MRI Perfusion Imaging Using Segmented Inversion Recovery Pulses

The patent divides the inversion recovery pulse into two separate components: a spatially non-selective IR pulse applied first, followed by a spatially selective IR pulse. This segmentation allows each pulse to serve a specific function - the non-selective pulse handles the baseline inversion while the selective pulse provides spatial specificity, preventing baseline drift that occurs when a single selective pulse is repeatedly applied.

The spatially non-selective IR pulse is applied as a preliminary action before the spatially selective IR pulse. This preliminary inversion of the entire region establishes a clean baseline state, ensuring that subsequent selective pulsing does not accumulate baseline deviations. The preliminary action prepares the magnetization state to prevent the perfusion curve from failing to return to baseline.

The patent applies inversion in a non-intuitive order by first applying the spatially non-selective IR pulse (which inverts the entire region including background) before the spatially selective pulse. This reverse ordering compared to conventional methods allows the non-selective pulse to suppress MT effects across the entire field of view, while the subsequent selective pulse maintains spatial specificity and SNR.

The spatially non-selective IR pulse serves multiple functions simultaneously: it inverts the magnetization of the entire region, suppresses MT effects across the whole field of view, and establishes a uniform baseline state. This multi-functionality allows a single pulse to address both the MT suppression requirement and the baseline stability requirement, while the selective pulse adds spatial specificity.