| BackgroundCoronary atherosclerotic heart disease(CAD)is one of the most common cardiovascular diseases in clinical.CAD may affect individuals at any age,but becomes dramatically more common at progressively older ages,with approximately a tripling with each decade of life.Males are affected more often than females,and the incidence rate of CAD in man is significantly higher than that in women of a given age.In recent years,the incidence rate of CAD is increased,and the prevalence age trends to be younger.CAD is the most common cause of death globally,resulting in 8.14 million deaths(16.8%)in 2013.In our country,at least 1 million people die of CAD every year.CAD has a serious hazard for human healthy,so early detection,early diagnosis and early intervention of CAD is of great importance.Invasive coronary angiography(ICA)can relatively accurately assess the location of coronary artery plaque,the degree of stenosis and distal blood flow,as well as deal with percutaneous coronary intervention(PCI)at the same time.ICA has long been considered as a golden standard for the assessment of the degree of coronary artery stenosis,but cannot be used as a routine screening tool due to its invasion,and it cannot reveal the characteristics of plaque.With continuing technology advances,CT angiography(CTA)and cardiac CT has largely replaced ICA.However,the new technology of CT brings new challenges to us,including optimization of standardized protocols,reduction of radiation dose,management of large image data sets,and assurance of diagnostic accuracy.Technology advances in CT resulted in a significant reduction in scan and acquisition time(<1-6 seconds,depending on scan mode)and artifacts due to breathing and coronary artery pulse.The opportunity of maximizing clinical benefit while overcoming technical challenges is equally applicable to the use of intravenous contrast medium(CM).The reduction of scan and acquisition time made adoption of a smaller volume of CM to be possible.Although technology advances in CT allow more efficient and flexible application of CM,certain technical challenges,including scan timing relative to maximum contrast enhancement and optimal contrast material delivery(iodine delivery rate,IDR),must be met to fully reap the benefits of multidetector CT.Previous studies demonstrated that at least 325 Hounsfield unit(HU)enhancement levels in the coronary arteries were necessary for optimal diagnosis.Lower enhancement levels yielded poorer contrast between the arteries and their surrounding tissues which was unfavorable for diagnostic accuracy.Higher enhancement levels produced steak artifacts and obscured small calcified plaques.Arterial attenuation is determined by injection-related parameters,scan-related parameters and patient-related factors.The injection-related parameters include CM concentration,CM volume,injection velocity,IDR,total iodine dose(TID),saline flush,CM viscosity,temperature of CM injection and needle type.The scan-related parameters include scan protocol,scan duration,scan delay,tube voltage,tube current and reconstruction kernel.The patient-related factors include cardiac output,blood volume,heart rate,weight,height,body mass index(BMI),body surface area(BSA),breathing control,hepatic and renal function and other various pathologic conditions.Previous CCTA protocols did not adapt to individual body weight or cardiac output.Consequently,vessel attenuation in CCTA has been shown to vary largely.In recent years,individualized CCTA protocols have attracted more and more attention.Patient related factors are strongly related to the degree of contrast enhancement.The goal in the future is to explore more individualized CCTA protocols.Previous studies have mainly focused on the impact of body weight and BMI on intravascular attenuation with variable results.In terms of patient related factors,a correlation between intravascular attenuation and body weight has been confirmed previously,and body weight adapted CM injection in CCTA has been widely used.A standardized protocol with a constant CM volume,independent of weights and lengths of patients,can undoubtedly lead to an over-and underestimation of the CM volume in certain weight ranges,resulting in attenuation of the degree of contrast enhancement of the coronary arteries as well as undesirable consequences on image quality.However,patients with comparable body weight undergoing standard CCTA protocol with standard injected CM volume have different contrast enhancement in solid organs and vessels,because simple body weight-based linearity can not provide an accurate estimation of the required CM doses.Additionally,physical factors such as cardiac output and muscle mass(concept of lean body weight)differ substantially between patients with comparable body weight,resulting in variability in solid organ and vascular enhancement.Recently,a BMI adapted protocol was introduced to reduce the impact of BMI on image noise.However,coronary contrast remained subject to large variation,presumably due to bolus dilution depending on blood volume.As blood volume is well paralleled by BSA,we identified BSA as the most promising parameter to be of potential value for adjusting the contrast bolus in future protocols.ObjectiveThe purpose of our study was to evaluate the