Sudha S P, Gopalakrishnan M S, Saravanan K
Department of Radiotherapy, Jawaharlal Institute of Post-Graduate Medical Education and Research (JIPMER), Pondicherry, India.
Department of Neurosurgery, Jawaharlal Institute of Post-Graduate Medical Education and Research (JIPMER), Pondicherry, India.
J Appl Clin Med Phys. 2017 Sep;18(5):174-177. doi: 10.1002/acm2.12144. Epub 2017 Aug 18.
The spinal cord is poorly visualized on CT images but is well visualized in MRI images. However, implants used for spinal stabilization can produce artifacts on the MRI images which can interfere with identification of the cord. CT myelography in conjunction with CT simulation helps to clearly delineate the cord.
CT simulation was done in a patient with vertebral hemangioma. Pre- and post myelography images were obtained. Two plans were generated on pre and post myelography CT images using Eclipse™ treatment planning system (TPS) version 10.0, Varian Medical Systems, USA. The prescribed total dose to PTV was 40 Gy in 20 fractions.
The cord was poorly visualized in the premyelogram CT images. The titanium implants used for spinal cord stabilization produced artifacts in the MRI images. Figure Post myelogram, the contrast lit up the spinal cord. There was an overlap of 0.75 cc volume of the spinal cord with the PTV in the premyelogram images. This volume was reduced to 0 cc in the post myelogram images. There was an overlap of 5.4 cc volume of the PRV of spinal cord with the PTV in the premyelogram images which was reduced to 1 cc in the post myelogram images. The overlap region between the PTV and spinal cord received around 71% of the prescribed dose in premyelogram CT could be reduced to 0% in the post myelogram CT. The mean dose received by the overlap PRV spinal cord and PTV could be increased from 70% in the premyelogram to 92% in the post myelogram plans.
CT myelogram in conjunction with CT simulation is particularly useful in cases where the tumor margin is very close to the cord and spinal implants are causing distortion of magnetic resonance images.
脊髓在CT图像上显示不佳，但在MRI图像上显示良好。然而，用于脊柱稳定的植入物会在MRI图像上产生伪影，这可能会干扰脊髓的识别。CT脊髓造影结合CT模拟有助于清晰地勾勒出脊髓。
对一名患有椎体血管瘤的患者进行CT模拟。获取脊髓造影前后的图像。使用美国瓦里安医疗系统公司的Eclipse™治疗计划系统（TPS）版本10.0，在脊髓造影前后的CT图像上生成两个计划。PTV的处方总剂量为40 Gy，分20次给予。
脊髓造影前的CT图像中脊髓显示不佳。用于脊髓稳定的钛植入物在MRI图像上产生伪影。图 脊髓造影后，造影剂使脊髓显影。脊髓造影前图像中脊髓有0.75 cc的体积与PTV重叠。在脊髓造影后图像中，该体积减少至0 cc。脊髓造影前图像中脊髓PRV有5.4 cc的体积与PTV重叠，在脊髓造影后图像中减少至1 cc。PTV与脊髓之间的重叠区域在脊髓造影前CT中接受约71%的处方剂量，在脊髓造影后CT中可降至0%。重叠的PRV脊髓和PTV接受的平均剂量可从脊髓造影前的70%增加到脊髓造影后计划中的92%。
CT脊髓造影结合CT模拟在肿瘤边缘非常靠近脊髓且脊柱植入物导致磁共振图像失真的情况下特别有用。
