Traditional Posters: Body Imaging

William Dominguez-Viqueira^1,2, Matthew S. Fox, ^1,3, Giles E. Santyr<sup>2,4

1</sup>Imaging Laboratories, Robarts Research Institute, London, Ontario, Canada; ²Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada; ³Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada; ⁴Department of Medical Imaging, University of Western Ontario, London, Ontario, Canada

The maximum SNR in Hyperpolarized Noble Gas (HNG) MR imaging of rodent lung is expected to be at high fields (>3T). However, SNR improvements of up to 300% have been demonstrated in rat lung at 73.5mT using Litz-wire coils. In this work the SNR for HNG MRI of rat lung was investigated theoretically and in vivo, using multi-turn Litz-wire coils at 73.5mT and compared to images obtained at 3T using ¹²⁹Xe and ³He. The use of Litz-wire coils significantly reduces the advantage (from factor ten to a factor of two) of using high fields for HNG imaging of rat lungs.

2561. Quantitative Assessment of Alveolar Recruitment with Hyperpolarized Gas MRI

Kiarash Emami¹, Masaru Ishii², Stephen J. Kadlecek¹, Jianliang Zhu³, Stephen Pickup¹, Yi Xin¹, Puttisarn Mongkolwisetwara¹, Harrilla Profka¹, Rahim R. Rizi<sup>1

1</sup>Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States; ²Department of Otolaryngology, Johns Hopkins University, Baltimore, MD, United States; ³Department of Surgery, University of Pennsylvania, Philadelphia, PA, United States

This study evaluates the preliminary use of HP gas diffusion MRI to assess alveolar recruitment dynamics in a healthy rat model. After a period of ventilation at zero positive end-expiratory pressure (PEEP), recruitment was studied at elevated PEEP and constant tidal volume. After recruitment, it was found that regional ADC values initially diminished and consistently recovered with the removal of elevated PEEP. It is therefore proposed that before recruitment, accumulated alveolar collapse causes the over-extension of active alveoli (high ADC); after recruitment, the fixed tidal volume is shared by the greater number of recruited alveoli (corresponding to decreased ADC).

2562. Alveolar Gas Diffusion MRI as a Function of Pulmonary Pressure

Kiarash Emami¹, Stephen J. Kadlecek¹, Yi Xin¹, Puttisarn Mongkolwisetwara¹, Harrilla Profka¹, Stephen Pickup¹, Jianliang Zhu², Masaru Ishii³, Rahim R. Rizi<sup>1

1</sup>Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States; ²Department of Surgery, University of Pennsylvania, Philadelphia, PA, United States; ³Department of Otolaryngology, Johns Hopkins University, Baltimore, MD, United States

In this work, we evaluate the use of HP gas ADC measurements to assess the positive end-expiratory pressure (PEEP) dependence of alveolar recruitment in a healthy rat model. By maintaining a constant tidal volume, ADC can be decoupled from volume dependence and thus considered a measurement of average alveolar size. In general, it was found that higher ADC values correspond with large PEEP. Additionally, at any given PEEP, the end-inhale ADC value is larger than the end-exhale ADC value, supporting the theory that in low-recruitment conditions (large numbers of collapsed alveoli), active alveoli are over-inflated (yielding high ADC).

2563. Quantitative Assessment of Idiopathic Pulmonary Fibrosis with Hyperpolarized Gas MRI

Michael J. Stephen¹, Kiarash Emami², John M. Woodburn², Elaine Chia², Stephen J. Kadlecek², Jianliang Zhu³, Masaru Ishii⁴, Milton Rossman¹, Benjamin Pullinger², Stephen Pickup², Rahim R. Rizi<sup>2

1</sup>Department of Pulmonary and Critical Care, University of Pennsylvania, Philadelphia, PA, United States; ²Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States; ³Department of Surgery, VA Medical Center, Philadelphia, PA, United States; ⁴Department of Otolaryngology, Johns Hopkins University, Baltimore, MD, United States

This study demonstrates the first attempt to use hyperpolarized gas MR images of lung ventilation and apparent diffusion (ADC) in an animal model of interstitial lung disease. The efficacy of hyperpolarized ³He MRI metrics in assessing idiopathic pulmonary fibrosis (IPF) was evaluated in a bleomycin rat model. Results showed that fractional ventilation 3 weeks after bleomycin administration was significantly lower than in the control animals, and ADC measurements followed similar trends. Hyperpolarized gas MRI is a promising diagnostic for IPF and an improvement over current diagnostics in its regional sensitivity and benignancy.

2564. Regional Pulmonary Pressure Over Volume Curves of the Rat Lung Measured by Polarized 3He Magnetic Resonance Imaging