64层CT手动和自动管电流调节技术在骨盆创伤中的对照研究

目的:探讨64层CT手动管电流调节技术在骨盆外伤中应用的可行性及其应用价值.方法:对87例骨盆外伤患者采用64层CT进行手动和自动管电流调节技术两种方法扫描,由2名具有资质的影像医师采用双盲法分别对两种扫描方法所获取图像的图像质量、骨折显示情况及辐射剂量进行评价,详细记录所有数据并进行统计学分析.结果:①手动管电流调节技术对骨折线、盆部软组织、VR图像质量和MPR图像质量评分分别为4.00±0.00,2.72±0.44,4.00±0.00,4.00±0.00;自动管电流调节技术对骨折线、软组织、VR和MPR评分分别为4.00±0.00,3.72±0.44,4.00±0.00,4.00±0.00;两种扫描方法对软组织评分有统计学差异(t =9.06,P=0.00);②手动与自动管电流调节技术剂量加权指数CTDIVOL分别为9.05±1.59.15.50±2.74;手动较自动管电流调节技术降低约41.61％,具有统计学差异(t=17.91,P=0.00).结论:在骨盆外伤患者中,64层CT手动管电流调节技术能确保图像质量满足诊断需求,并能有效降低患者的辐射剂量.     

管电压对CT值测量、辐射剂量及图像质量影响的模型研究

目的 探讨降低管电流和管电压对CT值的影响,及其辐射剂量降低对图像质量的影响程度.方法 配置不同浓度对比剂样本共113个,在15种不同扫描条件下进行CT扫描.测量和记录CT值及标准差,分析改变管电流和管电压对CT值测量的影响,并计算对应关系.记录CT容积剂量指数(CTDIvol),计算15种扫描条件下的辐射剂量.不同管电压和管电流下CT值差异比较采用方差分析和Kruskal-Wallis秩和检验,不同管电压下CT值对应关系及管电压和管电流对辐射剂量和图像质量的影响程度分析采用相关性分析.结果 管电压固定时不同管电流间(250、200、150、100和50 mA)的CT值差异均无统计学意义(F值分别为0.001、0.008、0.075,P均＞0.05).管电流固定时,不同管电压间(120、100和80 kV)的CT值差异均具有统计学意义(H值分别为17.906、17.906、13.527、20.124、23.563,P均＜0.05).计算不同管电压下同一样本CT值的对应关系:CT值100 kV=1.561×CT值120kV+4.0818,CT值80kV=1.2131 ×CT值120 kV+0.9283.分析不同管电压下辐射剂量对图像噪声的影响程度,并确立相关性方程:N120kv=-5.9771Ln(D120kV)+25.412,N100kv=-10.544Ln(D100 kV)+36.262,N80 kv=-25.326Ln(D80 kv)+62.816.计算噪声值关键点,证明根据所需图像噪声值(11.2和13.9),可以指导扫描条件,在一定条件下应用低管电压,高管电流可以降低辐射剂量.结论 管电压对CT值测量有影响,根据所需图像噪声值调整扫描条件,在一定条件下应用低管电压,高管电流可以降低辐射剂量.改变管电压后造成的CT值变化,可依据不同管电压下CT值对应关系进行校准.     

铋屏蔽联合器官管电流调制技术在颅脑CT检查中应用的体模研究

目的:通过测量敏感器官的辐射剂量,评价铋屏蔽联合器官-管电流调制(X-care)技术在颅脑CT扫描中的应用价值。方法:使用德国德国西门子公司炫速双源CT对头颈体模进行相同容积CT剂量指数(CTDI vol)下的X-care、铋屏蔽和X-care联合铋屏蔽3种方式扫描颅脑,及无铋屏蔽和铋屏蔽2种方式扫描双能量...     

自动管电流技术联合人工智能在COVID-19肺部低剂量CT中的应用价值

【摘要】目的：探讨新型冠状病毒肺炎(COVID-19)肺部CT应用低剂量自动管电流调制技术（CareDose）联合人工智能（AI）辅助诊断系统有效降低辐射剂量的可行性。方法：选取216例COVID-19住院患者,按3种扫描剂量模式随机分配,即常规剂量Caredose模式（管电流80～150mAs,管电压120kV）、低剂量CareDose模式（管电流21～60mAs,管电压100kV）和人工固定低管电流模式（管电流20mAs,管电压100kV）,每组72例,AI独立阅片后由两位放射专家评判识别符合率。结果：低剂量CareDose模式组的图像主观评分和诊断符合率接近常规剂量CareDose组,明显优于人工固定低管电流组;低剂量CareDose模式组和人工固定低管电流模式组的CT剂量指数（CTDIvol）、剂量长度乘积（DLP）和有效辐射剂量（ED）均显著低于常规CareDose模式组（ED分别降低66.75%、82.39%）。结论：低剂量自动管电流调制技术联合AI辅助诊断系统应用于COVID-19肺部CT,在不影响诊断筛查的前提下能显著降低辐射剂量。     

