Failure of Real-time Passive Notification about Radiation Exposure to Influence Physician Ordering Behavior.

Objectives  To determine whether real-time passive notification of patient radiation exposure via a computerized physician order entry system would alter the number of computed tomography scans ordered by physicians in the Emergency Department (ED) setting. Methods  When a practitioner ordered a computed tomography scan, a passive notification was immediately and prominently displayed via the computerized physician order entry system. The notification stated the following: the amount of estimated radiation in millisieverts (mSv), the equivalent number of single-view chest radiographs, and equivalent days of average environmental background radiation to which a patient during a specific computed tomography scan would be exposed. The primary outcome was changed in the number of computed tomography scans ordered when comparing data collected before and after the addition of the notification. Results  Before the dosimetry notification ("intervention") was instituted, 1,747 computed tomography scans were performed on patients during 11,709 Emergency Department visits (14.9% computed tomography scan rate). After the intervention had been instituted, 1,827 computed tomography scans were performed on patients during 11,582 Emergency Department patient visits (15.8% computed tomography scan rate). No statistically significant difference was found for all chief complaints combined (p = 0.17), or for any individual chief complaint, between the number of computed tomography scans performed on Emergency Department patients before versus after the intervention. Conclusions  Passive real-time notification of patient radiation exposure displayed in a computerized physician order entry system at the time of computed tomography scan ordering in the Emergency Department did not significantly change the number of ordered scans.

Three-Dimensional Modeling Analysis of Visceral Arteries and Kidneys during Respiration.

BACKGROUND: Visceral arteries are commonly involved in endovascular repair of complex abdominal aortic aneurysms (AAAs). To improve repair techniques and reduce long-term complications involving visceral arteries, it is crucial to understand in vivo arterial geometry and the deformations due to visceral organ movement with respiration. This study quantifies deformation of the celiac, superior mesenteric (SMA), and renal arteries during respiration and correlates the deformations with diaphragmatic excursion. METHODS: Sixteen patients with small AAAs underwent magnetic resonance angiography during inspiratory and expiratory breathholds. From geometric models of the aorta and visceral arteries, vessel length, branch angle, curvature, and positions were computed, along with degree of diaphragmatic excursion as indicated by kidney translation. RESULTS: From inspiration to expiration, the celiac artery exhibited axial shortening of 4.8 ± 6.4% (P < 0.001) and a mean curvature increase of 0.03 ± 0.02 mm(-1), greater than other visceral arteries (P < 0.01). With expiration, the SMA, left and right renal arteries (LRA and RRA) angled upward by -9.8 ± 6.4°, -6.4 ± 6.4°, and -5.2 ± 5.0°, respectively (P < 0.005). All vessels translated superiorly (P < 0.0005) and posteriorly (P < 0.01), and the SMA translated rightward additionally (P < 0.005). The left and right kidneys translated by 22 ± 9 mm and 21 ± 9 mm, mostly superiorly (P < 0.001). Translations of all visceral arteries were moderately correlated to the right kidney (R > 0.50). Correlation of the LRA with the left kidney was greater than that of the RRA with the right kidney. CONCLUSIONS: The celiac artery exhibited less branch angle change, and greater axial and curvature deformations than the other visceral arteries, due to the vicinity to the liver and influence of the median arcuate ligament. Correlation between visceral arteries and kidney translations revealed that diaphragmatic excursion affects vessel mobility. Weaker correlation of the RRA to the right kidney indicates mechanical shielding from the inferior vena cava.

Greater asymmetric wall shear stress in Sievers' type 1/LR compared with 0/LAT bicuspid aortic valves after valve-sparing aortic root replacement.

