|
For the benefit of free from invasiveness and irradiation exposure, many efforts tried to evaluate kidney with ultrasound. With built integral functions as 2-D gray scale image, we can measure renal size, that is not sensitive to renal function; furthermore the change in renal size is a late indicator of poor renal function. Using duplex Doppler to check resistance index (RI) and pulsatile index (PI) is another available built function of Doppler ultrasound. In evaluation of renal transplant, the RI value is mandatory. From a physical aspect, however, RI is not well-understood despites it is so popular applied. The usefulness of the ultrasonographic measurement of resistive index is not yet fully recognized. The current consensus of RI is its stand for vascular resistance. Moreover, the range of RI value varied widely, without definite cutoff point. So, mean RI is a more convincing data to be analyzed. With introduction of color duplex sonography that has been available in 1986 and power Doppler image later in 1993, we have more realistic tools to evaluate renal cortex perfusion. Color duplex sonography, also referred to as color flow mapping, or technically not quite correct color Doppler, has become an essential modality in medical diagnosis imaging. Most color Doppler technique as based on the estimation of the mean Doppler frequency shift. Some efforts tried to improve perfusion detection by color duplex Doppler and detect renal perfusion by contrast-enhanced harmonics ultrasound images. Although color Doppler ultrasound with harmonics function seems to have a good correlation with renal cortex perfusion, the preparation and injection of contrast medium diminishes the characteristics of ultrasound--non-invasive and easily available. The power Doppler technique, also called color Doppler energy image, bases on estimating the integrated Doppler power spectrum. The power Doppler image, however, is superior to color Doppler index in the demonstration of the normal intrarenal vasculature. We can even see the cortical brush resulting from visualization of small vessels at their branches distal to the arcuate arteries. Studies graded the perfusion of the renal cortex by power Doppler, no matter 6 or 3 grades, among adult or children, there were no correlation with renal function. No matter the superiority of renal cortex perfusion detection ability, Hilborn made a conclusion that objective analysis of the power Doppler sonographic appearance of renal transplants does not appear to aid in their evaluations(Michel C, 1999) . The studies about vascular impedance aid another way to evaluate the kidney. Impedance is calculated by the ratio between pressure and flow at difference frequencies. Prior to 1955 there were only sporadic attempts to analyze the arterial pulse in the frequency domain. The conventional study, conducted by Hamilton, Remington, and their colleagues, was to analyze fluctuation in wave contour in time domain, not to involve in frequencies. In 1955, the physiologist McDonald and the mathematician Womersley first published the relationship between pulsatile pressure and flow in a vascular segment. This was based completely on the concepts that the arterial system being in a steady state of oscillation and pressure-flow relationship were obtained through Fourier analysis of recorded pulses. The non-linearitics in pressure-flow relationship were insufficiently small to be neglected at a first approximation. Taylor, working with McDonald in the same laboratory, showed that impedance patterns could be used to characterize the properties of the vascular bed downstream from a recording site, especially with regard to pulse-wave reflection. At the difference properties and position of vascular trees, the impedance works quite different from others. Analysis of vascular contour fluctuation was feasible because the reflection of vascular bed was the most important contribution to fluctuation in wave contour. Early study considered the reflection arose from branching area of arteries. Later we knew that the main reflection sites were arterial-arteriolar junction. The different properties of vascular bed that work different as filter was studied by Young in 1992. Each arterial bed selects specific frequency on which to propagate and reflect. The beds are attached to the aorta at different sections and with different length of