Unenhanced dynamic MR angiography: high spatial and temporal resolution by using true FISP-based spin tagging with alternating radiofrequency

Abstract

Purpose: To present an unenhanced four-dimensional time-resolved dynamic magnetic resonance (MR) angiography technique with true fast imaging with steady-state precession-based spin tagging with alternating radiofrequency (STAR), also called TrueSTAR.

Materials and methods: This study received Institutional Review Board approval and was HIPAA compliant. Informed consent was obtained from all study subjects. In eight healthy volunteers, the spatial and temporal resolution of the TrueSTAR technique were optimized. In another six healthy volunteers, the contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of the TrueSTAR dynamic MR angiography images were compared with those acquired by using a standard Look-Locker echo-planar technique by using the Wilcoxon signed rank test. Finally, one patient with an arteriovenous malformation (AVM) was studied by using this technique.

Results: The SNR and CNR of the TrueSTAR dynamic MR angiography images were 29% and 39% higher, respectively, compared with those acquired by using a standard Look-Locker echo-planar imaging sequence (both P = .028). In the AVM patient, TrueSTAR dynamic MR angiography delineated the dynamic course of labeled blood flowing through feeding arteries into the nidus and draining veins.

Conclusion: The results suggest that TrueSTAR is a promising unenhanced dynamic MR angiography technique for clinical evaluation of cerebrovascular disorders such as AVM, steno-occlusive disease, and aneurysm.

Conflict of interest statement

Authors stated no financial relationship to disclose.

Figures

Figure 1:

Pulse sequence diagram of TrueSTAR with flow-sensitive alternating inversion recovery for spin labeling. Layout of gradient and readout is shown in inset. α = flip angle, RF = radiofrequency, TI = inversion time.

Figure 2a:

Mean dynamic MR angiography time courses from arterial regions of interest acquired with (a) three different inversion band thicknesses and (b, c) three different flip angles normalized to equilibrium blood signal intensity (M0), with data in c further scaled by the sine of the flip angle (a).

Figure 2b:

Mean dynamic MR angiography time courses from arterial regions of interest acquired with (a) three different inversion band thicknesses and (b, c) three different flip angles normalized to equilibrium blood signal intensity (M0), with data in c further scaled by the sine of the flip angle (a).

Figure 2c:

Mean dynamic MR angiography time courses from arterial regions of interest acquired with (a) three different inversion band thicknesses and (b, c) three different flip angles normalized to equilibrium blood signal intensity (M0), with data in c further scaled by the sine of the flip angle (a).

Figure 3a:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images acquired with 3D TrueSTAR from a representative subject. Note the anatomic details of dynamic courses for blood originating from internal carotid and basilar arteries as it fills the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) sequentially. Small branches of the middle cerebral artery and anterior and posterior cerebral arteries can also be seen in later phases of dynamic MR angiography. Note signal intensity in sagittal sinus owing to labeled venous blood superior to imaging sections. ms = milliseconds.

Figure 3b:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images acquired with 3D TrueSTAR from a representative subject. Note the anatomic details of dynamic courses for blood originating from internal carotid and basilar arteries as it fills the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) sequentially. Small branches of the middle cerebral artery and anterior and posterior cerebral arteries can also be seen in later phases of dynamic MR angiography. Note signal intensity in sagittal sinus owing to labeled venous blood superior to imaging sections. ms = milliseconds.

Figure 3c:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images acquired with 3D TrueSTAR from a representative subject. Note the anatomic details of dynamic courses for blood originating from internal carotid and basilar arteries as it fills the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) sequentially. Small branches of the middle cerebral artery and anterior and posterior cerebral arteries can also be seen in later phases of dynamic MR angiography. Note signal intensity in sagittal sinus owing to labeled venous blood superior to imaging sections. ms = milliseconds.

Figure 4a:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images acquired with 3D TrueSTAR by using a pulse-trigger in the same subject shown in Figure 3. Note improved sharpness. ACA = anterior cerebral artery, MCA = middle cerebral artery, ms = milliseconds, PCA = posterior cerebral artery.

Figure 4b:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images acquired with 3D TrueSTAR by using a pulse-trigger in the same subject shown in Figure 3. Note improved sharpness. ACA = anterior cerebral artery, MCA = middle cerebral artery, ms = milliseconds, PCA = posterior cerebral artery.

Figure 4c:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images acquired with 3D TrueSTAR by using a pulse-trigger in the same subject shown in Figure 3. Note improved sharpness. ACA = anterior cerebral artery, MCA = middle cerebral artery, ms = milliseconds, PCA = posterior cerebral artery.

Figure 5a:

(a) Bar graph shows comparison of SNR efficiencies (SNR divided by square root of acquisition time) of dynamic MR angiography images between two-dimensional TrueSTAR and Look-Locker echo-planar imaging (LL-EPI) across three different flip angles. (b) Collapsed MIP images from a representative subject show ghost artifact in M1 segment of middle cerebral artery (arrow) on Look-Locker echo-planar image and improved visualization of anterior cerebral artery (arrowhead) on TrueSTAR image. SNR efficiency of 3D TrueSTAR is 32.82 ± 2.65.

Figure 5b:

(a) Bar graph shows comparison of SNR efficiencies (SNR divided by square root of acquisition time) of dynamic MR angiography images between two-dimensional TrueSTAR and Look-Locker echo-planar imaging (LL-EPI) across three different flip angles. (b) Collapsed MIP images from a representative subject show ghost artifact in M1 segment of middle cerebral artery (arrow) on Look-Locker echo-planar image and improved visualization of anterior cerebral artery (arrowhead) on TrueSTAR image. SNR efficiency of 3D TrueSTAR is 32.82 ± 2.65.

Figure 6a:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images of a 29-year-old man with AVM and (d) the associated MIP image of time-of-flight MR angiography. Arrowheads = feeding arteries. Arrows = nidus. Curved arrows = draining veins.

Figure 6b:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images of a 29-year-old man with AVM and (d) the associated MIP image of time-of-flight MR angiography. Arrowheads = feeding arteries. Arrows = nidus. Curved arrows = draining veins.

Figure 6c:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images of a 29-year-old man with AVM and (d) the associated MIP image of time-of-flight MR angiography. Arrowheads = feeding arteries. Arrows = nidus. Curved arrows = draining veins.

Figure 6d:

(a) Axial, (b) coronal, and (c) sagittal dynamic MR angiography MIP images of a 29-year-old man with AVM and (d) the associated MIP image of time-of-flight MR angiography. Arrowheads = feeding arteries. Arrows = nidus. Curved arrows = draining veins.