- 期刊
骨盆固定器對擺位誤差的影響
The Influence of the Pelvic Immobilization Device to Setup Error during Radiotherapy
摘要
目的：評估骨盆固定器對於放射治療擺位誤差的影響。 材料與方法：本研究選擇三種骨盆部位的惡性腫瘤作為分析比較的對象：包括了子宮頸癌10例，攝護腺癌4例，及直腸癌2例。在執行放射治療計畫之前即以隨機抽樣的方式區分為傳統未加骨盆固定器與使用骨盆固定器兩組患者。開始治療後每周拍攝兩張照野片，照野片拍攝的方向是前後或兩側面方向。本研究共取得34張模擬攝影片與149張照野片。放射治療方式在兩組之問沒有任何差異，除直腸癌是以三照野治療外其餘均是四照野方式治療。記錄放射治療擺位誤差的方法為比較模擬攝影X光片與照野片的左右、頭腳、前後、以及旋轉等軸的誤差。分析擺位誤差的方法是以t-test（兩尾）及chi-square方法分別評估誤差平均值及誤差超過5mm 比例等數值有無統計學上的差異。 結果：傳統未加骨盆固定器與使用骨盆固定器兩組之間的誤差型態並不相同。以誤差平均值方式評佔，兩者左右(p=0.445)、頭腳(p=0.092)、與旋轉軸(p=0.337)均未有明顯差別。唯有機頭270度時的前後軸達到統計差異(p=0.016)；使用骨盆固定器患者的平均誤差(0.21mm, SD=1.11mm)明顯小於未使用骨盆固定器患者的平均誤差(1.54mm, SD=2.58mrn)，以誤差超過5mm比例的方法作評估，使用骨盆固定器可減少前後軸的誤差(p=0.046)，但反而使頭腳軸的誤差加大(p=0.018)；左右軸則未有顯著差別(p=0.359)。 結論：使用骨盆固定器可以顯著的減少前後軸方向的誤差，但對擺位誤差超過5mm的比例而言它反而使頭腳軸方向的誤差加大；對於左右軸方向的誤差並未有明顯的影響。所以當使用骨盆固定器時應注意頭腳軸方向的固定方法以減少此方向軸的誤差。
並列摘要
Purpose: To evaluate the extent of influence of setup deviation by pelvic immobilization device. Materials and Methods: This prospective randomized study composed of two study groups that were with or without pelvic immobilization device. We included three kinds of malignant diseases that originated in pelvic cavity; these were 10 cases of cervical cancer, 4 cases of prostate cancer, and 2 cases of rectal cancer. Except from the two patients of rectal cancer, all of them were treated with four-field box technique and the principle of radiation technique was all the same in both groups. The portal films were taken from anterior-posterior and bilateral directions with the frequency of twice per week. There were 34 simulation films and 149 portal films to be evaluated. The setup error was recorded by comparison the iso-center shift between simulation and portal films of four individual axes, that were latero-lateral, caudo-cranial, anterior-posterior axis and degree of rotation. The statistic methods for evaluation the results were two-tall t-test and chi-square methods for mean value of setup deviation and ratio of iso-center shift exceeded 5-mm, respectively. Results: The patterns of setup error were different between non-immobilization and immobilization groups. When evaluated by mean setup error, there were no significant differencer between the two groups of the laterolateral (p=0.44S) and caudo-cranial (p=0.092) axes, the degree of rotation was also no difference at all (p=0.337). In anterior-posterior axis evaluated by gantry 270 degree, the mean setup error of the immobilization group (0.21-mm, SD=l.llmm) was significant smaller than non-immobilization group (1.54-mm, SD=2.SSmm) (p=0.016). Evaluation by the ratio of iso-center shift exceeded 5-mm, the immobilized group showed significant reduction in the error of anterior-posterior axis (p=0.046), but this group had opposed behavior of the caudocranial axis (p=0.0l8). The latero-lateral (p=0.359) and rotational (p=0.803) axes did not show any significant difference between the two groups. Conclusion: With the immobilization device, there has significant improvement of the anterior-posterior axis, but the caudo-cranial axis has opposed effect when we evaluated by the ratio of setup error exceeded 5-mm. The iso-center shift in latero-lateral axis has no significant difference despite of the used of this immobilization device. So, we must pay more effort to avoid the inter-treatment variation of the caudo-cranial axis when we use this kind of pelvic immobilization device.