Lung T

Area of Science:

• Magnetic Resonance Imaging
• Pulmonary Medicine
• Biophysics

Background:

• Accurate T2* mapping is crucial for assessing lung tissue characteristics.
• Conventional MRI sequences often struggle with the short T2* values found in lung tissue.
• Free-breathing acquisitions are desirable for patient comfort and to minimize motion artifacts.

Purpose of the Study:

• To develop and validate 3D ultrashort echo time (UTE) sequences with minimized echo time intervals (δTE).
• To enable accurate T2* mapping of lung parenchyma during free breathing.
• To improve the precision of T2* quantification in lung imaging.

Main Methods:

• Implementation of a novel four-echo UTE sequence with δTE < 0.5 ms.
• Monte Carlo simulations to optimize the number of echoes for accuracy and scan time.
• Phantom studies with known short T2* values (< 5 ms) for validation.
• Human imaging at 3T on 6 volunteers using mono-exponential and bi-exponential T2* fitting models.

Main Results:

• Simulations predicted over a 2-fold improvement in T2* accuracy with 10 echoes compared to standard six-echo UTE.
• Phantom validation showed up to three times greater accuracy compared to standard six-echo UTE.
• Successful free-breathing lung T2* mapping was achieved with 10 echoes.
• Average T2* values in human lungs were 1.62 ± 0.48 ms (mono-exponential) and 1.00 ± 0.53 ms (bi-exponential).

Conclusions:

• A novel UTE sequence with optimized δTE was successfully implemented and validated for short T2* phantoms.
• The sequence demonstrated efficacy in free-breathing human lung imaging.
• Bi-exponential T2* fitting in lung imaging may offer valuable insights into diseased lung states.