Christopher J François

University of Wisconsin–Madison, Madison, Wisconsin, United States

Are you Christopher J François?

Claim your profile

Publications (90)249.54 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Erratum to: Abdom Imaging (2013) 38:714–719 DOI 10.1007/s00261-012-9975-2In the original publication of the article, references were cited incorrectly which has been corrected with this erratum.In “Summary of Literature Review” under subheading “Pathophysiology”, the last sentence of the first paragraph states, “In the chronic setting, mesenteric ischemia is almost always caused by severe atherosclerotic disease, with rare causes including fibromuscular displasia, median arcuate ligament syndrome, and vasculitis [4].” The stated reference [4] is incorrect. The correct reference is Sreenarasimhaiah J (2005) Chronic mesenteric ischemia. Best Pract Res Clin Gastroenterol 19(2):283–295.In “Summary of Literature Review” under subheading “Pathophysiology”, the second sentence of the second paragraph states, “Acute mesenteric artery thrombosis is typically associated with chronic atherosclerotic disease and, given its more insidious course, a well-developed collateral circulation is commonly
    Abdominal Imaging 08/2014; 39(4). · 1.91 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Companion animals are routinely anesthetized or heavily sedated for cardiac MRI studies, however effects of varying anesthetic protocols on cardiac function measurements are incompletely understood. The purpose of this prospective study was to compare effects of two anesthetic protocols (Protocol A: Midazolam, fentanyl; Protocol B: Dexmedetomidine) on quantitative and qualitative blood flow values measured through the aortic, pulmonic, mitral, and tricuspid valves using two-dimensional phase contrast magnetic resonance imaging (2D PC MRI) in healthy dogs. Mean flow per heartbeat values through the pulmonary artery (Qp) and aorta (Qs) were compared to right and left ventricular stroke volumes (RVSV, LVSV) measured using a reference standard of 2D Cine balanced steady-state free precession MRI. Pulmonary to systemic flow ratio (Qp/Qs) was also calculated. Differences in flow and Qp/Qs values generated using 2D PC MRI did not differ between the two anesthetic protocols (P = 1). Mean differences between Qp and RVSV were 3.82 ml/beat (95% limits of agreement: 3.62, −11.26) and 1.9 ml/beat (−7.86, 11.66) for anesthesia protocols A and B, respectively. Mean differences between Qs and LVSV were 1.65 ml/beat (−5.04, 8.34) and 0.03 ml/beat (−4.65, 4.72) for anesthesia protocols A and B, respectively. Mild tricuspid or mitral reflux was seen in 2/10 dogs using 2D PC MRI. No aortic or pulmonic insufficiency was observed. Findings from the current study indicated that these two anesthetic protocols yield similar functional measures of cardiac blood flow using 2D PC MRI in healthy dogs. Future studies in clinically affected patients are needed.
    Veterinary Radiology &amp Ultrasound 08/2014; · 1.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A low relative area change (RAC) of the proximal pulmonary artery (PA) over the cardiac cycle is a good predictor of mortality from right ventricular failure in patients with pulmonary hypertension (PH). The relationship between RAC and local mechanical properties of arteries, which are known to stiffen in acute and chronic PH, is not clear, however. In this study, we estimated elastic moduli of three PAs (MPA, LPA and RPA: main, left and right PAs) at the physiological state using mechanical testing data and correlated these estimated elastic moduli to RAC measured in vivo with both phase-contrast magnetic resonance imaging (PC-MRI) and M-mode echocardiography (on RPA only). We did so using data from a canine model of acute PH due to embolization to assess the sensitivity of RAC to changes in elastic modulus in the absence of chronic PH-induced arterial remodeling. We found that elastic modulus increased with embolization-induced PH, presumably a consequence of increased collagen engagement, which corresponds well to decreased RAC. Furthermore, RAC was inversely related to elastic modulus. Finally, we found MRI and echocardiography yielded comparable estimates of RAC. We conclude that RAC of proximal PAs can be obtained from either MRI or echocardiography and a change in RAC indicates a change in elastic modulus of proximal PAs detectable even in the absence of chronic PH-induced arterial remodeling. The correlation between RAC and elastic modulus of proximal PAs may be useful for prognoses and to monitor the effects of therapeutic interventions in patients with PH.
