Automatic segmentation of thoracic CT images using three deep learning models

PurposeDeep learning (DL) techniques are widely used in medical imaging and in particular for segmentation. Indeed, manual segmentation of organs at risk (OARs) is time-consuming and suffers from inter- and intra-observer segmentation variability. Image segmentation using DL has given very promising results. In this work, we present and compare the results of segmentation of OARs and a clinical target volume (CTV) in thoracic CT images using three DL models.Materials and methodsWe used CT images of 52 patients with breast cancer from a public dataset. Automatic segmentation of the lungs, the heart and a CTV was performed using three models based on the U-Net architecture. Three metrics were used to quantify and compare the segmentation results obtained with these models: the Dice similarity coefficient (DSC), the Jaccard coefficient (J) and the Hausdorff distance (HD).ResultsThe obtained values of DSC, J and HD were presented for each segmented organ and for the three models. Examples of automatic segmentation were presented and compared to the corresponding ground truth delineations. Our values were also compared to recent results obtained by other authors.ConclusionThe performance of three DL models was evaluated for the delineation of the lungs, the heart and a CTV. This study showed clearly that these 2D models based on the U-Net architecture can be used to delineate organs in CT images with a good performance compared to other models. Generally, the three models present similar performances. Using a dataset with more CT images, the three models should give better results.     

Quantification of myocardial fibrosis using noninvasive T2-mapping magnetic resonance imaging: Preclinical models of aging and pressure overload

Noninvasive imaging of cardiac fibrosis is important for early diagnosis and intervention in chronic heart diseases. Here, we investigated whether noninvasive, contrast agent-free MRI T₂-mapping can quantify myocardial fibrosis in preclinical models of aging and pressure overload. Myocardial fibrosis and remodeling were analyzed in two animal models: (i) aging (15-month-old male CF-1 mice vs. young 6- to 8-week-old mice), and (ii) pressure overload (PO; by transverse aortic constriction in 4- to 5-month-old male C57BL/6 mice vs. sham-operated for 14 days). In vivo T₂-mapping was performed by acquiring data during the isovolumic and early diastolic phases, with a modified respiratory and ECG-triggered multiecho TurboRARE sequence on a 7-T MRI. Cine MRI provided cardiac morphology and function. A quantitative segmentation method was developed to analyze the in vivo T₂-maps of hearts at midventricle, apex, and basal regions. The cardiac fibrosis area was analyzed ex vivo by picro sirius red (PSR) staining. Both aged and pressure-overloaded hearts developed significant myocardial contractile dysfunction, cardiac hypertrophy, and interstitial fibrosis. The aged mice had two phenotypes, fibrotic and mild-fibrotic. Notably, the aged fibrotic subgroup and the PO mice showed a marked decrease in T₂ relaxation times (25.3 ± 0.6 in aged vs. 29.9 ± 0.7 ms in young mice, p = 0.002; and 24.3 ± 1.7 in PO vs. 28.7 ± 0.7 ms in shams, p = 0.05). However, no significant difference in T₂ was detected between the aged mild-fibrotic subgroup and the young mice. Accordingly, an inverse correlation between myocardial fibrosis percentage (FP) and T₂ relaxation time was derived (R² = 0.98): T₂ (ms) = 30.45 – 1.05 × FP. Thus, these results demonstrate a statistical agreement between T₂-map–quantified fibrosis and PSR staining in two different clinically relevant animal models. In conclusion, T₂-mapping MRI is a promising noninvasive contrast agent-free quantitative technique to characterize myocardial fibrosis.     

