器官剂量调制技术在头颅CT平扫中的应用

目的探讨头颅CT平扫中应用器官剂量调制(ODM)技术对辐射剂量及图像质量的影响。方法连续收集100例于我院接受头颅CT平扫患者,随机均分为试验组及对照组,每组50例。头颅CT平扫时,试验组在眼眶区域应用ODM技术;对照组采用常规扫描方法,扫描参数相同。记录2组眼眶区域各方向(前、后、左、右)的管电流、容积CT剂量指数(CTDI_(vol))、剂量长度乘积(DLP),计算有效辐射剂量(ED);分别于桥脑及双侧小脑半球选取ROI,测量并计算客观噪声及SNR。采用5分法对CT图像质量进行主观评分。结果头颅CT眼眶区域4个方向中,试验组在前方向上管电流明显低于对照组(t=9.72,P=0.01);2组间CTDI_(vol、)DLP及ED差异均无统计学意义(P均0.05),后颅窝颞骨岩部层面桥脑及双侧小脑半球客观噪声、SNR差异均无统计学意义(P均0.05)。2组主观图像质量评分≥3分,图像质量均可满足诊断需要;2组间图像质量评分差异无统计学意义(Z=0.25,P=0.31)。结论在头颅CT平扫中应用ODM技术可降低直射方向(前方)上的管电流,进而降低眼眶区域辐射剂量,能够在保护敏感器官的同时获得满足诊断要求的图像质量。     

低剂量宝石能谱CT引导经皮肺穿刺活检术

目的探讨低剂量宝石能谱CT用于引导经皮肺穿刺活检术的可行性。方法收集接受宝石能谱CT引导经皮肺穿刺活检术的80例患者,穿刺过程中均多次重复定位,依次采用常规剂量及噪声指数(NI)为20、24、28的低剂量CT扫描,比较常规剂量和低剂量CT图像质量及CT容积剂量指数(CTDI_(vol))、剂量长度乘积(DLP)及有效辐射剂量(ED)。结果常规剂量和低剂量CT图像均能清晰显示穿刺针和病灶的位置关系,可满足穿刺需要;常规剂量与NI为20、24、28的低剂量图像质量级别差异均无统计学意义(P=0.08),常规剂量与NI为20、24、28的低剂量图像的CTDI_(vol)、DLP、ED差异均有统计学意义(P均0.01),且随着NI增加,CTDI_(vol)、DLP和ED逐渐降低(P均0.05)。结论低剂量宝石能谱CT扫描图像可以满足经皮肺穿刺活检术需要,并降低辐射剂量。     

低管电压联合低剂量对比剂扫描方案用于MSCT门静脉成像

目的探讨低管电压联合低对比剂扫描方案用于MSCT门静脉成像(MSCTP)的可行性。方法纳入接受MSCTP、体质量指数25kg/m2的患者118例,随机分为两组:双低组(n=59),管电压90kVp,管电流395mAs,对比剂用量1.2ml/kg体质量;常规组,管电压120kVp,管电流200mAs,对比剂用量1.5ml/kg体质量。比较两组门静脉期图像质量评分、肝实质CT值(CTH)、门静脉CT值(CTP)、图像噪声(SD),肝实质SNR(SNRH)、门静脉与肝实质CNR(CNRP)及有效剂量(ED)差异。结果双低组图像质量评分(4.53±0.32)高于常规组(3.71±0.32,P0.05);双低组CTH[(101.11±16.65)HU]、CTP[(186.94±29.29)HU]、SNRH(6.92±2.28)和CNRP(5.71±2.00)均明显高于常规组[CTH:(83.61±13.94)HU,CTP:(141.85±26.89)HU,SNRH:6.05±1.58,CNRP:4.23±1.65;P均0.05],两组图像SD差异无统计学意义[(16.32±9.21)HU vs(14.33±2.32)HU,P0.05];双低组ED[(3.81±0.44)mSv]明显低于常规组[(5.77±0.52)mSv,P0.05)。结论采用低管电压结合低剂量对比剂扫描方案进行MSCTP可提高图像质量,并降低辐射剂量。     

