radio nucleotide imaging

1. NUCLEAR RENAL IMAGING IN
UROLOGY

2. Introduction
Aimed to measure renal function with
radiopharmaceuticals.
Functional and anatomic information
Range varies from
urine counting and crude probe detectors
measurements of plasma clearance, dynamic functional
imaging
Single-photon emission computed tomography
(SPECT) cortical imaging.

3. Indications
 Blood flow abnormalities
 Function quantification and Differential function
 Glomerular filtration rate, effective renal plasma flow
 Mass vs. column of Bertin
 Obstruction: Uteropelvic junction, ureteral
 Pyelonephritis
 Renal failure: Acute and chronic
 Renovascular hypertension/renal artery stenosis
 Renal vein thrombosis
 Surgical complications
 Transplant rejection and anastomosis assessment
 Trauma
 Vesicoureteral reflux
 Volume quantification: Bladder residual volume

4. Physiology
Normally, the kidneys receive 20% of cardiac output,
with renal plasma flow (RPF) averaging 600 mL/min
 Clearance (mL/min) = Urine concentration (mg/mL) × Urine flow
(mL/min) / Plasma concentration (mg/mL)
Plasma clearance occurs by glomerular filtration and
tubular secretion

5. Clearence
First pass extraction is
usually < 100%, the term
effective renal plasma flow
(ERPF) is used to describe
the measurement
~20% of RPF (120
mL/min) is filtered through
the semipermeable
membrane of the
glomerulus
Tubular secretion accounts
for 80% of renal plasma
clearance

6. NUCLEAR SCINTIGRAPHY
TECHNIQUES
2D Scintigraphy - use of internal radionuclides to create
two-dimensionalimages.
3D SPECT - tomographic technique using gamma camera
data from many projections and reconstructed in different
planes
HYBRID SCAN - SPECT/CT and PET/CT

7. Renal Radiopharmaceuticals
Are Classified by their uptake and clearance
mechanisms as
agents for glomerular filtration
Tubular secretion
Cortical binding.

8. Agents Used to Quantify
For GFR
C-14 or H-3 inulin
I-125 diatrizoate
I-125 iothalamate
Co-57 vitamin B12
Cr-51 EDTA
In-111 or Yb-169 DTPA
Tc-99m DTPA
For ERPF
H-3 or C-14
paraaminohippurate
(PAH)
I-125 or I-131
iodopyracet
I-123, or I-
131orthoiodohippurate
(hippuran)
Tc-99m
mercaptoacetyltriglycine
(MAG3)

9. Radionuclides for Imaging
Desirable characteristics
Minimum particulate emission
Primary photon energy between 50-500 keV
Physical T1/2 > time reqd to prepare material
Effective T1/2 longer than examination time
Low toxicity
Stability or near stability of the product

10. Technetium99m
Fulfills many criteria of ideal radionuclide
No particulate emission
6 hour half life
Used in most nuclear imaging procedures

11. Tc-99m
Mercaptoacetyltriglycine
Tc-99m MAG3 is commonly used
As it is protein bound hence(97%) not filtered and
Cleared by tubular secretion  shows significant
anatomic details
Alternative path of excretion is via the hepatobiliary
route.
The normal time to peak activity is 3 to 5 minutes, with a
time to half peak (T½) of 6 to 10 minutes.
Clearance is bi-exponential, and in patients with normal
renal function, 90% of the dose is cleared in 3 hours.

