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RADIONUCLIDES METHODS IN VITROclearance measurement methodsRADIONUCLIDES METHODS IN VITROclearance measurement methods

Emmanuel DURANDEmmanuel DURAND

ISCORN, Mikulov, 2010Tuesday May 11th 1030-1130ISCORN, Mikulov, 2010Tuesday May 11th 1030-1130

Question 1

What is the best index for renal function?(one choice only)

A – renal sizeB – urine flowC – renal blood/plasma flowD – glomerular filtration rateE – filtration fraction

Question 1



Question 2

What is the best technique to assess glomerular filtration rate?(one choice only)

A – serum creatinine assayB – MDRD formulaC – blood urea nitrogenD – 99mTc-DMSA absolute uptakeE – plasma clearance of 51Cr-EDTA

Question 2



Question 3

Should we normalise GFR to body size?(one choice only)

A – no, neverB – yes, always, to body surface areaC – yes, most of the time, to body surface areaD – yes, always, to body weightE – yes, most of the time, to body weight

Question 3



Question 4

What could best characterise urine clearance measurements, as compared to plasma clearance measurements?(one choice only)

A – they are more precise and more accurateB – they are less precise but more accurateC – they are more precise but less accurateD – they are less precise and less accurateE – they are more precise and as accurate

Question 4



Question 5

In which circumstance(s) should you perform a urinary clearance measurement instead of a plasma clearance measurement?(potentially several answers)

A – in childrenB – in patients with œdema C – in patients with hyperfiltrationD – in patients with very low renal functionE – in patients with asymetrical renal function

Question 5



Question 6

What is the general formula for clearance?P: plasma concentration – U: urinary concentrationBW : body weight – V : urine flow – CO : cardiac output(one choice only)

A – P × U / VB – U × V / PC – U × V / BWD – (C × O / V ) × (P / U)E – P × V × U

Question 6



Question 7

How is the plasma clearance determined?(one choice only)

A – the urinary concentration divided by the plasma concentrationB – the area under the plasma time-concentration curve divided by the injected activityC – the area under the plasma time-concentration curve divided by the plasma concentration at time 0D – the injected activity divided by the area under the plasma time-concentration curveE – the injected activity divided by the area under the plasma time-concentration curve

Question 7



Question 8

When using two plasma samples for plasma clearance technique:(potentially several answers)

A – two exponentials must be determinedB – one exponential only can be determinedC – a correction formula must be used, the recommended one being published by Brochner and MortensenD – a correction formula must be used, the recommended one being published by Christensen and GrothE – there is no need for correction

Question 8



Clinical indications for renal clearance measurementsThe concept of renal clearance

renal functionclearanceglomerular

Methods of clearance measurementstracerstypes of clearancesurinary clearancecontinuous infusion plasma clearancesingle shot plasma clearancenormalisation for body size

Practical issues in measurementChoice of MethodInterpretation

normal valuesbody size scalingcase of children






E.Durand – ISCORN’2010 - Mikulov

CLINICAL INDICATIONSCLINICAL INDICATIONS

global function: clearancerelative function: renal scanindividual function: clearance + renal scan

global function: clearancerelative function: renal scanindividual function: clearance + renal scan

http://www.bio.psu.edu/people/faculty/strausshttp://www.bio.psu.edu/people/faculty/strauss

ED - ISCORN'2010 - Mikulov


• can a patient withstand nephrectomy (either for himself or as a kidney donor)• can a patient withstand nephrotoxic drugs (anti-tumoural chemotherapy)?• adapt drug dosage to renal function • detect mild renal insufficiency• renal function follow-up• prepare dialysis• can a patient stop dialysis?• how does a patient behaves under a drug (i.e. ACE inhibitors)• concept of glomerular functional reserve• determine hyperfiltration in diabetics

• can a patient withstand nephrectomy (either for himself or as a kidney donor)• can a patient withstand nephrotoxic drugs (anti-tumoural chemotherapy)?• adapt drug dosage to renal function • detect mild renal insufficiency• renal function follow-up• prepare dialysis• can a patient stop dialysis?• how does a patient behaves under a drug (i.e. ACE inhibitors)• concept of glomerular functional reserve• determine hyperfiltration in diabetics


concept of glomerular functional reserveconcept of glomerular functional reserve

After infusion of:• either Dopamin 2 µg/kg/min• or some amino-acids (Hyperamin 50 mL/hr)• or bothglomerular filtration rate increases by about 15%

After infusion of:• either Dopamin 2 µg/kg/min• or some amino-acids (Hyperamin 50 mL/hr)• or bothglomerular filtration rate increases by about 15%












CONCEPT: functionCONCEPT: function

best parameter to assess renal function =best parameter to assess renal function =

Glomerular Filtration Rate (GFR)Glomerular Filtration Rate (GFR)

Levey AS. Use of glomerular filtration rate measurements to assess the progression of renal diseaseSemin Nephrol 1989;9(4):370-9

Levey AS. Use of glomerular filtration rate measurements to assess the progression of renal diseaseSemin Nephrol 1989;9(4):370-9

• keep homeostasis (water, ions, )• excretion of toxic substances• metabolism (1-hydroxylation of vitamin D)• hormonal: erythropoietin, renin

• keep homeostasis (water, ions, )• excretion of toxic substances• metabolism (1-hydroxylation of vitamin D)• hormonal: erythropoietin, renin












CONCEPT: clearanceCONCEPT: clearance

FFrenal (arterial) plasma flowrenal (arterial) plasma flow renal (venous) plasma flowrenal (venous) plasma flow

F� F�

APAP

plasma (arterial) concentrationof a substanceplasma (arterial) concentrationof a substance

VPVP

plasma (venous) concentrationof the substanceplasma (venous) concentrationof the substance

extraction:extraction: 1A V V

A A

P P PEP P−

= = −1A V V

A A

P P PEP P−

= = −



FFrenal (arterial) plasma flowrenal (arterial) plasma flow renal (venous) plasma flowrenal (venous) plasma flow

F� F�200 mmol/L200 mmol/L

extraction:extraction: 200 50 501 75%200 200

E −= = − =200 50 501 75%200 200

E −= = − =

50 mmol/L50 mmol/L



FF F� F�APAP VPVP

AP F×AP F×substance arterial flowsubstance arterial flow

VP F×VP F×substance venous flowsubstance venous flow

urine flowurine flowVVurinary concentrationurinary concentrationUUsubstance urinary flowsubstance urinary flow

