目的探讨静脉法三维数字减影血管成像(intravenous three-dimensional digital subtraction angiography,IV3D DSA)在脑血管中运用的临床可行性,并与容积CT数字减影血管成像(VCTDSA)对照评价其图像质量。方法对21例行VCTDSA的动脉瘤开...目的探讨静脉法三维数字减影血管成像(intravenous three-dimensional digital subtraction angiography,IV3D DSA)在脑血管中运用的临床可行性,并与容积CT数字减影血管成像(VCTDSA)对照评价其图像质量。方法对21例行VCTDSA的动脉瘤开颅夹闭术后患者同期行IV 3D DSA脑血管成像检查。对比剂从肘前静脉入路,行头部3D DSA,将原始数据传至工作站进行后处理。结果 IV 3D DSA检查中,2例失败,19例成功,20个动脉瘤夹均显示较清晰(其中1例有2个动脉瘤夹),12例清晰显示动脉瘤夹闭完全,载瘤动脉通畅,7例因运动伪影干扰使载瘤动脉显示欠佳,大部分能较好地显示颅内主要大动脉,其中,图像质量Ⅱ级占10.5%(2/19),Ⅲ级占84.2%(16/19),Ⅳ级占5.3%(1/19);对应VCTDSA中,19例动脉瘤夹及载瘤动脉均清晰显示,图像质量Ⅰ级占36.8%(7/19),Ⅱ级占42.1%(8/19),Ⅲ级占21.1%(4/19)。IV 3D DSA与VCTDSA的图像质量差异有统计学意义(Z=-3.782,P<0.05)。结论 IV 3D DSA临床可行,但图像质量不及VCTDSA。IV 3D DSA尚需优化成像参数提高图像质量。展开更多
In this paper,a genetic algorithm (GA) is investigated to deal with cell-by-cell dynamic spectrumallocation (DSA) in the heterogeneous scenario with temporal and spatial traffic demand changes,whichis also known as a ...In this paper,a genetic algorithm (GA) is investigated to deal with cell-by-cell dynamic spectrumallocation (DSA) in the heterogeneous scenario with temporal and spatial traffic demand changes,whichis also known as a difficult combinatorial optimization problem.A new two-dimensional chromosome encodingscheme is defined according to characteristics of the heterogeneous scenario,which prevents forminginvalid solutions during the genetic operation and enables much faster convergence.A novel randomcoloring gene generation function is presented which is the basic operation for initialization and mutationin the genetic algorithm.Simulative comparison demonstrates that the proposed GA-based cell-by-cellDSA outperforms the conventional contiguous DSA scheme both in terms of spectral efficiency gain andquality of service (QoS) satisfaction.展开更多
文摘目的探讨静脉法三维数字减影血管成像(intravenous three-dimensional digital subtraction angiography,IV3D DSA)在脑血管中运用的临床可行性,并与容积CT数字减影血管成像(VCTDSA)对照评价其图像质量。方法对21例行VCTDSA的动脉瘤开颅夹闭术后患者同期行IV 3D DSA脑血管成像检查。对比剂从肘前静脉入路,行头部3D DSA,将原始数据传至工作站进行后处理。结果 IV 3D DSA检查中,2例失败,19例成功,20个动脉瘤夹均显示较清晰(其中1例有2个动脉瘤夹),12例清晰显示动脉瘤夹闭完全,载瘤动脉通畅,7例因运动伪影干扰使载瘤动脉显示欠佳,大部分能较好地显示颅内主要大动脉,其中,图像质量Ⅱ级占10.5%(2/19),Ⅲ级占84.2%(16/19),Ⅳ级占5.3%(1/19);对应VCTDSA中,19例动脉瘤夹及载瘤动脉均清晰显示,图像质量Ⅰ级占36.8%(7/19),Ⅱ级占42.1%(8/19),Ⅲ级占21.1%(4/19)。IV 3D DSA与VCTDSA的图像质量差异有统计学意义(Z=-3.782,P<0.05)。结论 IV 3D DSA临床可行,但图像质量不及VCTDSA。IV 3D DSA尚需优化成像参数提高图像质量。
基金Supported by the National Basic Research Program of China (No. 2007CB310606)
文摘In this paper,a genetic algorithm (GA) is investigated to deal with cell-by-cell dynamic spectrumallocation (DSA) in the heterogeneous scenario with temporal and spatial traffic demand changes,whichis also known as a difficult combinatorial optimization problem.A new two-dimensional chromosome encodingscheme is defined according to characteristics of the heterogeneous scenario,which prevents forminginvalid solutions during the genetic operation and enables much faster convergence.A novel randomcoloring gene generation function is presented which is the basic operation for initialization and mutationin the genetic algorithm.Simulative comparison demonstrates that the proposed GA-based cell-by-cellDSA outperforms the conventional contiguous DSA scheme both in terms of spectral efficiency gain andquality of service (QoS) satisfaction.