CT Angiography of the Aorta: Contrast Timing by Using a Fixed versus a Patient-specific Trigger Delay

Abstract

Background Optimal timing of the CT scan relative to the contrast media bolus remains a challenging task given the shorter scan durations of modern CT scanners, as well as interpatient variability. Purpose To compare contrast opacification in CT angiography of the aorta between a cohort with fixed trigger delay and a cohort with patient-specific individualized trigger delay for contrast media timing with bolus tracking. Materials and Methods In this prospective study (January-August 2018), CT angiography of the thoracoabdominal aorta with bolus tracking was performed in two different study cohorts: one with a fixed trigger delay of 4 seconds (fixed cohort) and one with a patient-specific trigger delay (individualized cohort). All CT and contrast media protocol parameters were kept identical among cohorts. Objective image quality was evaluated by one reader; two readers assessed subjective image quality. Student test was used to test for differences in mean attenuation; the Wilcoxon-Mann-Whitney test was used to test for differences in noise, contrast-to-noise ratio, and subjective image quality. Results The fixed cohort had 108 study participants (16 women; mean age ± standard deviation, 72 years ± 10); the individualized cohort had 108 participants (16 women; mean age, 72 years ± 12). The trigger delay in the individualized cohort ranged from 6.4-11.3 seconds (mean, 9.2 seconds). There was higher overall attenuation in the individualized cohort than in the fixed cohort (486 HU ± 92 for individualized vs 438 HU ± 99 for fixed; < .001), with increasing differences from the aortic arch (8 HU) to the iliac arteries (95 HU). The regression model indicated uniform attenuation in the individualized cohort and decreasing attenuation in the fixed cohort (decrease of 87 HU by the iliac arteries; < .001). There was no difference between cohorts for image noise (20 vs 19; = .41), but contrast-to-noise ratio (21 vs 19; = .04) and subjective image quality were higher in the individualized cohort than in the fixed cohort (excellent or good image quality, 100% vs 67%; < .001). Conclusion Compared with a fixed delay time after bolus tracking, a patient-specific individualized trigger delay improves image quality and provides uniform contrast attenuation for CT angiography of the aorta. ©RSNA, 2019.

Use of artificial intelligence in computed tomography dose optimisation

“…Based on these data, an algorithm is able to predict the ultimate height and width of the resulting contrast enhancement curve in the aorta. In subsequent patients beyond the training data, the system can predict the whole contrast enhancement curve using only a few data points on the rising edge of the curve, based upon which the optimal timing of the scan to be performed can be set as the contrast is flowing through the patient (Hinzpeter et al., 2019). Clinical studies have demonstrated better uniformity of contrast enhancement over the scan range in parallel to a reduction in the required dose of iodinated contrast media.…”

Machine Learning and Deep Neural Networks

“…2). 18,20 This algorithm uses the first few The Avatar hull is computed and the table height at which the 3D camera planning image was taken is then adjusted such that the Avatar center and thus the patient is aligned in the isocenter of the computed tomography scanner (B).…”

“…18 This technique showed its robustness in cardiac and thoracoabdominal CTA studies resulting in an improved and constant image quality compared with a fixed posttrigger delay, yielding a uniform contrast attenuation of the thoracoabdominal aorta independent of the cardiovascular situation of the individual patient. 18,20 The personalized bolus-tracking permits also diagnostic CTA examinations despite slower injection rates and less iodine in CTA of the abdomen. 20 The software for personalized contrast media application described above is not yet commercially available.…”

“…18,20 The personalized bolus-tracking permits also diagnostic CTA examinations despite slower injection rates and less iodine in CTA of the abdomen. 20 The software for personalized contrast media application described above is not yet commercially available.…”

An optimized test bolus for computed tomography pulmonary angiography and its application at 80 kV with 10 ml contrast agent

“…For fast multidetector CT, an additional delay is usually used 6 . Low kilovoltage scanning based on a small volume of contrast media also affects the determination of the scanning time 7 . Moreover, venous contamination usually occurred in the bolus tracking system 8 .…”