Evaluation of an imaging biomarker, Dixon quantitative chemical shift imaging, in Gaucher disease: lessons learned.

Gaucher disease (GD) is the first lysosomal storage disorder for which specific therapy became available. The infiltration of bone marrow by storage cells plays an important part in the pathophysiology of skeletal complications and can be quantified by measurements of bone marrow fat fraction (Ff). Ff measurements by Dixon quantitative chemical shift imaging (QCSI) are standard for the follow-up care of GD patients at the Academic Medical Center. Several criteria should be met in order for these measurements to qualify as an imaging biomarker. These include: 1) The presence of the imaging biomarker is closely coupled or linked to the presence of the target disease or condition; 2) The detection and/or quantitative measurement of the biomarker is accurate, reproducible, and feasible over time, and; 3) The changes measured over time in the imaging biomarker are closely coupled, or linked, to the success or failure of the therapeutic effect and the true end point for the medical therapy being evaluated. This review assesses the use of Ff measurements by QCSI as a biomarker for GD in light of these criteria. In addition potential pitfalls are discussed including: degenerative disc disease; vertebral collapse and infection; haematological malignancies; focal fatty deposits; age; menopause; phase and repositioning errors, and; fat surrounding the basivertebral vein.QCSI measurements of Ff can be used as an imaging biomarker for GD taking these pitfalls into account. It is one of the first biomarkers, in particular imaging biomarkers, for GD that has been systematically evaluated and could be a valuable tool in clinical trials comparing different treatments or dosing regimens.