Volumetric tumor burden and its effect on brachial plexus dosimetry in head and neck intensity-modulated radiotherapy

To determine the effect of gross tumor volume of the primary (GTV-P) and nodal (GTV-N) disease on planned radiation dose to the brachial plexus (BP) in head and neck intensity-modulated radiotherapy (IMRT). Overall, 75 patients underwent definitive IMRT to a median total dose of 69.96 Gy in 33 fractions. The right BP and left BP were prospectively contoured as separate organs at risk. The GTV was related to BP dose using the unpaired t-test. Receiver operating characteristics curves were constructed to determine optimized volumetric thresholds of GTV-P and GTV-N corresponding to a maximum BP dose cutoff of > 66 Gy. Multivariate analyses were performed to account for factors associated with a higher maximal BP dose. A higher maximum BP dose (> 66 vs ≤ 66 Gy) correlated with a greater mean GTV-P (79.5 vs 30.8 cc; p = 0.001) and ipsilateral GTV-N (60.6 vs 19.8 cc; p = 0.014). When dichotomized by the optimized nodal volume, patients with an ipsilateral GTV-N ≥ 4.9 vs < 4.9 cc had a significant difference in maximum BP dose (64.2 vs 59.4 Gy; p = 0.001). Multivariate analysis confirmed that an ipsilateral GTV-N ≥ 4.9 cc was an independent predictor for the BP to receive a maximal dose of > 66 Gy when adjusted individually for BP volume, GTV-P, the use of a low anterior neck field technique, total planned radiation dose, and tumor category. Although both the primary and the nodal tumor volumes affected the BP maximal dose, the ipsilateral nodal tumor volume (GTV-N ≥ 4.9 cc) was an independent predictor for high maximal BP dose constraints in head and neck IMRT.     

Quantitative Dosimetry for Yttrium-90 Radionuclide Therapy: Tumor Dose Predicts Fluorodeoxyglucose Positron Emission Tomography Response in Hepatic Metastatic Melanoma

PurposeTo assess a new method for generating patient-specific volumetric dose calculations and analyze the relationship between tumor dose and positron emission tomography (PET) response after radioembolization of hepatic melanoma metastases.Methods and MaterialsYttrium-90 (⁹⁰Y) bremsstrahlung single photon emission computed tomography (SPECT)/computed tomography (CT) acquired after ⁹⁰Y radioembolization was convolved with published ⁹⁰Y Monte Carlo estimated dose deposition kernels to create a three-dimensional dose distribution. Dose-volume histograms were calculated for tumor volumes manually defined from magnetic resonance imaging or PET/CT imaging. Tumor response was assessed by absolute reduction in maximum standardized uptake value (SUV_max) and total lesion glycolysis (TLG).ResultsSeven patients with 30 tumors treated with ⁹⁰Y for hepatic metastatic melanoma with available ⁹⁰Y SPECT/CT and PET/CT before and after treatment were identified for analysis. The median (range) for minimum, mean, and maximum dose per tumor volume was 16.9 Gy (5.7–43.5 Gy), 28.6 Gy (13.8–65.6 Gy) and 36.6 Gy (20–124 Gy), respectively. Response was assessed by fluorodeoxyglucose PET/CT at a median time after treatment of 2.8 months (range, 1.2–7.9 months). Mean tumor dose (P = .03) and the percentage of tumor volume receiving ≥ 50 Gy (P < .01) significantly predicted for decrease in tumor SUV_max, whereas maximum tumor dose predicted for decrease in tumor TLG (P < .01).ConclusionsVolumetric dose calculations showed a statistically significant association with metabolic tumor response. The significant dose-response relationship points to the clinical utility of patient-specific absorbed dose calculations for radionuclide therapy.     

