A practical biphasic contrast media injection protocol strongly enhances the aorta and pulmonary artery simultaneously using a single CT angiography scan

Background Enhancement profiles of the pulmonary artery (PA) and aorta differ when using computed tomography (CT) angiography. Our aim was to determine the optimal CT protocol for a one-time CT scan that assesses both blood vessels. Methods We prospectively enrolled 101 cases of CT angiography in patients with suspected pulmonary embolism or aortic dissection from our center between 2018 and 2020. We also retrospectively collected the data of 40 patients who underwent traditional two-time CT scans between 2015 and 2018. Patients were divided into four groups: test bolus (TB) I, TB II, bolus-tracking (BT) I, and BT II. The enhancement of the PA and aorta, and the radiation doses used in the four groups were collected. Those who underwent two-time scans were classified into the traditional PA or aorta scan groups. Data were compared between the BT and traditional groups. Results The aortic enhancement was highest in BT II (294.78 ± 64.48 HU) followed BT I (285.18 ± 64.99 HU), TB II (186.58 ± 57.53 HU), and TB I (173.62 ± 69.70 HU). The radiation dose used was lowest in BT I (11.85 ± 5.55 mSv) and BT II (9.07 ± 3.44 mSv) compared with that used in the traditional groups (20.07 ± 7.78 mSv) and accounted for half of the traditional group (45.17–59.02%). The aortic enhancement was also highest in BT II (294.78 ± 64.48 HU) followed by BT I (285.18 ± 64.99 HU) when compared with that in the traditional aorta scan group (234.95 ± 94.18 HU). Conclusion Our CT protocol with a BT technique allows for a lower radiation dose and better image quality of the PA and aorta than those obtained using traditional CT scans. Trial registration: NCT04832633, retrospectively registered in April 2021 to the clinical trial registry.

Visualization of extracranial-intracranial bypass in moyamoya patients using intraoperative three-dimensional digital subtraction angiography with intravenous contrast injection and robotic C-arm: patient series

BACKGROUNDThe authors describe a noninvasive intraoperative imaging strategy of three-dimensional (3D) digital subtraction angiography (DSA) with intravenous (IV) contrast injection, using indocyanine green (ICG) as a test bolus, during extracranial-intracranial (EC-IC) bypass surgery for moyamoya disease.OBSERVATIONSFour patients underwent EC-IC bypass surgery in a hybrid operating room. During the surgery, bypass patency was verified using ICG videoangiography and Doppler ultrasonography. After skin closure, the patients under anesthesia underwent IV 3D-DSA with a robotic C-arm in which the scan delay time for the 3D-DSA scan was estimated from the arrival time of ICG during the ICG videoangiography. One day after the surgery, the patients underwent magnetic resonance angiography (MRA). The IV 3D-DSA images were retrospectively compared with those obtained with other modalities. Good bypass patency was confirmed on IV 3D-DSA, ICG videoangiography, Doppler ultrasonography, and postoperative MRA in all cases. The delay time determined using ICG videoangiography as a test bolus resulted in IV 3D-DSA with adequate image quality, allowing assessment of the spatial relationships between the vessels and anastomoses from all directions.LESSONSTo evaluate bypass patency and anatomical relationships immediately after EC-IC bypass surgery, IV 3D-DSA may be a useful modality. ICG videoangiography can be used to determine the scan delay time.

The feasibility of low iodine dynamic CT angiography with test bolus for evaluation of lower extremity peripheral artery disease

Objective This study aims to determine if low iodine dynamic computed tomography angiography performed after a fixed delay or test bolus acquisition demonstrates high concordance with clinical computed tomography angiography (using a routine amount of iodinated contrast) to display lower extremity peripheral arterial disease. Methods After informed consent, low iodine dynamic computed tomography angiography examination (using either a fixed delay or test bolus) using 50 ml of iodine contrast media was performed. A subsequent clinical computed tomography angiography using standard iodine dose (115 or 145 ml) served as the reference standard. A vascular radiologist reviewed dynamic and clinical computed tomography angiography images to categorize the lumen into “not opacified”, “<50% stenosis”, “ 50 ̶70% stenosis”, “>70% stenosis”, and “occluded” for seven arterial segments in each lower extremity. Concordance between low iodine dynamic computed tomography angiography and the routine iodine reference standard was calculated. The clinical utility of 4D volume-rendered images was also evaluated. Results Sixty-eight patients (average age 66.1 ± 12.3 years, male; female = 49: 19) were enrolled, with 34 patients each undergoing low iodine dynamic computed tomography angiography using fixed delay and test bolus techniques, respectively. One patient assigned to the test bolus group did not undergo low iodine computed tomography angiography due to unavailable delayed time. The fixed delay was 13 s, with test bolus acquisition resulting in a mean variable delay prior to image acquisition of 19.5 s (range; 8–32 s). Run-off to the ankle was observed using low iodine dynamic computed tomography angiography following fixed delay and test bolus acquisition in 76.4% (26/34) and 100% (33/33) of patients, respectively ( p = 0.005). Considering extremities with run-off to the ankle and without severe artifact, the concordance rate between low iodine dynamic computed tomography angiography and the routine iodine reference standard was 86.8% (310/357) using fixed delay and 97.9% (425/434) using test bolus ( p < 0.001). 4D volume-rendered images using fixed delay and test bolus demonstrated asymmetric flow in 57.7% (15/26) and 58.1% (18/31) ( p = 0.978) of patients, and collateral blood flow in 11.5% (3/26) and 22.6% (7/31) of patients ( p = 0.319), respectively. Conclusion Low iodine dynamic computed tomography angiography with test bolus acquisition has a high concordance with routine peripheral computed tomography angiography performed with standard iodine dose, resulting in improved run-off to the ankle compared to dynamic computed tomography angiography performed after a fixed delay. This method is useful for minimizing iodine dose in patients at risk for contrast-induced nephropathy. 4D volume-rendered computed tomography angiography images provide useful dynamic information.

