Normal Study

MAG3 Study

General

• Tracer = Tc-99m-MAG3

• Dose = 0.1 mCi/kg

• 1 frame every 15 seconds for 20 minutes

• Furosemide 1.0 mg/kg (max of 40 mg)

• Minimal radiation dose (less than a CT)

• When looking at renal artery stenosis

  • Hold ACEi for 2-5 days prior to exam

  • Give 25 mg captopril (oral 1.0 mg/kg) not to exceed 50 mg

  • Give 300-500 ml of water

Analysis

• 3 Things to look at basically

• Cortical/Parenchymal phase (60-120 seconds)

  • Look at uptake, shape, size, location, total and split function

• Transcortical Transit Time

  • This is the time from tracer injection to the pelvicalyceal system

  • Normal = 2-5 minutes

• Drainage Phase

  • Image and time-activity curve analysis

• When looking at renal artery stenosis, an abnormal study is characterized as

  • Increased split differential uptake

  • Increased cortical transit time

  • Retention of tracer in renal parenchyma

  • When you give captopril to a pt with RAS the MAG3 clearance will decrease (when given to patient with normal renal function MAG3 clearance will increase)

• For our reports at UH it asks to report the T1/2 clearance

  • To get this you need to look at the time at which it is Tmax and look at the counts on the left (Y axis)

  • Go to the time on the X axis where the counts are half of the Tmax

  • Then subtract the time where it is T1/2 from the time at Tmax

  • Normal is < 10 minutes

  • Equivocal is 10-20 min

  • Evidence of obstruction = > 20 min

Normal Study

Delayed clearance

• May be seen with obstruction

Duplicated Collecting System

• Basically half kidney is photopenic

Super-Renal Function

• Basically rapid uptake and excretion

• Nothing worrisome

Renal Scintigraphy

Renal Artery Stenosis

• Right kidney is smaller and shows delayed uptake and retention = RAS

Abnormal Study

Tc-99m DTPA

General

• Used to evaluate renal cortex, such as for:

  • Renal scarring (vs pyelo)

• Pinhole collimator or SPECT used to image