Vascular Access: Comparison ofUS Guidance with the Sonic Flashlightand Conventional US in Phantoms1Wilson M. Chang, MD, PhDNikhil B. Amesur, MDRoberta L. Klatzky, PhDAlbert B. Zajko, MDGeorge D. Stetten, MD, PhDPurpose:To prospectively evaluate whether ultrasonography (US)-guided vascular access can be learned and performedfaster with the sonic flashlight than with conventional USand to demonstrate sonic flashlight–guided vascular ac-cess in a cadaver.Materials andMethods:Institutional review board approval and oral and writteninformed consent were obtained. The sonic flashlight re-places the standard US monitor with a real-time US imagethat appears to float beneath the skin and is displayedwhere it is scanned. In studies 1 and 2, participants per-formed sonic flashlight–guided needle insertion tasks invascular phantoms. In study 1, 16 participants (ninewomen, seven men) with no US experience performed 60simulated vascular access trials with sonic flashlight orconventional US guidance. With analysis of variance(ANOVA) and power-curve fitting, improvement withpractice rate and mean differences between techniquesand tasks were examined. In study 2, 14 female nurses(mean age, 50.1 years) proficient with conventional USperformed simulated vascular access trials on three taskswith the sonic flashlight and conventional US. With ran-dom assignment, half the participants used the sonic flash-light first and half used conventional US first. Mean perfor-mance with each technique and that with each task werecompared by using ANOVA. In study 3, feasibility of sonicflashlight guidance for access to internal jugular and basilicveins was demonstrated in a cadaver.Results:For study 1, learning rates (ie, decrease in access timeover trials) did not differ for vascular access with sonicflashlight and conventional US. Overall, participantsachieved faster vascular access times with sonic flashlightguidance (P ⬍ .007). In study 2, participants performedprocedures faster overall with the sonic flashlight (P ⬍ .02)and found the sonic flashlight easier to use. In study 3,sonic flashlight– guided vascular access was gained in thecadaver.Conclusion:Learning and performance of vascular access were signifi-cantly faster with the sonic flashlight than with conven-tional US, and vascular access could be gained in a ca-daver; the sonic flashlight is ready for clinical trials.娀 RSNA, 2006Supplemental material:radiology.rsnajnls.org/cgi/content/full/241/3/771/DC11From the Department of Bioengineering, University ofPittsburgh, 749 Benedum Hall, Pittsburgh, PA 15261.From the 2004 RSNA Annual Meeting. Received Sep-tember 27, 2005; revision requested November 14;revision received December 21; accepted January 24,2006; final version accepted February 1. Supported byNational Institutes of Health grants 1-R01-EB00860-1and 1-R01-HL074285-01. Address correspondence toW.M.C. (e-mail: [email protected]).姝 RSNA, 2006ORIGINAL RESEARCH䡲EXPERIMENTAL STUDIESRadiology: Volume 241: Number 3—December 2006 771In most freehand ultrasonography(US)-guided interventional proce-dures, the US transducer is held inone hand, while the other hand guides aneedle into the desired target. Duringthe procedure, the operator’s eyes arefocused on the US image, which is dis-played away from the operating field.Some of the difficulty in learning US-guided procedures stems from the dis-placed sense of hand-eye coordination,which occurs when the operator has tolook away from the operating field tosee the display.To address this difficulty, some re-searchers have explored nonconventionalmethods for viewing the US image, pa-tient, instrument, and operator’s hands inone environment. Head-mounted displaysystems have been developed to display aUS image as if within the patient (1–4).Despite their promise, head-mounted dis-play systems have yet to overcome sub-stantial obstacles, including lag time,low resolution, limited field of view,weight, and expense. Furthermore, ifmultiple observers are cooperating in aprocedure or are involved in training,each observer requires a separate head-mounted display to observe the same insitu US image.The sonic flashlight, a device in de-velopment at our institution, displaysreal-time US images inside the patientwithout the use of positional tracking ora head-mounted display system (5,6).The sonic flashlight fixes the relative ge-ometry of the transducer, display, and ahalf-silvered mirror, which the operatorlooks through, to produce a virtual im-age of the US data inside the patient(Figs 1, 2). The US image appears tofloat beneath the surface of the skin. Itis a virtual image in the exact opticssense of the word. For all intents andpurposes, each pixel of the US imageemanates from its correct anatomic lo-cation within the patient, as if being illu-minated directly by the sonic flashlight(Fig 2).The sonic flashlight is viewpoint in-dependent, meaning that any or all us-ers looking through the mirror from anyvantage point will see the US imageproperly registered with the internalanatomy. The sonic flashlight mergesthe US image, the patient, the instru-ment, and the operator’s hands into onevisual environment and eliminates theneed to look away from the operatingfield. This simplifies US-guided inter-ventional procedures by allowing theuser to aim directly for the US image(Fig 3). It should be noted that photo-graphs cannot convey the very strongsense that the US image appears withinthe patient, as if emanating from its cor-rect location.We hypothesized that vascular ac-cess can be learned and performedfaster with the sonic flashlight than withconventional US. Thus, the purpose ofour study was to prospectively evaluatewhether US-guided vascular access canbe learned and performed faster withthe sonic flashlight than with conven-tional US and to demonstrate sonicflashlight–guided vascular access in acadaver.Materials and MethodsInstitutional review board approval wasobtained for studies involving humanparticipants, and informed consent wasobtained prior to enrollment in the stud-ies. The cadaver was obtained and usedin this study according to our institutionalguidelines, and no special consent wasotherwise required from the next of kin.Sonic Flashlight PrototypeThe sonic flashlight prototype is builtaround a Food and Drug Administra-tion–approved commercially available10-MHz US probe (Terason 2000; Ter-atech, Burlington, Mass), a small 44 ⫻33-mm flat-panel organic light-emittingdisplay