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D A Bluemke

Publications and source records attributed to D A Bluemke.

At least 19 recordsLinked to original sources
PubMed2005

Non-invasive half millimetre 32 detector row computed tomography angiography accurately excludes significant stenoses in patients with advanced coronary artery disease and high calcium scores.

OBJECTIVE: To show an overall diagnostic accuracy > or = 90% for detection of > or = 50% stenoses by coronary half millimetre 32 detector row computed tomography angiography (32 x 0.5-MDCTA) in patients with advanced coronary artery disease (CAD) and a high likelihood of raised calcium scores. METHODS: ECG gated 32 x 0.5-MDCTA (32 x 0.5 mm cross sections, 0.35 x 0.35 x 0.35 mm3 isotropic voxels, 400 ms rotation) was performed after injection of iodixanol (120 ml, 320 mg/ml) in 30 consecutive patients (25 men, mean (SD) age 59 (13) years, body mass index 26.2 (4.9) kg/m2). Native arteries, including > or = 1.5 mm branches, and bypass grafts were screened for > or = 50% stenoses. Stents were excluded. Conventional coronary angiography (performed 18 (12) days before 32 x 0.5-MDCTA) was analysed by quantitative coronary angiography. RESULTS: Median Agatston calcium score was 510 (range 3-5066). Sensitivity, specificity, and positive and negative predictive values for detection of > or = 50% stenoses in native arteries were 76% (29 of 38), 94% (190 of 202), 71% (29 of 41), and 96% (190 of 199), respectively. Overall diagnostic accuracy was 91% (219 of 240). Due to the following artefacts 20% (69 of 352) of the vessels were excluded: motion, noise, and low contrast enhancement isolated or in combination (45 of 69 (65%)); image distortion by implantable cardioverter-defibrillator or pacemaker leads (18 of 69 (26%)); and blooming secondary to severe calcification (6 of 69 (9%)). CONCLUSIONS: Coronary 32 x 0.5-MDCTA accurately excludes > or = 50% stenoses in patients with advanced CAD and high calcium scores with an overall diagnostic accuracy of 91%.

Adult↗
PubMed2005

Cardiac magnetic resonance imaging in a patient with implantable cardioverter-defibrillator.

The presence of pacemakers and implantable cardioverter-defibrillators (ICD) is considered historically a contraindication to magnetic resonance (MR) imaging. This image modality has unparalleled soft-tissue imaging capabilities, and many consider it as the image of choice for patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C). ICDs are now smaller, with less magnetic materials and improved electromagnetic interference protection. We tested modern ICDs for heat, force, function and image distortion and found that several of them may indeed be MRI safe. We report here a patient who was suspected of ARVD/C, underwent ICD implantation based on MR safety testing, and underwent intentionally scheduled follow-up cardiac MR imaging. This is the description of a patient with an ICD who had planned MRI scanning. The scan was safe and most of the MRI images were of high quality.

Adult↗
PubMed2004

Myocardial first-pass perfusion magnetic resonance imaging: a multicenter dose-ranging study.

BACKGROUND: MRI can identify patients with obstructive coronary artery disease by imaging the left ventricular myocardium during a first-pass contrast bolus in the presence and absence of pharmacologically induced myocardial hyperemia. The purpose of this multicenter dose-ranging study was to determine the minimally efficacious dose of gadopentetate dimeglumine injection (Magnevist Injection; Berlex Laboratories) for detecting obstructive coronary artery disease. METHOD AND RESULTS: A total of 99 patients scheduled for coronary artery catheterization as part of their clinical evaluation were enrolled in this study. Patients were randomized to 1 of 3 doses of gadopentate dimeglumine: 0.05, 0.10, or 0.15 mmol/kg. First-pass perfusion imaging was performed during hyperemia (induced by a 4-minute infusion of adenosine at a rate of 140 microg x kg(-1) x min(-1)) and then again in the absence of adenosine with otherwise identical imaging parameters and the same contrast dose. Perfusion defects were evaluated subjectively by 4 blinded reviewers. Receiver-operating curve analysis showed that the areas under the receiver-operating curve were 0.90, 0.72, and 0.83 for the low-, medium-, and high-contrast doses, respectively, compared with quantitative coronary angiography (diameter stenosis > or =70%). For the low-dose group, mean sensitivity was 93+/-0%, mean specificity was 75+/-7%, and mean accuracy was 85+/-3%. CONCLUSIONS: First-pass perfusion MRI is a safe and accurate test for identifying patients with obstructive coronary artery disease. A low dose of 0.05 mmol/kg gadopentetate dimeglumine is at least as efficacious as higher doses.

Adenosine↗
PubMed2001

Relation between Gd-DTPA contrast enhancement and regional inotropic response in the periphery and center of myocardial infarction.

