Renal T perfusion using an iron oxide nanoparticle contrast agent—influence of T₁ relaxation on the first‐pass response

Abstract

Quantitative perfusion measurements require accurate knowledge of the correlation between first-pass signal changes and the corresponding tracer concentration in tissue. In the present study, a detailed analysis of first-pass renal cortical changes in T 1 and T * 2 following bolus injection of the iron oxide nanoparticle NC100150 Injection was investigated in a pig model using a double-echo gradient-echo sequence. The estimated change in 1/T* 2 during first pass calculated from single-echo sequences was compared to the true double-echo-derived 1/T* 2 curves. Using a single-echo (TE ‫؍‬ 6 ms) spoiled gradient-echo sequence, the first-pass 1/T* 2 response following a bolus injection of 1 mg Fe/kg of NC100150 Injection was significantly underestimated due to counteracting T 1 effects. Signal response simulations showed that the relative error in the first-pass response decreased with increasing TE and contrast agent dose. However, both the maximum TE and the maximum dose are limited by excessive cortical signal loss, and the maximum TE is further limited by high temporal resolution requirements. The problem of T 1 contamination can effectively be overcome by using a double-echo gradient-echo sequence. This yields a first-pass response that truly reflects the tissue tracer concentration, which is a critical requirement for quantitative renal perfusion assessment. Magn Reson Med 47:298 -304, 2002.

Quantitative cerebral perfusion using the PRESTO acquisition scheme

“…This unexpected result is in contradiction to previous studies, in which the susceptibility-weighted signal was thought to have been contaminated predominantly by R1 (22). In analogy with the conclusions derived from perfusion experiments conducted with truly confined intravascular contrast agents, this error can potentially be eliminated using a double-echo gradient-echo sequence, which however may critically compromise the temporal resolution (22)(23)(24). For example, a single-shot double-echo EPI has been attractive for cerebral perfusion due to its inherent R2 dependency, but this technique is somewhat hampered by the limited number of slices available (25).…”

Dynamic contrast‐enhanced MRI in clinical oncology: Current status and future directions

“…Preliminary results indicate that dysprosium‐based relative cerebral blood volume (rCBV) maps are superior to those obtained with gadolinium chelates (53, 54). USPIO particles designed for bolus injection can be used as susceptibility contrast agents to study tissue perfusion (55, 56). Encouraging early clinical results using USPIO particles are beginning to appear in the literature (57, 58).…”

Renal hemodynamics and oxygenation in transient renal artery occluded rats evaluated with iron-oxide particles and oxygenation-sensitive imaging

“…Although most UPSIOs are known to remain in the intravascular compartment, the water exchange between blood and interstitum will to some extent reduce the spin-lattice relaxation time (denoted as T1). The results from the study by Bjørnerud et al indicated that T1 effects can lead to a significant underestimation of perfusion even in the absence of extravascular leakage, as reflected in the area and peak height of the first-pass curve following bolus injection of iron oxide nanoparticles [26]. This effect was not taken into consideration in our study.…”