80 kVp管电压冠状动脉CTA联合ASiR-V图像重建用于超重和Ⅰ级肥胖患者的可行性

目的探讨80 kVp管电压冠状动脉CTA(CCTA)联合体积自适应统计迭代重建-V(ASiR-V)图像重建应用于超重和Ⅰ级肥胖患者的可行性。方法将120例接受CCTA检查的超重和Ⅰ级肥胖患者随机分为80 kVp组和100 kVp组,每组60例,分别于80、100 kVp管电压下行CCTA,并采用权重为60%的ASiR-V进行图像重建。对比2组图像质量,各部位CT值、SNR、对比噪声比(CNR)、容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP)、对比剂剂量及有效辐射剂量。结果 80 kVp组和100 kVp组图像质量评分差异无统计学意义(P0.05)。2组CTDIvol、DLP、对比剂剂量、有效辐射剂量差异均有统计学意义(P均0.05);2组主动脉根部、右冠状动脉、左前降支及左回旋支CT值差异无统计学意义,右冠状动脉、左前降支及左回旋支SNR、CNR差异无统计学意义(P均0.05)。结论 80 kVp管电压CCTA联合60%ASiR-V图像重建应用于超重和Ⅰ级肥胖患者,可获得与100 kVp管电压相当的图像质量,且对比剂剂量及有效辐射剂量均减少。     

CT自动毫安调节技术联合低对比剂增强扫描在诊断甲状腺乳头状癌中的应用

目的探讨CT自动毫安(Auto mA,AM)低辐射扫描联合低对比剂CT增强扫描在甲状腺乳头状癌诊断中的应用。方法2018年2月至2020年1月经病理证实的133例160枚甲状腺乳头状癌,术前分为四组。A组:120kV,250mA,对比剂用量1.2ml/kg;B组:120kV,250mA,对比剂用量1.0ml/kg;C组:120kV,AM (100～400 mA),对比剂用量1.2ml/kg;D组:120kV,AM (100～400 mA),对比剂用量1.0ml/kg。记录患者的CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP),并计算有效辐射剂量(ED);观察甲状腺结节的数量、体积、纵横比、边缘情况、增强后模糊、钙化、咬饼征及颈部淋巴结及诊断符合率,对比分析四组间CTDIvol、DLP、ED、甲状腺乳头状癌各征象及诊断符合率是否有统计学差异。结果四组间CTDIvol、DLP、ED有统计学差异,甲状腺乳头状癌数量、体积、纵横比、边缘情况、增强后模糊、钙化、咬饼征及诊断符合率无明显统计学差异,颈部淋巴结显示率组间有统计学差异,且C、D组高于A、B组,组间比较有统计学差异。结论自动毫安(AM)低辐射联合低对比剂CT增强扫描在保证对甲状腺乳头状癌诊断同时降低了CT辐射剂量及对比剂的用量,减少了辐射危害及对比剂的不良反应。     

双低剂量64层螺旋CT腹部多期增强扫描与血管成像对血运性肠梗阻治疗方式选择的价值

研究双低剂量64层螺旋CT腹部多期增强扫描与血管成像对指导血运性肠梗阻治疗方式的选择价值。前瞻性选取2015年6月—2018年6月中山大学附属第八医院收治的84例血运性肠梗阻患者,均经外科手术或数字减影血管造影(DSA)证实为血运性肠梗阻。按随机数字表法将患者分为研究组和对照组两组,每组各42例。对照组采用对比剂浓度为370 mg I/m L的优维显和120 k V管电压进行64层螺旋CT扫描,研究组采用对比剂浓度为320 mg I/m L的碘佛醇和100 k V管电压进行64层螺旋CT扫描。对两组血管图像主观评分和客观评价及辐射剂量进行比较分析,评估两组影像学图像质量及信噪比(SNR)、噪声比(CNR)、噪声、CT值等。分析两组辐射剂量情况,包括剂量长度乘积(DLP)、容积CT计量指数(CTDIvol)、有效辐射剂量(ED)及碘总量。两组血管图像中肠系膜动脉血管图像及肠系膜静脉血管图像主观评分差异无统计学意义(P0.05)。两组血管图像噪声值差异无统计学意义(P0.05);研究组CT值、SNR及CNR均优于对照组(P0.05)。研究组CTDIvol、碘总量、ED及DLP等辐射剂量明显低于对照组(P0.05)。双低剂量64层螺旋CT腹部多期增强扫描与血管成像对血运性肠梗阻患者检查效果较好,明显降低辐射剂量,获得更好图片,利于疾病诊断和指导治疗,值得临床应用及推广。     

