Perfusion MRI using endogenous deoxyhemoglobin as a contrast agent: Preliminary data

Abstract

Purpose:To demonstrate the feasibility of mapping cerebral perfusion metrics with BOLD MRI during modulation of pulmonary venous oxygen saturation.Methods: A gas blender with a sequential gas delivery breathing circuit was used to implement rapid isocapnic changes in the partial pressure of oxygen of the arterial blood. Partial pressure of oxygen was initially lowered to a baseline of 40 mmHg. It was then rapidly raised to 95 mmHg for 20 s before rapidly returning to baseline. The induced cerebral changes in deoxyhemoglobin concentration were tracked over time using BOLD MRI in 6 healthy subjects and 1 patient with cerebral steno-occlusive disease. BOLD signal change, contrast-to-noise ratio, and time delay metrics were calculated. Perfusion metrics such as mean transit time, relative cerebral blood volume, and relative cerebral blood flow were calculated using a parametrized method with a mono-exponential residue function. An arterial input function from within the middle cerebral artery was used to scale relative cerebral blood volume and calculate absolute cerebral blood volume and cerebral blood flow. Results:In normal subjects, average gray and white matter were: BOLD change

Hemodynamic Imaging in Cerebral Diffuse Glioma—Part B: Molecular Correlates, Treatment Effect Monitoring, Prognosis, and Future Directions

“…Differential responses during separate oxygen and carbon dioxide modulation in the same tissue voxels may, in principle, hint at aberrant versus functional vasculature [ 201 ]. Interestingly, oxygen modulation has been also recently proposed as a means to study cerebral perfusion through rapid transient hemoglobin desaturation with the potential to substitute contrast-based perfusion [ 202 , 203 , 204 ] with advantages also relating to the avoidance of gadolinium contrast use [ 205 ], but application in the study of brain tumors is still lacking. Independently of these developments, the possibility of precise end-tidal oxygen modulation in isocapnic conditions has been preliminarily investigated as a means to provide a novel “imaging biomarker” to detail glioblastoma lesion microvascular features during BOLD imaging, exploiting hypoxia and hyperoxia as BOLD contrasts [ 206 ].…”

Investigations of hypoxia‐induced deoxyhemoglobin as a contrast agent for cerebral perfusion imaging

“…This rate of change results from the kinetics of gas in the lungs which require the dilution of the gas in the functional residual capacity (i.e., the gas remaining in the lung after exhalation). By contrast, the resumption of normoxia can be achieved within one breath as there is a greater inspired gas to lung PO 2 gradient available to raise lung PO 2 (Fisher et al, 2016 ; Poublanc et al, 2021 ).…”

“…Previously, Poublanc et al (2021) determined that CNR increased marginally with repeated hypoxic stimuli. In this study, we examined the CNR resulting from the three selected paradigms of the hypoxiainduced dOHb protocol and found little improvement between a single and double hypoxic bolus.…”

“…This method is described in greater detail in Poublanc et al ( 2021 ). Average CNR and ΔBOLD values for GM, WM, and GM/WM ratios were calculated for each participant.…”

“…Vu et al ( 2021 ) have led the way in exploring the application of pulmonary hypoxia for increasing the concentration of dOHb ([dOHb]) in arterial blood for the purpose of providing susceptibility contrast in MRI. Poublanc et al ( 2021 ) showed that one or two very brief (<60 s) episodes of pulmonary hypoxia‐generate boluses of dOHb which are then propagated through the arterial system. The PO 2 profile in the lungs is accurately reflected in the dOHb concentration versus time profile in the blood.…”