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New Non-Contrast MR Techniquessyngo NATIVE and syngo ASLOne step ahead with Inline Technology

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MR angiography and Siemens

Contrast-Enhanced Magnetic ResonanceAngiography (ce-MRA) remains the goldstandard for evaluating vasculature inMR as it enables high spatial andtemporal resolution with extremely fastimaging times. Siemens technologicalinnovations in angiography along withthe implementation of stronger gradientshas pushed imaging times to secondsinstead of minutes. High resolutionultrafast ce-MRA techniques fromSiemens are in routine clinical usagetoday along with improved workflowwith Siemens unique inline processing,subtraction and image composingspeeding up exam time. Innovativeapplications like syngo TWIST and syngoNATIVE now provide the user flexibilityof choice of technique to do MRangiography. syngo NATIVE enablesexcellent non-contrast angiographyimaging and reproducible results.

NSF (Nephrogenic Systemic Fibrosis)and changes in hospital policies

The use of injected contrast media hascome under scrutiny as the commoncontrast agents containing gadoliniumhave been linked to a condition calledNephrogenic Systemic Fibrosis (NSF) thatcan occur in patients with renalinsufficiency. The Food and Drug

Administration issued new-boxedwarnings for all manufactures ofgadolinium, which stated that patientswith severe kidney insufficiency whoreceive these agents are at risk fordeveloping NSF. Their recommendationsfurther state that facilities should avoiduse of gadolinium in patients with knownrisks for developing NSF unless thediagnostic information is essential andcannot be obtained with a non-contrastenhanced MR or other diagnosticprocedures. The FDA also stated thatfacilities should assess renal dysfunctionprior to administration of gadolinium aswell as not exceed recommended doses.Go to www.FDA.gov for more informationon gadolinium-containing contrast agents.

Due to recent events involving NSF andgadolinium, facilities such as New YorkUniversity Hospital have implemented ascreening process for those patients atrisk and modified their routine writtenconsent form. NYU assesses for renaldysfunction prior to administration ofMR contrast agents to identify patientsat risk for renal insufficiency and therebypotentially at risk for developing NSF.The risk factors include increasedserum creatinine, history of renaldisease, acute renal failure or recent renalsurgery, proteinuria, diabetes mellitus,hypertension, gout or recent intake ofnephrotoxic drugs. Documentation ofrecent BUN, creatinine and estimatedGlomerular Filtration Rate (GFR) are

obtained in patients who are at risk forrenal insufficiency. NYU’s departmentalpolicy for administration of MR contrastagent based on estimated GFR (calculatedusing the MDRD equation) is as follows:

eGFR >60 (mL/min/1.73 m2)No restriction for administrationof contrast.

eGFR >30-60Discuss with the patient the risksof administration of contrast andconsider using low dose.

eGFR 15-30Discuss risks and benefits withreferring physician, nephrologistand patient. Consider using lowdose but not recommended.

eGFR <15 or on dialysisAvoid administration of contrastunless benefits outweigh risks basedon assessment of the referringphysicians, nephrologists andradiologist. Peritoneal dialysis isan absolute contraindication.

NYU utilizes a non-contrast angiographytechnique called syngo NATIVE whenthese patients cannot have contrast.When low dose contrast is indicated,NYU utilizes syngo TWIST (Time-resolvedAngiography With Stochastic Trajectories),a new versatile high-resolutionangiography technique that furtherimproves time-resolved ce-MRA.

New Non-Contrast MR Techniquessyngo NATIVE and syngo ASL

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syngo TWIST

The new k-space coverage in syngoTWIST provides the user greaterflexibility in tailoring temporal andspatial resolution for dynamic MRimaging (Figure 1). syngo TWIST is up to10 times faster* compared to a standard,full k-space version of dynamic imaging.Excellent background suppression ascompared to other available techniquesresults in accurate and reproduciblediagnostic information even with smalleramounts of contrast agent.

The key clinical benefits ofsyngo TWIST are:

• Scalable temporal resolution• Workflow efficient ultrafast

technique• Lower cost and improvements in

diagnostic confidence as additionalhigh-res scan can be acquired in thesame setting

• Increased speed• Head-to-toe applications• Improved image quality• Multiple very small dose contrast

injections are possible to capturedynamic processes

Demand for non-contrastangiography techniques

Utilization for Contrast-EnhancedMagnetic Resonance Angiography (CEMRA) has been affected by the FDA’s newwarning. Currently, facilities performingMRA examinations utilizing gadoliniumdesire non-contrast angiographyapplications as an alternative backupfor patients at risk for developing NSF.

Current MRA techniquesIn Magnetic Resonance Imaging, severalphysical effects of flowing blood areexploited to image the vessels withoutinjection of contrast. Traditional non-contrast techniques encompass:

• Time of Flight MRA (ToF MRA) —(Figure 2A) Contrast mechanism isbased on exchanging the signal frominflowing blood during themeasurement.

• Phase Contrast MRA (PC MRA)—(Figure 2B) Contrast mechanism isbased on the change in phase due tomotion or flow.

These techniques are adequate forintra- and extra-cranial circulation.

