Improvement Of Technique Parameters And Clinical Application Of CT Perfusion In The Diagnosis Of Solitary Pulmonary Nodule

【BACKGROUD】Ever since the CT perfusion technique came into being,researchers did a lot of work on the parameters of this technique and made certain corresponding progress.In 1995,Swensen adopted the following protocol:scanned every 30 seconds after injection of the contrast agent and 6 times in all which took 3 minutes.In 1996 and 2000,Swensen changed his former protocol:scanned once every minute and 4 times in all.Chin adopted a new plan:scanned once every 20seconds and 9 times in all.Miles adopted the following plan:scanned once every 3 seconds for the first 30 seconds and 10 times in all.Zhang took the following parameters:5.6 second delay after contrast agent injection;once every second and 40 times in all.Although different researcher took different protocols,time interval always kept within 3 seconds.With the development of CT,studies at present are all apt to take the sequence of one scanning every one second, delay time 0～15 seconds and time period 30～40 second.In addition,speed of contrast agent injection is one of the focus we pay much attention to which is related to mathematic model.Nowadays,mathematic models for CT perfusion includes two main kinds:deconvolution and non-deconvolution model.The former allowed relatively low injection speed and 4-5 ml/s may be applied in clinical work while the latter required a higher speed.To some extent,it could reach 10 ml/s or 20 ml/s.Thus,special work should be done.In the diagnosis and differential diagnosis with CT perfusion for solitary pulmonary nodules,Zhang took her work with 65 cases of SPN.All cases were divided into three groups as malignant SPN(primary and metastasis),benign SPN(granuloma, tuberculoma,hamartoma,bronchial cysts) and inflammatory SPN(pneumonia, tuberculosis).Take measures of the following parameters as peak value of SPN, SPN/aorta and perfusion value of SPN respectively.The results showed that peak value of SPN,SPN/aorta and perfusion value of malignant and inflammatory SPNs were higher than those of benign SPNs while there was no obvious difference between malignant and inflammatory SPNs.Bai and Wang performed CT perfusion on 34 SPNs and got similar results with Zhang's.To sum up,we can draw conclusions that there are still some issues to be solved.Firstly, CT perfusion technique in its early stage showed an average perfusion of an organ of lesion.Thus it had a relatively further relationship with its pathological changes.Secondly, X-ray dose in this examination kept high which was several times higher than that of conventional CT scan and in tum become a obstruction.Thirdly,patients were required to hold his or her breath for 30-40 seconds which was rather difficult.Fourthly,different mathematical model used for CT perfusion software required different CT contrast agent injection speed which turned out to be another obstruction in its clinical application.Lastly, different SPNs with different CT perfusion parameters are to be discussed in a further way.【OBJECTIVE】67 cases of SPNs were included in the research for CT perfusion.Adjustment and of parameters of the technique as scanning time,time interval and injection speed were performed and evaluation of their effect on 64-detetors CT perfusion were done simutinuously.To evaluate the clinical application of CT perfusion in SPN diagnosis and differential diagnosis and its limitation..【MATERIALS AND METHODS】Critiria for cases:1,SPNs detected on X-ray or CT examination for the first time without any therapy.2,diameter of SPN was not more than 3cm.difinition of diameter is: mean value of three direction in MPR in mediastinal window.3,No alergical reaction.4, Able to cooperate with the scanning with the help of breath training.General materials:67 patients with SPNs(diameter≤3cm;50 maliagnant nodules;10 active inflammatory nodules:7 benign nodules) during 2005/12-2008/02 that underwent perfusion CT scanning were included in the study.male 41 cases,female 26 cases.Age ranges from 28-73 years which on average was 56.02±9.11 years.Among all the cases,43 cases got pathological