MRI of respiratory dynamics with 2D steady-state free-precession and 2D gradient echo sequences at 1.5 and 3 Tesla: an observer preference study

Abstract

To compare the image quality of dynamic lung MRI with variations of steady-state free-precession (SSFP) and gradient echo (GRE) cine techniques at 1.5 T and 3 T. Ventilated porcine lungs with simulated lesions inside a chest phantom and four healthy human subjects were assessed with SSFP (TR/TE=2.9/1.22 ms; 3 ima/s) and GRE sequences (TR/TE=2.34/0.96 ms; 8 ima/s) as baseline at 1.5 and 3 T. Modified SSFPs were performed with nine to ten images/s (parallel imaging factors 2 and 3). Image quality for representative structures and artifacts was ranked by three observers independently. At 1.5 T, standard SSFP achieved the best image quality with superior spatial resolution and signal, but equal temporal resolution to GRE. SSFP with improved temporal resolution was ranked second best. Further acceleration (PI factor 3) was of no benefit, but increased artifacts. At 3 T, GRE outranged SSFP imaging with high lesion signal intensity, while artifacts on SSFP images increased visibly. At 1.5 T, a modified SSFP with moderate parallel imaging (PI factor 2) was considered the best compromise of temporal and spatial resolution. At 3 T, GRE sequences remain the best choice for dynamic lung MRI.

Four-Dimensional Magnetic Resonance Imaging Using Axial Body Area as Respiratory Surrogate: Initial Patient Results

“…Notably, however, there was a large degree of intersubject variation in the tumor-to-tissue CNR of the 4D-MRI (range, 4.57-45.00; standard deviation 14.63). The tumor-to-tissue CNR may be affected by multiple factors, including histology and stage of the cancer, patient size, as well as characteristics of the MRI system (eg, scanner type, magnetic field strength [17] and the number of receiver coil elements, T2-weighting of the pulse sequence). Both 1.5-T and 3-T MR scanners were used in this study.…”

MRI of the lung (2/3). Why … when … how?

“…patient can keep a breath-hold for 20 s or perfect gating/triggering), a threshold size of 3-4 mm can be assumed for lung nodule detection with MRI [19, 20]. In comparison with CT, it might be even faster and more efficient to read lung MRI for pulmonary nodules, since they appear with bright signal against the dark background of the healthy lung tissue [21] (Fig. 2).…”

“…to analyse respiratory motion of the lung, diaphragm and relationships of tumours to chest wall boundaries. The technical advances described above for 2D + t MRI or 3D + t MRI with different variants of T1-weighted gradient echo or steady state free precession sequences have been applied for this purpose [68, 69]. One of the most important clinical applications will be radiotherapy planning for organs with respiration-correlated motion [70, 71].…”

“…While most sequences, in particular 3D gradient echo techniques, profit from a higher lesion-to-background contrast to a certain degree, artefacts may deteriorate the image quality of steady state gradient echo sequences [17, 21, 77]. Overall, the changes of image quality with transfer of the concept to 3 T are acceptable or even positive for most sequence types.…”

4D-Imaging of the Lung: Reproducibility of Lesion Size and Displacement on Helical CT, MRI, and Cone Beam CT in a Ventilated Ex Vivo System

“…Four-dimensional CT with multidetector-row systems and short acquisition times permits a temporal resolution down to 250 ms (13,14). MRI with fast sequences such as two-dimensional (2D) gradient echo (GRE) or 2D fast steady-state GRE allows for lung-motion imaging with a temporal resolution between 3 and 10 images per second (15). Four-dimensional MRI with time-resolved 3D GRE sequences allows a temporal resolution of 1 s (16,17).…”