The application value of low-dose contrast agent combined with bolus tracking technique in radiotherapy localization for nasopharyngeal carcinoma / 中华放射肿瘤学杂志

ABSTRACT

Objective:To assess the application value of low-dose contrast agent combined with bolus tracking technique in radiotherapy localization for nasopharyngeal carcinoma (NPC).Methods:One hundred patients with NPC for radiotherapy localization were enrolled prospectively and randomly divided into observation ( n = 50) and control ( n = 50) group using random number table. All patients in the control group underwent routine computerized tomography (CT) for radiotherapy localization with an intravenous bolus of 80 ml iodinated contrast media. Images were obtained at a fixed delay of 50 s from the beginning of contrast injection. Patients in the observation group underwent CT scan using a bolus tracking technique with an intravenous bolus of 50-60 ml iodinated contrast media. By observing the time-CT value monitoring curve, the scanning was manually triggered when the peak fell. The score of image quality, enhanced CT value, iodine contrast dose, and dose calculation variance of planning target volume were compared between the two different dose groups. The differences of dose were compared using independent sample t-tests and the differences in graph scores were compared using Wilcoxon rank sum tests. Results:The dosage of iodine contrast agent in the observation group was 28.75% less than that in the control group, and the difference achieved statistical significance ( t=-42.11, P<0.001). The enhanced CT value of carotid artery and jugular vein in the control group increased 32.58% and 21.02% compared with patients in the observation group, respectively ( t=-8.11 and -4.82, P<0.001 for both). No statistically significant differences in the enhanced CT value were found for the gross tumor volume (GTV) of nasopharynx or sternocleidomastoid between the two groups ( P>0.05). The images in both groups can met the requirements of target volume delineation, and the difference of subjective score was not statistically significant ( Z=-1.36, P=0.175). There were no significant differences in the signal-to-noise ratio (SNR) or contrast-to-noise ratio (CNR) of nasopharynx between the two groups ( P>0.05). The results of subjective score and GTV target area showed high consistency between the two doctors with a κ value of 0.77. The differences in dose calculation variance of planning target volume between the two different dose groups was also not statistically significant ( P>0.05). Conclusions:In the radiotherapy localization for nasopharyngeal carcinoma, the application of low-dose contrast agent combined with bolus tracking technique could obtain good images for target delineation and effectively reduce the intake of iodine contrast agent and the risk of adverse reactions. Based on these results, low-dose contrast agent combined with bolus tracking technique has wide range of application.