European Nuclear Medicine Guide
This molecule was initially proposed as the L,L-EC isomer, but the radiopharmaceutical is a racemic mixture (N,N-EC) of the two enantiomers. It is a metabolite of the brain radiopharmaceutical [99mTc]Tc-ECD (ethylenedicysteine diester).
Ethylene dicysteine is a small molecule (369 g.mol-1) and binds to plasma proteins (20-45%). It is partly (17%) filtered in the glomeruli, but the major portion (50%) is secreted in the proximal part of tubules by organic anion transporters. This leads to a first-pass extraction rate of circa 65%, which is much higher than that of [99mTc]Tc-DTPA and slightly higher than that of [99mTc]Tc-MAG3.
It has no hepatobiliary metabolism.
[99mTc]Tc-bisicate, like other tubular agents (([123I]OIH and [99mTc]Tc-MAG3), has a high extraction rate thereby leading to high image quality. In most cases, the tubular and glomerular functions are parallel, so split renal function can be assessed with [99mTc]Tc-bisicate as well as with [99mTc]Tc-DTPA. Exceptions are:
In either case, [99mTc]Tc-bisicate secretion can be preserved, even when glomerular filtration is severely decreased.
When renal function is low, the high extraction makes [99mTc]Tc-bisicate even more efficient than [99mTc]Tc-DTPA to assess split function.
The suggested activitie to administer is
[99mTc]Tc-bisicate: No recommendations are given for paediatric nuclear medicine.
The effective dose for [99mTc]Tc-bisicate is 6.3 µSv/MBq in patients with normal renal function and 4.6 µSv/MBq with abnormal kidney function, the organ with the highest absorbed dose is the urinary bladder: 95 µGy/MBq [3].
The effective dose for [99mTc]Tc-DTPA is approximately: 0.47 mSv per procedure.
Caveat:
“Effective Dose” is a protection quantity that provides a dose value related to the probability of health detriment to an adult reference person due to stochastic effects from exposure to low doses of ionizing radiation. It should not be used to quantify the radiation risk for a single individual associated with a particular nuclear medicine examination. It is used to characterize a certain examination in comparison to alternatives, but it should be emphasized that if the actual risk to a certain patient population is to be assessed, it is mandatory to apply risk factors (per mSv) that are appropriate for the gender, the age distribution and the disease state of that population."
After basic, visual assessment, the relative renal function should be measured by tracing renal ROIs and background ROIs (ideally perirenal rings) to get a corrected renogram. The best quantifying method is the Rutland-Patlak graph, which requires placing the heart into the field of view. Alternatively, the area method (taken between 1- and 2-min post-injection, and in any case well before the peak activity has been reached) can be used.
In patients with low renal function, the liver activity must be considered when assessing the right kidney function.
Care should be taken to ensure the patient is adequately hydrated before scanning
If a diuresis renography is considered, prior hydration should be ensured, per os if possible, with circa 7 mL/kg body weight. When i.v. infusion must be used, a sodium-low solute must be used to ensure a rapid diuresis, such as 5% glucose solution. In infants, however, pure glucose solution is dangerous, and a mixed saline-glucose solution is recommended.
Probenecid is taken by the same organic ion transporters with possible competition. Discontinuation should be considered.
There are no EANM procedure guidelines, but information regarding the methodology can be found in in the published literature [114,115].