Dynamic contrast-enhanced (DCE) MRI has been used to measure important tumor microenvironmental parameters, such as plasma flow (Fp), vascular permeability surface area product (PS), vascular plasma volume fraction (vp), and extravascular extracellular volume fraction (ve), that can be used for diagnosis of cancer as well as for prediction and monitoring of treatment response. However, accurate estimation of the kinetic parameters from DCE-MRI data still remains a challenging task, particularly due to difficulties in measurement of the arterial input function (AIF). Recently, we developed a photo-induced triplet harvesting (PTH) technique to quantify GBCA using Carbostyril 124 (cs124)-sensitized diethylenetriamine pentaacetic acid (DTPA) via induced triplet energy transfer to Tb-DTPA using a simple fluorescence plate reader that is widely available in research labs. It has been shown that the relaxivity r1 of Gd-DTPA-cs124 is quite close to that of Gd-DTPA. Furthermore, we established that sequential blood sampling following injection of Gd-DTPA-cs124 allows for the measurement of plasma clearance of Gd-DTPA-cs124 in mice which matched closely with that of Gd-DTPA. This figure illustrates the application of Gd-DTPA-cs124 with tail vein injection in a DCE-MRI experiment, incorporating blood sampling for direct validation of MRI-based quantification with fluorescence-based quantitative data.