Rapid quantitative susceptibility mapping of intracerebral hemorrhage

Abstract

Background Quantitative susceptibility mapping (QSM) offers a means to track iron evolution in hemorrhage. However, standard QSM sequences have long acquisition times and are prone to motion artifact in hemorrhagic patients. Purpose To minimize motion artifact and acquisition time by performing rapid QSM in intracerebral hemorrhage (ICH) using single‐shot echo planar imaging (EPI). Study Type Prospective method evaluation. Population/Subjects Forty‐five hemorrhages were analyzed from 35 MRI exams obtained between February 2016 and March 2019 from 27 patients (14 male / 13 female, age: 71 ± 12 years) with confirmed primary ICH. Field Strength/Sequence 3T; susceptibility‐weighted imaging (SWI) with 4.54‐minute acquisition and 2D single‐shot gradient EPI with 0.45‐minute acquisition. Assessment Susceptibility maps were constructed from both methods. Measurement of ICH area and mean magnetic susceptibility were made manually by three independent observers. Motion artifacts were quantified using the magnitude signal ratio of artifact‐to‐brain tissue to classify into three categories: mild or no artifact, moderate artifact, or severe artifact. The cutoff for each category was determined by four observers. Statistical Tests Pearson's correlation coefficient and paired t‐test using α = 0.05 were used to compare results. Inter‐ and intraclass correlation was used to assess observer variability. Results Using 45 hemorrhages, the ICH regions measured on susceptibility maps obtained from EPI and SWI sequences had high correlation coefficients for area (R2 ≥ 0.97) and mean magnetic susceptibility (R2 ≥ 0.93) for all observers. The artifact‐to‐tissue ratio was significantly higher (P < 0.01) for SWI vs. EPI, and the standard deviation for the SWI method (SD = 0.05) was much larger than EPI (SD = 0.01). All observers' measurements showed high agreement. Data Conclusion Single‐shot EPI‐QSM enabled rapid measurement of ICH area and mean magnetic susceptibility, with reduced motion as compared with more standard SWI. EPI‐QSM requires minimal additional acquisition time and could be incorporated into iron tracking studies in ICH. Level of Evidence: 2 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;51:712–718.

QSM in canine model of acute cerebral ischemia: A pilot study

“…9, [15][16][17][18][19] QSM is a postprocessing technique that quantifies local tissue magnetic properties through the solution of the field-to-source problem. Previously, QSM has been utilized in multiple studies of pathological conditions involving iron, [20][21][22][23][24][25][26][27] calcifications, 21,23,28 and myelin. 22,29,30 Furthermore, there is a growing body of research on QSM applicability in cerebral ischemia involving preclinical models and patients.…”

Quantitative susceptibility mapping of carotid plaques using nonlinear total field inversion: Initial experience in patients with significant carotid stenosis

“…Another limitation is the relatively long scan time of the QSM sequence. More efficient k‐space sampling trajectories and the use of higher field strengths or better surface carotid coil designs to improve SNR can be used to reduce acquisition time. In addition, comparison with QSM approaches for dealing with a large dynamic range of susceptibilities, including the STAR‐QSM method, was not performed.…”

Editorial for “Quantitative Susceptibility Mapping for Staging Acute Cerebral Hemorrhages: Comparing the Conventional and Multi‐Echo Complex Total Field Inversion MR Methods”

“…Blood leakage into the brain parenchyma from ICH may generate accumulation of toxic iron, resulting in secondary inflammation and increased injury 2 . In ICH, the property of the accumulated hemoglobin evolves over time, from an initial diamagnetic form to various paramagnetic states as the lesion evolves 3 . Neuroimaging is essential for rapid diagnosis of cerebral hemorrhage and identification of the potential cause, therefore contributing to triage and treatment of patients 4 …”

“…MRI is better than CT techniques in staging ICH, particularly for visualizing chronic hemorrhages 4 . Moreover, mean ICH susceptibility has shown better separation of various stages of hemorrhage as compared with conventional T1‐ and T2‐weighted MRI 3 …”