Development of Simplified Auto-Segmentable Functional Cardiac Atlas

PurposeThere is increasing evidence that radiation doses to cardiac substructures are associated with cardiac adverse events. Manual delineation of cardiac substructures is time-consuming, and auto-segmentation of cardiac substructure atlases has consequently been evaluated. However, proper automatic delineation of small substructures, such as the left anterior descending coronary artery, is challenging, and auto-segmentation of cardiac conduction system substructures has never been evaluated, despite multiple reports of radiation-induced arrhythmia after thoracic irradiations. The aim of this study was to propose and evaluate a simplified auto-segmentable functional cardiac atlas.Methods and MaterialsWe created a cardiac substructure atlas based on 20 computed tomography scans from patients with breast cancer comprising the 4 cardiac cavities, a high-risk cardiac zone as a left anterior descending coronary artery surrogate, and the 2 cardiac conduction nodes. Automatic delineation of this atlas by an atlas-based auto-segmentation algorithm was evaluated on a validation data set, consisting of 20 additional computed tomography scans. Dice similarity coefficients were used to evaluate the concordance level between the manual and the automatic contours; a dosimetric comparison between mean and maximum doses to the manual and to the auto-segmented substructures was additionally performed, based on intensity modulated radiation therapy treatment plans of the patients of the validation set.ResultsAverage dice similarity coefficient values were 0.78 for the 4 cardiac cavities, 0.65 for the high-risk cardiac zones, 0.56 for the sinoatrial node, and 0.15 for the atrioventricular node. Compared with manual contours, auto-segmented substructures were slightly smaller but the dosimetric parameters were similar.ConclusionsWe proposed a simplified functional cardiac atlas that included the cardiac conduction system and circumvented coronary delineation difficulties by using a surrogate high-risk cardiac zone. Most cardiac substructures were associated with acceptable atlas-based auto-segmentation properties. Such an atlas could be used for epidemiologic studies and for clinical practice.     

Evaluating cardiac substructure radiation exposure in breast rotational intensity modulated radiation therapy: Effects of cancer laterality,fractionation and deep inspiration breath-hold

PurposeRotational intensity-modulated radiation therapy currently has a growing role in breast cancer radiation therapy, since this radiation technique reduces cardiac radiation exposure while homogeneously covering target volumes. This study aims to evaluate radiation exposure of cardiac substructures across a broad spectrum of breast cancer cases differing by cancer laterality, fractionation regimen and addition of deep-inspiration breath hold.Materials and methodsCardiac substructures were delineated following guidelines endorsed by the European Society for Radiotherapy and Oncology (ESTRO) for forty-four breast cancer patients having undergone conserving surgery and adjuvant rotational intensity-modulated radiation therapy. Target volumes consisted of the whole breast with a boost, axillary and internal mammary nodes. Patients were treated using free-breathing technique for left-sided or right-sided, normofractionated or hypofractionated helical tomotherapy or volumetric modulated arc therapy, or using deep-inspiration breath hold for left-sided normofractionated volumetric modulated arc therapy. Mean and maximum doses to cardiac substructures were retrieved. Correlations were performed between mean- and maximum radiation doses to cardiac substructures.ResultsLeft-sided and right-sided irradiations were associated with different cardiac substructure exposure patterns despite comparable mean heart dose: 7.21 Gy for left-sided normofractionated regimen, 6.28 Gy for right-sided normofractionated regimen. Deep-inspiration breath hold reduced mean doses to almost all cardiac substructures for left-sided irradiation, but did not decrease maximum doses to coronary arteries. Correlations between mean- and maximum doses to cardiac substructures were usually moderate, but stronger for right-sided irradiation.ConclusionDespite comparable mean heart dose, cardiac substructure radiation exposure patterns with rotational intensity-modulated radiation therapy strongly depend on the breast side, which could trigger clinically different long-term cardiotoxicity events. Deep-inspiration breath hold improves cardiac substructure dosimetry. Mean- and maximum heart dose could probably not be used as surrogate markers for precise cardiac substructure evaluation. In a near future, clinical practice and cardiotoxicity studies could possibly gain by considering cardiac substructure in a more systematic manner, possibly relying on cardiac autosegmentation algorithms.     