偏离等中心点对CT自动管电流调制技术图像质量及辐射剂量的影响

目的探讨偏离扫描野等中心点对CT自动管电流调制(ATCM)技术图像质量及辐射剂量的影响。资料与方法使用16层螺旋CT固定管电流和ATCM技术扫描等中心点及不同偏心位置的质量保证水模。其他采集参数保持一致。记录不同扫描位置定位像的大小和CT值,以及图像的mA和噪声。结果随着水模偏离球管的距离增加,定位像越小,但CT值无改变。固定管电流扫描,随着偏离等中心点距离的增加,图像噪声越明显。ATCM技术扫描,等中心点以上100mm到等中心点以下70mm,管电流是等中心点的168%到78%,图像噪声从91%增加到122%。结论应用ATCM技术扫描,偏离扫描野等中心点将显著增加图像噪声或辐射剂量。     

自动管电流调节联合低电压低剂量扫描技术在幼儿胸部CT扫描中的优化应用研究

目的 探讨64层CT自动管电流调节技术(ATCM)结合低电压在幼儿胸部低剂量扫描中的应用价值.方法 搜集行64层CT ATCM胸部扫描的幼儿(≤2岁)48例,其中A组(管电压100 kV)30例,B组(管电压80kV) 18例;并与既往采用固定管电流条件下的低剂量扫描数据进行对比分析,对照组C组(100 kV/60 mAs)30例;其余扫描参数一致.记录每次扫描的平均管电流(mAs)、CT容积剂量指数(CTDIvol)、剂量长度值(DLP),计算出有效剂量(ED)及剂量减低比值(DR),并比较3组的剂量及图像质量.结果 A组CTDIvol为(1.11±0.19)mGy,B组CTDIvol为(0.99 ±0.11)mGy,C组CTDIvol为(2.38±0.00) mGy;3组数据两两比较差异均有统计学意义(P＜0.05).A组相对C组DR约51.07％,B组相对C组DR降低约58.20％.3组图像质量均满足诊断要求,差异无统计学意义(P=0.50).结论 低电压联合ATCM技术在幼儿胸部扫描中可以广泛应用,能够有效降低辐射剂量且不影响图像质量.     

Z轴自动管电流调制技术在头颈部CT扫描血管成像中对甲状腺剂量的降低

目的 评价在进行头颈部CT扫描血管成像时,Z轴自动管电流调制技术(ATCM)对减少甲状腺的辐射剂量的作用及对图像噪声的影响。方法 回顾性地分析140例头颈部CT增强血管成像的病例,其中用固定管电流技术和 Z 轴自动管电流调节技术各70例,观察其成像质量,记录其客观噪声水平(由CT图像衰减值的标准差进行评估),并比较其单次扫描的加权CT剂量指数CTDI_w,管电流mA及剂量长度乘积DLP。结果 在扫描范围、扫描参数(管电压、螺距、准直器厚度等)、造影剂注射速率和注射部位完全相同的情况下,固定管电流技术和 Z 轴自动管电流调节技术的图像质量相同,甲状腺图像噪声分别为10.14和13.64 HU。单次扫描的加权CT剂量指数CTDI_w(mGy)分别为(43.22±1.42)和(35.99±1.31) mGy。剂量长度乘积分别为(1514.45±5.56)和(1121.39±5.51)mGy·cm, 剂量长度乘积降低约25.95%。结论 Z 轴自动管电流调节技术能有效降低总曝光量和累计剂量长度乘积,可以有效地降低患者的辐射剂量,特别是像甲状腺和眼晶体等射线敏感组织器官的辐射剂量降低,减少其辐射危害,但是图像噪声略有增加。     

