Changes in thymus size observed radiographically during the course of spontaneous lymphoma in the AKR/J mouse.

Previous means of diagnosing AKR lymphoma only detected mice in fairly advanced stages of the disease. Since the first organ to be affected is usually the thymus, a study was made of the feasibility of diagnosing the disease and following its course by observing changes in thymus size radiographically. Rapid exposure of unanesthetized AKR/J mice to relatively soft X rays provided adequate radiographs with negligible doses to the mice (3-4 mrad). Planimeter measurements made of the cross-sectional area around the heart and thymus in side view radiographs of the individually housed mice provided a quantitative and reproducible measure of the thymus size for thymuses greater than 100 mg. When these measurements were added to the palpation scores of spleen and lymph nodes, all leukemic mice were detected. Thymus size increases were not detected until late in the disease, and decrease in thymus size was seen in approximately half of the mice prior to death. This precluded direct correlation of size to time of death. There was no relationship between the preterminal decrease in thymus size and increasing or decreasing blood leukocyte counts or leukocyte size.