Auto-segmentation of low-risk clinical target volume for head and neck radiation therapy

PurposeTo investigate atlas-based auto-segmentation methods to improve the quality of the delineation of low-risk clinical target volumes (CTVs) of unilateral tonsil cancers.Method and MaterialsSixteen patients received intensity modulated radiation therapy for left tonsil tumors. These patients were treated by a total of 8 oncologists, who delineated all contours manually on the planning CT image. We chose 6 of the patients as atlas cases and used atlas-based auto-segmentation to map each the atlas CTV to the other 10 patients (test patients). For each test patient, the final contour was produced by combining the 6 individual segmentations from the atlases using the simultaneous truth and performance level estimation algorithm. In addition, for each test patient, we identified a single atlas that produced deformed contours best matching the physician's manual contours. The auto-segmented contours were compared with the physician's manual contours using the slice-wise Hausdorff distance (HD), the slice-wise Dice similarity coefficient (DSC), and a total volume overlap index.ResultsNo single atlas consistently produced good results for all 10 test cases. The multiatlas segmentation achieved a good agreement between auto-segmented contours and manual contours, with a median slice-wise HD of 7.4 ± 1.0 mm, median slice-wise DSC of 80.2% ± 5.9%, and total volume overlap of 77.8% ± 3.3% over the 10 test cases. For radiation oncologists who contoured both the test case and one of the atlas cases, the best atlas for a test case had almost always been contoured by the oncologist who had contoured that test case, indicating that individual physician's practice dominated in target delineation and was an important factor in optimal atlas selection.ConclusionsMultiatlas segmentation may improve the quality of CTV delineation in clinical practice for unilateral tonsil cancers. We also showed that individual physician's practice was an important factor in selecting the optimal atlas for atlas-based auto-segmentation.     

Prospective assessment of an atlas-based intervention combined with real-time software feedback in contouring lymph node levels and organs-at-risk in the head and neck: Quantitative assessment of conformance to expert delineation

PurposeA number of studies have previously assessed the role of teaching interventions to improve organ-at-risk (OAR) delineation. We present a preliminary study demonstrating the benefit of a combined atlas and real time software-based feedback intervention to aid in contouring of OARs in the head and neck.Methods and MaterialsThe study consisted of a baseline evaluation, a real-time feedback intervention, atlas presentation, and a follow-up evaluation. At baseline evaluation, 8 resident observers contoured 26 OARs on a computed tomography scan without intervention or aid. They then received feedback comparing their contours both statistically and graphically to a set of atlas-based expert contours. Additionally, they received access to an atlas to contour these structures. The resident observers were then asked to contour the same 26 OARs on a separate computed tomography scan with atlas access. In addition, 6 experts (5 radiation oncologists specializing in the head and neck, and 1 neuroradiologist) contoured the 26 OARs on both scans. A simultaneous truth and performance level estimation (STAPLE) composite of the expert contours was used as a gold-standard set for analysis of OAR contouring.ResultsOf the 8 resident observers who initially participated in the study, 7 completed both phases of the study. Dice similarity coefficients were calculated for each user-drawn structure relative to the expert STAPLE composite for each structure. Mean dice similarity coefficients across all structures increased between phase 1 and phase 2 for each resident observer, demonstrating a statistically significant improvement in overall OAR-contouring ability (P < .01). Additionally, intervention improved contouring in 16/26 delineated organs-at-risk across resident observers at a statistically significant level (P ≤ .05) including all otic structures and suprahyoid lymph node levels of the head and neck.ConclusionsOur data suggest that a combined atlas and real-time feedback-based educational intervention detectably improves contouring of OARs in the head and neck.     

