Caffeine

MR experiments (3 Tesla, Siemens Medical Solutions, Erlangen, Germany) were performed on a total of 39 healthy subjects (age 31±7 years, range 19–48 years, 23 males and 16 females). The protocol was approved by Institutional Review Board. Informed written consent was obtained for each participant. The body coil was used for RF transmission and a head coil was used for receiving. Foam paddings were used to stabilize the head to minimize motion. The subjects were instructed not to fall asleep during the experiments (verified after the session), as the cerebral blood flow and venous oxygenation may change during sleep. Four effective TEs were used: 0ms, 40ms, 80ms and 160ms, corresponding to 0, 4, 8 and 16 refocusing pulses in the T2-preparation (τ_CPMG=10ms). Other Imaging parameters: FOV=230mm, matrix=64×64, single-shot EPI, slice thickness=5mm, TR=8000ms, TE=19ms, TI=1200ms, repetition=4, thickness of labeling slab = 50 mm, gap between labeling slab and imaging slice = 25 mm, scan duration 4 minutes and 16 seconds.
In a sub-group of healthy subjects (n=6), the intra-session reproducibility was evaluated by performing five TRUST MRI scans at approximately 10 minute intervals. The same slice locations and imaging parameters were used for the five scans.
In a sub-group of healthy subjects (n=5), TR dependence of the measurement was investigated by performing TRUST MRI using TR values of 1.5 seconds to 8 seconds at 0.5 second intervals (14 different TR values). All other parameters were identical as specified above. The durations for the scans depended on TR and varied from 48 seconds to 4 minutes and 16 seconds. In one subject, the TI dependence was investigated (with fixed TR) and the TI values varied from 200ms to 2600ms (13 different TI values). All other parameters were identical as specified above.
In two healthy subjects, hypercapnia challenge (by breathing through a plastic tube with 600ml of volume, thereby increasing the dead-space (25 (link))) was induced and TRUST MRI was performed before, during, and after the challenge. End-tidal CO2 (EtCO2) was monitored throughout the experiment and was compared to MRI results.
In three healthy subjects, TRUST MRI was performed before and after 200mg caffeine tablet ingestion (26 (link)). The pre-caffeine scan was first performed. Then, while still inside the head coil, the subject was instructed to open his or her mouth for the researcher to place one tablet inside, and a small amount of water was administered via a straw to assist with swallowing. The MRI table was then repositioned to the iso-center. Twenty minutes later, the post-caffeine TRUST scan was performed. During the twenty minute waiting time, other anatomical scans (e.g. T1-weigthed anatomical imaging) were performed.
In three subjects, TRUST MRI was performed before and after the intravenous administration of Gd-DTPA contrast agent (Magnevist, Berlex Laboratories, Wayne, NY) at standard dosage (0.1 mmol/kg). The post-contrast TRUST was performed approximately 6 minutes after the injection of the contrast agent so that the agent concentration remained relatively constant for the duration of the TRUST scan.