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Invited Talk I                      Invited Talk II

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•    Invited Talk I

       TitleMR image guided microwave ablation of liver tumors

-From a low field open-configuration system to a high field closed-bore system

       Speaker:  Shigehiro Morikawa

                        Biomedical MR Science Center, Shiga University of Medical Science

       Abstract:  Since 2000, we have experienced more than 300 clinical cases of MR image guided microwave ablation of liver tumors using a double doughnuts type open MR system, 0.5T GE SIGNA SP. This system enabled easy access to a patient and surgeons can accurately insert an MR-compatible microwave electrode into liver tumors while monitoring real time MR images. We have developed a custom made navigation system and MR compatible motorized manipulator. This procedure is quite feasible. However, this open MR system is very old and a successor model is not available. We need to consider the next step using a high field closed bore system.

    A high field MR system provides us better image quality, but access to a patient is limited. We need to consider the way to solve such problems. We are developing two measures. One solution will be the utilization of a long MR compatible fiberscope to reach the image center in the magnet. The other one will be a seamless navigation system between inside and outside the magnet. In this talk, I would like to present our developments for the next project of MR image guided surgical procedures using a closed bore system.

       Bio:  Shigehiro Morikawa graduated from Kyoto University, Faculty of Medicine and received a M.D. degree in 1975. After clinical training as a general surgeon at Kyoto University Hospital and Kitano Hospital, he received a Ph.D. degree from Kyoto University, Graduate School of Medicine (Surgery) in 1987. He has beenengaged inNMR research since 1989. He was an Associate Professor in 1994 at Molecular Neurobiology Research Center, Shiga University of Medical Science. He is currently a Professor in the Department of Fundamental Nursing (Morphology & Physiology) and Biomedical MR Science Center, Shiga University of Medical Science. He isconcurrently a Visiting Professor in the Department of Science and Engineering, Ritsumeikan University since 2002. His main research interests are biomedical MR science and MR image guided surgery.

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•    Invited Talk II

      TitleMechanisms and functions of visual illusions

      Speaker:  Akiyoshi Kitaoka

                       College of Letters, Ritsumeikan University

      Abstract:  Visual illusion refers to a phenomenon that the perception of an object or its properties is different from what it should ¡®objectively¡¯be. There are a variety of visual illusions including the geometrical illusion (shape illusion), color illusion, lightness illusion, motion illusion etc., depending on visual attributes. Mechanisms and functions are fairly understood for some illusions while not for others.

       The ¡®functional¡¯ illusion should be distinguished from the ¡®not-functional¡¯ illusion.To put it simply, the former is calledtrompe l¡¯oeil or ¡®damashie¡¯ in Japanese, while the latter is called ¡®sakushi¡¯ in Japanese. For example, the Ames room, a kind of trompe l¡¯oeil, can be understood in terms of competition between shape constancy and size constancy. Both pieces of constancy are functional. On the other hand, the ¡®Rotating snakes¡¯ illusion created by Kitaoka in 2003 shows illusory motion in a static image but cannot be accounted for in terms of any function. Actually sakushiis translated to visual illusion or optical illusion, but they are not identical. Moreover, mechanisms of sakushitend to be less distinct than those of trompel¡¯oiel.

       In this workshop, I will talk about mechanisms and functions of some illusions. One is the spiral illusion, in which concentric circles appear to be spirals. This illusion is explained with cooperation between orientation-selective neurons in V1 and spiral pattern-responding neurons in V4 (Kitaoka et al., 2001). Another is a motion illusion in a static image, in which the inset of low contrast appears to move in the same direction as the image motion that observers make. This illusion is explained in terms of the difference in visual latency between a high-contrast region and a low-contrast one (Kitaoka and Ashida, 2007). The former gives a shorter latency than the latter, giving apparent displacement within the image.

