【摘要】 目的 研究千伏級錐形束CT（kV-cone beam CT，kV-CBCT）影像用于鼻咽癌調(diào)強放射治療計劃劑量計算的可行性和精確度。 方法 2010年7-9月7例鼻咽癌患者 ，獲取每例患者的第1天放射治療時的kV-CBCT影像。用CIRS062密度模體和患者自身特定區(qū)域亨氏單位值（hounsfield unit，HU）映射的兩種方法重新刻度亨氏單位值-相對電子密度（HU-RED）表，分別進行劑量計算，并與在傳統(tǒng)扇形束CT（FBCT）影像上的原放射治療計劃結(jié)果進行對比，包括輻射劑量分布、靶區(qū)和危及器官的劑量體積直方圖（DVH）。 結(jié)果 kV-CBCT影像的治療計劃和原治療計劃在劑量分布和DVH上有較好的一致性。在劑量分布的比較上采用了γ分析（2%/2 mm標準的通過率），用基于模體的HU-RED表得到的治療計劃與原治療計劃對比，在經(jīng)過等中心冠狀面、矢狀面和橫斷面的通過率分別為92.7%±3.5%、95.1%±3.1%和95.7%±3.4%，用基于患者的HU-RED表得到治療計劃與原治療計劃對比的通過率分別為94.8%±2.7%、96.6%±2.9%和97.4%±2.7%。DVH的統(tǒng)計數(shù)據(jù)表明，兩種方法得到的kV-CBCT治療計劃和原治療計劃相比較，靶區(qū)和危及器官劑量偏差大多數(shù)在2%以內(nèi)。有1例因在橫斷面發(fā)生了明顯的旋轉(zhuǎn)誤差，導(dǎo)致在橫斷面的通過率很低，DVH統(tǒng)計數(shù)據(jù)較原計劃偏差較大。 結(jié)論 kV-CBCT影像可以用來做輻射劑量計算，基于患者自身影像生成的HU-RED表的治療計劃較原治療計劃有更高的符合度。
【Abstract】 Objective To evaluate the feasibility and accuracy of dose calculation based on cone beam CT (CBCT) data sets for intensity modulated radiation therapy (IMRT) planning of nasopharyngeal cancer (NPC). Methods Seven NPC patients were selected. The kV-CBCT images for each patient were acquired on the first treatment day. Two correction strategies were used to generate the cone beam HU value vs relative electron density calibration tables which named CIRS062 phantom based HU-RED tables and patient specific HU-RED tables respectively for dose calculation. The dose distributions and dose volume histograms (DVHs) of the target and organs at risk (OAR) based on kV-CBCT images were compared to the plans based on the fan-beam CT (FBCT). Results The DVH and dose distribution comparison between plans based on the FBCT and those on the CBCT showed good agreements. The γ analysis with a criterion of 2 mm/2% was used for the comparison of dose distribution at the coronal plane, sagital plane and cross plane through the isocenter point. The passing rate from phantom based HU-RED tables were (92.7±3.5) %, (95.1±3.1) %, and (95.7±3.4)%, respectively. The passing rates from the patient specific HU-RED tables were (94.8±2.7) %, (96.6±2.9) %, and (97.4±2.7) %, respectively. The dose difference between plans based on CBCT and those based on FBCT was within 2% at most patients by analyzing DVH based parameters. Only one patient who had significant rotation setup error resulted in the low passing rate and disagreement in DVH. Conclusion The CBCT images can be used to do dose calculation in IMRT planning of NPC. The differences between plans based on HU-RED tables generated by specific patient and the original plans are less than those between plans based on CIRS062 phantom based HU-RED tables and the original plans.
引用本文： 吳魁,李光俊,蔣曉芹,王世超,王辛,柏森. 千伏級錐形束CT影像用于鼻咽癌調(diào)強放療計劃劑量計算的可行性. 華西醫(yī)學(xué), 2010, 25(12): 2156-2159. doi: 復(fù)制
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- 1. Ling CC, Yorke E, Fuks Z. From IMRT to IGRT: frontierland or neverland?[J]. Radiother Oncol, 2006, 78(2): 119-122.
- 2. 戴建榮, 胡逸明. 圖像引導(dǎo)放療的實現(xiàn)方式[J]. 中華放射腫瘤學(xué)雜志, 2006, 15(2), 132-135.
- 3. Yan D, Vicini F, Wong J, et al. Adaptive radiation therapy[J]. Phys Med Biol, 1997, 42(1): 123-132.
- 4. Yoo S, Yin FF. Dosimetric feasibility of cone-beam CT-based treatment planning compared to CT-based treatment planning[J]. Int J Radiat Oncol Biol Phys, 2006, 66, (5): 1553-1561.
- 5. Houser C, Nawaz AO, Galvin J, et al. Quantitive evaluation of cone beam CT data used for treatment planning[J]. Med Phys, 2006, 33(4): 2285-2286.
- 6. Richter A, Hu Q, Steglich D, et al. Investigation of the usability of conebeam CT data sets for dose calculation[J]. Radiat Oncol, 2008, 3: 42.
- 7. Fippel M. Fast monte carlo dose calculation for photon beams based on the VMC electron algorithm[J]. Med Phys, 1999, 26(8): 1466-1475.
- 8. Fippel M, Laub W, Huber B, et al. Experimental investigation of a fast monte carlo photon beam dose calculation algorithm[J]. Phys Med Biol, 1999, 44(12): 3039-3054.
- 9. Jaffray DA, Battista JJ, Fenster A, et al. X-ray scatter in megavoltage transmission radiography: physical characteristics and influence on image quality[J]. Med Phys, 1994, 21(1): 45-60.