simultaneousestimationofglomerular …jnm.snmjournals.org/content/36/9/1701.full.pdf ·...

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Nuclear Medicine Seivice, Department oflnternal Medicine, Biostatistics and Data Processing Center, 1ST, Genoa, Italy University of Genoa Medical School; and &perimental vides a measurementof the tubularexcretion rate (TER) of MAG3 [TER(MAG3)] after its correction by a factor 1.5, closely approximates [‘31I]OIHclearance (8). Further more, 5tCr-EDTA, when available in a form suitable for human use, is the most reliable agent for monitoring go merular filtration rate (GFR) because 5tCr-EDTA renal clearance closely approximates inulin clearance (11—13). The biological and physical properties of 51Cr-EDTAand @Tc-MAG3 led us to study these radiopharmaceuticals for simultaneous estimation of GFR and TER(MAG3) us ing multi-sample (3,5,6,14—18) and single-sample plasma clearance methods (16,18—22)in a population of normal volunteers and patients with various renal disorders. MATERIALS AND METhODS Subjects Westudied17healthyadultvolunteers(meanageof 35.3yr. range23—47 yr)and28patients(11men,7women;aged26—67 yr) with various renaldiseases whose degree of renalimpairmenthad been tested by estimating creatinine clearance according to the formulaof Goult-Cockroft[creatinineclearance (ml/min) = 140- age (yr) x weight (kg)/72 x plasma creatinine concentration (mgi 100 ml)]. Values from their estimate were corrected by a factor equal to 0.85 in women. Diagnoses were made based on histolog icalappearanceand/orclinicalfindings.In particular(as reported in Table 1), five patients had various types of chronic giomemlo nephritis,includingIgAglomerulonephritis (Patients12—24), mm imal lesion glomerulonephritis (Patient 16), membrano proliferative glomerulonephritis (Patient 27), mesangiocapillary glomerulonephntis (Patient 10), while other patients had hyper tensiveangionephrosclerosis(Patients1,5, 7, 11, 13, 14, 19,26), diabetic nephropathy (Patients 20—23), secondary glomerulone phntis (Patients 2, 3, 4, 22) and nephrocarcinoma(Patient 25). Each subjectwas given a singe intravenouscompositeinjection dose containing about 37 MBq @â€oeTc-MAG3 (prepared from a commercialkit formulation)and about3.7MBq51Cr-EDTA. The EDTA had a specific activityof about 37 MBq/mg.Separate standardsfor @‘Tc-MAG3 and5tCr-EDTAwere preparedby dilution from duplicate syringes. After injecting the dose, nine blood samples were drawn into standard EDTA-anticoagulated vacuum sample tubes at 10, 20, 30, 45, 60, 90, 120, 180 and 240 mm. Three milliliters of the plasma obtained from each blood sample and 3 ml of the acqueous standard solutions of @Tc MAG3 and 5tCr-EDTAwere pipetted into counting tubes and countedusingamultichannel PackardAutogammaSpectrometer. To correctthecontributions of scatteredphotonsfrom51Cr,the totalcountsinthe @Tc channelwerecorrectedforspilloverfrom Companng the measurements of both glomerular filtration (GFR)andtubularexcretionrates @TER(MAG3)] bymulti-sample and single-sample methods has been performed after a single bolus injectionof 3.7 MBq 51Cr-EDTAplus 37 MBq @9c- MAG3. Methods: We studied 17 healthy volunteers and 28 patients with a wide range of renal function. For each plasma clearence curve, nine plasma samples were drawn at intervals from 10 to 240 mm after injectionof tracers. When comparing indMduatvalues for GFR and TEA (MAG3)from the tracer dilutionspaces (VD)withthose derivedfromthe analysis ofthe entireplasma disappearancecurves of two radiopharmaceuti cats, a good linear correlation appears (r = 0.96). Resufts: We found that the nadir-error(S@.@) @ predicted GFR occurs at 180 mm (11.0 mI/mm/i.73 me), while the nadir-errorfor predicted TEA(MAG3)is reachedat 90 mm(26.4mVmin/1 .73 ms). Conclusion: In the computation of GFA and TEA (MAG3) with a single-samplemethod, it appears that the mean residence time (t)for each tracer represents the optimum plasma sampling time. Our results suggest that the single injection of 51Cr-EDTA and @Tc-MAG3 followedbybloodsamplingtwicepermitsac curate simultaneous estimationof GFR and TEA (MAG3)and, after correction of the latter kinetic parameter, effective renal plasma flow. KeyWords:glomerularfiltrationrate;tubularexcretionrate; effective renal plasma flow, chrorruum-51-EDTA; technetium 99m-MAG3 J NucIMed1995;36:1701-1706 @lL@echnetium-99m •-mercaptoacetyltriglycine (@Fc-MAG3) has propertiescomparableto [‘31ljorthoiodohippurate (1,2), and although the renal clearance of this radiopharmaceutical is littleover halfthat of ‘31I-hippurate clearance(3—5), @â€oe@Tc MAG3clearancecorrelateswell with thatof [‘3'IJOIH (4—9). For these reasons, and because of its more suitable energy and better dosimetry (10), @Tc-MAG3has been proposed as a substitute for [‘31IIOIH in plasma clearance measurement of effective renal plasma flow (ERPF) (2,3,5,6,8,10). Indeed, @@@iTc@MAG3 clearance, which pro ReceivedMay17, 1994;revisionacceptedOct. 13, 1994. Forcorrespondenceorrepiintscontat G@,annI F.Fresco, MD, Depar@entof InternalMedidne,UniversftyofGenoaMed@School,\IsaleBenedettoXV,No.6, 16132Genoa,It@y. SimultaneousEstimationofGFRandERPF• Fresco at al. 1701 Simultaneous Estimation of Glomerular Filtration Rate and Renal Plasma Flow Giovanni F. Fresco, Flavia DiGiorgio and Giovanna L. Curti by on September 16, 2020. For personal use only. jnm.snmjournals.org Downloaded from