OBJECTIVE: To evaluate the role of commissure orientation on downstream blood flow patterns and ascending aortic wall shear stress (WSS) in patients with bicuspid aortic valves (BAV) after valve-sparing aortic root replacement (V-SARR). METHODS: Nineteen BAV patients after V-SARR (9 Sievers' type 1/LR [type 1 valve with fusion of the left and right cusps] and 10 Sievers' type 0/LAT ["naturally perfect"; type 0 valve without the presence of a raphe, and with the 2 commissures oriented right-anterior-to-left-posterior]) were imaged using time-resolved 3-D phase contrast magnetic resonance imaging. A control group of 5 unoperated tricuspid aortic valve patients were used for comparison purposes. Wall shear stress and eccentricity of flow normalized to aortic diameter were measured in planes placed perpendicular to the axis of the ascending aorta at the level of the sinotubular junction (proximal ascending), main pulmonary artery (mid-ascending), and origin of the brachiocephalic (distal ascending). RESULTS: The ratio of WSS along the outer curvature to that along the inner curvature was greater in Sievers' type 1/LR patients compared with Sievers' type 0/LAT patients in the proximal (3.8 ± 1.6 vs 2.1 ± 0.9, P = .009) and mid- ascending aorta (4.5 ± 2.4 vs 2.4 ± 1.3, P = .027). Relative to control normal tricuspid patients, Sievers' type 1/LR BAV patients had a higher WSS ratio in the mid-ascending aorta (4.5 ± 2.4 vs 1.2 ± 1.2, P = .007). Conversely, WSS in Sievers' type 0/LAT patients was not different than in normal tricuspid patients. CONCLUSIONS: After V-SARR, BAV cusp morphology has a major impact on the pattern of blood flow and WSS in the ascending aorta.

Putting the fat and water protons to work for you: a demonstration through clinical cases of how fat-water separation techniques can benefit your body MRI practice.

OBJECTIVE: Separation methods exploit the different precessional frequencies of fat and water protons. They offer potential benefits to body MRI but are not routinely used in most practices. After a review of the technique, we highlight through cases promising applications of this technology, including using water-only series to obtain more robust fat-suppressed images, shortening MRI scanning protocol time, and achieving perfect coregistering of fat-suppressed and non-fat-suppressed images. CONCLUSION: As technology has advanced, fat-water separation techniques have shown that they can be valuable tools for a body MRI practice, particularly when the presence or absence of fat, homogeneity of fat saturation, coregistration, or quantitative evaluation is critical.

2013 ACCF/ACR/ASE/ASNC/SCCT/SCMR appropriate utilization of cardiovascular imaging in heart failure: an executive summary: a joint report of the ACR Appropriateness Criteria ® Committee and the ACCF Appropriate Use Criteria Task Force.

The ACR and the American College of Cardiology Foundation (ACCF) developed a joint process for determining the appropriate utilization (AU) of cardiovascular imaging modalities in heart failure (HF). This report represents an executive summary of the AU document which was aimed at critically and systematically creating, reviewing, and categorizing clinical situations where physicians order or use imaging tests for patients with suspected, incompletely characterized, or known HF.

Respiration-induced deformations of the superior mesenteric and renal arteries in patients with abdominal aortic aneurysms.

PURPOSE: To quantify respiration-induced deformations of the superior mesenteric artery (SMA), left renal artery (LRA), and right renal artery (RRA) in patients with small abdominal aortic aneurysms (AAAs). MATERIALS AND METHODS: Sixteen men with AAAs (age 73 y ± 7) were imaged with contrast-enhanced magnetic resonance angiography during inspiratory and expiratory breath-holds. Centerline paths of the aorta and visceral arteries were acquired by geometric modeling and segmentation techniques. Vessel translations and changes in branching angle and curvature resulting from respiration were computed from centerline paths. RESULTS: With expiration, the SMA, LRA, and RRA bifurcation points translated superiorly by 12.4 mm ± 9.5, 14.5 mm ± 8.8, and 12.7 mm ± 6.4 (P < .001), and posteriorly by 2.2 mm ± 2.7, 4.9 mm ± 4.2, and 5.6 mm ± 3.9 (P < .05), respectively, and the SMA translated rightward by 3.9 mm ± 4.9 (P < .01). With expiration, the SMA, LRA, and RRA angled upward by 9.7° ± 6.4, 7.5° ± 7.8, and 4.9° ± 5.3, respectively (P < .005). With expiration, mean curvature increased by 0.02 mm(-1) ± 0.01, 0.01 mm(-1) ± 0.01, and 0.01 mm(-1) ± 0.01 in the SMA, LRA, and RRA, respectively (P < .05). For inspiration and expiration, RRA curvature was greater than in other vessels (P < .025). CONCLUSIONS: With expiration, the SMA, LRA, and RRA translated superiorly and posteriorly as a result of diaphragmatic motion, inducing upward angling of vessel branches and increased curvature. In addition, the SMA exhibited rightward translation with expiration. The RRA was significantly more tortuous, but deformed less than the other vessels during respiration.