Validation of a Fully Automated Hybrid Deep Learning Cardiac Substructure Segmentation Tool for Contouring and Dose Evaluation in Lung Cancer Radiotherapy

Background and purposeAccurate and consistent delineation of cardiac substructures is challenging. The aim of this work was to validate a novel segmentation tool for automatic delineation of cardiac structures and subsequent dose evaluation, with potential application in clinical settings and large-scale radiation-related cardiotoxicity studies.Materials and methodsA recently developed hybrid method for automatic segmentation of 18 cardiac structures, combining deep learning, multi-atlas mapping and geometric segmentation of small challenging substructures, was independently validated on 30 lung cancer cases. These included anatomical and imaging variations, such as tumour abutting heart, lung collapse and metal artefacts. Automatic segmentations were compared with manual contours of the 18 structures using quantitative metrics, including Dice similarity coefficient (DSC), mean distance to agreement (MDA) and dose comparisons.ResultsA comparison of manual and automatic contours across all cases showed a median DSC of 0.75–0.93 and a median MDA of 2.09–3.34 mm for whole heart and chambers. The median MDA for great vessels, coronary arteries, cardiac valves, sinoatrial and atrioventricular conduction nodes was 3.01–8.54 mm. For the 27 cases treated with curative intent (planned target volume dose ≥50 Gy), the median dose difference was –1.12 to 0.57 Gy (absolute difference of 1.13–3.25%) for the mean dose to heart and chambers; and –2.25 to 4.45 Gy (absolute difference of 0.94–6.79%) for the mean dose to substructures.ConclusionThe novel hybrid automatic segmentation tool reported high accuracy and consistency over a validation set with challenging anatomical and imaging variations. This has promising applications in substructure dose calculations of large-scale datasets and for future studies on long-term cardiac toxicity.     

Autosegmentation of cardiac substructures in respiratory-gated,non-contrasted computed tomography images

BACKGROUNDRadiation dose to specific cardiac substructures can have a significant on treatment related morbidity and mortality, yet definition of these structures is labor intensive and not standard. Autosegmentation software may potentially address these issues, however it is unclear whether this approach can be broadly applied across different treatment planning conditions. We investigated the feasibility of autosegmentation of the cardiac substructures in four-dimensional (4D) computed tomography (CT), respiratory-gated, non-contrasted imaging.AIMTo determine whether autosegmentation can be successfully employed on 4DCT respiratory-gated, non-contrasted imaging.METHODSWe included patients who underwent stereotactic body radiation therapy for inoperable, early-stage non-small cell lung cancer from 2007 to 2019. All patients were simulated via 4DCT imaging with respiratory gating without intravenous contrast. Generated structure quality was evaluated by degree of required manual edits and volume discrepancy between the autocontoured structures and its edited sister structure.RESULTSInitial 17-structure cardiac atlas was generated with 20 patients followed by three successive iterations of 10 patients using MIM software. The great vessels and heart chambers were reliably autosegmented with most edits considered minor. In contrast, coronary arteries either failed to be autosegmented or the generated structures required major alterations necessitating deletion and manual definition. Similarly, the generated mitral and tricuspid valves were poor whereas the aortic and pulmonary valves required at least minor and moderate changes respectively. For the majority of subsites, the additional samples did not appear to substantially impact the quality of generated structures. Volumetric analysis between autosegmented and its manually edited sister structure yielded comparable findings to the physician-based assessment of structure quality.CONCLUSIONThe use of MIM software with 30-sample subject library was found to be useful in delineating many of the heart substructures with acceptable clinical accuracy on respiratory-gated 4DCT imaging. Small volume structures, such as the coronary arteries were poorly autosegmented and require manual definition.     

