Effect of body position on cerebral perfusion: a comparison of supine and seated positions assessed using conventional and upright CT perfusion

[Formerhuman]

Effect of body position on cerebral perfusion: a comparison of supine and seated positions assessed using conventional and upright CT perfusion​

Spoiler: Authors

Katsuhiro Mizutani, Yoshitake Yamada, Minoru Yamada, Yoichi Yokoyama, Kenzo Kosugi, Keisuke Yoshida, Satoshi Takahashi, Takenori Akiyama, Masahiro Toda, Masahiro Jinzaki. /Tokyo, Japan

Abstract​

Objective​

Postural changes influence systemic hemodynamics and may affect cerebral perfusion; however, quantitative evaluation remains limited in vivo under physiological gravitational conditions. We aimed to assess posture-dependent alterations in cerebral perfusion using upright multidetector computed tomography perfusion (CTP), with whole-brain cerebral blood flow (CBF) as the primary outcome.

Materials and methods​

This was a single-center observational study of healthy volunteers approved by the institutional review board. Eighteen volunteers underwent CTP imaging in both the supine and seated positions on the same day using two 320-row multidetector CT scanners with identical systems. Whole-brain CBF was defined as the primary endpoint. Mean transit time (MTT) and cerebral blood volume (CBV) were evaluated as secondary outcomes. Paired comparisons were performed between postures, and exploratory analyses assessed regional changes and interindividual variability.

Results​

Whole-brain CTP-derived CBF was significantly higher in the seated position than in the supine position (32.9 ± 6.0 [mean ± standard deviation] versus 29.2 ± 5.6 mL/100 g/min; p = 0.010), representing a 1.15 ± 0.19-fold increase. CTP-derived MTT was significantly shorter in the seated position (4.25 ± 0.61 versus 4.63 ± 0.72 s; p = 0.035), and CTP-derived CBV showed a modest but significant increase (2.23 ± 0.16 versus 2.16 ± 0.17 mL/100 g; p = 0.044). Regional perfusion changes were consistent across brain segments with interindividual variability in postural responses.

Conclusions​

Upright CTP detected posture-associated differences in whole-brain CTP-derived perfusion metrics, suggesting potential utility for investigating physiological and pathological alterations in cerebral hemodynamics associated with postural change.

Relevance statement​

Upright CTP enables physiological evaluation of posture-related cerebral hemodynamics under gravitational loading and may provide new insights into cerebral circulation in both health and disease.

Key Points​

• Whole-brain cerebral blood flow increased by 15% in the seated position compared with supine using upright CT perfusion.
• Mean transit time shortened by 7% and cerebral blood volume increased modestly by 4% in the seated position.
• Perfusion responses showed marked interindividual variability, suggesting different physiological adaptations to posture.

Web | DOI | PDF | European Radiology Experimental - Open access

 

[ScoutB]

They found *greater* blood flow to the brain while seated compared to lying down? Huh.

They say:

[…] Thus, cerebral perfusion pressure in the seated position is expected to decrease relative to that in the supine position […] We hypothesized that CBF may increase to compensate for this reduction in cerebral perfusion pressure, ensuring sustained energy and oxygen supply to the brain.