Evaluation of Marfan patients status post valve-sparing aortic root replacement with 4D flow.

BACKGROUND: Over the past two decades elective valve-sparing aortic root replacement (V-SARR) has become more common in the treatment of patients with aortic root and ascending aortic aneurysms. Currently there are little data available to predict complications in the post-operative population. The study goal was to determine if altered flow patterns in the thoracic aorta, as measured by MRI, are associated with complications after V-SARR. METHODS: Time-resolved three-dimensional phase-contrast MRI (4D flow) was used to image 12 patients with Marfan syndrome after V-SARR. The patients were followed up for an average of 5.8 years after imaging and 8.2 years after surgery. Additionally 5 volunteers were imaged for comparison. Flow profiles were visualized during peak systole using streamlines. Wall shear stress estimates and normalized flow displacement were evaluated at multiple planes in the thoracic aorta. RESULTS: During the follow-up period, a single patient developed a Stanford Type B aortic dissection. At initial imaging, prior to the development of the dissection, the patient had altered flow patterns, wall shear stress estimates, and increased normalized flow displacement in the thoracic aorta in comparison to the remaining V-SARR patients and volunteers. CONCLUSIONS: This is the first follow-up study of patients after 4D flow imaging. An aortic dissection developed in one patient with altered flow patterns and hemodynamic stresses in the thoracic aorta. These results suggest that flow and altered hemodynamics may play a role in the development of post-operative intramural hematomas and dissections.

Respiratory-induced 3D deformations of the renal arteries quantified with geometric modeling during inspiration and expiration breath-holds of magnetic resonance angiography.

PURPOSE: To quantify renal artery deformation due to respiration using magnetic resonance (MR) image-based geometric analysis. MATERIALS AND METHODS: Five males were imaged with contrast-enhanced MR angiography during inspiratory and expiratory breath-holds. From 3D models of the abdominal aorta, left and right renal arteries (LRA and RRA), we quantified branching angle, curvature, peak curve angle, axial length, and locations of branch points. RESULTS: With expiration, maximum curvature changes were 0.054 ± 0.025 mm(-1) (P < 0.01), and curve angle at the most proximal curvature peak increased by 8.0 ± 4.5° (P < 0.05) in the LRA. Changes in maximum curvature and curve angles were not significant in the RRA. The first renal bifurcation point translated superiorly and posteriorly by 9.7 ± 3.6 mm (P < 0.005) and 3.5 ± 2.1 mm (P < 0.05), respectively, in the LRA, and 10.8 ± 6.1 mm (P < 0.05) and 3.6 ± 2.5 mm (P < 0.05), respectively, in the RRA. Changes in branching angle, axial length, and renal ostia locations were not significant. CONCLUSION: The LRA and RRA deformed and translated significantly. Greater deformation of the LRA as compared to the RRA may be due to asymmetric anatomy and mechanical support by the inferior vena cava. The presented methodology can extend to quantification of deformation of diseased and stented arteries to help renal artery implant development.

Improvement of gadoxetate arterial phase capture with a high spatio-temporal resolution multiphase three-dimensional SPGR-Dixon sequence.