arteries. These effects result in organic arterial beds having different frequency properties, as the frequency selectivity is heavily dependent on the positions and the physical properties of organs. The kidney and spleen are more rigidly encapsulated organs, and communicate with the aorta through shorter arteries. Such organic beds may couple strongly with the aorta and amplify the high-frequency components of pressure waves. The arteries of stomach and the intestine are much longer and more divergent. Such arterial beds simply work as reflective sites. The importance of resonance in hemodynamics had been revealed by Wang in 1991 and the characteristics of different vascular beds were also studied in 1994. The impedance of a kidney system in rat revealed that second and third harmonics were resonant frequencies. At the second harmomic, the pressure wave and fluid flow run in a round trip through the branch of the kidney. Whereas it is difficult for the third harmonics flow to enter the kidney. The kidney vascular system exhibits a resonant frequency at the second harmonics of the heartbeat. From above studies the data were obtained from artery line in rat’s tail artery or radial artery line in human. Since renal cortex area is the main site of arterial-arteriolar junction that can be detected non-invasively with power Doppler. We have a good position to detect renal cortex vascular beds waveform non-invasively with ultrasound and try to clarify its physiological property. For all examination, ATL ultrasound machine (HDI 5000) and a model 2-5 MH probe are used to evaluate kidney. Pulse repetition frequencies (PRFs) set at 1000Hz with gain optimized (CPA 79%, MAP1, WF med, and Flow opt V). Images were recorded 17-27 frames per second according to depth of kidney and recorded by a digital image processing unit. These frames were transferred to computer one by one and in order. We pick up images including at least three heart circles and usually more than 50 frames at each set of data available. Examination procedure: Patients did not need any special preparation and took a rest more than 15 minutes. All patients were instructed to take easy to prevent change his or her heart rate by emotion. For native kidney evaluation, volunteers or patients would be put on supine or flank position according to most appropriate position for data collection. Patients with short of breath that disturb image collection would be quitted. Valsava Maneuver was avoided since this procedure would interfere with data collection. Each patient was asked to hold respiration in seconds to facilitate completing data collection. The kidney was first examined in B-mode and judged for echogenicity, structural differentiation or abnormality, renal size and cortex thickness. Patients with situation like hydronephrosis, tumor or calculi were excluded. With the use of color and/or power Doppler, an area of cortex and medulla was evaluated and focused a region containing a complete vascular tree infused by an interlobar artery. The superficial cortex would be better for detection of perfusion since the deep renal cortex often showed less flow than the superficial cortex, presumably due to attenuation. This vascular tree includes an interlobar artery, interlobular artery and arcuatal artery. Brush in peripheral area of cortex in image of power Doppler was en bloc recorded. Among these cases, some were recorded more than one cortex area to check the homogeneity. Usually three areas were selected including upper, middle and lower pole. In some cases a same area were recorded twice, one with color Doppler and then with power Doppler, because we intended to know whether there was difference between color and power Doppler in modulus calculated with Fournier analysis. With pulse wave Doppler, maximal and minimum velocity were measured in the interlobular artery, downstream. Interlobular and arcuatal artery each wave selected had to fit the criteria that at least 5 stable continuous pulse with same waveform available. The RI for all the arteries was calculated using the formula: RI= (maximal systolic flow velocity subtracted end diastolic flow velocity, then divided by maximal systolic flow velocity). PI= (maximal systolic flow velocity subtracted end diastolic flow velocity, then divided by mean systolic flow velocity). Mean RI was the mean of three independent RI values