Alan C. Seifert¹, Cheng Li¹, Suzanne L. Wehrli², and Felix W. Wehrli^1
1University of Pennsylvania, Philadelphia, PA, United States, ²Children's Hospital of Philadelphia, Philadelphia, PA, United States

Proton NMR signal in bone arises from pore water (T2 > 1ms), bound water (T2 ~ 400±100µs), and collagen (T2 << 100µs). Pore water is hypothesized to scale with porosity, and bound water with collagen density. Here we measured single adiabatic inversion-recovery zero echo-time (SIR-ZTE) bound water density in 15 human cortical bone specimens at 9.4T, and found strong correlations with both gravimetric organic matrix density (R^2 = 0.74) and µCT porosity (R^2 = 0.73). SIR-ZTE is therefore suitable for measurement of matrix density in vivo.

Jun Chen¹, Michael Carl², Hongda Shao¹, Soorena Azam Zanganeh¹, Eric Chang^1,3, Christine B Chung^1,3, Graeme M Bydder¹, and Jiang Du^1
1Radiology, University of California, San Diego, CA, United States, ²GE Healthcare, San Diego, CA, United States, ³Department of Radiology, VA San Diego Healthcare System, San Diego, CA, United States

Bound and pore water have been reported to make different contributions to the mechanical properties of cortical bone. By using Ultrashort echo time (UTE) sequences signals from both bound and pore water can be detected in cortical bone. In this study, tibial and femoral mid-shafts in healthy volunteers were respectively imaged with 3D Cones and 3D IR-Cones sequences, to measure T1 and T2* of bound and pore water at both sites, and to investigate whether there are differences between these two sites. High resolution imaging of the tibia and fermur can be achieved. The femoral midshaft and tibial midshaft have different MR properties, including bound and pore water T2*s, relative fractions, effective T1 of both bound and pore water, and T1 of bound water.This study suggests that T1 and T2* of bound and pore water in cortical bone can be measured with 3D Cones and IR-Cones sequences; femoral and tibial midshafts may have different properties in healthy volunteers.

Silvia Capuani^1,2, Giulia Di Pietro^2,3, Guglielmo Manenti⁴, Vincenzo Vinicola⁵, Marco Bozzali⁶, and Umberto Tarantino^7
1Physics Department, CNR-IPCF Roma Sapienza University of Rome, Rome, Italy, Italy, ²Center for Life NanoScience@LaSapienza, Istituto Italiano di Tecnologia, Rome, Italy, Italy, ³Enrico Fermi Center, Rome, Italy, Italy, ⁴Department of Diagnostic Imaging and Interventional Radiology, “Tor Vergata” University of Rome, Rome, Italy, Italy, ⁵4Rehabilitation Hospital IRCCS Santa Lucia Foundation, Rome, Italy, Rome, Italy, Italy, ⁶Neuroimaging Laboratory Santa Lucia Foundation, Rome, Italy, Italy, ⁷5Department of Orthopaedics and Traumatology, PTV Foundation, “Tor Vergata” University of Rome, Rome, Italy, Italy

The investigation of calcaneus bone-marrow might offer the chance of reducing the risk of subjects’ claustrophobic reactions, which remains a major source of drop-outs in Magnetic Resonance (MR) examinations. In this work the reliability and the potential of MR Spectroscopy in calcaneus is discussed. MRS in calcaneus can provide reliability fats estimation and L13/L43, L13/L52+L53 may be reliable markers of osteoporosis. Since bone-marrow fats in calcaneus are characterized by a different metabolism compared to that of vertebral or femoral sites, MRS in calcaneus performed in large population, may increase our pathophysiological understanding of osteoporosis from a metabolic point of view.

Michael Carl¹, Jiang Du², and Graeme M Bydder^2
1GE Healthcare, San Diego, CA, United States, ²UCSD, CA, United States

In this work we explore the collection of several UTE k-space spokes after the application of a single IR pulse. Theoretical calculations, simulations, and phantom experiments were used to optimize the sequence parameters such as TI and flip angle.

