中华放射学杂志
中華放射學雜誌
중화방사학잡지
Chinese Journal of Radiology
2009年
7期
753-758
,共6页
肺栓塞%辐射剂量%模型,理论%体层摄影术,X线计算机
肺栓塞%輻射劑量%模型,理論%體層攝影術,X線計算機
폐전새%복사제량%모형,이론%체층섭영술,X선계산궤
Pulmonary embolism%Radiation dosage%Models,theoretical%Tomography,X-ray computed
目的 通过模型实验证实低剂量CT肺动脉成像(CTPA)的可能性并筛选出合理低剂量阈值.方法 测量132例患者气管内、体外空气密度差,制成噪声测量和肺动脉栓塞(PE)模型.设置管电压为120 kVp,管电流分别为280、200、160、100、90、80、70、60、50、40、30、20、15、10 mA,扫描上述两种模型和水模,采用标准算法和软组织算法重建,3名阅片者独立评判图像质量.应用Pearson线性相关分析、配对t检验、方差分析和Kappa检验进行统计学分析.结果 132例患者气管内、体外空气密度差范围在20.00～55.00 HU,与体质量[(64.99±11.86)kg]、体质量/身高[(38.71±6.13)kg/m]及体质量指数(BMI)[(23.11±3.38)ks/m2]呈正相关(r值分别为0.288、0.374、0.449,P值均<0.01).两种模型标准算法[噪声分别为(22.43±11.25)、(21.99±11.67)HU]与软组织算法[(16.55±9.08)、(16.42±9.40)HU]之间噪声差异有统计学意义(F=4.316,P<0.05),软组织算法噪声水平低于标准算法,而与使用何种体模无关.软组织算法100 mA时图像噪声水平与标准算法280 mA时相当,PE模型图像信噪比(SNR)和对比噪声比(CNR)分别为23.05、20.52,不影响对栓塞的识别;软组织算法60 mA时噪声水平与标准算法160 mA时相当,PE模型图像SNR、CNR分别为18.01、15.97,亦不影响栓子定性观察;30 mA以下图像质量明显下降,PE模型图像SNR、CNR分别在12.36、10.95以下,模拟栓子检出能力下降.3名阅片者图像质量判读结果之间一致性高(Kappa值分别0.807、0.712和0.904,P值均<0.01).结论 100 mA可能是比较理想的低剂量CTPA扫描条件;30 mA可能是诊断所需的最低扫描条件;软组织算法成像能减少SNR损失.
目的 通過模型實驗證實低劑量CT肺動脈成像(CTPA)的可能性併篩選齣閤理低劑量閾值.方法 測量132例患者氣管內、體外空氣密度差,製成譟聲測量和肺動脈栓塞(PE)模型.設置管電壓為120 kVp,管電流分彆為280、200、160、100、90、80、70、60、50、40、30、20、15、10 mA,掃描上述兩種模型和水模,採用標準算法和軟組織算法重建,3名閱片者獨立評判圖像質量.應用Pearson線性相關分析、配對t檢驗、方差分析和Kappa檢驗進行統計學分析.結果 132例患者氣管內、體外空氣密度差範圍在20.00～55.00 HU,與體質量[(64.99±11.86)kg]、體質量/身高[(38.71±6.13)kg/m]及體質量指數(BMI)[(23.11±3.38)ks/m2]呈正相關(r值分彆為0.288、0.374、0.449,P值均<0.01).兩種模型標準算法[譟聲分彆為(22.43±11.25)、(21.99±11.67)HU]與軟組織算法[(16.55±9.08)、(16.42±9.40)HU]之間譟聲差異有統計學意義(F=4.316,P<0.05),軟組織算法譟聲水平低于標準算法,而與使用何種體模無關.軟組織算法100 mA時圖像譟聲水平與標準算法280 mA時相噹,PE模型圖像信譟比(SNR)和對比譟聲比(CNR)分彆為23.05、20.52,不影響對栓塞的識彆;軟組織算法60 mA時譟聲水平與標準算法160 mA時相噹,PE模型圖像SNR、CNR分彆為18.01、15.97,亦不影響栓子定性觀察;30 mA以下圖像質量明顯下降,PE模型圖像SNR、CNR分彆在12.36、10.95以下,模擬栓子檢齣能力下降.3名閱片者圖像質量判讀結果之間一緻性高(Kappa值分彆0.807、0.712和0.904,P值均<0.01).結論 100 mA可能是比較理想的低劑量CTPA掃描條件;30 mA可能是診斷所需的最低掃描條件;軟組織算法成像能減少SNR損失.
