Comprehensive evaluation of dosimetric impact against position errors in accelerator-based BNCT under different treatment parameter settings.
Comprehensive evaluation of dosimetric impact against position errors in accelerator-based BNCT under different treatment parameter settings.
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DOI：
10.1002/mp.15823
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发表时间：
2022-08
期刊：
影响因子：
3.8
通讯作者：
Ono, Koji
中科院分区：
文献类型：
--
作者：
Kakino, Ryo;Hu, Naonori;Isohashi, Kayako;Aihara, Teruhito;Nihei, Keiji;Ono, Koji
关键词：
以加速器为基础的(AB)硼中子俘获治疗(BNCT)治疗头颈部癌症的患者在坐位时通常会感到不舒服，而且患者在这种治疗过程中的运动可能比其他放射治疗技术更大。此外，BNCT的治疗时间相对较长(最长可达1小时左右)，这增加了患者在治疗过程中移动的可能性。由于大多数BNCT照射是在单个部分进行的，患者运动引起的剂量学误差更严重，需要评估和考虑。BNCT剂量计算需要几个治疗参数。为研究AB-BNCT系统在不同治疗参数设置下，使用简单的圆柱体体模对位置误差的剂量学影响。治疗计划在RayStation中创建，并使用NeuCure®剂量引擎进行剂量计算。建立了直径16 cm×高20 cm的软组织圆柱体模型。假性肿瘤为直径3 cm的球体，分别位于2.5和6.5 cm的深度(分别表示为T2.5和T6.5)。通过设置以下参数创建参考计划：准直器直径=10、12或15厘米，准直器到表面的距离(CSD)=4.0或8.0厘米，使用18F-氟-硼-苯丙氨酸的肿瘤与血液的比率(T/B比)=2.5或5.0，以及血液中的10B浓度=0.20、25或30 ppm。T2.5和T6.5的处方剂量均为D95%≥+20Gyeq。在参考平面的基础上，在26个方向[左-右(LR)、前-后(AP)和上-下(SI)方向的所有组合)和3个距离(1.0、2.0和3.0 cm)上创建幻影移位平面。DI值为80%的肿瘤。通过进行多元回归分析(MRA)和必要时的其他分析，评估DI在LR、AP和SI方向上的移位方向相关性。对于T2.5，LR、AP和SI移位的DIS的MRA系数分别为−0.08、2.16和−0.04(p值分别为0.084、0.01和0.334)；对于T6.5的−分别为0.05、2.08和0.15(p值分别为0.526、0.01和0.065)。方差分析表明，在T2.5上，较小的准直器尺寸和在T6.5上的CSD较小时，由于AP漂移引起的DIS显著增大。根据学生t检验，在T2.5和T6.5上，较小的准直器尺寸以及T2.5上较小的CSD，由于SI或LR(横向)移位而导致的剂量减少显著更大。不同T/B比和10B浓度对AP移位和侧向移位的影响差异无统计学意义。DIS受AP方向移动的影响较大，并受不同处理参数的影响。
Patients who undergo accelerator‐based (AB) boron neutron capture therapy (BNCT) for head and neck cancer in the sitting position are generally uncomfortably immobilized, and patient motion during this treatment may be greater than that in other radiotherapy techniques. Furthermore, the treatment time of BNCT is relatively long (up to approximately 1 h), which increases the possibility of patient movement during treatment. As most BNCT irradiations are performed in a single fraction, the dosimetric error due to patient motion is of greater consequence and needs to be evaluated and accounted for. Several treatment parameters are required for BNCT dose calculation. To investigate the dosimetric impacts (DIs) against position errors using a simple cylindrical phantom for an AB‐BNCT system under different treatment parameter settings. The treatment plans were created in RayStation and the dose calculation was performed using the NeuCure® dose engine. A cylindrical phantom (16 cm diameter × 20 cm height) made of soft tissue was modeled. Dummy tumors in the form of a 3‐cm‐diameter sphere were arranged at depths of 2.5 and 6.5 cm (denoted by T 2.5 and T 6.5, respectively). Reference plans were created by setting the following parameters: collimator size = 10, 12, or 15 cm in diameter, collimator‐to‐surface distance (CSD) = 4.0 or 8.0 cm, tumor‐to‐blood ratio (T/B ratio) using 18F‐fluoro‐borono‐phenylalanine = 2.5 or 5.0, and 10B concentration in blood = 20, 25, or 30 ppm. The prescribed dose was D 95% ≥ 20 Gy‐eq for both T 2.5 and T 6.5. Based on the reference plans, phantom‐shifted plans were created in 26 directions [all combinations of left–right (LR), anterior–posterior (AP), and superior–inferior (SI) directions) and three distances (1.0, 2.0, and 3.0 cm). The DIs were evaluated at D 80% of the tumors. The shift direction dependency of the DI in the LR, AP, and SI directions was evaluated by conducting a multiple regression analysis (MRA) and other analyses where required. The coefficients of the MRA of the DIs for LR, AP, and SI shifts were −0.08, 2.16, and −0.04 (p‐values = 0.084, <0.01, and 0.334) for T 2.5 and −0.05, 2.08, and 0.15 (p‐values = 0.526, <0.01, and 0.065) for T 6.5, respectively. The analysis of variance showed that DIs due to the AP shift were significantly greater for smaller collimator sizes on T 2.5 and smaller CSD on T 6.5. Dose reduction due to SI or LR (lateral) shifts was significantly greater for smaller collimator sizes on both T 2.5 and T 6.5 and smaller CSD on T2.5, according to the Student's t‐test. There were no significant differences in the DIs against both the AP shift and the lateral shift between the different T/B ratios and 10B concentrations. The DIs were largely affected by the shift in the AP direction and were influenced by the different treatment parameters.
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影响因子：
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