QSM Analysis
Note
Under construction
Background and Theory
Susceptibility weighted imaging (SWI) is sensitive to both iron and myelin, and therefore SWI is used clinically to provide additional contrast to T1 and T2 weighted images.
Role of iron in the brain
Iron is involved in regulating electrons in metabolic processes, such as the Krebs cycle and oxidative phosphorylation. In addition, iron is also involved in oxygen transport in the brain via haemoglobin.
Role of myelin in the brain
Myelin forms a sheath around axons of neurons, which insulates the axons and increases the speed of electrical signal transmission.
Motivations for QSM
Iron accumulates in the brain with age and link to neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis.
Magnetic Susceptibility
Clinical Applications
Calcification
Question: how to tell difference between iron and calcification in susceptibility weighted images?
Higher concentrations would exhibit greater enhancement of the region.
Case study of patient with both calcification and bleeds
Depends on handedness of scanner, veins and bleeds may appear dark and calcifications may appear bright.
Need to check for dipole field pattern in sagittal or coronal plane, which will be much more evident around paramagnetic regions, as these have a larger susceptibility difference compared to the diamagnetic tissue.
Hypoxic Ischemic Encephalopathy
Subarachnoid haemorrhage
Subarachnoid haemorrhage refers to the bleeding in the subarachnoid space, usually from a ruptured aneurysm.
Workflow:
Iron deposited in the brain after subarachnoid haemorrhage around the Sylvian fissures.
Need to investigate the relationship of iron and brain volume changes.
Future work includes studying whether clinical outcome is more closely associated with baseline blood volume or iron deposition.
Superficial Siderosis
Hemosiderin deposited on the pial surface of the brain and/or spinal cord, as a result of chronic subarachnoid haemorrhage.
Deferiprone is an iron chelator that can be used to treat superficial siderosis.
There is a need to develop a workflow for rare clinical cases, such as superficial siderosis.
Workflow:
