Magnetic resonance susceptibility weighted imaging in neurosurgery: current applications and future perspectives

Abstract

T he initial development of MR venography by Reichenbach et al. 90 laid the foundation for Haacke et al. 42 to apply the principles of MR venography in conventional MRI for broader usage in clinical and research settings. By utilizing magnitude and phase information, both of which are normally acquired from conventional MRI data, susceptibility weighted imaging (SWI) has an enhanced ability to detect microhemorrhages 4,12,26 and microvasculature. 26,27,41,92 It is a highly sensitive imaging modality able to depict magnetic substances, such as deoxygenated hemoglobin, with high contrast 42 and to help investigate neurological diseases, 82 grade tumors, 25,63 and assist in determining treatment or prognosis. 18,26,37,70,71,115 Over the past years, the SWI technique has found applications in the different fields of neurosurgery, namely neurooncology, vascular neurosurgery, neurotraumatolabbreviatioNs AVM = arteriovenous malformation; CCM = cerebral cavernous malformation; CMB = cerebral microbleed; CVS = cortical vessel sign; DAI = diffuse axonal injury; DBS = deep brain stimulation; DWI = diffusion-weighted imaging; GBM = glioblastoma multiforme; GCS = Glasgow Coma Scale; GPe = external globus pallidus; GPi = internal GP; GRE = gradient-recalled echo; ITSS = intratumoral susceptibility signal; mIP = minimum intensity projection; MRA = MR angiography; MS = multiple sclerosis; PD = proton density; PQ = percentagewise quantification; PWI = perfusion-weighted imaging; SN = substantia nigra; STN = subthalamic nucleus; SWI = susceptibility weighted imaging; TBI = traumatic brain injury; VM = vascular malformation. Susceptibility weighted imaging (SWI) is a relatively new imaging technique. Its high sensitivity to hemorrhagic components and ability to depict microvasculature by means of susceptibility effects within the veins allow for the accurate detection, grading, and monitoring of brain tumors. This imaging modality can also detect changes in blood flow to monitor stroke recovery and reveal specific subtypes of vascular malformations. In addition, small punctate lesions can be demonstrated with SWI, suggesting diffuse axonal injury, and the location of these lesions can help predict neurological outcome in patients. This imaging technique is also beneficial for applications in functional neurosurgery given its ability to clearly depict and differentiate deep midbrain nuclei and close submillimeter veins, both of which are necessary for presurgical planning of deep brain stimulation. By exploiting the magnetic susceptibilities of substances within the body, such as deoxyhemoglobin, calcium, and iron, SWI can clearly visualize the vasculature and hemorrhagic components even without the use of contrast agents. The high sensitivity of SWI relative to other imaging techniques in showing tumor vasculature and microhemorrhages suggests that it is an effective imaging modality that provides additional information not shown using conventional MRI. Despite SWI's clinical advantages, its implementation in MRI protocols is st...

Longitudinal assessment of rabbit renal fibrosis induced by unilateral ureteral obstruction using two‐dimensional susceptibility weighted imaging

“…[22][23][24][25] The technique was traditionally performed in the brain using 3D acquisition, which FIGURE 3: SWI fusion maps of left kidneys in rabbits obtained at baseline (1 ) and week 2 (2 ), week4 (3 ), week 6 (4 ), and week 8 (5 ) following UUO. [22][23][24][25] The technique was traditionally performed in the brain using 3D acquisition, which FIGURE 3: SWI fusion maps of left kidneys in rabbits obtained at baseline (1 ) and week 2 (2 ), week4 (3 ), week 6 (4 ), and week 8 (5 ) following UUO.…”

Advanced MRI for Pediatric Brain Tumors with Emphasis on Clinical Benefits

“…2), typical of high-grade tumors, based on signal difference between magnitude and phase images of SWI or by using quantitative susceptibility mapping (414243). Potential value of SWI in tumor grading in adults has been reported by using various evaluation methods, such as intratumoral susceptibility signals, hypointensity ratios, and a computational fractal-based method (43). In addition, treatment response can be predicted or monitored based on SWI findings in adult tumors (43).…”

“…Potential value of SWI in tumor grading in adults has been reported by using various evaluation methods, such as intratumoral susceptibility signals, hypointensity ratios, and a computational fractal-based method (43). In addition, treatment response can be predicted or monitored based on SWI findings in adult tumors (43). However, more studies to refine the clinical value of SWI in pediatric brain tumors are required.…”

QuickBrain MRI for the detection of acute pediatric traumatic brain injury

“…11,15,21 Past studies in adults evaluated MRI as a diagnostic modality for intracranial hemorrhage. 2,6,7,18 MRI studies that include specific sequences, such as susceptibility-weighted imaging (SWI) or gradient echo (GRE), are highly accurate for detecting blood while adding only minutes to the acquisition time;…”