efficacy and safety of individually BSA-versus body weight-adapted CM injection in CCTA with 2nd DSCT.MethodsThis study was conducted at Shandong Provincial Medical Imaging Institute,Jinan,China.We enrolled 270 consecutive participants who had been referred for CCTA for suspected coronary artery disease between March 2015 and September 2015.270 enrolled patients were randomly assigned into 3 groups(90 patients for each group)according to different CM injection protocols.The three groups adopted the uniphasic CM protocol with fixed injection time of 15s followed by 30ml saline flush,loversol 320(320mgl/100ml,Jiangsu Hengrui Medicine Co.,Ltd.,Lianyungang,Jiangsu,China)was used in all patients.In control group,all patients were injected with fixed volume of 75 ml and fixed flow rate of 5ml/s.In BW-adapted group,patients were injected with the volume of 0.9 ml per BW and the flow rate of 0.06 ml/s per BW.In BSA-adapted group,patients were injected with the volume of 36.5 ml per BSA and the flow rate of 2.4 ml/s per BSA.CM injection was timed by bolus tracking in a sample region of interest,the descending aorta,with the scan begun 10 s after exceeding a threshold of 100 Hounsfield units(HU).All studies were performed on a 2nd generation 128-slice DSCT system(SOMATOM Definition Flash,Siemens Healthcare,Forchheim,Germany).All scans were performed in a craniocaudal direction with prospective electrocardiogram(ECG)-gated protocol.The images were reconstructed with sinogram-affirmed iterative reconstruction(SAFIRE,Siemens Healthcare,Forchheim,Germany)algorithm using the corresponding vascular kernel(126f).The adjustable increment of strength 1 was used for adaptation of the noise model.Transverse images were reconstructed at 0.75 mm slice thickness with a 0.5 mm increment and in a matrix size of 512x512.All images were anonymized and transferred to an picture archiving and communicating system(PACS)(syngo MMWP VE 36A,Siemens Healthcare,Forchheim,Germany)for further image analysis.Two experienced observers,who were blind to the groups,evaluated the CTA images,independently.All statistical analysis was performed using SPSS software(SPSS v19.0,Chicago,ILL,USA).Quantitative variables were expressed as mean ±standard deviation(SD),and categorical variables were expressed as frequencies and percentages.Inter-group differences were evaluated by Welch's test,Mann-Whitney U test or independent-samples t test.P value<0.05 was considered statistically significant.ResultsThe basic characteristics of the subjectIn this study,270 patients were enrolled in this study,90 patients in each group were treated with traditional contrast agent regimen,body weight-adapted regimen and BSA-adapted regimen.There were no significant differences in gender,age,body weight,height,BMI,BSA,heart rate,blood pressure,history and risk factors among the three groups.Image quality evaluationThe control group was not adjusted individually according to the subject's weight or BSA.All subjects injected the same dose of contrast agent at the same rate of injection.The results showed that the degree of enhancement of the coronary arteries in the control group varied largely(398 ± 157HU).The degree of enhancement of the coronary arteries in the BW-or BSA-adapted group is higher,of which BSA-adapted better.Compared with the control group,the coronary artery enhancement degree of the subject group was significantly lower than that of the control group(P<0.05),and the mean value of the coronary arteries was higher than that of the control group(P<0.05),and the difference was statistically significant P<0.01).The CT value of the BSA group was higher than that of the body weight control group(476 HU vs.447 HU),the standard deviation was lower than that of the body weight control group(89 HU vs.106 HU),and the CT value was statistically significant(P<0.05).Compared with the control group(3.76 ± 0.95),the image quality score of the body weight adjustment group increased slightly(3.93 ± 0.62),but the difference was not statistically significant(P>0.05);compared with the control group,(P<0.05).Compared with the body weight control group,the image quality score of the BSA group was slightly higher than that of the control group(P>0.05),but the difference was not significant(P>0.05)The amount of the contrast agent and the flow rateIn the three contrast agent injections,the control group was not adjusted according to the body weight or BSA of the patients.Compared with the control group and the BSA group,the contrast agent dosage was large and the average injection flow rate was fast,the difference was statistically significant(P<0.01).There was no significant difference in the amount and flow rate of contrast agent between the two groups(P>0.05).Safety evaluationThere was no significant difference in radiation dose between the three groups(P>0.05).All subjects did not show significant adverse events during CCTA examination.There was no significant difference between the threegroups(P>0.05).ConclusionBSA-adapted protocol exhibited in a relatively low CM volume and flow velocity,as well as a relatively high degree of contrast enhancement andimage quality.The efficacy and safety of BSA-adapted protocol in CCTA are compelling.However,more large-scale,multinational,multicenter and prospective