PURPOSE: To determine whether a multiphase method with high spatiotemporal resolution (STR) by means of a combination of parallel imaging, pseudorandom sampling and temporal view sharing improves the capture and intensity of gadoxetate arterial phase images as well as lesion enhancement. MATERIALS AND METHODS: Thirty-seven patients were imaged with a conventional spoiled gradient echo acquisition and 48 with a high STR multiphase acquisition after the administration of gadoxetate. Arterial phase capture, image quality, and quality of fat suppression were qualitatively graded. Fourteen lesions in the conventional group and 28 in the high STR multiphase group were imaged, including 34 focal nodular hyperplasias. The ratio of lesion to parenchyma enhancement as well as relative hepatic artery enhancement were calculated. Chi-squared, Mann-Whitney U and student t-tests were used to compare differences. RESULTS: The high STR multiphase acquisition included the arterial phase more frequently than conventional acquisitions (P < 0.001), with the arterial phase missed in 17% (95% CI of 4-28%) of patients with conventional acquisition compared with 2% (95% CI of 0-6%) with the high STR multiphase acquisition. There was no loss of image quality or degree of fat saturation. Additionally, there was increased relative intensity of the hepatic arteries (P < 0.001) as well as lesion enhancement (P = 0.01). CONCLUSION: The high STR multiphase acquisition resulted in more reliable gadoxetate arterial phase capture compared with a conventional acquisition while preserving image quality with robust fat saturation.

Rapid pediatric cardiac assessment of flow and ventricular volume with compressed sensing parallel imaging volumetric cine phase-contrast MRI.

OBJECTIVE: The quantification of cardiac flow and ventricular volumes is an essential goal of many congenital heart MRI examinations, often requiring acquisition of multiple 2D phase-contrast and bright-blood cine steady-state free precession (SSFP) planes. Scan acquisition, however, is lengthy and highly reliant on an imager who is well-versed in structural heart disease. Although it can also be lengthy, 3D time-resolved (4D) phase-contrast MRI yields global flow patterns and is simpler to perform. We therefore sought to accelerate 4D phase contrast and to determine whether equivalent flow and volume measurements could be extracted. MATERIALS AND METHODS: Four-dimensional phase contrast was modified for higher acceleration with compressed sensing. Custom software was developed to process 4D phase-contrast images. We studied 29 patients referred for congenital cardiac MRI who underwent a routine clinical protocol, including cine short-axis stack SSFP and 2D phase contrast, followed by contrast-enhanced 4D phase contrast. To compare quantitative measurements, Bland-Altman analysis, paired Student t tests, and F tests were used. RESULTS: Ventricular end-diastolic, end-systolic, and stroke volumes obtained from 4D phase contrast and SSFP were well correlated (ρ = 0.91-0.95; r(2) = 0.83-0.90), with no statistically significant difference. Ejection fractions were well correlated in a subpopulation that underwent higher-resolution compressed-sensing 4D phase contrast (ρ = 0.88; r(2) = 0.77). Four-dimensional phase contrast and 2D phase contrast flow rates were also well correlated (ρ = 0.90; r(2) = 0.82). Excluding ventricles with valvular insufficiency, cardiac outputs derived from outlet valve flow and stroke volumes were more consistent by 4D phase contrast than by 2D phase contrast and SSFP. CONCLUSION: Combined parallel imaging and compressed sensing can be applied to 4D phase contrast. With custom software, flow and ventricular volumes may be extracted with comparable accuracy to SSFP and 2D phase contrast. Furthermore, cardiac outputs were more consistent by 4D phase contrast.

Cardiac imaging: Part 2, normal, variant, and anomalous configurations of the coronary vasculature.

OBJECTIVE: Noninvasive imaging of the heart and coronary vasculature using CT and MRI is a new and exciting opportunity for radiologists. The purpose of this pictorial essay is to review normal and variant anatomy of the coronary arteries and of several coronary anomalies that may be clinically significant. The coronary veins and artifacts simulating disease will also be briefly covered. This article will help radiologists learn and review normal coronary anatomy, normal variants, and coronary anomalies and recognize pitfalls, such as coronary veins and artifacts, that may be confusing when first encountered. CONCLUSION: The coronary arteries generally are predictable in their origin, course, and perfusion territories. Standardized reporting systems exist for describing the location of specific lesions, and radiologists who interpret CT and MR coronary images should be aware of and should attempt to integrate these reporting schemes into clinical practice.