A dosimetric comparative study following RTOG and ESTRO contouring guidelines for breast radiation therapy

PurposeTo compare the dosimetric parameters considering the Radiation Therapy Oncology Group (RTOG) and European Society for Radiotherapy and Oncology (ESTRO) guidelines for breast cancer radiotherapy. Two radiotherapy techniques, intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT), were considered.Patients and methodsTwenty-eight patients with left-sided medially-located TanyN2M0 tumors were contoured based on RTOG and ESTRO guidelines. 9-field IMRT, 10-field IMRT, 11-field IMRT, and VMAT treatment plans were applied as radiotherapy (RT) techniques for both contouring sets. The dosimetric parameters of the RT plans were extracted and compared.ResultsComparing dose-volume histogram (DVH) parameters, equivalent uniform dose (EUD), and normal tissue complication probability (NTCP) of OARs across the contouring guidelines and considering each RT technique showed that the only significant differences were higher D_max, D_mean, V₃₀, and V₄₅, EUD, and NTCP of the thyroid in all treatment modalities when the RTOG guideline had been adopted. Using the VMAT technique, PTV's EUD and the tumor control probability (TCP) were considerably higher when the ESTRO guideline was adopted. Moreover, the conformity index (CI) of VMAT plans was significantly higher when the ESTRO guideline was used.ConclusionUnless having higher doses to thyroid when the RTOG guideline was adopted, the doses to other organs-at-risk (OAR) were similar between the two considering guidelines. Moreover, except for higher EUD, TCP, and CI for VMAT when the ESTRO guideline was used, no other significant differences were obtained between dosimetric parameters of target volumes considering the RT techniques and contouring guidelines.     

自动轮廓勾画软件构建图谱库在宫颈癌放疗中应用探讨

目的 探讨宫颈癌放疗中自动轮廓勾画软件中图谱数据库模板的最优构建模式,并检验其有效性和准确性。方法 本研究采用MIM自动勾画软件,在临床中分别选取20、40、60、80、100、120例宫颈癌患者CT图像及结构文件构建相应的图谱库模板。另选20例宫颈癌患者比较自动勾画与手动勾画差异,并使用单因素方差分析、随机区组方差分析和最小显著性差异t检验。利用时间计数、形状相似系数、交叉系数分析图谱库模板数目及患者CT扫描层数对MIM软件自动勾画所用时间及结果准确度的影响。结果 以专家手工勾画结果为参考,模板数目对该软件勾画结果的准确性及软件自动勾画所需时间均无影响(P均>0.05);待进行靶区勾画患者所扫描CT层数<65层时自动勾画所用时间较短(P=0.000),但导致直肠区域勾画结果准确性下降。当患者CT扫描层数达到67层时可使结肠区域自动勾画结果的准确性达到最高(P=0.037)。结论 应用MIM软件对宫颈癌患者进行靶区自动勾画时构建图谱库的模板数目推荐为20例;待勾画靶区包括膀胱、股骨、脊髓时患者所扫描的CT层数推荐为65层,待勾画靶区包括直肠时推荐为67层。     

ABAS软件勾画OAR临床前测试重要性研究

目的 对基于模板自动分区(ABAS)算法的图像勾画软件进行临床前测试,评估鼻咽癌放疗计划OAR勾画精度,为确定临床应用条件提供依据。方法 以放疗医师在22例鼻咽癌患者放疗计划CT图像上手工勾画的OAR结构为评价标准,分别对ABAS软件两种算法(General和Head/Neck)自动勾画的OAR进行以下测试:(1)每1例患者均拷贝1套图像,以原图像上手工勾画的轮廓为模板在拷贝图像上自动勾画,考察自动勾画对模板的还原能力;(2)以1例患者图像上手工勾画的轮廓为模板,对其余患者图像进行自动勾画,考察采用单一模板对不同患者图像自动勾画的准确度。评价指标包括各OAR的DSC、V_diff、DSC与勾画体积相关性,以及自动勾画加手工修改与单纯手工勾画的耗时差别。Wilcoxon符号秩检验,Spearman相关性分析。结果 Head/Neck算法对模板还原能力优于或相当于General算法,自动勾画DSC与所勾画结构体积大小呈正相关(r_s=0.879、0.939)。还原测试中体积>1 cm³器官自动勾画的DSC>0.8。使用Head/Neck算法基于单一模板的自动勾画中,脑干、颞叶、腮腺、下颌骨的DSC和V_diff平均值分别为0.81~0.90和2.73%~16.02%,颞颌关节和视交叉DSC为0.45~0.49。应用自动勾画加手工修改比单纯手工勾画可以节省68%时间。结论 临床前测试可以确定ABAS算法在特定临床应用条件的准确度和适用范围,所测试软件可帮助提高鼻咽癌放疗计划OAR勾画效率,但不适用于较小体积器官的勾画。     

