Traditional Posters: Body Imaging

Angelos Kyriazis^1,2, Ignacio Rodriguez^1,2, Jose-Manuel Perez-Sanchez³, Lars E. Olsson⁴, Jesus Ruiz-Cabello<sup>1,2

1</sup>Universidad Complutense de Madrid, Instituto de Estudios Biofuncionales, Madrid, Spain; ²CIBER de Enfermedades Respiratorias, Spain; ³Orsay and Kremlin-Bicetre, U2R2M, Paris, France; ⁴DECS Imaging, AstraZeneca R&D, Mölndal, Sweden

A method to estimate regional lung volume over time based on spin-density 3He images is presented. Combining this with the tracheal pressure, regional volume over pressure is appraised. The static ROI are the left and the right lobe of the lung. Physiological parameters were calculated for the two ROI and for the whole lung. The method is proven reproducible because the measurements of the ROI of the same animal as well as the measurements of different animals agreed satisfactorily. The method may differentiate not only healthy from diseased animals but also healthy from diseased areas of the lung.

2565. In Vivo Comparison of 2D and 3D T2* in the Rat Lung Using Hyperpolarized Helium-3 MRI at 1.5 T

Kyle Hill^1,2, José-Manuel Pérez-Sánchez², Roberta Santarelli², Mathieu Sarracanie², Pascal Hagot², Marlies Friese², Xavier Maître², Luc Darrasse<sup>2

1</sup>University of Oxford, Oxford, Oxfordshire, United Kingdom; ²Imagerie par Résonance Magnétique Médicale et Multimodalité (UMR 8081), Univ Paris-Sud, CNRS, Paris, Le Kremlin-Bicêtre, France

The T¬2* of hyperpolarized helium-3 in the lungs has shown promise in characterizing lung microstructure due to its sensitivity to local gradients caused by gas-tissue interfaces, whose abundance per unit volume changes with lung inflation and pathological modification. Despite the lung’s three-dimensional structure, most measurements of helium-3 T¬2* have been performed using projection imaging which neglects the complex microstructure’s effects. This work uses five rats in vivo to compare the T2* in a projection image with 3D imaging and shows that 3D is necessary to detect statistically different local phenomena that may not be apparent in projection imaging.

2566. Gravity Dependent Ventilation of Rats Measured by Hyperpolarised Helium MRI and Electric Impedence Tomography

Marlies Elly Joy Friese¹, Kimble R. Dunster, ¹², Gary J. Cowin¹, Deming Wang¹, Graham Galloway¹, John Fraser^3,4, Andreas Schibler, <sup>4,5

1</sup>Centre for Magnetic Resonance, The University of Queensland, Brisbane, Queensland, Australia; ²Medical Engineering Research Facility,, Queensland University of Technology, Brisbane, Queensland, Australia; ³Paediatric Intensive Care Unit,, Mater Children’s Hospital, Brisbane, Queensland, Australia; ⁴Critical Care Research Group, The Prince Charles Hospital, Brisbane, Queensland, Australia; ⁵Paediatric Intensive Care Unit, Mater Children’s Hospital, Brisbane, Queensland, Australia

Gravity-dependent ventilation distribution was investigated in using both hyperpolarised helium-3 magnetic resonance imaging (HP3He MRI) and electrical impedance tomography (EIT). Time averaged EIT data and HP3HeMRI images of apnoea showed ventilation distribution in rats to be gravity dependent, whereas regional filling characteristics are dependent on anatomy. HP3He MRI and EIT data agree where they can be compared. HP3He MRI provides data on real geometry which EIT cannot as EIT tomograms are reconstructed to a circular image. Dynamic imaging of the breathing cycle with HP3He is still needed to make a full comparison of the two methods.

2567. Respiratory Impedance in a Mouse Model of Asthma Using Hyperpolarized ³He MR Imaging

Suryanarayanan Sivaram Kaushik¹, John Nouls¹, Erin Potts², Zackary Cleveland¹, W Michael Foster², Bastiaan Driehuys<sup>1

1</sup>Center for In-Vivo Microscopy, Duke University Medical Center, Durham, NC, United States; ²Pulmonary and Critical Care Medicine, Duke University Medical Center, Durham, NC, United States

The broncho-constriction and inflammation associated with asthma contributes to increased airway impedance. This impedance is typically measured using global respiratory mechanics techniques such as FlexiVent. However, the time course of broncho-constriction can also be directly visualized using hyperpolarized (HP) 3He MRI. This imaging-based technique provides a time-dependent method for quantifying central airway impedance and may be useful to assess the regional contributions to globally measured impedance. Here, we discuss the method we used in obtaining the upper airway impedance during a Methacholine (Mch) challenge, in a mouse model of asthma.

2568. Relaxation of Hyperpolarized ¹²⁹Xe in a Flexible Gas Reservoir