Purpose
To instill radiotracer into full bladder and look for vesico-ureteric reflux.

Indirect Method
This is done following dynamic renogram with Tc99m DTPA or Tc99m EC.
If the clearance of tracer from background soft tissue is good and if there is no residual activity in the region of ureters and kidneys, study can be performed immediately. Or else patient can be advised to go to the toilet for the first void and wait for the bladder to fill up to perform the voiding scan.

Direct Methods
Tracer used
Tc99m DTPA or Tc99m Sulphur Colloid; Dose 18.5 – 37 MBq (0.5 – 1.0 mCi)

Techniques of tracer instillation
There are two techniques which are to be performed by the physician or by a technician trained for this under the supervision of the physician:
(i) Supra-pubic puncture technique:
Adequate distension of the bladder is verified by percussion or ultrasound scan. Sterile needle is inserted into bladder under aseptic conditions, urine is aspirated for verification and tracer is injected.
(ii) Catheterization technique:
Bladder is catheterized using Foley’s balloon catheter in older children and feeding tube in infants with sterile precautions. Normal saline is allowed to flow into the bladder from a height of about one meter above the level of the table. Radiotracer is injected thro the tubing with an insulin needle as the saline starts flowing. Here filling of tracer into the bladder can be monitored on the PScope and the filling phase can be dynamically acquired into the computer at 5 sec / frame. Filling is stopped at maximal estimated bladder volume:
i.e. (age in yrs +2) X 30 ml.

Imaging of Voiding Phase
In the non-catheter techniques, patient can be positioned erect with the camera vertically behind; male patients are to stand and the females are seated on a urine pan. Privacy is provided by using screen stands, locking the camera room door and dimming the lights. Voided volume should be measured and entered in the case record.

Static pre-void image is acquired for 15 sec in 256 X 256 matrix.
Dynamic imaging is performed during voiding at 2 sec / Fr in 64 X 64 matrix.
Static post-void image is acquired again for 15 sec in 256 X 256 matrix.

In the catheter method, clamp of the catheter is released and the urine is allowed to drain into a tray while dynamic imaging is performed. In infants and in irritable or spastic bladders one may not have control on the peri-catheter voiding and disposable paper towels should be used to contain the radioactive urine.

Image Processing
ROI analysis can be used to estimate bladder residue & refluxed volume and TAC’s can be used to calculate the voiding rates.