Contrast Saline Mixture DualFlow Injection Protocols for Low-Kilovolt Computed Tomography Angiography: A Systematic Phantom and Animal Study

Improvement in arterial enhancement using diluted injection of contrast medium in CT angiography

BACKGROUND

Arterial enhancement after contrast injection affects the quality of computed tomography angiography (CTA) images.

PURPOSE

To evaluate whether the dilution of contrast medium (CM) for CTA increases arterial enhancement after the adjustment of iodine concentration as per the patient's body weight (BW).

MATERIAL AND METHODS

We retrospectively studied 700 patients who underwent coronary CTA. The first 350 consecutive patients underwent standard CTA with a fixed iodine concentration, whereas the remaining 350 underwent CTA with a diluted CM injection. All patients were classified into three groups according to their BW (<55, 55-65, and 66-73 kg). The mean and proportion of contrast enhancements (CEs) in the ascending aorta of ≥350 Hounsfield units (HUs) (CE₃₅₀) were compared between the standard CTA and diluted CM injection and among the BW groups. The associations between BW and CE were analyzed using linear regression.

RESULTS

Receiving diluted CM increased the mean CE in the <55-kg group (403.4 ± 55.4 HU vs. 382.8 ± 59.3 HU; P < 0.01) but not in the groups with heavier BW. The proportion of patients with CE₃₅₀ increased with BW (<55 kg = 71%, 55-65 kg = 84%, and 66-73 kg = 91%) and increased after dilution (86%, 93%, and 96%, respectively). After CM dilution, the correlation between BW and CE among patients undergoing CTA decreased from 0.37 to 0.22 (P < 0.05).

CONCLUSION

CM dilution for CTA improves arterial enhancement.

Third-Generation Cardiovascular Phantom: The Next Generation of Preclinical Research in Diagnostic Imaging

OBJECTIVE

Different types of preclinical research tools used in the field of diagnostic imaging such as dynamic flow circulation phantoms have built the foundation for optimization and advancement of clinical procedures including new imaging techniques. The objective was to introduce a third-generation phantom, building on the limitations of earlier versions and unlocking new opportunities for preclinical investigation.

MATERIAL AND METHODS

A third-generation phantom was designed and constructed comprising physiological vascular models from head to toe, including a 4-chamber heart with embedded heart valves and a controllable electromechanical pump. The models include modular segments, allowing for interchangeability between healthy and diseased vessels. Clinical sanity checks were performed using the phantom in combination with a dual-head power injector on a third-generation dual-source computed tomography scanner. Contrast media was injected at 1.5 g I/s, and the phantom was configured with a cardiac output of 5.3 L/min. Measurements of mean transit times between key vascular landmarks and peak enhancement values in Hounsfield units (HUs) were measured to compare with expected in vivo results estimated from literature.

RESULTS

Good agreement was obtained between literature reference values from physiology and measured results. Contrast arrival between antecubital vein and right ventricle was measured to be 13.1 ± 0.3 seconds. Transit time from right ventricle to left ventricle was 12.0 ± 0.2 seconds, from left internal carotid artery to left internal jugular vein 7.7 ± 0.4 seconds, and 2.9 ± 0.2 seconds from aortic arch to aortic bifurcation. The peak enhancement measured in the regions of interest was between 336 HU and 557 HU.

CONCLUSIONS

The third-generation phantom demonstrated the capability of simulating physiologic in vivo conditions with accurate contrast media transport timing, good repeatability, and expected enhancement profiles. As a nearly complete cardiovascular system including a functioning 4-chamber heart and interchangeable disease states, the third-generation phantom presents new opportunities for the expansion of preclinical research in diagnostic imaging.

Low kV Computed Tomography of Parenchymal Abdominal Organs-A Systematic Animal Study of Different Contrast Media Injection Protocols

Objectives: To evaluate multiphase low kV computed tomography (CT) imaging of the abdomen with reduced contrast media (CM) dose using different injection protocols. Methods: Two injection protocols were evaluated for use with low kV (80 kV) multiphase abdominal imaging in comparison to the standard procedure acquired at 120 kV (500 mgI/kg; 5 mL/s). This evaluation was conducted in a highly standardized animal study (5 Goettingen minipigs). The low kV protocols consisted of (a) a single-flow (SF) injection with 40% reduced CM dose and injection rate (300 mgI/kg; 3 mL/s) and (b) a DualFlow (DF) injection protocol consisting of 60%/40% contrast to saline ratio administered at 5 mL/s. Dynamic CT was first performed within representative liver regions to determine optimal contrast phases, followed by evaluation of the three protocols in multiphase abdominal CT imaging. The evaluation criteria included contrast enhancement (CE) of abdominal organs and vasculature. Results: The 80 kV DF injection protocol showed similar CE of the abdominal parenchymatous organs and vessels to the 120 kV reference and the 80 kV SF protocol. Hepatic parenchyma showed comparable CT values for all contrast phases. In particular, in the portal venous parenchymal phase, the 80 kV DF protocol demonstrated higher hepatic parenchymal enhancement; however, results were statistically non-significant. Similarly, CE of the kidney, pancreas, and abdominal arterial/venous vessels showed no significant differences between injection protocols. Conclusions: Adapted SF and DF injection protocols with reduced IDR/iodine load offer the potential to calibrate optimal CM doses to the tube voltage in abdominal multiphase low kV CT imaging. The data suggest that the DF approach allows the use of predefined injection protocols and adaption of the contrast to saline ratio to an individualized kV setting and yields the potential for patient-individualized CM adaption.