trials are warranted.BackgroundIn recent years,nondestructive coronary CT angiography(CCTA)has attracted increasing attention and has been widely used in the diagnosis of coronary artery disease.64-row and more advanced CT devices are capable of meeting the requirements of cardiac and coronary angiography.These CT devices including 64-row spiral CT,post 64-row CT and dual source CT(DSCT)can provide prospective ECG-triggering scan mode and automatic tube voltage regulation technology to reduce radiation dose.Siemens 2nd 128-layer 4D Flash DSCT(SOMATOM Definition Flash)and 3rd DSCT(SOMATOM Force)can provide prospective ECG-triggering large pitch(pitch up to 3.4)scan mode to further reduce radiation dose to<1.0 mSv.Contrast media(CM)is usually used to be administrated into the body to enhance the contrast of tissues and organs.The most widely used CM in CT enhancement is iodinated contrast medium(ICM).ICM can be divided into ionic monomers,ionic dimmers,nonionic monomers and nonionic dimmers on the basis of their chemical structure and ionization in solution.ICM can also be divided into high-osmolality CM(>1500mOsm/kgH2O),sub-high-osmolality CM(600-850 mOsm/kgH2O)and iso-osmolality CM(290-320 mOsm/kgH20)as compared with plasma osmolality.The high-osmolality is related to some adverse events of ionic monomer.The low-osmolality ICM include nonionic monomers,ionic dimmers and nonionic dimers.For a given iodine concentration,nonionic monomers have approximately one-half of the osmolality of ionic monomers in solution.The nonionic monomers are widely used in clinical practice due to their relative low osmolalities and potentially less chemotoxic side effects than the ionic monomers.Application of CM may result in adverse reactions,which can be divided into intoldiosyncratic reactions(such as urticaria,vascular edema,laryngeal edema,bronchial spasm,severe hypotension,sudden death,and so on)and physicochemical reactions(such as nausea,vomiting,flushing,fever,local pain,and so on).The intoldiosyncratic reactions are related to individual characteristics regardless of the amount of CM,whereas the incidence and severity of the physicochemical reactions have a clear relationship with the amount of CM.The physicochemical reactions are associated with the osmotic pressure,water solubility,charge,and viscosity of the CM.The osmotic pressure of the CM commonly used in clinical is significantly higher than that of the plasma,leading to diverse adverse reactions,such as damages to endothelium,blood brain barrier and red blood cells,high blood volume,renal,hepatic and heart toxicity,pain and vasodilatation.The iodine concentration of CM is associated with its osmotic pressure and viscosity.The amount of CM is an independent risk factor for contrast-induced nephropathy(CIN).Cigarroa et al proposed the formula for the amount of CM:5ml × body weight(Kg)/serum creatinine(SCr;mg/dL),with the maximum amount no more than 300 ml.Results demonstrated that the incidence rate of CIN was 21-37%under the threshold dose and 0-2%above the threshold dose Therefore,the selection of optimal CM,optimal iodine concentration and the minimum amount of CM is critical to reduce the physicochemical reactions.Previous studies demonstrated that at least 325 Hounsfield unit(HU)enhancement levels in the coronary arteries were necessary for optimal diagnosis.Lower enhancement levels yielded poorer contrast between the arteries and their surrounding tissues which was unfavorable for diagnostic accuracy.Higher enhancement levels produced steak artifacts and obscured small calcified plaques.Arterial attenuation is determined by injection-related parameters,scan-related parameters and patient-related factors.The injection-related parameters include CM concentration,CM volume,injection velocity,iodine delivery rate(IDR),total iodine dose(TID),saline flush,CM viscosity,temperature of CM injection and needle type.The scan-related parameters include scan protocol,scan duration,scan delay,tube voltage,tube current and reconstruction kernel.The patient-related factors include cardiac output,blood volume,heart rate,weight,height,body mass index(BMI),body surface area(BSA),breathing control,hepatic and renal function and other various pathologic conditions.Recently,a body weight/BMI adapted protocol was introduced to reduce the impact of body weight/BMI on image noise.However,variations in coronary contrast remained very large,presumably due to bolus dilution depending on blood volume.As increased blood volume is well paralleled by BSA,we have identified BSA as the most promising parameter to be of potential value for adjusting the contrast bolus in future protocols.Bae et al proposed that BSA or BMI adjusted CM application might be more accurate than body weight,and recommended that CM should be adjusted based on BMI,fat body weight and BSA.Aju P.Pazhenkottil et al.also confirmed that a BSA-adapted CM protocol resulted in a comparable coronary contrast enhancement independent of individual BSA with a significant reduction in the amount of CM.Our study formulated more individualized BSA adjusted CM protocol with fixed iodine flow dose per BSA.Moreover,there was no literature or guideline that comparing the effect of different iodine concentrations of CM on coronary contrast enhancement,by