眼表铁过载小鼠干眼模型的构建和机制研究

目的：通过给小鼠腹腔注射右旋糖酐铁，建立小鼠铁过载干眼模型并初步探索其可能的机制。

方法：将40只雄性C57BL/6小鼠(取右眼为实验眼)用随机数字表法将小鼠分为4组：对照组10只，每次腹腔注射生理盐水0.2mL； 低剂量组、中剂量组、高剂量组各10只为模型组，每次分别腹腔注射浓度为12.5、25、50mg/mL的右旋糖酐铁溶液0.2mL。每3d注射1次，共注射28d。注药后第7、14、28d观察各组小鼠眼表炎症指数、角膜荧光素染色、泪膜破裂时间(BUT)及泪液分泌量(SⅠt)，评估干眼及眼表炎症程度。28d后处死小鼠，取角膜、结膜及泪腺组织，进行HE染色、普鲁士蓝染色以及组织铁检测，评估小鼠炎症反应及铁过载情况； 采用酶联免疫吸附试验(ELISA)检测炎症因子白细胞介素-1β(IL-1β)、肿瘤坏死因子-α(TNF-α)、基质金属蛋白酶-9(MMP-9)的表达情况。

结果：与对照组相比，模型组小鼠出现一系列干眼症状，小鼠眼表炎症指数增高，角膜荧光素染色评分增加，BUT缩短，泪液分泌量减少(均P<0.05)； 模型组小鼠角膜、结膜及泪腺组织均受到不同程度的损伤，各组织眼表铁沉积情况较对照组加重，组织铁含量明显增加(均P<0.01)； 模型组小鼠角膜、结膜及泪腺组织中炎症因子(IL-1β、TNF-α、MMP-9)的含量均高于对照组(均P<0.01)，随着右旋糖酐铁注药时间及浓度增加，小鼠干眼及眼表炎症程度逐渐加重。

结论：腹腔注射右旋糖酐铁可成功建立小鼠铁过载干眼模型，其机制可能与铁过载加重眼表炎症反应有关。     

Altitude exposure as a training & iron overload management strategy post leukemia

ObjectivesTo examine iron stores, hemoglobin mass, and performance before, during and after intermittent altitude exposure in a professional male rugby player experiencing iron overload following blood transfusions for treatment for acute myeloid leukemia.DesignLongitudinal, repeated measures, single case-study.MethodsThe player was followed prior to (control), and during (study), an in-season block of altitude training. During the control period two venesections were performed for a total of 750 mL of blood removal. Internal and external training load, match statistics, blood volume, plasma volume, haemoglobin mass, serum ferritin and reticulocyte count were monitored throughout.ResultsDuring the control period serum ferritin declined following the two venesections (∼51%) as did haemoglobin mass (∼2%), reticulocyte count remained stable. During the study period serum ferritin further declined (∼30%), however haemoglobin mass and reticulocyte count increased (∼4% and ∼14% respectively). Internal training load for the control and study period was similar, however external training load was lower in the study period. Match statistics were not favourable for the player during the control period, however they improved during the study period.ConclusionsThis case supports the theory that individuals with elevated iron availability are well placed to achieve increases in haemoglobin mass. Furthermore, although therapeutic venesections may still be required to manage iron overload, the addition of altitude exposure may be a method to assist in reducing total body iron by means of mobilising available (excessive) iron to incorporate into haemoglobin. Altitude exposure did not hinder the players’ performance. Further research is encouraged.     

Comparative analysis of calcification parameters with Agatston Score approximations for ex vivo atherosclerotic lesions

BackgroundThe Agatston Calcium Score is a predictor of major adverse cardiovascular events but it is unable to identify high-risk lesions. Recent research suggests that examining calcification phenotype could be more indicative of plaque stability.ObjectiveTo examine the Agatston score's ability to determine atherosclerotic calcification phenotype.MethodsMicro-Computed Tomography was performed on 20 carotid and 20 peripheral lower limb lesions. ImageJ pixel histogram analysis quantified the non-calcified (≥30HU, <130HU) and calcified (≥130HU) tissue volumes. ImageJ ‘3D Objects Counter’ plugin determined the calcified particle count, volumes and maximum attenuation density of each particle. Image stacks were subsequently downsampled to a resolution of 0.7 × 0.7 × 3 mm and an approximation for the Extra-Coronary Calcium Scores (ECCS) were calculated. Spearman's correlation examined the relationships between ECCS approximations and calcification parameters.ResultsECCS has a strong positive correlation with the Calcified Volume Fraction (CVF) (r_s = 0.865, p < 0.0005), weak positive correlations with Calcified Particle Fraction (CPF) (r_s = 0.422, p = 0.007) and Microcalcification Fraction (micro-CF) (r_s = 0.361, p = 0.022). There is no correlation evident between ECCS and Calcified Particle Index (CPI) (r_s = −0.162, p = 0.318). It is apparent that there is a high prevalence of microcalcifications in both carotid and peripheral lower limb lesions. Additionally, an inverse relationship exists between calcified particle volume and maximum-recorded attenuation density.ConclusionThe density-weighted Agatston calcium scoring methodology needs to be reviewed. Calcium scoring which differentiates between critical calcification morphologies, rather than presenting a density-weighted score, is required to direct high-risk plaques towards tailored treatment.     

