CMR-Analysis (including machine learning)

1356196 - Breath-Hold UTE Stack-of-Spirals Lung Water Volume Quantification at Rest and Physiological Exercise at 3T

Wednesday, January 25, 2023

Location: E-POSTER

Presenting Author(s)

SA

Salah Assana, MSc

Research Assistant
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States

Primary Author(s)

SA

Salah Assana, MSc

Research Assistant
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States

Co-Author(s)

SN

Shiro Nakamori, MD

Senior Lecturer
Mie University Hospital
Tsu, Mie, Japan
MM

Manuel A. Morales, PhD

Post-doc Research Fellow
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States
SB

Sophie Berg, RN

Research Nurse
Beth Israel Deaconess Medical Center, United States
SJ

Scott Johnson

MRI Tech
Beth Israel Deaconess Medical Center, United States
PP

Patrick Pierce, RT

MRI Tech
Beth Israel Deaconess Medical Center, Massachusetts, United States
BG

Beth Goddu, RT

MRI Tech
Beth Israel Deaconess Medical Center, United States
JR

Jennifer Rodriguez

Clinical Trials Specialist
Beth Israel Deaconess Medical Center
Boston, Massachusetts, United States
LN

Long H. Ngo, PhD

Associate Professor
Harvard Medical School
Boston, Massachusetts, United States
Warren J. Manning, MD

Professor of Medicine and Radiology
Harvard Medical School
Boston, Massachusetts, United States
RT

Richard Thompson, PhD

Professor of Biomedical Engineering
University of Alberta
Edmonton, Alberta, Canada
RN

Reza Nezafat, PhD

Professor
Harvard Medical School
Boston, Massachusetts, United States

Disclosure(s):

Warren J. Manning, MD: No relevant disclosure to display

Reza Nezafat, PhD: No financial relationships to disclose

Background: Pulmonary edema is the accumulation of extravascular water in the pulmonary interstitium and alveoli. It is present in many patients with cardiovascular disease at rest or post exercise. There is a growing interest in evaluation of pulmonary edema during CMR exams. Initial studies quantified lung water using a gradient-echo imaging sequence with short TE and small flip angle at low magnetic field. Recently, ultra-short echo time (UTE) sequences have been introduced to reduce the effect of local magnetic field inhomogeneity within the lung¹. In this study, we sought to a) investigate the repeatability & reproducibility of lung water imaging at 3T using a 10 second breath-hold UTE stack-of-spiral sequence, and b) demonstrate the feasibility of quantifying lung water changes in response to physiological exercise.

Methods: Fourteen healthy subjects (2 males; 26±6 years) were enrolled in our study. All imaging was performed in a 3T scanner using 18-channel cardiac coil with the protocol shown in Fig 1A. All scans had identical imaging parameters: FoV 600mm, slice 2.5mm, flip angle 1⁰, TR 2.6ms, TE 0.05ms, spiral interleaves 264, scan time≈15 sec. Images were post-processed using an in-house software which first normalized the voxels in the lung by the surrounding tissue to compute lung water density (LWD). Then, an iterative 3D region-growing algorithm segmented the lung parenchyma and excluded large conduit vessels². Finally, the voxels were multiplied by their LWD and summed to quantitatively measure extravascular lung water volume. The repeatability & reproducibility of MRI-derived water volume were measured using coefficient of variation (CV) and inter-correlation coefficient (ICC). The changes in lung water and volume parameters due to exercise was quantified at different time-points (Fig 2).

Results: Imaging acquisition was completed in all subjects; 38 of the 434 UTE imaging datasets (18%) were discarded due to improper breath-holding which resulted in the failure of the semi-automatic lung segmentation. Fig 1B shows lung MRI images collected using breath-hold UTE stack-of-spirals and segmented lung area used to calculate lung water. Table 1 shows CV & ICC for all measured parameters, demonstrating good-excellent repeatability & reproducibility. The CMR-derived lung water increased immediately post-exercise (0.56±0.08L to 0.72±0.17L) and then gradually decreased over time (Fig 2A), however, we observed a heterogenous response to exercise among subjects (Fig 2B).

Conclusion: The 3D UTE stack-of-spirals yields repeatable & reproducible measures of lung water parameters at 3T. The pilot exercise study demonstrated feasibility of measuring lung water changes with exercise; however, heterogenous response to exercise was observed that may either reflect underlying physiology of changes in lung water or technical challenges associated with imaging post-exercise. Further studies are warranted to rigorously investigate the exercise response.