    Journal of biomechanics. 07/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Heart rate is a major factor influencing diagnostic image quality in computed tomographic coronary artery angiography (MDCT-CA), with an ideal heart rate of 60–65 beats/min in humans. The purpose of this prospective study was to compare effects of two different clinically applicable anesthetic protocols on cardiovascular parameters and 64-MDCT-CA quality in 10 healthy dogs. Scan protocols and bolus volumes were standardized. Image evaluations were performed in random order by a board-certified veterinary radiologist who was unaware of anesthetic protocols used. Heart rate during image acquisition did not differ between protocols (P = 1), with 80.6 ± 7.5 bpm for protocol A and 79.2 ± 14.2 bpm for protocol B. Mean blood pressure was significantly higher (P > 0.05) using protocol B (protocol A 62.9 ± 9.1 vs. protocol B 72.4 ± 15.9 mmHg). The R-R intervals allowing for best depiction of individual coronary artery segments were found in the end diastolic period and varied between the 70% and 95% interval. Diagnostic quality was rated excellent, good, and moderate in the majority of the segments evaluated, with higher scores given for more proximal segments and lower for more distal segments, respectively. Blur was the most commonly observed artifact and mainly affected the distal segments. No significant differences were identified between the two protocols for optimal reconstruction interval, diagnostic quality and measured length individual segments, or proximal diameter of the coronary arteries (P = 1). Findings indicated that, when used with a standardized bolus volume, both of these anesthetic protocols yielded diagnostic quality coronary 64-MDCT-CA exams in healthy dogs.
    Veterinary Radiology &amp Ultrasound 07/2014; · 1.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PurposeTo compare pulmonary artery flow using Cartesian and radially sampled four-dimensional flow-sensitive (4D flow) MRI at two institutions.Methods Nineteen healthy subjects and 17 pulmonary arterial hypertension (PAH) subjects underwent a Cartesian 4D flow acquisition (institution 1) or a three-dimensional radial acquisition (institution 2). The diameter, peak systolic velocity (Vmax), peak flow (Qmax), stroke volume (SV), and wall shear stress (WSS) were computed in two-dimensional analysis planes at the main, right, and left pulmonary artery. Interobserver variability, interinstitutional differences, flow continuity, and the hemodynamic measurements in healthy and PAH subjects were assessed.ResultsVmax, Qmax, SV, and WSS at all locations were significantly lower (P < 0.05) in PAH compared with healthy subjects. The limits of agreement were 0.16 m/s, 2.4 L/min, 10 mL, and 0.31 N/m2 for Vmax, Qmax, SV, and WSS, respectively. Differences between Qmax and SV using Cartesian and radial sequences were not significant. Plane placement and acquisition exhibited isolated, site-based differences between Vmax and WSS.Conclusions4D flow MRI was used to detect differences in pulmonary artery hemodynamics for PAH subjects. Flow and WSS in healthy and PAH subject cohorts were similar between Cartesian- and radial-based 4D flow MRI acquisitions with minimal interobserver variability. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 06/2014; · 3.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Truncation artefact (Gibbs ringing) causes central signal drop within vessels in pulmonary magnetic resonance angiography (MRA) that can be mistaken for emboli, reducing diagnostic accuracy for pulmonary embolism (PE). We propose a quantitative approach to differentiate truncation artefact from PE.
