MEASUREMENT OF PERFUSION RATE IN HUMAN-MELANOMA XENOGRAFTS BY CONTRAST-ENHANCED MAGNETIC-RESONANCE-IMAGING

Reliable methods based on MRI for measurement of the perfusion rate in human tumors are highly warranted. Tumors of two amelanotic human mel anoma xenograft lines were subjected to dynamic H-1 MRI after i.v. adm inistration of gado-pentetate dimeglumine (Gd-DTPA). The aim was to in vestigate to what extent different perfusion parameters determined fro m the Gd-DTPA kinetics, i.e., the initial uptake rate, the maximal upt ake, the decay rate, and the perfusion rate calculated by use of the K ety equation, can be used as a reliable estimate of tumor perfusion ra te, Each parameter was calculated in dual; one calculation was based o n relative signal intensity increase (RSII) in T-1-weighted MR images and the other on Gd-DTPA concentration determined from the images. The perfusion parameters were compared with the perfusion rates determine d from measurement of tumor uptake of Rb-86 Or [C-14]iodoantipyrine. T he results showed that reliable estimates of tumor perfusion rate can be achieved from analysis of Gd-DTPA kinetics by use of the Kety equat ion. Gd-DTPA kinetics based on concentration might be used to achieve reliable estimates of absolute tumor perfusion rate, whereas reliable estimates of the relative perfusion rate might also be achieved from G d-DTPA kinetics based on RSII, The initial uptake rate, the maximal up take, and the decay rate of Gd-DTPA, however, are not reliable estimat es of tumor perfusion rate, mainly because these parameters are highly influenced by the tumor extracellular volume fraction in addition to the perfusion rate.