UVUV



AP F×AP F× VP F×VP F×substance arterial flowsubstance arterial flow substance venous flowsubstance venous flow

substance urinary flowsubstance urinary flowUVUV A VP F P F UV× − × =A VP F P F UV× − × =



A VP F P F UV× − × =A VP F P F UV× − × =

( )A VP P F UV− × =( )A VP P F UV− × =

A V

A

P PEP−

=A V

A

P PEP−

=

A V AP P E P− = ×A V AP P E P− = ×

AE P F UV× × =AE P F UV× × =

E F P UV× × =E F P UV× × =



500 mL/min200 mmol/L= 0.2 mmol/mL

AP F×AP F×substance arterial flowsubstance arterial flow

100 mmol/min.

50 mmol/L= 0.05 mmol/mL

VP F×VP F×substance venous flowsubstance venous flow

25 mmol/min.

1,5 mL/min= 2 L/day

50 mmol/mL(imaginary substance)

substance urinary flowsubstance urinary flowUVUV

75 mmol/min

E F P UV× × =E F P UV× × =

75%E =75%E =



ClearanceClearance U VCP×

=U VCP×

=

urinaryconcentration

urinaryconcentration

urinaryflow

urinaryflowmmol/Lmmol/L mL/minmL/min

plasmaconcentration

plasmaconcentration

mmol/Lmmol/L

mL/minmL/min



E F P UV× × =E F P UV× × =U VCP×

=U VCP×

=

E F PCP× ×

=E F PC

P× ×

=

C E F= ×C E F= ×

clearance is the kidney ability to extract the substancemultiplied by the kidney input i.e. plasma flow

the product corresponds to the kidney function



U VCP×

=U VCP×

=

50 mmol/mL50 mmol/mL 1.5 mL/min1.5 mL/min

200 mmol/L= 0.2 mmol/mL200 mmol/L= 0.2 mmol/mL

375 mL/min375 mL/min

75 mmol/min75 mmol/min

C E F= ×C E F= ×500 mL/min

75%



UC VP= ×UC VP= ×

50 mmol/mL50 mmol/mL

1.5 mL/min1.5 mL/min

0.2 mmol/mL0.2 mmol/mL

375 mL/min375 mL/min

urine is 250 times more concentrated than plasma 1 mL urine ‘cleans’ 250 mL plasma from substance

1.5 mL/min urine ‘cleans’ 250 x 1.5 = 375 mL/min plasma

clearance is the imaginary plasma flow cleared from substancei.e. kidney ability to ‘clean’ plasma from substance



Clearance : Clearance : U VC E FP×

= = ×U VC E FP×

= = ×

definition :imaginary plasma flow (volume per unit time)completely cleared from substance

definition :imaginary plasma flow (volume per unit time)completely cleared from substance

for a given organ:ability to take the subtance including the input function (perfusion)

= plasma flow × extraction

for a given organ:ability to take the subtance including the input function (perfusion)

= plasma flow × extraction



Clearance reflects renal functionas if the role of the kidney were to remove a substance from the blood(which is a shortcut)

Clearance reflects renal functionas if the role of the kidney were to remove a substance from the blood(which is a shortcut)












CONCEPT: glomerularCONCEPT: glomerular

A glomerular traceris a small molecule, freely filtered, not linked to proteinsnot secreted nor reabsorbed


its concentration in the plasma isits concentration in the plasma is PP

its concentration in the glomerular filtrate (primary urine) is alsoits concentration in the glomerular filtrate (primary urine) is also PP

its flow in the glomerular filtrate isits flow in the glomerular filtrate is GFRP×GFRP×

GFR GFRPCP×

= =GFR GFRPCP×

= =its clerance is thereforeits clerance is therefore

as it is not secreted nor reabsorbed, its flow in the final urine is also

as it is not secreted nor reabsorbed, its flow in the final urine is also GFRUV P= ×GFRUV P= ×


CONCEPT: glomerularCONCEPT: glomerular



Its clearance is the glomerular filtration rateIts clearance is the glomerular filtration rate











« Gold Standard »: Inulin (cold, exogenous)« Gold Standard »: Inulin (cold, exogenous)


METHODS: tracers (inulin)METHODS: tracers (inulin)

Exogenous cold tracer (former gold standard) = inulinExogenous cold tracer (former gold standard) = inulinfructose polymer (polyfructosan)extracted from Jerusalem artichokeconsidered as a gold standardthough, also cleared by other organsassays are not straightforwardno more widely available for in vivo human use

fructose polymer (polyfructosan)extracted from Jerusalem artichokeconsidered as a gold standardthough, also cleared by other organsassays are not straightforwardno more widely available for in vivo human use

Routine: Creatinine (cold, endogenous)Routine: Creatinine (cold, endogenous)


METHODS: tracers (creatinine)METHODS: tracers (creatinine)

Endogenous tracer used in clinical routine : creatinineEndogenous tracer used in clinical routine : creatinineendogeneous: no injection is neededproduced by protein catabolismproduction is not constant (muscles / food intake)not only filtered but secretedassays are not straightforward (many interferences)assay results strongly depends on technique

endogeneous: no injection is neededproduced by protein catabolismproduction is not constant (muscles / food intake)not only filtered but secretedassays are not straightforward (many interferences)assay results strongly depends on technique

CO

CO–

NH2

CO

CO–

NH2

CO

CH2

O–

NC

NH+2

NH2

CO

CH2

O–

NC

NH+2

NH2

CO CH2N

C

NH+2

NH

CO CH2N

C

NH+2

NH

amino acidsamino acids

creatinecreatine

creatininecreatinine


METHODS: tracers (creatinine)METHODS: tracers (creatinine)

Endogenous tracer used in clinical routine : creatinineEndogenous tracer used in clinical routine : creatinine

How to interpret creatinine assays?How to interpret creatinine assays?