    European Radiology 05/2014; · 4.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to quantify right (RV) and left (LV) ventricular function, pulmonary artery flow (QP), tricuspid valve regurgitation velocity (TRV), and aorta flow (QS) from a single 4D flow cardiovascular magnetic resonance (CMR) (time-resolved three-directionally motion encoded CMR) sequence in a canine model of acute thromboembolic pulmonary hypertension (PH). Acute PH was induced in six female beagles by microbead injection into the right atrium. Pulmonary arterial (PAP) and pulmonary capillary wedge (PCWP) pressures and cardiac output (CO) were measured by right heart catheterization (RHC) at baseline and following induction of acute PH. Pulmonary vascular resistance (PVRRHC) was calculated from RHC values of PAP, PCWP and CO (PVRRHC = (PAP-PCWP)/CO). Cardiac magnetic resonance (CMR) was performed on a 3 T scanner at baseline and following induction of acute PH. RV and LV end-diastolic (EDV) and end-systolic (ESV) volumes were determined from both CINE balanced steady-state free precession (bSSFP) and 4D flow CMR magnitude images. QP, TRV, and QS were determined from manually placed cutplanes in the 4D flow CMR flow-sensitive images in the main (MPA), right (RPA), and left (LPA) pulmonary arteries, the tricuspid valve (TRV), and aorta respectively. MPA, RPA, and LPA flow was also measured using two-dimensional flow-sensitive (2D flow) CMR. Biases between 4D flow CMR and bSSFP were 0.8 mL and 1.6 mL for RV EDV and RV ESV, respectively, and 0.8 mL and 4 mL for LV EDV and LV ESV, respectively. Flow in the MPA, RPA, and LPA did not change after induction of acute PAH (p = 0.42-0.81). MPA, RPA, and LPA flow determined with 4D flow CMR was significantly lower than with 2D flow (p < 0.05). The correlation between QP/TRV and PVRRHC was 0.95. The average QP/QS was 0.96 +/- 0.11. Using both magnitude and flow-sensitive data from a single 4D flow CMR acquisition permits simultaneous quantification of cardiac function and cardiopulmonary hemodynamic parameters important in the assessment of PH.
    Journal of Cardiovascular Magnetic Resonance 03/2014; 16(1):23. · 4.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pulmonary hypertension is a condition of varied etiology, commonly associated with poor clinical outcome. Patients are categorized on the basis of pathophysiological, clinical, radiologic, and therapeutic similarities. Pulmonary arterial hypertension (PAH) is often diagnosed late in its disease course, with outcome dependent on etiology, disease severity, and response to treatment. Recent advances in quantitative magnetic resonance imaging (MRI) allow for better initial characterization and measurement of the morphologic and flow-related changes that accompany the response of the heart-lung axis to prolonged elevation of pulmonary arterial pressure and resistance and provide a reproducible, comprehensive, and noninvasive means of assessing the course of the disease and response to treatment. Typical features of PAH occur primarily as a result of increased pulmonary vascular resistance and the resultant increased right ventricular (RV) afterload. Several MRI-derived diagnostic markers have emerged, such as ventricular mass index, interventricular septal configuration, and average pulmonary artery velocity, with diagnostic accuracy similar to that of Doppler echocardiography. Furthermore, prognostic markers have been identified with independent predictive value for identification of treatment failure. Such markers include large RV end-diastolic volume index, low left ventricular end-diastolic volume index, low RV ejection fraction, and relative area change of the pulmonary trunk. MRI is ideally suited for longitudinal follow-up of patients with PAH because of its noninvasive nature and high reproducibility and is advantageous over other biomarkers in the study of PAH because of its sensitivity to change in morphologic, functional, and flow-related parameters. Further study on the role of MRI image based biomarkers in the clinical environment is warranted.
    Journal of thoracic imaging 03/2014; 29(2):68-79. · 1.42 Impact Factor
  • Randi Drees, Christopher J François, Jimmy H Saunders
    [Show abstract] [Hide abstract]
    ABSTRACT: Computed tomographic angiography (CTA) of the thoracic cardiovascular system is offering new diagnostic opportunities in companion animal patients with the increasing availability of multidetector-row computed tomographic (MDCT) units in veterinary facilities. Optimal investigation of the systemic, pulmonary, and coronary circulation provides unique challenges due to the constant movement of the heart, the small size of several of the structures of interest, and the dependence of angiographic quality on various contrast bolus design and patient factors. Technical and practical aspects of thoracic cardiovascular CTA are reviewed in light of the currently available veterinary literature and future opportunities given utilizing MDCT in companion animal patients with suspected thoracic cardiovascular disease.
