Respiratory self-gated 3D UTE for lung imaging in small animal MRI.
To investigate retrospective respiratory gating of three-dimensional ultrashort echo time (3D UTE) lung acquisition in free-breathing rats using k-space center self gating signal (DC-SG) and 3D image-based SG (3D-Img-SG).



Seven rats were investigated with a quasi-random 3D UTE protocol. Low-resolution time-resolved sliding-window images were reconstructed with a 3D golden-angle radial sparse parallel (GRASP) reconstruction to extract a 3D-Img-SG signal, whereas DC-SG was extracted from the center of k-space. Both signals were sorted into 10 respiratory bins. Signal-to-noise ratio (SNR) and normalized signal intensity (NSI) in lung parenchyma, image sharpness, and lung volume changes were studied in the resulting images to show feasibility of the method. An algorithm for bulk movement identification and removal was implemented.



Three-dimensional Img-SG allows reconstruction of different respiratory stages in all acquired datasets, showing clear differences in diaphragm position and significantly different lung volumes, SNR, and NSI in lung parenchyma. Improved sharpness in expiration images was observed compared to ungated images. DC-SG did not result in clear different diaphragm position in all cases. Bulk motion removal improved final image sharpness.



Low-resolution 3D GRASP reconstruction allowed for extraction of an effective gating signal for 3D-Img-SG. The DC-SG method did not work in cases for which respiratory frequencies were inconsistent. Magn Reson Med 78:739-745, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
Core Facility Small Animal MRI, Ulm University, Ulm, Germany.
Marta
M
Tibiletti
Boehringer Ingelheim Pharma GmbH & Co. KG, Target Discovery Research, In-Vivo Imaging Laboratory, Biberach an der Riss, Germany.
Andrea
A
Bianchi
Department of Neuroradiology, University Hospital Hamburg-Eppendorf, Hamburg, Germany.
Åsmund
Å
Kjørstad
Department of Internal Medicine II, Ulm University, Ulm, Germany.
Stefan
S
Wundrak
Boehringer Ingelheim Pharma GmbH & Co. KG, Target Discovery Research, In-Vivo Imaging Laboratory, Biberach an der Riss, Germany.
Detlef
D
Stiller
Core Facility Small Animal MRI, Ulm University, Ulm, Germany.|Department of Internal Medicine II, Ulm University, Ulm, Germany.
Volker
V
Rasche
D000465:Algorithms; D000818:Animals; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008168:Lung / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D059629:Signal-To-Noise Ratio
UTE; image-based self-gating; lung imaging; self-gating; ultrashort echo time