Hemodynamic changes quantified in abdominal aortic aneurysms with increasing exercise intensity using mr exercise imaging and image-based computational fluid dynamics.

Abdominal aortic aneurysm (AAA) is a vascular disease resulting in a permanent, localized enlargement of the abdominal aorta. We previously hypothesized that the progression of AAA may be slowed by altering the hemodynamics in the abdominal aorta through exercise [Dalman, R. L., M. M. Tedesco, J. Myers, and C. A. Taylor. Ann. N.Y. Acad. Sci. 1085:92-109, 2006]. To quantify the effect of exercise intensity on hemodynamic conditions in 10 AAA subjects at rest and during mild and moderate intensities of lower-limb exercise (defined as 33 ± 10% and 63 ± 18% increase above resting heart rate, respectively), we used magnetic resonance imaging and computational fluid dynamics techniques. Subject-specific models were constructed from magnetic resonance angiography data and physiologic boundary conditions were derived from measurements made during dynamic exercise. We measured the abdominal aortic blood flow at rest and during exercise, and quantified mean wall shear stress (MWSS), oscillatory shear index (OSI), and particle residence time (PRT). We observed that an increase in the level of activity correlated with an increase of MWSS and a decrease of OSI at three locations in the abdominal aorta, and these changes were most significant below the renal arteries. As the level of activity increased, PRT in the aneurysm was significantly decreased: 50% of particles were cleared out of AAAs within 1.36 ± 0.43, 0.34 ± 0.10, and 0.22 ± 0.06 s at rest, mild exercise, and moderate exercise levels, respectively. Most of the reduction of PRT occurred from rest to the mild exercise level, suggesting that mild exercise may be sufficient to reduce flow stasis in AAAs.

Intraprocedure visualization of the esophagus using interventional C-arm CT as guidance for left atrial radiofrequency ablation.

RATIONALE AND OBJECTIVES: During radiofrequency catheter ablation for atrial fibrillation, the esophagus is at risk for thermal injury. In this study, C-arm computed tomography (CT) was compared to clinical CT, without the administration of oral contrast, to visualize the esophagus and its relationship to the left atrium and the ostia of the pulmonary veins (PVs) during the radiofrequency ablation procedure. MATERIALS AND METHODS: Sixteen subjects underwent both cardiac clinical CT and C-arm CT. Computed tomographic scans were performed on a multidetector scanner using a standard electrocardiographically gated protocol. C-arm computed tomographic scans were obtained using either a multisweep protocol with retrospective electrocardiographic gating or a non-gated single-sweep protocol. C-arm and clinical computed tomographic scans were analyzed in a random order and then compared for the following criteria: (1) visualization of the esophagus (yes or no), (2) relationship of esophageal position to the four PVs, and (3) direct contact or absence of a fat pad between the esophagus and the PV antrum. RESULTS: The esophagus was identified in all C-arm and clinical computed tomographic scans. In four cases, orthogonal planes were needed on C-arm CT (inferior PV level). In six patients, the esophageal location on C-arm CT was different from that on CT. Direct contact was reported in 19 of 64 of the segments (30%) examined on CT and in 26 of 64 (41%) on C-arm CT. In five of 64 segments (8%), C-arm CT overestimated a direct contact of the esophagus to the left atrium. CONCLUSIONS: C-arm computed tomographic image quality without the administration of oral contrast agents was shown to be sufficient for visualization of the esophagus location during a radiofrequency catheter ablation procedure for atrial fibrillation.

In-vivo imaging of femoral artery nitinol stents for deformation analysis.

