PT  - JOURNAL ARTICLE
AU  - J. Poublanc
AU  - O. Sobczyk
AU  - R. Shafi
AU  - J. Duffin
AU  - K. Uludag
AU  - J. Wood
AU  - C. Vu
AU  - R. Dharmakumar
AU  - J.A. Fisher
AU  - D.J. Mikulis
TI  - Perfusion MRI using endogenous deoxyhemoglobin as a contrast agent: preliminary data
AID  - 10.1101/2020.08.21.255802
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.08.21.255802
4099  - http://biorxiv.org/content/early/2020/09/18/2020.08.21.255802.short
4100  - http://biorxiv.org/content/early/2020/09/18/2020.08.21.255802.full
AB  - Background The paramagnetic properties of deoxyhemoglobin shorten T2* as do gadolinium based contrast agents. Induction of abrupt changes in arterial deoxyhemoglobin concentration ([dOHb]) can simulate intra-vascular injections of gadolinium for perfusion imaging.Aim To demonstrate the feasibility of making rapid changes in pulmonary venous hemoglobin saturation and employing the resulting changes in T2* to calculate flow metrics in the brain.Methods A gas blender with a sequential gas delivery breathing circuit and software enabling prospective arterial blood gas targeting was used to implement rapid isocapnic lung changes in the partial pressure of blood oxygen (PaO2). Lung PO2 was initially lowered to induce a low baseline [dOHb]. PaO2 was then rapidly raised to PaO2 ∼ 100 mmHg for 10 seconds and then rapidly returned to baseline. Blood oxygenation level dependent (BOLD) MRI signal changes were measured over time.Results Arrival delay, signal amplitude and change in BOLD discriminated between large arteries, tissue and veins. The median half-time of BOLD signal in the middle cerebral artery was 1.7 s, indicating minimal dispersion confirming effective rapid modulation of pulmonary venous PO2. The contrast-to-noise ratio in the cortex was 3. Calculations of arrival delay, cerebral blood volume, mean transit time and cerebral blood flow were within normal ranges from published literature values.Conclusion Non-invasive induction of abrupt changes in [OHb] may function as a novel non-invasive vascular contrast agent for use in perfusion imaging.Competing Interest StatementDrs Fisher and Mikulis contributed to the development of an automated end-tidal targeting device, RespirActTM which is designed, assembled, and made available as a research tool by Thornhill Medical Inc (TMI). TMI is a for profit spin-off company from the University Health Network/University of Toronto. Drs Fisher and Mikulis have equity in TMI. J. Poublanc, O. Sobczyk, R. Shafi, J. Duffin, K. Uludag, J. Wood, C. Vu, R. Dharmakumar declare no competing interests.