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Page 1: SimultaneousEstimationofGlomerular …jnm.snmjournals.org/content/36/9/1701.full.pdf · 2006-12-19 · NuclearMedicineSeivice,DepartmentoflnternalMedicine, BiostatisticsandDataProcessingCenter,1ST,Genoa,Italy

Nuclear Medicine Seivice, Department oflnternal Medicine,Biostatistics and Data Processing Center, 1ST, Genoa, Italy

University of Genoa Medical School; and &perimental

vides a measurementof the tubularexcretion rate (TER)ofMAG3 [TER(MAG3)] after its correction by a factor 1.5,closely approximates [‘31I]OIHclearance (8). Furthermore, 5tCr-EDTA, when available in a form suitable forhuman use, is the most reliable agent for monitoringgomerular filtration rate (GFR) because 5tCr-EDTA renalclearance closely approximates inulin clearance (11—13).The biological and physical properties of 51Cr-EDTAand

@Tc-MAG3led us to study these radiopharmaceuticalsfor simultaneous estimation of GFR and TER(MAG3) using multi-sample (3,5,6,14—18)and single-sample plasmaclearance methods (16, 18—22)in a population of normalvolunteers and patients with various renal disorders.

MATERIALSAND METhODS

SubjectsWe studied17healthyadultvolunteers(meanageof 35.3yr.

range23—47yr)and28patients(11men,7women;aged26—67yr)with various renaldiseases whose degree of renalimpairmenthadbeen tested by estimating creatinine clearance according to theformulaof Goult-Cockroft[creatinineclearance (ml/min) = 140-age (yr) x weight (kg)/72 x plasmacreatinineconcentration(mgi100 ml)]. Values from their estimate were corrected by a factorequal to 0.85 in women. Diagnoses were made based on histologicalappearanceand/orclinicalfindings.In particular(as reportedin Table 1), five patients had various types of chronic giomemlonephritis,includingIgAglomerulonephritis(Patients12—24),mmimal lesion glomerulonephritis (Patient 16), membranoproliferative glomerulonephritis (Patient 27), mesangiocapillaryglomerulonephntis (Patient 10), while other patients had hypertensiveangionephrosclerosis(Patients1,5, 7, 11, 13, 14, 19,26),diabetic nephropathy (Patients 20—23),secondary glomerulonephntis (Patients 2, 3, 4, 22) and nephrocarcinoma(Patient 25).Each subjectwas givena singe intravenouscompositeinjectiondose containing about 37 MBq @“Tc-MAG3(prepared from acommercialkit formulation)and about3.7 MBq51Cr-EDTA.TheEDTA had a specificactivityof about37 MBq/mg.Separatestandardsfor @‘Tc-MAG3and 5tCr-EDTAwere preparedbydilution from duplicate syringes. After injecting the dose, nineblood sampleswere drawn into standard EDTA-anticoagulatedvacuum sample tubes at 10, 20, 30, 45, 60, 90, 120, 180 and 240mm. Three milliliters of the plasma obtained from each bloodsample and 3 ml of the acqueous standard solutions of @TcMAG3and 5tCr-EDTAwere pipetted into counting tubes andcountedusinga multichannelPackardAutogammaSpectrometer.To correctthecontributionsof scatteredphotonsfrom51Cr,thetotalcountsinthe @Tcchannelwerecorrectedforspilloverfrom

