Nolan Michael W, Randall Elissa K, LaRue Susan M, Lunn Katharine F, Stewart Jeff, Kraft Susan L
Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523.
Vet Radiol Ultrasound. 2013 Sep-Oct;54(5):560-6. doi: 10.1111/vru.12070. Epub 2013 Jun 6.
Consistency and accuracy in normal tissue contouring in radiotherapy planning is important for comparison of dosimetry and toxicity data between studies. The purpose of this study was to determine whether magnetic resonance imaging (MRI) improves the accuracy of optic apparatus contouring as compared with computed tomography (CT) in both normal and acromegalic cats, and to construct a reference contour of the feline optic apparatus. Both CT and MRI were performed on cadavers of four healthy cats, as well as on five radiotherapy patients with feline acromegaly. Contours of the optic apparatus were drawn for each imaging study. The volume, center of mass, and the degree of concordance and mismatch were determined for each, and compared with a reference standard. Precontrast CT was found to overestimate volume as compared with MRI in acromegalic cats; no other statistically significant differences were identified in the volume, concordance index or mismatch index values of normal or acromegalic cats. Contours derived from T2-wieghted MRI were subjectively considered to best match the reference standard. The caudal margin of the optic chiasm and the optic tracts were difficult to confidently contour regardless of which imaging modality and/or sequence was used. In conclusion, findings from the current study supported the use of a combination of CT and MR images and a priori knowledge of the shape of the optic apparatus to guide accurate contouring, especially where image contrast is not sufficient to clearly delineate the margins. Guidelines for feline optic apparatus contouring developed in this study can be used for future studies.
放射治疗计划中正常组织轮廓勾画的一致性和准确性对于比较不同研究之间的剂量学和毒性数据非常重要。本研究的目的是确定在正常猫和肢端肥大症猫中，与计算机断层扫描（CT）相比，磁共振成像（MRI）是否能提高视器轮廓勾画的准确性，并构建猫视器的参考轮廓。对四只健康猫的尸体以及五名患有猫肢端肥大症的放疗患者进行了CT和MRI检查。对每项成像研究绘制视器轮廓。确定每个轮廓的体积、质心以及一致性和不匹配程度，并与参考标准进行比较。发现在肢端肥大症猫中，与MRI相比，平扫CT高估了体积；在正常或肢端肥大症猫的体积、一致性指数或不匹配指数值方面，未发现其他统计学上的显著差异。主观认为，从T2加权MRI得出的轮廓与参考标准最匹配。无论使用哪种成像方式和/或序列，视交叉和视束的尾缘都难以可靠地勾画。总之，本研究结果支持结合使用CT和MR图像以及对视器形状的先验知识来指导准确的轮廓勾画，特别是在图像对比度不足以清晰描绘边缘的情况下。本研究制定的猫视器轮廓勾画指南可用于未来的研究。