    Veterinary Radiology &amp Ultrasound 02/2014; · 1.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To develop and demonstrate a breathheld 3D radial ultrashort echo time (UTE) acquisition to visualize co-registered lung perfusion and vascular structure. Nine healthy dogs were scanned twice at 3 Tesla (T). Contrast-enhanced pulmonary perfusion scans were acquired with a temporally interleaved three-dimensional (3D) radial UTE (TE = 0.08 ms) sequence in a breathhold (1 s time frames over a 33 s breathhold). The 3D breathheld volume was reconstructed into time-resolved perfusion datasets, and a composite vascular structure dataset. For structural comparison, a 5 min respiratory-gated 3D radial UTE scan was acquired. Data were analyzed by quantitative metrics and radiologist scoring. Appropriate time-course of contrast was seen in all subjects. Right ventricle to aorta transit times were 7.4 ± 2.0 s. Relative lung enhancement was a factor of 8.4 ± 1.5. Radiologist scoring showed similarly excellent visualization of the pulmonary arteries to the subsegmental level in breathheld (94% of cases) and respiratory-gated (100% of cases) acquisitions (P = 0.33) despite the aggressive under sampling in the breathheld scan. Similarly, differentiation of lung tissue and airways was achieved by both acquisition methods. A time-resolved 3D radial UTE sequence for simultaneous imaging of pulmonary perfusion and co-registered vascular structure is feasible.J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 12/2013; · 2.57 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE To evaluate peak velocity, net flow, vessel diameter and wall shear stress (WSS) in the proximal pulmonary arteries of normotensive controls and patients with pulmonary arterial hypertension (PAH) using 4D flow MRI. METHOD AND MATERIALS With IRB approval, 10 patients (age: 57±10, 5 females) and 9 volunteers (age: 40 ±12, 6 females) were scanned on a 3T MR system. Time-resolved 3D pulmonary flow was measured using 4DMRI with full coverage of the right ventricular outflow tract, pulmonary trunk (PT) and right and left pulmonary branches (RPA and LPA). Net flow and maximum velocity were quantified at the level of PT, RPA and LPA. WSS and vessel diameter were also measured in analysis planes positioned at these three levels in both groups. RESULTS Net flow in PAH patients (PT: 52.7±11, LPA: 21.5±5, RPA: 26.2±7 ml/cycle) was significantly lower compared to controls (PT: 68.3±13, LPA: 29.3±7, RPA: 32.7±5 ml/cycle, p-value< 0.05). The same pattern was observed for peak velocity in PAH patients (PT: 0.5±0.1, LPA: 0.3±0.1, RPA: 0.4±0.1 m/s) compared to the controls (PT: 0.8±0.1, LPA: 0.7±0.2, RPA: 0.9±0.2 m/s, p-value< 0.05). In addition, PAH arteries had a significantly larger diameter (PT: 3.4±0.5, LPA: 2.3±0.3, RPA: 2.4±0.3 cm) compared to the normal population (PT: 2.6±0.2, LPA: 1.8±0.2, RPA: 1.7±0.3 cm, p-value< 0.001). As shown in Figure 1, PAH patients had reduced WSS at all three measurement positions, compared to volunteers. CONCLUSION 4D flow MRI illustrates distinct hemodynamic changes in PAH patients compared to a normal population. The significant reduction in net flow, peak velocity and an increase in PA lumen diameter in patients resulted in decreased WSS values, as compared to normal volunteers. CLINICAL RELEVANCE/APPLICATION Pulmonary hypertension is associated with right heart failure, but its effect on arterial diameter and hemodynamic factors (i.e. velocity, flow, WSS) and their role in disease progression is not clear
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE Determine the effectiveness of using pulmonary magnetic resonance imaging as the primary test for the determination of pulmonary embolism (MRA-PE) in a symptomatic population. METHOD AND MATERIALS We performed a retrospective review of our experience with 578 consecutive symptomatic patients studied over a five year period with MRA-PE for the primary diagnosis of pulmonary embolism (PE). Contrast enhanced MRA images were performed in a single breath hold at 1.5 Tesla. The negative predictive value at three months and Kaplan-Meier analysis were calculated from the available time to venous thromboembolism (VTE) follow up data obtained from the electronic medical record. RESULTS There were 578 consecutive symptomatic patients who underwent pulmonary MRA as their primary examination for the determination of PE. There were 467 females (average age ± 1S.D: 36.6 years, ± 16), and 111 males (average age ± 1S.D: 44.9 years± 19.5). Out of 578 MRA exams, 25 were non-diagnostic due to motion. Of the remaining 553 patients, 53 were positive and treated on the basis of MRA findings alone. Of the 500 negative MRA’s, 76 were lost to 3-month follow up, leaving 424 patients with an initial negative MRA and 3 months of complete EMR follow up. Of these, 8 were found to have VTE during F/U. The negative predictive value