磁振造影的優點為高度的解像能力及非侵入性檢查。有鑑於此，利用磁振造影技術來研究隨著年齡而變化的血液動力特性已行之有年。能夠了解與年齡相關的腦部生理參數不僅僅能夠用於評估臨床病理的狀況，也能觀察正常的老化過程。此外，動物模型更是一項研究與年齡相關之神經科學研究的利器。
在此論文中，我們將先探討在isoflurane的麻醉下，電刺激大鼠臉部肌肉區的功能性磁振造影之再現性。結果顯示在連續三周進行fMRI實驗下，活化區域皆可重複地出現在主要體感覺桶狀皮質區、次要體感覺皮質區以及主要體感覺頷皮質區。一但檢驗過此動物模型的再現性之後，我們將著重在年齡對於大鼠的功能性磁振造影的影響。結果發現，不管在活化區大小、引起的訊號變化、血液動力延遲以及時態對比雜訊率方面，三個月大的老鼠以及十五個月大的老鼠其表現都沒有顯著差別。因此我們推斷，在進行功能性磁振造影實驗包含此一年齡範圍的大鼠時，將不用特別考慮年齡會造成的影響。
論文的最後一部分將探討與年齡相關的總體腦部氧代謝率。此一研究包含118位健康受試者，其年齡分布為18-74歲。我們分別利用相位對比磁振造影技術來量測腦部血流量以及利用T2遲緩時間質子標記法來量測上矢狀竇的含氧濃度。結合這兩項技術，我們將可量測出總體腦部氧代謝率。結果顯示，腦部氧代謝率將會隨著年齡增加而增加，這暗示著老化的腦需要消耗更多的能量才能維持正常的功能。此外，和男性相比，女性的腦部氧代謝率受年齡影響較緩。這也暗示著，腦部氧代謝率隨時間的變化會因性別不同而展現出不同的時間模式。

With the merit of high spatial resolution and non-invasive, investigations on the hemodynamic changes with age via magnetic resonance imaging (MRI) techniques have flourished for years. The understanding of normal age-associated values in brain would help evaluate not only clinical-pathologic conditions but also normal aging processes. In addition, animal studies provide approaches to better understanding in the field of age-related neuroscience research.
This thesis first explores the reproducibility of rat fMRI study by employing electric mystacial pad stimulation under isoflurane anesthesia. Results showed that all rats exhibited reproducible activation in primary somatosensory barrel field cortex (S1BF), secondary somatosensory cortex (S2) and the primary somatosensory jaw region cortex (S1J) in all fMRI sessions in 3 successive weeks. Once the reproducibility was tested, we had examined age-related changes in the animal fMRI studies for the first time. In terms of the spatial extent of activation, induced signal change, hemodynamic delay and temporal contrast-to-noise ratio, there was no significantly different between 3-month-old and 15-month-old rats. These findings suggested the further age-related correlation is not needed in rodent fMRI studies composed of rats aging up to 15-month-old.
The final part of this thesis is designed to assess age-related differences in global cerebral metabolic rate of oxygen (CMRO2) in a relatively large cohort (118 subjects) with a wide age range (18-74 years). Computation of CMRO2 is based on global cerebral blood flow (CBF) obtained from phase-contrast MRI and venous oxygen saturation (Yv) measurements in the superior sagittal sinus with a T2 relaxation experiment. The central finding is that CMRO2 increases with age, suggesting the aged brain may engage more energy to maintain the same functionality. In addition, women have a slower rate of CMRO2 change when compared to men (P<0.001 for interaction term), indicating a sex-difference in its temporal pattern.

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