Companng the measurements of both glomerular filtration(GFR)andtubularexcretionrates @TER(MAG3)]bymulti-sampleand single-sample methods has been performed after a singlebolus injectionof 3.7 MBq 51Cr-EDTAplus 37 MBq @9c-MAG3. Methods: We studied 17 healthy volunteers and 28patients with a wide range of renal function.For each plasmaclearence curve, nine plasma samples were drawn at intervalsfrom 10 to 240 mm after injectionof tracers. When comparingindMduatvalues for GFR and TEA (MAG3)from the tracerdilutionspaces (VD)withthose derivedfromthe analysis of theentireplasma disappearancecurves of two radiopharmaceuticats, a good linear correlation appears (r = 0.96). Resufts: Wefoundthat the nadir-error(S@.@)@ predictedGFR occurs at 180mm (11.0 mI/mm/i.73 me), while the nadir-errorfor predictedTEA(MAG3)is reachedat 90 mm(26.4 mVmin/1.73 ms).Conclusion: In the computation of GFA and TEA (MAG3)witha single-samplemethod, it appears that the mean residencetime (t)for each tracer represents the optimum plasma samplingtime. Our results suggest that the single injection of 51Cr-EDTAand @Tc-MAG3followedby bloodsamplingtwicepermitsaccurate simultaneous estimationof GFR and TEA (MAG3)and,after correction of the latter kinetic parameter, effective renalplasma flow.

Key Words: glomerularfiltrationrate;tubularexcretionrate;effective renal plasma flow, chrorruum-51-EDTA; technetium99m-MAG3

J NucIMed1995;36:1701-1706

@lL@echnetium-99m•-mercaptoacetyltriglycine(@Fc-MAG3)has propertiescomparableto [‘31ljorthoiodohippurate(1,2),and although the renal clearance of this radiopharmaceuticalis littleoverhalfthatof ‘31I-hippurateclearance(3—5),@“@TcMAG3clearancecorrelateswell with thatof [‘3'IJOIH(4—9).

For these reasons, and because of its more suitableenergy and better dosimetry (10), @Tc-MAG3has beenproposed as a substitute for [‘31IIOIHin plasma clearancemeasurement of effective renal plasma flow (ERPF)(2,3,5,6,8,10). Indeed, @@@iTc@MAG3clearance, which pro

ReceivedMay17, 1994;revisionacceptedOct. 13, 1994.ForcorrespondenceorrepiintscontatG@,annIF.Fresco,MD,Depar@entof

InternalMedidne,UniversftyofGenoaMed@ School,\IsaleBenedettoXV,No.6,16132Genoa,It@y.

SimultaneousEstimationof GFRand ERPF•Frescoat al. 1701

Simultaneous Estimation of GlomerularFiltration Rate and Renal Plasma FlowGiovanni F. Fresco, Flavia DiGiorgio and Giovanna L. Curti

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Single-Sample MethodWecomputedthenadir-error(,@,JforpredictedGFRandTER

(MAG3) from thevolumeof dilution VD [VD = ID/c(t)] for either51Cr-EDTAor @‘Tc-MAG3,as reportedby Tauxeet al. (24) ineach subject. The various values for VD and the correspondingvaluesfor GFRandTER(MAG3)were fittedto an exponentialfunction of the type:

GFR [TER(MAG3)] (mI/min/1.73 m2)

= Fm@[l — C aWD -

where Fm,,,,represents theoretical asymptotic maximumvalue ofGFR [TER(MAG3)], a is the rate constant, and Viag @5the intercept of the fittedcurve on the abscissa, andto a parabolicfunctionofthe type:

GFR [TER(MAG3)I (mI/min/1.73 m2)

= A + BVD + CVD2,

where A is the intercepton the ordinate, B the coefficient of thelinear term and C the coefficientof the quadraticterm. The correlations between VD and multi-sampleGFR and TER(MAG3)were assayed only for values of VD determinedat plasma timesaroundthatof the meanresidencetime (i) of 51Cr-EDTAand

@‘@Tc-MAG3as determined by the multi-sample method.

