Perfusion is a crucial physiological parameter for tissue function. To obtain perfusion-weighted images and consequently to measure cerebral blood flow (CBF), a newly developed flow-sensitive alternating inversion recovery (FAIR) technique was used. Dependency of FAIR signal on inversion times (TI) was examined; signal is predominantly located in large vessels at short TI, whereas it is diffused into gray matter areas at longer TI. CBF of gray matter areas in the human brain is 71 +/- 15 SD ml/100 g/min (n = 6). In fMRI studies, micro- and macrovessel inflow contributions can be obtained by adjusting TIs. Signal changes in large vessel areas including the scalp were seen during finger opposition at a TI of 0.4 s; however, these were not observed at a longer TI of 1.4 s. To compare with commonly used BOLD and slice selective inversion recovery techniques, FAIR and BOLD images were acquired at the same time during unilateral finger opposition. Generally, activation sites determined by three techniques are consistent. However, activation of some areas can be detected only by FAIR, not by BOLD, suggesting that the oxygen consumption increase couples with the CBF change completely. Relative and absolute CBF changes in the contralateral motor cortex are 53 +/- 17% SD (n = 9) and 27 +/- 11 SD ml/100 g/min (n = 9), respectively.

The continuous technological progress of magnetic resonance imaging (MRI), as well as its widespread clinical use as a highly sensitive tool in diagnostics and advanced brain research, has brought a high demand for the development of magnetic resonance (MR)-compatible robotic/mechatronic systems. Revolutionary robots guided by real-time three-dimensional (3-D)-MRI allow reliable and precise minimally invasive interventions with relatively short recovery times. Dedicated robotic interfaces used in conjunction with fMRI allow neuroscientists to investigate the brain mechanisms of manipulation and motor learning, as well as to improve rehabilitation therapies. This paper gives an overview of the motivation, advantages, technical challenges, and existing prototypes for MR-compatible robotic/mechatronic devices.

Flow-sensitive alternating inversion recovery (FAIR) is a recently introduced MRI technique for assessment of perfusion that uses blood water as an endogenous contrast agent. To characterize the FAIR signal dependency on spin tagging time (inversion time (TI)) and to validate FAIR for cerebral blood flow (CBF) quantification, studies were conducted on the rat brain at 9.4 T using a conventional gradient-recalled echo sequence. The T1 of cerebral cortex and blood was found to be 1.9 and 2.2 s, respectively, and was used for CBF calculations. At short TIs (<0.8 s), the FAIR signal originates largely from vascular components with fast flows, resulting in an overestimation of CBF. For TI > 1.5 s, the CBF calculated from FAIR is independent of the spin tagging time, suggesting that the observed FAIR signal originates predominantly from tissue/capillary components. CBF values measured by FAIR with TI of 2.0 s were found to be in good agreement with those measured by the iodoantipyrine technique with autoradiography in rats under the same conditions of anesthesia and arterial pCO2. The measured pCO2 index on the parietal cortex using the FAIR technique was 6.07 ml/100 g/min per mmHg, which compares well with the pCO2 index measured by other techniques. The FAIR technique was also able to detect the regional reduction in CBF produced by middle cerebral artery occlusion in rats.