calculated from spectral Doppler waveform among a same artery. This effort tried to decrease the detecting error. Fournier analysis: The collected 2-D Doppler images needed to transform to waveform for Fournier analysis, we had to transform those further. Firstly, we transformed this image into VI (vascularity index) (%) values. VI was identified as the percentage of colored pixel in a selected area that we preferred. Usually this area included a complete vascular tree in cortex and medulla, from medulla and collecting system junction to peripheral cortex. Renal capsule must be included because we do not want to neglect brush not seen by naked eyes. The ratio in each frame was recorded as VI (%) that plotted against frame number. This procedure was completed by computer and software was kindly supported by Professor 邵耀華。 This VI to frame pictures show a sinusoid picture. The waveform could be transformed digitally with Fourier transformation to moduli, named H1, H2, to Hn, for further analyses. There were 117 cases in non-transplant group and 108 in transplant group. The male to female ratio was 56% and 77%. There were 164 and 273 effective data available in each group. In non-transplant group, the collected parameters included age, patient physical condition, kidney size, RI value (including arcuate, interlobar, interlobular RI), parenchyma perfusion with power Doppler, body weight, hemocrit, and serum creatinine. In transplant group, we collected the following parameters: age(donor and recipient), after transplantation follow-up time(coding in months), graft situation(coding in smooth, acute rejection, chronic allograft nephropathy, elevated Cre, and just after transplantation), proteinuria, prescribed medication(CNI, sirolimus, antihypertensive agents uses to treat hyperlipidemia and hyperuricemia), kidney size, RI value(including arcuate, interlobar, interlobular RI), parenchyma perfusion with power Doppler, body weight, hemocrit, and serum creatinine. There were two significant results: 1. The transplant group: The age of recipient is a good predictive factor of H21(the ratio of H2 to H1). With current knowledge, the kidney has a resonance harmonics among H2 and H1. The ratio of H2 to H1 reveals the relative component of these two harmonics. Aging caused vascular stiffness increased, then influence vessel distensibility of aorta, large arteries and small peripheral vessels. The flow in a vessel propagates decreased under high frequency harmonic component, since high frequency harmonic reflected the elastic component of a vessel. H2 and H1 impedance might increase in aging process since there were drastic changes in the vasculature, then increase cardiac afterload. Both nonpulsatile and pulsatile component of arterial load increased chronologically too. The flow propagates into each organ also decreased. (Kelly R, 1989). However, no interpretation about separate component of impedance was found. From our study, the ratio H21 decreased with age means the high harmonic component, which stands for elastic part of a vessel, decreased more prominent than H1, which stands for rigid tube part. Since a kidney transplant was implanted into a new hemodynamic situation (the recipient), this kidney had to couple with the new system. From series RI and renal systolic pressure evaluation, (Isiklar I, 2000) the transplant took several months to couple into this system. The transplant kidney would adapt the recipients’ systematic circulation and the physical age of this recipient. 2. The mean interlobar RI value has good correlation with patient’ age: With our best knowledge, the mean RI has good correlation with age (Mary TK, 1996). The mean RI is a mean of RIs measured from different part of this kidney or different parenchyma vessel. However, the intrarenal vessel RI value decreases in order from renal artery, interlobar artery to cortical artery(Filippo Quarto di P, 1996). The different RI valued measured from parenchyma vessel also decreases among peripheral vessel. The aim of study was to test whether different RI value correlated with age existed or not. However, the mean interlobar artery RI value had high statistical correlation with age (p=0.007). And arcuate RI value also has significant correlation with age (p=0.05). With aging, characteristic changes were noted in all sites, including pulse amplitude increased with advancing age, diastolic decay steeped, and diastolic waves less prominent. The aging process hence causes the elevated systolic velocity and decreased velocity. According to the definition of RI value, RI value elevated is doomed. We just tried to clarify which parenchyma vessel can correlated well with age. RI of interlobar artery has once been reported correlated well with perfusion pressure during acute urinary retention.