• urinary creatinine clearance• urinary creatinine clearance• plasma creatinine only• plasma creatinine only

• plasma creatinine with formulaeCockroft and Gault, MDRD, Schwartz, Counahan-Barratt…

• plasma creatinine with formulaeCockroft and Gault, MDRD, Schwartz, Counahan-Barratt…

U VCP×

=U VCP×

=


Using only the MDRD formula is still debatedconsidered to be reliable within a ± 30% confidence inteval!unsuitable to children, elder people, obese, very thin, patients with advanced renal of hepatic insufficiency…

Using only the MDRD formula is still debatedconsidered to be reliable within a ± 30% confidence inteval!unsuitable to children, elder people, obese, very thin, patients with advanced renal of hepatic insufficiency…

Coresh. J Am Soc Nephrol 2002;13(11):2811-2.Agarwal R. Am J Kidney Dis 2005;45(3):610-3.Rule. Am J Kidney Dis 2004;43(1):112-9.

Coresh. J Am Soc Nephrol 2002;13(11):2811-2.Agarwal R. Am J Kidney Dis 2005;45(3):610-3.Rule. Am J Kidney Dis 2004;43(1):112-9.

radiotracers still have a roleradiotracers still have a role

METHODS: tracers (creatinine: formulæ)METHODS: tracers (creatinine: formulæ)

Radiopharmaceuticals: glomerularRadiopharmaceuticals: glomerular


GLOMERULAR TRACERSGLOMERULAR TRACERS

labelling MW filtrationfraction secretion extraction

coefficientproteinbinding

DTPAdiethylene pentacetic

acid

99mTc 169Yb113mIn140La

393 D 15-20% – 15-20% 0-10%

EDTAethylene-diamine-tetracetic acid

51Cr 292 D 15-20% – 15-20% <5%

iothalamate125I131I

COLD614 D 15-20% 10-20% 4-25%

diatrizoate 125I 636 D 15-20% –

²²

ideal: filtered, non-secreted, non reabsorbed, no protein bindingideal: filtered, non-secreted, non reabsorbed, no protein binding

METHODS: tracers (radiopharmaceuticals, glomerular)METHODS: tracers (radiopharmaceuticals, glomerular)


EDTAEDTA DTPADTPA



METHODS: tracersMETHODS: tracers

51Cr-EDTA (Ethylene-Diamine-TetrAcetate)51Cr-EDTA (Ethylene-Diamine-TetrAcetate)51Cr : T1/2 = 27,7 j CE + γ 320 keV (10%)no imaging, only clearancealready labeled in 1 mCi vialsexcellent in vitro and in vivo stabilitypresent gold standard(small extra-renal clearance ~ 4 mL/min.)

51Cr : T1/2 = 27,7 j CE + γ 320 keV (10%)no imaging, only clearancealready labeled in 1 mCi vialsexcellent in vitro and in vivo stabilitypresent gold standard(small extra-renal clearance ~ 4 mL/min.)

99mTc-DTPA (Diethylene-Tetramine-PentAcetate)99mTc-DTPA (Diethylene-Tetramine-PentAcetate)imaging and/or clearancescold kitgood in vitro and in vivo stabilityprotein binding should be checked for (depends on brand used)labeling yield (free Tc and reduced-hydrolysed Tc)

imaging and/or clearancescold kitgood in vitro and in vivo stabilityprotein binding should be checked for (depends on brand used)labeling yield (free Tc and reduced-hydrolysed Tc)


Among Glomerular tracers:• EDTA-51Cr is a tracer of choice (unavailable in the USA)• DTPA-99mTc is good provided protein binding is checked

(strong variations among preparations)

iothalamate is only a second choice (USA)it is also secreted

Among Glomerular tracers:• EDTA-51Cr is a tracer of choice (unavailable in the USA)• DTPA-99mTc is good provided protein binding is checked

(strong variations among preparations)

iothalamate is only a second choice (USA)it is also secreted

Rehling - Scand J Clin Lab Invest 1988; 48: 603Rehling - Nucl Med Commun 1997; 18: 324Brøchner – Clin Physiol 1985; 5: 1Carlsen – J Nucl Med 1980; 21: 126

Rehling - Scand J Clin Lab Invest 1988; 48: 603Rehling - Nucl Med Commun 1997; 18: 324Brøchner – Clin Physiol 1985; 5: 1Carlsen – J Nucl Med 1980; 21: 126



Other Glomerular Tracers…Other Glomerular Tracers…iodinated contrast media : Iohexol (OK if HPLC assays)

cold Iothalamateradiopharmaceuticals : labelled Iothalamate

Diatrizoate

iodinated contrast media : Iohexol (OK if HPLC assays)cold Iothalamate

radiopharmaceuticals : labelled IothalamateDiatrizoate













METHODS: types of clearancesMETHODS: types of clearances

plasma clearanceplasma clearance

urinary clearance(renal clearance)urinary clearance(renal clearance)

external countingexternal counting



timetime

bolus ("single shot")bolus ("single shot")

timetime

continuous infusioncontinuous infusion



timetime

single shotsingle shot

timetime







Methods of clearance measurementstracerstypes of clearancesurinary clearancecontinuous infusion plasma clearance single shot plasma clearancenormalisation for body size









METHODS: urinaryMETHODS: urinary

timetime

single shotsingle shot plasma clearanceplasma clearance



timetime


OR



U VGFRP×

=U VGFRP×

=

urinary concentrationurinary concentration

urinary flowurinary flow

plasma concentrationplasma concentration



U VCP×

=U VCP×

=10 00010 000

10001000

100100

1010time ttime t

plasma concentration Pplasma concentration P

micturition micturition (UV)1(UV)1 (UV)2(UV)2 (UV)3(UV)3 (UV)4(UV)4

P1P1P2P2

P3P3P4P4



In fact, any scheme of injection suits (IV, infusion, even SC)hydrate well (urine flow should exceed 3 mL/min)plasma samplingurine collectionindividual GFR determination for each collection periodvalue averaging (discard when flow < 1 mL/min)

In fact, any scheme of injection suits (IV, infusion, even SC)hydrate well (urine flow should exceed 3 mL/min)plasma samplingurine collectionindividual GFR determination for each collection periodvalue averaging (discard when flow < 1 mL/min)



exemple :exemple :

9h00 injection10h00 micturition (thrown away)10h30 plasma sampling11h00 micturition 11h30 plasma sampling12h00 micturition 12h30 plasma sampling13h00 micturition