智能最佳管电压调节技术在儿童埋伏牙CT扫描中的应用

目的探讨双源CT智能最佳管电压调节(CARE kV)技术在儿童埋伏牙扫描中的应用价值。方法对90例埋伏牙患儿行CT扫描,并分为A、B、C 3组,每组30例,A组常规扫描(100kVp/150mAs),B组开启CARE Dose 4D扫描(100kVp/参考管电流150 mAs),C组CARE kV联合CARE Dose 4D扫描(参考管电压100kV/参考管电流120mAs)。比较3组的辐射剂量、图像平均CT值、噪声、SNR、CNR、主观评分及CT诊断与临床诊断的差异。结果 3组实际扫描管电流、管电压及辐射剂量差异均有统计学意义(P均0.05),与A组比较,B组有效剂量(ED)减低约15.74%,C组ED减低26.85%;图像的平均CT值、噪声、SNR、CNR及主观评分比较差异均无统计学意义(P均0.05);3组CT与临床诊断结果比较差异无统计学意义(P0.05)。结论采用双源CT智能最佳管电压调节技术行儿童埋伏牙CT扫描,可有效降低辐射剂量,在保证图像质量的同时,不影响诊断。     

低管电压扫描条件下个体化对比剂用量方案在冠状动脉CTA中的应用

目的探讨冠状动脉CTA中以体质量指数(BMI)与体表面积(Suf)作为个体化分类标准,联合100kV低管电压扫描,降低对比剂用量、提高造影效率和图像质量的价值。方法入组患者17.0≤BMI26.5,分为120kV组(A组)与100kV组(B组),各100例。A组扫描管电压120kV,管电流600mA;对比剂0.8~1.0ml/kg(总量约65ml),生理盐水50ml,注射流率均为5.0ml/s。A组检查完毕后采用线性回归分析对比剂用量与BMI、Suf关系,制成量化速查表。B组扫描管电压100kV,管电流600mA;对比剂根据上述速查表采用35~65ml,生理盐水30~50ml(对比剂总量×80%),注射流率均为5.0ml/s。结果两组对比剂用量、主动脉强化值、左心室强化值、图像噪声、辐射剂量指数、有效剂量差异均有统计学意义(P均0.05),B组较A组对比剂用量下降28.16%、主动脉强化值提高21.58%;辐射剂量指数下降39.54%、有效剂量下降40.83%、噪声值升高27.15%。两组图像质量评分B组优于A组(P0.01)。结论以BMI、Suf作为个体化分类标准,可降低检查中对比剂用量、提高造影效率;结合100kV低管电压扫描,能在显著降低辐射剂量的同时改善图像质量。     

