Determination of differences in dosimetry with and without intravenous contrast media for radiotherapy planning in the anatomical region of the head and neck
In radiotherapy (RT), to determine the tumor volume (TV) and its morphology, computed tomography (CT) is used, acquiring images without and with intravenous iodinated contrast media (CM), where its influence has been poorly studied usually in artificial phantoms. Computerized dosimetries without and with CM from 10 CT of head and neck were analyzed using a before-after design. The same study group served as a control. Point doses and dose-area histogram (DAH) were evaluated, as well as a dose-volume histogram (DVH), using Student’s t-test with 5% significance. Before and after administering CM, the average difference between point doses was –0.09% within the confidence interval (CI) 0.27% and –0.45%, with a standard deviation (SD) 0.52%. The average doses using DAH, resulted in a mean difference of 0.02%, within the 0.2% CI and -0.16%, with 0.27% SD. The standard volume within 100% of the dose utilizing DVH analysis resulted in an average of the differences of 0.1%, with CI 1.34% and –1.14% and SD 1.76%. The t-test of difference of means for paired designs, with α=0.05 found that there are no significant differences between the study and control groups for the different dose reading methods.