9h00 injection10h00 micturition (thrown away)10h30 plasma sampling11h00 micturition 11h30 plasma sampling12h00 micturition 12h30 plasma sampling13h00 micturition

P1 = 1 200 cpm/mLU1 = 35 000 cpm/mL V1=52 mL/60 minP2 = 800 cpm/mLU2 = 20 000 cpm/mL V2=240 mL/60 minP3 = 600 cpm/mLU3 = 15 000 cpm/mL V3=180 mL/60 min


10 00010 000

10001000

100100

1010temps ttemps t

conc. plasmatique Pconc. plasmatique P

mictionmiction(UV)1(UV)1 (UV)2(UV)2 (UV)3(UV)3 (UV)4(UV)4

P1P1P2P2

P3P3P4P4





< 1 mL/min< 1 mL/min20 000 cpm/mL 4 mL/min

800 mL/minCl ×=20 000 cpm/mL 4 mL/min

800 mL/minCl ×= 100 mL/minCl =100 mL/minCl =

15 000 cpm/mL 3mL/min600 mL/minCl ×

=15 000 cpm/mL 3mL/min

600 mL/minCl ×= 75 mL/minCl =75 mL/minCl =

averaging 100 and 75 = 87 mL/minaveraging 100 and 75 = 87 mL/min



Urinary clearance is :Urinary clearance is :

accurate : no biais (no extrarenal clearance)accurate : no biais (no extrarenal clearance)

imprecise : scatter (urine collection is troublesome)imprecise : scatter (urine collection is troublesome)(experimental) gold standard =

urethral catheterisation+ bladder rinsing+ air exsufflation

(experimental) gold standard =urethral catheterisation+ bladder rinsing+ air exsufflation

accurateaccuratenot precisenot precise(like urinary cl.)(like urinary cl.)

preciseprecisenot accuratenot accurate

(like plasma cl.)(like plasma cl.)












METHODS: continuous infusion plasma clearance METHODS: continuous infusion plasma clearance

U VCP×

=U VCP×

=

instead of measuring the urine output, we measure the infusion inputinstead of measuring the urine output, we measure the infusion input

RCP=RCP= tracer outflow

in urinetracer outflow

in urinetracer inflowfrom infusiontracer inflowfrom infusion


METHODS: continuous infusion plasma clearance METHODS: continuous infusion plasma clearance plasma concentrationplasma concentration

timetime

flowplateauGFR = flowplateauGFR =

at the plateau,input = outputat the plateau,input = output

U VCP×

=U VCP×

=RCP=RCP=



RCP=RCP=

500 c 100 mL/mipm / mL50 000 cpm / min nGFR = =500 c 100 mL/mipm / mL50 000 cpm / min nGFR = =

100 000 cpm / mL0,5 mL / minR = 50 000 cpm / min

100 000 cpm / mL0,5 mL / minR = 50 000 cpm / minP = 500 cpm / mLP = 500 cpm / mL



In practice:In practice:

• roughly estimate GFR from creatinine• inject a loading dose (22 kBq/kg BW)• then infuse with constant flow (7 kBq/[ml/min GFR])• plasma sampling between 1½ et 4 h after the infusion start• no need for accurate timing• urine collection is required if GFR<15 mL/min or ascites or oedema• the infusion solution is calibrated by “infusing” tubes

• roughly estimate GFR from creatinine• inject a loading dose (22 kBq/kg BW)• then infuse with constant flow (7 kBq/[ml/min GFR])• plasma sampling between 1½ et 4 h after the infusion start• no need for accurate timing• urine collection is required if GFR<15 mL/min or ascites or oedema• the infusion solution is calibrated by “infusing” tubes



☺☺

��

• nearly no possible error (very robust)• dynamic (baseline+test condition are feasible)

(glomerular reserve/ACE inhibitors…)• precise• can be used with a urinary clearance

• nearly no possible error (very robust)• dynamic (baseline+test condition are feasible)

(glomerular reserve/ACE inhibitors…)• precise• can be used with a urinary clearance

• requires a several hour infusion• impurities may accumulate in the plasma• cumbersome ?

• requires a several hour infusion• impurities may accumulate in the plasma• cumbersome ?

• no precise timing needed• standard calibration is very easy and robust• trained nurses find it no more time-consuming than single-shot clearance

• no precise timing needed• standard calibration is very easy and robust• trained nurses find it no more time-consuming than single-shot clearance











Single injection plasma clearanceSingle injection plasma clearance

general principlefull sampling (two-exponential)slope-intercept (single-exponential)single pointslope-only


ED - ISCORN'2010 - Mikulov ED - ISCORN'2010 - Mikulov

METHODS: bolus injection plasma clearance METHODS: bolus injection plasma clearance

( ) ( )( )

U t V tUVCP P t

×= =

( ) ( )( )

U t V tUVCP P t

×= =

( ) ( ) ( )tracer flow in urine

C P t U t V t× = ×14243

( ) ( ) ( )tracer flow in urine

C P t U t V t× = ×14243

( ) ( ) ( )0 0

C P t dt U t V t dt q∞ ∞

× = × =∫ ∫( ) ( ) ( )0 0

C P t dt U t V t dt q∞ ∞

× = × =∫ ∫

( )0

injected activityarea under the plasma time-activity curve

qCP t dt∞= =

∫ ( )0

injected activityarea under the plasma time-activity curve

qCP t dt∞= =

∫

( )0

C P t dt q∞

× =∫ ( )0

C P t dt q∞

× =∫



( )0

qClP t dt+∞

= ∫ ( )0

qClP t dt+∞

= ∫QQ

plasma activityplasma activity

timetime








two compartiment,openmamillarysystem

two compartiment,openmamillarysystemplasmaplasma

interstitialspace

interstitialspace

removal by kidneyremoval by kidney

Theory predicts that:Theory predicts that:( )

fast component slow component

t tP t A e B eα β− −= ⋅ + ⋅123 123

( )fast component slow component

t tP t A e B eα β− −= ⋅ + ⋅123 123




t tP t A e B eα β− −= ⋅ + ⋅123 123


t tP t A e B eα β− −= ⋅ + ⋅123 123

Exact technique:• take >> 4 samples• fit model curve (2 exp.) to experimental data• determine the four parameters: A, B, α, β• calculate the integral:

