| Perfusion is a important function that it help the blood flow transport its oxygen and nutrient substance to histiocyte through capillary network. Through measure the blood perfusion of part tissue. We can understand the change of haemodynamics and function. The normal physiologic function and various kinds of pathologic change of kidney have intimatic correlation with the blood change of tissue and organs. Among of it, single photo emit tomography(SPECT) is always a main method to gain the microcirculation information of renal tissue in vivo. Renal perfusion imaging is a dynamics can for select deck after the contrast agent was perfused into the vein clump. So gain time-density curve of every image element in this deck, and calculate every perfusion parameter with different mathematic model, to evaluate the perfusion condition of tissue and organs.The scanner time of CT perfusion imaging is short. The pictorial resolution are high. In space and time, it need not radioisotope, and influencing factors are little. It is a modus operandi to study the renal haemodynamics. In this stud-y, we utilize the 16 row spiral CT (produced by American GE company) and perfusion software to study the renal blood perfusion of animal experiment and clinical application. Analyze the influence of difference of every perfusion index in cortex and punctuate of two side renal. Meanwhile, at the foundation of ARF model by glycerine intramuscular method. Analyze the change of every perfusion index of renal failure, and contrast to pathology, on the foundation of imageology quantization analyze the change renal haemodynamics to evaluate the renal function.Material and method1. equipment and experimental animalsLight speed ultra 16 spiral CT (American GE company) Aw 4. 2 workstation perfusions softwareContrast agent (omnipaque 320mg I/ml ro wisipaque 270mg I/ml) Healthy rabbits, weight (2.5 ±0.5)kg, female or male Offered by Experimental Animal Center of Da Qing Oil Fiend Hospital Group.2. examination methodfixed the rabbit on the examination frame at dorsal decubitus, made vene-puncture at ear edge vein, and quickly injected contrast agent (2ml/kg). Each time selected one side of renal perfusion scanning.Clinical examination patients lied on their backs. Firstly, according to the normal procedure plainly scanned two-side kidneys. Used No. 8 trocar and high pressure syringe to inject contrast agent quickly through the vein in the front of elbow (dosage was 0. 65ml/kg, injection speed was 3. 5ml/s). Selected renal hilum area level as scanning deck.3. experiment study of renal perfusion36 healthy rabbits were divided into A group, B group and C group randomly. Each group were 12 rabbits. Injection flow were lml/s, 2ml/s and 3ml/s respectively.4. Renal failure animal model establishment and perfusion imaging40 healthy rabbits were determined urine protein with chromatometry within one week, drew the blood to measure the BUN and Cr, and made renal perfusion scanning. Injection flow was 2ml/s. After scanned, glycerol already preparation were injected into the back leg intramuscular of rabbits (lOml/kg). In order to increased glyceric toxicity, before within 12 hour muscular injected, drinking water amount was limited. Determined the urine protein level after injected drugs at 24, 48, 72, 96 hour, drew blood to check BUN and Cr. Made renal perfusion scanning by CT at every time stage respectively. 6 experimentalrabbits naturally died in the time of experiment. Killed one rabbit at every time stage to make pathology examination.5. clinical application of renal perfusion imaging by MSCTNormal group had 32 cases, 18 cases were men, 14 cases were women. One side nephrectomy 12 cases (1-3. 5year) , age 23 ~68. (contrast agent was omnipaque and checker had normal renal function and routine urianlysis within one week). Renal failure group were 25 cases , 18 cases were men, 7 cases were women ( urine pr > 0. 2g/L, blood BUN > 20mmol/L, Cr > 700umol/L within one week, the contrast agent was wisipague).6. programming and scanning techniqueFirstly, routinely made two-side renal plain scan, layer thickness was 5 mm, layer distance was 5mm. Scanning speed should be at least 0. 