肺泡蛋白沉积症低剂量容积数据高分辨率CT影像特征分析

背景　目前肺泡蛋白沉积症（PAP）的确诊需要依据支气管肺泡灌洗和/或肺活检，属于侵入性检查，而胸部CT检查对本病的诊断具有重要提示作用，尤其是胸部低剂量容积数据高分辨率CT（VHRCT）检查能更多地显示双肺解剖细节及病变细微特点，从而为临床诊断提供帮助，但鲜有这方面的报道。目的　观察低剂量VHRCT下PAP治疗前后的影像学表现，从而探讨VHRCT在PAP诊断中的临床价值。方法　回顾性分析2015年6月-2018年6月在四川大学华西第四医院诊治的24例PAP患者的临床资料和胸部低剂量VHRCT资料、确诊情况及治疗效果。结果　治疗前，24例患者双肺均可见多发的磨玻璃样密度影，边界清，边缘模糊，其中12例磨玻璃影广泛分布，呈“地图征”表现，7例患者双肺可见局限性片状实变影；6例磨玻璃影中可见小叶间隔增厚，呈“铺路石征”表现；3例可见从肺门向外放射，呈“蝶翼状”分布的大面积阴影（磨玻璃影或/和实变影）；2例可见充气支气管征；部分患者双肺可见多发微小结节及间质纤维化表现；24例均未见纵隔及肺门淋巴结增大；同一患者中可有上述几种征象同时出现。治疗后复查及随访过程中，24例双肺磨玻璃影范围不同程度缩小、密度减低、边缘清晰，4例实变影密度减低呈磨玻璃密度影，2例见充气支气管征。16例经支气管肺泡灌洗确诊，3例经血清粒细胞-巨噬细胞集落刺激因子（GM-CSF）抗体检测确诊，5例经支气管镜肺穿刺活检确诊。确诊前根据患者胸部低剂量VHRCT的特征性表现高度提示PAP者共16例，符合率为66.7%（16/24），其余8例患者依据VHRCT的特征，5例提示细菌性肺炎、2例提示肺水肿、1例提示特发性肺间质纤维化。治疗后患者，呼吸困难、咳嗽等临床症状明显好转。治疗后总肺活量占预计值百分比（TLC%）、一氧化碳弥散量占预计值百分比（DLCO%）、肺活量占预计值百分比（VC%）、酸碱度（pH）、氧分压（PaO2）高于治疗前，治疗后二氧化碳分压（PaCO2）低于治疗前（P<0.05）。结论　PAP的低剂量VHRCT表现为广泛性或局限性分布的磨玻璃影和/或实变影，其中“地图征”和“铺路石征”具有一定的特征性，部分病例可见“蝶翼征”和充气支气管征；另外，本疾病一般无纵隔及肺门淋巴结增大；上述影像学征象有助于PAP的诊断、严重程度评价和疗效观察，可作为一种常规检查，推广应用。     

体视学法在颅内血肿体积测量的应用

目的介绍改进后的体视学法测量颅内血肿体积,并验证其准确性。方法在92例颅内出血的CT图像上,同时运用体视法、CT定量法测量颅内血肿体积,以CT定量法的结果为标准验证体视法的准确性。结果按血肿体积大小分为5组,各组CT定量法、体视学法所测得体积采用配对样本的t检验分析P值皆大于0.05,即CT定量法、体视学法所测血肿体积无统计学差异。结论体视学法测量颅内血肿准确可靠,在CT工作站对颅内血肿病例行胶片打印排版时,在图像上加上合适的网格,可方便临床医生快速运用体视法准确测量颅内血肿体积。