Estimation of cardiac output from test-bolus during coronary computed tomography angiography: a personalized mathematical model

Background Contrast enhancement is measured in the aorta at set intervals of time during the test-bolus series of a coronary computed tomography angiography [CCTA]. Its primary purpose is to ascertain the timing delay of the main scan after contrast administration to ensure optimal image acquisition. The change in contrast enhancement over time correlates directly with contrast medium concentration in the vessel. If the complete time density curve [TDC] is known and corrected for contrast enhancement due to recirculation it can be used to estimate the cardiac output [CO], by e.g. a modified Stewart-Hamilton equation, as shown by Mahnken et al. Purpose The current study aims to explore ways to improve the mathematical estimation of CO. In practical applications only part of the TDC is known. By integrating patient factors, contrast factors and scanning factors with a mathematical compartment model, the CO can be estimated. Estimated CO is subsequently used to simulate the distribution of contrast medium in the body, enabling prospective adjustment of contrast medium administration protocol that could be tailored to each individual, utilizing the lowest possible dose of contrast to achieve diagnostically acceptable CCTA images. Methods Test-bolus images were acquired sequentially at two second intervals over the aorta from 40 patients with a clinical indication for CCTA. According to clinical routines, premedication with beta-blockers was performed in 35 patients and sublingual nitroglycerine in 39 patients. Attenuation in the aorta was measured by a centrally placed region of interest with a width of half the aortic diameter. Each participant underwent cardiac magnetic resonance imaging [MRI] immediately after CCTA, from which actual CO was measured as a method of validation. A mathematical compartment model for distribution of contrast, outlined by Bae et al. was improved and used to estimate the CO from the TDC in the aorta during the test-bolus. The estimated CO [COEst] was compared with CO calculated from MRI [COMR], and estimated attenuation in the aorta [HUEst] was compared with measured attenuation in the aorta during test-bolus in CCTA [HUCT]. Results One patient was excluded due to unacceptable cardiac MRI. Our model showed a strong correlation between COEst and COMR for all patients (r=0.62, p&lt;0.001) and a higher correlation for women than men when separated by gender (men r=0.58, p=0.006; women r=0.63, p=0.005). Women had an average COEst 1.92 L/min significantly lower than men (p&lt;0.001), despite no statistical difference in COMR between men and women. Conclusion An improved mathematical model for estimation of CO can be a valuable tool to improve individualized contrast administration protocols and increase the diagnostic information extracted from a CCTA. In addition to known physical factors it is clear that gender and weight, including their derivatives, must play a more significant role in estimation. Funding Acknowledgement Type of funding source: Public hospital(s). Main funding source(s): Stavanger University Hospital

Successful depiction of systemic collateral supply to pulmonary artery in CTEPH using time-resolved 4D CT angiography: a case report

A 49-year-old man with CTEPH (pre-procedural mean pulmonary artery pressure: 36 mmHg) underwent balloon pulmonary angioplasty. Chronic total occlusion of the left inferior pulmonary artery trunk was observed. To evaluate the collateral vessels of the chronic total occlusion, 4D-CTA was performed. The examination was performed using a 256-row detector CT system using the test bolus tracking method. 4D-CTA showed the bronchial artery-to-left inferior pulmonary artery collateral supply, which was confirmed by a selective bronchial artery angiography. The patient’s symptoms improved with balloon pulmonary angioplasty of the other stenotic lesions. 4D-CTA can noninvasively evaluate the anatomy and hemodynamics of multiple systemic collaterals simultaneously. This technique can support interventions in systemic artery-to-pulmonary artery collaterals, such as embolization, and could be helpful in challenging balloon pulmonary angioplasty interventions for chronic total occlusion to identify vessel structures distal to the chronic total occlusion and collateral channels for a retrograde approach.