A free-breathing non-contrast-enhanced pulmonary magnetic resonance angiography at 3 Tesla.
BACKGROUND
The breathhold contrast-enhanced three-dimensional magnetic resonance angiography (MRA) using T1-weighted gradient-echo imaging sequence is the standard technique for MRA of the thorax. However, this technique is not desirable for certain patients with respiratory insufficiency, serious renal impairment, or allergy to contrast agents. The objective of this study was to optimize and evaluate a non-contrast-enhanced free-breathing pulmonary MRA protocol at 3 Tesla.


METHODS
The time-of-flight protocol was based on a two-dimensional T1-weighted turbo field echo sequence with slice-selective inversion recovery and magnetization transfer preparation together with respiratory navigator gating, cardiac gating, and parallel imaging. Optimal values for time of inversion delay, flip angle and slice thickness were experimentally determined and used for all subjects.


RESULTS
Excellent pulmonary MRA images, in which the 7th order branches of pulmonary arteries could be reliably identified, were obtained in the 12 free-breathing healthy volunteers. TI of approximately 300 ms provides the best suppression of background thoracic and cardiac muscles and effective inflow enhancement. With increasing flip angle, the pulmonary vessels gradually brightened and exhibited optimal contrast at 20 degrees-30 degrees. The 2 mm slice thickness and 0.5 mm slice overlap is suitable for visualization of the peripheral pulmonary vessel.


CONCLUSIONS
The MRA protocol at 3 Tesla may have clinical significance for pulmonary vascular imaging in patients who are not available for contrast-enhanced 3D MRA and CT angiography examination or are unable to sustain a long breath-hold.
Yang
Jian
J
Medical Imaging Center, First Hospital, School of Medicine, Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China. yj1118@mail.xjtu.edu.cn
Wang
Wei
W
Wang
Ya-rong
YR
Niu
Gang
G
Jin
Chen-wang
CW
Wu
Ed Xuekui
EX
D000328:Adult; D000368:Aged; D003287:Contrast Media; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000033:anatomy & histology; D011652:Pulmonary Circulation / Q000502:physiology; D011667:Pulmonary Veins / Q000033:anatomy & histology; D055815:Young Adult
D003287:Contrast Media