基于参考图像的ABAS软件自动勾画技术在头颈部肿瘤中的应用研究

目的 评估ABAS软件对头颈部肿瘤自适应调强放疗患者基于CT图像自动勾画靶区与危及器官轮廓的吻合度.方法 对随机抽取的10例已勾画轮廓的头颈部肿瘤患者设计两种形变自动勾画方式,第1种对每例患者进行基于各自CT图像的形变自动勾画,第2种是随机抽取2例患者CT图像作为参考进行其余8例的形变自动勾画.利用形状相似性系数(DSC)及交叉指数(OI)评估自动勾画与人工勾画的吻合性,并行两种勾画方式差异配对t检验.结果 第1种的所有器官DSC和OI值均＞0.80,下颌骨均最高(＞0.91).大体肿瘤体积DSC值最低(0.81),临床靶体积的为0.82;而临床靶体积OI值最低(0.79),大体肿瘤体积的为0.82.第2种的只对危及器官进行勾画并将脊髓和脑干综合起来分析,所有DSC均在0.70左右,下颌骨DSC和Ol值均较高,这与其骨性解剖结构密切相关.第2种勾画结果中绝大多数明显低于第1种的(t =3.24 ～8.26,P=0.014 ～0.000),只有右腮腺接近有统计学意义水平(t=2.08,P=0.075).结论 ABAS软件用于自适应调强放疗患者的内部轮廓勾画可达到非常满意结果,而对常规调强放疗患者轮廓勾画应仔细选择参考图像以最大限度满足临床需要.     

Clinical evaluation of atlas and deep learning based automatic contouring for lung cancer

Background and purpose

Contouring of organs at risk (OARs) is an important but time consuming part of radiotherapy treatment planning. The aim of this study was to investigate whether using institutional created software-generated contouring will save time if used as a starting point for manual OAR contouring for lung cancer patients.

Evaluation of a software for automatic delineation of the mammary gland and organs at risk in patients treated for breast cancer in lateral position

Purpose of the studyThe purpose of this study was to assess the potential for improvement of routine breast and organs at risk contouring in patients treated in the lateral decubitus position using Workflow Box™ (Mirada Medical™, UK) automatic contouring software.Materials and methodsAutomatic contouring of the breast by this software is currently based on an atlas created from isodoses representing 95% of the prescribed dose in a population of patients previously treated at institut Curie. Forty cases of breast cancer (20 right breasts and 20 left breasts) were contoured by three radiation oncologists specialized in breast cancer, allowing the creation of a new atlas in the automatic contouring software. This study assessed the quality of contouring in 20 patients (ten right breasts and ten left breasts) by comparing manual contouring performed by the expert radiation oncologists (reference) with those generated by the old and new atlases developed at Institut Curie. The accuracy of contouring was assessed by overlap volume and the associated standard deviations.ResultsBreast contouring based on the new atlas and by radiation oncologists presented a mean overlap of 0.80 ± 0.09 for the right breast and 0.81 ± 0.06 for the left breast. By comparing volumes of interest contoured by radiation oncologists and those obtained from the old atlas, mean overlap volumes were 0.75 ± 0.08 and 0.74 ± 0.13 for the right and left breasts, respectively. Twenty cases (ten right breasts and ten left breasts) used to create the new atlas were also reprocessed by this same atlas in order to assess the quality of automatic contouring of the breast when the case was already known to the software. The mean overlap volume in this case was 0.84 ± 0.08 for the right breast and 0.83 ± 0.06 for the left breast. Finally, after automatic contouring of organs at risk by means of the new atlas, the mean overlap volume was 0.87 ± 0.04 for the heart and 0.93 for each lung (±0.05 for the right lung and ± 0.04 for the left lung).ConclusionWorkflow Box™ automatic contouring software, based on our new atlas provides reliable and clinically relevant organs at risk and breast contouring. The contours proposed by the software from the new atlas were better than those obtained with the previous atlas based on 95% isodoses obtained from old treatment plans. This software has therefore become more efficient, justifying its use in routine clinical practice for breast cancer contouring in patients treated in the lateral decubitus position. Investigations are currently underway to develop a fully automated process to ensure reliable, robust and operator-independent contouring and breast cancer treatment dosimetry in the lateral decubitus position. Promising preliminary results have already been obtained.     