RESULTS

Mum-Sample MethodFor the plasma disappearance curves of injected 51Cr

EDTA and @“@Tc-MAG3,individualvalues for GFR andTER(MAG3) in normal subjects and in patients are listed inTable 1. The mean value for GFR in normal subjects is103.8 ±17.2 ml/min/1.73 m2 (mean ±s.d.) and 71.8 ±44.1ml/min/1.73 m2 in patients. As reported in Table 2, themean value for the volume of injection compartment (V1)for 51Cr-EDTA is 7.59 ±0.81 liters/1.73 m2 in normals and8.35 ±1.48 liters/1.73 m2 in patients. The total apparentdistribution volume (V1 + V2)of 51Cr-EDTA in normals is14.96 ±3.00 liters/1.73 m2 and 16.52 ±3.42 liters/1.73 m2in patients. The meanvalue for the mean residence time for51Cr-EDTA is 148.0 ±37.9 min in normals and 300.9 ±154.1 min in patients with renal disorders. The mean valuefor TER(MAG3) is 309.5 ±40.3 ml/min/1.73 m2 for normals and 223.8 ±123.1 ml/min/1.73 m2 for patients. Thevolume for the injection compartment for @“Tc-MAG3is7.68 ±4.02 liters/1.73 m2 for normals compared to 10.32 ±2.58 liters/1.73 m2 for patients. The (V1 + V2) for @“@‘FcMAG3 is 19.64 ±5.69 liters/1.73 m2 for normals and 24.32±11.82 liters/1.73 m2 for patients. Finally, the mean valuefor the mean residence time for @Tc-MAG3is 63.4 ±14.9min for normals and 132.0 ±87.4 mm for patients.

Single-Sample MethodCorrelation between VD and multi-sample GFR and

TER(MAG3) was performed at 120, 180 and 240 min forGFR and at 45, 60, 90 and 120 min for TER(MAG3). Asreported in Table 3, the nadir-error@ for predictedGFR equals 11.0 ml/min/1.73 m2 when dilution space for51Cr-EDTAis computed at 180 min, while S,,,,@for pre

F2-1

<

F1-2

I 2

FIGURE 1. Schematic representation of the two-pool modeladopted in this study. Compartment 1 (injectioncompartment) isinterconnectedwithcomparbTent2 (exchangeablepool).Reservolr3 representsthe kidneys,i.e.,the only irreversiblelossof the substance from the system.

951Cr.Thereafter,accordingto theopentwo-compartmentmammillaiy system (Fig. 1), as suggested by Sapirstein et at. (23),51Cr-EDTAand @‘Tc-MAG3plasmadatawerefittedwitha sumof two exponential functions of the formula:

c(t)= Ae@t + Be_Pt,

where c(t) (KBq/mI/1.73m2)is the normalizedto the body surfaceof 1.73 m2plasma concentration at time t(min), expressed as thepercent injected dose (%ID)(MBq)/liter,A and B are the intercepts on the ordinate;and a, f3(min') representthe slopes of therapid and slow components. This analysis was performed on acomputer using the ENZFI'VFprogram(Elsevier/Biosoft, Cambridge, U.K.). Accordingto the Stewart-Hamiltonformula, theamountof irreversibleremoval of tracersfromthe system versuskidneys (i.e., glomerularfiltrationrate [or the tubular excretionrate of @Tc.MAG3J),were estimated by the equation:

GFR [TER(MAG3)XmI/miiVl.73 m2)

The following kinetic parameterswere also derived:

•V1(liter/1.73m2),the volumeintowhichthe injectionwasmade (V1 = ID/(A + B)).

•F1_2(ml/min/1.73m2),the intercompartmentalflowratebetween two compartments of the model adopted (F1_2=V1(Aa+ Bf3)/(A+ B) —F13).

•k1_2(min'), the fractionalrate transferfromcompartment1to compartment2 (k1_2= F1@/V1).

•V2 (liter/1.73m2),the volume ofthe interchangeablepool (V2= F1_3 F1_2/V1a@).

•V@,1(literfl.73m2),thetotalvolumeof distributionof tracers(V@0@= V1 + V2).

•i (mm), the mean residence time of the substance in thesystem [t = (Vi + V2)/F1_3J.

IDaf3

= Af3 + Ba F13.

