Collins, Jeremy D.

BackgroundSystematic evaluation of complex flow in the true lumen and false lumen (TL, FL) is needed to better understand which patients with chronic descending aortic dissection (DAD) are predisposed to complications.PurposeTo develop quantitative hemodynamic maps from 4D flow MRI for evaluating TL and FL flow characteristics.Study TypeRetrospective.PopulationIn all, 20 DAD patients (age = 60 ± 11 years; 12 male) (six medically managed type B AD [TBAD], 14 repaired type A AD [rTAAD] now with ascending aortic graft [AAo] or elephant trunk [ET1] repair) and 21 age‐matched controls (age = 59 ± 10 years; 13 male) were included.Field Strength/Sequence1.5T, 3T, 4D flow MRI.Assessment4D flow MRI was acquired in all subjects. Data analysis included 3D segmentation of TL and FL and voxelwise calculation of forward flow, reverse flow, flow stasis, and kinetic energy as quantitative hemodynamics maps.Statistical TestsAnalysis of variance (ANOVA) or Kruskal–Wallis tests were performed for comparing subject groups. Correlation and Bland–Altman analysis was performed for the interobserver study.ResultsPatients with rTAAD presented with elevated TL reverse flow (AAo repair: P = 0.004, ET1: P = 0.018) and increased TL kinetic energy (AAo repair: P = 0.0002, ET1: P = 0.011) compared to controls. In addition, TL kinetic energy was increased vs. patients with TBAD (AAo repair: P = 0.021, ET1: P = 0.048). rTAAD was associated with higher FL kinetic energy and lower FL stasis compared to patients with TBAD (AAo repair: P = 0.002, ET1: P = 0.024 and AAo repair: P = 0.003, ET1: P = 0.048, respectively).Data ConclusionQuantitative maps from 4D flow MRI demonstrated global and regional hemodynamic differences between DAD patients and controls. Patients with rTAAD vs. TBAD had significantly altered regional TL and FL hemodynamics. These findings indicate the potential of 4D flow MRI‐derived hemodynamic maps to help better evaluate patients with DAD.Level of Evidence: 3Technical Efficacy Stage: 1J. Magn. Reson. Imaging 2020;51:1357–1368.

Abstract Background Deaths in gluteal autografting occur due to gluteal vein injuries, but data are lacking on the precise location and caliber of these veins. Objectives The authors sought to present the first in vivo study of gluteal vein anatomy utilizing magnetic resonance imaging. Methods Magnetic resonance imaging venography of 16 volunteer hemi-sections was conducted in the supine, prone, prone with a bump (jack-knife), and left and right decubitus positions in 1 session after a single contrast administration. Caliber and course of the superior and inferior gluteal veins (SGV/IGV) were analyzed vs bony landmarks and position changes. Results The SGV has a very short submuscular course before splitting into 2 smaller branches superolaterally. The IGV runs immediately deep to the gluteus maximus in the center of the buttock as a single large trunk, on average 56 mm deep (mean 27 mm of muscle belly and 30 mm subcutaneous fat). No intramuscular or subcutaneous branches greater than 2 mm were found. In the prone position, the IGV and SGV have an average caliber of 5.96 mm and 5.63 mm. Vessel caliber decreased by 21% and 27%, respectively, in the jack-knife position and by 14% and 15% in lateral decubitus. Conclusions The SGV and IGV are immediately deep to gluteus maximus approximately 6 cm deep with a caliber on the order of 6 mm in the prone position. The distribution of these vessels suggests there is no “safe zone” in the intramuscular or submuscular planes. The jackknife or lateral decubitus positions can decrease vein caliber by up to 27%, possibly reducing the risk of injury due to either traction or direct cannula impact.