A Radiation Therapy Contouring Atlas for Cardiac Conduction Node Delineation

PurposeThe heart is a complex organ at risk. Currently, radiation therapy cardiac delineation atlases do not include conduction system substructures, which exposure may clinically translate into arrhythmia and conduction disorders. We present a method to reproducibly delineate conduction nodes on noncontrast simulation computed tomography scans.Methods and MaterialsLocalization and dimensioning of the sinoatrial and atrioventricular nodes volumes on noncontrast simulation computed tomography scans were proposed based on radio-anatomic and histologic considerations and agreed upon by a multidisciplinary staff.ResultsThe proposed atlas enables the dosimetric evaluation of the sinoatrial and atrioventricular nodes exposure, and both contours correspond to 2-cm diameter spheres.ConclusionsThis delineation atlas should facilitate the delineation of cardiac conduction nodes in clinical research and daily practice.     

Electrocardiogram-Gated Computed Tomography with Coronary Angiography for Cardiac Substructure Delineation and Sparing in Patients with Mediastinal Lymphomas Treated with Radiation Therapy

Purpose(1) Demonstrate feasibility of electrocardiogram-gated computed tomography with coronary angiography (E-CTA) in treatment planning for mediastinal lymphoma and (2) assess whether inclusion of cardiac substructures in the radiation plan optimization (CSS optimization) results in increased cardiac substructure sparing.Methods and MaterialsPatients with mediastinal lymphomas requiring radiation therapy were prospectively enrolled in an observational study. Patients completed a treatment planning computed tomography scan and E-CTA in the deep inspiration breath hold position. Avoidance structures (eg, coronary arteries and cardiac valves) were created in systole and diastole and then merged into a single planning organ-at-risk volume based on a cardiac substructure contouring atlas. In the photon cohort, 2 volumetric modulated arc therapy plans were created per patient with and without CSS optimization. Dosimetric endpoints were compared.ResultsIn the photon cohort, 7 patients were enrolled. For all 7 patients, the treating physician elected to use the CSS optimization plan. At the individual level, 2 patients had reductions of 10.8% and 16.2% of the right coronary artery receiving at least 15 Gy, and 1 had a reduction of 9.6% of the left anterior descending artery receiving 30 Gy. No other differences for coronary arteries were detected between 15 and 30 Gy. Conversely, 5 of 7 patients had >10% reductions in dose between 15 to 30 Gy to at least 1 cardiac valve. The greatest reduction was 22.8% of the aortic valve receiving at least 30 Gy for 1 patient. At the cohort level, the maximum, mean, and 5-Gy increment analyses were nominally similar between planning techniques for all cardiac substructures and the lungs.ConclusionsCardiac substructure delineation using E-CTA was feasible, and inclusion in optimization led to modest improvements in sparing of radiosensitive cardiac substructures for some patients.     

