Bulk volume susceptibility difference between deoxyhemoglobin and oxyhemoglobin for HbA and HbS: A comparative study

Area of Science:

• Biophysics
• Medical Imaging
• Hematology

Background:

• Sickle cell anemia alters red blood cell morphology and oxygen affinity.
• Quantitative BOLD MRI assesses oxygen delivery and stroke risk in sickle cell anemia.
• BOLD signal relies on magnetic susceptibility difference ($$) between oxygenated and deoxygenated blood.

Purpose of the Study:

• To determine if the magnetic susceptibility difference ($$) of sickle hemoglobin differs from normal hemoglobin A (HbA).
• To validate the use of established $$ values in BOLD MRI for sickle cell anemia research.

Main Methods:

• Measured $$ in blood from sickle cell anemia patients and controls.
• Controlled for oxygen saturation, pH, PCO2, temperature, and magnetic field drift.
• Utilized Hill's equations to adjust for differing oxygen affinities of HbA, sickle hemoglobin, and HbF.

Main Results:

• The measured $$ values for HbA and sickle hemoglobin were not statistically significantly different.
• Assumptions included similar $$ for HbA and HbF, and $$ for sickle hemoglobin being 5/4 of HbA.

Conclusions:

• The magnetic susceptibility difference ($$) is comparable between normal and sickle hemoglobin.
• A single $$ value can be applied in quantitative BOLD MRI analysis for both HbA and sickle hemoglobin.