parameters calculated with different b-value ranges.</p

Graph showing variations in the adjusted R² values of the mono-exponential, bi-exponential, stretched-exponential and kurtosis models with an increase in b-value.

<p>The mean value of the adjusted R² of the mono-exponential model decreased with the increase of b-value, while the mean value of the adjusted R² of the bi-exponential, stretched-exponential and kurtosis models were stable and excellent with the increase of b-value (It should be noted that, because the adjusted R² values of the bi-exponential and stretched-exponential models were close, their curves have been superimposed).</p

Mean values and standard deviation of the adjusted R².

<p>Mean values and standard deviation of the adjusted R².</p

ROC curve analyses show the diagnostic accuracy of the diffusion parameters in distinguishing between cancerous tissues and benign PZs.

<p>In group A, K_app had the largest AUC (0.940), but the AUCs of ADC and K_app were not significantly different (<i>p</i> = 0.070). In groups B and C, the AUCs of ADC and K_app were comparable and significantly higher than those of the other parameters. In group D, the AUCs of ADC was slightly higher than that of K_app (0.957 vs 0.953, <i>p</i> = 0.002), and both were significantly higher than those of other parameters (<i>p</i>< 0.001 for all).</p

Diffusion parameters in benign PZs and cancerous tissues.

<p>Diffusion parameters in benign PZs and cancerous tissues.</p