PURPOSE: The authors have developed a direct method to study femoral artery stent deformations in vivo. A previously described imaging and analysis approach based on a calibrated phantom was used to examine stents in human volunteers treated for atherosclerotic disease. In this pilot study, forces on stents were evaluated under different in-vivo flexion conditions. MATERIALS AND METHODS: The optimized imaging protocol for imaging with a C-arm computed tomography system was first verified in an in-vivo porcine stent model. Human data were obtained by imaging 13 consenting volunteers with stents in femoral vessels. The affected leg was imaged in straight and bent positions to observe stent deformations. Semiautomatic software was used to calculate the changes in bending, extension, and torsion on the stents for the two positions. RESULTS: For the human studies, tension and bending calculation were successful. Bending was found to compress stent lengths by 4% ± 3% (-14.2 to 1.5 mm), increase their average eccentricity by 10% ± 9% (0.12 to -0.16), and change their mean curvature by 27% ± 22% (0 to -0.005 mm(-1)). Stents with the greatest change in eccentricity and curvature were located behind the knee or in the pelvis. Torsion calculations were difficult because the stents were untethered and are symmetric. In addition, multiple locations in each stent underwent torsional deformations. CONCLUSIONS: The imaging and analysis approach developed based on calibrated in vitro measurements was extended to in-vivo data. Bending and tension forces were successfully evaluated in this pilot study.

Improved cardiovascular flow quantification with time-resolved volumetric phase-contrast MRI.

BACKGROUND: Cardiovascular flow is commonly assessed with two-dimensional, phase-contrast MRI (2-D PC-MRI). However, scan prescription and acquisition over multiple planes is lengthy, often requires direct physician oversight and has inconsistent results. Time-resolved volumetric PC-MRI (4-D flow) may address these limitations. OBJECTIVE: We assess the degree of agreement and internal consistency between 2-D and 4-D flow quantification in our clinical population. MATERIALS AND METHODS: Software enabling flow calculation from 4-D flow was developed in Java. With IRB approval and HIPAA compliance, 18 consecutive patients without shunts were identified who underwent both (1) conventional 2-D PC-MRI of the aorta and main pulmonary artery and (2) 4-D flow imaging. Aortic and pulmonary flow rates were assessed with both techniques. RESULTS: Both methods showed general agreement in flow rates (ρ: 0.87-0.90). Systemic and pulmonary arterial flow rates were well-correlated (ρ: 4-D 0.98-0.99, 2-D 0.93), but more closely matched with 4-D (P < 0.05, Brown-Forsythe). Pulmonary flow rates were lower than systemic rates for 2-D (P < 0.05, two-sample t-test). In a sub-analysis of patients without pulmonary or aortic regurgitation, 2-D showed improved correlation of flow rates while 4-D phase-contrast remained tightly correlated (ρ: 4-D 0.99-1.00, 2-D 0.99). CONCLUSION: 4-D PC-MRI demonstrates greater consistency than conventional 2-D PC-MRI for flow quantification.

Quantification of particle residence time in abdominal aortic aneurysms using magnetic resonance imaging and computational fluid dynamics.

Hemodynamic conditions are hypothesized to affect the initiation, growth, and rupture of abdominal aortic aneurysms (AAAs), a vascular disease characterized by progressive wall degradation and enlargement of the abdominal aorta. This study aims to use magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) to quantify flow stagnation and recirculation in eight AAAs by computing particle residence time (PRT). Specifically, we used gadolinium-enhanced MR angiography to obtain images of the vessel lumens, which were used to generate subject-specific models. We also used phase-contrast MRI to measure blood flow at supraceliac and infrarenal locations to prescribe physiologic boundary conditions. CFD was used to simulate pulsatile flow, and PRT, particle residence index, and particle half-life of PRT in the aneurysms were computed. We observed significant regional differences of PRT in the aneurysms with localized patterns that differed depending on aneurysm geometry and infrarenal flow. A bulbous aneurysm with the lowest mean infrarenal flow demonstrated the slowest particle clearance. In addition, improvements in particle clearance were observed with increase of mean infrarenal flow. We postulate that augmentation of mean infrarenal flow during exercise may reduce chronic flow stasis that may influence mural thrombus burden, degradation of the vessel wall, and aneurysm growth.

