MAC Print Syngo ASL

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syngo ASL. Powered by Tim.Non-contrast enhanced perfusionimagingMAGNETOM Applications MAC Print


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syngo ASL. Powered by Tim.Non-contrast enhanced perfusion imaging

Arterial Spin Labeling (ASL) is an MR tech-nique using the water in arterial blood asan endogenous contrast agent to evaluateperfusion non-invasively. ASL providesunique insight into human brain perfusionand function physiology by evaluatingcerebral blood flow (CBF). ASL is capableof high spatial resolution perfusion imag-ing, making the technique very appealingin the evaluation of stroke, tumors, degen-erative diseases, epilepsy but also in basicneuroscience, e.g. for studies of functionalCBF changes. Siemens is proud to introducesyngo ASL, powered by Tim (Total imagingmatrix), thereby allowing the use of non-contrast enhanced perfusion imaging inboth the clinical and research settings.

Principles of Arterial Spin Labeling

Initially the techniques used for determiningcerebral blood flow were rather invasive

and involved the use of exogenous contrastagents, such as 15 O labeled radiotracer inPositron Emission Tomography (PET).With MRI, brain perfusion studies have beencommonly performed using exogenousGadolinium-based contrast agent. The prin-ciples behind ASL are quite similar to thoseutilizing exogenous contrast agents. How-ever, ASL is completely non-invasive: noradiation and no injection of contrast media.

In ASL, first, arterial blood water is magneti-cally labeled just below the region of interestby applying a 180 degree radiofrequency(RF) inversion pulse. The result of this pulseis inversion of the net magnetization of theblood water. In other words, the water mol-ecules within the arterial blood are labeledmagnetically. After a period of time (calledthe transit time), the magnetically labeledwater flows into the region of interest whereit exchanges with tissue water. The inflow-ing inverted spins within the blood wateralter total tissue magnetization, reducingit and, consequently, the MR signal and im-age intensity. During this time, an image istaken (called the tag image).

The experiment is then repeated withoutlabeling the arterial blood to create anotherimage (called the control image). The tag-state is alternated with the control state,in which the magnetization of the arterialblood is not inverted. The control image andthe tag image are subtracted to producea perfusion image. This image will reflectthe amount of arterial blood delivered tothe slice within the transit time.

There are mainly two techniques for ASL;PASL (pulsed ASL) and CASL (ContinuousASL). In PASL, the RF pulse is applied in aspatially selective manner (region-specific).Consequently the inversion of the ar te-rial blood occurs over a specific area. PASLis particularly attractive for higher fieldstrengths as other ASL schemes such asCASL have to deal with the challengeof high Specific Absorption Rate (SAR).


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ost-stroke examination showing good correlation between ASL and contrast-enhanced CBF and TTP perfusion data.ote that Dark Fluid does not show yet the extent of the affected region. MAGNETOM Trio a Tim system. Courtesy of Xuanwu Hospital, CUMS, Beijing, P.R. China

syngo ASL acquired with matrix 64 x 64 and slice thickness 5 mm, fused in the Neuro 3D cardwith structural MR data.

2 TSE, DW EPI, ADC map and Dark Fluid images fused with the diffusion data and ASL again showing a considerably larger affected region. MAGNETOM Trio a Tim system.ourtesy of Xuanwu Hospital, CUMS, Beijing, P.R.China

Arterial Spin Labeling Applications

There are several applications for ASLimaging tumor and pediatric perfusionimaging being the primary. Other applica-tions include stroke, epilepsy, degenerativediseases such as dementia and Alzheimers

disease. ASL is also a great tool for function-al evaluation of the brain in combinationwith BOLD techniques. Changes in perfusionare more localized to the parenchyma,whereas BOLD changes are tied to theveins and venules.

syngo ASL implementation

Siemens implemented PASL. This new ap-plication, called syngo ASL makes use of theunique Parallel Imaging capabilities of Tim(Total imaging matrix) with the standard 12-channel Head Matrix coil as well as the 32-channel Head coil. syngo ASL is compatiblewith GRAPPA parallel acquisition technique.In order to make this advanced applicationmore efficient, Siemens has also enabledthe use of 3D PACE, prospective motion cor-rection for ASL, thereby enabling a higherrobustness of the technique.

ark Fluid rel. CBF ASL TTP

2 TSE Diffusion EPI Diffusion EPI ADC map Dark Fluid fused with Diffusion ASL


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On account of certain regional limitations ofsales rights and serv ice availability, we cannotguarantee that all products included in this bro-chure are available through the Siemens sales or-

ganization worldwide. Availability and packagingmay vary by country and is subject to changewithout prior notice. Some/All of the features andproducts described herein may not be available inthe United States.

All devices listed herein may not be licensed ac-cording to Canadian Medical Devices Regulations.

The information in this document contains ge-neral technical descriptions of specifications andoptions as well as standard and optional featureswhich do not always have to be present in indivi-dual cases.

Siemens reserves the right to modify the design,packaging, specifications and options describedherein without prior notice. Please contact yourlocal Siemens sales representative for the mostcurrent information.

Note: Any technical data contained in this docu-ment may vary within defined tolerances. Origi-nal images always lose a certain amount of detailwhen reproduced.

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