8s/layer. Perfusion scanning adopted Cine Full mode. After 5 second, the contrast agent were injected, begin scan, all scanned 50 second in one second interval. The first pass picture of dynamic image acted as the first pass image, made it as a standard image. At first-pass and after first-pass of contrast agent made the dynamic image at identical deck.7. Postprocessing of renal tissue perfusionScanning data were transmitted to workstation ( AW 4.2) and analyzed perfusion image. Selected region of interest (ROI) about 7.5mm , gained TDC of ROI. Meanwhile got BF, BV, MTT, PS and false color function image of corresponding perfusion station. Got the renal relative priming volume by TDC calculation , strengthening peak time ( PT) , CT value rising time ( RT) , peak CT value (PV) , CT value amplification (RV) and relative strengthening (ED). In order to avoid the error, made "X" type 4 spot ROI measurement and got average value.8. Statistics analysisStatistical treatment made SPSS 11.5 software, the result took the average value of measurement value, made non-matched-pairs t test and variance test.Result1. In the same renal cortex and medulla, BF, BV, PS, PT, RT, PV all had significant difference besides MTT (P < 0. 01). Along with the increasing of injection flow of every group from lml/s to 3ml/s, BF, BV and PS of renal cortex also increased, but MTT had not obviously change. PT and RT decreased, PV significantly increased. Injection flow increased three time, PV about elevated 13 percent, but the change of BF, BV and MTT et al were not obvious in medullary , PV increased only 5 percent.2. Renal perfusion parameter of ARF animal modeContrast to pro-injection, every renal functional parameter value were significantly increased after 1 ~3day intramuscular glycerol (P <0. 01). BF and BV decreased, MTT increased ( P < 0. 01 ). reaching peak time prolonged, peak value decreased.3. Histomorphology change of ARF animal modeKidney swelled, renal amicula very tensed, bleeding point saw in the cut surface. At optical microscope, the structure of nephric tubule and interstition were severity damage, a lots of renal tubular epithelial cell necrosis. Lumens collapsed and expanded, protein cast appeared, glomerulus injury was relative light. At electron microscope, glomerular mesangium and endothelium hyper-plasia and swell. Pykno-materials deposit between basal lamina and splanchno-derm epithelium, epithelium foot process confluence, vanish, basal lamina thic-king and break. Edge of it become irregular. These changes are same as the ARF pathology characteristic.4. The same perfusion index of two-side renal cortex were not significant difference (P > 0. 05). Also in medullary (P > 0.05). Besides MTT, the same perfusion parameter of the same side renal cortex and medullary, all had significant difference (P <0.01). 12 cases one side nephrectomy, perfusion index of uninjured side ren besides MTT and PT decrease, the others significantly increase. At renal failure, renal flow decrease, BF, BV and PV decrease, MTT and PT increase. Especially medullarenis change were obvious.DiscussionIt has many methods to determinate the renal blood perfusion, and radioactive nuclide method is always a main one. Its defect is that the size of seeker granule influence computation. Miles et al thought that radioactivity contrast a-gent infused by vein had identical pharmacokinetics of radiotracer. Meanwhile determined the reliability of CT measure for renal flow.CT perfusion imaging is a functional imaging, gained TDC by perfusion software, which reflect the concentration change of contrast agent in this organ, and the change of iodine aggregation quantity, thereby indirectly reflect the change of tissue perfusion volume. TDC in normal renal perfusion has a steep rising stage, high ridge, the TDC of two-side ren are basic similar, reaching peak time and strengthening peak value are symmetry.The kidney is a comparatively large volume, parenchy matoas and symmetry organ, blood flow is abundance, unlike liver, blood supply is not multiplicity. Respiratory movement has little influence on it. It very fit to do CT perfusion imaging. But the difference of contrast agent injection flow may result in a certain difference of results. Haemodynamics effect of iodine would influence the accuracy of renal blood flow. The date showed, when the contrast agent were injected into the artery, the increment of incipient renal blood flow would reach 19% -35% , then gradually decrease to normal condition, the contrast agent dosage of CT perfusion is small, it caused a little change. Bell et al thought that the more little of contrast agent use the more accuracy of BF value, but if contrast agents are too little to gain favorable signal-noise ratio after enhancement scanning , thus it would influence the results. The speed of clump perfusion is very fast, although it can elevate the accuracy rating of calculation, it increase the chanciness of contrast agent exosmosis and cardiac burden. In this experiment , when the change of contrast agent injection flow are not very big, it can cause a little influence on the change of every perfusion index in the renal cortex and medullary, but when the injection flow elevate two fold, it will significantly influence the change of every perfusion index, especially the correspondenceoerfusion parameter, for this reason, when make a measurement