Hirohito Kan1, Nobuyuki Arai2, Masahiro Takizawa3, Kazuyoshi Omori4, Harumasa Kasai5, Hiroshi Kunitomo6, Yasujiro Hirose7, Yuta Shibamoto8. 1. Department of Radiology, Nagoya City University Hospital, 1-Kawasumi, Mizuho-cho Mizuho-ku, Nagoya City, Aichi, 4678602, Japan. Electronic address: h.kan1208@gmail.com. 2. Department of Radiology, Nagoya City University Hospital, 1-Kawasumi, Mizuho-cho Mizuho-ku, Nagoya City, Aichi, 4678602, Japan. Electronic address: rarai51@med.nagoya-cu.ac.jp. 3. Healthcare Business Unit, Hitachi Ltd, Japan. Electronic address: masahiro.takizawa.jd@hitachi.com. 4. Healthcare Business Unit, Hitachi Ltd, Japan. Electronic address: kazuyoshi.omori.xu@hitachi.com. 5. Department of Radiology, Nagoya City University Hospital, 1-Kawasumi, Mizuho-cho Mizuho-ku, Nagoya City, Aichi, 4678602, Japan. 6. Department of Radiology, Nagoya City University Hospital, 1-Kawasumi, Mizuho-cho Mizuho-ku, Nagoya City, Aichi, 4678602, Japan. Electronic address: rakunny@med.nagoya-cu.ac.jp. 7. Department of Radiology, Nagoya City University Hospital, 1-Kawasumi, Mizuho-cho Mizuho-ku, Nagoya City, Aichi, 4678602, Japan. Electronic address: rahirose@med.nagoya-cu.ac.jp. 8. Department of Radiology, Nagoya City University Hospital, 1-Kawasumi, Mizuho-cho Mizuho-ku, Nagoya City, Aichi, 4678602, Japan. Electronic address: yshiba@med.nagoya-cu.ac.jp.
Abstract
PURPOSE: We developed a non-regularized, variable kernel, sophisticated harmonic artifact reduction for phase data (NR-VSHARP) method to accurately estimate local tissue fields without regularization for quantitative susceptibility mapping (QSM). We then used a digital brain phantom to evaluate the accuracy of the NR-VSHARP method, and compared it with the VSHARP and iterative spherical mean value (iSMV) methods through in vivo human brain experiments. MATERIALS AND METHODS: Our proposed NR-VSHARP method, which uses variable spherical mean value (SMV) kernels, minimizes L2 norms only within the volume of interest to reduce phase errors and save cortical information without regularization. In a numerical phantom study, relative local field and susceptibility map errors were determined using NR-VSHARP, VSHARP, and iSMV. Additionally, various background field elimination methods were used to image the human brain. RESULTS: In a numerical phantom study, the use of NR-VSHARP considerably reduced the relative local field and susceptibility map errors throughout a digital whole brain phantom, compared with VSHARP and iSMV. In the in vivo experiment, the NR-VSHARP-estimated local field could sufficiently achieve minimal boundary losses and phase error suppression throughout the brain. Moreover, the susceptibility map generated using NR-VSHARP minimized the occurrence of streaking artifacts caused by insufficient background field removal. CONCLUSION: Our proposed NR-VSHARP method yields minimal boundary losses and highly precise phase data. Our results suggest that this technique may facilitate high-quality QSM.
PURPOSE: We developed a non-regularized, variable kernel, sophisticated harmonic artifact reduction for phase data (NR-VSHARP) method to accurately estimate local tissue fields without regularization for quantitative susceptibility mapping (QSM). We then used a digital brain phantom to evaluate the accuracy of the NR-VSHARP method, and compared it with the VSHARP and iterative spherical mean value (iSMV) methods through in vivo human brain experiments. MATERIALS AND METHODS: Our proposed NR-VSHARP method, which uses variable spherical mean value (SMV) kernels, minimizes L2 norms only within the volume of interest to reduce phase errors and save cortical information without regularization. In a numerical phantom study, relative local field and susceptibility map errors were determined using NR-VSHARP, VSHARP, and iSMV. Additionally, various background field elimination methods were used to image the human brain. RESULTS: In a numerical phantom study, the use of NR-VSHARP considerably reduced the relative local field and susceptibility map errors throughout a digital whole brain phantom, compared with VSHARP and iSMV. In the in vivo experiment, the NR-VSHARP-estimated local field could sufficiently achieve minimal boundary losses and phase error suppression throughout the brain. Moreover, the susceptibility map generated using NR-VSHARP minimized the occurrence of streaking artifacts caused by insufficient background field removal. CONCLUSION: Our proposed NR-VSHARP method yields minimal boundary losses and highly precise phase data. Our results suggest that this technique may facilitate high-quality QSM.