MRI直方图在头颈部肿瘤诊断中应用的研究进展

肿瘤的精准评估是肿瘤影像学研究的关键点。随着高分辨率磁共振成像(magnetic resonance imaging,MRI)和信号处理方法的不断进步,利用磁共振功能成像结合影像组学方法在肿瘤诊断中受到广泛关注。MRI直方图分析是从标准影像数据中通过高通量算法提取定量参数特征来分析肿瘤整体的异质性,进一步开发诊断、预测与预后模型,为临床医生诊疗过程提供参考依据。本文就近年来MRI直方图在头颈部肿瘤异质性诊断及治疗效果评估、预测方面进行综述,并强调了不同磁共振成像技术直方图在头颈部肿瘤诊断中的研究进展。     

Risk factors for brain injury after carbon ion radiotherapy for skull base tumors

Background and purpose

This study aimed to determine the risk factors for radiation-induced brain injury (RIBI) after carbon ion radiotherapy (CIRT) for treating skull base tumors.

Materials and methods

Between April 1997 and January 2009, CIRT at a total dose of 48.0–60.8 Gy equivalent (GyE) was administered in 16 fractions to 47 patients with skull base tumors. Of these patients, 39 who were followed up with magnetic resonance imaging (MRI) for more than 24 months were analyzed. RIBI was assessed according to the MRI findings based on the Late Effects of Normal Tissue-Subjective, Objective, Management, Analytic criteria; clinical symptoms were assessed according to the Radiation Therapy Oncology Group/European Organisation for Research and Treatment of Cancer tables. The correlations of clinical and dosimetric parameters with incidence of ?grade 2 RIBI were retrospectively analyzed.

Results

The median follow-up period was 67 months. The 5-year actuarial likelihoods of ?grade 2 RIBI and ?grade 2 clinical symptoms were 24.5% and 7.0%, respectively. Multivariate analysis demonstrated that the brain volume receiving more than 50 GyE (V50) was a significant risk factor for the development of ?grade 2 RIBI (p = 0.004).

Conclusion

V50 was a significant risk factor for ?grade 2 RIBI after CIRT using a 16-fraction regimen.     

A Novel Approach to Speckle Reduction in Ultrasound Imaging

Speckle noise is inherent in ultrasound images, and it generally tends to reduce the resolution and contrast, thereby degrading the diagnostic accuracy of this modality. Speckle reduction is very important and critical for ultrasound imaging. In this paper, we propose a novel approach for speckle reduction using 2-D homogeneity and directional average filters. We have conducted experiments on numerous artificial images, clinic breast ultrasound images and vascular images. The experimental results are compared with that of other methods and the performance is evaluated using several merits, and they demonstrate that the proposed approach can reduce the speckle noise effectively without blurring the edges and damaging the textual information. It will be very useful for computer-aided diagnosis systems using ultrasound images. (E-mail: hengda.cheng@usu.edu)     

Ⅲ+Ⅳ期非小细胞肺癌三维适形放疗正常肺V_5、V_(10)预测放射性肺损伤前瞻性临床研究

目的 探讨非小细胞肺癌三维适形放疗正常肺低剂量体积对放射性肺损伤的预测作用.方法 采用三维适形后程加速超分割放疗经病理或细胞学证实的非小细胞肺癌患者100例.Ⅲ期14例,Ⅲb期36例,Ⅳ期50例.鳞癌49例,腺癌48例,腺鳞癌3例.初治79例、术后复发8例,术后残留12例,术后辅助1例.单纯放疗9例,放化疗91例.放疗剂量60～80 Gy,60～69 Gy 24例,≥70 Gy76例.化疗方案采用紫杉类+铂类一线方案.用剂量体积直方图计算正常肺V_5、V_(10)、V_(20)、V_(30)和平均肺剂量(MLD).肺损伤评估根据CTC 3.0标准.结果 全组V_5为37%～98%,中位值65%;V_(10)为27%～78%,中位值47.5%;V_(20)为17%～54%,中位值31%;V_(30)为9%～31%,中位值24%.100例患者中发生放射性肺炎(RP)1级34例,2级27例,3级8例,4级1例,5级1例.75例患者中发生放射性肺纤维化1级46例,2级14例,3级2例.V_5、V_(10)、V_(20)、MLD与≥1级RP相关,V_(5)、V_(20)、V_(30)、MLD与≥2级RP相关,V_5与≥3级RP相关.V_(5)、V_(20)、V_(30)、分别>65%、31%、24%时发生≥2级RP概率增加,V_(5)、V_(20)分别>65%、31%时发生≥3级RP概率增加,V_(20)>31%时发生≥1级RP概率增加.大体肿瘤体积、计划靶体积与≥1级RP、≥2级放射性肺纤维化相关.性别、年龄、临床分期、处方剂量、照射野数目与各级放射性肺损伤无关.结论 剂量体积参数V_(5)、V_(10)与RP发生相关,可能成为放射肺损伤有效的预测因子.     