       The latest issue I have been studying for a couple of years is the Fraser-Wilcox illusion group. The Fraser-Wilcox illusion was proposed in 1979. However, it was not followed by subsequent research for no less than twenty years because of difficulty of reproduction.This problem was solved by Kitaoka and Ashida (2003) who separated one illusion from another. Since these two illusions cancel each other in the original Fraser-Wilcox illusion image, rearranging them so as to work together makes a strong illusion.I call it the ¡®optimized¡¯ Fraser-Wilcox illusion.

       At present, there are five types of the ¡®optimized¡¯ Fraser-Wilcox illusion, each including two subtypes. Then, ten basic illusions constitute this group. These illusions are strong in the peripheral vision as well as in bright stimuli or in bright illumination. The ¡®Rotating snakes¡¯ illusion is a product of this group. In fMRI studies, it was revealed that the ¡®Rotating snakes¡¯ illusion image activates hMT+ as well as lower visual areas such as V1 or V2 (Ashida, 2012; Kuriki et al., 2008). Yet the mechanism of this illusion remains indistinct.

       Moreover, Kitaoka (2012) proposed a novel variant, in which illusion is strong in dark stimuli. This variant is strong in bright illumination like the previous variants. Furthermore, another novel illusion which is strong in dark illuminationhas subsequently been revealed (Kitaoka, 2013). It is called the color-dependent Fraser-Wilcox illusion. This illusion shows a reversal in the direction of illusory motion depending on illumination. Here I will discuss this paradoxical illusion mentioning possible involvement of rod activity.

 

    References

    Ashida, H., Kuriki, I., Murakami, I., Hisakata, R. and Kitaoka, A. (2012). Direction-specific fMRI adaptation reveals the visual cortical network underlying the "Rotating Snakes" illusion. NeuroImage, 61, 1143¨C1152.

    Kitaoka, A. (2012). The Fraser-Wilcox illusion and its extension. Perception 41 ECVP Abstract Supplement, page 91.

    Kitaoka, A. and Ashida, H. (2003). Phenomenal characteristics of the peripheral drift illusion.VISION (Journal of the Vision Society of Japan), 15, 261-262.

    Kitaoka, A. and Ashida, H. (2007). A variant of the anomalous motion illusion based upon contrast and visual latency. Perception, 36, 1019-1035.

    Kitaoka, A. and Yanaka, H. (2013). Reversal of the color-dependent Fraser-Wilcox illusion under a dark condition. Perception 42 ECVP Abstract Supplement, page 97.

    Kitaoka, A., Pinna, B., and Brelstaff, G. (2001). New variations of spiral illusions.Perception, 30, 637-646.

    Kuriki, I., Ashida, H., Murakami, I., and Kitaoka, A. (2008). Functional brain imaging of the Rotating Snakes illusion by fMRI. Journal of Vision, 8(10):16, 1-10.

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      Bio:  Akiyoshi Kitaoka is a professor of psychology at the College of Letters, Ritsumeikan University, Kyoto, Japan. He received a BSc from the Department of Biology, University of Tsukuba, Tsukuba, Japan in 1984, and received a PhD degree from the Institute of Psychology, University of Tsukuba in 1991. He received the "Gold Prize" of the 9th L'OREAL Art and Science of Color Prize in 2006, and the "Award for Original Studies" from the Japanese Society of Cognitive Psychology in 2007. He extensively studies visual illusions including geometrical (shape) illusions, lightness illusions, color illusions, motion illusions and other visual phenomena including visual completion or perceptual transparency. He also produces a variety of "illusion works" and exhibits them in his webpages. The most popular illusion work is "Rotating snakes", which was created in 2003 as an image of the optimized Fraser-Wilcox illusion. Before he started to investigate visual illusions, he studied animal psychology (burrowing behavior in rats and mice) in the University of Tsukuba and electrophysiology (neuronal activity of the inferotemporal cortex in Macaque monkeys) in the Tokyo Metropolitan Institute for Neuroscience. He wrote more than ten books of visual illusions or illusion designs.

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