The Study Of Dual-source CT Perfusion Imaging And Pathologic Basis In The Early Diagnosis Of Radiation-induced Lung Injury

PartⅠ clinical significance of early detection of radiation-induced lunginjury with dual-source CT perfusion imagingObjectives: It’s hard to make an early diagnosis due to the delayed morphologicalchanges using conventional imaging in the detection of radiation-induced lung injury(RILI) after thoracic radiotherapy. As to the issue, can thoracic functional imagingdeliver the earlier functional changes of RILI than traditional imaging? This studyapplies pulmonary perfusion imaging (CT perfusion imaging, CTPI) with dual-sourceCT (DSCT) scanner to explore the feasibility of the early diagnosis of RILI and itsclinical value.Methods: As the Control Group,20cases, age47-76(10males,10females) wereselected from the negative patients who were suspected with pulmonary embolism ruledout by the results of4D-DSCT enhancement imaging and clinical diagnosis.48patients,aged43-70(27males and21females) with postoperative radiotherapy with upperesophageal cancer or thymic tumor (irradiation dose of total, ie DT,60Gy) wereselected as Test Group. CTPI with detection of tumor necrosis factor (TNF alpha) andtransforming growth factor (TGF-beta1) in peripheral blood, were performed beforeradiotherapy and at1/2DT time point (30Gy). Serum levels of cytokines, conventionalCT manifestations and CTPI perfusion values [relative blood flow (rrBF), relative bloodvolume (rrBV), relative blood capillary permeability surface (rrPS)] were compared andanalized between patients with RILI (group A) and non-RILI (group B). Using Siemensnew dual-source CT machine (FLASH)4-D lung volume scanning technology as CTP imaging method, routine high resolution CT scan (HRCT) was first performed thenperfusion imaging.Results:⑴In all subjects of Control Group, the satisfactory CTP images wereproduced with nice layers and structures. Stable data could be gained from eachdifferent size of ROIs in lung field; The normal pulmonary BF, BV and PS were149.3±18.3mL/100mL/min,14.86±2.65mL/100mL,9.54±2.91mL/100mL/min,respectively; there was no significant difference between the genders or the bilateralsides for all the above parameters obtained (P>0.05); there was significant difference,for BF and BV, between the superior and inferior lung fields（P <0.05）and nosignificant difference for all perfusion parmeters, between superior and middle ormiddle and inferior fields (P>0.05).⑵18cases (18/48) of ARILI were diagnosed. Thediffereces of TNF-α and TGF-β1pre-and post-radiotherapy were not significant inGroup A(P>0.05), but there was positive sign of conventional CT in two cases. Themean values of rrBF, rrBV and rrPS (relative regional blood flow, volume andpermeability surface, respectively) of post-radiation in Group A were correspondinglyhigher than those of pre-radiation(each P <0.05); the rrBF and rrBV of post-radiationfrom Group B were significantly higher than those of pre-radiation (each P<0.05), butno obviously change for rrPS (P>0.05). There were significant differences for allperfusion values detected pre-and post-radiation from radiation lung fields betweenGroup A and B (each P <0.05). Applying the diagnostic threshold value of rrPS=1.22,the sensitivity, specificity, positive and negative predictive values of CTPI (88.9%,90.0%) for early diagnosis of ARILI were better than those of CT (11.1%,90.0%;χ2=13.61, P <0.05).⑶There were no significant differences for all correspondingperfusion values of pre-radiation between control and test groups.Conclusions:⑴Dual-source CTPI may apply in the study of pulmonary perfusionimaging via providing the quantitative analysis of pulmonary hemodynamic parameters,such as rBF, rBV, rPS, etc.⑵TNF-α, TGF-β1of peripheral blood may not yield apositive value for early diagnosis of RILI in patients with radiotherapy.⑶Values ofCTPI parameters may reflect the hemodynamic changes of post-irradiation lung,yielding a promising value in early diagnosing ARILI. PartⅡ Establishment and appreciation of ladder model ofradiation-induced lung injury in rabbits1. Preparation method of the ladder model of RILI in rabbitsObjective: For human RILI, it is difficult to accurately control each phase of RILIand to perform repeatable study of biochemistry, imaging and histopathology. Therefore,to establish a suitable for dynamic observation and research of animal model is verynecessary.This study was to explore the preparation method of the ladder model of RILIin rabbits.Methods: Fifty-four healthy New Zealand rabbits were randomly divided intothree groups: A, B, and C (18rabbits for each group). the same hybrid methodanesthetic technique was used by the same anesthetist in the three groups, that is, thefirst muscle injection of diazepam (the dosage is0.8-1.0mL/kg), then intramuscularinjection of Su-Mian-Xin II (the dosage is0.4-0.5mL/kg), and then underwenthigh-energy X-ray irradiation in unilateral single lung after fixed by the homemademedium animal medical imaging scanning bed. The irradiation dose of total was35,25and15Gy, respectively. Conventional CT observation was performed at ladder timepoints (1,2,3,4,5,6,8,12,16,20,24weeks) of post-radiation, including the safetyand efficacy of hybrid anesthesia method, comparison of time of CT positive expressionand total mortality of each model.Results:⑴The anesthesia efficacy in three groups of model were all remarkablewith unconscious time of anesthesia for an average ranging from30to40minutes, andzero anesthesia mortality.