• infer clearance

Sapirstein – Am J Physiol 1955; 181: 330

Exact technique:• take >> 4 samples• fit model curve (2 exp.) to experimental data• determine the four parameters: A, B, α, β• calculate the integral:

• infer clearance

Sapirstein Sapirstein –– Am J Physiol 1955; 181: 330Am J Physiol 1955; 181: 330

0

A BP α β∞

= +∫0

A BP α β∞

= +∫

0

q qC A BP α β∞= =

+∫0


+∫



fast removalsmall areahigh function

fast removalsmall areahigh function

( )0

qClP t dt+∞

= ∫ ( )0

qClP t dt+∞

= ∫slow removallarge arealow function

slow removallarge arealow function



( ) ( )7

-15 -1

0

10 cpm 100 mL min10 cpm mL minqClP t dt+∞

= = = ⋅⋅ ⋅∫ ( ) ( )7

-15 -1

0

10 cpm 100 mL min10 cpm mL minqClP t dt+∞

= = = ⋅⋅ ⋅∫

Express injected activity in the same way as the activity per unit of volume, usually detected activity:i.e. counts per minute (cpm) but might be Bq, g, mol…

Express injected activity in the same way as the activity per unit of volume, usually detected activity:i.e. counts per minute (cpm) but might be Bq, g, mol…



countingcountingcounting

patientpatientpatient

standardstandardstandard

For this, use a ‘standard’: known volume of water, ‘injected’ like the patientcounted like the patient’s plasma.



Calibration needs comparison between injected activities(patient/standard)

( )0

qClP t dt+∞

= ∫ ( )0

qClP t dt+∞

= ∫countingcountingcountingpatientpatientpatient

standardstandardstandard

e.g. 10 000 000 cpme.g. 10 000 000 cpm

e.g. 3 000 cpm/mL at time te.g. 3 000 cpm/mL at time t



ratio by comparing: • masses• or volumes• or activities

ratio by comparing: ratio by comparing: •• massesmasses•• or volumesor volumes•• or activitiesor activities

Calibration needs comparison between injected activities(patient/standard)

( )0

qClP t dt+∞

= ∫ ( )0

qClP t dt+∞

= ∫



In practice, for the two-exponential technique :• sample from 5-10 min. post injection• up to 3-24 h according to expected renal function• 8 samples is good• cumbersome � alleviate burden is desirable

… simplified techniques!







tt B eeP t A βα −−= ⋅ + ⋅123 123


tt B eeP t A βα −−= ⋅ + ⋅123 123

( )slow component

tP t B e β−= ⋅123

( )slow component

tP t B e β−= ⋅123

Mono-exponential technique (‘slope-intercept’)Mono-exponential technique (‘slope-intercept’)

××××

late sampling onlyuse only one exponentialcompensate for neglecting the first exponential

late sampling onlyuse only one exponentialcompensate for neglecting the first exponential



( )0

qClP t dt+∞

= ∫ ( )0

qClP t dt+∞

= ∫


tt B eeP t A βα −−= ⋅ + ⋅123 123


tt B eeP t A βα −−= ⋅ + ⋅123 123

( )slow component

tP t B e β−= ⋅123

( )slow component

tP t B e β−= ⋅123

The measured P(t) is lower than the true P(t)Denominator is underestimatedClearance is overestimatedCalculated clearance should be reducedThe higher the renal function, the higher the error

The measured P(t) is lower than the true P(t)Denominator is underestimatedClearance is overestimatedCalculated clearance should be reducedThe higher the renal function, the higher the error


METHODS: bolus injection plasma clearance METHODS: bolus injection plasma clearance Calculated clearance should be corrected (reduced):Calculated clearance should be corrected (reduced):

• multiply by a number < 1 (Chantler):0.93 for adults / 0.87 for children

• use a 2nd degree formula: ax²+bx (Brøchner-Mortensen)• use a more physiologiocal formula (recommended)

Flemingimproved by Jødal and Brøchner-Mortensen

• multiply by a number < 1 (Chantler):0.93 for adults / 0.87 for children

• use a 2nd degree formula: ax²+bx (Brøchner-Mortensen)• use a more physiologiocal formula (recommended)

Flemingimproved by Jødal and Brøchner-Mortensen

corrected uncorrecteduncorrected

11

Cl Cl Clf=+ ×

corrected uncorrecteduncorrected

11

Cl Cl Clf=+ ×

0.65 1.30.0032 mf BSA−= ×0.65 1.30.0032 mf BSA−= ×

Scand J Clin Lab Invest 69:305 – Nucl Med Comm 28:315 Scand J Clin Lab Invest 69:305 – Nucl Med Comm 28:315 Fleming: same assuming BSA is 1.33 m²(calculation after normalisation to BSA)Fleming: same assuming BSA is 1.33 m²(calculation after normalisation to BSA)

here the clearance values are not normalised to BSAhere the clearance values are not normalised to BSA



In practice, for slope-intercept technique (mono-exponential):• sample 2-4 samples starting no earlier than 60-90 min• fit the plasma activity decay to a single exponential• calculate the uncorrected clearance value

• compensate for single exponential (preferably with Jødal formula)

In practice, for slope-intercept technique (mono-exponential):• sample 2-4 samples starting no earlier than 60-90 min• fit the plasma activity decay to a single exponential• calculate the uncorrected clearance value

• compensate for single exponential (preferably with Jødal formula)

0


+∫0


+∫0

q qC BPβ

∞= =

∫0

q qC BPβ

∞= =

∫0

q qC BP β∞= =

∫0

q qC BP β∞= =

∫



With slope-intercept technique, at least two-samples are required.Can it be simplified further?In principle, no! Two unknowns: ECV and GFR so two samples are needed.

However, if one makes an assumption about ECV, GFR can then be inferred with only one sample:this is the principle of single-sample techniques.

With slope-intercept technique, at least two-samples are required.Can it be simplified further?In principle, no! Two unknowns: ECV and GFR so two samples are needed.

However, if one makes an assumption about ECV, GFR can then be inferred with only one sample:this is the principle of single-sample techniques.






