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75 Cards in this Set
- Front
- Back
What are 3 techniques of looking at the kidney in nuclear medicine
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tracer clearance
physiologic structure radionuclide cystography |
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What is tracer is used in tracer clearance
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MAG3
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What tracer is used to evaluate the physiologic structure of the kindney in nuclear medicine
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DMSA
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What are the 2 types of renal imaging studies in nuc medicine
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renogram (standard)
cortical imaging |
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What tracer is used for cortical imaging
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DMSA
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What tracers are used for a renogram
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MAG3 or DTPA
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What to important physiologic quantitative measures that are gained from doing a renogram
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the GFR and ERPF (effective renal plasma flow)
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What is the ERPF
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this is the total perfusion of the kidney that is available for clearance. (80% tubular secreation and 20% GFR)
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What is excluded in the ERPF
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capsular secretion (this is not available for clearacn)
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What is the main reason to to a renal scan
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for the quantitave measurements (GFR and ERPF)
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What are 4 common reasons to do a renal scan
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evaluate:
degree of obstruction transplant evaluation suspected ATN renovascular hypertension |
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How is a renal scan done
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bolus injection of 10mCi of MAG3
image posteriorly immediate dynamic phase 2-5 sec per frame for a total of 1 minute then continous 30-60 per frame second images for about 30 minutes |
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What does it mean if the persfusion of the kidney is good
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the kidney is usually good bc perfusion mirrors function the one exception is ATN
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Is renal perfusion relatively perserved in ATN
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often it is
blood flow is better than might be expected for the degree of renal insufficiency |
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What is split function
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quantification using ROI
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How is quantification of the kidneys done on a renal scan
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ROI drawn of the entire kidney on immediate images.
The relative uptake at about 2-3 minutes post injection is then calculated after background substraction |
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When should the relative uptake be measured
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at 2-3 minutes before the tracer appears in collecting system
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How is the ROI drawn when trying to measure clearance
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the roi is drawn around the periphery of the kidney to avoid counting activity in the collecting system
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What is a time activity curve
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this is a curve of clearance and is
renal tracer Vs time |
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Why is the quantative time activity curve of clearance an imperfect science
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because its difficult not to include the collecting system in the ROI and this causes error.
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In a standard renogram what tracers are used
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both MAG 3 and DTAP
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What is MAG3 used to look at
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renal perfusion and excretion
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What is DTAP used for
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look at GFR
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What are the two parts to MAG3 portion of the study
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immediate phase which looks at perfusion for 1 minute (flow or perfusion phase)
then second images for function that last for 30 minutes |
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What is the 1st phase of a renal scan
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blood flow sequence
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Can DTAP be used in the renogram flow and function portion
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yes, but the uptake is not as brisk and excretion is not as quick in the 2nd phase
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What is being analyzed in the second phase of a renogram
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the uptake and clearance of tracer from the kidneys.
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What phase of a renogram is split function quantification done
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the second phase (function phase or 30 minute phase)
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How is split function quantification done
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by making an ROI of kidney, background (subtract out) and bladder (account for lost tracer)
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When is split function quantificaction done
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after 2-3 minues (before the tracer gets in collecting system)
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What tracers can split function be done with
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MAG3, DTPA or DMSA
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What is quantified with quantificaiton split function
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uptake by kidneys (will be different for each)
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What else is quantified in the 2nd phase of the renogram
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clearance (draw ROI around periphery of the kidney to avoid the collecting system)
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What is the name of the curve made from clearance
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time activity curve of clearance
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What information is derived from the time activity curve of clearance
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time to peak uptake
T1/2 of clearance from time of peak uptake fraction of tracer remaining at 20 minutes |
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What is a study that is different from clearance that is used to evaluate the rate of emptying of the collecting system
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diuretic study
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What is the difference of a rate of emptying study and clearance
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rate of emptying demonstrates drainage of the pelvis and calcyes and not renal function
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How are the ROI different for clearance and emptying studies
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clearances (ROI around the cortex)
emptying (ROI around the entire kidney) |
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What is an emptying study useful to evaluate
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hydronephrosis (differentiate obstructed from non-obstructed or how badly obstructed)
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What is the idea behind using an emptying study to determine if there is obstructed hydronephrosis
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if the pelvis can be flushed.
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What preparation is important before a bladder emptying study
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have the patient void so they have an emptying bladder (will interfere with hydrodyanamics if not)
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If the T1/2 if less than ten minutes in an emptying study what can be said
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It is normal
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If the T1/2 if greater than 20 minutes in an emptying study what can be said
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it is obstructed (not reliable 30 minutes at cedars)
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When is lasix given
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20 minutes after tracer evaluation
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What is suggested if the kidney is well perfused despite oliguria in a transplant patient
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ATN
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What is a suggestion of transplant rejection in a renal scan
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decreased perfusion but not always
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In the first phase of a renal scan what are you looking besides flow
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tortuosity of the aorta and filling time of the aorta, if beyond 5 frames it indicates poor cardiac function.
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What is seen in transplant ATN with MAG3
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MAG3- relatively good immediate blood uptake with persiting nephrogam (little washout)
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What is seen in transplant ATN with DTAP
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realatively good immediate uptake, kidney fades away without excretion into collecting system.
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Is RAS easily detected by renal scans
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no, blood flow is preserved until extremely severe
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How does an ACE inhibitor work in a captopril scan
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ACE inhibitors blocks vasoconstriction of the efferent arterioroles and as a result more blood flows out the efferent arterioles and GFR falls.
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If a person has renal artery stenosis how is blood flow perserved to the glomeruli
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by angiotensin causing constiction of the efferent arterioles. This causes increased hydrostatic pressure in the glomerulus and maintains renal function.
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What is the goal of a captopril scan
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to induce renal dysfunction transiently by using an ACEI
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What tracer is used for captopril scans
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MAG3 or DTAP
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If baseline renal function is compromised is a captopril scan useful
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no
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What is a problem with captopril studys of RAS
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if there is bilateral disease it is difficult to diagnose and a baseline scan may be needed for comparison.
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What is the appearance of MAG3 in an abnormal captopril scan
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prolonged nephrogram (uptake is normal but clearance is delayed)
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What is the appaearnce of DTPA in a captopril study
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decreased intial uptake and clearance also split function of affected kidny falls)
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If a pt has RAS what happens to the size of the kidney
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decreases
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When doing a captopril study do you have to do a base line study
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yes, on a different day for a comparison (especially with DTPA)
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What quantitative test will change when doing comparing baseline to captopril study in a pt with RAS when using DTAP
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the split function
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What is DMSA used for?
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this is for cortical scans
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How does DMSA work
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binds to the renal tubules and there is little filtration.
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When is a cortical scan done
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in children with pyelonephritis or evaluation of scarring
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Is cortical scans more sensitive than pyelonephritis
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yes
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What is used when doing DMSA scanning
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spect or pinhole images
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What are you looking for in a cortical scan
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areas of the kidney with decreased uptake.
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What will you see a on a cortical scan of a duplex renal system
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upper 1/3 with uptake and the lower 1/3 is without uptake.
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Can you differentiate pyelo from scarring
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no, both will have decreased uptake.
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What is another name for a radionuclide cystography
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RNC
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What tracer is used in RNC
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tc-sulfur colloid
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How is an RNC done
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pt fills the bladdr to initiate voiding and image continously during filling and voiding of the bladder
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What is an RNC used to diagnose
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reflux
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What is a disadvantage of an RNC to VCUG
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you cant see the anatomy, or evaluate the urethra
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When is an RNC done
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as a follow up to a VCUG
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