Abstract
In this study, we developed a novel photoacoustic imaging technique based on poly (ethyleneglycol)-coated (PEGylated) gold nanorods (PEG-GNRs) (as the contrast agent) combined with traditional Chinese medicine (TCM) acupuncture (as the auxiliary method) for quantitatively monitoring contrast enhancement in the vasculature of a mouse brain in vivo. This study takes advantage of the strong near-infrared absorption (peak at [Formula: see text][Formula: see text]nm) of GNRs and the ability to adjust the hemodynamics of acupuncture. Experimental results show that photoacoustic tomography (PAT) successfully reveals the optical absorption variation of the vasculature of the mouse brain in response to intravenous administration of GNRs and acupuncture at the Zusanli acupoint (ST36) both individually and combined. The quantitative measurement of contrast enhancement indicates that the composite contrast agents (integration of acupuncture and GNRs) would greatly enhance the photoacoustic imaging contrast. The quantitative results also have the potential to estimate the local concentration of GNRs and even the real-time effects of acupuncture.
Highlights
IntroductionPhotoacoustic tomography (PAT), an emerging biomedical imaging technique, has developed greatly in recent decades.[1,2,3,4,5,6,7] This in vivo brain functional imaging technique has the following unique advantages: (1) it is an noninvasive imaging mode which is conducted in accordance with ethical principles; (2) animals can maintain normal physiological activity during imaging; (3) it has adequate spatial resolution (up to tens of m), temporary resolution (up to tens of ms) and limited depth of penetration (up to several mm, with intact scalp) in monitoring the brain; (4) it provides high-resolution functional information, such as hemoglobin and blood oxygenation levels relevant to describing physiology and pathology.[6,8,9,10,11,12,13,14,15,16,17,18,19,20] PAT of small animal brain has successfully been implemented.[3,8,9,10,11,12,13] In these studies, PAT was used for mapping the microvascular network of a mouse brain with the hemodynamic activities when the scalp and skull were intact.[8,10,11,12,13] Resting-state functional connectivity (RSFC) has been studied in the mouse brain using PAT.[8,11] PAT was able to detect connectivity between di®erent functional regions and even between sub-regions.[8,10] Recently, several research demonstrated that the neonatal brain imaging through fontanel using photoacoustic technique is feasible.[14,15,16,17,18,19,20] Even though the skull and scalp of any small animal is thin, the penetration depth is limited.[17,20] In the situation where a limited detection depth is certain, or an endogenous contrast is not available, an exogenous contrast agent can be utilized
1941004-2 we developed a method based on combined acupuncture and Gold nanorods (GNRs), in which GNRs were injected intravenously and the concentration of hemoglobin in the cerebral cortex of the mice was increased by acupuncture at the Zusanli (ST36) acupoint
The major blood vessels shown in the Photoacoustic tomography (PAT) image (Fig. 3(a)) were marked by anatomical landmarks, including the rostral rhinal vein (RRV; the left RRV and right RRV was marked by No 1 and No 2 ellipses in red, respectively), the superior sagittal sinus (SSS, between the left and right hemispheres), the transverse sinus (TS, between the colliculi and cerebellum areas; the left TS and right TS was marked by No 3 and No 4 ellipses in red, respectively), the left veins (LVs), and the right veins (RVs)
Summary
Photoacoustic tomography (PAT), an emerging biomedical imaging technique, has developed greatly in recent decades.[1,2,3,4,5,6,7] This in vivo brain functional imaging technique has the following unique advantages: (1) it is an noninvasive imaging mode which is conducted in accordance with ethical principles; (2) animals can maintain normal physiological activity during imaging; (3) it has adequate spatial resolution (up to tens of m), temporary resolution (up to tens of ms) and limited depth of penetration (up to several mm, with intact scalp) in monitoring the brain; (4) it provides high-resolution functional information, such as hemoglobin and blood oxygenation levels relevant to describing physiology and pathology.[6,8,9,10,11,12,13,14,15,16,17,18,19,20] PAT of small animal brain has successfully been implemented.[3,8,9,10,11,12,13] In these studies, PAT was used for mapping the microvascular network of a mouse brain with the hemodynamic activities when the scalp and skull were intact.[8,10,11,12,13] Resting-state functional connectivity (RSFC) has been studied in the mouse brain using PAT.[8,11] PAT was able to detect connectivity between di®erent functional regions and even between sub-regions.[8,10] Recently, several research demonstrated that the neonatal brain imaging through fontanel using photoacoustic technique is feasible.[14,15,16,17,18,19,20] Even though the skull and scalp of any small animal is thin, the penetration depth is limited.[17,20] In the situation where a limited detection depth is certain, or an endogenous contrast is not available, an exogenous contrast agent can be utilized. Known as exogenous contrast agents, can be used to enhance images in medical scans of the tissues or organs. They can potentially improve the image resolutions.[4]
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