Sampling at time t.Plasma concentration of tracer is P(t).Nearly all these single sample-technique use the following intermediate parameter: apparent dilution volume:

The higher the plasma concentration,the smaller the volumethe smaller the clearance.

Sampling at time t.Plasma concentration of tracer is P(t).Nearly all these single sample-technique use the following intermediate parameter: apparent dilution volume:

The higher the plasma concentration,the smaller the volumethe smaller the clearance.

( ) ( )DqV t P t=( ) ( )DqV t P t=



Adults Fisher and Veall 1975Morgan 1977Constable 1979Jacobsson 1983Russel 1985Christensen and Groth 1986d° simplified by Watson 1992

Adults Fisher and Veall 1975Morgan 1977Constable 1979Jacobsson 1983Russel 1985Christensen and Groth 1986d° simplified by Watson 1992

Children Groth 1984Tauxe 1987Ham and Piepsz 1991

Children Groth 1984Tauxe 1987Ham and Piepsz 1991

General Waller 1987 Russell 1985Fleming 2005

General Waller 1987 Russell 1985Fleming 2005

Many formulæ were published (most were empirical):Many formulæ were published (most were empirical):


METHODS: bolus injection plasma clearance METHODS: bolus injection plasma clearance If we assume a single-exponential decay: If we assume a single-exponential decay: ( ) tP t B e β−= ⋅( ) tP t B e β−= ⋅

( ) ( )00Dq qECV V P B= = =( ) ( )00Dq qECV V P B= = =

( )0P B=( )0P B=

( ) ( )D t ttqB

ECV

q q q ECVV t P t e eeβ ββ− −

−

= = = =⋅

⋅

( ) ( )D t ttqB

ECV

q q q ECVV t P t e eeβ ββ− −

−

= = = =⋅

⋅

qB ECV=qB ECV=

( )lnD

ECVtV t

β− = ( )lnD

ECVtV t

β− = ( )lnD

ECVV tt

β−

=( )lnD

ECVV tt

β−

=( )t

D

ECVeV t

β−= ( )

t

D

ECVeV t

β−=


METHODS: bolus injection plasma clearance METHODS: bolus injection plasma clearance If we assume a single-exponential decay: If we assume a single-exponential decay: ( ) tP t B e β−= ⋅( ) tP t B e β−= ⋅

( ) ( )00Dq qECV V P B= = =( ) ( )00Dq qECV V P B= = =

( )0P B=( )0P B=

( ) ( )D t tt

q q q ECVV t qP t B e eeECVβ ββ− −

−

= = = =⋅

⋅

( ) ( )D t tt

q q q ECVV t qP t B e eeECVβ ββ− −

−

= = = =⋅

⋅

qB ECV=qB ECV=

( )t

D

ECVeV t

β−= ( )

t

D

ECVeV t

β−= ( )ln

D

ECVtV t

β− = ( )lnD

ECVtV t

β− = ( )lnD

ECVV tt

β−

=( )lnD

ECVV tt

β−

=

( ) ( )lnln DDq ECVE V tGF

ER ECV t

V VtB

CV

t Cβ= = = + ×−

( ) ( )lnln DDq ECVE V tGF

ER ECV t

V VtB

CV

t Cβ= = = + ×−

qECV B=qECV B=

Jacobsson 1983 Clin Physiol 3 297-305Jacobsson 1983 Clin Physiol 3 297-305

qGFR Bβ

=qGFR Bβ

=


METHODS: bolus injection plasma clearance METHODS: bolus injection plasma clearance Assuming ECV, Christensen and Groth devised a technique,which was simplified by Watson to get the same resultThe technique reduces in solving a 2nd degree equation*:

Assuming ECV, Christensen and Groth devised a technique,which was simplified by Watson to get the same resultThe technique reduces in solving a 2nd degree equation*:

Christensen & Groth – Clin Physiol 1986; 6: 579Christensen & Groth Christensen & Groth –– Clin Physiol 1986; 6: 579Clin Physiol 1986; 6: 579

2 42

b b acGFRa

− + −=

2 42

b b acGFRa

− + −=

• recommended by the international consensus (Blaufox, Santa Fe, 1996)•• recommended by the international consensus (Blaufox, Santa Fe, recommended by the international consensus (Blaufox, Santa Fe, 1996)1996)

Watson – Eur J Nucl Med 1992; 19: 827Watson Watson –– Eur J Nucl Med 1992; 19: 827Eur J Nucl Med 1992; 19: 827

( )( )

-6 2

-4 2

1.710 t - 0.0012 t-7.7510 t +1.31 tln D

abc ECV V t ECV

= × × = × × = × ( )( )

-6 2

-4 2

1.710 t - 0.0012 t-7.7510 t +1.31 tln D

abc ECV V t ECV

= × × = × × = ×28116.6 mL/m 28.2 mLECV BSA≅ × −28116.6 mL/m 28.2 mLECV BSA≅ × −

2 0ax bx c+ + =2 0ax bx c+ + =


METHODS: bolus injection plasma clearance METHODS: bolus injection plasma clearance For children:For children:

( )2.602 120 min 0.273DGFR V= × −( )2.602 120 min 0.273DGFR V= × −

Ham and Piepsz 1991 J Nucl Med 32 1294-1297 Ham and Piepsz 1991 J Nucl Med 32 1294-1297

showed good precisioneven if empirical formula. showed good precisioneven if empirical formula.

( ) 21.73 mln Da b V tBSAGFR

t

+ × × =( ) 21.73 mln Da b V t

BSAGFRt

+ × × =

11297 4 883 41.95 862 1282 15.5

a BSA tb BSA t= − − × − ×

= + × + ×

11297 4 883 41.95 862 1282 15.5

a BSA tb BSA t= − − × − ×

= + × + ×

ororFleming et al 2005 Nucl Med Comm 26 743-748Fleming et al 2005 Nucl Med Comm 26 743-748



Can we go further and determine GFR without even any plasma sample?

Can we go further and determine GFR without even any plasma sample?

…unfortunately no!…unfortunately no!






A few techniques were proposed using the slope only:GalliPeters

These techniques have not been validated.

A few techniques were proposed using the slope only:GalliPeters

These techniques have not been validated.