1702 The Joumatof NuclearMedicine•Vol.36 •No. 9 •September1995

ID

J:@t@t

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SubjectsPatientsSubject

no. GFRM* GFRSt @RQ@,,jA@33)@tTER(MAG3)@'Patientno. GFRM* GFRSt TER(MAG3)MTER(MAG3)5@

GFRM*= multi-sampleGFR; GFR8t= single-sample GFR (180 mm);TER(MAG3)M*= multi-sampleTER(MAG3); TER(MAG3)5'= single-sampleTER(MAG3)(90 mm).

TABLE 1Clearance EstimatiOn in Subjects and PatientS (mVmin/1.73 m@)

191.585.6276.2292.5123.813.248.448.62101.493.2279.1316.7253.146.6169.6160.83139.7158.0252.1247.7319.514.7169.0178.54131

.877.2302.7285.2474.975.3375.3374.2599.7109.4339.2347.2548.548.4188.6169.1e121.7120.4319.8341.56150.8147.7292.7302.9768.879.8395.6386.4741.644.9132.1110.78110.599.0320.7345.08147.9147.7261.7230.8998.792.3287.9313.89149.6144.4459.5449.710100.8100.0328.2338.11047.445.9106.899.81

192.787.7270.9265.31125.232.252.672.212111.2104.8397.3386.41267.372.4101.4145.313100.096.5272.7247.71337.330.698.899.214100.9101.1311.7297.51470.070.1158.6151.71578.683.1284.2300.215167.4159.0471.6395.116107.2102.6317.8300.21656.557.0319.0302.917109.6105.2305.7345.01771.774.3204.5207.8mean±s.d.103.8±17.299.8±18.7309.5±40.3315.1

±41.81819202122232425262728

mean ±s.d.113.8

52.441.841.944.945.461.1

164.866.261.864.8

71.8 ±44.1112.9

53.044.650.170.153.674.9

161.672.862.470.1

73.2 ±42.6175.7

126.1243.5143.7173.8320.6379.4451.0

90.1275.3277.1

223.8 ±123.1147.5

109.8271.5128.4143.5290.0378.3418.4168.2310.9265.3

219.0 ±113.5

dicted TER(MAG3) is 26.4 mi/mm/i .73 m2 when dilutionspace (VD)for @Tc-MAG3is determinedat 90 minpostinjection. As reportedin Table 1, the mean value for GFR is99.8 ±18.7 ml/min/1.73 m2 in normals and 73.2 ±42.6mi/mm/i .73 m2in the 28 patients with renal diseases, whilethe mean value for TER(MAG3) is 315.1 ±41.8 mI/min/1.73 m2 in normals and 219.0 ±113.5 ml/min/1.73 m2 inpatients. Wilcoxon analysis of individualvalue for multisample GFR in both study groups indicated no significantdifference (p = 0.72). No significant differences were foundwhen multi-sample TER(MAG3) values were comparedwith predicted TER(MAG3) from VD computed at 90 min(p = 0.61). In addition,our results demonstrate(Figs. 2 and3) a good linear regression between multi-sample and single-sample GFR andbetween multi-sampleandsingle-sampie TER(MAG3) (r = 0.96).

DISCUSSION

The mean values and ranges for GFR and TER(MAG3)obtained from the multi-samplemethod agreed with thosereported by other authors (6,8,14,16—18,22),suggestingthat these kinetic parameters may be suitable reference

parameters when evaluating the accuracy of predictedGFR and TER(MAG3) with the single-sample method.

For other kinetic parameters determined by the multicompartmental approach, we obsewed that the volume forthe injection compartment V1 for two injected radiopharmaceuticals in normals is approximately two times greaterthan the plasma volume. According to Tauxe et al. (24),this compartment should include, other than plasma, extravascular tissues. Furthermore, the size for the apparentdistributionvolume for 51Cr-EDTAand @‘@Tc-MAG3(V2),which in normals equals 7.37 ±2.49 and 11.96 ±4.89liters/1.73 m2 (10), respectively, should be assigned to thetracerbeing distributedthroughoutthe body but not available to the kidneys for clearance. For (V1 + V2), of 51CrEDTA, there was no significant difference between subjects with low-normal and high normal GFR and normals;for @‘@‘Tc-MAG3,there was a significantly greater difference in between subjects with high-normalTER(MAG3)andnormals(37 liters/i .73 m2versus 20 liters/1.73m2).Onecould hypothesize that highvalues for TER(MAG3)resulting in more rapiddisposal of @Tc-MAG3molecules fromthe system as opposed to kidneys imply a decrease in the

