Dynamic computed tomography of the lungs with reduced radiation load

Abstract

Aim. To evaluate the possibilities of dynamic lung CT using a low-dose scanning Protocol. Materials and methods. The study is based on the experience of using two protocols of dynamic lung CT in 97 patients with single foci in the lungs. CT study was performed on a multispiral computed tomograph GE Optima CT660 with bolus administration of 100 ml of iodine-containing drug at a rate of 3.5 ml/sec. Native the study was conducted from the level of the jugular notch to the diaphragmatic sinuses. After that, the focus area was scanned for 30 seconds, 1, 2, 4, 6, 15 minutes after administration of contrast agent. Depending on the scanning Protocol used, the patients were divided into 2 groups. The Protocol of the first group of patients (n = 20) included the following parameters: radiation field (Nativ/contrast phase) – 270–340 mm/100-140 mm; voltage – 120 kV; the current 80–400 mA; rotation time of the tube – 0,6 sec; slice thickness 5 mm. the parameters of the scanning Protocol of the second group of patients (n = 50): radiation field (Nativ/contrast phase) – 270–340 mm/30–45 mm; voltage – 100 kV; the current 80–400 mA; rotation time of the tube – 0,6 sec; the slice thickness is 5 mm. Quantitative assessment included measurement of effective dose. Qualitative assessment of each study included the analysis of the CT scans obtained with an assessment of the degree of “noise” of the image and its impact on the interpretation of the obtained CT data. Results. In the first group of patients, the tube voltage was 120 kV, the irradiation field in the native phase was within 270–340 mm, in contrast phases of the study-within 100–140 mm (124.5 ± 12.8 mm), while the effective dose ranged from 13.7 mSv to 21.5 mSv and averaged 18.1 ± 2.4 mSv. In the second group of patients radiation field in the native phase was in the range of 270–340 mm, the contrast phase of the study – in the range of 30–45 mm (36.0 ± 6.1 mm), the effective radiation dose was varied in the range of 5.1 mSv – 10.2 mSv and the average was 7.6 ± 1.7 mSv. Conclusion. The use of the developed Protocol of CT-study in the dynamic CT of the chest provides a reduction in the dose of radiation by an average of 42% while maintaining an adequate assessment of the data on the accumulation and leaching of contrast agent formation.