Room 155 EF

10:30 - 12:30

Moderators:

Giles E. Santyr, Jim M. Wild

Rosa Tamara Branca¹, Le Zhang², Christian White¹, and Ting He^1
1Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, ²Material Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States

In vivo temperature measurement of fatty tissues by proton MR is notoriously challenging. Here we demonstrate in vivo temperature measurement by HP Xenon MR. We also show the possibility to directly measure in real time thermogenesis by brown adipose tissue, a tissue which has recently become the focus of much research attention due to its implication in the development of human obesity and type 2 diabetes.

Matthew S. Freeman¹, Zackary I. Cleveland², Yi Qi², and Bastiaan Driehuys^1,2
1Medical Physics Graduate Program, Duke University, Durham, NC, United States, ²Department of Radiology, Duke University, Durham, NC, United States

Hyperpolarized 129Xe provides a unique means of probing gas exchange, being soluble in tissues and displaying a large in vivo chemical shift range. However, mice do not typically display a unique RBC resonance, as rats and humans do. For the first time, transgenic mice expressing for human hemoglobin display two dissolved-phase NMR peaks at 198 and 220 ppm, almost identical to the interstitial tissue and RBC peaks seen in humans. This enables visualization of pulmonary gas-exchange not previously possible in mice, providing global and regional physiological information about gas transit to the RBCs in mouse models of disease and injury.

General Leung¹, Graham Norquay¹, and Jim M. Wild^1
1Department of Cardiovascular Science, University of Sheffield, Sheffield, South Yorkshire, United Kingdom

MR oximetry with endogenous contrast can be confounded by physiological variations in the underlying signal. Exogenous agents can be useful, especially in regions such as the lungs, that suffers from low endogenous signal. This study explores the use of hyperpolarized 129Xe as an exogenous tracer of red blood cell oxygenation in human pulmonary vasculature.

Kai Ruppert¹, Talissa A. Altes¹, Jaime F. Mata¹, Iulian C. Ruset^2,3, F. William Hersman^2,3, and John P. Mugler, III^1
1University of Virginia, Charlottesville, VA, United States, ²Xemed, LLC, Durham, NH, United States, ³University of New Hampshire, Durham, NH, United States

“Chemical Shift Saturation Recovery” (CSSR), is a method for monitoring the uptake of hyperpolarized xenon-129 (HXe) by the lung parenchyma through the acquisition of a free induction decay following a variable delay time after an RF saturation pulse. The purpose of our studies was to demonstrate that, by holding the delay time fixed, it is feasible to evaluate the pulsation of flowing blood in the pulmonary capillaries in real time. We found that rhythmic pulsations with a period of approximately 1s in both dissolved-phase peaks are detectable at residual volume and total lung capacity.

Suryanarayanan S. Kaushik^1,2, Matthew S. Freeman^2,3, Zackary I. Cleveland^2,4, Rohan S. Virgincar², Scott H. Robertson^2,3, John Davies⁵, Jane Stiles⁶, William Michael Foster⁶, H. Page McAdams⁴, and Bastiaan Driehuys^2,4
1Biomedical Engineering, Duke University, Durham, North Carolina, United States, ²Center For In Vivo Microscopy, Duke University, Durham, NC, United States, ³Medical Physics Graduate Program, Duke University, Durham, NC, United States, ⁴Radiology, Duke University, Durham, NC, United States, ⁵Respiratory Therapy, Duke University, Durham, NC, United States, ⁶Pulmonary Medicine, Duke University, Durham, NC, United States

In addition to its alveolar gas-phase resonance (0 ppm), ¹²⁹Xe dissolved in the pulmonary tissues gives rise to distinct resonances in the barrier tissue (197 ppm) and red blood cells (211 ppm). To quantify this dissolved ¹²⁹Xe distribution, the gas-phase image should be acquired in the same breath. To this end, we describe an interleaved 3D-radial acquisition that acquires isotropic images of both the dissolved and gas-phase ¹²⁹Xe. Using this acquisition, we probe the effect of the supine and prone posture on the dissolved-phase signal distribution.

