Preconditioned water-fat total field inversion: Application to spine quantitative susceptibility mapping

Area of Science:

• Medical Imaging
• Quantitative Susceptibility Mapping (QSM)
• Biophysics

Background:

• Quantitative Susceptibility Mapping (QSM) is crucial for analyzing tissue magnetic susceptibility.
• Existing methods like Local Field Inversion (LFI) and Total Field Inversion (TFI) face challenges with artifacts in water-fat regions.
• Accurate differentiation of bone lesions in the spine is vital for patient diagnosis and treatment.

Purpose of the Study:

• To develop a preconditioned water-fat total field inversion (wfTFI) algorithm for direct susceptibility map estimation.
• To evaluate the performance of the wfTFI QSM method against LFI and TFI in spinal imaging.
• To assess the diagnostic capability of wfTFI in distinguishing osteoblastic from osteolytic bone changes.

Main Methods:

• Developed a novel wfTFI algorithm utilizing complex multi-echo gradient echo data.
• Conducted numerical simulations and in vivo spine imaging on a healthy volunteer and 10 patients.
• Compared wfTFI with LFI and TFI methods, using CT scans as a reference for lesion characterization.

Main Results:

• wfTFI demonstrated reduced normalized root mean square error in simulations compared to LFI and TFI.
• In vivo wfTFI susceptibility maps exhibited fewer background field removal artifacts, noise, and streaking.
• wfTFI significantly increased diagnostic confidence in differentiating spinal lesions (p = .012) compared to LFI.

Conclusions:

• The wfTFI method effectively minimizes background field removal artifacts, noise amplification, and streaking in water-fat regions.
• wfTFI offers superior differentiation of osteoblastic and osteolytic changes in patients with metastatic bone disease.
• This advanced QSM technique holds promise for improved spinal imaging diagnostics.