J Kovoor - PowerPoint Presentation

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J Kovoor1, D Wang2, T Moritani1, A Capizzano1, J Kademian1, J Kim31University of Iowa Hospitals and Clinics, Iowa City, IA2Siemens Medical Solutions, Minneapolis, MN3University of Illinois at Chicago, Chicago, IL

Quantitative susceptibility mapping in detection of cerebral microbleeds in cerebral amyloid angiopathy

Poster #:

EP-60Slide2

IntroductionCerebral 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. Slide3

PurposeTo 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. Slide4

Materials

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

ImagingSlide5

Materials

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. Slide6

MethodsQuantitative 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 R2014bRegion of interest (ROI) measures of QSM at amyloid plaques and site of IPH were performed using ImageJ software. Slide7

MethodsQSM processing steps :Generating brain masksPhase reconstruction from multichannel phased array coil imagesUnwrap phase : Fourier-domain Laplacian operatorsRemoval of background

fields : Projection onto Dipole Fields (PDF) method

Local susceptibility mapping

: Morphology Enabled Dipole Inversion

(MEDI) method

Slide8

Qsm processing Pipeline

Mask image

Phase data

Background field

removal

QSM with morphology enabled

dipole inversion (MEDI)

Phase unwrapping

Magnitude dataSlide9

T2*-weighted GREQSM

Case 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 depositionSlide10

CASE-2 70 year old woman with history of hypertension and hyperlipidemia, who presented with acute onset language difficulties

CT T1WI T2WISlide11

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 GRESlide12

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.Slide13

QSMT2*-weighted GRECase 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 wallSlide14

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 Slide15

mIP SWIQSM

Case 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 QSMSlide16

ResultsQSM 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). Slide17

DISCUSSIONWhile 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. Slide18

ConclusionWe 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. Slide19

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