1. USE OF NUCLEAR IMAGING
IN KIDNEY DISEASES :
INDICATIONS AND
INTERPRETATIONS
20-5-13
2. Isotopes
Any given element may have many isotopes
All isotopes of a given element have the same no of
protons and differ only in the no of neutrons
Some of these isotopes have unstable nuclear
configuration and seek greater stability by
decay/disintegration to a more stable form
Isotopes attempting to reach stability by emitting
radiation are called radionuclides/radioisotopes
4. 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
5. Technetium
99m
Fulfills many criteria of ideal radionuclide
No particulate emission
6 hour half life
A predominant (98%) 148KeV photon
conversion
Used in > 70% of nuclear imaging procedures in
United States
6.
Nuclear medicine is a branch of medicine
and imaging that uses radionuclides and relies on
the process of radioactive decay in the diagnosis
and treatment of disease.
Used in Nephro-Urology since 1960s
7.
Functional and anatomic information
More organ / tissue specific c/t whole body scans
RADIOPHARMACEUTICALS =
RADIONUCLIDES + PHARMACEUTICAL
8. NUCLEAR SCINTIGRAPHY
TECHNIQUES
2D Scintigraphy - use of internal radionuclides to create twodimensional images.
3D SPECT - tomographic technique using gamma camera
data from many projections and reconstructed in different
planes
HYBRID SCAN - SPECT/CT and PET/CT
11. Radiopharmaceutical Agents
1.
Grouped into three categories:
Those excreted by glomerular filtration,
1.
Those excreted by tubular secretion, and
2.
Those retained in the renal tubules for long
periods
14. Tc 99m DTPA
•
•
•
Inulin clearance remains the gold standard to
measure GFR, but it is expensive, time
consuming, and requires a steady-state plasma
concentration and accurate and timed urine
collection
99m
Tc-DTPA is recommended agent is for GFR
measurement.
5- 10% plasma protein binding, so it tends to
underestimate the GFR(insignificant)
15. •
•
•
•
Peak renal activity after 3 – 4 min.
90 % filtered within 4 hours.
The extraction fraction of 99mTc-DTPA is
approximately 20 per cent; for this reason,
not useful for imaging , in patients with
impaired renal function.
In such cases, agents with higher extraction
efficiencies such as 99mTc-MAG3 more
appropriate.
16. 51Cr-EDTA, which may provide more accurate
values for GFR, but cannot be used for
imaging.
20. I-131 OIH
Secreted by tubules – 80% & glomerular
filtration - 20%
Chemically & pharmacokinetically similar to
PAH
Plasma protein binding – 70%
Cortical peak time = 3-5 min
Radiation absorbed dose to bladder= 0.74
rad/mCi
21.
The main disadvantages of 131I-OIH are the
suboptimal imaging characteristics of 131I.
123
I-OIH has better imaging qualities, but 123I is
more expensive and less available.
23. Tc99m MAG3
70 – 90 % PROTEIN BINDING
89% TUBULAR SECRETION
11% GLOMERULAR FILTRATION
Extraction fraction of 40-50%.
Provides a high target-to-background ratio, good
image quality, and more accurate numerical
values, particularly when the kidney function is
low or immature
5 TO 10 mCi i.v. ( ADULTS)
25. EC:
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
28. Cortical agents
Tc99m DMSAPYELONEPHRITIS, INFARCTS, SCARS, ANOMALIES
75% protien binding in 6 hrs
5- 20 % excretion 2 hrs
37% excretion in 24 hrs
40-50% cortical localisation
Maximum activity at 3-6 hrs
2 TO 5 mCi i.v.
Images at 2 – 4 hrs
29.
Importantly, acute infection can produce
abnormalities in the scan; and if the test is being
performed to evaluate for cortical scarring, it
should be done at least 3 months after an acute
infection ( Rosenberg et al, 1992 ).
31. CONTD..
Tc 99m GH
It is both filtered by the glomerulus and bound by
the tubules.
Glomerular filtration 80-90%
Tubular secretion 10-20%
25-40% in 1 hr & 70% in 24 hrs in urine
15% bound to PCT
EARLY DYNAMIC FUNCTIONAL imaging
DELAYED CORTICAL imaging
10-15 mCi
35. Basic Renal Scintigraphy
Patient Preparation
Patient must be well hydrated
Give 5-10 ml/kg water (2-4 cups)
30-60 min. pre-injection
Can measure U - specific gravity (<1.015)
Void before injection
Void @ end of study
Int’l Consens. Comm.
Semin NM ‘99:146-159
37. Basic Renal Scintigraphy
Acquisition (cont’d)
Obtain a 30-60 sec. image over injection site @
end of study
if infiltration >0.5% dose do not report clearance
Obtain post-void supine image of kidneys
@ end of study
Taylor, SeminNM 4/99:102-127
38. International Consensus Committee
Recommendations for Basic Renogram
Tracer: MAG3, (DTPA)
Dose: 2 - 5 mCi adult, minimum 0.5 mCi peds
Pt. position: supine (motion, depth issues)
Include bladder, heart
Collimator: LEAP
Image over injection site
Int’l Consens. Comm.
