Trends in Static Magnetic Field Exposure due to MRI Penny Gowland Magnetic Resonance Centre University of Nottingham Future trends Overview • The numbers of patients exposed • The field strength of exposure – Why high field ? – Changes in magnet design • The ranges of applications • The classes of staff exposed • The alternatives Number of scanners in the UK 400 2000-3000 Increasing at scan per 30-40 p.a. scanner Embedded table (double click to see it) p.a. 350 300 250 200 150 100 50 3 20 0 1 20 0 9 19 9 7 19 9 5 19 9 3 19 9 19 9 1 0 1-2% of the UK population have an MRI scan every year 800,000 scans p.a. in UK, capacity will increase 10% soon MagNET New title slide to break up presentation Field strength trends MR market share >=1,5T 1899 Embedded1,0T excel file 0,5T - 0,7T <0,5T 583 161 03 20 01 20 99 19 97 19 95 19 93 19 91 19 89 19 87 19 85 97 19 19 83 70% 65% 60% 55% 50% 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% Projected market 100% >=3T 1.5T 1.0-0.5T 0% 1999 2004 Embedded image 2009 <0.5T Ultrahigh field • High field milestones: – 8T to Ohio State University 1998 – 7T to Minnesota 1999 Try to put some sort of image on every slide (depending on audience and the – 9.4T to Minnesota 2003 the talk) • Expected world market forpoint 7T ofwhole body is ~ 10 to 15 systems (expected to increase significantly over the next 5 years) • Magnex and Oxford both shipped 9.4T whole body scanners last year. Why high field? Whyhigh field ? • Signal: – SNR ~ Bo • Chemical shift: – CS ~ Bo   • Susceptibility These were ticks and crosses.. Look what can happen to fonts when ppt files are moved between computers  DB ~ Bo   • RF heating: – SAR ~ Bo2  • Relaxation times: – T1 increased;   – T2/T2* decreased  Wicklow, Washington University, St. Louis Using increased S/N • Increase spatial resolution – Microscopy, fibre tracking – Thinner slices • Increased temporal resolution – Dynamic imaging • Shorter experiments – reduced imaging time – reduced susceptibility artefacts T2 weighted Tx/Rx Quad Head 1024 Matrix, 4 mm,TE 80, TR 4s High spatial resolution- hair folicles 4.7 T Zoomed in corner of image Roger Ordidge, UCL Anatomical imaging in MS Suspected MS 1.5 T 640 x 1024 Custom animation Dept. of Radiology, University of Bonn, Germany 256 x 512 3.0 T Summary • This magnet is great!   Bo Embedded equation Insert> Object> Equation To get colour right, Right click> Format object> Picture> Recolour Acknowledgements • My family