Phosphocol P-32

Name: Phosphocol P-32

Radiation dosimetry

The effective half-life of phosphorus P 32 is considered to be equal to its physical half-life, with a residence time of 495 hours.

The radiation dose from a uniformly distributed concentration of 37 kilobecquerels (1 microcurie) per gram within a 16-gram prostate is estimated to be equivalent to about 7.3 grays (730 rads)2. Table 3 shows the estimated radiation doses to the prostate and the pleural or peritoneal surfaces3 of an average patient (70 kg) from a dose of 740 megabecquerels (20 millicuries) of phosphorus P 32.

In comparison to the distribution in the prostate, the distribution of phosphorus P 32 on the pleural and peritoneal surfaces is non-uniform, with great extremes in local doses. To obtain an estimate of the average dose, the surface area of the pleural and peritoneal cavities can be assumed to amount to 4,000 and 5,000 cm2, respectively. The estimated radiation doses to an average patient (70 kg) with 90% retention of a dose of 740 megabecquerels (20 millicuries) of phosphorus P 32 distributed uniformly over these areas are shown in Table 3. The decreases of the averaged radiation doses at various tissue depths away from the surfaces of the pleural and peritoneal cavities are also tabulated.

Table 3. Estimated Radiation Doses
Surface/Organ Pleural Peritoneal Prostate
% Retention
Area/wt		 90
4000 cm2		 90
5000 cm2		 100
16 gm
Depth in
tissue
(cm)		 Dose Rate Tissue Dose / 740 MBq (20 mCi)
mGy-cm2
MBq-s		 rad-cm2
μCi-h
grays
rads
grays
rads
grays
rads
0.006 0.75 10 178 17800 134 13400 9180 918000
0.018 0.53 7 125 12500 94 9360
0.03 0.42 5.6 100 10000 74.9 7490
0.12 0.15 2 36 3570 26.7 2670
0.21 0.064 0.85 15 1520 11.4 1140
0.3 0.023 0.31 5.5 550 4.1 410
0.4 0.0047 0.062 1 110 0.83 83
2 Stabin MG. A Model of the Prostate Gland for Use in Internal Dosimetry. J Nucl Med 35(3):516-520, 1994. 3 Watson EE, Stabin MG, Davis JL and Eckerman KF. A Model of the Peritoneal Cavity for Use in Internal Dosimetry. J Nucl Med 30:2002 2011, 1989.

Proper Use of Phosphocol P-32

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

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