Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2010 Oct;64(4):995-1004.
doi: 10.1002/mrm.22411.

Contrast-enhanced in vivo magnetic resonance microscopy of the mouse brain enabled by noninvasive opening of the blood-brain barrier with ultrasound

Gabriel P Howles  1 , Kristin F Bing, Yi Qi, Stephen J Rosenzweig, Kathryn R Nightingale, G Allan Johnson
Affiliations

Contrast-enhanced in vivo magnetic resonance microscopy of the mouse brain enabled by noninvasive opening of the blood-brain barrier with ultrasound

Gabriel P Howles et al. Magn Reson Med. 2010 Oct.

Abstract

The use of contrast agents for neuroimaging is limited by the blood-brain barrier (BBB), which restricts entry into the brain. To administer imaging agents to the brain of rats, intracarotid infusions of hypertonic mannitol have been used to open the BBB. However, this technically challenging approach is invasive, opens only a limited region of the BBB, and is difficult to extend to mice. In this work, the BBB was opened in mice, using unfocused ultrasound combined with an injection of microbubbles. This technique has several notable features: it (a) can be performed transcranially in mice; (b) takes only 3 min and uses only commercially available components; (c) opens the BBB throughout the brain; (d) causes no observed histologic damage or changes in behavior (with peak-negative acoustic pressures of 0.36 MPa); and (e) allows recovery of the BBB within 4 h. Using this technique, Gadopentetate Dimeglumine (Gd-DTPA) was administered to the mouse brain parenchyma, thereby shortening T(1) and enabling the acquisition of high-resolution (52 × 52 × 100 micrometers(3)) images in 51 min in vivo. By enabling the administration of both existing anatomic contrast agents and the newer molecular/sensing contrast agents, this technique may be useful for the study of mouse models of neurologic function and pathology with MRI.