Respiratory navigated free breathing 3D spoiled gradient-recalled echo sequence for contrast-enhanced examination of the liver: diagnostic utility and comparison with free breathing and breath-hold conventional examinations.

OBJECTIVE: The purpose of our study was to evaluate image quality in a 3D spoiled gradient-recalled echo (SPGR) sequence that was modified to incorporate respiratory navigation to limit the deleterious effects of respiratory motion and to compare it with conventional scanning during breath-holding and free breathing. CONCLUSION: Respiratory navigation of 3D SPGR sequences is technically feasible, and image quality is modestly improved over free breathing acquisitions using conventional 3D SPGR sequences. This may represent a promising imaging alternative for patients who cannot hold their breath.

Quantification of hemodynamics in abdominal aortic aneurysms during rest and exercise using magnetic resonance imaging and computational fluid dynamics.

Abdominal aortic aneurysms (AAAs) affect 5-7% of older Americans. We hypothesize that exercise may slow AAA growth by decreasing inflammatory burden, peripheral resistance, and adverse hemodynamic conditions such as low, oscillatory shear stress. In this study, we use magnetic resonance imaging and computational fluid dynamics to describe hemodynamics in eight AAAs during rest and exercise using patient-specific geometric models, flow waveforms, and pressures as well as appropriately resolved finite-element meshes. We report mean wall shear stress (MWSS) and oscillatory shear index (OSI) at four aortic locations (supraceliac, infrarenal, mid-aneurysm, and suprabifurcation) and turbulent kinetic energy over the entire computational domain on meshes containing more than an order of magnitude more elements than previously reported results (mean: 9.0-million elements; SD: 2.3 M; range: 5.7-12.0 M). MWSS was lowest in the aneurysm during rest 2.5 dyn/cm(2) (SD: 2.1; range: 0.9-6.5), and MWSS increased and OSI decreased at all four locations during exercise. Mild turbulence existed at rest, while moderate aneurysmal turbulence was present during exercise. During both rest and exercise, aortic turbulence was virtually zero superior to the AAA for seven out of eight patients. We postulate that the increased MWSS, decreased OSI, and moderate turbulence present during exercise may attenuate AAA growth.

Quantifying in vivo hemodynamic response to exercise in patients with intermittent claudication and abdominal aortic aneurysms using cine phase-contrast MRI.

PURPOSE: To evaluate rest and exercise hemodynamics in patients with abdominal aortic aneurysms (AAA) and peripheral occlusive disease (claudicants) using phase-contrast MRI. MATERIALS AND METHODS: Blood velocities were acquired by means of cardiac-gated cine phase-contrast in a 0.5 Tesla (T) open MRI. Volumetric flow was calculated at the supraceliac (SC), infrarenal (IR), and mid-aneurysm (MA) levels during rest and upright cycling exercise using an MR-compatible exercise cycle. RESULTS: Mean blood flow increased during exercise (AAA: 130%, Claudicants: 136% of resting heart rate) at the SC and IR levels for AAA participants (2.6 +/- 0.6 versus 5.8 +/- 1.6 L/min, P < 0.001 and 0.8 +/- 0.4 versus 5.1 +/- 1.7 L/min, P < 0.001) and claudicants (2.3 +/- 0.5 versus 4.5 +/- 0.9 L/min, P < 0.005 and 0.8 +/- 0.2 versus 3.3 +/- 0.9 L/min, P < 0.005). AAA participants had a significant decrease in renal and digestive blood flow from rest to exercise (1.8 +/- 0.7 to 0.7 +/- 0.6 L/min, P < 0.01). The decrease in renal and digestive blood flow during exercise correlated with daily activity level for claudicants (R = 0.81). CONCLUSION: Abdominal aortic hemodynamic changes due to lower extremity exercise can be quantified in patients with AAA and claudication using PC-MRI. The redistribution of blood flow during exercise was significant and different between the two disease states.