Hypointensity on Diffusion-Weighted MRI of the Brain Related to T2 Shortening and Susceptibility Effects

Hollow manganese oxide nanoparticle-enhanced MRI of hypoxic-ischaemic brain injury in the neonatal rat

“…In our study, there was a signal loss in the injured dorsolateral thalamus on diffusion-weighted images and ADC maps. This can be explained by the phenomenon called "T 2 blackout", 26 which represents susceptibility effects caused by paramagnetic effects of HMON. In contrast with ADC measurement, HMON-enhanced MRI may have an advantage in visualizing apoptotic area even in the later period after ischaemic injury.…”

Diffusion tensor imaging of deep gray matter brain structures: Effects of age and iron concentration

“…Deep gray matter structures have a unique MR signal intensity in the elderly, with profound signal darkening on T 2 * and T 2 -weighted images in some regions, especially the putamen (Hiwatashi et al, 2003;Thomas et al, 1993). There is ample evidence indicating that these local age effects are due to age-related iron deposition (in vivo: 7,18,postmortem: Hallgren and Sourander, 1958), which may be a marker of occult vascular disease and a correlate of age-related decline in cognitive or motor functions associated with the iron-laden subcortical structures (Pujol et al, 1992).…”

“…Commonly but not necessarily, diffusivity negatively correlates with anisotropy within white matter samples (Chen et al, 2001;Engelter et al, 2000;Head et al, 2004;Helenius et al, 2002;Naganawa et al, 2003;Pfefferbaum et al, 2005;Sullivan, 2005b, 2003), probably reflecting an age-related increase in unbound interstitial fluid (e.g., Norris et al, 1994;Peters and Sethares, 2003;Pfefferbaum and Sullivan, 2005b;Rumpel et al, 1998;Sehy et al, 2002;Silva et al, 2002). Signal loss attributable to iron deposition is especially conspicuous on diffusion-weighted spin-echo images (Hiwatashi et al, 2003). Although greater presence of free water should result in increased MD and reduced R 2 (c.f., Pfefferbaum et al, 1999), these fluid-related age effects on MD may be more reflective of spin-spin R 2 changes than are R 2 estimates from multi-echo spin-echo MRI data.…”

Brain

“…However, DWI, being driven by echo-planar imaging (EPI), is prone to susceptibility artifacts ( Fig. 10.7b ), particularly at the air-bone interface, and hence prone to falsenegative and false-positive pitfalls particularly in the temporal lobes ( Fig Another pitfall of high signal on DWI is the phenomenon of "T2 shine-through" caused by T2 prolongation (rather than true restricted diffusion) contributing to hyperintensity, typically in subacute to chronic infarction, when the apparent diffusion coeffi cient (ADC) is pseudonormalized or increased, respectively ( of the relationship between ADC, transverse (T2) relaxation time, and proton density (as well as b value, and TE), which infl uence DWI signal intensity (Mandell et al 2012 ;Hiwatashi et al 2003 ). This pitfall may be avoided by reviewing ADC maps.…”

“…This pitfall may be avoided by reviewing ADC maps. The opposite effects of overwhelming susceptibility from blood products causing T2 shortening (hypointensity) resulting in DWI hypointensity is typically seen in acute (deoxyhemoglobin) and early subacute (extracellular methemoglobin) stage hematomas (Hiwatashi et al 2003 ;Silvera et al 2005 ). However, hyperintense spontaneous hematomas with decreased ADC values may be seen at the earliest hyperacute (oxyhemoglobin) and late subacute (extracellular methemoglobin) stages and may thus mimic hyperacute arterial stroke on DWI (Silvera et al 2005 ).…”