{
    "abstract": "Magnetic resonance imaging (MRI) is increasingly used in treatment preparation of ocular proton therapy, but its spatial accuracy might be limited by geometric distortions due to susceptibility artefacts. A correct geometry of the MR images is paramount since it defines where the dose will be delivered. In this study, we assessed the geometrical accuracy of ocular MRI.\nA dedicated ocular 3\u00a0T MRI protocol, with localized shimming and increased gradients, was compared to computed tomography (CT) and X-ray images in a phantom and in 15 uveal melanoma patients. The MRI protocol contained three-dimensional T2-weighted and T1-weighted sequences with an isotropic reconstruction resolution of 0.3-0.4\u00a0mm. Tantalum clips were identified by three observers and clip-clip distances were compared between T2-weighted and T1-weighted MRI, CT and X-ray images for the phantom and between MRI and X-ray images for the patients.\nInterobserver variability was below 0.35\u00a0mm for the phantom and 0.30(T1)/0.61(T2) mm in patients. Mean absolute differences between MRI and reference were below 0.27\u00a0\u00b1\u00a00.16\u00a0mm and 0.32\u00a0\u00b1\u00a00.23\u00a0mm for the phantom and in patients, respectively. In patients, clip-clip distances were slightly larger on MRI than on X-ray images (mean difference T1: 0.11\u00a0\u00b1\u00a00.38\u00a0mm, T2: 0.10\u00a0\u00b1\u00a00.44\u00a0mm). Differences did not increase at larger distances and did not correlate to interobserver variability.\nA dedicated ocular MRI protocol can produce images of the eye with a geometrical accuracy below half the MRI acquisition voxel (<0.4\u00a0mm). Therefore, these images can be used for ocular proton therapy planning, both in the current model-based workflow and in proposed three-dimensional MR-based workflows.",
    "authors": [
        {
            "affiliation": "Leiden University Medical Center, Department of Ophthalmology, Leiden, the Netherlands.\nLeiden University Medical Center, Department of Radiology, Leiden, the Netherlands.\nLeiden University Medical Center, Department of Radiation Oncology, Leiden, the Netherlands.",
            "firstname": "Lisa",
            "initials": "L",
            "lastname": "Klaassen"
        },
        {
            "affiliation": "Leiden University Medical Center, Department of Ophthalmology, Leiden, the Netherlands.\nLeiden University Medical Center, Department of Radiology, Leiden, the Netherlands.\nLeiden University Medical Center, Department of Radiation Oncology, Leiden, the Netherlands.",
            "firstname": "Corn\u00e9",
            "initials": "C",
            "lastname": "Haasjes"
        },
        {
            "affiliation": "Leiden University Medical Center, Department of Radiation Oncology, Leiden, the Netherlands.\nHollandPTC, Delft, the Netherlands.",
            "firstname": "Martijn",
            "initials": "M",
            "lastname": "Hol"
        },
        {
            "affiliation": "HollandPTC, Delft, the Netherlands.",
            "firstname": "Patricia",
            "initials": "P",
            "lastname": "Cambraia Lopes"
        },
        {
            "affiliation": "HollandPTC, Delft, the Netherlands.",
            "firstname": "Kees",
            "initials": "K",
            "lastname": "Spruijt"
        },
        {
            "affiliation": "Leiden University Medical Center, Department of Radiology, Leiden, the Netherlands.\nHollandPTC, Delft, the Netherlands.",
            "firstname": "Christal",
            "initials": "C",
            "lastname": "van de Steeg-Henzen"
        },
        {
            "affiliation": "Leiden University Medical Center, Department of Ophthalmology, Leiden, the Netherlands.",
            "firstname": "Khanh",
            "initials": "K",
