Evolution of CBCT: An Academic and Industrial Collaboration

Johns Hopkins University and Carestream bring weight-bearing extremity imaging to market.

There is a well-known adage in radiology: “You see what you look for; you look for what you know.” British philosopher Gilbert Ryle would likely place this level of thinking in the realm of “knowing how  — implicit, experiential, skill-based learning” versus “knowing that” –content that  we learn from text and rule books. (1)

Source: Jaffe C. Medical Imaging, Vision and Visual Psychophysics: Kodak monograph (vol. 60 #1)

A radiographer’s library of content knowledge – our ‘clinician brain”- grows over time with each study. Similarly, we need the other dependent components in the diagnosis cycle pictured below to advance along with us. While working at Johns Hopkins University, I participated in an academic/industrial collaboration to optimize cone beam computed tomography (CT) diagnostic imaging technology. Along with others at the university, I provided direction on potential clinical applications, and helped with each redesign/improvement of the system through its different generations. The collaboration resulted in the Carestream OnSight 3D Extremity System which is now commercially available.

The research was especially important to me because of my interest in musculoskeletal medical imaging. Musculoskeletal disorders are the most common causes of severe long-term pain and physical disability, affecting hundreds of millions of people across the world.  Advancements in imaging technology could help us make earlier and better diagnoses to change management, or change prognosis, or provide better decision making for utilization of resources.

Until recently, CT imaging systems were multi detector and multi-slice. A narrow slice of the patient is imaged with a “fan beam” of X-rays. To image an extended volume of the anatomy via CT, the patient must be moved through the fan beam of x-rays as it rotates around the patient multiple times.

Image of data acquisition of skull using cone beam CT

With CBCT, a large-area detector images an extended volume of the patient in a single rotation.

In contrast, in cone beam CT (CBCT), a large-area detector images an extended volume of the patient in a single rotation. I think of it as a “one-thousand-slice CT scanner”. Because there is only one rotation around the patient, the mechanics are simpler and allow for novel applications, such as in musculoskeletal.

Benefits of CBCT imaging

The new CBCT imaging system provides several important benefits and new applications:

  • Large field of view and at high resolution. We can do isotropic spatial resolution pushing toward 300 microns which gives us insight into important measures like bone health.
  • Image acquisition is short – about 20 seconds. It requires about half the dose of a multi-detector CT using the regular setting.
  • Its ability to capture weight-bearing images provides insight on miniscule extrusion which has been difficult in the past.  These weight-bearing images have value for knee, foot and ankle joints; biomechanical comparison healthy vs. disease; comparison with pressure measurements; improved detection of arthrosis and impingement, and other applications.
  • CBCT is also favorable from a workflow standpoint for the patient, rad tech, and radiologist. If you get your inputs right, it only takes a brief acquisition set. Then you can go ahead and post-process it, getting a 3D image fairly quickly.

Innovative weight-bearing CBCT systems are commercially available now, but the research and new developments continue. Myself and others are exploring the possibility of improving contrast resolution for soft tissue through post-processing; bone microstructure; dual energy with three-source CBCT; and evaluations of bone erosions in rheumatoid arthritis patients using cone beam computed tomography along with magnetic resonance imaging and ultrasound.

Additionally, work is ongoing to establish the clinical significance of CBCT metrics and weight-bearing images. The Weight Bearing CT International Study Group is dedicated to enhancing diagnosis and understanding of weight bearing foot and ankle conditions. (2)

The process for our academic/industrial collaboration

Text from the research framework

The Research Framework established by Jeffrey G. Jarvik was followed closely.

The process for developing and testing the cone beam CT system and new applications was very collaborative and methodical. We followed the Research Framework based on a 6-tiered model of diagnostic efficacy established by Jeffrey G. Jarvik.

As the team conducted our research, we continually asked:

  • What are we looking for when developing biomarkers?
  • What is the image measuring and what is it we want to measure?
  • Do our engineering and physicist counterparts find technical validity in it?
  • Are we measuring the pathologies that are of interest?

Once we had a working prototype from Carestream, we brought in members of our clinical teams including orthopaedists, rheumatologists, and others. We also noted feedback from our radiology technologists on workflow, and worked with our bio medical engineers. And we included several radiologists with different levels of experience.

Throughout the process, we provided direction to Carestream’s engineers on potential clinical applications, and on each redesign/improvement of the system through its different generations. Our goal was to help create an imaging system with a favorable cost profile that can be used at the point of care where a doctor can maximize its ability for decision making. I believe we accomplished our goals.

Learn more about the CARESTREAM OnSight 3D Extremity System.

Dr. John A. Carrino is Vice-Chairman of the Radiology and Imaging Department at the Hospital for Special Surgery and Professor of Radiology, Weill Medical College of Cornell University. The views and opinions expressed in this blog are those of Dr. Carrino, and do not reflect the views and opinions of Hospital for Special Surgery.

A highly regarded physician and winner of several academic honors and awards, Dr. Carrino’s background includes medical imaging diagnostics, leadership in major medical institutions, and extensive experience in image guided interventions.  Dr. Carrino is widely recognized as a leader in the musculoskeletal medical imaging and healthcare informatics fields specializing in organizing, structuring and implementing novel programs and information systems. He is a member of Carestream Health’s Medical Advisory Board.

 

Resources

White Paper: Advantages of Volumetric Cone Beam Imaging for Orthopaedic Extremity Exams

Video: Dr. Mikael Ploug Boesen of Copenhagen University Hospital explains the Complementary Roles of Weight-bearing Cone Beam Technology for Imaging Bones and MRI for Soft Tissue.

Blog: Weight-bearing CT Study Group Offers Potential for Better Care

 

References:

  1. https://www.newyorker.com/magazine/2017/04/03/ai-versus-md
  2. https://www.wbctstudygroup.com/

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