Standardizing Image Acquisition

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Standardizing Image Acquisition

• Jeffrey L. Evelhoch, PhD
• Director
• Medical Sciences (Imaging)

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Why standardize acquisition?
Best Image Processing Ever
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Issues to consider

• Manufacturer-based differences
• Technology changes
• Not all sites are created equal
• QC for quantitative v. diagnositic imaging
• Appropriate method depends on
• Exact question
• Image analysis methods
• Who will mind the shop

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An Example Consensus Protocol

• DCE-MRI
• Early phase clinical trials for drugs targeting
  tumor blood supply      
• Low molecular weight gadolinium chelates
• 1.5 Tesla

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A Brief History

• October 1999 NCI Workshop ? consensus
  recommendation
• Included both treatment response and breast
  diagnosis
• March 2002 CRUK PTAC Workshop ? consensus
  recommendation
• Treatment response in early clinical trials
• Nov 2004 NCI Workshop ? consensus recommendation
• Treatment response in early clinical trials

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NCI Workshop Participants

• Jeffrey Abrams
• Thomas Chenevert
• Laurence Clarke
• Jerry Collins
• Jeffrey Evelhoch
• Susan Galbraith
• Michael Knopp
• Jason Koutcher
• Martin Leach
• Nina Mayr
• Daniel Sullivan
• Edward Ashton
• Peter Choyke
• Patricia Cole
• Gregory Curt

• Milind Dhamankar
• Michael Jacobs
• Gary Kelloff
• Adrian Knowles
• Lester Kwock
• Peter Martin
• Teresa McShane
• Anwar Padhani
• Stefan Roell
• Mark Rosen
• Gregory Sorensen
• Charles Springer
• Michael Tweedle
• Donald Williams
• Antonio Wolff

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Specific recommendations for

• Type of measurement
• Requirements for contrast agent injection
• Primary endpoints
• Secondary endpoints
• Nomenclature
• Data reduction
• Region of interest

• Images acquired prior to contrast injection
• Dynamic acquisition protocol
• Measurement requirements for primary endpoints
• Trial design
• Image analysis

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Lets consider issues approaches adopted to
address those issues
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Manufacturer-based differences
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Approaches

• Need access to experts on all systems
• Use basic sequences (differences smaller)
• Tweak parameters to match as closely as possible
• Make certain reconstruction methods are as close
  as possible
• Same reference standard on all systems

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Technology changes ? keep it simple

• 1.5-T (for near future)
• Basic sequences (less likely to change with
  upgrades)
• Parameters (at least) one step back from cutting
  edge
• Use analysis with considerable experience within
  community, most forgiving
• Revisit recommendations periodically

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Not all sites are created equal

• Keep it simple
• Training, training, training,
• Routine QC
• Careful monitoring
• Immediate feedback

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QC for quantitative v. diagnositic imaging

• Requires higher performance
• MR system
• Sequences
• Set-up procedures
• Radiological processes
• Better here

or here?
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Appropriate method

• For breast cancer diagnosis want dynamic
  temporal-spatial resolution trade-off

M. Schnall,MRM 2001
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Who will mind the shop?
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Summary of key recommendations fordata
acquisition
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General Issues

• Entry criteria should consider tumor size in
  relation to pharmacological mechanisms, MRI
  resolution, sensitivity to motion and potential
  confounding factors from previous treatment
  (e.g., radiation) or rapid tumor growth rates
• Tumors in a fixed superficial location should be
  at least 2 cm in diameter other tumors should be
  at 3 cm in diameter
• Adjust orientation so that motion is in-plane
  when motion effects cannot be avoided (e.g.,
  liver, lungs)

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Pre-injection

• Acquire high quality clinical images of entire
  anatomic region (preferably in two orthogonal
  planes)
• Acquire T1- and T2-weighted images registered in
  the same planes as the dynamic data
• If possible, measure T1 (using same resolution
  and field of view for dynamic data)

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Contrast agent injection

• Use power injector to minimize variation
• Injection dose should be standardized by weight
• 15-30 sec for total injection, at least 20 cc
  saline flush
• Document injection site, use same site for
  subsequent studies in same subject
• Minimum of 24 h between studies

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Dynamic study (I)

• For first 150 sec after bolus injection, use
  fastest sampling possible consistent with spatial
  resolution/anatomic coverage requirements, but
  not slower than 20 sec temporal resolution

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Dynamic study (II)

• Acquire data out to at least 8 min (continual
  sampling is optional)
• If possible, include in imaging volume a
  normalization function (e.g., arterial or other
  tissue)
• For serial studies, imaging volume of interest
  should be adjusted to sample same region of tumor

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Summary

• Development application of appropriate protocol
  requires close academic-industry interaction
• For multi-center studies
• Keep it as simple as possible while still getting
  the required info
• Clarity education up front is essential
• Non-standard methods require substantial
  continuous support