Comparison between the ideal reference dose level and the actual reference dose level from clinical 3D radiotherapy treatment plans

Purpose

Retrospective study of 3D clinical treatment plans based on radiobiological considerations in the choice of the reference dose level from tumor dose-volume histograms.

Methods and materials

When a radiation oncologist evaluates the 3D dose distribution calculated by a treatment planning system, a decision must be made on the percentage dose level at which the prescribed dose should be delivered. Much effort is dedicated to deliver a dose as uniform as possible to the tumor volume. However due to the presence of critical organs, the result may be a rather inhomogeneous dose distribution throughout the tumor volume. In this study we use a formulation of tumor control probability (TCP) based on the linear quadratic model and on a parameter, the F factor. The F factor allows one to write TCP, from the heterogeneous dose distribution (TCP{(ε_j,D_j)}), as a function of TCP under condition of homogeneous irradiation of tumor volume (V) with dose D (TCP(V,D)). We used the expression of the F factor to calculate the “ideal” percentage dose level (iDL_r) to be used as reference level for the prescribed dose D delivery, so as to render TCP{(ε_j,D_j)} equal to TCP(V,D).The 3D dose distributions of 53 clinical treatment plans were re-evaluated to derive the iDL_r and to compare it with the one (D_tpL) to which the dose was actually administered.

Results

For the majority of prostate treatments, we observed a low overdosing following the choice of a D_tpL lower than the iDL_r. While for the breast and head-and-neck treatments, the method showed that in many cases we underdosed choosing a D_tpL greater than the iDL_r. The maximum difference between the iDL_r and the D_tpL was −3.24% for one of the head-and-neck treatments.

Conclusions

Using the TCP model, the probability of tumor control is compromised following an incorrect choice of D_tpL; so we conclude that the application of the F factor is an effective tool and clinical aid to derive the optimal reference dose level from the dose-volume histogram (DVH) of each treatment plan.     

A novel method for the evaluation of uncertainty in dose-volume histogram computation

PURPOSE: Dose-volume histograms (DVHs) are a useful tool in state-of-the-art radiotherapy treatment planning, and it is essential to recognize their limitations. Even after a specific dose-calculation model is optimized, dose distributions computed by using treatment-planning systems are affected by several sources of uncertainty, such as algorithm limitations, measurement uncertainty in the data used to model the beam, and residual differences between measured and computed dose. This report presents a novel method to take them into account. METHODS AND MATERIALS: To take into account the effect of associated uncertainties, a probabilistic approach using a new kind of histogram, a dose-expected volume histogram, is introduced. The expected value of the volume in the region of interest receiving an absorbed dose equal to or greater than a certain value is found by using the probability distribution of the dose at each point. A rectangular probability distribution is assumed for this point dose, and a formulation that accounts for uncertainties associated with point dose is presented for practical computations. RESULTS: This method is applied to a set of DVHs for different regions of interest, including 6 brain patients, 8 lung patients, 8 pelvis patients, and 6 prostate patients planned for intensity-modulated radiation therapy. CONCLUSIONS: Results show a greater effect on planning target volume coverage than in organs at risk. In cases of steep DVH gradients, such as planning target volumes, this new method shows the largest differences with the corresponding DVH; thus, the effect of the uncertainty is larger.     

直方图诊断脂肪肝的应用探讨

目的 探讨直方图对脂肪肝诊断的价值。方法 应用超声诊断仪中直方图功能，在70例脂肪肝患者的增强回声区中取样，获得直方图M值，与正常组50例健康人进行对照，判断有无数值上的差异。结果 正常组M值为25～49，70例脂肪肝患者M值为50～120，与正常组未显示有交叉。结论 直方图对脂肪肝的诊断具有临床价值。