Comparison of appearance time in brain between red blood cell and plasma using H <sub>2</sub> <sup>15</sup> O and <sup>15</sup> O <sub>2</sub> applying positron emission tomography
<i>Background</i>. The appearance time of blood components in the brain provides complementary information about cerebral microvascular dynamics. Plasma and red blood cells (RBCs) behave differently in the microcirculation: while plasma can pass through peripheral layers of capillaries, RBCs carry oxygen and are affected by phenomena such as the Fåhræus-Lindqvist effect and plasma skimming. Our study aims at visualizing these differences<i>in vivo</i>using H<sub>2</sub><sup>15</sup>O PET to assess plasma appearance time (AT<sub>Plasma</sub>) and<sup>15</sup>O<sub>2</sub>PET to assess RBC appearance time (AT<sub>RBC</sub>), and demonstrated that the relative delay of RBCs compared with plasma correlates with the oxygen extraction fraction (OEF).<i>Methods</i>. We retrospectively analyzed PET images obtained with<sup>15</sup>O<sub>2</sub>and H<sub>2</sub><sup>15</sup>O administration in 40 patients, comprising a total of 63 scan data. Appearance time images were generated by fitting tissue curves both for the<sup>15</sup>O<sub>2</sub>(AT<sub>RBC</sub>) and H<sub>2</sub><sup>15</sup>O phases (AT<sub>Plasma</sub>). AT<sub>RBC</sub>and AT<sub>Plasma</sub>values were extracted from regions of interest (ROIs) and compared. Additionally, differences between AT<sub>RBC</sub>and AT<sub>Plasma</sub>(ΔAT) were analyzed in relation to OEF.<i>Results</i>. AT<sub>RBC</sub>and AT<sub>Plasma</sub>images exhibited similar spatial distributions. A strong correlation was observed between them as AT<sub>RBC</sub>= 0.80·AT<sub>Plasma</sub>+ 1.8,<i>r</i>= 0.86), with a slope significantly less than unity, suggesting that RBCs flow faster than plasma. The difference between the two (ΔAT) showed a moderate correlation with OEF (<i>r</i>= 0.44), suggesting that higher OEF values are associated with slower RBC movement relative to plasma. This finding suggests that under certain ischemic conditions, RBC flow is more severely impaired than plasma flow.<i>Conclusion</i>. This study demonstrates that AT<sub>RBC</sub>and AT<sub>Plasma</sub>are closely related measures of cerebral blood appearance time. The observed association between their difference and OEF suggests a potential link to ischemic pathology.
Authors
- Masatoshi Morimoto (ORCID: https://orcid.org/0000-0003-1897-4324)
- Keigo Ohmori
- Mitsumasa Murao (ORCID: https://orcid.org/0009-0003-6442-3643)
- Takashi Norikane (ORCID: https://orcid.org/0000-0002-0989-8369)
- Yukito Maeda (ORCID: https://orcid.org/0000-0001-5104-1273)
- Katsuya Mitamura
- Yoshihiro Nishiyama
- Yuri Manabe (ORCID: https://orcid.org/0000-0002-5286-157X)
- Takuya Kobata (ORCID: https://orcid.org/0000-0001-7633-8858)
- Tetsuhiro Hatakeyama (ORCID: https://orcid.org/0000-0003-2088-9153)
- Nobuyuki Kudomi (ORCID: https://orcid.org/0000-0002-3456-8740)
- Keisuke Miyake (ORCID: https://orcid.org/0000-0002-7611-6486)
- Yuka Yamamoto (ORCID: https://orcid.org/0000-0002-3912-4217)
Institutions
- Kagawa University (JP)
- Kagawa University Hospital (JP)
- Tokushima Bunri University (JP)
Publication Details
- Journal
- Biomedical Physics & Engineering Express
- Published
- 2025-11-04
- DOI
- https://doi.org/10.1088/2057-1976/ae1b0b
- Primary Topic
- Advanced MRI Techniques and Applications
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- Japan Society for the Promotion of Science