Relative tumor initiating activity of benzo[a]fluoranthene, benzo[b]fluoranthene, naphtho[1,2-b]fluoranthene and naphtho[2,1-a]fluoranthene on mouse skin

The tumor-initiating activities of benzo[a]fluoranthene (BaF), benzo[b]fluoranthene (BbF), naphtho[1,2-b]fluoranthene (NbF) and naphtho[2,1-a]fluoranthene (NaF) were evaluated on the skin of female CD-1 mice. Each of these polycyclic aromatic hydrocarbons was assayed at total initiation doses of 1.0 and 4.0 mumol/mouse. These hydrocarbons were applied in 10 subdoses administered every other day. Promotion commenced 10 days after the last initiator dose and consisted of thrice weekly application of 2.5 micrograms of tetradecanoylphorbol acetate for 20 weeks. BbF was the most potent tumor initiator inducing a 100% incidence of tumor-bearing mice with an average of 8.5 tumors per mouse at a total initiator dose of 1.0 mumol. NaF was slightly more active as a tumor initiator than either NbF or BaF. NaF induced a 90% incidence of tumor-bearing mice with an average of 5.9 tumors per mouse at a total initiator dose of 1.0 mumol. BaF and NbF at a total initiator dose of 4.0 mumol exhibited similar tumor-initiating activity with both inducing a 90% incidence of tumor-bearing mice with an average of 4.3 and 6.6 tumors per mouse, respectively. However, at a total initiator dose of 1.0 mumol, BaF and NbF induced a 95% and 65% incidence of tumor-bearing mice with an average of 3.3 and 2.5 tumors per mouse, respectively.

Detection of intracavitary masses on gated scans: a phantom study

A series of 1.5, 2.0 and 3.0 cm diameter paraffin balls were placed on a 3 cm tether within a simulated left ventricular balloon phantom to determine the maximal balloon volume that permitted identification of the lesion. When images were recorded with the phantom stationary, the lesions could be detected at 100, 280 and 360 ml volumes, respectively. When the phantom was set in motion with a fixed 80 ml stroke volume, the lesions were detected at 120, 320 and 360 ml, respectively. These findings suggest that gating does not decrease lesion detection even when the lesion is freely mobile, and a 1.5 cm lesion would be difficult to detect in an enlarged ventricle, but 2 and 3 cm lesions could be detected even in the presence of moderate ventricular enlargement.