MRI R2* and quantitative susceptibility mapping in brain tissue with extreme iron overload.

Area of Science:

• Neuroimaging
• Medical Physics
• Biochemistry

Background:

• R2* and quantitative susceptibility mapping (QSM) are established for assessing brain iron levels.
• Their accuracy in extreme iron overload conditions, such as aceruloplasminemia (ACP), remains unclear.
• This study evaluates R2* and QSM algorithms in ACP patients versus healthy controls.

Purpose of the Study:

• To assess the usability of R2* and QSM techniques in extreme brain iron overload.
• To compare the performance of various R2* and QSM algorithms in patients with aceruloplasminemia (ACP).
• To investigate the impact of different QSM referencing strategies on susceptibility measurements in ACP.

Main Methods:

• Acquisition of a 3D multiecho gradient-echo sequence for R2* and QSM.
• Comparison of six R2* and six QSM algorithms in three ACP patients and three healthy controls.
• Assessment of R2* and QSM values in specific brain regions (caudate nucleus, putamen, globus pallidus, thalamus) with varying QSM referencing methods.

Main Results:

• Significant variability in R2* values across algorithms, especially in the putamen.
• QSM susceptibility values were significantly influenced by both reference region choice and algorithm selection.
• Referencing to the whole brain in ACP patients resulted in lower QSM susceptibility values compared to referencing to cerebrospinal fluid.

Conclusions:

• Extreme brain iron overload amplifies variability in R2* and QSM measurements.
• QSM referencing is challenging in diffuse iron accumulation, necessitating multi-reference region analysis to mitigate bias.
• Algorithm and referencing choices are critical for accurate R2* and QSM measurements and clinical interpretation in severe brain iron overload.