应用CBCT研究胸腹部肿瘤IMRT两种体位固定技术的摆位误差

Study the setup errors by CBCT in radiotherapy with two different immobilization techniques for thoracic and abdominal tumors

目的应用千伏级CBCT研究IMRT两种体位固定方式的摆位误差。方法选取60例胸腹部肿瘤IMRT患者均分两组，研究组采用体部固定底板＋真空垫＋热塑成型网罩体位固定方式，对照组采用体部固定底板＋热塑成型网罩体位固定方式。放疗前行CBCT扫描并在线匹配，得出左右、上下、前后方向摆位误差，并用2．5∑＋0．78算出胛V外放界值。对两组摆位误差比较行成组t检验。结果研究组患者左右、上下、前后方向的摆位误差分别为（0．32±2．58）、（-0．40±3．89）、（-0．75±2．43）mm，PTV外放界值分别为5．60、6．08、6．32mm；对照组的分别为（0．62±3．60）、（2．44±4．93）、（0．66±2．85）mm和8．07、10．63、6．90mm；两组在上述方向的比较t=-0．78、-5．11、-4．22，P=0．440、0．000、0．000。结论采用体部固定底板＋真空垫＋热塑成型网罩体位固定方式能有效固定患者，在控制误差方面明显优于体部固定底板＋热塑成型网罩体位固定方式。

Objective To study the set-up errors by CBCT in IMRT with two different immobilization techniques for thoracic and abdominal tumors. Methods Sixty patients with thoracic and abdominal tumor were included in this study and separated into study group and the control group. The study group were immobilized with carbon fiber holder, vacuum bag and thermoplastic mask. The control group were immobilized with carbon fiber holder and thermoplastic mask. CBCT scan and auto-match online were regularly performed before the treatment. The setup of left-fight（x）, superior-inferior（y）, anterior-posterior （z） were received. The value of the Mptv was calculated, meanwhile. The grouped t-test of was carried out between these two methods. Results The shift errors in x-, y-, z-dimension of the study group were （0. 32 ±2. 58）mm, （ -0.40 ±3.89） mm, （ -0. 75±2. 43） ram. The MpTv were 5.60 mm,6. 08 mm,6. 32 mm. The translation set-up errors in x - , y - , z - dimension of the control group were（0. 62 ±3.60）, （2.44 ±4. 93）, （0. 66 ±2. 85） mm, respectively. The Merv were 8.07,10. 63,6.90 mm, respectively. The t-test value were t = - 0. 78, - 5.11, - 4. 22, P = 0. 440, 0. 000, 0. 000, respectively. Conclusions The immobilization techniques with carbon fiber holder, vacuum bag and thermoplastic mask would be better than the techniques without the vacuum bag in reducing the setup errors.