双源CT低剂量扫描在上腹部增强检查中的应用

目的探讨双源CT上腹部增强扫描中低剂量技术的应用。方法搜集2011年7月至2012年2月期间来我院行双源CT上腹部增强检查的连续600例患者,按就诊时间先后分别依次采用常规管电流量(210 mAs)和低管电流量(200、190、180、170及165 mAs)扫描,分别为常规管电流量组和低管电流量组。测量、计算并评估各组患者动脉期和门脉期图像的皮下脂肪标准差(SD)值、肝脏和胰腺信噪比(SNR)、肝脏-竖脊肌和胰腺-竖脊肌对比噪声比(CNR)、图像主观质量评分以及射线剂量指标CT剂量指数(CTDI)、剂量长度乘积(DLP)、有效剂量(ED)。结果各组患者动脉期和门脉期图像的皮下脂肪SD值、肝脏和胰腺SNR、图像主观质量评分和射线剂量指标CTDI、DLP、ED之间差异均有统计学意义(P<0.05);各组肝脏-竖脊肌和胰腺-竖脊肌CNR之间差异无统计学意义(P>0.05)。其中165 mAs管电流量组图像SNR、射线剂量和主观质量评分均为最低,不能满足诊断需求。结论上腹部增强CT检查,通过阶段性降低管电流量使诊断医生逐渐适应低剂量图像质量,从而普及现有设备的低剂量扫描的方法是可行的。双源CT采用170 mAs的参考管电流量,既能获得满足临床诊断的合格图像,又能大大降低患者群体接受的辐射剂量。     

低管电压联合管电流自动调节技术降低下肢动脉CTA辐射剂量

目的探讨低管电压结合管电流自动调节技术实现下肢动脉CTA低剂量扫描的可行性。方法将64例患者分为3组行下肢动脉CTA检查,A组管电压120kV,管电流自动调节范围50~250mA;B组管电压100kV,管电流自动调节范围50~350mA;C组管电压80kV,管电流自动调节范围100~350mA;获得腹主动脉、股动脉及腘动脉CT值、图像噪声、SNR、扫描长度(SL)、容积CT剂量指数(CTDIvol)及剂量长度乘积(DLP)。并对图像质量进行主观评价。结果3组间腹主动脉、股动脉及腘动脉CT值、图像噪声、SNR差异均有统计学意义(P均0.05)。3组间SL差异无统计学意义(P0.05),CTDIvol、DLP差异均有统计学意义(P均0.05)。A、B、C组图像均可满足诊断要求,主观图像质量评分分别为(2.50±0.51)分、(2.44±0.63)分及(2.41±0.56)分,差异无统计学意义(P0.05)。结论低管电压结合管电流自动调节技术,可在获得符合诊断要求图像的同时,降低下肢动脉CTA扫描辐射剂量。     

能谱纯化结合高级模拟迭代重建在成人胸部低剂量CT中的应用

目的探讨第3代双源CT能谱纯化结合高级模拟迭代重建(ADMIRE)技术在成人胸部低剂量CT检查中的应用价值。方法将100名成年体检者随机均分为A组和B组,采用Siemens Force双源CT扫描仪行胸部CT检查。对A组采用常规100kV扫描结合ADMIRE(强度3级)重建(获得A-ADMIRE图像),B组采用能谱纯化(Sn 100kV)扫描结合ADMIRE(强度1~5级)重建(分别获得B-ADMIRE1、B-ADMIRE2、B-ADMIRE3、B-ADMIRE4、B-ADMIRE5图像)。肺窗及纵隔窗图像ROI包括肺组织、胸主动脉、竖脊肌、背部皮下脂肪及背景空气。比较2组间辐射剂量指标的差异及2组不同ADMIRE图像间客观评价指标、主观图像质量评分的差异。结果 B组CT剂量指数(CTDIvol)、剂量长度乘积(DLP)及有效剂量(ED)均较A组明显下降(P均0.01)。2组不同ADMIRE图像间肺窗及纵隔窗各ROI图像噪声差异均有统计学意义(P均0.01),其中B-ADMIRE1图像噪声最高;肺组织、胸主动脉、竖脊肌信噪比(SNR)及肺组织-背部皮下脂肪、胸主动脉-竖脊肌、胸主动脉-背部皮下脂肪对比噪声比(CNR)差异均有统计学意义(P均0.01),其中AADMIRE图像SNR、CNR最高。B组中ADMIRE1~5图像噪声呈逐级递减趋势,SNR及CNR均呈逐级递增趋势(P均0.01)。2组不同ADMIRE图像间肺窗及纵隔窗图像质量评分差异均有统计学意义(P均0.01),其中AADMIRE图像质量评分最高。B组中B-ADMIRE3图像肺窗及纵隔窗图像质量评分最高,分别为(3.89±0.26)分和(3.00±0.15)分,均可满足诊断要求。结论成人胸部低剂量CT检查中,采用能谱纯化结合ADMIRE技术可在满足诊断要求的同时有效减低辐射剂量,且ADMIRE 3级强度重建图像质量最佳。     

