SElf‐gated Non‐Contrast‐Enhanced FUnctional Lung imaging (SENCEFUL) using a quasi‐random fast low‐angle shot (FLASH) sequence and proton MRI

Abstract

Obtaining functional information on the human lung is of tremendous interest in the characterization of lung defects and pathologies. However, pulmonary ventilation and perfusion maps usually require contrast agents and the application of electrocardiogram (ECG) triggering and breath holds to generate datasets free of motion artifacts. This work demonstrates the possibility of obtaining highly resolved perfusion-weighted and ventilation-weighted images of the human lung using proton MRI and the SElf-gated Non-Contrast-Enhanced FUnctional Lung imaging (SENCEFUL) technique. The SENCEFUL technique utilizes a two-dimensional fast low-angle shot (FLASH) sequence with quasi-random sampling of phase-encoding (PE) steps for data acquisition. After every readout, a short additional acquisition of the non-phase-encoded direct current (DC) signal necessary for self-gating was added. By sorting the quasi-randomly acquired data according to respiratory and cardiac phase derived from the DC signal, datasets of representative respiratory and cardiac cycles could be accurately reconstructed. By application of the Fourier transform along the temporal dimension, functional maps (perfusion and ventilation) were obtained. These maps were compared with dynamic contrast-enhanced (DCE, perfusion) as well as standard Fourier decomposition (FD, ventilation) reference datasets. All datasets were additionally scored by two experienced radiologists to quantify image quality. In addition, one initial patient examination using SENCEFUL was performed. Functional images of healthy volunteers and a patient diagnosed with hypoplasia of the left pulmonary artery and left-sided pulmonary fibrosis were successfully obtained. Perfusion-weighted images corresponded well to DCE-MRI data; ventilation-weighted images offered a significantly better depiction of the lung periphery compared with standard FD. Furthermore, the SENCEFUL technique hints at a potential clinical relevance by successfully detecting a perfusion defect in the patient scan. It can be concluded that SENCEFUL enables highly resolved ventilation- and perfusion-weighted maps of the human lung to be obtained using proton MRI, and might be interesting for further clinical evaluation.

Respiratory self-gated 3DUTE for lung imaging in small animal MRI

“…Signal‐to‐noise ratio and NSI in lung parenchyma significantly differ between the various respiratory stages, reflecting the density changes expected due to lung inflation. This change in signal intensity could be exploited to extract functional information on local ventilation, as in previous 2D studies . Three‐dimensional UTE offers better SNR due to the extremely low TE and isotropic resolution, whereas the 2D method is restricted to thick coronal slices.…”

“…These can, for example, be used for the extraction of local ventilation, which can be derived from the difference in signal intensity in lung parenchyma between inspiration and expiration images. A similar approach has been used by Fischer et al for human acquisitions , as well as by Bianchi et al, who recently demonstrated the applicability of ventilation maps derived from SG 2D UTE images to evaluate the functional impairment in a rat model of emphysema .…”

Multistage three‐dimensional UTE lung imaging by image‐based self‐gating

“…The quasirandom (QR, Figure C) scheme has been suggested for 3D UTE by Hemberger et al and for Cartesian 3D FLASH by Fischer et al . It exploits the characteristics of a Niederreiter 2D quasi random sequence to generate a sequence of 2D‐tuples that fills 2D‐space more uniformly than uncorrelated random points .…”

Acute Pulmonary Artery Embolism Detected by Noncontrast Functional Lung Magnetic Resonance Imaging

“…FD-MRI was performed using the SElf-gated Non-Contrast-Enhanced FUnctional Lung (SENCEFUL) MRI approach, providing maps in sufficient spatial resolution and reconstruction of complete cardiac/respiratory cycles. 1 The acquisition of a slice with 1-cm thickness in the coronar plane takes ≈2 minutes. Data acquisition of the entire lung amounts to 15 to 20 slices, resulting in an acquisition time of 25 to 40 minutes.…”

“…SENCEFUL FD-MRI can be implemented in any commercially available MRI system as technical details of the sequence have been published. 1 Limitations of FD-MRI refer to the common MRI contraindications. Evaluation and development of SENCEFUL-MRI is part of a research protocol on functional lung MRI in the reporting department.…”