Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning.
Feasibility and limitations of bulk density assignment in MRI for head and neck IMRT treatment planning.
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DOI：
10.1120/jacmp.v15i5.4851
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发表时间：
2014-09-08
影响因子：
2.1
通讯作者：
Teo BK
中科院分区：
文献类型：
--
作者：
Chin AL;Lin A;Anamalayil S;Teo BK
以颅底为中心的头颈部肿瘤MRI比CT更清晰。本研究的目的是探讨头颈部调强放疗（IMRT）治疗方案优化中体积密度分配的准确性。我们的研究调查了密度分配MRI和CT之间剂量计算的差异，并确定了在仅基于MRI的治疗计划框架中与牙种植体和MRI几何畸变相关的潜在局限性。对7名患者进行体积密度分配，并将其应用于MRI，生成三组MRI图像，其异质性水平不断提高：1)：所有患者均为水当量；2)：含骨，密度为；3)：包括骨头和空气。使用相同的计划和优化参数，生成基于MRI的IMRT计划，并根据目标覆盖率、等剂量分布和剂量-体积直方图（DVHs）与相应的、预先计算的基于CT的IMRT计划进行比较。幻影研究用于评估MRI几何畸变的大小和空间依赖性。基于剂量的计算将目标覆盖率高估了16.1%。在基于CT的计划中，骨分割将差异减少到覆盖区域的2%以内。进一步的空气分割改善了空气-组织界面附近的一致性。牙齿伪影导致了大量的目标覆盖率高估。在扫描仪等心周围的成像体积中，几何畸变小于1毫米，但在等心外侧17厘米处，几何畸变高达4毫米。在MRI - IMRT头颈部治疗计划框架下的体积密度分配是一种可行的方法，但存在一定的局限性。骨和牙齿占密度不均一效应的大部分。与CT相比，MRI可以很好地显示软组织，而牙科植入物在MRI上可能不可见，必须通过其他方法识别并指定适当的密度以准确计算剂量。肩部附近身体轮廓的远离中心几何畸变是剂量计算不准确的潜在来源。PACS数字：87.61。87.55高c。D
Head and neck cancers centered at the base of skull are better visualized on MRI than on CT. The purpose of this investigation was to investigate the accuracy of bulk density assignment in head and neck intensity‐modulated radiation therapy (IMRT) treatment plan optimization. Our study investigates dose calculation differences between density‐assigned MRI and CT, and identifies potential limitations related to dental implants and MRI geometrical distortion in the framework of MRI‐only‐based treatment planning. Bulk density assignment was performed and applied onto MRI to generate three MRI image sets with increasing levels of heterogeneity for seven patients: 1) : all water‐equivalent; 2) : included bone with density of ; and 3) : included bone and air. Using identical planning and optimization parameters, MRI‐based IMRT plans were generated and compared to corresponding, forward‐calculated, CT‐based plans on the basis of target coverage, isodose distributions, and dose‐volume histograms (DVHs). Phantom studies were performed to assess the magnitude and spatial dependence of MRI geometrical distortion. ‐based dose calculations overestimated target coverage by 16.1%. Segmentation of bone reduced differences to within 2% of the coverage area on the CT‐based plan. Further segmentation of air improved conformity near air–tissue interfaces. Dental artifacts caused substantial target coverage overestimation even on . Geometrical distortion was less than 1 mm in an imaging volume around scanner isocenter, but up to 4 mm at 17 cm lateral to isocenter. Bulk density assignment in the framework of MRI‐only IMRT head and neck treatment planning is a feasible method with certain limitations. Bone and teeth account for the majority of density heterogeneity effects. While soft tissue is well visualized on MRI compared to CT, dental implants may not be visible on MRI and must be identified by other means and assigned appropriate density for accurate dose calculation. Far off‐center geometrical distortion of the body contour near the shoulder region is a potential source of dose calculation inaccuracy. PACS numbers: 87.61.‐c, 87.55.‐D
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影响因子：
4.2
作者：
Idiyatullin, Djaudat;Corum, Curt;Nixdorf, Donald R.
通讯作者：
Nixdorf, Donald R.
DOI：
10.1186/1748-717x-5-62
发表时间：
2010-06-30
期刊：
Radiation oncology (London, England)
影响因子：
--
作者：
Jonsson JH;Karlsson MG;Karlsson M;Nyholm T
通讯作者：
Nyholm T
DOI：
10.1016/j.ijrobp.2004.05.068
发表时间：
2004-10-01
影响因子：
7
作者：
Chen, LL;Price, RA;Pollack, A
通讯作者：
Pollack, A
影响因子：
3.8
作者：
Fallone, B. G.;Murray, B.;Tymofichuk, D.
通讯作者：
Tymofichuk, D.
影响因子：
3.8
作者：
Johansson, Adam;Karlsson, Mikael;Nyholm, Tufve
通讯作者：
Nyholm, Tufve