Évaluation d’un logiciel pour la délinéation automatique des organes à risques et des volumes cibles ganglionnaires chez des patientes prises en charge pour un cancer du sein

Purpose

Intensity-modulated radiotherapy needs the strict delineation of target volumes as well as organs at risk and the time used for this procedure is long. The purpose of this study was to evaluate the Workflow Box system (Mirada Medical, UK) for automatic delineation and segmentation for everyday use of organs at risk and lymph nodes delineation in patients treated for early stage breast cancer.

A pre-clinical assessment of an atlas-based automatic segmentation tool for the head and neck

Background and purpose

Accurate conformal radiotherapy treatment requires manual delineation of target volumes and organs at risk (OAR) that is both time-consuming and subject to large inter-user variability. One solution is atlas-based automatic segmentation (ABAS) where a priori information is used to delineate various organs of interest. The aim of the present study is to establish the accuracy of one such tool for the head and neck (H&N) using two different evaluation methods.

Materials and methods

Two radiotherapy centres were provided with an ABAS tool that was used to outline the brainstem, parotids and mandible on several patients. The results were compared to manual delineations for the first centre (EM1) and reviewed/edited for the second centre (EM2), both of which were deemed as equally valid gold standards. The contours were compared in terms of their volume, sensitivity and specificity with the results being interpreted using the Dice similarity coefficient and a receiver operator characteristic (ROC) curve.

Results

Automatic segmentation took typically ∼7 min for each patient on a standard PC. The results indicated that the atlas contour volume was generally within ±1SD of each gold standard apart from the parotids for EM1 and brainstem for EM2 that were over- and under-estimated, respectively (within ±2SD). The similarity of the atlas contours with their respective gold standard was satisfactory with an average Dice coefficient for all OAR of 0.68 ± 0.25 for EM1 and 0.82 ± 0.13 for EM2. All data had satisfactory sensitivity and specificity resulting in a favourable position in ROC space.

Conclusions

These tests have shown that the ABAS tool exhibits satisfactory sensitivity and specificity for the OAR investigated. There is, however, a systematic over-segmentation of the parotids (EM1) and under-segmentation of the brainstem (EM2) that require careful review and editing in the majority of cases. Such issues have been discussed with the software manufacturer and a revised version is due for release.     

Cardiac substructures exposure in left-sided breast cancer radiotherapy: Is the mean heart dose a reliable predictor of cardiac toxicity?

PurposeThis study aimed to assess radiation dose distribution to cardiac subvolumes in left-sided breast cancer radiotherapy (LBCRT) and to clarify whether the mean heart dose (MHD) reliably reflects cardiac substructures exposure.Materials and methodsFifty women referred for adjuvant LBCRT were prospectively evaluated. All patients received 3D-conformal hypofractionated radiotherapy (40 Gy delivered in 15 fractions of 2.67 Gy ± boost of 13.35 Gy). Cardiac substructures were contoured using the F. Duane's cardiac atlas. Dose distribution to cardiac chambers, left main (LM), left anterior descending (LAD), left circumflex (LCx) and right coronary artery (RCA)) was assessed. Dosimetric associations were analysed.ResultsThe mean MHD was 3.08 Gy (EQD2 = 3.67 Gy). The mean Dmean/Dmax LAD was 11.45 Gy (EQD2 = 13.64 Gy)/29.5 Gy (EQD2 = 35.15 Gy). Low doses were delivered to LM, LCx, and RCA (Dmean ≤ 1.3 Gy). The left ventricle (LV) was the most exposed cardiac chamber with Dmean/Dmax of 4.78 Gy/37 Gy. The strongest correlation with MHD was found for Dmean LAD (r = 0.81). For every 1 Gy increase in MHD, Dmean LAD rose by 3.4 Gy. However, the proportion of variance in Dmean LAD predictable from MHD was moderate (R² = 0.65). For all other cardiac substructures, R² values were < 0.7.ConclusionOur study showed high exposure of LAD and LV in LBCRT. With poor predictive value, MHD may underestimate doses to cardiac substructures. For optimal heart sparing radiotherapy, we recommend to consider LV and LAD as separate organ at risk.     