and comparison )f multilayer CT renal peifusion, we should consider the factor of injection flow. Blomly et al study showed, when the injection flow increase from 5ml/s toOml/s, CT peak value would increase about 8 percent. It close to our part experimental results.As the isotonic contrast agent become popular, the iodine which used for ;trengthening will cause little influence on the renal parachyma perfusion. It is 'ery important to carefully designate ROI, ROI must as far as possible great, in >rder to decrease quantum noise, but we should as far as possible away from the tincture of cortex and medulla, as have a determination distance with the pe-iphery part of tissue and organ, decrease influence of volume effect, avoid the nterference to perfusion parameter.In the animal experiment and clinical application we find that there is no 'bvious difference in the cortex or medulla BF, BV, MTT and PS of two-side :idneys. However, the BF, BV and PS value in the same side kidney is obvi->usiy higher than that of medulla, MTT has no obvious change because the renal ortex is made up of glomerulus with dense vessels and abundant blood flow, /hile the renal medulla is mainly made up of renal tubules with fewer vessels, lowever, the PT and RT values of renal medulla are obviously longer than those f cortex in the same side, while PV, RV and ED values of renal medulla are ower than those of cortex. This mainly because the medulla contains little lood, then the enhancement degree of the contrast medium is relatively low and le enhancement speed is slow. If one-side kidney is ablated, the BF, PV and ,D of cortex and medulla will increase, while MTT will shorten obviously in the pposite kidney. This indicates that if one-side kidney is ablated, the functions f the healthy kidney will be increased to compensate the ablated one. At renal lilure, renal ischemia and nephrotoxin cause the release of vasoactive sub-:artce, make vessel of kidney to contract, effective filtration pressure of renal lornerulus decrease, renal blood flow perfusion decrease, BF and BV decrease, T prolong, PV decrease. Moreover, because of the obstruct of renal tubule, lood become bracly, stasis, so that MTT increase, the change is obvious espe-ally medullarenis. ARF animal modes are very fit to make a experimental stud-y of CT perfusion, when the glucerol was injected into muscle about 12 hours, the pathology change of ren become appear, at 72 hours, the pathology changes are most severity, BUN and Cr levels one after another reach peak afterward get into recovery condition, so we select ARF of 72 hours as a model. Majority of ARF are reversibility, it has a obvious difference to irreversibility of chronic renal failure, so early understand the pathology change and microcirculation change of ARF, it can offer a important information to evaluate and treat ARF.When a great quantity of glucerol are injected into muscle, it will cause sarcolysis and haemolysis, release a great myohemoglobin and hemoglobin, and aggregate to form cast to obstruct renal tubule, result in injury of renal tubule and mesenchyme. In addition, myohemoglobin and hemoglobin all can resolve into hematosin (endogenous) , injury renal tubular cell. Both can cause afferent , efferent of arteriole of glomerulus to contract, result in the decrease of glomer-ulur filtration. Renal blood flow perfusion obviously decrease, many perfusion index acquired decrease follow. Moreover, along with the ARF aggravate, the change of each CT perfusion index become more and more obvious, the change in medullorenis is significant than that of cortex. Miles et al study had proved this point.The determination of renocortical blood flow priming volume is an important index of judgement of renal blood flow, the priming volume in normal cortex are significantly high than that of ischemia cortex. At present, the renal ischemia in one side is judged mainly by comparing the blood flow in the opposite renal cortex. If the blood flow in one-side renal cortex is less than 25% , renal ischemia may exist there. One of the advantages of this method is the difference in individual circulation is reduced and the percentage is comparable in certain degree. However, the judgment on renal ischemia of two-side kidneys lacks of objective index. Measurement of perfusion blood in renal cortex is the direct index for judging renal blood. In many pathological conditions like shock, the blood flow in renal cortex and medulla will distribute again. At present, many experimental researches on perfusion are under developing in this field.The MSCT can quickly trace the time when the contrast medium passes renal circulation for the first time, which will bring several hemodynamic data. 3D...
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