Abstract
PurposeTo evaluate blood oxygenation level‐dependent (BOLD) contrast changes in healthy breast parenchyma and breast carcinoma during administration of vasoactive gas stimuli.Materials and MethodsMagnetic resonance imaging (MRI) was performed at 3T in 19 healthy premenopausal female volunteers using a single‐shot fast spin echo sequence to acquire dynamic T 2‐weighted images. 2% (n = 9) and 5% (n = 10) carbogen gas mixtures were interleaved with either medical air or oxygen in 2‐minute blocks, for four complete cycles. A 12‐minute medical air breathing period was used to determine background physiological modulation. Pixel‐wise correlation analysis was applied to evaluate response to the stimuli in breast parenchyma and these results were compared to the all‐air control. The relative BOLD effect size was compared between two groups of volunteers scanned in different phases of the menstrual cycle. The optimal stimulus design was evaluated in five breast cancer patients.ResultsOf the four stimulus combinations tested, oxygen vs. 5% carbogen produced a response that was significantly stronger (P < 0.05) than air‐only breathing in volunteers. Subjects imaged during the follicular phase of their cycle when estrogen levels typically peak exhibited a significantly smaller BOLD response (P = 0.01). Results in malignant tissue were variable, with three out of five lesions exhibiting a diminished response to the gas stimulus.ConclusionOxygen vs. 5% carbogen is the most robust stimulus for inducing BOLD contrast, consistent with the opposing vasomotor effects of these two gases. Measurements may be confounded by background physiological fluctuations and menstrual cycle changes. J. Magn. Reson. Imaging 2016;44:335–345.
Highlights
Nineteen healthy female volunteers participated in this prospective study
We evaluated four stimulus paradigms, comprising carbogen and “carbogen-light” interleaved with either medical air or oxygen relative to an all-air control state
This investigation builds on previous work to optimize detection of vasomotor response in the breast via T2-based BOLD contrast,[15] as it accounts for normal physiological variations in each subject, which is a confounding factor in these types of analyses.[16]
Summary
Nineteen healthy female volunteers participated in this prospective study. Seventeen volunteers successfully completed the entire imaging protocol. Only one interleaved stimulus paradigm plus a baseline air-only scan was acquired due to a technical issue (failure of fat suppression) and time constraints. Volunteers did not report any adverse side effects as a result of the elevated CO2 concentration when breathing 2% or 5% carbogen in 2-minute blocks interleaved with either medical air or oxygen. No statistically significant change in respiratory (P 5 0.66, n 5 9; P 5 0.12, n 5 10) or cardiac rate (P 5 0.15, n 5 9; P 5 0.58, n 5 10) was observed during 5% carbogen breathing compared to air or oxygen breathing, respectivel
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