Simultaneous Estimation of GFR arid ERPF •Fresco et at. 1703

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ParameterSubjects51Cr-EDTA mean ±s.d. (range)99ITrrc@MAG3mean ±s.d.(range)F,@,

(mllmin/1.73 m2)N103.8 ±17.2309.5±40.3.P(60.8—139.7)

71.8 ±44.1(23.8 —167.4)(252.1

—395.6)223.8 ±123.1(48.4 —471.6)vi

(liter/i.73m2)N

P7.59

±0.81(5.84 —9.10)8.35 ±1.48(5.60 —12.06)7.68

±4.02(2.67—14.86)10.32 ±2.58(4.30—14.66)F1@

(mI/min/1.73m2)N

P205.3

±85.8(33.9 —3272)186.7 ±65.9(79.7 —370.2)366.4

±148.2(94.5 —648.7)

310.2 ±191.6(94.5 —924.8)k1@

(min1)N

P0.027

±0.013(0.006—0.051)0.023 ±0.009(0.008—0.048)0.070

±0.050(0.006 —0.163)0.032 ±0.024(0.011—0.111)V2

(liter/i .73 m2)N

P7.37

±2.49(3.47 —14.04)8.17 ±2.66

(3.40 —13.60)1

1.96 ±4.89(6.13 —25.24)14.01 ±10.91(4.55 —47.62)vtot

(lfter/1.73m@)N

P14.96

±3.00(9.31—22.99)16.52±3.4219.64±5.69

(13.93 —36.53)24.32±11.82I

(mm)N

P(9.00

—23.68)148.0 ±37.9(70.6—239.3)

300.9 ±154.1(94.2 —670.7)(9.62

—57.50)63.4 ±14.9(45.3 —91.9)132.0 ±87.4(56.9 —459.0)

Tracert (mm)VD

rangeParabolicExponentialABCS@,F@aV@S@51Cr-EDTA120

18024016-81

17—10820—164—44

—36—124.3

3.21.9—0.022

—0.013—0.00515.0

11.012.0233

2152020.017

0.0150.0101

113915.1

11.012.0@mTc-MAG345

6090

12013—109

15—13217—17221—233—76

—3611249.2

5.83.02.0—0.042

—0.017—0.002—0.00131.3

31.826.428.8501

6149398100.021

0.0100.0040.00311

93130.3

31.526.729.3

TABLE 2Chromium-51-EDTA and Technelium-99m-MAG3 Kinetic Parameters from Normal Subjects (N) and Patients (P) Using the

Two-Comparhi@ent MOdel

mean residence time of tracer in the system and consequently, an expansion of the interchangeablepool V2. Thelatter implies an increase in the total volume of distribution. On the other hand, in subjects with low-normalvaluesfor TER(MAG3), the averagetime @‘@Tc-MAG3moleculesspend in the system prior to irreversible loss appears significantly higher than in normals (t: 165min versus 63 min).Ourkinetic studies demonstrate that the fractionaltransferrate k1_2(= F121V1)remains unchanged in subjects withlow and high-normalvalues for GFR because changes in

clearance (F13) imply variations of both the flow F12 fromcompartments 1 to 2 and distribution volume V1. On thecontrary, in subjects with low and high values for TER(MAG3), significant changes for the fractional transfer ratek1_2occur. These differentresults may be ascribed to theprotein bindingof @Tc-MAG3,which leads to a reducedvalue for the fractionof tracerflowingfromcompartment1to 2 (i.e., k12). The mean residence time in the 17 normalsubjects for 51Cr-EDTA is 148.0 ±37.9 mlii and 63.4 ±14.9 min for @Tc-MAG3.In calculating predicted GFR

TABLE 3Coefficientsand Standard Errors (S@,@)(mI/mm/i.73 m@)fromDilutionSpaces (VD)(liter/i.73 m@)at VariousPlasma Sample

limes (t)

1704 The Journalof NuclearMedicine•Vol.36 •No. 9 •September1995

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ues for the nadir-errorof GFR from the single-samplemethod agree with those of several authors. In particular,Fisher et al. (15) found a standarderrorof about 8 ml/minfor predicted GFR after 51Cr-EDTAadministrationwhendistribution volumes were computed at 180min. Morgan etal. (16) studied 296 patients and observed a nadir-errorforpredicted GFR after 51Cr-EDTAinjection, of about 8 mumm for 180-mmplasma time. In determiningGFR by thesingle-sample method after 5tCr-EDTAinjection, Constable et al. (19) found an errorfor predictedGFR from VDat180 mm plasma time of 4.4 mI/min only. The GFR reference value they used when comparing predicted valueswith that of plasma 5tCr-EDTA disappearance curves tookinto account the 3—5hr portion of this curve.