New non-contrast MR techniques

Siemens is the leader in InnovativeApplications and Innovative Workflowwith the most comprehensive contrastand non-contrast angiography offeringswith the flexibility to fit every clinicalscenario. Due to extensive researchcollaborations, Siemens has developedmultiple non-contrast techniqueslike syngo NATIVE and syngo ASL forclinical need.

syngo NATIVE

For non-contrast MR AngiographySiemens currently offers two techniquesunder the category of NATIVE (Non-contrast MRA of ArTerIes and Veins)—syngo NATIVE TrueFISP and syngoNATIVE SPACE.

syngo NATIVE TrueFISPsyngo NATIVE TrueFISP is based on thesequence TrueFISP (True Fast Imagingwith Steady state Precession) which is abalanced steady state gradient echotechnique. The contrast mechanism forsyngo NATIVE TrueFISP comes from thepreparation of the imaging volume witha spatially selective inversion pulse,resulting in the suppression of stationarytissue within the imaging volume andsuppression of signal from blood in the

Figure 1: syngo TWIST, MAGNETOM Avanto.

*Data on file.

Figure 2A: Time of Flight (ToF).Figure 2B: Phase Contrast (PC).

2A

2B

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enables dynamic angiography—forexample, in the lower legs (Figure 4).

Non-contrast MR perfusion studies—syngo ASL (Arterial Spin Labeling)

Siemens has been at the forefront inother non-contrast techniques beyondangiography. Arterial Spin Labeling(ASL) is an MR technique using thewater in arterial blood as an endogenouscontrast agent to evaluate perfusionnon-invasively. ASL provides uniqueinsight into human brain perfusion andfunction physiology by evaluatingcerebral blood flow (CBF). ASL is capableof high spatial resolution perfusionimaging, making the technique veryappealing in the evaluation of stroke,tumors, degenerative diseases andepilepsy, but also in basic neuroscience,e.g. for studies of functional CBF changes.Siemens is proud to introduce syngo ASL,powered by Tim (Total imaging matrix),thereby allowing the use of noncontrastenhanced perfusion imaging in both theclinical and research settings. (Figure 5)

Tim technology

syngo NATIVE and syngo ASL arepowered by Tim (Total imaging matrix).

Tim is the solution that addresses thereal needs of today’s clinical MRIenvironment. Tim provides the flexibilityto scan any part of the body withoutinterrupting the exam for coil or patientrepositioning. Tim is also the first RFtechnology optimized for use withparallel imaging.

Conclusions

Siemens technological innovationsin angiography along with theimplementation of stronger gradientshas pushed imaging times to secondsinstead of minutes. High resolutionultrafast ce-MRA techniques from Siemensare in routine clinical usage. Improvedworkflow with Siemens unique inlineprocessing, subtraction and imagecomposing speeds up exam time.Innovative applications like syngo TWISTand syngo NATIVE provide the userflexibility of choice of technique to doMR angiography in any clinical scenario.syngo NATIVE enables excellent non-contrast angiography imaging and is anexcellent alternative for patients in whomcontrast material needs to be avoided.With Tim and inline processing, non-contrast MRA, head-to-toe is easy anddemonstrates excellent image quality.

imaging volume (e.g. venous blood).Blood which flows into the imagingvolume during the inversion time has thesame high signal characteristics exhibitedin conventional TrueFISP. The contrast isfurther enhanced by the suppression ofthe background by the inversion pulse.The sequence can be made selective forarteries or veins by appropriatepositioning of the inversion pulse, whichcan be positioned independently fromthe imaging volume. The sequenceaccommodates 3D, 2D, breath-hold,PACE (Prospective Acquisition andCorEction) navigated and respiratorytriggered approaches depending onclinical environment (Figure 3).

syngo NATIVE SPACE—Siemens exclusivesyngo NATIVE SPACE is based on theSPACE technique which is a modifiedvariable flip angle 3D Turbo Spin Echosequence in which the contrastmechanism for visualizing vessels is basedon the difference in intravascular signalbetween maximal and minimal flowduring the cardiac cycle. The subtractedimage is calculated in-line and with inlineMIP generation, instantaneous clinicalresults are produced for completelynon-invasive MR angiography, furtherimproving workflow at the scanner. Thesyngo NATIVE SPACE technique can alsoaccommodate multi phase imaging that

Figure 4: syngo NATIVE SPACE. Figure 5: Pulsed ASL perfusion with 3D PACE. Single Shot EPIpulsed arterial spin labeling sequence (Q2TIPS).

Figure 3: syngo NATIVE TrueFISP.

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Head to Toe Coverage withNon-Contrast Techniques

Whole body ce-MRA with Tim

syngo ASL

syngo NATIVE SPACE syngo NATIVE TrueFISP

syngo NATIVE TrueFISP

syngo NATIVE SPACEsyngo NATIVE SPACE

NEW 3D Time of Flight 2D ToF Carotids

HeadquartersSiemens Medical Solutions USA, Inc.51 Valley Stream ParkwayMalvern, PA 19355-1406 USATelephone: 1-888-826-9702

Contact Address GermanySiemens AG, Medical SolutionsHenkestr. 127, D-91052 ErlangenGermanyTelephone: +49 9131 84-0www.siemens.com/medical

Contact Address USASiemens Medical Solutions USA, Inc.Magnetic Resonance Division51 Valley Stream ParkwayMalvern, PA 19355-1406 USATelephone: 1-888-826-9702

www.usa.siemens.com/healthcare

On account of certain regional limitations ofsales rights and service availability, we cannotguarantee that all products included in thisbrochure are available through the Siemenssales organization worldwide. Availability andpackaging may vary by country and is subjectto change without prior notice. Some/all ofthe features and products described hereinmay not be available in the United States.

The information in this document containsgeneral technical descriptions of specificationsand options as well as standard and optionalfeatures which do not always have to be presentin individual 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 thisdocument may vary within defined tolerances.Original images always lose a certain amountof detail when reproduced.

© 1.2008, Siemens Medical Solutions USA, Inc.Order No. A91MR-1100-34C-7600Printed in USA