Revolution CT能谱成像测量腰椎体模骨密度的准确性及可重复性

目的观察Revolution CT能谱成像测量腰椎体模骨密度(BMD)的准确性及可重复性。方法采用2台同型号Revolution CT,分别以不同管电流及不同球管转速组合共计20组扫描条件对欧洲腰椎体模(ESP)重复进行10次扫描;利用能谱物质分离功能分别测量体模L1、L2、L3椎体羟基磷灰石(HAP)值,比较HAP测值与真实值之间的差异,评价其准确性;记录各扫描条件下CT容积剂量指数(CTDI_(vol))。对比不同CT设备之间测量结果的可重复性。结果 20组条件下,L1、L2、L3椎体HAP测值差异均有统计学意义(P均0.001)。取管电流230 mA、球管转速0.8 s/rot及管电流315 mA、球管转速1.0 s/rot,L1、L2、L3椎体HAP测值与体模实际值差异均无统计学意义(P均0.05),CTDI_(vol)分别为9.09 mGy和15.46 mGy,且2台CT所测L1、L2、L3椎体HAP值差异无统计学意义(P均0.05)。结论 Revolution CT扫描测量ESP BMD准确性高,尤以球管转速0.8 s/rot配合管电流230 mA条件准确性更高,且辐射剂量低;同型号不同CT设备间可重复性好。     

Optimization of acquisition parameters for reduced-dose thoracic CT: A phantom study

PurposeThe purpose of this study was to analyze the impact of different options for reduced-dose computed tomography (CT) on image noise and visibility of pulmonary structures in order to define the best choice of parameters when performing ultra-low dose acquisitions of the chest in clinical routine.Materials and methodsUsing an anthropomorphic chest phantom, CT images were acquired at four defined low dose levels (computed tomography dose index [CTDI_vol] = 0.15, 0.20, 0.30 and 0.40 mGy), by changing tube voltage, pitch factor, or rotation time and adapting tube current to reach the predefined CTDI_vol-values. Images were reconstructed using two different levels of iteration (adaptive statistical iterative reconstruction [ASIR®]-v70% and ASIR®-v100%). Signal-to-noise ratio (SNR) as well as contrast-to-noise ratio (CNR) was calculated. Visibility of pulmonary structures (bronchi/vessels) were assessed by two readers on a 5-point-Likert scale.ResultsBest visual image assessments and CNR/SNR were obtained with high tube voltage, while lowest scores were reached with lower pitch factor followed by high tube current. Protocols favoring lower pitch factor resulted in decreased visibility of bronchi/vessels, especially in the periphery. Decreasing radiation dose from 0.40 to 0.30 mGy was not associated with a significant decrease in visual scores (P < 0.05), however decreasing radiation dose from 0.30 mGy to 0.15 mGy was associated with a lower visibility of most of the evaluated structures (P < 0.001). While image noise could be significantly reduced when ASIR®-v100% instead of ASIR®-v70% was used, the visibility-scores of pulmonary structures did not change significantly.ConclusionFavoring high tube voltage is the best option for reduced-dose protocols. A decrease of SNR and CNR does not necessarily go along with reduced visibility of pulmonary structures.     

Radiation exposure – how do CT scans for appendicitis compare between a free standing children’s hospital and non-dedicated pediatric facilities?

Background

We compare the amount of radiation children receive from CT scans performed at non-dedicated pediatric facilities (OH) versus those at a dedicated children’s hospital (CH).