胸部低剂量CT扫描管电流与噪声分布相关性研究

目的 分析胸部低剂量CT图像噪声分布特点,优化低剂量扫描参数.方法 利用图像空间添加噪声软件对中国人仿真胸部体模CT图像进行6种不同噪声指数的模拟,并分析预设噪声指数与模拟图像噪声值的差异.使用该软件对20例志愿者常规扫描图像进行噪声添加,模拟出10、30、50、80、100、120、150、180及240 mA 9组胸部低剂量图像,记录每幅图像模拟噪声值,并对不同剂量组模拟噪声值进行统计学分析.结果 图像噪声添加法计算的模拟噪声值与预设噪声指数差异不大.胸部低剂量扫描时,图像模拟噪声值随着管电流的降低而增加,当管电流在30～50 mA时,噪声降低显著(F=24.09 ～ 40.79,P＜0.05);80～240 mA时,噪声值降低幅度变缓;80mA组与120 mA组之间差异不大.结论 图像空间添加噪声软件可应用于胸部低剂量CT图像噪声的评价研究.胸部低剂量CT检查采用管电流80 mA,能够保证图像噪声较小,同时明显降低辐射剂量.     

低管电流联合 SAFIRE 重建在颈部肿大淋巴结的双能量 CT 扫描中的应用

目的：探讨低管电流联合 SAFIRE 重建的双能量 CT 扫描在颈部肿大淋巴结诊断中的应用。方法经病理证实的50例颈部肿大淋巴结的患者,进行常规 CT 平扫及双能量动脉期扫描,将其随机分为2组,即实验组和对照组,每组25例。实验组管电压分别为100 kV 和 Sn140 kV,管电流分别为117 mAs 和109 mAs,图像重建采用 SAFIRE 迭代重建技术,值选3;对照组管电压分别为100 kV 和 Sn140 kV,管电流分别为189 mAs 和165 mAs,1.0 cm,图像重建算法采用滤波反投影(FBP)技术,其余参数均相同。由2名有经验的医师对2组图像质量进行双盲法评分,利用 Kappa 检验比较观察者间评分的一致性;采用独立样本 t 检验比较2组患者的图像质量及有效辐射剂量。结果2组患者平均 CT 值的比较无统计学差异(P >0.05);2组噪声及信噪比(SNR)的比较有统计学差异(t 分别为4.705、4.403,P 分别为0.0008、0.0007);2组对比噪声比(CNR)无统计学差异(P >0.05);2组图像主观评分一致性较好(Kappa=0.720)且无统计学差异(P >0.05);实验组容积 CT 剂量指数(CTDIvol)为(10.801±0.594)mGy,剂量长度乘积(DLP)为(270.317±5.439)mGy·cm,有效辐射剂量(ED)为(1.594±0.031)mSv,对照组 CTDIvol 为(18.870±0.356)mGy, DLP 为(464.560±1.577)mGy·cm,ED 为(2.741±0.009)mSv,实验组 ED 较对照组降低约41.8%,且2组差异均有统计学意义(P <0.05)。结论在颈部肿大淋巴结的双能量扫描中,低管电流联合 SAFIRE 迭代重建能够在保证图像质量的同时,降低受检者所接受的辐射剂量。     

自动管电流调节技术对下肢血管CTA图像质量和辐射剂量的影响

目的 :探讨64排螺旋CT采用固定管电流和固定噪声指数(NI)的Z轴自动管电流调节(ATCM)技术对下肢血管CTA图像质量及辐射剂量的影响。方法:将60例行下肢血管CTA检查的患者随机分为A组(固定管电流250 m A)、B组(ATCM技术,50~380 m A,NI 12)各30例。其余扫描参数均一致。检查结束后分别对2组相同横断层面图像的股主动脉、腘动脉和胫后动脉图像噪声(SD)进行测量,并对重组后的三维图像进行质量评分,同时记录机器自动生成的CT剂量指数(CTDIvol)、相应剂量长度乘积(DLP),对比2组数据之间差异。结果:2组的血管图像噪声和图像质量评分差异均无统计学意义(均P0.05),重组后的三维图像均能完整显示下肢动脉及其各级主要分支,满足诊断需要。B组的辐射剂量与A组比较,CTDIvol降低了51.72%(P=0.000,P0.05)、DLP降低了47.87%(P=0.000,P0.05)、有效辐射剂量(ED)下降了43.90%。结论 :下肢血管CTA采用ATCM技术,在保证图像质量的同时可降低患者的辐射剂量。     

Dose reduction in multidetector CT using attenuation-based online tube current modulation