for MRA-PE at three months was 98% (97-99, 95% CI). Kaplan-Meier estimate values, for time to VTE at one year, was found to be 0.98 (97-0.99, 95% C.I). CONCLUSION In this single site retrospective study, MRA-PE was found to be effective as a primary imaging modality for the diagnosis of PE in symptomatic patients with a high rate of technical success. At those sites with sufficient technical expertise in performing pulmonary MRA, and knowledgeable of the artifacts associated with this technique, should consider use of this modality where appropriate clinical settings warrant. CLINICAL RELEVANCE/APPLICATION MRA-PE can be safely used for the primary diagnosis of pulmonary embolism in symptomatic patients. This test should be considered as an acceptable alternative to CTA-PE for vulnerable patients.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: To demonstrate the use of temporal averaging with radial 4D flow magnetic resonance imaging (MRI) to reduce scan time for quantification and visualization of flow in the portal circulation. This study compared phase-contrast MR angiography, 3D flow visualization, and flow quantification of portal venous hemodynamics of time-averaged vs. time-resolved reconstructions. Time-resolved 3D radial ("4D") phase contrast data were acquired from 44 subjects (15 volunteers, 29 cirrhosis patients) at 3T. Images were reconstructed as a fully sampled time-resolved reconstruction and multiple time-averaged reconstructions using a variable number of acquired projections to simulate different scan times. Images from each reconstruction were evaluated to compare the quality of anatomical and hemodynamic visualization. Time-averaged reconstructions outperformed time-resolved reconstructions for flow quantification (3.9 ± 3.1% error vs. 5.2 ± 4.4% error), average streamline length (47 ± 7 mm vs. 34 ± 15 mm), and visualization quality (average grading = 3.7 ± 0.5 vs. 2.2 ± 0.9). In addition, excellent visualization quality was achieved using fewer acquired projections. Reductions in scan time can be achieved through time-averaging while still providing excellent visualization and quantification in the portal circulation. Scan time reduction of up to 70%-80% was possible for high-quality assessment, translating into a reduction in scan time from 10-12 minutes to ∼3-4 minutes. J. Magn. Reson. Imaging 2013;. © 2013 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 11/2013; · 2.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To develop and evaluate a free-breathing chemical-shift-encoded (CSE) spoiled gradient-recalled echo (SPGR) technique for whole-heart water-fat imaging at 3 Tesla (T). We developed a three-dimensional (3D) multi-echo SPGR pulse sequence with electrocardiographic gating and navigator echoes and evaluated its performance at 3T in healthy volunteers (N = 6) and patients (N = 20). CSE-SPGR, 3D SPGR, and 3D balanced-SSFP with chemical fat saturation were compared in six healthy subjects with images evaluated for overall image quality, level of residual artifacts, and quality of fat suppression. A similar scoring system was used for the patient datasets. Images of diagnostic quality were acquired in all but one subject. CSE-SPGR performed similarly to SPGR with fat saturation, although it provided a more uniform fat suppression over the whole field of view. Balanced-SSFP performed worse than SPGR-based methods. In patients, CSE-SPGR produced excellent fat suppression near metal. Overall image quality was either good (7/20) or excellent (12/20) in all but one patient. There were significant artifacts in 5/20 clinical cases. CSE-SPGR is a promising technique for whole-heart water-fat imaging during free-breathing. The robust fat suppression in the water-only image could improve assessment of complex morphology at 3T and in the presence of off-resonance, with additional information contained in the fat-only image. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.
    Magnetic Resonance in Medicine 11/2013; · 3.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Although aortic valve replacement is the definitive therapy for severe aortic stenosis, almost half of patients with severe aortic stenosis are unable to undergo conventional aortic valve replacement because of advanced age, comorbidities, or prohibitive surgical risk. Treatment options have been recently expanded with the introduction of catheter-based implantation of a bioprosthetic aortic valve, referred to as transcatheter aortic valve replacement. Because this procedure is characterized by lack of exposure of the operative field, image guidance plays a critical role in preprocedural planning. This guideline document evaluates several preintervention imaging examinations that focus on both imaging at the aortic valve plane and planning in the supravalvular aorta and iliofemoral system. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.
