Fig. 4.

Relationship of baseline oxygenation-sensitive signal intensity and signal intensity response in relationship to hemoglobin changes in healthy males. a There was strong negative relationship between changes in hemoglobin concentration and signal intensity on oxygenation-sensitive images before and after rapid infusion of Lactated Ringer’s solution in healthy men (r = 0.82, p = 0.002) at rest, suggesting an increase in relative SI with decreasing hematocrit. b Relationship between the extent of hemodilution and the attenuation of the maximal signal intensity response during apnea (r = 0.63, p = 0.037) and c) at the end of the breath-hold (r = 0.68, p = 0.016) in healthy males. A significantly decreased hemoglobin level was associated with a stronger attenuation of the signal intensity response in healthy males