Accurate semiautomatic assessment of ligament length variations from MRI data.

Purpose: A semiautomatic method for the assessment of ligament length variations during different joint positions based on MRI data is proposed.

Methods: Ligament lengths are represented as distances between points marking characteristic locations in the ligament insertion regions on the bones. These points are defined manually for one single reference joint position and for all other joint positions they are automatically mapped with high accuracy to the correct locations using image registration methods.

Knee cartilage MRI with in situ mechanical loading using prospective motion correction.

Purpose: To assess the feasibility of high resolution knee cartilage MRI with in situ mechanical loading using optical tracking to compensate for motion.

Methods: In vivo cartilage MRI with in situ mechanical loading is demonstrated on a clinical 3T system for the patellofemoral as well as for the tibiofemoral knee joint using a T1-weighted spoiled three-dimensional gradient-echo sequence. Prospective motion correction is performed with a moiré phase tracking system consisting of an in-bore camera and a single tracking marker attached to the skin.

Reproduction of motion artifacts for performance analysis of prospective motion correction in MRI.

Purpose: Despite numerous publications describing the ability of prospective motion correction to improve image quality in magnetic resonance imaging of the brain, a reliable approach to assess this improvement is still missing. A method that accurately reproduces motion artifacts correctable with prospective motion correction is developed, and enables the quantification of the improvements achieved.

Methods: A software interface was developed to simulate rigid body motion by changing the scanning coordinate system relative to the object.

Measurement and correction of microscopic head motion during magnetic resonance imaging of the brain.

Magnetic resonance imaging (MRI) is a widely used method for non-invasive study of the structure and function of the human brain. Increasing magnetic field strengths enable higher resolution imaging; however, long scan times and high motion sensitivity mean that image quality is often limited by the involuntary motion of the subject. Prospective motion correction is a technique that addresses this problem by tracking head motion and continuously updating the imaging pulse sequence, locking the imaging volume position and orientation relative to the moving brain.