    Journal of the American College of Radiology: JACR 10/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Renal transplant patients often require imaging to ensure appropriate graft placement, to assess integrity of transplant vessel anastomosis and to evaluate for stenosis that can be a cause of graft failure. Because there is risk for nephrogenic systemic fibrosis in the setting of renal insufficiency, the use of non-contrast MRA in these patients is helpful. In this study, the ability of two non-contrast MRA methods - 3D radial linear combination balanced SSFP (VIPR-SSFP) and inflow-weighted Cartesian SSFP (IFIR) - to visualize the transplant renal vessels is compared. Twenty-one renal transplant patients were scanned using the VIPR-SSFP and IFIR sequences. Diagnostic efficacy of the sequences was scored using a four point Likert scale according to the following criteria: overall image quality, fat suppression, and arterial/venous visualization quality. Average scores for each criterion were compared using the Wilcoxon signed-rank test. In addition to significantly improved venous visualization, the VIPR-SSFP sequence provided significantly improved fat suppression quality (p<0.03) compared to IFIR. VIPR-SSFP also identified several pathologies such as renal arterial pseudoaneurysm that were not visible on the IFIR images. However, IFIR afforded superior quality of arterial visualization (p<0.005). These two methods of non-contrast MR imaging each have significant strengths and are complementary to each other in evaluating the vasculature of renal allografts.
    Magnetic Resonance Imaging 10/2013; · 2.06 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To investigate the utility of hyperpolarized He-3 MRI for detecting regional lung ventilated volume (VV ) changes in response to exercise challenge and leukotriene inhibitor montelukast, human subjects with exercise induced bronchoconstriction (EIB) were recruited. This condition is described by airway constriction following exercise leading to reduced forced expiratory volume in 1 second (FEV1) coinciding with ventilation defects on hyperpolarized He-3 MRI. Thirteen EIB subjects underwent spirometry and He-3 MRI at baseline, postexercise, and postrecovery at multiple visits. On one visit montelukast was given and on two visits placebo was given. Regional VV was calculated in the apical/basilar dimension, in the anterior/posterior dimension, and for the entire lung volume. The whole lung VV was used as an end-point and compared with spirometry. Postchallenge FEV1 dropped with placebo but not with treatment, while postchallenge VV dropped more with placebo than treatment. Sources of variability for VV included region (anterior/posterior), scan, and treatment. VV correlated with FEV1/ forced vital capacity (FVC) and forced expiratory flow between 25 and 75% of FVC and showed gravitational dependence after exercise challenge. A paradigm testing the response of ventilation to montelukast revealed both a whole-lung and regional response to exercise challenge and therapy in EIB subjects. J. Magn. Reson. Imaging 2013. © 2013 Wiley Periodicals, Inc.
    Journal of Magnetic Resonance Imaging 09/2013; · 2.57 Impact Factor
  • Christopher J François
    [Show abstract] [Hide abstract]
    ABSTRACT: The diagnostic workup of patients with cardiovascular disease is frequently challenging, and requires a multimodality approach to appropriately determine management. Depending on the presenting symptoms and their acuity, noninvasive diagnostic imaging strategies can include radiography, ultrasonography, computed tomography, and magnetic resonance imaging. This article provides an introduction to the use of these imaging modalities for commonly encountered diseases of the aorta, mesenteric arteries, and renal arteries, focusing on how the acuity of presentation and likelihood of disease affects the workup of patients with known or suspected vascular disease.
