On the first imaging timepoint: If the blood pool is not visualized or if there is diffuse, intense tracer uptake in the liver and/or spleen or uptake suggestive of urinary obstruction the biodistribution is altered. Diffuse lung uptake greater than that of blood pool on the first day represents altered biodistribution.
On the second and third imaging timepoints: Uptake suggestive of urinary obstruction and diffuse lung uptake greater than that of the blood pool represent altered biodistribution.
Total body residence times of less than 50 hours and more than 150 hours.
CALCULATION OF IODINE-131 ACTIVITY FOR THE THERAPEUTIC DOSE

There are two options for calculation of the Iodine-131 activity for the therapeutic dose. The derived values and calculation of the therapeutic dose may be determined manually [see “Workbook for Dosimetry Methodology and Administration Set-Up”] or calculated automatically using the GlaxoSmithKline proprietary software program [BEXXAR Patient Management Templates]. The following describes in greater detail the stepwise method for manual determination of the Iodine-131 activity for the therapeutic dose.

Residence Time (hr)

For each timepoint, calculate the background corrected total body count at each timepoint (defined as the geometric mean). The following equation is used:

In this equation, CA = the anterior counts, CBA = the anterior background counts, CP = the posterior counts, and CBP = the posterior background counts.

Once the geometric mean of the counts has been calculated for each of the 3 timepoints, the % injected activity remaining for each timepoint is calculated by dividing the geometric mean of the counts from that timepoint by the geometric mean of the counts from Day 0 and multiplying by 100.

The residence time (h) is then determined by plotting the time from the start of infusion and the % injected activity values for the 3 imaging timepoints on Graph 1 (see Worksheet “Determination of Residence Time” in the “Workbook for Dosimetry Methodology and Administration Set-Up” supplied with Dosimetric Dose Packaging). A best-fit line is then drawn from 100% (the pre-plotted Day 0 value) through the other 2 plotted points (if the line does not intersect the two points, one point must lie above the best-fit line and one point must lie below the best-fit line). The residence time (h) is read from the x-axis of the graph at the point where the fitted line intersects with the horizontal 37% injected activity line.

Activity Hours (mCi hr)

In order to determine the activity hours (mCi hr), look up the patient’s maximum effective mass derived from the patient’s sex and height (see Worksheet “Determination of Maximum Effective Mass” in the “Workbook for Dosimetry Methodology and Administration Set-Up” supplied with Dosimetric Dose Packaging). If the patient’s actual weight is less than the maximum effective mass, the actual weight should be used in the activity hours table (see Worksheet “Determination of Activity Hours” in the “Workbook for Dosimetry Methodology and Administration Set-Up” supplied with Dosimetric Dose Packaging). If the patient’s actual weight is greater than the maximum effective mass, the mass from the worksheet for “Determination