use of a standardized CM injection protocol based on BSA or body weight.ObjectiveThe aim of this study was to investigate the efficacy of the personalized application of different iodine concentrations of CM in coronary CT angiography with 2nd DSCT in eliminating differences in coronary contrast enhancement on the basis of BSA adapted CM injection protocol as well as HR and BMI adjusted scan protocol independent of iodine concentrations of CM.MethodsThis study was conducted at Shandong Provincial Medical Imaging Institute,Jinan,China.We enrolled 270 consecutive participants who had been referred for CCTA for suspected coronary artery disease between February 2016 and October 2016.270 enrolled patients were randomly assigned into 3 groups(90 patients for each group)according to different CM concentrations.The three groups adopted the uniphasic CM protocol with fixed injection time of 15s followed by 30ml saline flush.lopromide 370(370mgl/100ml,Bayer Healthcare Co.,Ltd.),loversol 320(320mgl/100ml,Jiangsu Hengrui Medicine Co.,Ltd.,Lianyungang,Jiangsu,China)and 350(350mgl/100ml,Jiangsu Hengrui Medicine Co.,Ltd.)was used.CM volume and flow rate was adjusted according to the BSA,with volume of 31.5,33.3 and 36.5 ml per BSA,flow rate of 2.1,2.2 and 2.4 ml/s per BSA and fixed flow rate of 5ml/s.CM injection was timed by bolus tracking in a sample region of interest,the descending aorta,with the scan begun 10 s after exceeding a threshold of 100 Hounsfield units(HU).All studies were performed on a 2nd generation 128-slice DSCT system(SOMATOM Definition Flash,Siemens Healthcare,Forchheim,Germany).All scans were performed in a craniocaudal direction with prospective electrocardiogram(ECG)-gated protocol.The images were reconstructed with sinogram-affirmed iterative reconstruction(SAFIRE,Siemens Healthcare,Forchheim,Germany)algorithm using the corresponding vascular kernel(126f).The adjustable increment of strength 1 was used for adaptation of the noise model.Transverse images were reconstructed at 0.75 mm slice thickness with a 0.5 mm increment and in a matrix size of 512×512.All images were anonymized and transferred to an picture archiving and communicating system(PACS)(syngo MMWP VE 36A,Siemens Healthcare,Forchheim,Germany)for further image analysis.Two experienced observers,who were blind to the groups,evaluated the CTA images,independently.All statistical analysis was performed using SPSS software(SPSS v19.0,Chicago,ILL,USA).Quantitative variables were expressed as mean ±standard deviation(SD),and categorical variables were expressed as frequencies and percentages.Inter-group differences were evaluated by Welch's test,Mann-Whitney U test or independent-samples t test.P value<0.05 was considered statistically significant.ResultsThe basic characteristics of the subjectIn this study,270 patients were enrolled in this study,90 patients in each group were treated with traditional contrast agent regimen,body weight regimen and BSA regimen.There were no significant differences in gender,age,body weight,height,BMI,BSA,heart rate,blood pressure,history and risk factors among the three groups.Image quality evaluationThe CT of the iodophorol group was 21.14 ± 5.15HU,21.43 ± 5.22HU and 21.86 ± 5.31 HU,respectively,and the CT values of the ascending aorta were 473 ± 106HU,485 ± 102HU And 485 ± 131 HU,the RC values of RCA were 443 ± 116HU,453 ± 108HU and 446 ± 123HU,respectively.The CT values of LM were 476 ± 130HU,466 ± 119HU and 472 ± 139HU respectively,and the CT values of LAD were 457 ± 102HU,455 ± 89HU and 451 ± 93HU,respectively.The CT values of LCX were 429 ± 95HU,441 ± 82HU and 432 ± 113HU,respectively.There was no significant difference in the enhancement of noise,aorta,RCA,LM,LAD and LCX in the three groups.The image quality scores of the three groups were 4.16 ±0.73,4.13 ± 0.73 and 4.11 ± 0.74,respectively.There was no significant difference between the three groups.The amount of the contrast agent and the flow rateThe dosage of iodoprofen 370 group,iodophorol 350 group and iodophorol group were 56.98 ± 5.68ml,60.20 ± 5.19ml and 65.21 ± 5.21 ml,respectively.There was significant difference between the two groups(P<0.01).The flow rates of the three groups were 3.80 ± 0.38 ml/s,4.01 ± 0.35 ml/s and 4.35 ± 0.35 ml/s,respectively.There was significant difference between the three groups(P<0.01).The use of low concentrations of contrast agents requires more amount of contrast agent and faster flow rates,and the use of relatively high concentrations of contrast agents requires less contrast agent dosage and lower flow rates.Safety evaluationThere was no significant difference in radiation dose between the three groups(P>0.05).All subjects had no serious adverse reactions during the CCTA examination,including contrast agent allergies,contrast agent leakage,acute renal impairment,acute myocardial infarction,arrhythmia,organ embolism,vascular complications(bleeding,Embolization,etc.)and vasovagal reflexes.There was no significant difference between the three groups(P>0.05).ConclusionAs mentioned above,3 iodine concentrations of CMs(320mg/ml,350mg/ml and 370mg/ml)have similar efficacy and safety in CCTA.However,more large-scale,multinational,multicenter and prospective trials are warranted. |
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