Functional MRI of human brain during breath holding by BOLD and FAIR techniques

BOLD (blood oxygenation level-dependent) and FAIR (flow-sensitive alternati ng inversion recovery) imaging techniques were used to investigate the oxyg enation and hemodynamic responses of human brain during repeated challenges of breath holding and prolonged single breath holding. The effects of diff erent breathing techniques on BOLD and FAIR image contrasts were carefully examined. With a periodic breath-holding paradigm of 30 s, global changes i n gray matter were observable both in T-2*-weighted and FAIR images. T-2*-w eighted images showed 1-4% relative signal intensity increases, while FAIR images demonstrated relative cerebral blood flow (CBF) increase up to 30-70 %. The activated pixels depicted in FAIR images were about three times less than those seen in T-2*-weighted images. With prolonged breath holding, it was observed that signal intensities in T-2*-weighted and FAIR images were dependent on the breathing techniques used. Breath holding after expiratio n gave rise to immediate signal intensity increases in T-2*-weighted and FA IR images, whereas breath holding performed after deep inspiration signals showed a biphasic change both in flow and T-2*-weighted. T-2*-weighted and FAIR signals showed a transient decrease before rising above the baseline l evel. (C) 1999 Academic Press.