William C. Lavely MD, Presenter: Nothing to Disclose

Harvey A. Ziessman MD, Abstract Co-Author: Nothing to Disclose

George Sgouros PhD, Abstract Co-Author: Nothing to Disclose

Intraperitoneal (IP) scintigraphy is done in patients undergoing peritoneal dialysis and in patients with chemotherapy catheters to evaluate for peritoneal/pleural connections. This study evaluated the absorbed dose to 23 tissues and to the whole body for IP administered Tc-99m sulfur colloid (TSC).

Gamma camera scintigraphy demonstrated negligible biological clearance of IP injected TSC. Dosimetry was performed assuming that IP injected TSC is eliminated by physical decay only. The effect of IP fluid leakage to the pleural cavity was estimated by considering scenarios of 1, 5 and 10% IP fluid leakage. The MIRD methodology, with S-values for Tc-99m in the peritoneal cavity volume, was used to estimate absorbed dose; electron contribution was assumed to be negligible. The residence time resulting from different levels of IP leakage into the pleural cavity was assigned to the lungs and MIRDOSE 3.1 was used to estimate the absorbed dose to other organs from activity in the lungs. The MIRDOSE 3.1 derived absorbed doses were added to the doses obtained when the peritoneal cavity is the source to give total absorbed dose to different tissues with 0, 1, 5 and 10% leakage into the pleural cavity.

Absorbed doses ranged from a minimum of 8.7 x 10-6 mGy/MBq (3.2 x 10-5 rad/mCi) to the brain to a maximum of 5.6 x 10-2 mGy/MBq (2.1 x 10-1 rad/mCi) to the uterus; the red marrow absorbed dose was 5.6 x 10-3 mGy/MBq (2.1 x 10-2 rad/mCi). At 1, 5 and 10% IP leakage, corresponding absorbed dose values for brain were 1.1 x 10-5, 2.0 x 10-5 and 3.1 x 10-5 mGy/MBq, respectively. The values for uterus were 5.6 x 10-2, 5.3 x 10-2 and 5.1 x 10-2 mGy/MBq, respectively. These two organs received the min and max absorbed dose, regardless of IP leakage. The greatest increase in absorbed dose as a result of IP leakage occurred for the thyroid. At 10% IP leakage, the thyroid absorbed dose of 3.0 x 10-4 mGy/MBq represents an 11-fold increase over the dose absorbed in the absence of IP leakage.

Tc-99m sulfur colloid peritoneal scintigraphy provides a method for evaluating peritoneal leaks at low radiation doses. Even with a 10% peritoneal/pleural leak, radiation dose to all organs remains low.

Lavely, W, Ziessman, H, Sgouros, G, Internal Dosimetry for Scintigraphy of Intraperitoneally-administered Tc-99m Sulfur Colloid.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4415024.html