Feasibility of free breathing Lung MRI for Radiotherapy using non-Cartesian k-space acquisition schemes

Abstract

Objective:To test a free-breathing MRI protocol for anatomical and functional assessment during lung cancer radiotherapy by assessing two non-Cartesian acquisition schemes based on T 1 weighted 3D gradient recall echo sequence: (i) stack-of stars (StarVIBE) and (ii) spiral (SpiralVIBE) trajectories. Methods:MR images on five healthy volunteers were acquired on a wide bore 3T scanner (MAGNETOM Skyra, Siemens Healthcare, Erlangen, Germany). Anatomical image quality was assessed on: (1) free breathing (StarVIBE), (2) the standard clinical sequence (volumetric interpolated breath-hold examination, VIBE) acquired in a 20 second (s) compliant breath-hold and (3) 20 s non-compliant breath-hold. For functional assessment, StarVIBE and the current standard breath-hold time-resolved angiography with stochastic trajectories (TWIST) sequence were run as multiphase acquisitions to replicate dynamic contrast enhancement (DCE) in one healthy volunteer. The potential application of the SpiralVIBE sequence for lung parenchymal imaging was assessed on one healthy volunteer. Ten patients with lung cancer were subsequently imaged with the StarVIBE and SpiralVIBE sequences for anatomical and structural assessment. For functional assessment, free-breathing StarVIBE DCE protocol was compared with breath-hold TWIST sequences on four prior lung cancer patients with similar tumour locations. Image quality was evaluated independently and blinded to sequence information by an experienced thoracic radiologist. Results:For anatomical assessment, the compliant breath-hold VIBE sequence was better than free-breathing StarVIBE. However, in the presence of a non-compliant breath-hold, StarVIBE was superior. For functional assessment, StarVIBE outperformed the standard sequence and was shown to provide robust DCE data in the presence of motion. The ultrashort echo of the SpiralVIBE sequence enabled visualisation of lung parenchyma. Conclusion:The two non-Cartesian acquisition sequences, StarVIBE and SpiralVIBE, provide a free-breathing imaging protocol of the lung with sufficient image quality to permit anatomical, structural and functional assessment during radiotherapy. Advances in knowledge:Novel application of non-Cartesian MRI sequences for lung cancer imaging for radiotherapy. Illustration of SpiralVIBE UTE sequence as a promising sequence for lung structural imaging during lung radiotherapy. To test a free-breathing MRI protocol for anatomical and functional assessment during lung cancer radiotherapy by assessing two non-Cartesian acquisition schemes based on T 1 weighted 3D gradient recall echo sequence: (i) stack-of stars (StarVIBE) and (ii) spiral (SpiralVIBE) trajectories. Methods: MR images on five healthy volunteers were acquired on a wide bore 3T scanner (MAGNETOM Skyra, Siemens Healthcare, Erlangen, Germany). Anatomical image quality was assessed on: (1) free breathing (StarVIBE), (2) the standard clinical sequence (volumetric interpolated breath-hold examination, VIBE) acquired in a 20 second (s) compliant breath-hold and ...

3D ultrashort echo time MRI of the lung using stack‐of‐spirals and spherical k‐Space coverages: Evaluation in healthy volunteers and parenchymal diseases

“…3D-USV using a stack-of-spirals has been recently described and applied in patients with lung cancer. 12 It could be noticed that in the previous study by Du et al, 16 a higher signal-tonoise ratio was obtained using 2D spiral trajectories than with 2D radial trajectories in static organs such as the brain or bones, which was ascribed to a more time-efficient coverage of the k-space. On the contrary, by comparing 3D-USV with PETRA, apparent signal and contrast ratios of 3D-USV were found lower in healthy volunteers than that obtained using a radial spherical coverage of k-space.…”

“…The two main procedures consist of acquiring k ‐space either radially into a sphere or into a cylinder using stack‐of‐discs, although several variants exist. 3D‐USV using a stack‐of‐spirals has been recently described and applied in patients with lung cancer . It could be noticed that in the previous study by Du et al, a higher signal‐to‐noise ratio was obtained using 2D spiral trajectories than with 2D radial trajectories in static organs such as the brain or bones, which was ascribed to a more time‐efficient coverage of the k ‐space.…”

“…Although all 3D sequences seek to decrease the echo time down to the microsecond, variable schemes are used to sample the k ‐space. The two main k ‐space variants consist in acquiring the k ‐space either radially into a sphere or into a cylinder using stack‐of‐discs such as stack‐of‐stars or stack‐of‐spirals . In our institution, a novel prototype dedicated to 3D‐UTE imaging using VIBE (volume interpolated breath‐hold examination) and stack‐of‐spirals (3D‐USV) has been released for testing.…”

“…The two main k-space variants consist in acquiring the k-space either radially into a sphere 4 or into a cylinder using stack-of-discs such as stack-of-stars 5 or stackof-spirals. 12 In our institution, a novel prototype dedicated to 3D-UTE imaging using VIBE (volume interpolated breath-hold examination) and stack-of-spirals (3D-USV) has been released for testing. Although a few reports exist regarding the rationale and the feasibility of 3D-USV for lung MRI, 12,13 a more exhaustive assessment might be beneficial.…”

Simultaneous Evaluation of Lung Anatomy and Ventilation Using 4D Respiratory‐Motion‐Resolved Ultrashort Echo Time Sparse MRI

“…However, this acquisition scheme significantly reduces scan efficiencies compared with standard radial sequences, since only half of the data can be acquired within a given scan time. It would be interesting to explore a stack‐of‐spirals acquisition scheme for lung imaging as shown previously . By acquiring different image partitions with varying TEs, this sequence is expected to achieve ultrashort echo time contrast and improved imaging efficiency simultaneously.…”