{
  "abstract": "Large-scale acoustic simulations underpin the development of ultrasound imaging and therapy, but modeling nonlinearity, frequency-dependent attenuation, and absorbing boundaries in heterogeneous tissue remains computationally demanding. We present Fullwave 2, a unified time-domain formulation with arbitrary power-law tissue attenuation and perfectly matched layers (PMLs) within a single framework suited to high-order finite difference solution. Attenuation and dispersion are encoded directly into complex coordinate-stretched spatial derivatives through multiple relaxation mechanisms. Because the same mechanism describes both interior tissue attenuation and the absorbing boundary, the convolutional PML (C-PML) becomes a special case of the domain-wide model and adds no extra computational burden. The formulation preserves the structure of the d'Alembertian operator, which allows high-order staggered-grid finite difference stencils optimized for long-distance propagation, and a two-stage C-PML with a transition region is introduced to ensure numerical stability in the presence of multiple relaxations. The domain-wide multiple relaxation model reproduces power-law attenuation with less than 5% attenuation error and 0.5% phase-velocity error over 1-20 MHz. The two-stage C-PML reaches reflection coefficients below -49 dB with a compact 4 lambda footprint. Nonlinear propagation is validated against a 1D Burgers solution, with agreement up to the 7^(th) harmonic. The framework is demonstrated on 2D abdominal wall imaging and 3D transcranial rat skull simulations, where it accurately captures complex scattering and aberration artifacts. Fullwave 2 unifies nonlinear propagation, arbitrary power-law attenuation, and absorbing boundaries in a single, computationally efficient time-domain formulation, providing an accurate and scalable wave propagation tool for medical ultrasound research.",
  "abstract_shown": true,
  "affiliations": [
    "North Carolina State University",
    "The University of North Carolina at Chapel Hill"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Masashi Sode",
      "orcid": "0000-0002-3685-7378"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Gianmarco Pinton",
      "orcid": "0000-0002-4896-1439"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/40re7b3qwc41v.bib",
  "cited_by": 18,
  "doi": "10.1088/1361-6560/ae9116",
  "fulltext_url": null,
  "id": "40re7b3qwc41v",
  "issns": [
    "0031-9155",
    "1361-6560"
  ],
  "landing_url": "https://doi.org/10.1088/1361-6560/ae9116",
  "language": "en",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2741|Ultrasound Imaging and Elastography"
    ]
  ],
  "openalex": "W7171427901",
  "pdf_url": null,
  "pmcid": "PMC13579090",
  "pmid": "42508458",
  "published": "2026-07-27",
  "publisher": "IOP Publishing",
  "ris": "https://research.draconitic.com/paper/40re7b3qwc41v.ris",
  "sources": [
    {
      "first_seen": "2026-11-04T13:21:15Z",
      "native_id": "W7171427901",
      "source": "openalex",
      "url": "https://doi.org/10.1088/1361-6560/ae9116"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "openalex:2741|Ultrasound Imaging and Elastography",
      "subfield": "imaging"
    }
  ],
  "title": "A fullwave model of the nonlinear wave equation with multiple relaxations and relaxing perfectly matched layers for high-order numerical finite difference solutions",
  "title_text": "A fullwave model of the nonlinear wave equation with multiple relaxations and relaxing perfectly matched layers for high-order numerical finite difference solutions",
  "type": "peer-reviewed",
  "updated_at": "2026-11-09T13:21:15Z",
  "url": "https://research.draconitic.com/paper/40re7b3qwc41v",
  "venue": "Physics in Medicine and Biology",
  "versions": []
}