    Surgical Clinics of North America 08/2013; 93(4):741-60. · 2.02 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this study was to validate radially undersampled 5-point velocity-encoded time-resolved flow-sensitive magnetic resonance imaging (MRI) ("PC-VIPR", phase contrast vastly undersampled imaging with isotropic resolution projection reconstruction magnetic resonance) for the quantification of ascending aortic (AAO) and main pulmonary artery (MPA) flow in vivo. Data from 18 healthy volunteers (41.6 ± 16.2 years [range, 22-73 years]; body mass index, 26.0 ± 3.5 [19.1-31.4]) scanned at 3 T with a 32-channel coil were included. The left and right ventricular stroke volumes calculated from contiguous short-axis CINE-balanced steady state free precession (CINE-bSSFP) slices were used as the primary reference for cardiac output. Flow measured from 2-dimensional phase contrast MRI (2D-PC-MRI) in the AAO and the MPA served as the secondary reference. Time-resolved 4-dimensional flow-sensitive MRI (4D flow MRI) using PC-VIPR was performed with a velocity sensitivity of Venc = 150 cm/s reconstructed to 20 time frames at 1.4-mm isotropic spatial resolution. In 11 of 20 volunteers, phantom-corrected 4D flow MRI data were also assessed. Differences between methods of calculating the left ventricular and right ventricular cardiac output were assessed with the Bland-Altman analysis (BA, mean difference ±2SD). The QP/QS-ratio was calculated for each method. Initially, PC-VIPR compared unfavorably with CINE-bSSFP (left ventricular stroke volume: 96.5 ± 14.4 mL; right ventricular stroke volume: 93.6 ± 14.0 mL vs 81.2 ± 24.3 mL [AAO] and 85.6 ± 25.4 mL [MPA]; P = 0.027 and 0.25) with BA differences of -14.6 ± 44.0 mL (AAO) and -9.0 ± 45.9 mL (MPA). Whereas phantom correction had minor effects on 2D-PC-MRI results and comparison with CINE-bSSFP, it improved PC-VIPR results: BA differences between CINE-bSSFP and PC-VIPR after correction were -1.4 ± 15.3 mL (AAO) and -4.1 ± 16.1 mL (MPA); BA comparison with 2D-PC-MRI improved to -12.0 ± 48.1 mL (AAO) and -2.2 ± 19.5 mL (MPA). QP/QS-ratio results for all techniques were within physiologic limits. Accurate quantification of AAO and MPA flows with radially undersampled 4D flow MRI applying 5-point velocity encoding is achievable when phantom correction is used.
    Investigative radiology 07/2013; · 4.85 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The current Dana Point Classification system (2009) distinguishes elevation of pulmonary arterial pressure into pulmonary arterial hypertension (PAH) and pulmonary hypertension. Fortunately, PAH is not a common disease. However, with the aging of the First World's population, heart failure has become an important outcome of pulmonary hypertension, with up to 9% of the population involved. PAH is usually asymptomatic until late in the disease process. Although features that are indirectly related to PAH are found on noninvasive imaging studies, its diagnosis and management still require right heart catheterization. Imaging features of PAH include the following: (1) enlargement of the pulmonary trunk and main pulmonary arteries; (2) decreased pulmonary arterial compliance; (3) tapering of the peripheral pulmonary arteries; (4) enlargement of the inferior vena cava; and (5) increased mean transit time. The chronic requirement to generate high pulmonary arterial pressure measurably affects the right heart and main pulmonary artery. This change in physiology causes the following structural and functional alterations that have been shown to have prognostic significance: relative area change (RAC) of the pulmonary trunk, right ventricular stroke volume index, right ventricular stroke volume, right ventricular end-diastolic volume index, left ventricular end-diastolic volume index, and baseline right ventricular ejection fraction <35%. All of these variables can be quantified noninvasively and followed up longitudinally in each patient using magnetic resonance imaging to modify the treatment regimen. Untreated PAH frequently results in rapid clinical decline and death within 3 years of diagnosis. Unfortunately, even with treatment, fewer than half of these patients are alive at 4 years.
    Journal of thoracic imaging 05/2013; 28(3):178-195. · 1.42 Impact Factor

Publication Stats

526 Citations
249.54 Total Impact Points

Institutions

  • 2008–2014
    • University of Wisconsin–Madison
      • • Department of Medical Physics
      • • Department of Radiology
      Madison, Wisconsin, United States
  • 2013
    • Yale-New Haven Hospital
      New Haven, Connecticut, United States
  • 2012
    • Brigham and Women's Hospital
      • Center for Brain Mind Medicine
      Boston, MA, United States
  • 2003–2009
    • Northwestern University
      • • Department of Radiology
      • • Division of Cardiology (Dept. of Medicine)
      Evanston, IL, United States
  • 2007
    • Northwestern Memorial Hospital
      • Department of Radiology
      Chicago, Illinois, United States