OBJECTIVE: This study was designed to quantify the radiation dose saved by attenuation-based online tube current modulation applied to multidetector CT (MDCT) of the adult trunk as a function of effective milliampere-second (mAs) presets, sex, and body habitus. SUBJECTS AND METHODS. One hundred twenty patients underwent MDCT of the trunk (60 thoracic, 60 abdominal) with an attenuation-based online tube current modulation. Consecutive acquisitions at standard and two lower effective mAs presets were obtained in each patient. Mean percentage effective mAs reductions were compared for each effective mAs preset, taking into account sex and body mass index. RESULTS: Mean effective mAs reduction was 16.9% and 20.0% for the chest and the abdomen, respectively. Mean percentage effective mAs reductions were found to be significantly different for sex (chest, p = 0.003; abdomen, p = 0.002) but not significantly different for the different effective mAs presets or body mass index. CONCLUSION: Attenuation-based online tube current modulation used with MDCT should be considered as a secondary tool of radiation dose reduction because it saves as much as 20% of the radiation dose on the adult trunk, regardless of initial mAs preset. However, initial decreases of mAs presets by the physician should be considered the primary tool for radiation dose reduction.     

行肝脏对比增强CT时根据密度自动调整管电压和管电流调制以减少辐射剂量

目的回顾性分析联合应用自动调整管电压和自动管电流调制技术,与单独使用自动管电流调制比较,是否可在可接受的影像质量情况下降低肝脏对比增强CT的辐射剂量。材料与方法本研究经单位伦理委员会批准,无需知情同意书。怀疑肝脏疾病的314例病人,分成3组。其中2组应用自动调整管电压和自动管电流调制技术(A1组,n=97;A2组,n=101),但两组之间采用不同的对比增益设定;第3组,在固定管电压120kV条件下采用自动管电流调制技术(B组,n=116)。评价容积加权CT剂量指数与辐射距离乘积、对比噪声比和平均影像噪声。影像分析由2名具职业执照的放射科医师和1名放射科住院医师完成。统计分析采用单因素方差分析、双尾配对t检验、秩和检验和非劣效性检验。结果 A1和A2组较B组辐射剂量明显降低(P<0.0001)。A1组的辐射剂量平均降低20%,A2组降低31%。此外,A1和A2组的对比噪声比明显高于B组(P<0.0001)。尽管A1和A2组的影像噪声较高,但影像质量总体还是可以接受的。结论与单独采用自动管电流调制技术相比,联合应用自动调整管电压和自动管电流调制技术可在保证影像质量情况下,降低肝脏对比增强CT的检查辐射剂量。     

Noise-based tube current reduction method with iterative reconstruction for reduction of radiation exposure in coronary CT angiography

Purpose

To investigate the potential of noise-based tube current reduction method with iterative reconstruction to reduce radiation exposure while achieving consistent image quality in coronary CT angiography (CCTA).

Materials and methods

294 patients underwent CCTA on a 64-detector row CT equipped with iterative reconstruction. 102 patients with fixed tube current were assigned to Group 1, which was used to establish noise-based tube current modulation formulas, where tube current was modulated by the noise of test bolus image. 192 patients with noise-based tube current were randomly assigned to Group 2 and Group 3. Filtered back projection was applied for Group 2 and iterative reconstruction for Group 3. Qualitative image quality was assessed with a 5 point score. Image noise, signal intensity, volume CT dose index, and dose-length product were measured.

Results

The noise-based tube current modulation formulas were established through regression analysis using image noise measurements in Group 1. Image noise was precisely maintained at the target value of 35.00 HU with small interquartile ranges for Group 2 (34.17–35.08 HU) and Group 3 (34.34–35.03 HU), while it was from 28.41 to 36.49 HU for Group 1. All images in the three groups were acceptable for diagnosis. A relative 14% and 41% reduction in effective dose for Group 2 and Group 3 were observed compared with Group 1.

Conclusion

Adequate image quality could be maintained at a desired and consistent noise level with overall 14% dose reduction using noise-based tube current reduction method. The use of iterative reconstruction further achieved approximately 40% reduction in effective dose.     

Effect of reduction in tube current on reader confidence in paediatric computed tomography

BACKGROUND: Computed tomography (CT) contributes significantly to the total radiation dose derived from medical imaging in children. As the number of CT examinations increases there is renewed interest in possible ways to minimize such radiation. AIM: To study the effect of decremental reduction in tube current settings on structural resolution and on reader confidence in being able to reach a final diagnosis. MATERIALS AND METHODS: The study involved spiral CT of children aged 0-13 years. CT performed at reduced mA settings (60-75, 76-90 and 91-130 mA for thoracic, abdominal and pelvic examinations, and 76-90 and 91-130 mA for cranial examinations) were compared with similar investigations at conventional settings (180-240 mA). Images were scored by two blinded readers for structural resolution and diagnostic confidence. Structural resolution was scored on a binary (adequate or not) scale for six structures each in cranial, thoracic and pelvic examinations and for eight structures in abdominal studies, and reader confidence was scored on a four-point scale as 25-100%. Scores from the two readers were averaged for comparison in subgroup analyses. RESULTS: Reduction of tube current settings to 75-90 mA for thoracic, abdominal and pelvic examinations and to 90-130 mA for cranial examinations was not associated with any significant deterioration in image quality. The number of scans considered satisfactory were comparable even at 60-75 mA, although the total relative scores for structural resolution at this setting were lower. CONCLUSION: Tube current settings can be significantly reduced in all paediatric age groups, in all regions. In younger children the impact of such reduction in tube current is likely to be greater. Cranial scans are more sensitive to such reductions as compared to thoracic or abdominopelvic examinations.     

