background-based delineation of internal tumor volumes on static positron emission tomography in a phantom study

objective(s): considering the fact that the standardized uptake value (suv) of a normal lung tissue is expressed as x±sd, x+3×sd could be considered as the threshold value to outline the internal tumor volume (itv) of a lung neoplasm. methods: three hollow models were filled with 55.0 kbq/ml fluorine18- fluorodeoxyglucose (18f-fdg) to represent tumors. the models were fixed to a barrel filled with 5.9 kbq/ml 18f-fdg to characterize normal lung tissues as a phantom. the pet/ct images of the phantom were acquired at rest. then, the barrel was moved periodically to simulate breathing while acquiring pet/ct data. volume recovery coefficient (vrc) was applied to evaluate the accuracy of itvs. for statistical analysis, paired t-test and analysis of variance were applied. results: the vrcs ranged from 0.74 to 0.98 and significantly varied among gross tumor volumes for delineating itv (p<0.01). in two-dimensional pet scans, the motion distance did not affect vrc (p>0.05), whereas vrc decreased with increasing distance in three-dimensional pet scans (p<0.05). conclusion: the threshold value (x+3×sd) had the potential to delineate the itv of cancerous tissues, surrounded by lung tissues, particularly in two-dimensional pet images.