Semin NM ‘99:146-159
39. Radionuclide Renal Evaluation
Functional Imaging(visual assessment of
perfusion and function)
Renography (time activity curve representative
of renal function)
Quantification of renal function(GFR &
ERPF)
Anatomic imaging( cortical imaging)
40. Functional Imaging
Perfusion imaging –
Evaluation of renal blood flow and function of
native kidneys – posterior projection ;
transplanted kidneys – anterior projection
10-20mCi of radiopharmaceutical injected iv in
antecubital vein.
Imaging renal perfusion is usually begun as soon
as bolus is seen in abd. Aorta
Subsequent images are taken every 1-5 secs
41.
In normal 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.
43. Renal functional imaging
At the end of perfusion sequence , imaging for
function begins.
Dynamic or sequential static; 3-5 min Tc99m
DTPA or MAG3 are then obtained over 20-30
mins.
Evaluation is similar to an IVP with – anatomy,
position, symmetry and adequacy of function &
collecting system patency.
44.
With Tc99m MAG3 maximal parenchymal activity
is seen at 3-5 min
Activity in collecting system and bladder by 4-8
mins.
46. Renography
A Time Activity Curve
Graphic representation of uptake and excretion
of radiopharmaceutical
Information is displayed from time of injection
to abt 20-30 mins
47. Renogram Phases
FLOW / VASCULAR PHASE
( 30 MIN )
(RADIONUCLETIDE
ANGIOGRAM)
•
•
FUNCTIONAL PHASE
II.
Parenchymal phase(uptake)
Last for 30-60 sec.
•
Max activity 3to 5 min
Max activity 4-6 secs
•
UPTAKE AT 2 TO 3 MIN FOR
after peak aortic activity
SPLIT FUNCTION
III.
Washout (excretory) phase
no activity after 30 min
49. Data obtained from renogram
Time to peak cortical activity- 3-5 min
Half-time excretion- time for half of peak
activity to be cleared from kidney. N – 8-12
mins
Cortical activity at 20 min/ peak activity :
< 0.30 on MAG3 renogram.
50. RELATIVE/SPLIT
FUNCTION
Contribution of each kidney to the total function
% Lt kid =
net cts in Lt ROI
--------------------------------------- x 100%
net cts Lt + net cts Rt ROI
ROI: Region of interest
Normal
Borderline
Abnormal
50/50 - 56/44
57/43 - 59/41
> 60/40
Taylor, SeminNM Apr 99
54. Quantitation of Renal Function
GFR & ERPF measurement
Two methods :
Plasma sample based clearances :
The amt of activity remaining in blood at
prefixed times is a measurement of activity not
yet cleared – indirect measure of activity already
cleared.
More accurate ,but requires determination of
pharmaceuticals levels in plasma and some times
in urine.
55.
Camera based clearances :
Counts are obtained from syringe before inj. &
subsequently over kidneys after injection.
No blood and urine collection.
Sufficiently reliable method.
56. Anatomic(Cortical) Imaging
(Tc99m DMSA or GH )
Images obtained after 2 to 4 hrs of injection
Posterior/ right post. Oblique/ left post. Oblique
NORMAL FINDINGS
Smooth contour with Homogeneous activity
Less uptake in medulla
No activity in PCS
57. Diuretic (Furosemide) Renal Scan
Obstructive uropathy (hydronephrosis, hydroureter)
may lead to obstructive nephropathy (loss of renal
function)
Indications:
Evaluate functional significance of hydronephrosis
Determine need for surgery
obstructive hydronephrosis - surgical Rx
non-obstructive hydronephrosis - medical Rx/ follow up
Monitor effect of therapy
58. PRINCIPLE
Hydronephrosis - tracer pooling in dilated renal
pelvis
Furesemide induces increased urine flow
If obstructed >>> will not wash out
If dilated, non-obstructed >>> will wash out
Can quantitate rate of washout (T1/2)
59. PROTOCOL
Oral hydration prior to study
NS @ 15ml/kg over 30 min 15 min prior to
injection & continued in study @ 200ml/kg/24 hr
Bladder catheterization is required in children
Tc 99m MAG3 – agent of choice in children with
limited function
high target-to-background ratio, good image quality,
and more accurate numerical values
60. PROTOCOL
Pre requisite – residual function to respond
Diuretic given ( infants- 1mg/kg, children 0.5
mg/kg, 40 mg adults ) 20-30 min after
radiotracer injection
Imaging for 20 – 30 minutes, post micturition
image
Functional images, renogram time/activity
curve( before & after ), wash out half time
calculated
symmetric uptake and good washout is by
definition not obstructed
61. 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
65. “F minus 15” Diuretic
Renogram
Furosemide (Lasix) injected 15 min before
radiopharmaceutical
Rationale: kidney in maximal diuresis,
under maximal stress
Some equivocals will become clearly positive, some
clearly negative
English, Br JUrol 1987:10-14
Upsdell, Br JUrol 1992:126-132
70. Renovascular Hypertension
Prevalence
<1% unselected population with HTN
Clinical features
Abrupt onset HTN in child, adult < 30 or > 60y
Severe HTN resistant to medical Rx
Unexplained or post-ACEI impairment in ren fct
HTN + abdominal bruits
If these present - moderate risk of RVH (20-30%)
72. Captopril Renal ScanMAG 3
Tc 99m MAG 3 = gold standard
Stop ACE inhibitors 48 hrs prior and no solid food
before 4 hrs
Before procedure, orally fluid – 10 ml/kg
Hydration continued i.v. 4ml/ min
Baseline BP & PR recorded→ captopril 50 mg
73.