Peters - Nephrol Dial Transplant 1992; 7: 205Peters Peters -- Nephrol Dial Transplant 1992; 7: 205Nephrol Dial Transplant 1992; 7: 205



Gamma-camera techniques (e.g. Gates, absolute DMSA,…):good for relative measurementsnot recommended for absolute measurements (Blaufox et al - J Nucl Med 1996; 37: 1883-1890, consensus)+ many experimental studies

no more precise than creatinine-based techniques

Gamma-camera techniques (e.g. Gates, absolute DMSA,…):good for relative measurementsnot recommended for absolute measurements (Blaufox et al - J Nucl Med 1996; 37: 1883-1890, consensus)+ many experimental studies

no more precise than creatinine-based techniques












CHOICE OF METHODCHOICE OF METHOD

timetime

single shotsingle shot

timetime



urinary clearance(renal clearance)

urinary clearance(renal clearance)


• EDTA or DTPA?• plasma or urinary• single-shot or infusion• how many samples?• when sampling?

• EDTA or DTPA?• plasma or urinary• single-shot or infusion• how many samples?• when sampling?


CHOICE OF METHODCHOICE OF METHODFirst of all, collect information:• indication• age• body mass• height• gender• plasma creatinine • presence of œdema/ascitis/3rd compartment• (urea)• (Black?)• (albumin)

and estimate GFR from creatinine(MDRD in adults / Schwartz in children)

ensure steady-state conditions

First of all, collect information:• indication• age• body mass• height• gender• plasma creatinine • presence of œdema/ascitis/3rd compartment• (urea)• (Black?)• (albumin)

and estimate GFR from creatinine(MDRD in adults / Schwartz in children)

ensure steady-state conditions



EDTA or DTPA?both are goodDTPA can also be used for scanningEDTA is a very stable tracerDTPA should be checked for protein binding

EDTA or DTPA?both are goodDTPA can also be used for scanningEDTA is a very stable tracerDTPA should be checked for protein binding



plasma or urinary?Plasma is more preciseBut urinary is more accurate and mandatory if any of:

• expected GFR < 25 mL/min/1.73 m²• ascites• œdema• third compartment

plasma or urinary?Plasma is more preciseBut urinary is more accurate and mandatory if any of:

• expected GFR < 25 mL/min/1.73 m²• ascites• œdema• third compartment



single-shot or infusion?Single-shot is the most widely usedBut continuous infusion is needed for:

• assessment of glomerular functional reserve• assessment of GFR variations over various conditions

(ACE inhibitors…)Continuous infusion is very robust (kidney donors)

single-shot or infusion?Single-shot is the most widely usedBut continuous infusion is needed for:

• assessment of glomerular functional reserve• assessment of GFR variations over various conditions

(ACE inhibitors…)Continuous infusion is very robust (kidney donors)



When single-shot is chosen1 sample is precise but it is not robust

(international consensus: Christensen & Groth / Watson)

2+ samples is more robust(British consensus: single-exponential + Brochner-Mortensen)2 samples make it possible to check VEC3 samples show if 3 points are not aligned4+ samples make it possible to exclude an aberrant pointadding samples does not increase precision much

When single-shot is chosen1 sample is precise but it is not robust

(international consensus: Christensen & Groth / Watson)

2+ samples is more robust(British consensus: single-exponential + Brochner-Mortensen)2 samples make it possible to check VEC3 samples show if 3 points are not aligned4+ samples make it possible to exclude an aberrant pointadding samples does not increase precision much



When to sample?For single exponential: from 90 minutes post injectionFor last sampleIf expected GFR > 90 mL/min/1.73 m² up to 3 hr

> 60 mL/min/1.73 m² up to 4 hr> 40 mL/min/1.73 m² up to 5 hr< 40 mL/min/1.73 m² up to 24 hr

When to sample?For single exponential: from 90 minutes post injectionFor last sampleIf expected GFR > 90 mL/min/1.73 m² up to 3 hr

> 60 mL/min/1.73 m² up to 4 hr> 40 mL/min/1.73 m² up to 5 hr< 40 mL/min/1.73 m² up to 24 hr



sample early (<4 h)if function expected normalsample early (<4 h)if function expected normal

sample late (> 5h)if function expected lowsample late (> 5h)if function expected low



If I want to start, what technique should I use in most cases?If I want to start, what technique should I use in most cases?

plasma clearance51Cr-EDTA3 samplessingle-exponential model (slope intercept)Jødal and Brøchner-Mortensen correction formula

plasma clearance51Cr-EDTA3 samplessingle-exponential model (slope intercept)Jødal and Brøchner-Mortensen correction formula












INTERPRETATION: normal valuesINTERPRETATION: normal values

Piepsz, Eur. J. nucl. med. mol. imag. 2006; 33:1477Piepsz, Eur. J. nucl. med. mol. imag. 2006; 33:1477

normal values are difficult to establish:• who is normal?• is a normal truly normal?• why carrying out a clearance measurement if a subject is normal?• which technique was used (tracer/type of clearance/technique details)• is GFR is the same in different populations?

normal values are difficult to establish:• who is normal?• is a normal truly normal?• why carrying out a clearance measurement if a subject is normal?• which technique was used (tracer/type of clearance/technique details)• is GFR is the same in different populations?


INTERPRETATION : normal valuesINTERPRETATION : normal values



INTERPRETATION : normal valuesINTERPRETATION : normal values

Gender difference is debated:

men : 127 ± 23 ml/min/1.73 m²women : 118 ± 16 ml/min/1.73 m² or no significant difference

Gender difference is debated:

men : 127 ± 23 ml/min/1.73 m²women : 118 ± 16 ml/min/1.73 m² or no significant difference

Blake Nucl Med Commun 2005;26:983-7.Blake Nucl Med Commun 2005;26:983-7.2-17 years: GFR= 110 ± 17 mL/min/1.73 m²2-17 years: GFR= 110 ± 17 mL/min/1.73 m²

adults: GFR= 103 ± 16 mL/min/1.73 m²adults: GFR= 103 ± 16 mL/min/1.73 m²Grewal Nucl Med Commun 2005;26:61-5.Grewal Nucl Med Commun 2005;26:61-5.

