Prediction of multi-criteria optimization (MCO) parameter efficiency in volumetric modulated arc therapy (VMAT) treatment planning using machine learning (ML)

PurposeTo predict the impact of optimization parameter changes on dosimetric plan quality criteria in multi-criteria optimized volumetric-modulated-arc therapy (VMAT) planning prior to optimization using machine learning (ML).MethodsA data base comprising a total of 21,266 VMAT treatment plans for 44 cranial and 18 spinal patient geometries was generated. The underlying optimization algorithm is governed by three highly composite parameters which model a combination of important aspects of the solution. Patient geometries were parametrized via volume- and shape properties of the voxel objects and overlap-volume histograms (OVH) of the planning-target-volume (PTV) and a relevant organ-at-risk (OAR). The impact of changes in one of the three optimization parameters on the maximally achievable value range of five dosimetric properties of the resulting dose distributions was studied. To predict the extent of this impact based on patient geometry, treatment site, and current parameter settings prior to optimization, three different ML-models were trained and tested. Precision-recall curves, as well as the area-under-curve (AUC) of the resulting receiver-operator-characteristic (ROC) curves were analyzed for model assessment.ResultsSuccessful identification of parameter regions resulting in a high variability of dosimetric plan properties depended on the choice of geometry features, the treatment indication and the plan property under investigation. AUC values between 0.82 and 0.99 could be achieved. The best average-precision (AP) values obtained from the corresponding precision/recall curves ranged from 0.71 to 0.99.ConclusionsMachine learning models trained on a database of pre-optimized treatment plans can help finding relevant optimization parameter ranges prior to optimization.     

Comparison of the RayStation photon Monte Carlo dose calculation algorithm against measured data under homogeneous and heterogeneous irradiation geometries

PurposeThis work compares Monte Carlo dose calculations performed using the RayStation treatment planning system against data measured on a Varian Truebeam linear accelerator with 6 MV and 10 MV FFF photon beams.MethodsThe dosimetric performance of the RayStation Monte Carlo calculations was evaluated in a variety of irradiation geometries employing homogeneous and heterogeneous phantoms. Profile and depth dose comparisons against measurement were carried out in relative mode using the gamma index as a quantitative measure of similarity within the central high dose regions.ResultsThe results demonstrate that the treatment planning system dose calculation engine agrees with measurement to within 2%/1 mm for more than 95% of the data points in the high dose regions for all test cases. A systematic underestimation was observed at the tail of the profile penumbra and out of field, with mean differences generally <0.5 mm or 1% of curve dose maximum respectively. Out of field agreement varied between evaluated beam models.ConclusionsThe RayStation implementation of photon Monte Carlo dose calculations show good agreement with measured data for the range of scenarios considered in this work and is deemed sufficiently accurate for introduction into clinical use.     

A patient immobilization device for prone breast radiotherapy: Dosimetric effects and inclusion in the treatment planning system

PurposeTo assess the dosimetric impact of a patient positioning device for prone breast radiotherapy and assess the accuracy of a treatment planning system (TPS) in predicting this impact.MethodsBeam attenuation and build-up dose perturbations, quantified by ionization chamber and radiochromic film dosimetry, were evaluated for 3 components of the patient positioning device: the carbon fiber baseplate, the support cushions and the support wedge for the contralateral breast. Dose calculations were performed using the XVMC dose engine implemented in the Monaco TPS. All components were included during planning CT acquisition.ResultsBeam attenuation amounted to 7.57% (6 MV) and 5.33% (15 MV) for beams obliquely intersecting the couchtop–baseplate combination. Beams traversing large sections of the support wedge were attenuated by 12.28% (6 MV) and 9.37% (15 MV). For the support cushion foam, beam attenuation remained limited to 0.11% (6 MV) and 0.08% (15 MV) per centimeter thickness. A substantial loss of dose build-up was detected when irradiating through any of the investigated components. TPS dose calculations accurately predicted beam attenuation by the baseplate and support wedge. A manual density overwrite was needed to model attenuation by the support cushion foam. TPS dose calculations in build-up regions differed considerably from measurements for both open beams and beams traversing the device components.ConclusionsIrradiating through the components of the positioning device resulted in a considerable degradation of skin sparing. Inclusion of the device components in the treatment planning CT allowed to accurately model the most important attenuation effect, but failed to accurately predict build-up doses.     

