Gadovist^® goes along well with apparent diffusion coefficients

The gadolinium-based contrast agent Gadovist^® does not disturb the signals generated during diffusion-weighted imaging (DWI). Post-contrast DWI evaluations within multiparametric MRI are as reliable as pre-contrast DWI assessments in prostate cancer.

Multiparametric magnetic resonance imaging (mpMRI) plays a crucial role in prostate cancer assessment. mpMRI usually combines T2-weighted imaging, diffusion-weighted imaging (DWI), and dynamic contrast-enhanced imaging (DCE). A study from 2011, by Liu X et al. suggested that intravenous application of contrast agent influences apparent diffusion coefficient (ADC) values on post-contrast DWI. If confirmed, this would influence the informative value of post-contrast DWI.

Chan Kyo Kim and colleagues, Sungkyunkwan University, Seoul, Korea, performed a retrospective study on the issue. They qualitatively and quantitatively compared pre- and post-contrast ADC and exponential ADC (EADC) maps of patients with proven prostate cancer.

Method

Kim et al. included 34 patients with 34 prostate biopsy-proven prostate cancer lesions in their study. All patients had undergone a 3T MRI with Gadovist^® (Bayer Healthcare) and a DWI with three b-values (0, 100, 1000) before and after contrast administration.

Two experienced genitourinary radiologists in consensus located the cancers on the MR images based on the results marked on the histopathological cancer map generated by an experienced genitourinary pathologist. Both radiologists rated the image quality in consensus on a four-point scale, ranging from 1–poor to 4–excellent. They also calculated the pre- and post-contrast ADC and EADC values in a region of interest (ROI) in the malignant lesion and in the benign area.

Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were estimated for DWI and ADC and EADC maps. Bland-Altman plots were used to calculate measurement consistency between pre- and post-contrast values.

Results

Image quality was mostly good or excellent for all images before and after contrast administration. Only four image sets were rated as “fair quality”, two in the pre- and two in the post-contrast series.

ADC and EADC in the cancerous lesion or in the benign area did not differ significantly between pre- and post-contrast imaging series.
SNR and CNR on DWI, ADC or EADC in the cancerous lesion or in the benign area did not differ significantly between pre- and post-contrast imaging series.

Bland-Altman plots showed a low variability of 3.2% between pre- and post-contrast imaging series in ADC and EADC measurements.

Conclusion

Administering a gadolinium-based contrast agent for assessing prostate cancer does not influence the ADC or EADC maps based on DWI signaling. Neither qualitative nor quantitative pre- and post-contrast DWI assessments differ significantly from each other. However, Kim et al. suggest further studies with a larger study population to verify their findings.

Original Article: Prostate diffusion-weighted imaging at 3T: effect of intravenous gadobutrol administration.