MRI Scientists Get Closer to Quantifying Wrist Dynamics

RESEARCH BRIEF

By Pawel Slabiak • August 9, 2024

Center for Advanced Imaging Innovation and Research

Scientists at NYU Langone Health and the Center for Advanced Imaging Innovation and Research are changing that.

The wrist plays an essential role in human dexterity but its kinematics have never been quantified in vivo.

It has so far been impossible to noninvasively image the natural motion of carpal bones in 3D or to quantify their movements.

The wrist, or "carpus," comprises eight uniquely shaped bones linked by a network of ligaments and muscles.

Hamate

Capitate

Trapezoid

Pisiform

Triquetrum

Lunate

Scaphoid

Trapezium

The team is focusing on a simple motion called radial-ulnar deviation. 

To shed light on the dynamics of this complex joint, researchers at NYU Langone are using MRI, flexible imaging coils, machine learning, and 3D computer modeling.

The researchers created a flexible radiofrequency coil that wraps around the wrist like a compression brace and follows the movement of the hand. 

Ruoxun Zi, doctoral candidate in the biomedical imaging and technology program at NYU Grossman School of Medicine, demonstrates the flexible wrist coil in NYU Langone's radiofreqency (RF) laboratory.

The high-impedance flexible coil technology was developed at NYU Langone's Center for Advanced Imaging Innovation and Research in 2018, facilitating new investigations into the kinematics of moving joints.

A 3D-printed, articulating platform allows study participants to perform radial-ulnar deviation in a controlled, reproducible way during an MRI scan.

Using a "LiveView" MRI sequence, the team images the wrist in thin, two-millimeter slices at a speed similar to standard video frame rate.

marker ↑

marker ↓

Although MRI is capable of acquiring 3D data, doing so takes longer per volume and would be too slow to capture motion at natural speed. Therefore, to image fast the researchers must image thin.

Markers built into the articulating platform allow the team to use machine learning to automatically align the slices after the scan...

...and create synthetic 4D MRI volumes (three spatial dimensions plus time).

The post-processing pipeline starts with a "template," an abstract representation of the carpal bones specific to an individual wrist. 

A dynamic MRI with segmentations of the radius and wrist bones.

Batool Abbas, PhD, postdoctoral fellow at NYU Langone has led the development of post-processing and 3D modeling.

A template is, “essentially, a statistical descriptor that represents the wrist in a neutral position created by averaging all the different poses the wrist takes over the course of the MRI sequence,” she explained. 

...resulting in a 3D model of the wrist bones.

The template image is used to semi-automatically segment the carpal bones, and the segmentation is then back-propagated to each frame in the sequence...

Point-cloud models of a trapezoid bone before registration (top) and after (bottom).

A rigidity constraint is then added to ensure that the modeled bones retain their shapes across all frames.

The unconstrained model's slight quivering (left) results from nonlinearities introduced by preceding segmentation and registration steps. The rigidity constraint eliminates these and stabilizes the radius bone for reference.

Before

After

The process allows the researchers to find and track every modeled bone's center of mass.

Capitate

Lunate

Scaphoid

Trajectories extracted from the modeled bones are the first draft of an emerging method for quantifying carpal motion.

Displacements of carpal bones in the X-Y plane during an MRI scan (color) and rescan (white) of radial-ulnar deviation, graphed on millimeter grid. The relative position of the traces has been changed for purposes of illustration; orientation and scale have been preserved.

Hamate

Capitate

Trapezoid

Pisiform

Triquetrum

Lunate

Scaphoid

Trapezium

"Normal wrist kinematics is not well understood because people haven't been able to measure it," said Riccardo Lattanzi, PhD, professor of radiology at NYU Langone. 

Dr. Lattanzi is the principal investigator on the project, which is supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

Dr. Lattanzi first started looking into wrist kinematics with colleagues at NYU Tandon School of Engineering after Catherine Petchprapa, MD, told him about her prior research in this area.

Dr. Petchprapa, associate professor of radiology at NYU Langone and member of the research team, has a long-standing interest in hand and wrist imaging.

"Besides the desire to understand this complex joint, knowledge of wrist kinematics in normal and pathologic conditions will have obvious impact on treatment," said Dr. Petchprapa.

Conditions like wrist instability, which can manifest as snapping or popping and can lead to osteoarthritis, are challenging to see and cannot be quantified with current standard imaging methods.

Point-clouds of a scaphoid bone.

"If we are able to get this to work, then we can study some of the more complicated motions that make humans uniquely able to do the things that [the wrist] does.”

"It starts as a clinical question but leads into a more fundamental inquiry,” said Dr. Petchprapa.

A 3D model from scan and rescan MRI data.

Credits: Research images and animations courtesy of Batool Abbas, Riccardo Lattanzi, and Ruoxun Zi. Photos by Adi Goldstein/Unsplash, McKenna Phillips/Unsplash, Andrew Neary/NYU Langone Health, Pawel Slabiak/NYU Langone Health. Illustration by Pawel Slabiak, including material from A.F. Dixon's Manual of Human Osteology and E. Muybridge's Plate Number 361, Throwing a Spear. Video, text, and production by Pawel Slabiak.

Research reported in this story was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health (NIH) under award number R21AR080325. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Related Publications

cai2r.net

Abbas B, Zi R, Block KT et al. Functional Kinematic Assessment of the Wrist Using Volumetric Dynamic MRI. Proc Intl Soc Magn Reson Med. 32 (2024). p 1027. Zi R, Wang B, Walczyk J et al. Volumetric Dynamic Imaging for Functional Kinematic Assessment of the Wrist. Proc Intl Soc Magn Reson Med. 31 (2023). p 1437.