For TER(MAG3) determined with the single-samplemethod, there are discrepancies to other publishedvalues.In 35 subjects (including 13 normals) Russell et al. (18)observed that the smallest error was present at 45 minpostinjection and equalled 19 mI/min.We attributethe discrepancy to the fact that these authors tested the correlation function at 35, 45 and55 min only, while we tested thiscorrelationat 30, 45, 60, 90 and 120 min. Tauxe et al. (24)observed that the nadir-error for predicted ERPF (when[‘31I]OIHis used) from @Dwas reached at 44 min andequaled about 32 mI/min.Since Tauxe et al. (24) and Russell et al. (18), indicatedthe same plasmatime at 44—45mmfor radiopharmaceuticalscharacterized by different meanresidence times, being that the@ for MAG3 is longer thanthatforOIH (2), there is reason to thinkthatthe nadir-errorfor ERPF from MAG3 is really reached at plasma timesafter45 min. At 45 min, we saw only a “local―nadir-errorabout 30 mi/mm. Our data indicate that a single simultaneous injection of 51Cr-EDTAand @Tc-MAG3followedby two blood samples at 90 and 180 min can result in anaccurate estimate of GFR and TER(MAG3) and after correction of the latter parameter, of ERPF. Our technique,apart from being simple, yields a low radiation dose (10),which further emphasizes its clinical utility, particularlywhen filtrationfractions are needed.

ACKNOWLEDGMENTS

The authorsthankDrs. GiuseppeVilla, AlbertoCifelliandPaoloCalzafortheirassistancein preparingthismanuscript.

REFERENCES1. FritzbergAR, Kasina5, EshimaD, et al. Synthesisandbiologicalevalua

tionof technetium-99mMAG3as a hippuranreplacement.I NuciMed1986;27:1l1—116.

2. TaylorA, EshimaD. Effectsof altered biochemicalphysiologicstates onthe clearanceand biodistributionof technetium-99m-MAG3,iodine-131-0tH andiodine-125-iothalamate.INuci Med 1988;29:669-675.

3. Russell CD, Thorstad B, Yester MV, et al. Comparison of technetium-99mMAG3with iodine-131hippuranby a simultaneousdual-channeltechnique.JNuclMed 1988;29:1189-1193.

4. JafriRA,BrinonKE,NimmonCC,Ctal.Technetium-99m-mercaptoacetyltriglycine:a comparisonwith ‘“I-and ‘@‘I.orthoiodohippurateO!H forroutinerenalwork [Abstracti.I NuciMed 1987;28:647.

5. Kengen RA, MeijerS, BCCkhUISH,et al. Technetium-99m-MAG3 clearanceasaparameterofeffectiverenalplasmaflowinpatientswithproteinuriaandlowered serum albumin Icvels.JNuclMed 1991;32:1709-1712.

2B@

50 100@ 159 200

GFRM (mL/min/l 73 m2)

FIGURE2. Chromium-51EDTAsingle-sampledearancevaluesat 180mm(GFAs(mI/mm/i.73me))correlateweliwiththe referencemulti-sampleclearancevalues (GFRM(mI/mm/i.73me).The linearregression equation is y = 6.50 + 0.91.

and TER(MAG3), the optimum plasma time at which tocalculate VD was chosen on the basis of the mean valuesfor t. Indeed, it was a reasonable assumption that theoptimum time for a single sample parallel the residencetime characterizing clearance from the system.

Our hypothesis is supported by the data of Tauxe et al.(24). These authors studied 116 patients with various renaldisorders whose ERPF had been assayed using ‘31I-OIHand a two-compartmentapproach. They found a total distributionvolume equal to 14 liters and a mean ERPF valueequal to 320 ml/min, which implies a (I) equal to 44 min.This is the same value for the optimum plasma time theyobserved after performingvarious time testings. Our val

FiGURE3. Technetium-99m-MAG3single-sampleclearancevalues at 90 mm @EA(MAG3)s(mI/mm/i .73 rn@))correlate well withthe [email protected] (TEA(MAG3)M(mLImin/1.73me)).The linearregressionequationis y = 16.49+ 0.93.