Various normal ranges, dependant:• on technique• on tracer• on population

Various normal ranges, dependant:• on technique• on tracer• on population


INTERPRETATION: : normal valuesINTERPRETATION: : normal values


in ederly people : - 1 ml/min/1.73 m² / yron the average (much scatter)

pregnancy : + 30%after eating meat

or after dopamin-hyperamine infusion : + 15-20% (glomerular reserve)nycthemeral cycle : increased during the dayafter nephrectomy : progressive recovery (50�70%)

(in ca. 6 months)

in ederly people : - 1 ml/min/1.73 m² / yron the average (much scatter)

pregnancy : + 30%after eating meat

or after dopamin-hyperamine infusion : + 15-20% (glomerular reserve)nycthemeral cycle : increased during the dayafter nephrectomy : progressive recovery (50�70%)

(in ca. 6 months)


INTERPRETATION: : normal valuesINTERPRETATION: : normal values

Lines - Historical normal rangePoints – Grewal et al, 2005 Nucl Med Comm












INTERPRETATION: scalingINTERPRETATION: scaling

normal GFR is supposed to be proportionnal to BSAnormal GFR is supposed to be proportionnal to BSA

Dubois – Arch. Int. Med. 1916 ;17 :863Dubois – Arch. Int. Med. 1916 ;17 :8632

3 0.725 0.4257.18410 cm kgmBSA Height Weight−= × ×23 0.725 0.4257.18410 cm kgmBSA Height Weight−= × ×

to determine renal function: YES!GFR in mL/min./1.73 m²

to determine renal function: YES!GFR in mL/min./1.73 m²

to adapt a medication dosage: NO!GFR in mL/min

(the absolute clearance is what mattersto clear the drug)

to adapt a medication dosage: NO!GFR in mL/min

(the absolute clearance is what mattersto clear the drug)

Improved formulæ: Haycock…Improved formulæ: Haycock…



Scaling must be done to assess the degree of renal functionScaling must not be done to determine high toxicity drug dosageScaling must be done to assess the degree of renal functionScaling must not be done to determine high toxicity drug dosage

eg : a GFR of 40 mL/mineg : a GFR of 40 mL/min

in an adult of 1.73 m² BSA168 cm – 63 kg

nGFR = 40 mL/min/1.73 m²is abnormal (stage 3)

carboplatin scaled to 40 mL/min

in an adult of 1.73 m² BSA168 cm – 63 kg

nGFR = 40 mL/min/1.73 m²is abnormal (stage 3)

carboplatin scaled to 40 mL/min

in a child of 0.56 m² BSA90 cm – 12 kg

nGFR = 123 mL/min/1.73 m²is normal

carboplatin scaled to 40 mL/minNOT TO 123 mL/min (adult dosage)

in a child of 0.56 m² BSA90 cm – 12 kg

nGFR = 123 mL/min/1.73 m²is normal

carboplatin scaled to 40 mL/minNOT TO 123 mL/min (adult dosage)

=

≠


Scaling to ECV was proposed, reducing the equations to a slope-only technique

This in only an approximation and remains quite controversial.

Scaling to ECV was proposed, reducing the equations to a slope-only technique

This in only an approximation and remains quite controversial.

Peters - Nephrol Dial Transplant 1992; 7: 205Peters Peters -- Nephrol Dial Transplant 1992; 7: 205Nephrol Dial Transplant 1992; 7: 205












INTERPRETATION: childrenINTERPRETATION: children



INTERPRETATION: childrenINTERPRETATION: children

normal GFR (2-15 years) : 104 ± 20 mL/min/1.73 m²(normal range ~ 64 – 144 mL/min/1.73 m²)

normal GFR (2-15 years) : 104 ± 20 mL/min/1.73 m²(normal range ~ 64 – 144 mL/min/1.73 m²)

0 months 52 ± 9 mL/min/1.73 m²1-4 months 62 ± 14 mL/min/1.73 m²4-8 months 72 ± 14 mL/min/1.73 m²8-12 months 83 ± 17 mL/min/1.73 m²12-18 months 92 ± 18 mL/min/1.73 m²18-24 months 95 ± 18 mL/min/1.73 m²

0 months 52 ± 9 mL/min/1.73 m²1-4 months 62 ± 14 mL/min/1.73 m²4-8 months 72 ± 14 mL/min/1.73 m²8-12 months 83 ± 17 mL/min/1.73 m²12-18 months 92 ± 18 mL/min/1.73 m²18-24 months 95 ± 18 mL/min/1.73 m²

considered as renal maturation(or would is just be a scaling artefact?)considered as renal maturation(or would is just be a scaling artefact?)

To conclude…To conclude…routine technique = plasma creatinine with MDRD/Schwartz formula but:• poor technique to detect renal diseases at early stage• many assay techniques, with different results• not precise (± 30 mL/min/1.73 m²)• not adapted to all patients (obese, diabetic, liver disease…)

routine technique = plasma creatinine with MDRD/Schwartz formula but:• poor technique to detect renal diseases at early stage• many assay techniques, with different results• not precise (± 30 mL/min/1.73 m²)• not adapted to all patients (obese, diabetic, liver disease…)

PoggioJ Am Soc Nephrol 200516:459

PoggioJ Am Soc Nephrol 200516:459

To conclude…To conclude…

Camera-based methods without blood sampling are not more preciseThey must be used for relative renal function assessmentDTPA/EDTA Clearance measurements* are precise (± 5 mL/min/1.73 m²)High care must be taken at all stages of the technique to get such a precisionRadiation burden is very low (~ 20 µSv for EDTA)Cold Iohexol clearance is a second-hand choice

Camera-based methods without blood sampling are not more preciseThey must be used for relative renal function assessmentDTPA/EDTA Clearance measurements* are precise (± 5 mL/min/1.73 m²)High care must be taken at all stages of the technique to get such a precisionRadiation burden is very low (~ 20 µSv for EDTA)Cold Iohexol clearance is a second-hand choice

* reference technique is bi-exponential* reference technique is bi-exponential

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A – the urinary concentration divided by the plasma concentrationB – the area under the plasma time-concentration curve divided by the injected activityC – the area under the plasma time-concentration curve divided by the plasma concentration at time 0D – the injected activity divided by the area under the plasma time-concentration curveE – the plasma concentration at time 0 by the area under the plasma time-concentration curve

Question 8



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