12. Tc-99m
Diethylene triamine
pentaacetic Acid
Used to examine flow and renal function
Calculate GFR
 DTPA is a heavy metal chelator used for treatment
of poisoning
Children: 1.9 MBq/kg, minimum dose of 1 mCi (37
MBq)
Adults: 5-10 mCi (185-370 MBq)
5- 10% plasma protein binding, so it tends to
underestimate the GFR

13. DTPA Kinetics
After intravenous injection, normal peak cortical uptake occurs
by 3 to 4 minutes.(90% filtered in 4hrs.)
By 5 minutes, the collecting system is seen
By 10-15 minutes the bladder is typically visualized by
The T½ peak, or the time it takes for half of the maximal
cortical activity to clear, is normally 15 to 20 minutes for Tc-
99m DTPA.
Its completely filtered at the glomerulus with no tubular
secretion or reabsorption.
As only 20% of renal function is the result of glomerular
filtration, the 1st
pass extraction of a glomerular filtration agent
is less than that of agents cleared by tubular secretion

14. Tc-99m Dimercaptosuccinic
Acid
Cortical imaging with DMSA is m/c to detect renal
scarring or acute pyelonephritis & provide accurate
differential renal function.
The rapid transit of others (DTPA, MAG3) does not
allow high resolution imaging of the cortex.
But the stable cortical uptake of DMSA produces high
quality images using pinhole imaging SPECT.
Delayed imaging results in high target-to-background
ratios and good resolution.

15. DMSA Kinetics
Upto 40% to 50% of the injected Tc-99m DMSA
dose localizes in the cortex
Common localisation is in the proximal tubules.
Imaging is done after a 2- to 3-hour delay to allow
time for slow background clearance
DMSA Inhibition in PTs diseases :- RTA, Fanconi`s
 Maximum activity at 3-6 hrs
 Images taken at 2 – 4 hrs
Poor target to background :- Poor renal functions

18. Imaging techniques
Dynamic functional studies are generally performed
Perfusion sequence of renal blood flow
 By 3 sec aorta is fully visualized.
 By 5-6 sec, both kidneys are seen.
Maximal kidney activity is reached in 30-60 sec.
Function seqence Consists of 2 parts.
Renal blood flow is assessed in the first pass of the bolus to
the kidney.
Over the next 25 to 30 minutes, uptake and clearance assess
function.

19. Protocols
PATIENT PREPARATION
RADIOPHARMACEUTICAL
INSTRUMENTATION
POSITIONING
COMPUTER ACQUISITION
PROCESSING
Perfusion Time-Activity Curve
Dynamic Renal Function Time-Activity Curve

20. Image acquisition
Flow (angiogram) : 2-3 sec / fr x 1 min
Dynamic: 15-30 sec / frame x 20-30 min
(display @ 1-3 min/frame)

21. DTPA normal

22. 30-60 seconds
2-3
mins

23. Renogram Curvers
The renogram represents a summation of uptake and
excretion.
Three phases are normally seen:-
Blood flow
Cortical uptake
Clearance phases

24. The functional changes are seen by
Time to peak activity
Uptake slope
Rate of clearance
Percent clearance at 20 minutes

25. Differential Functions
calculation is particularly useful because estimated
GFR and serum creatinine may not identify U/L
lesions
 Normally, the relative contribution for each kidney
lies between 45% to 55%
A calculation of GFR or ERPF can be done as a
separate study to quantify actual function.
GFR ~ 1/3 rd of ERPF

26. Interpretation
Flow Phase :- seen immediately after flow appears
in the adjacent artery
first few 2-sec flow frames.
Asses quality of the injection bolus
If the slope of the arterial TAC is not steep or if
activity visibly persists in the heart and lungs,
the injection may have been given improperly
asymmetry suggests abnormal perfusion to the
particular side

27. Interpretation
Cortical Function Phase
Normally kidneys accumulate agent in the
parenchymal tissues in the first 1 to 3 minutes
Cortex appear homogeneous.
calyces and renal pelvis usually seen in this initial
phase
“flip-flop” pattern  poorly functioning side initially
has lower uptake, but the cortical activity on
later images is higher sue to stasis
delayed cortical washout is a nonspecific finding