            "lastname": "Vu"
        },
        {
            "affiliation": "Leiden University Medical Center, Department of Radiation Oncology, Leiden, the Netherlands.\nHollandPTC, Delft, the Netherlands.",
            "firstname": "Pauline",
            "initials": "P",
            "lastname": "Bakker"
        },
        {
            "affiliation": "Leiden University Medical Center, Department of Radiation Oncology, Leiden, the Netherlands.\nHollandPTC, Delft, the Netherlands.",
            "firstname": "Coen",
            "initials": "C",
            "lastname": "Rasch"
        },
        {
            "affiliation": "Leiden University Medical Center, Department of Radiology, Leiden, the Netherlands.\nHollandPTC, Delft, the Netherlands.",
            "firstname": "Berit",
            "initials": "B",
            "lastname": "Verbist"
        },
        {
            "affiliation": "Leiden University Medical Center, Department of Ophthalmology, Leiden, the Netherlands.\nLeiden University Medical Center, Department of Radiology, Leiden, the Netherlands.\nLeiden University Medical Center, Department of Radiation Oncology, Leiden, the Netherlands.",
            "firstname": "Jan-Willem",
            "initials": "JW",
            "lastname": "Beenakker"
        }
    ],
    "conclusions": null,
    "copyrights": "\u00a9 2024 The Authors.",
    "doi": "10.1016/j.phro.2024.100598\n10.1016/j.ijrobp.2006.01.020\n10.3390/cancers13246241\n10.21037/cco.2016.07.06\n10.1016/j.ijrobp.2016.01.040\n10.3390/cancers15112995\n10.1080/02713683.2021.1874021\n10.1007/s00234-021-02825-5\n10.1186/s13244-021-01000-x\n10.1016/j.phro.2022.11.001\n10.1002/nbm.3041\n10.1016/j.oret.2022.06.019\n10.1002/mp.14665\n10.1016/j.radonc.2022.06.021\n10.1002/mp.16006\n10.1002/mp.15573\n10.1016/j.ijrobp.2016.02.059\n10.1016/j.acra.2005.10.023\n10.1002/mrm.1206\n10.1016/j.phro.2021.01.003\n10.1007/s10334-016-0529-4\n10.1016/j.radonc.2020.08.023\n10.1002/mrm.26534\n10.1186/s12886-022-02289-y\n10.3390/cancers11030377\n10.1007/s10334-014-0446-3\n10.1002/mp.12516\n10.1088/1361-6560/abb0f9\n10.1016/j.ijrobp.2011.01.046\n10.1016/j.ijrobp.2014.08.349\n10.1088/0031-9155/55/22/002\n10.1007/s10334-019-00788-6\n10.1177/1533034617735454\n10.1136/bjo.74.3.183\n10.1016/j.ejmp.2024.103358\n10.1016/j.adro.2022.101149\n10.3390/cancers14194729\n10.3174/ajnr.A6096\n10.1007/s00247-011-2201-5",
    "journal": "Physics and imaging in radiation oncology",
    "keywords": [
        "MRI",
        "Proton therapy",
        "Treatment planning",
        "Uveal melanoma"
    ],
    "methods": null,
    "publication_date": "2024-07-12",
    "pubmed_id": "38993288\n16647221\n34944862\n27558251\n27084651\n37296958\n33535828\n34718831\n34080069\n36386446\n24123279\n35840053\n33336379\n35788353\n36195575\n35218037\n27354136\n16488850\n11477648\n33898780\n26915081\n32890606\n27851881\n35123441\n34901465\n30884881\n24802620\n28803447\n33179610\n21477942\n25442348\n20962365\n31646408\n29332453\n2182105\n38643558\n36691449\n36230660\n31221635\n21850471",
    "results": "Interobserver variability was below 0.35\u00a0mm for the phantom and 0.30(T1)/0.61(T2) mm in patients. Mean absolute differences between MRI and reference were below 0.27\u00a0\u00b1\u00a00.16\u00a0mm and 0.32\u00a0\u00b1\u00a00.23\u00a0mm for the phantom and in patients, respectively. In patients, clip-clip distances were slightly larger on MRI than on X-ray images (mean difference T1: 0.11\u00a0\u00b1\u00a00.38\u00a0mm, T2: 0.10\u00a0\u00b1\u00a00.44\u00a0mm). Differences did not increase at larger distances and did not correlate to interobserver variability.",
    "title": "Geometrical accuracy of magnetic resonance imaging for ocular proton therapy planning.",
    "xml": "<Element 'PubmedArticle' at 0x788501c14810>"
}