Effect of a saline chaser for contrast enhancement of computed tomographic angiography in cattle

Usefulness of a saline chaser to reduce contrast material dose in abdominal CT of normal dogs

Use of a saline chaser has been reported to allow reduction of contrast dose and artifacts during computed tomography (CT) examination in humans. This study assesses the extent of contrast dose by using a saline chaser in abdominal CT scans of normal dogs. Five beagles underwent abdominal CT scans. Three protocols were applied: 600 mg I/kg iohexol without saline chaser (protocol 1), 30% lower dose of iohexol (420 mg I/kg) followed by a 10 mL saline chaser (protocol 2), and 40% lower dose of iohexol (360 mg I/kg) followed by a 10 mL saline chaser (protocol 3). Attenuation values were obtained from aorta, portal vein, and liver parenchyma. The maximum enhancement values (MEVs) in protocol 2 were significantly higher than those in protocols 1 and 3 in the aorta; no difference was seen in the portal vein in all protocols. The liver parenchymal MEVs in protocols 1 and 2 were significantly higher than those obtained in protocol 3. In this study, the use of a saline chaser and a reduced dose of contrast material did not affect vessel enhancement. In conclusion, use of a saline chaser for abdominal CT of dogs is recommended because it allows a 30% reduction of contrast dose without decreasing vascular and hepatic parenchymal enhancement.

Spiral flow-generating tube for saline chaser improves aortic enhancement in Gd-EOB-DTPA-enhanced hepatic MRI

OBJECTIVES

To evaluate the effect of a spiral tube on contrast enhancement in the hepatic arterial phase (HAP) of gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI).

METHODS

In this retrospective study, we observed 104 patients who underwent dynamic MRI of the liver between October 2017 and December 2017. Three Gd-EOB-DTPA injection protocols were compared: (A) conventional method (undiluted Gd-EOB-DTPA, injection rate 1 ml/s, n = 36); (B) spiral dilution method (1:1 diluted Gd-EOB-DTPA with saline [off-label], injection rate 2 ml/s via spiral tube, n = 38); (C) spiral-flushed method (undiluted Gd-EOB-DTPA, injection rate 1 ml/s via spiral tube, n = 30). We regarded protocol-A as a control. The signal-to-noise ratio (SNR) of the abdominal aorta was calculated using arterial phase images. Image contrast and artefacts were evaluated by two board-certified radiologists, using a four-point scale. Statistical analyses included Dunnett's test, the Kruskal-Wallis test and the Steel test.

RESULTS

The SNR of the aorta was significantly higher with protocol-C (25.4 ± 8.8) than protocol-A (20.8 ± 5.4, p = 0.01). There was no significant difference in SNR between protocols A and B (p = 0.47). The contrast score of protocol-C was significantly higher than that of protocol-A (p = 0.0019). There was no significant difference in contrast score between protocols A and B (p = 0.50). There was no significant difference in artefacts among the three protocols (p = 0.96).

CONCLUSIONS

Use of a spiral tube with a slow injection protocol contributed to improved aortic contrast enhancement in the HAP of GD-EOB-DTPA-enhanced hepatic MRI.

KEY POINTS

• Gadoxetic acid shows weaker arterial enhancement at recommended doses, compared with nonspecific gadolinium agents; selection of an appropriate injection protocol is important. • A spiral flow-generating tube improves the transport efficiency of the contrast media, and increases the signal-to-noise ratio of the aorta in hepatic arterial phase. • A spiral flow-generating tube does not contribute to artefact reduction in hepatic arterial phase.

Comparison of varying injection rates of saline chasers on intravascular contrast enhancement for dynamic CT in cattle

Dynamic CT was performed in five normal Holstein calves to investigate the effect of saline chasers on intravascular contrast enhancement when administered at three different rates. The five calves were imaged using dynamic CT in a crossover study design. Group A was administered only contrast medium (600 mg iodine/kg, 4 ml/s), while groups B, C and D were administered contrast medium at 30 per cent reduction followed by saline chasers injected at 2, 4 and 8 ml/s, respectively. Attenuation values were obtained from the right and left maxillary arteries and dorsal sagittal sinus. Maximum enhancement value and mean value of the enhancement plateau obtained from the maxillary arteries were significantly lower in group B than in the other groups. The duration of the enhancement plateau was longer in group C than in groups B and D (P<0.05).

Use of a saline chaser to reduce the dose of contrast material for dynamic CT in cattle

To investigate the effectiveness of a saline chaser in reducing the required dose of contrast material while carrying out dynamic CT scans in cattle, six clinically normal Holstein calves were subjected to CT scans of the head in a study using a crossover design. The calves were studied as three groups: group A received only contrast material (600 mgI/kg); group B received a 30 per cent lower dose of the same contrast material followed by 50 ml of saline solution; and group C received a 40 per cent lower dose of the same contrast material followed by 50 ml of saline solution. In all the animals, a power injector was used for administering the contrast material, with an injection rate of 4 ml/s and a pressure of 4.7 to 5.7 kg/cm(2). Attenuation values were obtained from the right and left maxillary arteries and dorsal sagittal sinus. There were no significant differences in the maximum enhancement value (MEV) of the maxillary arteries and dorsal sagittal sinus between groups A and B. The MEVs of the maxillary arteries and dorsal sagittal sinus in groups A and B were significantly greater than the MEV in group C (P<0.05). The use of a saline chaser allowed a 30 per cent reduction in the dose of contrast material without decreasing vascular enhancement.