Official Proceedings - AIUM

American Institute of Ultrasound in Medicine Proceedings J Ultrasound Med 32(suppl):S1–S134, 2013This session will discuss combining modalities for challenging clinicaldilemmas in both urgent and nonurgent settings. The speakers will reviewa variety of topics that illustrate when ultrasound alone is sufficientfor diagnosis and when obtaining additional clinically useful informationfrom computed tomography and/or magnetic resonance imaging is optimal.These topics include the enlarged uterus, uterine anomalies, adnexaltorsion, pelvic inflammation of gynecologic origin, pelvic lesions secondaryto bowel disease, pelvic malignancy, evaluation of pelvic pain inpregnancy, and biopsy/aspiration of pelvic lesions. The lessons of thissession will be reinforced by means of a series of “test” cases using audienceparticipation.Hemodialysis Vascular AccessModerator: John Blebea, MD, MBAFlow Measurement to Predict Access FailureDavid Vilkomerson DVX, LLC, Princeton, New Jersey USAprompting the United States Food and Drug Administration to issue a“black box” for both of the commercially available perflutren-containingUS contrast agents (Definity and Optison), warning of risks of serious cardiopulmonaryreactions, and contraindicating their use in patients withcritical cardiopulmonary conditions. Considerable debate about the safety,risks, and benefits of US contrast agents ensued and prompted the publicationof numerous single- and multi-center retrospective and prospectiveanalyses, all demonstrating a good safety profile, with a favorable balanceof risks and benefits, comparable to, or better than, contrast agent use inother imaging modalities. Subsequently, although the black box remains,several revisions of product labeling have occurred, which have resultedin softening and/or removal of previous warnings and precautions, simplificationof contraindications to the original concerns regarding intracardiacshunting and known hypersensitivity, and expansion of indicationssuch that stress imaging was no longer an exclusion. In summary, US contrastagents have a favorable risk/benefit profile in patients requiring improvedendocardial visualization for rest and stress echocardiographicimaging, and use for this purpose is currently required by US accreditationorganizations.Blood flow is high when a graft is placed and goes to zero whenit clots. Stenoses almost always cause this reduction in flow. It seems reasonable,then, to measure graft flow and, when it falls to a level indicatingan impending clot, to treat the stenoses and prevent the graft failure. Tenyears ago, 2 randomized clinical trials were undertaken to establish the validityof this approach; both showed that monthly flow surveillance led tomore procedures but failed to reduce graft failures. Many suspected thatmore frequent flow measurements might be more effective. We developed,with National Institutes of Health/National Institute of Diabetes andDigestive and Kidney Diseases Small Business Innovation Research funding,a Doppler ultrasound system especially for weekly graft flow measurement.In an observation-only phase, the instrument was shown to bequick, inexpensive, and accurate in predicting graft failure. On the basis ofthese results, a clinical trial was begun. Dialysis volunteers were randomizedto a surveillance group, who had their graft flow measured andrecorded every week, and a control group, who continued to receive conventionaltreatment, including monthly flow measurements. After 21months, in the surveillance group measured “per protocol,” only 8% hadgrafts that failed and a procedure rate similar to the control group. On an“intent-to-treat” basis, however, the clinical trial failed: skipped measurements,failure to notice graft flows showing impending clotting, and delaysin treatment prevented the trial from meeting its goal of reduced graftfailures. However, having a record of the graft flow after the missed signsallowed us to determine the important parameter of how fast grafts clotafter reaching the impending failure criteria: about 70% of grafts clotted inless than a month after meeting the criteria. The most common interval betweenthe signs of impending failure and thrombosis was 1 week. Lesson1: Monthly flow surveillance can never, no matter the method, significantlyreduce graft failures. Another result of having weekly flow data was beingable to correlate postintervention graft flow with the succeeding graft history.Lesson 2: If postintervention flow is 950 mL/min, >70% will be patent after 21 months.New Horizons in Contrast UltrasoundModerator: Paul Dayton, PhDSafety Aspects of Contrast UltrasoundSharon Mulvagh Medicine, Mayo Clinic, Rochester, MinnesotaUSAIn the mid to late 2000s, several years after approval of ultrasound(US) contrast agents for enhancement of endocardial borderdefinition and improved feasibility and quality of echocardiographic examinations,postmarketing surveillance suggested a “safety signal,”S6Review of Molecular ImagingJoshua Rychak Targeson, Inc, San Diego, California USAContrast ultrasound is an emerging technique for imaging tumorprogression, both in clinical and research settings. In particular, targetedmicrobubbles are now being used as molecular contrast agents for molecularimaging of angiogenesis, thrombosis, and inflammatory disease.This presentation will review developments in the field over the pastdecade and attempt to trace the path from proof of concept to the introductionof commercial formulations for research and clinical use. Early incarnationsof microbubbles for molecular imaging used antibody-targetingligands conjugated using a biotin-avidin scheme. This system has provedto be remarkably robust and, with several modifications, has emerged intoseveral widely used commercial products for small-animal imaging. Extendingultrasound molecular imaging to larger research species presentssome challenges: antibodies are not always readily available to the desiredmolecular target for rabbits, canines, and swine, and the large volume ofmicrobubble product required per dose makes cost a constraint. The useof small-molecule ligands that offer activity in a variety of species (andwhich can generally be made at low cost) can overcome this limitation. Replacementof biotin-avidin conjugation with covalent-coupling chemistriescan further reduce the cost and improve the consistency of the microbubbleproduct. Selection of conjugation chemistry, in addition to the ligandand shell components, proves to be an important aspect when translatingto human use. In addition to their incarnation as reagents for biomedicalresearch, the first generation of ultrasound molecular imaging agents arenow entering clinical trials.Microvascular MappingPaul Dayton, 1 * Ryan Gessner, 1 Stephen Aylward 21Biomedical Engineering, University of North Carolina, ChapelHill, North Carolina USA; 2 Kitware, Inc, Carrboro, NorthCarolina USAMicrobubbles are unique as ultrasound contrast agents in thatthey are constrained to the microvascular space due to their large size, andthey can be detected with high sensitivity due to their unique echo signatures.Through application of transducers and imaging strategies optimizedto achieve high resolution and high signal to noise coupled with 3D approaches,it is possible to obtain maps of microvascular structures associatedwith healthy and pathologic tissue. It is well known that angiogenicprocesses involved in rapidly growing tumors promote increased vesseldensity, tortuosity, and other structural abnormalities. Using vessel segmentationmethods, vessel patterns can be identified and characterizedfrom contrast ultrasound data. We demonstrate that these “microvascularmaps” can be used to characterize tissue volumes as tumor bearing or