Circle of Willis at CT angiography: dose reduction and image quality--reducing tube voltage and increasing tube current settings

PURPOSE: To prospectively assess the effects of lower tube voltage and various effective tube currents on image quality for computed tomographic (CT) angiography of the circle of Willis. MATERIALS AND METHODS: Institutional review board approval was obtained. Patients or family provided written informed consent. Signal-to-noise ratios (SNRs) were determined in a head phantom for various effective tube currents with tube voltages of 90, 120, and 140 kVp. Patients were referred for CT angiography because of acute subarachnoid hemorrhage (n = 20) or family history of cerebral aneurysms (n = 20). In each group, 10 patients were scanned with 120 kVp and 200 mAs(eff) and 10 were scanned with 90 kVp and 330 mAs(eff) (CT dose index volumes, 27.2 mGy and 20.6 mGy, respectively). CT numbers were measured in the internal carotid artery at the T junction and compared with a t test. Two radiologists used a five-point scale to subjectively score arterial enhancement, depiction of small arterial detail, image noise, venous contamination, and interference of subarachnoid blood. Mann-Whitney U test was used for statistical analysis. RESULTS: In the phantom, SNR(2) was proportional to effective tube current and CT dose index volume. With an identical effective tube current, SNR(2) was lower at 90 kVp than at 120 or 140 kVp. With identical CT dose index volume, tube voltage of 90 kVp resulted in a 45%-52% increase of SNR(2) compared with SNR(2) at 120 kVp. In patients, mean attenuation in the internal carotid artery T junction was higher with 90 kVp (340 HU) than with 120 kVp (252 HU, P < .001). Although dose at 90 kVp was 30% lower than dose at 120 kVp, scores for arterial enhancement and depiction of small arterial detail were higher at 90 kVp than at 120 kVp (4.0 vs 3.2 and 3.6 vs 3.1, respectively; P < .005). CONCLUSION: In head phantoms, lower tube voltage improved SNR at equal radiation doses. For CT angiography of the circle of Willis, this translated into superior image quality at 90 kVp.     

多层螺旋CT自动毫安技术对腰椎患者扫描剂量减少的可行性研究

Objective To investigate the feasibility of achieving consistent image quality with dose reduction technology in lumber spine MSCT examination with Z-axis automatic tube current modulation (ATCM). Methods Forty-eight patients diagnosed as lumber intervertebral disc protrution scanned twice by MSCT before and after interventional operations with the same coverage from third lumbar vertebra to first sacral vertebra. The first scan (FM) was with fixed tube current of 320 mAs. The follow-up scan was with ATCM with noise index (NI) of 12.0 HU. At the levels of L3-4, L4-5 and 15-S1, image quality, image noise and radiation dose were measured and analyzed. Image quality and radiation dose were compared by paired t-test and the image noise was compared by ANOVA test. Results The dosage of the ATCM had a 31.3% reduction compared with FM, the average DLP was(187.9±66.4)mGy·cm and(273.4±45.4) mGy·cm respectively, where t = 8.205, P < 0.05. The average noise and their deviations for the FM group were (9.8±2.4) HU,(9.9±2.4) HU, and (11.5±3.2) HU at level of L3-4, L4-5, 15-S1, respectively. With ATCM, the average noise was(12.0±0.8) HU, (11.7±0.6) HU, and (11.7±1.4) HU, respectively. There was statistical difference between the two groups (F = 23.31, P < 0.05). The image quality scores for the FM group were (4.7±0.3), (4.5±0.2), (4.5±0.2) and showed no statistical difference to ATCM group (4.6±0.3), (4.5±0.2), (4.5±0.2) at level of L3-4, L4-5, L5-S1, respectively, where t = 1.000, P > 0.050 Conclusion ATCM technique with the noise index setting at 12.0 HU can achieved a 31.3% dose reduction while keep the consistent image quality for lumbar spine MSCT study.