摘要
目的测定非小细胞肺癌病灶的同机FDGPETCT图像融合的精度,并利用PETCT融合图像制定精确放疗计划,探讨融合精度对放疗计划的影响。方法13例非小细胞肺癌患者分别采用几何中心法(COG)及体积法测定PETCT同机图像融合精度,COG法为测定病灶PET图像的COG与CT图像COG的距离,体积法为测定病灶PET与CT图像融合部分体积(VPETCT)占总体积(VPET+CT)的百分比(PPETCT),将勾画靶区文件传输至三维放疗计划系统,每例病例分别依据PET、CT、PET+CT3个靶区制定三套计划,分别比较三者正常组织受照剂量(肺、心脏、脊髓)的差异。结果采用COG法测定所有病灶的融合误差为(4.95±2.41)mm(1.00～8.68mm)。采用体积法测定PPETCT为46.7%±19.2%(2.7%～70.4%)。按照不同靶区制定的三组计划中,肺的受量(V20、肺平均受量)、脊髓最大剂量、心脏平均和最大受量的差异均有统计学意义(P<0.05),脊髓的平均受量差异无统计学意义(P=0.05)。下肺病灶PETCT图像融合精度较差,制定放疗计划中正常组织受量增加较上肺病灶明显。结论肺部病灶同机PETCT融合的偏差较小。融合精度对靶区的大小有一定的影响,融合误差将会使正常组织的受量增加。采用融合图像制定放疗计划时,必须对融合精度进行测定并采取有效的措施降低融合误差。
Objective To evaluate the accuracy of image coregistration of FDG PET-CT image and the its impact on radiation treatment planning in non-small cell lung cancer(NSCLC). Methods Thirteen patients with well-circumscribed NSCLC lesions were examined by in-line PET-CT . The registration accuracy of PET-CT image was measured with two methods-volume and center of geometry (COG). The volume of interest of each lesion was defined separately on PET, CT and fused images (V_ PET , V_ CT , V_ PET+CT ). The overlap volume of PET and CT image was calculated from formula: V_ PET-CT =V_ PET +V_ CT -V_ PET+CT . The percentage of V_ PET-CT on V_ PET+CT (P_ PET-CT ) was used to assess the fusion accuracy of PET and CT images. The geometric center of gravity (COG) of V_ PET and V_ CT was assessed. The COG distance between the PET image and the CT image (D_ COG ) was measured. The image data were transferred to the radiation treatment planning system. Three plans were made according to different volumes (V_ PET , V_ CT , V_ PET+CT ) with the same prescribed dose of 60?Gy. The dose in lung, heart and spinal cord were recorded in plans and compared with one another. Results The mean of D_ COG was (4.95± 2.41 )?mm(1.00- 8.68?mm ). P_ PET-CT was 46.7%±19.2%(2.7%-70.4%). Misregistration tended to be more pronounced in the lower lung (D_ COG = [4.73±2.50] ?mm, P_ PET-CT =52.0%±23.6%) than in upper lung (D_ COG = [5.21±2.51] ?mm, P_ PET-CT =40.5%±11.4%) (P>0.05). The dose to lung (mean lung dose and V_ 20 ),maximal dose to spinal cord ,mean and maximal dose to the heart were higher in plans with V_ PET+CT than in those with V_ PET and V_ CT (P<0.05), but statistical difference was not found among the mean spinal cord doses in the three plans (P= 0.05 ). Conclusions The registration of lung lesion in PET-CT image is usually accurate. Misregistration may exert on the target volume delineation in radiation treatment planning with PET-CT fused image for non-small cell lung cancer and result in higher dose to normal tissue. More precise measurement and control of the misregistration must be taken into account when fused PET-CT image were used in making radiotherapy planning.
出处
《中华放射肿瘤学杂志》
CSCD
北大核心
2005年第4期314-318,共5页
Chinese Journal of Radiation Oncology