evidence after operation;2 cases were proved by pathology by CT·guided percutaneous transthoracic biopsy,one case got pathological evidence wth fiberoptic bronchoscopy.Matastasis were found in 4 cases,among 7 benign SPNs,one case were proved with post-operation pathological evidence while the rest were followed up more than 2 years withour any change.10 cases of inflammantory SPNs were all cured with antiinflammatory therapy.Case division:1,on contrast agent injection speed.Different mathematical model require different injection speed.Deconvolation model was the one we apply in the study. In previous studies,most domestic authors adopted a speed of 4-5ml/s which served well in part of the cases.However,according to the writer,such speed was still hard to accept in some cases and in tum they had to give up CT perfusion examination.Meantime,too low injection speed may lead to low perfusion in SPN.Based on the above,we had two groups for different injection speed:3ml/s and 5ml/s.2,On scanning time.CT first pass perfusion require certain scanning time.At the same time,patients' ability to hold their breath is also a vital factor in the CT perfusion.So sanning time is an important factor.Normal time for circulation is 20～25 seconds.So scanning time should be restricted within this time to aviod reperfusion.23 seconds,25 seconds and 30 seconds were the parameters we had in the study.3,On time interval.X-ray dose has always been a focus.Time is one of the importatn factor related to it.In this study,time interval of 1,2 seconds were adopted and thus X-ray dose reduced cortresponding by 1/2 and 1/3 compared with no time interval.4,On different property.Differential diagnosis has been a problem in clinical work. Different properties of SPNs were divided into three groups as malignant,benign and inflammtory SPNs.Data process:1.In part one,caculate BF,BV,MTT and PS respectively of two groups of different injection speed as the parameters in evaluation of the SPNs.And t analysis was performed.2,In part two,caculate BF,BV,MTT and PS respectively of different groups of scanning time as the parameters in evaluation of the SPNs.And repeated measument analysis was performed.3,In part three,caculate BF,BV,MTT and PS respectively of different groups of time interval as the parameters in evaluation of the SPNs.And repeated measument analysis was performed.4.In part four,caculate BF,BV,MTT and PS respectively of three groups of properties as the parameters in evaluation of the SPNs.And t analysis was performed to evaluate the clinical application of CT perfusion.【RESULTS】1,For injection speed 3ml/s,average blood flow for malignant SPNs is 49.006±42.429 ml.100g^-1.min^-1;average blood volume is 3.358±4.608 ml/100g;average mean transit time is 6.307±3.772 seconds;average permailty surface is 9.378±9.040 ml.100g^-1.min^-1;For injection speed 5ml/s,average blood flow for malignant SPNs is 52.917±61.206 ml.100g^-1.min^-1;average blood volume is 3.045±4.671 ml/100g; average mean transit time is 6.079±3.831 seconds;average permailty surface is 8.142±7.082 ml.100g^-1.min^-1.Statistical difference were eveluated between two groups with t analysis:blood volume p=0.249＞0.05;blood volume p=0.737＞0.05;mean transit time p=0.776＞0.05;permailty surface p=0.454＞0.05.Four parameters were all higher than 0.05 which showed that there was no statistial differece between different injection speed in CT perfusion for SPNs.2,For scanning time 23 seconds,average blood flow for malignant SPNs is 55.531±55.870 ml.100g^-1.min^-1;average blood volume is 3.361±2.799 ml/100g; average mean transit time is 5.323±2.961seconds;average permailty surface is 8.980±9.454 ml.100g^-1.min^-1;For scanning time 25 seconds,average blood flow for malignant SPNs is 61.100±75.785 ml.100g^-1.min^-1;average blood volume is 3.354±2.636ml/100g;average mean transit time is 5.651±3.140seconds;average permailty surface is 8.367±7.854 ml.100g^-1.min^-1;For scanning time 30 seconds,average blood flow for malignant SPNs is 52.917±61.206 ml.100g^-1.min^-1;average blood volume is 3.524±4.564 ml/100g;average mean transit time is 6.249±3.545seconds;average permailty surface is 