Diffusion-Weighted More Sensitive Than T2-Weighted and Dynamic Contrast-Enhanced Images To Detect Prostate Cancer

A recent study was conducted to determine if the accuracy of prostate carcinoma detection on MRI is influenced by the presence of post-biopsy hemorrhage.

The study, published in Radiology, indicated an overall accuracy of 80% and 74% in the detection of prostate carcinoma in the peripheral zone and transitional zone, respectively, when combining findings obtained on T2-weighted, dynamic contrast-enhanced, and diffusion-weighted MR images.

The Study
This study evaluated 40 patients who were diagnosed with prostate carcinoma by ultrasound-guided prostate biopsy. These patients were referred for MRI evaluation following biopsy.

Methodology
MR imaging was performed on a 1.5-Tesla system.

Sequences included T2-weighted fast spin echo, T2-weighted echoplanar, diffusion-weighted (DW), T1-fast spin echo, and dynamic contrast-enhanced imaging. B-values of 0 and 800 seconds/mm2 were used during DW imaging.

Dynamic contrast enhanced images were obtained every 30 seconds for 2 minutes and 30 seconds.

The prostate gland was divided into 8 regions on the MR images according to the biopsy sites.

Each area was evaluated for presence of hemorrhage as well as neoplasm.

On the T2-weighted images, a lesion was considered to represent prostate carcinoma on the basis of the following criteria:

• homogeneous low-signal intensity with mass effect in the peripheral zone (PZ)
• well-circumscribed round or triangular focal low-signal intensity in the PZ, or ill-defined low-signal intensity area without a capsule in the transitional zone (TZ).

On the diffusion-weighted images, a focal high-signal intensity area represented neoplasm.

On dynamic contrast-enhanced images, a focal area that enhanced within the first 60 seconds was considered prostate carcinoma.

Results
There were 38 patients with postbiopsy hemorrhage, with a significantly higher hemorrhage score found in the PZ.

Diffusion-weighted imaging was more sensitive than dynamic contrast-enhanced imaging for detection of prostate carcinoma.

The sensitivity and specificity of detection was higher in the PZ than in the TZ, except for the apical regions where the sensitivity was <50%.

Combined MR imaging of prostate carcinoma detection with T2-weighted, DW, and dynamic contrast-enhanced examinations had a sensitivity and specificity of 69% and 85%, respectively.

The individual sensitivities and specificities for each of the MR imaging sequences were as follows:

• T2-weighted 51% and 91%
• DW 57% and 90%,
• dynamic contrast-enhanced 46% and 93%, respectively.

The combined imaging sequences had an accuracy of approximately 78%, which was higher than that of each sequence alone.

Conclusions
Interpretation of combined T2-weighted, dynamic contrast-enhanced, and diffusion-weighted MR image findings can yield reasonable diagnostic accuracy in both the peripheral zone and the transitional zone.

Reviewer’s Comments
The results of this study are useful in demonstrating that the combination of T2-weighted, DW, and dynamic contrast-enhanced MR imaging sequences can increase diagnostic confidence in the detection of prostate carcinoma.

In addition, DW imaging was found to be more sensitive than T2-weighted and dynamic contrast-enhanced images, and therefore should be considered a useful addition to one’s imaging protocol.

A limitation noted in this study was the small sample size.

Author: John Sabatino, MD.
Reference:
Tamada T, Sone T, et al. Prostate Cancer: Relationships Between Postbiopsy Hemorrhage and Tumor Detectability at the MR Diagnosis. Radiology; 2008; 248 (August): 531-539