To prospectively determine the range of aortopopliteal bolus transit times in patients with moderate-to-severe peripheral arterial occlusive disease (PAOD) as a guideline for developing injection strategies for computed tomographic (CT) angiography of peripheral arteries.The study protocol was approved by the local ethics board, and informed consent was obtained. Twenty patients with PAOD referred for CT angiography of the lower extremities were categorized into two groups, Fontaine stage IIb (group 1) and stage III or IV (group 2), and demographic information was collected. In all patients, a 16-mL test bolus was injected intravenously, and single-level dynamic acquisitions were obtained at the level of the abdominal aorta. After injection of a second 16-mL test bolus, dynamic acquisitions were obtained at the level of the knee (popliteal arteries). Aortopopliteal bolus transit times were calculated by subtracting the time to peak enhancement in the popliteal arteries from that in the aorta. Aortopopliteal transit speeds also were derived. Transit times and speeds were compared graphically between clinical stage groups. The time required for the contrast medium to enhance the entire peripheral arterial tree in patients with PAOD was estimated by using linear extrapolation.Sixteen men and four women with a mean age of 69 years (range, 49-86 years) were included. Twelve patients were included in group 1, and eight patients, in group 2. Aortopopliteal bolus transit times ranged from 4 to 24 seconds (median, 8 seconds) in all subjects, which corresponded to bolus transit speeds of 177 and 29 mm/sec, respectively. Wide overlap of transit times and transit speeds was observed between clinical stage groups. The estimated time needed for the bolus to enhance the entire peripheral arterial tree was 6-39 seconds.Aortopopliteal bolus transit times differ widely among patients and may be substantially delayed in all patients with PAOD. Empirical injection protocols should include an injection duration of 35 seconds or more, as well as an increased scanning delay, with table speeds of more than 30 mm/sec.
The objective of this study is to evaluate the safety and quality of computed tomographic angiography of the thoracic aorta (CTA-TA) exams performed using intraosseous needle intravenous access (ION-IVA) for contrast media injection (CMI).All CTA-TA exams at the study institution performed between 1/1/2013 and 8/14/2015 were reviewed retrospectively to identify those exams which had been performed using ION-IVA (ION-exams). ION-exams were then analyzed to determine aortic attenuation and contrast-to-noise ratio (CNR). Linear regression was used to determine how injection rate and other variables affected image quality for ION-exams. Patient electronic medical records were reviewed to identify any adverse events related to CTA-TA or ION-IVA.17 (∼0.2%) of 7401 exams were ION-exams. ION-exam CMI rates varied between 2.5 and 4 ml/s. Mean attenuation was 312 HU (SD 88 HU) and mean CNR was 25 (SD 9.9). A strong positive linear association between attenuation and injection rate was found. No immediate or delayed complications related to the ION-exams, or intraosseous needle use in general, occurred.For CTA-TA, ION-IVA appears to be a safe and effective route for CMI at rates up to 4 ml/s.
Introduction: Medical treatment of uncomplicated Stanford type-B aortic dissection (AD) is associated with a high rate of late adverse events (AE). Endografting may prevent late complications, however, initial trials failed to demonstrate a survival benefit in the first two years. We hypothesize that morphologic features at the initial hospitalization are associated with AE and could aid in the risk stratification of patients with AD. Methods: Eighty-three patients with acute uncomplicated type-B AD were retrospectively identified at two aortic centers in the US and EU. Multiple clinical and morphologic features - including true vs. false lumen blood supply - were identified on high-quality CT scans and followed. Multivariable Cox proportional hazards regression was used to evaluate the associations between candidate predictors and AE - defined as rapid growth, aneurysm formation (≥6cm), organ ischemia, and fatal or non-fatal aortic rupture, and develop an internally validated risk score. Results: AE were observed in 33 patients over a median 850 (IQR 247-1824) days follow up. Five significant predictors were identified in the multivariable model: Connective tissue disease (HR 2.94, 95% CI: 1.29 - 6.72, p= 0.01), circumferential extent of false lumen in angular degrees (HR 1.03, 95% CI: 1.01 - 1.04, p= 0.003), maximum aortic diameter in mm (HR 1.10, 95% CI: 1.02 - 1.18, p= 0.015), false lumen outflow in mL/min (HR 0.999, 95% CI: 0.998 - 1.000, p= 0.055), and number of intercostal arteries (HR 0.89, 95% CI: 0.80 - 0.98), p= 0.024). A model combining these five factors was constructed to calculate patient specific risk scores allowing stratification into high, intermediate, and low risk terciles. The model showed good discriminatory ability with an optimism-corrected c-statistic of 70.1%. Conclusion: Morphologic features predict late AE in uncomplicated type-B AD. If externally validated this may identify high-risk patients who benefit from early endografting.
Understanding flow dynamics in type-B aortic dissection (TBAD) is of high clinical interest to predict complications and individualize treatment. Here, we sought to evaluate 4D-flow MRI at high and low spatial image resolution, in comparison to high resolution, high signal-to-noise 2D phase contrast MRI. Further, we compare TBAD hemodynamics and flow alterations owing to changes in tear size. We leverage novel 3D printing technology to manufacture three compliant TBAD models with altered tear morphology and perform pressure- and flow-controlled MRI with an advanced in vitro flow setup.