28. Interpretation
Clearance Phase
calyces and pelvis usually begin filling by 3 minutes.
next 10 to 15 minutes, activity in the kidney and collecting
system decreases
Drains into bladder
Lack of clearance or overlap of PCS structures on the cortex
suggests HN
indirect determination of reflux can be done when ureteral
activity persists after the kidneys have cleared
Prevoid and postvoid bladder images evaluate emptying
and PVRs

30. Diuretic renography
In a dilated system, prolonged retention of agent is seen
because of a reservoir effect.
Furosemide inj. allows accurate identification of patients
affected by obstruction.
It’s a loop diuretic that inhibits Na+ & Cl- reabsorption,
markedly increases urine flow and washout in normal
patients.
Normally the Radiotracer washout is accelerated & In
Obstruction narrow lumen prevents augmented washout
Lasix is given slowly over 1 to 2 minutes  onset of
action within 30 to 60 seconds, maximal effect is seen at
15 minutes : Protocols :- F+20, F+0, F-15

32. Interpretations
In a very distended systems, delayed washout may be
seen regardless of whether obstruction is present.
An “indeterminate” clearance pattern is seen with
little change on the images or TAC
Diuretic response may also be diminished in patients
with azotemia in such cases an increased furosemide
dose or early diuretic infusion (F-15) may be used.
If the GFR on the affected side is less than 15
mL/min, diuretic renography is unreliable.

33. Normal Dilated Non
Obstructed
Obstructed
Inderminate

34. O Reilly`s Curves
Response curves to Furosemide
Curve Patterns
Type I  Normal Non-obstructed
Type II  Progressive Tracer Accumulation-
Obstruction
Type IIIa Rapid respose to Frusemide after initial
accmulation
Type IIIb Poor response to Frusemide (equivocal)
Type IV delayed compensation(delayed double
peaks) (Homsy`s sign)

36. Diuretic Renal Scan
Washout
(diuretic response)
T1/2
time required for 50% tracer to leave
the dilated unit
i.e. time required for activity to fall
to 50% of peak

37. Clearance half time or washout half time (T½) 
quantifications of the collecting system
Another method for T ½ estimation is to fit a curve
to the steepest portion of the washout TAC.
Normal < 10 min
Obstructed > 20 min
Indeterminate 10 - 20 min

39. ACE inhibition renography
Captopril
Indicated in patients at moderate to high risk for RVH.
severe hypertension/resistant to Rx
abrupt or recent onset
onset under the age of 30 yrs. or over 55 years
Abdominal or flank bruits
Worsening Renal parameters after ACE inhibitor Rx
sensitive, non-invasive functional method or diagnosing
RVH.
It blocks the conversion of AT I to ATII  causing fall in
GFR in Pts of RVH who rely on compensatory
mechanism to maintain.

40. Protocols
Stop all ACE inhibitors  2-3 days for captopril & 5-
7 days for longer acting such as enalapril and lisinopril
Also Stop angiotensin receptor blockers and calcium
channel blockers(cause false +ve )
2-Day/1-day protocol
ACE inhibitors cause a drop in GFR  decreases
urine flow that can be visualized during the functional
portion of the study as a diminished function

41. In DTPA the degree of change from baseline is
significant
Greater the change, the higher the probability that
RAS is causing significant RVH.
A 10% decrease in relative function or a decrease in
absolute function  GFR greater than 10% is
considered “high probability”/positive
A change of 5% to 9% is intermediate/boderline
A delayed MAG3 washout and the primary finding
will be cortical retention (cortical staining)

42. Transplant
Renal allograft evaluation is performed using the dynamic
scintigraphy protocol with Tc-99m MAG3
Camera is placed anterior, centred over the allograft in the
lower pelvis.
Some portion of the bladder is included, the entire bladder is
included on pre-void and post-void images.
If concern for RAS exists  ACE inhibitor protocol is used.
The diuretic renography protocol is employed in
hydronephrosis or obstruction.
Delayed images over the course of 1 to 2 hours used to clarify
the cause of fluid collections and assess possible urine leaks.
Acute Rejection v/s Vasomotor Nephropathy

