title: Flow-weighted MRI of the lungs with the ECG-gated half-Fourier FSE technique: evaluation of the effect of the cardiac cycle.
abstract: We investigated temporal MR signal changes in the peripheral lung and proximal pulmonary vessels during the entire cardiac cycle in order to evaluate the characteristics of the diastolic-systolic subtraction method in the lung. In eight healthy volunteers free of lung diseases, changes in the MR signal during one breath-hold were investigated with the multiple ECG-triggered half-Fourier single-shot fast-spin echo (SS-FSE) technique. The signal intensity-time course curve in the lung showed that biphasic signals decreased 20% to 47% at systole and 5% to 33% at mid-diastole, measured against the maximum signals at late diastole. This signal decrease in the peripheral lung was correlated to that in the proximal pulmonary vessels during an entire cardiac cycle (r=0.667 to 1.000). The best visualization of the lung was obtained at late diastole, when the intra-vascular flow in the lung was expected to be stagnant. Compared with the late diastolic SS-FSE images, the late diastolic-systolic subtracted SS-FSE images improved the signal-to-noise ratio in the lung as well as the signal-intensity ratio of the peripheral lung to surrounding tissues. Although the flow-induced signal dephasing in the lung was completely unavoidable and its amount was unpredictable even at late diastole, the diastolic-systolic subtracted SS-FSE images showed the relative differences in flow alteration during the cardiac cycle between the images at diastole and those at systole. The main characteristic of diastolic-systolic subtracted SS-FSE was the enhancement of visibility of cardiac-dependent signal changes in the lung due to the alteration in pulsatile flow.
authors.affiliation: Department of Radiology, University of Occupational and Environmental Health, School of Medicine, 1-1 Iseigaoka, Yahatanishi, Kitakyushu 807-8555, Japan. satoshi@med.uoeh-u.ac.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kawanami
authors.forename: Katsumi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Mitsue
authors.initials: M
authors.lastname: Miyazaki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sugiura
authors.forename: Shuichiro
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Hajime
authors.initials: H
authors.lastname: Nakata
mesh_terms: D000328:Adult; D003971:Diastole / Q000502:physiology; D004562:Electrocardiography; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011652:Pulmonary Circulation / Q000502:physiology*; D011673:Pulsatile Flow; D013599:Systole / Q000502:physiology