(Michel C, 1999) With my best knowledge, interlobar artery probably has good correlation with change of vessel distensibility whereas interstitial fibrosis and vessel stiffness contribute a lot to vessel distensibility. Aging would cause change, such as vessel stiffness.(Michael EM, 2000)
|
|
Allen KS, Jorkasky K, arger PH, et al.: Renal allografts: Prospective analysis of Doppler sonography. Radiology 169:371-6, 1988. Alexander JW, Vaughn WK, Carey MA:The use of marginal donors for organ transplantation:the role and younger donors. Transplant proc 1991;23:905-9. Bruno M, Pannier P, arnold H, et al.: Methods and devices for measuring arterial compliance in humans. American Journal of Hypertension 2000;15:743-53. Feldman HI, Fazio I, Roth D, et al: Recipient body size and cadaveric renal allograft survival. J Am Soc Nephrol 1996;7:151-7. Filippo Quarto di P, Roberto R, Attilio E, et al.:Relevance of resistive index ultrasonography measurement in renal transplantation. Nephron 1996;73:195-200. Filippo quarto di Palo, Roberto rivolta, Attilio elli, et al.:The transplanted nephroic mass influences renal vascular resistance and blood flow of the kidney graft. Nephron 1997;76:43-8. Galesic K, Brkljacic B, Sabljar-Matovinovic M, et al: Renal vascular resistance in essential hypertension: duplex-Doppler ultrasonographic evaluation. Angiology 2000; 51(8):667-75. Gill IS, Hodge EE, Nowick AC, et al.:Impact of obesity on renal transplantation . Transplant proc 1993;25:1047-8. Greenfield JC, Cox RL, Hernandez RR,et al: Pressure-flow studies in man during the Valsava Maneuver with observation on the mechanical properties of the ascending aorta. Circulation 1967;35:653. Hamilton WF: The patterns of the arterial pressure pulse. Am J Physiol 1944;141: 235-41. Heckman R, Rehwald U, Jakubowski HD, et al.; Sonographic criteria for renal allograft rejection. Urol Radiol 4:15-8, 1982. Hilborn, Bude and Murphy K J, et al: Renal transplant evaluation with power Doppler sonography. The british Journal of radiology 1997;70:39-42. Hostetter TH: Chronic transplant rejection. Kidney Int 1994;46:266-79. Isiklar I, Aktas A, Akgun S, et al.:From donor to recipient. Doppler US, power US and scintigraphy of kidney perfusion before and after transplantation. Acta Radiologica2000;41:285-7. Jorseph M: Role of abdominal aortic branches in pulse wave contour genesis. Circulation research 1956;9:676-9. Karl Turetschek, Christian Nasel, Partick Wunderbaldinger, et al: Power Doppler versus color Doppler imaging in renal allograft evaluation. J ultrasound med 1996;15:517-22. Kappes U, Schanz G, Gerhart U, et al. Influence of age on the prognosis of renal transplant recipients. American Journal of Nephrology 2001;21:259-63. Karreman G: Contributions to the mathematical biophysics of the cardiovascular system. J Math Bioph 1953;15:185. Kaveggia LP, Perrella RR, Grant EG, et al.: Duplex Doppler sonography in renal allografts: The significance of reversaed flow in diastolic. AJR 155:295-8, 1990. Kelly R, Fracp C, Hayward et al.:Noninvasive determination of age-related change in the human arterial pulse. Circulation 1989;80:1652-9. Keogan MT, Kliewere MA, Hertzberg BS, et al.: Renal resistive indexes: variability in Doppler US measurement in a healthy population. Radiology1996;199:165-9. Landowne M: Harmonic analysis of pressure wave propagation. Fed Proc 1957;16:77. Li JK, Melbin J, Riffle RA, et al: Pulse wave propagation. Circulation Research 1981; 49(2):442-52. Linkowski GD, Warvariv V, Filly RA, et al.: Sonography in the diagnosis of acute rejection and cyclosporin nephrotoxicity. AJR 148:291-5, 1987 Lufft V, Klien V, Tusch G, et al.: Renal transplantation in older adults: is graft survival affected by age? A case control study. Transplantation2000;69:790-4. Mary TK, Mark AK, Barbara SH, et al.:Renal resistive indexes:variability in Doppler US measurement in a health population. Radiology 1996;199:165-9. McDonald DA: The relation of pulsatile pressure to flow in arteries. J Physiol London 1955;127:533-52. McDononald,DA: McDononald’s blood flow in arteries. 