Renal Scintigraphy

1
Renal Scintigraphy

• Ghee Chew

2
Renal Physiology

• Glomerulus
• Filtration
• Convoluted Tubule
• Secretion
• Absorption
• Metabolism

3
Renal Autoregulation

• Macula densa detects low flow
• Juxtaglomerular Apparatus signaled to release
  renin

4
Renin Angiotensin System

• Angiotensinogen
• Renin
• Angiotensin I
• Angiotensin Converting Enzyme (ACE)
• Angiotensin II

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ACE Inhibitors

• ACE I e.g captopril
• Angiotensin II Receptor Antagonist e.g.
  irbesartan
• Efferent arterioles gt Afferent arterioles
• Result drop in glomerular filtration pressure
• Drop in GFR if limited renal reserve and limited
  auto regulation - e.g. renal ischaemia

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Captopril / Baseline Renal Scan

• To look for renal vascular disease as a cause of
  hypertension
• Effect of captopril on GFR
• Deconvolution analysis to assess cortical transit
  time

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Renal Function Measurement

• Glomerular Filtration Rate
• Effective Renal Blood Flow

8
Glomerular Filtration Rate

• Requires agent which is filtered, not absorbed /
  secreted / metabolised
• Inulin
• Creatinine

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Glomerular Filtration Rate

• 99mTc DTPA
• various mathematical models
• Russell 1 point 180 minute
• Russell 2 point 60 and 180 minute
• Jackson urinary GFR
• Gates renal cortical uptake GFR
• 51Cr EDTA

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Effective Renal Blood Flow

• Requires agent with a high renal extraction ratio
• Para amino hippuric acid
• Radiopharmaceuticals
• 123I orthoiodohippurate
• 99mTc MAG 3

11
Renal Transplant Scans

• Post operative complications
• Rejection
• Acute tubular necrosis
• Drug toxicity
• Ischaemia / infarction
• Urinary leak
• Infection / primary disease recurrence

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Slope Ratio
Tx
Ia
Slope Ratio max slope Ia / max slope Tx
13
Hilsens Index
Tx
Ia
Hilsens Index area to peak Ia / Tx area to
peak
14
QEH Index

Tx
Ia
QEH index Ia peak count / max slope Tx
15
The End
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Deconvolution Analysis
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What Is Deconvolution Analysis?

• In the ideal setting, a perfect bolus is
  administered into the renal artery and the kidney
  is scanned. The time activity curves will look
  like

Perfect bolus Artery curve
Perfect bolus Renal curve R
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What Is Deconvolution Analysis?

• In reality, the radiopharmaceutical is
  administered into a peripheral or central vein.
  The Time activity curves appear like this

Imperfect Bolus Artery curve I
Imperfect Bolus Renal Curve O
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What Is Deconvolution Analysis?

• Theory of Convolution
• O I () R
• whereby
• I input function iliac artery activity
  curve
• O output function transplant activity curve
• R system response function ideal transplant
  activity curve
• () convolution function

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What Is Deconvolution Analysis?

• Deconvolution the process by which the
  convolution process is reversed.
• Using the fundamental theorem of Fourier
  Analysis, the Fourier transforms of the output
  function (FO(t) ) is simply the product of the
  individual Fourier transforms of the input
  (FI(t)) and system-response (FR(t))
  functions.
• ie FO(t) FI(t) . FR(t)

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What Is Deconvolution Analysis?

• Thus using inverse Fourier transformation, the
  system response function is obtained
• ie R(t) F-1 FO(t) / FI(t)
• Thus theoretically, deconvolution should
  eliminate the contribution by the variability of
  the bolus quality to the distortion of scan
  results.