However, what might be considered an artefact in structural imaging may be of value in functional imaging the most popular functional MRI technique (BOLD fMRI, cf. [91]) is based on the oxygenation-dependent magnetic susceptibility of haemoglobin in blood that flows through the organism in a task-dependent manner (for recent review, see [92]).
MRS acquisition based on the blood oxygenation level dependent (BOLD) contrast mechanism was implemented at 3 T to investigate the impact of a non-conventional spectral averaging scheme (determined by the number of RF excitations, NEX) on the dynamics of cerebral metabolism during neuroactivation.
The typical functional magnetic resonance imaging (fMRI) study measures signal changes based on the blood oxygenation level dependent (BOLD) [1] effect.
Functional magnetic resonance imaging (fMRI) based on the blood oxygenation level-dependent (BOLD) contrast was performed using a 3T Siemens Allegra scanner housed in the Ahmanson-Lovelace Brain Mapping Center and a standard headcoil.
Functional data based on the blood oxygenation level-dependent (BOLD) signal were acquired using a multiple gradient echo-planar T2*-weighted pulse sequence, with the parameters: TR = 2000 ms; TE = 30 ms; flip angle = 90°; imaging matrix = 64 × 64; FOV = 192 mm axial slices.
Resting state functional data, based on the blood oxygenation level-dependent (BOLD) signal, were acquired using a three Tesla Verio scanner (Siemens, Erlangen, Germany), and using a multiple gradient echo-planar T2*-weighted pulse sequence, with the parameters: TR = 2410 ms; TE = 30 ms; flip angle = 90°; imaging matrix = 64 × 64; FOV = 192 mm axial slices.
The use of BOLD-MRI for assessment of tissue hypoxia is based on the assumption that oxygenation of haemoglobin is related to blood arterial pO2 (as described by the oxygen-haemoglobin dissociation curve), which is in equilibrium with oxygenation of surrounding tissues.
Comparisons of the variables in pure PJP patients who were subdivided into two groups based on the variables including oxygenation index, the use of ventilator or survivor status were made using the Mann–Whitney U test.
The patients were divided into two groups based on the results of analysis of the oxygenation status immediately after DHP-PMX (Group A, increase of the PaO2/FiO2 ratio by more than 20% (six cases); Group B, increase of the PaO2/FiO2 ratio by 20% or less (six cases)).
The simulation results demonstrate the optimal control of oxygenation based on the proposed PIA by iteratively evaluating the Hamiltonian cost functions and synthesizing the control actions until achieving the converged optimal criteria.
This technique is based on the assumption that increased tissue oxygenation represents a greater regional cerebral blood flow.
