Bone material analogues for PET/MRI phantoms.

Area of Science:

• Materials Science
• Biomedical Engineering
• Medical Imaging

Background:

• Developing accurate phantoms for simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) systems is crucial for image calibration and quality assurance.
• Existing bone analogues may not fully replicate the complex attenuation and magnetic resonance properties of human bone.

Purpose of the Study:

• To create novel bone material analogues for constructing phantoms specifically designed for simultaneous PET/MRI systems.
• To investigate the potential of plaster-based materials doped with various agents to simulate bone's physical characteristics.

Main Methods:

• Plaster was utilized as the base material for bone analogues.
• Varying concentrations of iodinated CT contrast, gadolinium-based MR contrast agents, and copper sulfate were incorporated to modulate attenuation and MRI properties (T1 and T2*).
• Attenuation was measured using CT and ⁶⁸Ge transmission scans, while MRI properties were assessed with quantitative ultrashort echo time pulse sequences.

Main Results:

• Undoped plaster exhibited similar 511 keV attenuation to cortical bone but had longer T1 and T2* relaxation times.
• Doping with iodinated contrast increased attenuation with minor MR property changes.
• Gadolinium chelate significantly reduced T1 and T2*, while copper sulfate selectively shortened T2* and achieved bone-like T1 and T2* values after drying.

Conclusions:

• Plaster doped with copper sulfate demonstrates significant promise as a bone material analogue for PET/MRI phantoms.
• This analogue effectively replicates the key MR properties (T1 and T2*) and 511 keV attenuation coefficient of human cortical bone.
• The developed material facilitates the creation of more accurate and reliable phantoms for simultaneous PET/MRI applications.