Unintended irradiation of internal mammary chain – Is that enough?

Aim

To evaluate the unintentional coverage of the internal mammary chain (IMC) with tangential fields irradiation to the breast, and its relation with the type of surgery employed.

Background

The dose distribution in regions adjacent to the treatment targets (mammary gland or chest wall), with incidental irradiation of the IMC, could translate into clinical benefit, due to the proximity of these regions.

Materials and methods

One hundred and twelve consecutive conformal radiotherapy plans were correlating the average dose to the IMC with the type of surgery employed, the extent of disease and the irradiation techniques.

Results

The mean doses to IMC after modified radical mastectomy (MRM), modified radical mastectomy with immediate reconstruction (MRM + R), and breast conservative surgery (BCS) were 30.34 Gy, 30.26 Gy, and 18.67 Gy, respectively. Significant differences were identified between patients who underwent MRM or MRM + R over BCS (p = 0.01 and 0.003, respectively), but not between MRM and MRM + R (p = 0.88). Mean doses to IMC were greater in patients with T3–T4 tumors when compared with more initial stages (≤T2) (p = 0.0096). The lymph node involvement also correlated with higher average doses to IMC (node positive: 26.1 Gy × node negative: 17.8 Gy, p = 0.0017).

Conclusions

The moderate dose level to the IMC in the unintentional irradiation scenario seems to be insufficient to treat the subclinical disease, although it could have an impact in patients undergoing mastectomy.     

鼻咽癌放疗患者生命质量的相关影响因素研究

目的:探讨放疗对鼻咽癌(NPC)患者生命质量的影响及影响NPC患者生命质量因素。方法:选择2011年10月到2014年10月在我院接受三维适形放疗(3DCRT)或调强放疗(IMRT)的160例首次治疗NPC患者,随机分为3DCRT组和IMRT组,各80例。3DCRT组采用3DCRT治疗,IMRT组采用IMRT治疗。采用生命质量测定量表(QLQ-C30)分别在治疗结束时、治疗结束后3个月、治疗结束后1年对两组患者进行问卷调查,分析影响NPC患者总体生命质量的危险因素。结果:在不同时间点,IMRT组患者的总体生命质量评分、社会功能评分、家庭经济评分均明显低于3DCRT组(P0.05)。经过非条件二分类Logistic回归分析显示,影响NPC患者总体生命质量的因素有放疗方式、年龄、是否同期化疗及经济状况。结论:与3DCRT组相比,IMRT能改善患者总体生命质量、社会功能等,放疗方式、年龄、是否同期化疗及经济状况是NPC患者生命质量的影响因素。     

姜黄素对晚期宫颈癌患者Bcl-xL、Bcl-2、EphA2及EphrinA1表达的影响

目的:探究姜黄素对宫颈癌晚期放疗患者Bcl-x L、Bcl-2、Eph A2与Ephrin A1表达的影响。方法:收集160例晚期宫颈癌放疗患者的宫颈癌石蜡标本,分为姜黄素组与对照组,均给予放射治疗,姜黄素组放疗期间加服姜黄素片剂,采用免疫组化等实验方法,观察两组病例标本Bcl-x L、Bcl-2、Eph A2与Ephrin A1的表达情况,比较两组病理标本化疗前后的凋亡细胞指数(AI)与微血管密度(MVD)。结果:姜黄素组的Bcl-x L、Bcl-2、Eph A2与Ephrin A1的表达阳性率分别为8.3%、43.33%、46.67%、15.0%,均显著低于对照组(P0.05);放疗后姜黄素组的AI显著高于对照组(P0.05),MVD显著低于对照组(P0.05)。结论:姜黄素可抑制Bcl-x L、Bcl-2的表达以促进肿瘤细胞凋亡,同时降低Eph A2与Ephrin A1的表达以减少肿瘤微血管形成,有显著的抗肿瘤与放疗增敏作用。     