500

@ 50 100 150 200 250 300 350 400 450 50@

TER(Mt@G3)M (mL/mir,/1 .73 m2)

Simultaneous Estimationof GFR and ERPF •Fresco at at. I 705

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simultaneousestimationof GFRand ERPF, involvinga singleinjectionandtwo blood samples.Intl NuciMed Biol 1977;4:79-83.

17. Gordon I, Anderson PJ, Orton M, et al. Estimation of technetium-99m-MAG3renal clearance in children: two gammacamera techniquescornpared with multiple plasma samples. I Nuel Med 1991;32:1704—1708.

18. Russell CD, Taylor A, Eshima D. Estimation of technetiurn-99m-MAG3plasmaclearancein adultsfromone or two bloodsamples.I Nuci Med1989;30:1955—1959.

19. Constable AR, Hussein MM, Albrecht MP, et al. Renal clearance fromsingle plasma samples. In: Hoilenberg NK, Lange S. eds. Radionuclides innephrology. Stuttgart: Georg Thiene Verlag; 1980;62—66.

20. Jacobsson L. A method for the calculationof renal clearancebased on asingleplasmasample.ClinPhysiol1983;3:297—305.

21. Russell CD, Bischoff PG. Kontzen FN, et al. Measurement of glomerularfiltrationrate: single-injectionplasmaclearancemethodwithout urine collection.I NuciMed 1985;26:1243—1247.

22. BubeckM.Renalclearancedeterminationwithonebloodsample:improvedaccuracyand universalapplicabilityby a new calculationprinciple.SeminNuciMed1993;23:73—86.

23. SapirsteinLA, Vidt DO, Mandel Mi, et at. Volumesof distributionandclearancesof intravenouslyinjectedcreatininein the dog.Am I Physiol1955;181:330—336.

24. Tauxe WN, Maher FT. Taylor WF. Effective renal plasma flow: estimationfrom theoreticalvolumesof distributionof intravenouslyinjected ‘@‘iorthoiodohippurate. Mayo C/in P@vc1971;46:524—531.

6. Russell CD, Thorstad B, Yester MV, et al. Quantitation of renal functionwith technetium-99m-MAG3. I NuciMed 1988;29:1931—1933.

7. TaylorAJr.ZifferJA,StevesA, etal.Evaluationof@―Tc-mercaptoacetyltriglycinein patientswith impairedrenalfunction.Radiology1987;162:365—370.

8. BubeckB, BrandauW, WeberE, et al. Pharmacokineticsof technetium99m-MAG3 in humans. JNuclMed 1990;31:1285—1293.

9. Taylor A Jr, Ziffer JA, Steves A, et al. Clinical comparison of 1311-orthoiodohippurateand the kit formulationof @“Fc-mercaptoacetyltriglycine. RadioIo@' 1989;170:721—725.

10. Stabin M, TaylorAir, Eshima D, et al. Radiationdosimetryfor technetium99m-MAG3,technetium-99m-DTPA,and iodine-131-OIHbased on humanbiodistribution studies. JNuclMed 1992;33:33—40.

11. Garnett ES, Parsons V. Veal N. Measurement of renal glomerular filtrationrate in man using a “Cr/edetic-acidcomplex. Lancet 1967;II:818—819.

12. HorG, PabstHW,SteinhoffH, et al. Untersuchungenzurclearancevon131 Hippuran, 203 Hg-Salyrgan, “Cr-EDTAund “Cr-inulin.RadioL@otopeLd. Kreislaufforschg 1968;8:327—332.

13. Brochner-Mortensen J, Giese J, Rossing N. Renal inulin clearance versustotalplasmaclearanceof―CrEDTA.ScandJClinLabInvest1969;23:301—305.

14. Brochner-Mortensen J. A simple method for the determination of glomerularfiltrationrate.Scandi CliiiLabInvest1972;30:271—274.

15. Fisher M, Veall N. Glomerular filtration rate estimation based on a singleblood sample. Bn:MedJ 1975;2:542.

16. Morgan WD, Birks JL, Sivyer A, et al. An efficienttechnique for the

1706 The Journalof NuclearMedicine•Vol.36 •No. 9 •September1995

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1995;36:1701-1706.J Nucl Med.   Giovanni F. Fresco, Flavia DiGiorgio and Giovanna L. Curti  Simultaneous Estimation of Glomerular Filtration Rate and Renal Plasma Flow

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