Methods

Using a retrospective chart review, all children undergoing CT scanning for appendicitis at an OH were compared to children undergoing CT imaging for appendicitis at a CH between January 2011 and November 2012.

Results

One hundred sixty-three children underwent CT scans at 42 different OH. Body mass index was similar between the two groups (21.00 ± 6.49 kg/m², 19.58 ± 5.18 kg/m², P = 0.07). Dose length product (DLP) was 620 ± 540.3 at OH and 253.78 ± 211.08 at CH (P < 0.001). OH CT scans accurately diagnosed appendicitis in 81%, while CT scans at CH were accurate in 95% (P = 0.026). CTDI_vol was recorded in 65 patients with subset analysis showing CTDI_vol of 16.98 ± 15.58 and 4.89 ± 2.64, a DLP of 586.25 ± 521.59 and 143.54 ± 41.19, and size-specific dose estimate (SSDE) of 26.71 ± 23.1 and 3.81 ± 2.02 at OH and CH, respectively (P < 0.001).

Conclusion

Using SSDE as a marker for radiation exposure, children received 86% less radiation and had improved diagnostic accuracy when CT scans are performed at a CH.     

64层螺旋CT低剂量双相扫描测定肺体积评价慢性阻塞性肺疾病患者肺功能

目的探讨64层CT低剂量双相扫描肺体积测量指标评估慢性阻塞性肺疾病(COPD)患者肺功能的价值。方法选择经临床肺功能检查确诊的36例COPD患者(COPD组)及30名健康体检者(正常对照组),采用64层CT行深吸气末、深呼气末全肺低剂量(50mAs)及常规剂量(100mAs)吸气末扫描,得出每次扫描的容积CT剂量指数(CTDIvol)和剂量长度乘积(DLP),并换算出有效剂量(ED)。以配对样本t检验比较两组间不同扫描剂量及不同呼吸状态下的CT-DIvol、DLP、ED;应用Fisher确切概率法比较CT图像质量。按扫描层数将全肺分为上、中、下3个肺区,应用Pulmo软件测量和计算COPD组与正常对照组的各体积指标:深吸气末体积(Vin)、深呼气末体积(Vex)、体积差(Vin-Vex)、体积比(Vex/Vin)、体积变化百分比(Vin-Vex)/Vin×100%。于CT检查前后3天完成PFT检查,对比研究指标为第1秒用力肺活量(FEV1)的实测值与预计值的比值(FEV1%)及FEV1与用力肺活量(FVC)的比值(FEV1/FVC)。结果所有图像均成功用于自动分割技术与数据处理。与正常对照组比较,COPD组除各肺区的Vin及上肺区Vin-Vex外,其余各体积指标差异均有统计学意义(P均<0.05);Vex、Vex/Vin、(Vin-Vex)/Vin×100%均与FEV1%、FEV1/FVC存在相关性(P<0.01)。结论 64层CT低剂量双相扫描肺体积指标可较好评价COPD患者肺功能,临床应用价值较高。     

Noise assessment across two generations of iterative reconstruction algorithms of three manufacturers using bone reconstruction kernel