Djaudat Idiyatullin¹, Michael Garwood¹, and Donald Nixdorf^2
1CMRR, Radiology Department, University of Minnesota, Minneapolis, Minneaota, United States, ²Division of TMD & Orofacial Pain and Department of Neurology, University of Minnesota, Minneapolis, Minneaota, United States

This work demonstrates that dental MRI using SWIFT identifies cracks of about 20 μm thickness and larger, which is one order of magnitude smaller than the image voxel, within the dentin of teeth. To explain this phenomenon, a dental digital MRI model based on known 1H relaxation parameters in dental tissues is proposed. The comparison of simulated and experimental data helps to understand the mechanisms of contrast observed in SWIFT images of cracked teeth. The similarity of dentin and cortical bone allows the generalization of the proposed model for studies other bone pathologies.

Hao Wu¹, Shuguang Chu¹, Huaping Sun¹, Yumin Zhong², Quanmin Nie³, Liemei Guo³, Xi Yang³, Hong Zhang², Yi Lin², Weibo Chen⁴, He Wang⁵, and Ming Zhu^2
1Department of Radiology, HuaShan Hospital North, Fudan University, Baoshan District, Shanghai, China, ²Department of Radiology, Shanghai Children¡¯s Medical Center, Shanghai Jiao Tong University School of Medicine, Pudong New District, Shanghai, China, ³Department of Neurosurgery, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Pudong New District, Shanghai, China, ⁴Philips Healthcare, Shanghai, China, ⁵Philips Research China, Shanghai, China

By the research of skull fracture specimens of 10 Bama pigs and 45 skull fracture patients, our study firstly found that MRI three dimentional ultrashort echo time (UTE) dual-echo pulse sequences clearly demonstrated the skull structures and fractures including linear, depressed and comminuted fractures. On this basis, the head MRI scan sequences of paediatric and adult patients of craniocerebral trauma, will be designed to partly replace CT to achieve the goal of no radiation and accurate imaging diagnosis. Particularly, the infants, children and pregnant women who are sensitive to or prohibited from X-ray will benefit from this study.

Alexey V. Dimov^1,2, Zhe Liu^1,2, Pascal Spincemaille², Jiang Du³, and Yi Wang^1,2
1Department of Biomedical Engineering, Cornell University, Ithaca, New York, United States, ²Radiology Department, Weill Cornell Medical College, New York, New York, United States, ³University of California (San Diego), California, United States

In the current work we us an ultrashort echo time (UTE-GRE) pulse sequence for MR signal acquisition and field map estimation within the bones; preliminary results demonstrate CT-quality quantitative susceptibility mapping of bone using the proposed technique both ex- and in-vivo.

Michael Dieckmeyer¹, Stefan Ruschke¹, Christian Cordes¹, Samuel Paran Yap¹, Hendrik Kooijman², Hans Hauner¹, Ernst J. Rummeny¹, Jan S. Bauer¹, Thomas Baum¹, and Dimitrios C. Karampinos^1
1Technische Universität München, Munich, Germany, ²Philips Healthcare, Germany

MRS-based vertebral bone marrow fat quantification is confounded by the overlapping of water and fat peaks and the differences in T₂ relaxation times of water and fat. The purpose of the present study was to determine using single-voxel MRS the vertebral bone marrow proton density fat fraction (PDFF) using single-voxel MRS, addressing the confounding effects introduced by overlapping water-fat peaks and the difference in T₂ relaxation time between the water and fat components. The importance of the consideration of T₂ decay effects in bone marrow fat quantification was shown in the context of the analysis of the bone marrow fat fraction age dependence.

Yanchun Zhu¹, Jiang Du², Qun He², Shanglian Bao³, Song Gao³, Guoru Zhao¹, and Yaoqin Xie^1
1Institue of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China, ²Department of Radiology, University of California, California, United States, ³Beijing City Key Lab of Medical Physics and Engineering, Peking University, Beijing, China

Dual Echo UTE Imaging with Rescaled Subtraction (dUTE-RS): Scaling Factor Optimization Study

Markus Weiger¹, Mingming Wu^1,2, Moritz Christoph Wurnig³, David Kenkel³, Andreas Boss³, Gustav Andreisek³, and Klaas Paul Pruessmann^1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, ²Institute of Biomedical Engineering, Karlsruhe Institute of Technology, Karlsruhe, Germany, ³Institute for Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland

Zero echo time (ZTE) imaging enables direct MRI of tissues with rapid relaxation, such as e.g. bone, tendons, or ligaments. Yet the feature of detecting signals from a wide T2 range is accompanied by a lack of contrast between the corresponding tissues. Therefore, in this work, efficient long-T2 suppression is developed for the ZTE technique. In this way, selective, direct musculoskeletal MRI akin to CT contrast is enabled and demonstrated in a tissue sample.