⑵exudative ground-glass appearance of peak time inconventional CT was2w,4w,16w, respectively for A, B, C groups, which wereconfirmed by further study in the following ladder time points, namely the generation ofRILI. Model deaths during the test were4,1,1, respectively, that is, the correspondingmortality rates were22.2%,5.6%and5.6%, respectively.Conclusions: Hybrid method anesthetic technique may provide such advantages ashigh security, good repeatability, strong controllability, easy operation, etc. Group B (25 Gy) with the advantages of moderate model-building time, lower mortality rate, theladder symmetry, facilitates further RILI analysis at ladder time points, and is thepreferred method of model building.2. Appreciation of ladder model of radiation-induced lung injury in rabbitsObjective: In clinic, the evolution process of occurrence and development of RILIis relatively complex, and the periods or phases of RILI have no obvious dividing line.So the dynamic observation and identification of animal models of RILI were yieldingan important clinical significance.This study was to explore dynamic serological andhistopathologic evaluation in rabbit model of RILI in order to determine the occurrenceand evolution process at ladder time points.Method: Using the above25Gy model-building method and the ditto anesthesiamethod, a total of60healthy New Zealand white rabbit, set as the experimental group,underwent unilateral single lung irradiation with high-energy X-ray exposure. At thesame time, as for the control group, the random batch of36white rabbits performedwith a sham-irradiation. According to the following time points of post-irradiation,12subgroups were divided and5and3rabbits for each subgroup in experiment and controlgroup, respectively. Extraction of4to8mL whole blood for serological detection viaheart puncture after thoracic open at the such ladder time points as1,6,12,24,48,72hours and1,2,4,8,16,24weeks after exposure, then6specimens were taken fromsuperior, middle and inferior field of bilateral lungs. Afterwards, the pathologicalchanges were observed with light and electron microscopies; the expression of TNF-aand TGF-β1in local lung tissue was detected by immunohistochemistry. During theobservation of models, a new individual was added to supplement if there was modeldeath.Result:⑴In experimental group, two died at2w,8w after irradiation,respectively, the total mortality in the experimental cycle was3.3%.⑵RILI occured inall rabbits of test group: at early stage, it’s characterized by acute inflammatory reaction;it featured the progressing fibrosis at later stage.⑶Regarding expression of TNF-a andTGF-β1after1st and48th of postirradiation, respectively, there were statistically difference between test and control groups (each P <0.05).⑷In terms of the aspects ofthickness of alveolar wall, density of pulmonary interstitium (after1st ofpostirradiation), amount of fibroblast and fibrocyte from interstitium (after24th ofpostirradiation), there were statistically difference between two groups (each P <0.05),and test group correlated well with the time of post-irradiation (r=0.82086,0.87181,0.68230; each P <0.05).⑸There was statistically difference among the relative amountof collagen fibers at time points of post-irradiation in test group (F=100.31, P=0.000),while no difference in control group (F=1.00, P=0.450). As to the relative amount ofcollagen fibers after48th of postirradiation, test group differs from control groupsstatistically (each P <0.05), correlating well with the time of post-irradiation(r=0.99318, P=0.0000).Conclusion: Stable and reliable ladder model of RILI in rabbits was made throughsingle fraction irradiation in whole unilateral lung with25Gy of high-energy X-rays,which may simulate the occurrence and development of evolution of RILI. Cytokinesmay be taken as a certain reference, but cannot be used as the basis for diagnosis orprediction.Part Ⅲ The study of technique of functional imaging in ladder modelof RILI in rabbitsObjective: To explore the feasibility of the technological parameters andquantitative analysis of CT perfusion imaging (CTPI) in healthy New Zealand whiterabbits.Method: Thirty-six healthy New Zealand rabbits (18, each gender) wereperformed with the same hybrid method anesthetic technique by the same anesthetist,that is, the first muscle injection of diazepam (the dosage is0.8-1.0mL/kg), thenintramuscular injection of Su-Mian-Xin II (the dosage is0.4-0.5mL/kg), and thenunderwent sham-irradiation in unilateral single lung after fixed by the homemademedium animal medical imaging scanning bed. Conventional CT (HRCT) and CTperfusion imaging (CTPI) were performed at ladder time points (1,6,12,24,48,72hours and1,2,4,8,12,16,24weeks) after sham-radiation. CTPI were performed by theequipment of Siemens new dual-source CT machine (FLASH), using the whole lung4-D volume dynamic scanning technology. Scan parameters: the tube voltage100kv,automatically adjust the tube current;4-D1.5s mode; total5mL of non-ionic contrastmedium (300mg I/mL), with injection rate0.8mL/s. Special animal breathing machinewas adopted for with15s apnea during CTPI.Result: In all subjects, the satisfactory CT perfusion images were produced withnice layers and well structures. Stable data could be measured from each different sizeof ROIs in lung fields. For healthy adult rabbits, the normal pulmonary BF, BV and PSwere23.8±25.9mL/100mL/min,13.04±2.07mL/100mL,8.97±2.14mL/100mL/min,respectively; there was no significant difference between the genders or the bilateralsides for all the above obtained parameters (P>0.05); there was significant difference,for BF and BV, between the superior and inferior lung fields （P <0.05）. Aftersham-radiation, each corresponding perfusion values at different time points deliver agood repeatability, and the CTPI parameters at each time point had no obviousdifferences with no statistical significance (each P>0.05).Conclusion: For normal adult rabbits, CTPI parameters in lungs can bequantitatively measured and analized with a good repeatability, and the similar changerule to that of the human lungs.Part Ⅳ Experimental study of early diagnosis for RILI withdual-source CT perfusion imagingObjective: To study of the hemodynamic change rules of ladder model of RILI inrabbit using whole lung CT perfusion imaging (CTPI) in order to explore the value ofearly diagnosis of RILI and its pathological basis in the development and process of thedisease.Method: Seventy-two healthy New Zealand rabbits were randomly divided intotwo groups:36rabbits in test group were administered with25Gy of single fractionatedirradiation in the whole unilateral lung; the other36rabbits in control group were sham-irradiated. According to the post-radiation time points (1,6,12,24,48,72h and1,2,4,8,16,24w, respectively), the test and control groups were divided into twelvesub-groups, respectively. All rabbits were respectively performed with conventional CT,CTPI and ultimately sacrificed at the different time points (1,6,12,24,48,72h, and1,2,4,8,16,24w) after irradiation. The pathological changes were observed with lightand electron microscopies; the expression of TNF-a and TGF-β1was detected byimmunohistochemistry. t-test, chi-square test and linear correlation analysis wereapplied in the comparison of results of CTPI, pathologic observed values between testand control groups.Result:⑴The changes of CTPI parameters from control group after irradiationwere relatively stable, but those of test group demonstrated a pattern ofdropping-rising-dropping in rBF, rBVand rPS with a significant difference from thoseof pre-radiation (t=2.90-6.37, each P <0.05): first, temporally dropping at1to12hours after irradiation, then strikingly rising (much higher than those of control group)to the peak at72hours to2weeks; lastly gradually falling down to the nadir (muchlower than those of control group) at24weeks.⑵In test group, capillary endothelialcells, basement membrane and alveolar epithelial cells, as the main injured targets,showed certain alterations in pathology. There was a significant correlation between thechanges of CTPI parameters (rBF and rBV) and pathohistology in control group (r=0.74,0.83; P=0.006,0.000), with the dependent relationship between rPS and the amounts ofRBC outside the capillary and the destruction of basement membrane (r=0.87,0.88; P=0.000,0.000).⑶The detection rate of RILI with CTPI was obviously higher than thatwith HRCT (χ2=4.37; P=0.036). According to ROC curve, the sensitivity andspecificity of CTPI and conventional CT for diagnosis of RILI were92.3%,92.3%and69.2%,90.0%, respectively (Z=13.06, P <0.05), denoting that CTPI diagnosticefficiency is superior to conventional CT, especially in the early stages of RILI model(4weeks after radiotherapy).Conclusion: CTPI parameters are able to reveal the rule of hemodynamic processand reflect the pathophysiologic state of different stages of RILI. By the time ofdetecting RILI, the detection rate of CTPI was clearly superior to that of HRCT, which yields potential value in predicting RILI.