表面增强激光解吸电离飞行时间质谱技术筛查肺癌血清特异性蛋白质及其临床意义

目的:探讨用表面增强激光解吸电离飞行时间质谱(SELDI-TOF-MS)技术筛查肺癌血清特异性蛋白质的临床意义。方法:应用SELDI-TOF-MS对35例正常对照组、43例治疗前肺癌病人的血清样品进行蛋白质指纹图谱测定,用BioMarker Wizard 3．01及BioMarker Parrern System 5．01分析软件对测得的数据进行处理及建立诊断模型。结果:共检测到251个蛋白质峰,筛选出差异蛋白质峰11个,以质荷比(m/z)分别为M2799_26,M3227_41,M5739_70和M8164_30的4个蛋白质峰为依据组合构建分类决策树模型,分出5个终节点。决策树模型的原始判别总准确率为91．0%(71/78),敏感性为88．4%(38/43),特异性为94．3%(33/35);交叉验证总准确率为85．9%(67/78),敏感性为88．4%(38/43),特异性为82．9%(29/35)。结论:SELDI-TOF-MS在肺癌血清特异性蛋白质的筛选及诊断模型的建立有一定的临床意义。     

支架置入技术治疗食道癌的临床疗效及预后

目的:观察支架置入法对食道癌患者的治疗效果及预后情况。方法:选取我院收治的食道癌患者共104例,根据治疗手段分为两组,其中对照组52例采用70 Gγ7/周治疗方案;实验组52例给予支架置入法治疗。对两组患者的梗阻改善情况、生存质量评分、并发症及生存情况进行统计分析。结果:1治疗后,两组患者的梗阻情况以及生存质量均得到有效改善,实验组患者的梗阻总缓解率为92.31%,生存质量评分为42.61±5.23分,均显著高于对照组,差异具有显著性(P0.05);2实验组患者的不良反应发生率(36.54%)与对照组(38.48%)比较无统计学差异(P0.05);3两组患者的3个月及6个月时的生存率相接近,但是实验组患者12个月生存率(71.7%)显著低于对照组(82.7%),差异具有统计学意义(P0.05)。结论:支架置入法能够显著改善食道癌患者的梗阻症状,提高患者生存质量,是较为安全可靠的缓解食道狭窄方法。     

Lung cancer. Radiotherapy in lung cancer: Actual methods and future trends

This survey is performed to update knowledge about methods and trends in lung cancer radiotherapy. A significant development has been noticed in radiotherapeutic techniques, but also in the identification of clinical prognostic factors. The improvement in the therapeutic line includes: application of the four-dimensional computer tomography (4DCT), taking advantage of positron emission tomography (PET-CT), designing of new computational algorithms, allowing more precise irradiation planning, development of treatment precision verification systems and introducing IMRT techniques in chest radiotherapy. The treatment outcomes have improved with high dose radiotherapy, but other fractionation alternations have been investigated as well.     

In-vivo dosimetry comparison of supraclavicular junction dose for breast and chest-wall patients with and without deep inspiration breath hold (DIBH)

PurposeThe use of deep inspiration breath-hold (DIBH) for patients with left-sided breast cancer reduces cardiac dose, with the aim of reducing the risk of major coronary events. However, this technique has not been universally adopted for patients requiring regional nodal irradiation (RNI) with one concern related to the junction dose. This study evaluates the dose received at the junction for both DIBH and free-breathing patients having tangential breast/chest wall radiation and regional nodal radiation treated with 3D-conformal or hybrid IMRT radiotherapy.MethodsIn-vivo dosimetry measurements utilizing EBT3 GafChromic™ film were performed for 19 patients during three fractions over their course of treatment. The mean junction dose and variability in junction dose were compared between the DIBH and free breathing patients.ResultsOur results show that for voluntary DIBH (v-DIBH) patients the junction dose is more variable between fractions. However, when comparing the average junction dose for DIBH and free breathing patients over the three measurements, the difference was small and not statistically significant. A larger difference was seen when patient measurements were analysed based on treatment linac.ConclusionsThese results show that the mean junction dose is not significantly compromised by the use of v-DIBH. The small possibility of a change in junction dose due to breathing technique should be weighed against the proven increased risks associated with excess cardiac dose received by free-breathing patients. If junction dose is of concern, an in-vivo study, such as this one, could allow cautious introduction of DIBH for patients requiring supraclavicular irradiation.