43. GFR
Accurate quantification of GFR and ERPF with
nonradioactive inulin and PAH is done
continuous infusion required to achieve a steady state
and multiple blood and urine samples.
Agents Like Tc-99m DTPA and I-131 OIH or Tc-
99m MAG3) used for estimation
camera-based techniques are employed

44. GFR Estimation
A small known dose of DTPA is counted at a set distance from
the camera face to determine the count rate before injecting it
into the patient.
The actual administered dose is then corrected for the post
injection residual in the syringe & serves as a standard.
Overestimation of GFR may occur if excess dose is counted.
The images are acquired for 6 minutes.
Counts in background are subtracted and Attenuation of the
photons caused by varying renal depth is corrected using
formula based on patient weight and height.
The fraction of the standard taken up by the kidneys in the 1-
to 2.5-minute or 2- to 3-minute frames can be correlated with
GFR

45. Cortical Imaging
Tc-99m DMSA offers superior cortical resolution due
to its significant cortical binding.
Commonly, DMSA is used to evaluate suspected
pyelonephritis or to possibly detect renal scarring in a
patient with reflux.
Occasionally, cortical scintigraphy is used to
differentiate a prominent column of Bertin seen on
ultrasound from a true mass
For acute pyelonephritis  DMSA is considered the
gold standard.

46. Renal Cortical Scintigraphy
Congenital Anomalies
Agenesis
Ectopy
Fusion (horseshoe, crossed fused ectopia)
Polycystic kidney
Multicystic dysplastic kidney
Pseudotumors (fetal lobulation, hypertrophic column of
Bertin , lobar nephronia)

47. Method
Here dynamic imaging is not performed
Background clearance is slow and the kidney clears
only a small percentage of the radiotracer.
Delayed cortical planar or SPECT imaging is acquired
Planar imaging usually requires at least both posterior
and posterior oblique views.
A pinhole collimator or converging collimator
provides magnification and improved resolution.
SPECT has excellent image detail(better resolution)

48. Imaging
normal DMSA  homogeneous distribution
throughout the renal cortex
Upper poles appear less intense  splenic
impression, fetal lobulation, and attenuation from
liver and spleen.
The central collecting system and medullary regions
are photon deficient because DMSA tubular binding
occurs in the cortex.

49. Interpretations
DMSA scan will show radiotracer uptake in a column of
Bertin but not in a mass caused by tumour
Areas of cortical tubular dysfunction from infection or
scar present as cortical defects(focal, ill defined or
multifocal)
Tumour will present as a defect because cortical scanning
is not specific(correlate with USG)
Diffuse loss of activity seen in diffuse inflammatory
process
Scars have a localized, sharp margins
Acute scars improve in function ( upto44%) over 6
months f/u scans else are termed chronic scars

50. CYSTOGRAPHY
MAG3 or Tc-99m sulphur colloid or DTPA are
employed agents
asked to not void until the bladder is maximally
distended {(age + 2) × 30 = vol. in ml }
First a Pre Voiding image is obtained
Secondly dynamic Voiding images are acquired
Finally a Post void film is obtained


51. Reflux
Reflux grades have been described for radiographic
contrast studies
In this system, criteria include
The level the reflux reaches
The dilation of the renal pelvis
The ureteral dilation and tortuosity.
But the anatomical resolution is much lower with
scintigraphic methods and calyceal morphology is not
well defined.

54. EC :- Ethylene Dicysteine
Metabolite of the L,L-ECD(ethylene cystine dimer)
with cortical uptake
Secretion in proximal convoluted tubules
Plasma protein binding is 50%
Exact excretion mechanism is not known
Clearance is 69-85% of OIH

55. MIBG

56. Refrences
Oxford text book of clinical nephrology-3rd
ed.
Essentials of Nuclear Medicine Imaging – Mettler
Brenner and Rector’s The kidney– 9th
ed.