PurposeTo compare the noise-magnitude and noise-texture obtained using strong kernel across two generations of iterative reconstruction (IR) algorithms proposed by three manufacturers.Materials and methodsFive computed tomography (CT) systems equipped with two generations of IR algorithm (hybrid/statistical IR [H/SIR] or full/partial model-based IR [MBIR]) were compared. Acquisitions on Catphan 600 phantom were performed at 120 kV and three dose levels (CTDI_vol: 3, 7 and 12mGy). Raw data were reconstructed using standard “bone” kernel for filtered back projection and one iterative level of two generations of IR algorithms. Contrast-to-noise ratio (CNR) was computed using three regions of interest placed semi-automatically: two placed in the low-density polyethylene and Teflon inserts and another placed on the solid water. Noise power spectrum (NPS) was computed to assess the NPS-peak and noise-texture.ResultsCNR was significantly greater in MBIR compared to H/SIR algorithms for all CT systems (P < 0.01). CNR were improved on average from H/SIR to MBIR of 36 ± 14% [SD] (range: 24–57%) for GE-Healthcare, 109 ± 19 [SD] % (range: 89–139%) for Philips Healthcare and 42 ± 5 [SD] % (range: 36–47%) for Siemens Healthineers. The mean NPS peak decreased from H/SIR to MBIR by ?41 ± 6 [SD] % (range: ?47–?35%) for GE Healthcare, ?79 ± 3 [SD] % (range: ?82–?76%) for Philips Healthcare and ?52 ± 2 [SD] % (range: ?54–?51%) for Siemens Healthineers systems. NPS spatial frequencies were greater with MBIR than with H/SIR for Philips Healthcare (20 ± 2 [SD] %; range: 19–22%) and for Siemens Healthineers (9 ± 5 [SD] %; range: 4–14%) but lower for GE Healthcare (?17 ± 3 [SD] %; range: ?14–?20%).ConclusionUsing bone kernel with recent MBIR algorithms reduces the noise-magnitude for all CT systems assessed. Noise texture shifted towards high frequency for Siemens Healthineers and Philips Healthcare but the opposite for GE Healthcare.     

双源CT头颈心一站式扫描对动脉粥样硬化的应用价值

目的探讨双源CT头颈心一站式扫描对动脉粥样硬化(AS)患者的应用价值。方法将120例AS患者随机分为2组,每组60例。对A组行头颈心一站式扫描,B组分别行常规冠状动脉CTA及头颈部血管CTA扫描。对2组图像质量进行主观及客观评价;主观评分采用3分法,客观评价指标包括左冠状动脉主干、右冠状动脉中段、颈总动脉近分叉处、颈内动脉C1段、大脑中动脉M1段血管的平均SNR及其相对于脊柱旁肌肉的CNR。记录2组CTA扫描长度、扫描时间、剂量长度乘积(DLP)和有效剂量(ED),并进行统计学分析。结果 2组图像质量评分差异无统计学意义(t=0.596,P=0.283),SNR及CNR差异亦无统计学意义(t=0.828、0.761,P=0.104、0.089)。2组间CTA扫描长度差异无统计学意义(t=1.351,P=0.621),但A组较B组扫描时间更短[(1.30±0.12)s vs (4.08±0.69)s,t=-2.831,P=0.006],DLP[(146.03±13.05)mGy·cm vs (1 935.04±134.12)mGy·cm,t=-6.743,P0.01]及ED[(0.88±0.32)mSv vs (9.62±1.64)mSv,t=-4.056,P0.01]更低。结论对AS患者,双源CT头颈心一站式扫描技术能获得满意的冠状动脉、头颈动脉图像,同时显著降低辐射剂量。     

Which dose for what image? Iterative reconstruction for CT scan

PurposeTo evaluate the potential of iterative reconstruction for reducing the dose given to the patient during abdominal CT scanning.Materials and methodsA double abdominal CT scan acquisition (Somatom Definition AS+ Siemens) performed without contrast administration at –30% and at –70% of the doses (mAs) was compared to the standard acquisition in 10 patients. The raw data were reconstructed by filtered back projection (FBP) and using the SAFIRE iterative reconstruction method (five levels of iteration). The signal, noise, signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) were compared for three regions of interest, including the kidney, psoas and abdominal fat.ResultsThe signal in each region of interest was not modified based on the type of reconstruction. The noise level decreased significantly during the passage from the FBP to SAFIRE, as well as with the increase in the SAFIRE level. The SNR and CNR therefore increased with the use of iterative reconstructions. The increase in noise observed between the acquisition at –30% and that at –70% was compensated by the use of higher SAFIRE levels.ConclusionIterative reconstructions can be used to improve the SNR and CNR at a constant dose or to reduce the dose by keeping the same SNR and CNR on abdominal CT images.