목적 통과모형실험증실저제량CT폐동맥성상(CTPA)적가능성병사선출합리저제량역치.방법 측량132례환자기관내、체외공기밀도차,제성조성측량화폐동맥전새(PE)모형.설치관전압위120 kVp,관전류분별위280、200、160、100、90、80、70、60、50、40、30、20、15、10 mA,소묘상술량충모형화수모,채용표준산법화연조직산법중건,3명열편자독립평판도상질량.응용Pearson선성상관분석、배대t검험、방차분석화Kappa검험진행통계학분석.결과 132례환자기관내、체외공기밀도차범위재20.00～55.00 HU,여체질량[(64.99±11.86)kg]、체질량/신고[(38.71±6.13)kg/m]급체질량지수(BMI)[(23.11±3.38)ks/m2]정정상관(r치분별위0.288、0.374、0.449,P치균<0.01).량충모형표준산법[조성분별위(22.43±11.25)、(21.99±11.67)HU]여연조직산법[(16.55±9.08)、(16.42±9.40)HU]지간조성차이유통계학의의(F=4.316,P<0.05),연조직산법조성수평저우표준산법,이여사용하충체모무관.연조직산법100 mA시도상조성수평여표준산법280 mA시상당,PE모형도상신조비(SNR)화대비조성비(CNR)분별위23.05、20.52,불영향대전새적식별;연조직산법60 mA시조성수평여표준산법160 mA시상당,PE모형도상SNR、CNR분별위18.01、15.97,역불영향전자정성관찰;30 mA이하도상질량명현하강,PE모형도상SNR、CNR분별재12.36、10.95이하,모의전자검출능력하강.3명열편자도상질량판독결과지간일치성고(Kappa치분별0.807、0.712화0.904,P치균<0.01).결론 100 mA가능시비교이상적저제량CTPA소묘조건;30 mA가능시진단소수적최저소묘조건;연조직산법성상능감소SNR손실.
Objective To investigate the feasibility of reduced radiation dose for CT pulmonary angiography (CTPA) and the possible lowest radiation threshold by a phantom study.Methods The CT value difference between air within the trachea and the extracorporeal background region was measured in132 consecutive patients.A noise-measurement phantom and a pulmonary embolism (PE) phantom were made of phenol-formaldehyde, and both phantoms and a water phantom were scanned with standard and lower radiation doses as follow: 280, 200, 160, 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, and 10 mA respectively, at a fixed voltage of 120 kVp.Standard and soft tissue algorithms were used to reconstruct the images.Three experienced doctors independendy evaluate the image quality and the efficiency of detecting PE of the images with various doses.The Pearson correlation analysis, two-tailed paired t test, ANOVA, and Kappa test were employed for the statistical analysis.Results The CT value difference between air within the trachea and the extracorpereal background region in 132 consecutive patients ranged from 20.00 to 55.00 HU, which had a positive correlation with weight[(64.99±11.86) kg], weight-height ratio [(38.71±6.13) kg/m], and BMI[(23.11±3.38) kg/m2](r=0.228,0.374,0.449 respectively; P <0.01).The image noise level with soft-tissue reconstruction algorithm[(16.55±9.08), (16.42±9.40) HU]was significantly lower than that of the image with standard reconstruction algorithm[(22.43±11.25),(21.99±11.67) HU](F=4.316, P < 0.05).The image noise level with soft-tissue reconstruction algorithm at 100 mA was similar to that of the images with standard reconstruction algorithm at 280 mA, and the signal-w-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the image of PE phantom was 23.05 and 20.52 respectively, without any impairment in detectability of embolus.The image noise level with soft-tissue reconstruction algorithm at 60 mA was similar to that of the image with standard reconstruction algorithm at 160 mA, while the SNR and CNR was 18.01 and 15.97 respectively, also with acceptable detectability of embolus.When the tube current was reduced below 30 mA, the image quality decreased significantly, with the SNR and CNR was lower than 12.36 and 10.95 respectively, and the detectability of embolus was degraded.The consistency of the image quality grading by 3 observers was excellent(K=0.807,0.712,0.904 ,respectively; P < 0.01).Conclusions The 100 mA may potentially be the ideal low dose tube current setting, with radiation dose only equal to 36% of 280 mA (standard dose).The 30 mA may possibly be a minimum radiation dose for detecting PE.The soft-tiasue reconstruction algorithm was favorable in preserving the SNR when the radiation dose was reduced.
