Quantification Of Perfusion & Permeability In Prostate Using Dynamic Contrast-Enhanced MRI With Inversion-Prepared Dual-Contrast Sequence

Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology
Article Date: 08 Jun 2009 - 1:00 PDT

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UroToday.com - The dynamic contrast-enhanced dynamic susceptibility contrast magnetic resonance imaging (DCE-DSC-MRI) technique presented in the article⁽¹⁾ is based on a novel dual-contrast sequence. The sequence is a gradient echo sequence that uses a single inversion pulse and subsequent acquisition of two contrasts/echoes with different inversion and echo times. Inversion preparation increases the signal-to-noise ratio in comparison to other gradient echo sequences. The blood volume in the prostate is relatively small, i.e., approximately one percent, while the interstitial contrast-agent-enhancing volume is approximately 20 percent. Therefore, conventional imaging sequences fail to separate the low contrast agent signal originating from the blood from that originating from interstitial tissue. The first contrast/echo is acquired with a short echo time and is T1-weighted, allowing quantification of the total signal contribution while failing to separate the blood signal from the interstitial contrast agent signal.

The second echo is acquired with a long echo time and is applied to assess susceptibility contrast. The susceptibility contrast specifically amplifies the contrast agent concentration difference between blood and interstitial volume in prostate tissue, thereby allowing quantification of the mean transit time of blood through the tissue capillaries. Therefore, the dual contrast approach allows us to estimate the contrast agent concentration in both prostate blood and prostate interstitium. In combination with an appropriate compartment model and post processing algorithms, the dual-contrast sequence enables in situ quantification of pharmacokinetic parameters in the prostate with unprecedented accuracy.

The high contrast-to-noise ratio of the novel sequence allows application of a more elaborate pharmacological model for quantifying physiological parameters. The method was used to quantify several physiological parameters including the fractional volumes of the blood and interstitial compartments, the blood transport parameters perfusion and bolus dispersion, and vessel permeability, which is the exchange parameter between blood and interstitium. Perfusion, in particular, enables statistically significant differentiation of prostate cancer from normal tissue, high-grade prostate cancer from chronic prostatitis, and chronic prostatitis from normal prostate tissue⁽²⁾. Quantification of these independent pharmacokinetic parameters might in the future help to establish noninvasive prognostic factors for prostate cancer and might allow a more precise differentiation between low-grade and high-grade prostate cancer. Moreover, the parametric maps generated with DCE-DSC-MRI can serve to individually tailor radiation therapy and allow monitoring the response to radiation or hormone therapy. Finally the quantification of physiological parameters improves inter- and intra- individual comparability of data obtained by different investigators and with different MR scanners.

1. Lüdemann L, Prochnow D, Rohlfing T, Franiel, Warmuth C, Taupitz M, Rehbein H, Beyersdorff D, Simultaneous quantification of perfusion and permeability in the prostate using dynamic contrast-enhanced magnetic resonance imaging with an inversion-prepared dual-contrast sequence. Annals of Biomedical Engineering 2009; 37:749-762.

2. Franiel T, Lüdemann L, Rudolph B, Rehbein H, Staak A, Taupitz M, Prochnow D, Beyersdorff D, Evaluation of normal prostate tissue, chronic prostatitis, and prostate cancer by quantitative perfusion analysis using a dynamic contrast-enhanced inversion-prepared dual-contrast gradient echo sequence. Invest Radiol 2008; 43:481-487.

Written by Tobias Franiel1 and Lutz Lüdemann2 as part of Beyond the Abstract on UroToday.com

¹ Department of Radiology, Charité - Universitätsmedizin Berlin, Charité Campus Mitte, Schumannstr. 20/21, 10117 Berlin, Germany
²Department of Radiotherapy, Charité - Universitätsmedizin Berlin, Charité Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany

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