PubMed Disclaimer

Figures

FIG. 1
FIG. 1
a: The BOMUS setup. b: Experimental time line.
FIG. 2
FIG. 2
The acoustic output of the ultrasound system was characterized in water using a hydrophone. a: The test pulse was a 10-cycle sinusoid (PRF = 10 Hz). An input voltage of 167 mVpp produced a peak negative pressure of 0.36 MPa. b: The lateral profile of the beam was measured at the transducers natural focus (58 mm).
FIG. 3
FIG. 3
T1-weighted SPGR images (high-throughput protocol) demonstrate that Gd-DTPA enhances body tissues but is excluded from the brain by the intact BBB. Treatment with either ultrasound or microbubbles alone does not make the BBB permeable to Gd-DTPA. However, co-administration of ultrasound and microbubbles globally opens the BBB, allowing the Gd-DTPA to enhance the brain.
FIG. 4
FIG. 4
Time course of Gd-DTPA enhancement in the brain and muscle after BOMUS. T1-weighted images (high-throughput protocol) were acquired prior to Gd-DTPA and BOMUS (plotted at time 0), serially after BOMUS, and 27 hours after BOMUS. ROIs were placed in the jaw muscle, lateral ventricle, cerebral cortex, and basal ganglia to measure the mean signal intensity. Plot shows mean ± standard deviation (n = 6 except at 27 hours for which n = 1).
FIG. 5
FIG. 5
The duration of BBB disruption was demonstrated by assaying BBB permeability at several times after BOMUS. A separate animal was used to assay each time point. Signal measurements were made in several ROIs from T1-weighted images (high-throughput protocol). To account for inter-animal variability, the muscle signal was used to normalize the intracranial signals: log2 (tissue signal/muscle signal) is plotted along the y-axis. For comparison, data from an untreated control animal is shown at time < 0.
FIG. 6
FIG. 6
a: The mean number of red blood cell extravasations seen in each histology slide of the brain is shown for acoustic pressures of 0.36 MPa (n = 3), 0.52 MPa (n = 4), and 5.0 MPa (n = 1). Error bars show standard error. b: An example of severe red blood cell extravasation from the brain exposed to 5.0 MPa is shown.
FIG. 7
FIG. 7
Behavioral testing was performed before anesthesia and 3 and 24 hours after recovery from anesthesia. The average behavior (± SEM) score for control (n = 3) and BOMUS (0.8 MPa) treated (n = 8) animals is shown. Relative to the pre-anesthesia baseline, all animals show a decrease in behavior score 3 hours after anesthesia, but they largely recover by the next day. At each time point, no difference was seen between the two groups, indicating that BOMUS did not measurably affect animal behavior.
FIG. 8
FIG. 8
T1 values were estimated from three ROIs in control and treated mice (1 mouse per group). In the control animal receiving neither Gd-DTPA nor BOMUS, T1 values were long in the cortex (2.08 s), basal ganglia (1.97 s), and muscle (2.01 s). The animal given only Gd-DTPA had somewhat shortened T1 values in the cortex (1.53 s) and basal ganglia (1.56 s), and dramatically shortened T1 in the muscle (0.71 s). In the animal treated with both BOMUS, Gd-DTPA not only shortened the T1 of the muscle (0.80 s), but also crossed the BBB and shortened T1 in the cortex (0.50 s) and basal ganglia (0.50 s).
FIG. 9
FIG. 9
High-resolution (52 × 52 × 100 µm3) SPGR images of the mouse brain acquired in vivo in 51 minutes. The control mouse receiving no contrast agent and the mouse receiving only Gd-DPTA have relatively low signal. The animal receiving Gd-DTPA along with BOMUS (microbubbles+ultrasound) shows an increase in SNR of 90% and 63% over the other two. SNR measurements were made in left anterior cortex. For each scan TR = 25ms and FA was adjusted to maximize signal in the anterior cerebral cortex (15, 15, and 25 degrees, respectively).
FIG. 10
FIG. 10
Minimum intensity projections of a 600-µm axial slab from SPGR images (high-resolution protocol) from BOMUS-treated animals given high doses of Gd-DTPA. BOMUS allows the Gd-DTPA to enhance the parenchyma of the brain, but high concentration of Gd-DTPA in the bloodstream causes susceptibility-induced loss of signal from the blood and perivascular tissue. This allows the delineation of cortical vessels (running perpendicular to the cortical surface). When the dose of Gd-DTPA is increased to 9.5 mmol/kg, this effect is exaggerated.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Johnson GA, Cofer GP, Gewalt SL, Hedlund LW. Morphologic phenotyping with MR microscopy: The visible mouse. Radiology. 2002;222(3):789–793. - PubMed
    1. Johnson GA, Ali-Sharief A, Badea A, Brandenburg J, Cofer G, Fubara B, Gewalt S, Hedlund LW, Upchurch L. High-throughput morphologic phenotyping of the mouse brain with magnetic resonance histology. Neuroimage. 2007;37(1):82–89. - PMC - PubMed
    1. Muldoon LL, Soussain C, Jahnke K, Johanson C, Siegal T, Smith QR, Hall WA, Hynynen K, Senter PD, Peereboom DM, Neuwelt EA. Chemotherapy delivery issues in central nervous system malignancy: A reality check. Journal of Clinical Oncology. 2007;25(16):2295–2305. - PubMed
    1. Doolittle ND, Peereboom DM, Christoforidis GA, Hall WA, Palmieri D, Brock PR, Campbell K, Dickey DT, Muldoon LL, O'Neill BP, Peterson DR, Pollock B, Soussain C, Smith Q, Tyson RM, Neuwelt EA. Delivery of chemotherapy and antibodies across the blood-brain barrier and the role of chemoprotection, in primary and metastatic brain tumors: report of the eleventh annual blood-brain barrier consortium meeting. Journal of Neuro-Oncology. 2007;81(1):81–91. - PubMed
    1. Kroll RA, Neuwelt EA. Outwitting the blood-brain barrier for therapeutic purposes: Osmotic opening and other means. Neurosurgery. 1998;42(5):1083–1099. - PubMed

Publication types