RAYMOND LEE^{1}, Gladys Lo^{1}, and Ka Fat John Chan^{1}

Apparent Diffusion Coefficient (ADC) maps obtained diffusion weighted imaging (DWI) have been shown to detect prostate cancer (PCa) and also correlate with tumor aggressiveness. Recent studies showed that improve detection of prostate cancer by high b-value DWI. However, high b-value images have an inherently low signal-to-noise ratio (SNR) and are prone to increased susceptibility artefact. Computed DWI (cDWI) is a method capable of obtaining high b-value images, which avoids the technical challenges of actually measuring them. Previous studies with limited sample size have evaluated the cDWI with high b-value but results were not conclusive. Current study may give an insight whether high b-value cDWI is valuable for differentiation of high risk versus low risk PCa.

1. K. Katahira, T. Takahara, T. C. Kwee et al., “Ultra-high-b-value diffusion-weighted MR imaging for the detection of prostate cancer: evaluation in 201 cases with histopathological correlation,. European Radiology, vol. 21, no. 1, pp. 188–196, 2011.

2. Y. Ueno, K. Kitajima, K. Sugimura et al., “Ultra-high b-value diffusion-weighted MRI for the detection of prostate cancer with 3-T MRI,” Journal of Magnetic Resonance Imaging, vol. 38, no. 1, pp. 154–160, 2013

3. M. C. Maas, J. J. F?utterer, and T. W. Scheenen, “Quantitative evaluation of computed high b value diffusion-weighted magnetic resonance imaging of the prostate,” Investigative Radiology, vol. 48, no. 11, pp. 779–786, 2013.

4. Metin et al, “Conspicuity of Peripheral Zone Prostate Cancer on Computed Diffusion-Weighted Imaging: Comparison of cDWI1500, cDWI2000, and cDWI3000,” BioMed Research International, Volume 2014, Article ID 768291, 6 pages.

67 year-old gentleman with a PSA level of 9.18ng/mL and a Gleason Score 4+4 Pca,

a. Transverse T2-weighted turbo spin echo MR image shows abnormal hypointense focus was identified in the right peripheral zone (arrow)

b. ADC map with reduced SI, ADC
value: 0.59 ×10^{-3} mm^{2}/s.

c-e. Acquired DWI_{0}, DWI_{400} ,
DWI_{800} with contrast ratio -0.4,-0.18 and -0.04 respectively.

f. cDWI_{1600} with contrast ratio 0.47 (significantly higher
than acquired DWI_{0}, DWI_{400} ,
DWI_{800} ).

Boxplot of ADC normal, ADC Low Risk PCa, ADC High Risk PCa

Boxplot of Contrast Ratio of DWI_{1600,} Low Risk Vs High Risk PCa

The sensitivity, specificity, calculated from the optimal
cut-off of the ROC curve (Figure 5) and the AUC (with 95% confidence intervals) using only
the ADC and CR cDWI_{1600}

The
ROC curves show the individual performance of ADC, CR cDWI1600 to discriminate low- and high-risk PCa