自动勾画软件ABAS在鼻咽癌自适应放疗中的应用

目的:评估ABAS自动勾画软件勾画的危及器官准确度和效率,以此来评估它在鼻咽癌患者自适应放疗中的适用程度.方法:随机抽取15例在我院治疗的鼻咽癌患者.CT1为患者的计划CT,CT2为三分之二疗程重薪扫描的CT图像,CT3为患者放疗结束后扫描的CT图像.在ABAS软件中CT1图像设为模板,在CT2和CT3上自动勾画出所需的危及器官,并将自动勾画结果和手工勾画的结果进行对比分析.利用形状相似性指数(Dice similarity coefficient,DSC)和自动勾画时间评价软件自动勾画的精准性和效率性.结果:ABAS软件自动勾画的体积较大的危及器官的DSC指数均大于0.9,在CT1和CT2组中DSC指数的最高为脊髓(0.96±0.01),最低为晶体(0.43±0.19),在CT1和CT3组中DSC指数最高为下颌骨(0.93±0.45),最低为晶体(0.49 ±0.17).同时用ABAS自动勾画危及器官所需平均时间为十分钟左右.结论:在鼻咽癌自适应放疗过程中,自动勾画软件勾画的危器官可以达到很好的准确度同时又明显的节省时间.这样就可以快速评价危及器官受量,使得鼻咽癌自适应放疗成为可能.     

Optimal Target Delineation and Treatment Techniques in the Era of Conformal Photon and Proton Breast and Regional Nodal Irradiation

PurposeRegional nodal irradiation improves disease-free and distant disease–free survival in patients with high-risk breast cancer (BC). Trials demonstrating this used 2- or 3-dimensional conformal radiation therapy (2-dimensional or 3-dimensional [3D] conformal radiotherapy [CRT]) fields based on bony anatomy. Modern volumetric-modulated arc therapy (VMAT) and pencil beam scanning proton therapy (PBSPT) may underdose regional nodes (RNs) not contoured but covered by 3D CRT. Multiple atlases guide modern treatment planning. This study addresses the risk of underdosing when relying on published atlases and treating with 3D CRT, VMAT, and PBSPT.Methods and MaterialsTargets per the Radiation Therapy Oncology Group (RTOG), European Society for Radiotherapy and Oncology (ESTRO), and Radiotherapy Comparative Effectiveness Consortium (RADCOMP) atlases were contoured on a representative patient CT scan. 3D CRT plans based on anatomic borders and VMAT and PBSPT plans for each set of target volumes were generated. Positron emission tomography/computed tomography (PET/CT) scans were reviewed. CT-positive and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG)–avid RNs (n = 389) were mapped from 102 patients with locally advanced (n = 51; median 2; range, 1-8 nodes) and metastatic (n = 51; median 4; range, 1-19 nodes) BC: axillary (AX; n = 284), supraclavicular (SCV; n = 60), and internal mammary nodal (IMN; n = 45). ¹⁸F-FDG-avid RNs falling within the 95% isodose line were considered adequately covered.Results3D CRT plans provided excellent RN coverage. Low AX nodes were covered (≥99%) in all plans. Underdosing of ¹⁸F-FDG–avid RNs falling in the high AX (78%-92%), SCV (52%-75%), and IMN (84%-89%) volumes was observed following the RTOG and ESTRO atlases for VMAT and PBSPT plans. Use of the RADCOMP atlas provided coverage of these areas (89%-100%) with slightly increased heart and lung doses. Atlas guided VMAT/PBSPT plans provided cumulative nodal coverage as follows: ESTRO (89%/88%), RTOG (93%/91%), and RADCOMP (98%/96%).ConclusionsVMAT and PBSPT for regional nodal irradiation in patients with high-risk BC risks underdosage in the high AX, SCV, and IMN nodal regions unless comprehensive target delineation is performed.