2008 - Semiquantitative Analysis of DCE-MRI Perfusion Parameters in Spinal Metastases after RT: Treatment Response vs. Non-Response

Purpose/Objective(s): Dynamic contrast-enhanced MRI (DCE-MRI) is a non-invasive imaging technique used to characterize the perfusion of spine metastases using Toft’s pharmacokinetic model and time intensity curves (TICs). Spinal metastases often show reduced plasma volume (Vp) after radiation treatment (RT), but changes in TIC pattern and signal intensity (SI), two semi-quantitative measures that do not require kinetic modeling, remain understudied. The purpose of this study is to investigate whether the TIC pattern and SI can be used to differentiate between treatment response and non-response groups. We hypothesize that treatment response is associated with changes in TIC morphology and decreased SI on post-RT DCE-MRI.

Materials/Methods: Retrospective study of 79 lesions in 53 patients that underwent DCE-MRI before and after RT to a treatment-naïve spinal metastasis. NordicICE was used to generate TICs and maximum SI for each lesion. Lesions were characterized as treatment responsive(n=62) or treatment non-responsive(n=17) based on an established ?Vp(-40%) cutoff¹. Wilcoxon signed-rank tests were conducted at a significance level of P<0.05 to assess post-RT changes in SI within each group.

Results: In both groups, we observed an averaged type D curve (fast initial wash-in and early wash-out) pattern prior to RT, which is common in malignant vertebral lesions. After RT, the treatment response group shifted to an averaged type E pattern (initial wash-in followed by gradual accumulation), which is associated with benign inflammatory processes. The treatment non-response group shifted to an averaged type C pattern (fast initial wash-in followed by plateau), which is non-specific and seen in benign and malignant processes². The averaged maximum SI in the treatment response group prior to RT was 3.93 and 2.475 after RT (P=2.59*10^-5). The averaged maximum SI in the treatment non-response group prior to RT was 2.86 and 3.016 after RT (P=0.7819).

Conclusion: The treatment response group resembled a type E pattern after RT. The observed slower rate of contrast accumulation suggests treatment-induced microvascular alterations affecting perfusion into the tumor. The decreased max SI further suggests decreased total contrast accumulation and reduced functional vascularity. The treatment non-response group resembled a type C pattern after RT. The slope of the wash-in phase was similar to the pre-RT type D pattern and had a similar max SI. This suggests a preservation of the tumor’s vascular network. Our findings indicate that a TIC shift to type E and C is associated with treatment response and non-response, respectively. Semi-quantitative analysis in DCE perfusion MRI can provide a critical tool for evaluating treatment response in spinal metastases.