Laser Needle Guide for the Sonic Flashlight David Wang 1,3,4, Bing Wu 2,3, George Stetten 1,2,3,4,5 1 Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh PA 15213, USA 2 Department of Psychology, Carnegie Mellon University, Pittsburgh PA 15213, USA 3 Robotics Institute, Carnegie Mellon University, Pittsburgh PA 15213, USA 4 University of Pittsburgh Medical Center, Pittsburgh PA 15261, USA 5 Department of Biomedical Engineering, University of Pittsburgh, Pittsburgh PA 15261, USA Out-of-Plane Ultrasound Guided Needle Insertion is Difficult Test with Water-tank Phantom Our Objective References Conclusion Implementation of Laser Guidance In ultrasound guided vascular access, it is often necessary to insert a needle outside the plane of an ultrasound scan. The tip of the needle is not visible until it reaches the plane of the ultrasound scan. Thus, a potential exists for the needle to miss the target, requiring multiple needle insertions and unnecessary trauma to the patient. Hence a method to accurately guide the needle to the target would be valuable. The proposed path for the needle insertion is shown to the operator by aiming a low-intensity laser at the virtual target in the SF. T he point where the needle will enter the body is indicated by the laser spot on the skin. A part of the laser beam reflects off the mirror, creating another spot on the flat panel monitor, whose virtual image shows the intersection of the path with the ultrasound slice at the location of the proposed target. Whereas the Sonic Flashlight with unaltered needles has shown good accuracy for relatively shallow targets such as veins in the arm, the addition of laser guidance may be appropriate for deeper procedures such as biopsies of the liver or kidney. 1.“PunctSURE Vascular Access Imaging”, html, “Site-Rite Ultrasound System”, G. Stetten, V. Chib, “Overlaying Ultrasound Images on Direct Vision,” Journal of Ultrasound in Medicine vol. 20, no. 3, pp , Stetten G, “System and Method for Location-Merging of Real-Time Tomographic Slice Images with Human Vision,” U.S. Patent no. 6,599,247, issue date, July 29, Wu, B, Klatzky, RL, Shelton, D & Stetten G (2005) Psychophysical Evaluation of In-Situ Ultrasound Visualization. IEEE Transactions on Visualization and Computer Graphics (In press). Two lasers are used so that the mid-point of the two spots in the virtual image determines the destination of the needle. Laser Needle Guidance The RTTR system functions by fixing the relative geometry of the ultrasound transducer, the display, and a half-silvered mirror to produce a virtual image at the scanned anatomy within the body. Through the mirror, the ultrasound image is seen as if it "shines out" from the probe and illuminates the inner tissue. Thus the system has been referred to as the Sonic Flashlight (SF). By keeping the lasers aimed on either side of the target, we successfully and very easily reached the target (depth: 5cm; size: 1 cm). In the picture to the right, beams from two lasers mounted along a needle strike the mirror (4) splitting into two sets of beams. The reflected beams reach the flat panel monitor (1) while the direct beams penetrate the mirror to produce bright spots on the surface of the water tank (3). The virtual image (2) of the spots (1) on the flat panel monitor accurately flank the target at its actual location in the water tank Flat- Panel Monitor Half- Silvered Mirror Laser 1 Laser 2 Needle The laser generators are placed parallel and as close as possible to the needle so that they flank the needle destination. There are only a few commercial guidance systems for out-of-plane needle insertion. They restrict the insertion to a fixed number of pre- determined angles (Site-Rite TM [2]) or to a second orthogonal plane (PunctSURE TM [1]). To overcome these problems, we developed a laser guidance system that offers users the ability to perform the insertion along an arbitrary path. The system is based on a device called the Sonic Flashlight [3, 4], which uses a technique called Real- Time Tomographic Reflection, described below. (  IEEE Reproduced with permission from [5]) Sonic Flashlight Virtual Image Needle Laser Guidance Real-Time Tomographic Reflection