Affiliations: [a] Cancer Research UK Clinical Magnetic Resonance Research Group, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Surrey, UK | [b] Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, John Radcliffe Hospital, Oxford, UK | [c] Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Surrey, UK | [d] Department of Radiology, University of California, San Diego, CA, USA | Cancer Research UK Clinical Magnetic Resonance Research Group, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT, UK
Correspondence:
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Corresponding author: Christina Messiou, Senior lecturer in imaging and consultant Radiologist, Magnetic Resonance Imaging Department, Royal Marsden Hospital, Downs Road, Sutton, Surrey SM2 5PT, UK. Tel.: +44 0208 642601, cordless ext: 1378, or 0208 661 3340; E-mail: [email protected].
Abstract: Introduction:Ultra Short TE MRI allows signal to be detected from tissues with a very short T2.The aims of this study were to optimize a 2D UTE MRI sequence for imaging and quantification of sclerotic bone metastases, establish T2* values of sclerotic components and investigate the feasibility of using the method to assess changes in T2* of sclerotic metastases and their relation to attenuation values in patients on treatment. Methods:Twenty-two subjects were recruited in 3 cohorts. Cohort 1 was used to optimize the 2-D UTE sequence, cohort 2 was used to establish T2* measurements using a range of TEs and cohort 3 was used to assess T2* changes with treatment response and relate them to changes on electron density as measured by CT Hounsfield Units. Results:Sagittal 2D UTE MRI of the lumbar spine is feasible demonstrating short T2 components in normal volunteers. In patients with bone metastases secondary to prostate carcinoma T2* can be measured and mean T2* of sclerotic metastases measured with TEs of 0.07, 0.27, 0.47 and 0.67 ms was 8.5 ms.T2* shortened by 20.0% in responders and increased by 24.4% in progressors. Discussion:The significant linear relationship between percentage change in T2* as derived from UTE MRI and percentage change in HU from corresponding CT studies is indirect evidence that they are measuring effects of the same process.If the relationship between T2* and electron density holds true in further studies it offers potential for MR guided radiotherapy planning as well as attenuation correction for PET/MRI.
Keywords: Bone, metastasis, computed tomography, magnetic resonance imaging