8.864±8.627ml.100g^-1.min^-1.Statistical difference were eveluated between three groups with repeated measurement analysis:blood volume p=0.937＞0.05;blood volume p=0.617＞0.05; mean transit time p=0.111＞0.05;permailty surface p=0.906＞0.05.Four parameters were all higher than 0.05 which showed that there was no statistial differece between different scanning time in the above three groups in CT perfusion for SPNs.3,For no time interval,average blood flow for malignant SPNs is 52.917±61.206ml.100g^-1.min^-1;average blood volume is 3.524±4.564 ml/100g;average mean transit time is6.249±3.545seconds;average permailty surface is 8.864±8.627 ml.100g^-1.min^-1;For 1 second time interval,average blood flow for malignant SPNs is 41.461±20.312 ml.100g^-1.min^-1;average blood volume is 3.579±3.106ml/100g; average mean transit time is 5.560±3.522 seconds;average permailty surface is 10.886±10.248 ml.100g^-1.min^-1;For 2 seconds time interval,average blood flow for malignant SPNs is 4.487±5.429 ml.100g^-1.min^-1;average blood volume is 3.524±4.564 ml/100g;average mean transit time is 6.451±3.817 seconds;average permailty surface is 9.319±8.857 ml.100g^-1.min^-1.Statistical difference were eveluated between three groups with repeated measurement analysis:blood volume p=0.001＜0.05;blood volume p=0.286＞0.05; mean transit time p=0.116＞0.05;permailty surface p=0.504＞0.05.For blood flow,it is statistically different while for the rest three,parameters were all higher than 0.05.So to sum up,there was statistial differece between different time interval in the above three groups in CT perfusion for SPNs.4,In solitary pulmonary nodules with different properties,average blood flow for malignant SPNs is 52.9±61.2607 ml.100g^-1.min^-1;average blood volume is 3.579±3.106 ml/100g;average mean transit time is 6.249±3.545 seconds;average permailty surface is 8.864±8.627 ml.100g^-1.min^-1;average blood flow for benign SPNs is 41.461±20.312 ml.100g^-1.min^-1;average blood volume is 3.579±3.106ml/100g; average mean transit time is 5.560±3.522 seconds;average permailty surface is 10.886±10.248 ml.100g^-1.min^-1;average blood flow for inflammantory SPNs is 74.283±69.258 ml.100g^-1.min^-1;average blood volume is 4.487±5.429 ml/100g;average mean transit time is 6.451±3.817 seconds;average permailty surface is 9.319±8.857 ml.100g^-1.min^-1.Statistical difference were eveluated between malignant and benign SPNs with t analysis:blood volume p=0.256＞0.05;blood volume p=0.439＞0.05;mean transit time p=0.763＞0.05;P value of the three parameters above were all higher than 0.05. Permailty surface p=0.009＜0.05.P value of permailty surfacewas less than 0.05.So to sum up,there was statistial differece between malignant and benign SPNs in CT perfusion..Statistical difference were eveluated between malignant and inflammantory SPNs with t analysis:blood volume p=0.318＞0.05;blood volume p=0.953＞0.05;mean transit time p=0.348＞0.05;permailty surface p=0.274＞0.05.P value of all the four parameters were all higher than 0.05.So to sum up,there was statistial differece between malignant and inflammtory SPNs in CT perfusion.Statistical difference were eveluated between inflammatory and benign SPNs with t analysis:blood volume p=0.003＜0.05;P value of blood volumewas less than 0.05.blood volume p=0.306＞0.05;mean transit time p=0.205＞0.05;permailty surface p=0.274＞0.05.P value of parameters above were all higher than 0.05.So to sum up, there was statistial differece between malignant and benign SPNs in CT perfusion.【CONCLUSION】1,In application of 64-row CT perfusion in SPNs diagnosis,there is no difference in using different contrast agent injection speed as 3ml/s and 5ml/s,so 3ml/s is recommanded in clinical application. 2,In application of 64-row CT perfusion in SPNs diagnosis,there is no difference in using different scanning time as 23s,25s and 30s,so 23s is recommanded in clinical application.3,There is statistical differece in Blood Flow between different time interval,so scanning with no time intereval is recommanded in 64-row CT perfusion to guarantee its clinical significance.4,64-row CT perfusion is of help in diagnosis and differential diagnosis of SPNs, and some limitations still exists.