2nd ed. London: Arnold, 1974. Meier-Kriesche HU, Ojo AO, Cibrik DM, et al.:Relationship of recipient age and development of chronic allograft failure Transplantation 2000;70:306-10. Michael F, O'Rourke: Vascular impedance in studies of arterial and cardiac function. In: Physiological review; Vol. 62. No. 2, April 1982. Michel C, Carol E, Barnewolt, et al.: Renal blood flow in pigs:change depicted with contrast-ehnanced harmonic US imaging during acute urinary obstruction. Radiology 1999;212:725-31. Michel Claudon, Carol E. Brnewolt, George A Taylor, et al: Renal blood flow in pigs: change depited with contrast-enhanced harmonic US imaging during acute urinary obstruction. Radiology 1999;212:725-31. Morgan JW, Ferrantly WR: Wave propagation in elastic filled with streaming fluid. J Acoust Soc America 1955;27:715. Muller A: Uber die Fortpflanzungsgeschwindigkeit von Druckwellen in denhbaren Rohen bei ruhender und stromender Flussigkeit. Helvet Physiol Et pharmacol Acta 1950;8:228. Odland MD, Kasiske BL: Kidney from female donors are increased risk for chronic allograft rejection. Transplant proc 1993;25:912. O'Rourke MF, Yaginuma T, Avolio AP: Physiological and pathophysiological implications of ventricular/vascular coupling. Annals of Biomedical Engineering1984 12(2):119-34. Perrella RR, Duerinckx AJ, Tessler FN, et al.: Evaluation of renal transplant dysfunction and review of the literature. Am J Kidney Dis 15:544-50, 1990 Peter F. Hoyer, Raoul schmid, Lutz wiinsch Udo Vester: Color Doppler energy-a new technique to study tissue perfusion in renal transplants. Pediatr Nephrol 1999;13: 559-63. Phebe C, Nabil Maklad M, Michael R. Color and power Doppler imaging of kidneys. World J Urol 1998;16:41-5. Rifkin MD, Needleman L, Pasto ME, et al.: Evaluation of renal transplant rejectiob by duplex Doppler examination: value of the resistive index. AJR 148:759-62, 1987 Rigsby CM, Burns PN, Weltin GG, et al.: Doppler signal quantitation in renal allografts: comparison in normal and rejection tansplants with pathologic correction. Radiology 162:39-42, 1987 Rigsby CM, Taylor KJW, Welton GW, et al.: Renal allografts in acute rejction: evaluation using duplex sonography. Radiology 158:375-8, 1986 Rita R,Perrella. Renal transplantation:Use of sonography. Urol Radiol 1992;14:43-8. Robert :Harmonic analysis of aortic pressure pulses in dogs. In: Circulation research; Vol 9.1961. Rubin Jonathan M, Adler Ronald S, Fowlkes J Brian, et al: Fractional moving blood volume: estimation with power Doppler US. Radiology 1995;197:183-90. Taylor MG: Hemodynamics. A Rev Physiol 1973;35:87-116. Taylor MG: The input impedance of assembly of randomly branching elastic tubes. J Biophys 1966;6:29-51. Takahashi S, Narumi Y, Takahara S, et al.: Acute renal allograft rejection in the canine evaluation: evaluation with serial duplex Doppler ultrasound. Transplanation proceedings 1999;31:1731-4. Terry JD, Rysavy JA, Frick MP. Intrarenal Doppler: characteristics of aging kidneys. Journal of Ultrasound in Medicine 1992;11:647-51 Tullius SG, Tilney NL: Both alloantigen-dependent and independent factors influence chronic allograft rejection. Transplantation 1995;59:313-8. Wang YY, Chang SL, Wu YE,et al: Resonance. The missing phenomenon in hemodynamics. Circulation Research1991; 69(1):246-9. Wang WK, Hsu TL, Chen HL, et al: Blood pressure and velocity relation in tissue. Proc of this biofluid mechanics Munich1994; 119-32. Womersley JR: Elastic tube theory of pulse transmission and oscillatory flow in mammalian arteries. EADC report TR 56-614. Dayton, Ohio, Wright air development center, 1957. Womersley JR: Oscillatory flow in arteries: the reflection of the pulse wave at junctions and rigid inserts in the arterial system. Phys Med Biol 1958; 2:313-23. Weskott HP, Knuth C: Ultrasound angiography: phantom measurements of slow blow flow. Bildgeburg 62:189-92,1995 Yu GL, Wang YL, Wang WK: Resonance in the kidney system of rats. American Journal of Physiology 1994;267(4 Pt 2):H1544-8t. Young ST, Wang WK, Chang LS, et al: Specific frequency properties of renal and superior mesenteric arterial beds in rats. Cardiovasc res 1989;23(6):465-7. Young ST, Wang WK, Chang LS, et al: The filter properties of the arterial beds of organs in rats. Acta Physiol Scand 1992;145:401-6.
|
| |