Miranda Kirby¹, Sarah Svenningsen¹, Alexei V. Ouriadov¹, Giles E. Santyr¹, David G. McCormack², and Grace Parraga^1
1Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada, ²Division of Respirology, Department of Medicine, The University of Western Ontario, London, Ontario, Canada

Our objective was to compare hyperpolarized helium-3 (3He) magnetic resonance imaging (MRI) apparent diffusion coefficients (ADC) and xenon-129 (129Xe) ADC with a b-value of 12s/cm2, 20s/cm2 and 30s/cm2 in the same healthy volunteers and chronic obstructive pulmonary disease (COPD) ex-smokers to determine which b-value associated with 129Xe ADC provides the greatest relationship with 3He ADC and standard measures of lung function. For all subjects, 3He ADC was significantly correlated with 129Xe ADCb=12 (r=.98, p<.0001) and ADCb=20 (r=.91, p=.002). DLCO was significantly correlated with 3He ADC (r=-1.00, p<.0001), 129Xe ADCb=12 (r=-.98, p<.0001) and 129Xe ADCb=20 (r=-.89, p=.003).

Juan Parra-Robles¹, Helen Marshall¹, and Jim M. Wild^1
1Unit of Academic Radiology, University of Sheffield, Sheffield, United Kingdom

In this work, the anomalous diffusion stretched-exponential model is used to describe multi b-value ³He MRI diffusion data from normal volunteers and COPD patients. Our results show that this model may provide a robust measure of changes in lung structure due to disease that is valid over a range of experimental conditions. This seems to indicate that the heterogeneity index  is insensitive to a range of uncertainties in experimental conditions but sensitive to changes in lung structure due to COPD/emphysema.

Hooman Hamedani¹, Stephen J. Kadlececk¹, Biao Han¹, Kiarash Emami¹, Yi Xin¹, Masaru Ishii², Milton Rossman³, and Rahim Rizi^1
1Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, ²Otolarynology, Johns Hopkins Medical Center, Baltimore, Maryland, United States, ³Pulmonary, allergy and Critical Care Division, University of Pennsylvania, Philadelphia, Pennsylvania, United States

The precision of hyperpolarized pAO2-imaging is diminished by abnormal flows that may occur during the required breath-hold, which can then result in implausible, non-physiologic values. It is shown here that a sequence of progressive breaths of hyperpolarized 3He prior to the pAO2-imaging not only improves the level of signal-to-noise, but also produces a more uniform distribution of imaging gas in parenchyma, ultimately resulting in more reasonable pAO2-maps. In addition, filling the poorly ventilated regions of the lung by progressive wash-in breaths provides information about these regions that is unavailable due to lack of signal when using the single-breath protocols.

Chengbo Wang^1,2, John P. Mugler, III^2,3, Eduard E. De Lange², G Wilson Miller², and Talissa A. Altes^2
1Faculty of Science and Engineering, University of Nottingham Ningbo China, Ningbo, Zhejiang, China, ²Radiology and Medical Imaging, University of Virginia, CHARLOTTESVLE, Virginia, United States, ³Biomedical Engineering, University of Virginia, CHARLOTTESVLE, Virginia, United States

Co-registered axial helium-3 apparent diffusion coefficient (ADC) maps were obtained in 24 healthy subjects and 15 patients with COPD using both short-time scale (STS) and long-time scale (LTS) techniques. Global histograms of all pixel-wise ADC values from all subjects showed a better separation of the COPD subjects from the healthy subjects for the LTS technique compared to the STS technique. A ROC analysis indicated that the LTS ADC method has a greater area under the ROC curve (LTS: 0.920 vs. STS: 0.849), suggesting that the LTS ADC is more sensitive to COPD than the STS ADC.

Maurizio Cereda¹, Yi Xin², Kiarash Emami², Jessie Huang², Jennia Rajaei², Harrilla Profka², Biao Han², Puttisarn Mongkolwisetwara², Stephen J. Kadlececk², Nicholas N. Kuzma², Stephen B. Pickup², Brian Kavanagh³, Clifford Deutschman¹, and Rahim Rizi^2
1Department of Anesthesiology and Critical Care, University of Pennsylvania, Philadelphia, Pennsylvania, United States, ²Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, ³Departments of Critical Care Medicine and Anesthesia, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada

Using hyperpolarized gas MRI, we provide evidence supporting the role of airspace recruitment, rather than expansion, in ventilated healthy rats without atelectasis. Our results showed that hysteresis was associated with a decrease in the size of ventilated airspaces. These results, obtained through imaging, are relevant because they contribute to the clarification of a controversial physiological mechanism. Furthermore, this study provides an additional rationale for investigating strategies that may minimize pulmonary stress.