J Kovoor1, D Wang2, T Moritani1, A Capizzano1, J Kademian1, J Kim3

1University of Iowa Hospitals and Clinics, Iowa City, IA2Siemens Medical Solutions, Minneapolis, MN

3University of Illinois at Chicago, Chicago, IL

QUANTITATIVE SUSCEPTIBILITY MAPPING IN DETECTION OF CEREBRAL MICROBLEEDS

IN CEREBRAL AMYLOID ANGIOPATHY

Poster #: EP-60

INTRODUCTION

• Cerebral microbleeds associated with cerebral amyloid angiopathy (CAA) are common neuroimaging finding leading to detrimental sequelae in elderly subjects.

• Quantitative susceptibility mapping (QSM) - a novel technique that allows quantifying brain iron concentration in vivo.

PURPOSE

• To evaluate the feasibility and clinical utility of QSM with potential diagnostic value as a complementary tool with conventional gradient-recalled echo sequence (GRE) magnitude imaging and susceptibility weighted imaging (SWI) in CAA.

M AT E R I A L S

• Subjects

Case Age/Gender Clinical Presentation CAA Diagnosis

1 70/F Left occipital IPH Pathology

2 70/F Left temporal IPH Imaging

3 76/F Left frontal IPH Pathology

4 82/F Right temporooccipital IPH Imaging

M AT E R I A L S

• First-line emergency head CT exam

• MRI Acquisition• 1.5 T (case 1, 2, 3) and 3 T (case 4) clinical scanners

• Imaging sequences

• Routine clinical protocol

• TSE T1/T2 WI, 2D GRE T2* WI, and 3D fast low-angle shot (FLASH) SWI with magnitude and phase image reconstructions.

METHODS

• Quantitative susceptibility mapping was retrospectively reconstructed from SWI data.

• QSM was reconstructed by using MEDI Toolbox (http://weill.cornell.edu/mri/pages/qsm.html) on MATLAB R2014b

• Region of interest (ROI) measures of QSM at amyloid plaques and site of IPH were performed using ImageJ software.

METHODS

• QSM processing steps :

• Generating brain masks

• Phase reconstruction from multichannel phased array coil images

• Unwrap phase : Fourier-domain Laplacian operators

• Removal of background fields : Projection onto Dipole Fields (PDF) method

• Local susceptibility mapping : Morphology Enabled Dipole Inversion (MEDI) method

QSM PROCESSING PIPELINE

Mask image

Phase data Background fieldremoval

QSM with morphology enabled dipole inversion (MEDI)

Phase unwrappingMagnitude data

T2*-weighted GRE QSMCase 1 (70 YO, FEMALE)

GRE shows multiple punctate foci of blooming bilaterally and QSM separates blooming from the lesion with microbleeds as hyperintensity. The margins of the lesions are more conspicuous with less blooming. Bilateral basal ganglia shows hyperintensity from iron deposition

CASE-2 70 YEAR OLD WOMAN WITH HISTORY OF HYPERTENSION AND HYPERLIPIDEMIA, WHO PRESENTED WITH ACUTE ONSET LANGUAGE DIFFICULTIES

CT T1WI T2WI

QSMT2*-weighted GRE

Calcifications

Case 2 (70 YO, FEMALE)

GRE shows choroid plexus calcifications as hypointensity lesions with blooming while QSM shows calcifications as hypointensity while the areas of iron deposition as hyperintense areas with distinct margins. Basal ganglia iron deposition seen on QSM but not well defined on GRE

CASE3 76 YEAR-OLD FEMALE WITH PAST MEDICAL HISTORY OF HTN, CHF, DM 2, CKD (UNKNOWN BASELINE) WHO PRESENTS FROM OUTSIDE HOSPITAL WITH LEFT FRONTAL INTRAPARENCHYMAL HEMORRHAGE. PRESENTED TO OSH AFTER DECLINE IN MENTAL STATUS WITH APHASIA, INCREASING SOMNOLENCE AND CONFUSION

CAA was confirmed by surgical histopathology.

QSMT2*-weighted GRE

Case 3 (76 YO, FEMALE)

GRE and QSM showing intraparenchymal bleed in left basifrontal region, which is seen as hypointensity on QSM with distinct margins and GRE shows blooming. Also seen are basal ganglia iron deposition and intraventricular hemorrhage. Arrow points to calcification in MCA vessel wall

CASE-4 82-YEAR-OLD FEMALE WITH HYPERLIPIDEMIA, PREVIOUS UTERINE CANCER TREATED WITH RESECTION IN 1997 AND RADIATION THERAPY. SHE PRESENTS WITH A FOUR-DAY PERIOD OF ERRATIC BEHAVIOR.

T1WI T2WI T2*GE

mIP SWI QSMCase 4 (82 YO, FEMALE)

GRE limited by blooming, while the QSM differentiates diamagnetic and paramagnetic deposition. Rt temporal lobe and right occipital bleed with leptomeningeal hemosiderosis seen as hypointentensity with blooming on mIPSWI. On QSM, the corresponding areas are seen as hyperintensity with distinct margins and the superficial siderosis is appreciated on QSM and not on SWI. Basal ganglia iron depositiion and chorod plexus calcification appearing hypointense on SWI, but appearing hyperintense and hypointense respectively on QSM

RESULTS

• QSM clearly distinguished paramagnetic CMB from diamagnetic mineral deposition

• Improved diagnostic accuracy and marginal definition of the lesions by elimination of surrounding blooming effect.

• Areas of IPH manifested with high signal on T1 and large blooming effect showed higher value of QSM measure (mean=17051.38, SD=1897.12) than brain structures with physiologic iron distribution (i.e. caudate nucleus, putamen, globus pallidus, red nucleus, substantia nigra, and dentate nucleus). QSM measures of CMB were highly variable (mean=7855.50, SD=5295.45).

DISCUSSION

• While T2*WI does not allow differentiation of diamagnetic and paramagnetic substances, QSM overcomes this problem by utilizing both magnitude and phase data and performing a dipole deconvolution.

• Limited pilot study - we were unable to quantify iron concentration distinctively from CMB in CAA versus amyloid plaques.

• Further investigation on iron overload in CAA may be useful to predict future hemorrhagic risk of the disease.

CONCLUSION

• We demonstrated feasibility of QSM in CAA with CBM from routine clinical MRI studies.

• QSM allowed improved diagnostic accuracy of CMB with an advantage of paramagnetic specificity.

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