RESUMO
Objective To explore the CTV to PTV external expansion boundary and the effect of the dose of normal lung tissue under different fixed modes by a comparative analysis of combined body position and thermoplastic film fixed set-up error of radiation therapy for lung cancer. Methods From October 2016 to March 2018, the patients who received chest radiology at the Tangshan people's hospital were enrolled as subjects retrospectively divided into two groups, including 50 patients with lung cancer radiotherapy with combined body position fixation, and 40 patients with lung cancer with thermoplastic film fixation. The two groups of patients drew the target areas in accordance with the unified standard, and the set-up error of left and right, up and down, front and rear ( x, y, z axis) were recorded respectively after 1 time/week cone CT( CBCT) matched with the planned CT image and analyzed by t test. According to the MPTV =2. 5Σ+0. 7δ, CTV to PTV external expansion boundary in the combined body position group were calculated. And the V5、V20 and V30 of two groups of patients were calculated and analyzed by TPS system. Results The set-up error of the combined body position group and thermoplastic film group were respectively (1. 00 ± 0. 58) mm and (3. 28 ± 0. 43) mm on the x axis, (1. 42 ± 0. 28) mm on the y axis and (4. 03 ± 0. 41) mm, (1. 06 ± 0. 44) mm and (3. 18 ± 0. 34) mm on the z axis. The set-up errors of the two groups were statistically significant on x, y and z axis( t= -20. 740, -35. 596, -25. 015,P<0. 05). There was no significant difference in set-up errors between the central and peripheral lung cancer patients and between left and right lung cancer patients(P>0. 05). Through the MPTV =2. 5Σ+0. 7δ, CTV to PTV external expansion boundary in the combined body position fixation group was 2. 906 , 3. 746 and 2. 958 mm on x, y and z axis respectively. The comparison between group A and B showed that the mean values of V5 , V20 and V30 in group B were reduced by 1. 5％, 3. 1％ and 4. 8％ respectively compared with group A. Conclusions The combined body position technique can improve the accuracy of lung cancer patients after radiation therapy,and further reduce the boundary of CTV to PTV, which is of certain value to reduce the occurrence of radiation pneumonitis.
RESUMO
Objective To investigate the value of PET-CT in TNM staging and three-conformal radiotherapy (3DCRT) in esophageal carcinoma. Methods From September 2007 to November 2008, 20 patients with pathologically confirmed esophageal carcinoma were enrolled, including 2 treated with surgery and 18 with 3DCRT. All the patients received PET-CT simulation before the treatment. The length and maximum transverse diameter of Grit based on esophagoscope, esophagography, CT, PET-CT_(SUV2.5) and PET-CT_(40%SUVmax) were compared. The TNM stages were compared based on CT and PET-CT images. Three treatment plans were produced and analyzed based on images of CT, PET-CT_(SUV2.5) and PET-CT_(40%SUVmax),respectively. Results The length of lesion on esophagoscope, esophagography, CT, PET-CT_(SUV2.5) and PET-CT_(40%SUVmax) was 4. 93 cm, 5.06 cm, 6. 67 cm, 5. 89 cm and 4. 84 cm, respectively. The corresponding maximum transverse diameter on the last 3 images was 4. 05 cm, 3.38 cm and 2. 95 cm, respectively. In all, 31, 21 and 14 positive lymph nodes were identified according to CT images, PET-CT images and the both. Five patients with CT diagnosed stage M_0 were found to have distant metastasis by PET-CT images, and 1 patient with CT diagnosed stage M_1 was excluded by PET-CT. The volumes of GTV_(CT) were similar with GTV_(SUV2.5) in 2 patients, smaller in 5 patients, and larger for the remaining 13 patients. For these 13 patients, the radiation dose of normal tissues based on GTV_(SUV2.5) was relatively lower. Conclusions The length of lesion based on PET -CT_(SUV2.5) matches the pathological length best , followed by esophagography. With PET-CT_(40%SUVmax) the actual lesion length may be underestimated. TNM stage might be changed by PET-CT, and then the target volumes and radiation doses of normal tissues might be reduced.