Julia Furtner
Arterial spin-labeling is an MRI technique that enables the quantitative determination of tissue blood flow values without the need to administer contrast agents, thus offering a noninvasive MRI perfusion sequence for the generation of cerebral perfusion maps. This method takes advantage of the fact that water protons of the arterial blood in the feeding vasculature of the brain are magnetically labeled and used as an endogenous tracer. After a specific inversion time, the labeled blood arrives at the plane in which the image is acquired. Conventional arterial spin-labeling techniques are characterized by a moderate spatial and temporal resolution; however, the increased clinical availability of high-field MRI scanners has helped to increase the signal-to-noise ratio.
In our study, we used multiple inversion times to track the labeled bolus dynamically over time, providing additional information about tumor physiology. The purpose of this study was to determine the inversion time with the largest differences in normalized intratumoral signal intensity between high-grade and low-grade astrocytomas, offering a totally noninvasive and rapid tool for glioma grading. The results of our study point out that the inversion time before expected cerebral perfusion shows the most significant difference, as well as the highest sensitivity and specificity for normalized intratumoral signal intensity values between high-grade and low-grade gliomas. Therefore, we suggest that the most significant intratumoral signal intensity in our study depicts tumor circulation, but not tumor perfusion, and should be called, more precisely, “normalized vascular intratumoral signal intensity.” This technique can be easily included in routine MRI diagnostics and provides a fast, easily applicable, and truly noninvasive method by which to depict tumor vascularization.