A one-month prospective study, conducted at a hospital in the centre region of Portugal, collected information on bolus tracking supported multiphase hepatic CT studies of adult patients. The work, performed after appropriate authorization, ensured patients and health professional’s data confidentiality. This study collected data on patients’ anthropometric measurements, ICM injection protocol information and also, on relevant DICOM metadata and dose report.
1. Patient population
This study enrolled 38 patients, 84 % males and 16% females, aged between 33 and 84 years old (63.8±12.6 years-old). Fig. 1 resumed patient age distribution.
Fig. 1: Bar Chart of Patient age distribution
References: School of Health Sciences, University of Aveiro (ESSUA) - Aveiro/PT
Patients' anthropometric measurements showed mean values of 73.6 ± 13.7 kg to body weight (BW) and 1.67 ± 0.09 m to body height. Calculated body mass index (BMI) was 26.0 ± 4.4.
2. ICM injection protocol
A non-ionic ICM was administered according to habitual practices used in the institution.
The venous puncture was mostly performed (71%) on the patient's left side, with no statistically significant differences between the venous puncture side.
Contrast injected flow ranged between 3.0 and 4.0 mL/s (Fig. 2).
Fig. 2: Bar Chart of CT studies distribution according to used injection flow rate.
References: School of Health Sciences, University of Aveiro (ESSUA) - Aveiro/PT
Arterial scan phase was started with bolus tracking. Two methods were used – automatic trigger and manual trigger, and the arterial delay was calculated with the following expression:
Arterial Scan Delay = MD + (NMI x (ISD + ROT)) + DD
MD – Monitoring Delay (time between injection start and the first monitoring image)
NMI - Number of Monitoring phase Images
ISD - Interscan Delay
ROT – Rotation Time
DD – Diagnostic Delay (time between trigger and the start of arterial acquisition)
Portal venous phase delay was always performed 40 seconds after the arterial phase acquisition.
3. Structures Enhancement quantitative Analysis
Contrast enhancement was evaluated in CT images for three structures – Aorta artery, portal vein and liver parenchyma. The Hounsfield Units (HU) evaluation was performed in axial images at the level of the celiac trunk artery, using circular ROI’s of 100 mm2 as presented in Fig. 3. Aorta artery ROI was placed in the centre of the aorta, portal vein ROI was placed in hilar zone of the main portal vein and liver parenchyma ROI was placed preferably in segment III and with no vascular or biliary structures contribution. Measurements were performed to non-enhanced and contrast-enhanced phases (arterial and portal venous acquisitions) using institution PACS viewer.
HU average of each measurement was collected, and structures enhancement calculated to each contrast-enhanced phase by the difference between enhanced and non-enhanced structures HU average values.
Fig. 3: Example of the ROI's arrangement to perform structures HU measurement.
References: Serviço de Imagiologia, Centro Hospitalar e Universitário de Coimbra (CHUC) - Coimbra/PT
4. Statistical Analysis
Data were evaluated using IBM© SPSS© Statistics 25. Scale variables summarized as the mean value ± standard deviation (SD), and categorical variables calculated as the count (percentage).
Normal distribution was evaluated using the t-student test, and when observed parametric tests were used. Pearson correlation tests were used to bivariate correlations analysis. Also was performed the analysis of variances.
Statistical significance was considered when p <.05.