【摘要】 目的 分析重力因素對二維探測器陣列驗證靜態調強計劃的影響，判斷機架角度歸為0°的測量方法是否安全可靠。 方法 在0°機架角和實際治療機架角分別測量靜態調強計劃的劑量分布，以3 mm范圍內偏差lt;3%(3% 3 mm)標準進行γ分析，獲得相對于參考劑量分布的通過率，分析通過率變化規律。分析兩種方法測量的等中心點絕對劑量的差異。 結果 通過率的變化呈隨機分布，96.9%的照射野偏差lt;2.5%。所有計劃的85.7%絕對劑量偏差lt;2%，最大偏差為4.75%。 結論 使用二維探測器陣列在0°角進行調強計劃的日常驗證是安全可靠的。【Abstract】 Objective To analyze impacts of gravity on the verification of IMRT plans with 2-Dimensional detector arrays and to evaluate the reliability of the measurements in vertical direction (gantry angle=0). Methods The dose distributions for each beam in IMRT plans were measured with 0 degree gantry angle and actual gantry angle respectively. The γ percentage pass rate (according to 3% 3 mm) for each beam under each angle condition was obtained by the comparison between the measured dose distribution and the calculated dose map from the treatment planning system which was treated as the reference distribution. Then the absolute dose at the isocenter for each plan was measured at each angle condition and was analyzed. Results The variations of γ percentage pass rates between the two types of measurements were randomly distributed, and the deviations for 96.9% beams were less than±2.5%. The differences between absolute doses for 85.7% beams were less than±2% and the biggest deviation was -4.75%. Conclusion Verification of IMRT plans for the radiotherapy quality assurance using 2-Dimensional detector arrays in 0 degree gantry angle is safe and reliable.
【摘要】 目的 調強放射治療（IMRT）能較好的保護危及器官并給予腫瘤足夠的致死劑量，基于多葉準直器（MLC）分步照射的IMRT技術對復雜病例需要更多子野。研究對直腸癌術后放射治療使用不同子野數目的IMRT計劃進行比對，選擇合理的子野數。 方法 選取2010年4-8月入院的直腸癌術后患者10例，保持射野入射角度及優化目標參數相同，僅改變MLC子野數目，設計不同IMRT對每一患者治療計劃的靶區適形指數（CI）、均勻性指數、最大劑量、最小劑量、平均劑量，危及器官關注體積的受照劑量，機器跳數及治療時間進行分析。 結果 所有治療計劃中靶區及危及器官的劑量學評估指標無統計學意義（Pgt;0.05），只有亞臨床計劃靶區（PTV）CI在15個子野的方案中（0.74±0.06）明顯差于25個子野方案（0.82±0.03）、40個子野方案（0.81±0.06）及60個子野方案（0.84±0.03），有統計學意義（Plt;0.05）；治療機器跳數（MU）隨子野數目增多明顯增大，15、20、40及60個子野方案所需MU分別為（458±56）、（559±62）、（614±74）、（622±82），有統計學意義（Plt;0.05），但40個子野方案與60個子野方案間無統計學意義。治療時間明顯隨子野數增加而增大。 結論 直腸癌術后IMRT計劃使用25個子野能滿足臨床劑量要求，同時能有效降低治療時間，可作為臨床應用參考值。【Abstract】 Objective The intensity modulated radiotherapy (IMRT) can deliver tumor enough doses and protect risk organs as much as possible at the same time. The MLC-based step and shoot IMRT(sIMRT) plan needs much more segment member to meet clinical aims. In this study, several sIMRT plans using different segment number for postoperative rectal cancer were compared to find out the most reasonable segment number setting. Methods Ten patients with rectal carcinoma underwent postoperative adjuvant radiotherapy for rectal cancer from April to August 2010 were selected. For each patient, the angle of field, the prescription expected and the physical parameters optimized were kept the same, while only the number of segments was changed in sIMRT plans. The dose volume histogram-based parameters [conformity index (CI) and homogeneous index (HI)] and other parameters concerned were compared and analyzed. Results The indexes of dosimetry associated with the targets and risk organs showed no significant statistical difference among the 4 sIMRT plans with different segment numbers. The index CI of PTV in the sIMRT plan with 15 segments (CI 0.74±0.06) was less than that in the sIMRT plan with 25 segments (CI 0.82±0.03), the sIMRT plan with 40 segments plan (CI 0.81±0.06), and the sIMRT plan with 60 segments (CI 0.84±0.03) (Plt;0.05). There were significant differences in MU among the sIMRT plans with 15 segments (average MU: 458±56) , with 25 segments (average MU: 559±62 ), and with 40 segments (average MU: 614±74)or with the 60 segments (average MU: 622±82 (Plt;0.05). The more segments meant more MU and more irradiation time. Conclusion The sIMRT plan for patients of rectal cancer to receive postoperative adjuvant radiotherapy may require at least 25 segments to balance the accepted dose results and efficient delivering.
【摘要】 目的 評價大分割適形放射治療對腹膜后軟組織腫瘤術后患者的治療作用。 方法 對1998年10月-2003年4月收治的16例腹膜后軟組織急性腫瘤術后患者行大分割適形放射治療，設計臨床靶區等效生物劑量為55～62 Gy，觀察放療后2、5年局部控制率、生存率和無病生存情況。 結果 2、5年局部控制率較未行放療患者明顯提高并和其他放射治療方式達到較高治療劑量者近似；遠期生存無改善，無病生存率較未行放療患者有提高。 結論 大分割適形放射治療方式對腹膜后軟組織急性腫瘤術后患者有較好的局部控制作用，無瘤生存率有提高，遠期生存無改善，無嚴重的遠期放療后遺癥。【Abstract】 Objective To observe the effect of high-dose three-dimensional conformal radiotherapy combined with surgery on primary retroperitoneal soft tissue sarcoma. Methods A total of 16 patients with primary retroperitoneal soft tissue sarcoma underwent high-dose three-dimensional conformal radiotherapy after sarcoma excision from October 1998 to April 2003. The biologically effective dose was 55-62 Gy for CTV. The local control rate and long-term survival rate and disease free survival after 2 and 5 years were observed. Results The local control rate obviously raised in these patients after 2 and 5 years; but the long-term survival rate didn’t improve and the disease free survival improved in these patients compared with those wasn’t radiated. Conclusion High-dose three-dinensional comfomal radiotherapy is effective on the patients with retroperitoneal soft tissue sarcoma in local control rate and disease free survival, but long-term survival rate is not improved and the side-effect is not serious.