Protocol:
1 day vs. 2 day test
1 day test:
baseline scan (1-2 mCi) followed by
post-Capto scan (8-10 mCi)
2 day test:
post-Capto scan,
only if abnormal >> baseline
74. Abnormal captopril Renography
Delayed time to maximal activity >11
minutes(normal -5min)
Significant asymmetry of peak activity of each
kidney
Marked cortical retention of radionuclide
A marked decrease in the GFR of the ipsilateral
kidney.
20-minute counts /peak counts [N <0.3 ], 0.15
change is considered significant.
78. ACEI Renography
In normal renal function - sens/spec ~ 90%
In poor renal function / ischemic nephropathy,
ACEI renography often indeterminate
>>> do MRA, Duplex US, angiogram
80. CONTD..
gold standard 99mTc DMSA
The radiotracer is taken up only by functioning
PCT mass
Pyelonephritis impairs tubular uptake of
radiotracer, these areas appear as unexposed or
underexposed
Persisting areas on follow up indicates
irreversible renal damage or scarring.
81. Renal Cortical Scintigraphy
Cold Defect
Acute or chronic PN
Cyst
Tumors
Infarct
Trauma (contusion, laceration,hematoma)
Cortical defects are not always d/t infection & all
DMSA defects are not necessarily scars.
89. Patient with Recurrent UTI
Tc99m-DMSA renal SPECT
scintigraphy
Ectopic left kidney with multiple
scars
90. Renal Transplant Evaluation:
Anterior images are obtained.
Normal perfusion study: radioactive bolus
reaches the renal transplant simultaneously with
iliac vessels.
Max parenchymal phase :3-5 min
Bladder activity appears : 4-8 min
Up to 2 weeks after Tx, prominent visualisation
of ureter due to edema at UV anastomotic site.
93.
Acute Tubular Necrosis:
Preserved or mildly reduced renal perfusion but
diminished renal function and progressive
cortical retention of tubular agents.
Acute Rejection :
Poor perfusion than function in early stage
Renogram demonstrates a diminished nephrogram
phase and delayed appearance of bladder activity.
95. Renal Transplant Scintigraphy
Transplant kidney is
showing poor perfusion,
uptake and drainage of
radiotracer- Chronic
Rejection
Tc99m-DTPA renal dynamic scintigraphy
96. Cyclosporin nephrotoxicity :
Scintigraphic appearance similar to ATN, with
relative good transplant perfusion and poor
tubular function.
Compared to ATN ,it occurs several weeks after
transplatation.
97. Renal transplants scintigraphy
Surgical complications
Urinary leak-Initial photopenic defect
accumulation of radiotracer
with progressive
Hematoma/ Abscess- Initial photopenic defect not
changing with time.
Lymphocele- Initial photopenic defect- equal to
background activity in delayed images.
Ureteral obstruction
Arterial stenosis and hypertension
100. Renal Transplant Scintigraphy
7th Post operative day of renal transplant c/o
Increased serum creatinine and pelvic collection
Lymphocele
101. Radionuclide Cystogram
INDICATIONS
Assess effect of
therapy / surgery
Screening of siblings of
reflux pts
Evaluation of children
with recurrent UTI
(30-50% have VUR)
PROs
More sensitive
100 times less radiation
CONs
Inferior anatomic
deleniation
103. Refrences
Oxford text book of clnilcal nephrology-3rd ed.
Essentials of Nuclear Medicine Imaging –
Mettler & Guiberteau
Brenner and Rector’s The kidney– 9th ed.
www.google.com
Notes de l'éditeur
—2-year-old girl with fever. Dimercaptosuccinic acid (DMSA) renal cortical scintigraphy scan obtained same day as ultrasound (C) shows corresponding photopenic defect (arrow). Follow-up DMSA scan obtained 8 months later (D) shows resolution of defect, consistent with recovered pyelonephritis.