Congress:
EuroSafe Imaging 2020
Keywords:
Action 7 - Radiation protection of children, Cardiac, Paediatric, CT, Contrast agent-intravenous, Diagnostic procedure, Physics, Quality assurance, Prospective, Experimental, Performed at one institution
Authors:
D. Kostova-Lefterova, P. Ilieva, A. Partenova, V. Stoyanova, P. Popeski, B. Bogdanova , K. Genova
DOI:
10.26044/esi2020/ESI-12123
Description of activity and work performed
Purpose: The purpose of the study was to develop low dose cardiac CTA (CCTA) protocols for paediatric examinations and achieve acceptable image quality for every single patient.
Materials and Methods: Optimized CCTA protocol was continuously developed in the period 2015-2019 on a 64-slice CT scanner, Canon Aqulion, installed in 2008. The CT unit is used for both paediatric and adult examinations. Data for 86 paediatric patients was collected. For each patient the following information was collected: patient age, height and weight; protocol used; quantity and speed of intravenous contrast media; dose data and other data including information about the use of sedation, immobilization device and patient support in the CT room. Image quality was scored by experienced radiologists applying 4-grade scale and image quality criteria, based on relative visual grading analysis (VGA) (see Table 1). Patent dose was defined in terms of maximal CTDIvol and DLP.
Results: The age distribution of all paediatric patients was the following: (0-1 m) - 3, (1-12 m) – 42, (1-4 y) – 18, (5-9 y) – 11 and (10-15 y) – 12.
The software version of our CT scanner is earlier than 4.51 and when SURE Exposure tube current modulation is used, the CTDIvol is reported based on the maximum tube current used in the exam, but the DLP is reported based on the average tube current. This is the reason why the reported CTDIvol values are in terms of maximal for the whole CT examination values (for the slice acquired with the maximal tube current value) and they appear to be higher than those reported for other CT units. The used exposure parameters for most of the patients were 80 kV, TCM, 42 effective mAs, 0.828 pitch, 8-12.5 SD, 0.35 s and 16 mm beam width. A new effective immobilisation device was introduced since October 2018 which reduced the number of sedated patients under 5 years by 50 % (Fig. 6). For the rest of the patients, lower quantity of medications was used.
The median values for the CT dose indexes was reduced by a factor of 6 from 18.4 mGy to 3.3 mGy for max CTDIvol and a factor of 11 from 607.8 mGy.cm to 54.2 mGy.cm for DLP. Automatic MDCT injector was used for all patients with optimized quantity of intravenous injection of contrast medium – 1.9 ml/kg; 2 ml/sec.
For all patients, a good contrast enhancement of the cardiac chambers and thoracic vessels was achieved (Fig. 1-5). In two cases-suboptimal enhancement of the right chambers but it was with no diagnostic importance for the clinical cases. For one of the cases the patient’s heart rate was over 140 and the used CT unit do not have any modern technology approach for rotation time faster than 0.35 s. for the second case the sedation was improper and there was movement by the patient during the CT examination (Fig. 1).