BACKGROUND: Gd-DTPA contrast-enhanced (CE) MRI identifies patterns of early hypoenhancement and delayed hyperenhancement in acute myocardial infarction, but their clinical significance for the prediction of myocardial viability remains controversial. Therefore, we closely examined the relationship between these CE patterns and regional inotropic response to low-dose dobutamine infusion at a regional level. METHODS AND RESULTS: Thirteen dogs underwent CE and tagged MRI at rest and during 5 microg. kg(-1). min(-1) dobutamine 48 hours after MI. CE patterns and 3D regional strains were measured in 96 segments per animal. Segments were categorized as being normofunctional (n=828) if resting circumferential shortening was within the range of remote myocardium, or dysfunctional (n=420) if not. Inotropic response in resting dysfunctional segments was assessed according to CE patterns. Significant improvement of radial thickening (from +12+/-1% [mean+/-SEM] to +22+/-2%, P<0.05) and circumferential shortening (from +1+/-1% to -5+/-1%, P<0.05) strains occurred in dysfunctional myocardium with normal CE pattern but not in myocardium with early hypoenhancement. Delayed hyperenhanced myocardium displayed a more complex behavior. Circumferential stretching improved in the peripheral regions (from +4+/-1% to -2+/-2%, P<0.05), where the infarct was nontransmural (38+/-3% transmurality), but not in centrally hyperenhanced regions (from +4+/-1% to +1+/-1% P=NS), where the infarct was 66+/-3% transmural. CONCLUSIONS: Inotropic reserve was confined to dysfunctional myocardium with normal contrast enhancement but not to myocardium with early hypoenhancement. Inotropic response in delayed hyperenhanced myocardium is influenced by transmurality of necrosis. These observations support the use of CE MRI for the clinical detection of myocardial viability.

Animals↗
PubMed2001

Dynamic pelvic magnetic resonance imaging and cystocolpoproctography alter surgical management of pelvic floor disorders.

PURPOSE: Pelvic organ prolapse results in a spectrum of progressively disabling disorders. Despite attempts to standardize the clinical examination, a variety of imaging techniques are used. The purpose of this study was to evaluate dynamic pelvic magnetic resonance imaging and dynamic cystocolpoproctography in the surgical management of females with complex pelvic floor disorders. METHODS: Twenty-two patients were identified from The Johns Hopkins Pelvic Floor Disorders Center database who had symptoms of complex pelvic organ prolapse and underwent dynamic magnetic resonance, dynamic cystocolpoproctography, and subsequent multidisciplinary review and operative repair. RESULTS: The mean age of the study group was 58 +/- 13 years, and all patients were Caucasian. Constipation (95.5 percent), urinary incontinence (77.3 percent), complaints of incomplete fecal evacuation (59.1 percent), and bulging vaginal tissues (54.4 percent) were the most common complaints on presentation. All patients had multiple complaints with a median number of 4 symptoms (range, 2-8). Physical examination, dynamic magnetic resonance imaging, and dynamic cystocolpoproctography were concordant for rectocele, enterocele, cystocele, and perineal descent in only 41 percent of patients. Dynamic imaging lead to changes in the initial operative plan in 41 percent of patients. Dynamic magnetic resonance was the only modality that identified levator ani hernias. Dynamic cystocolpoproctography identified sigmoidoceles and internal rectal prolapse more often than physical examination or dynamic magnetic resonance. CONCLUSIONS: Levator ani hernias are often missed by physical examination and traditional fluoroscopic imaging. Dynamic magnetic resonance and cystocolpoproctography are complementary studies to the physical examination that may alter the surgical management of females with complex pelvic floor disorders.

Adult↗
PubMed2001

The relationship between vascular wall shear stress and flow-mediated dilation: endothelial function assessed by phase-contrast magnetic resonance angiography.

OBJECTIVES: We sought: 1) to investigate the relationship between vascular wall shear stress and flow-mediated dilation (FMD) in humans, and 2) to investigate whether this relationship could explain why FMD is greater in small arteries. BACKGROUND: Arterial wall shear stress (WSS) is considered to be the primary stimulus for the endothelial-dependent FMD response. However, the relationship between WSS and FMD has not been investigated in humans. Furthermore, FMD is greater in small arteries, though the reasons for this phenomenon are unclear. METHODS: Using phase-contrast magnetic resonance angiography (PMRCA), we measured hyperemic WSS and FMD in 18 healthy volunteers. Peak systolic WSS was calculated assuming a blunted parabolic velocity profile. Diameter by PCMRA and by ultrasound was compared in nine subjects. RESULTS: Flow-mediated dilation was linearly proportional to hyperemic peak systolic WSS (r = 0.79, p = 0.0001). Flow-mediated dilation was inversely related to baseline diameter (r = 0.62, p = 0.006), but the hyperemic peak WSS stimulus was also inversely related to baseline diameter (r = 0.47, p = 0.049). Phase-contrast magnetic resonance angiography and ultrasound diameters were compared in nine subjects and correlated well (r = 0.84, p < 0.0001), but diameter by PCMRA was greater (4.1 +/- 0.7 mm vs. 3.7 +/- 0.5 mm, p = 0.009). CONCLUSION: Arterial FMD is linearly proportional to peak hyperemic WSS in normal subjects. Thus, the endothelial response is linearly proportional to the stimulus. Furthermore, the greater FMD response in small arteries is accounted for, at least partially, by a greater hyperemic WSS stimulus in small arteries. By allowing the calculation of vascular WSS, which is the stimulus for FMD, and by imaging a fixed arterial cross-section, thus reducing operator dependence, PCMRA enhances the assessment of vascular endothelial function.

Adult↗
PubMed2001

A comparison of prospective and retrospective respiratory navigator gating in 3D MR coronary angiography.

A comparison between the prospective and retrospective respiratory navigator gating in MR coronary angiography was performed with eight normal subjects. A three-dimensional (3D) ECG-gated fast gradient echo pulse sequence was used for image data acquisition. The results show that the MR coronary angiography obtained using retrospective gating retains a considerable amount of motion artifacts. In this study, the images acquired using prospective navigator gating demonstrated significantly reduced motion artifacts (p = 0.009), improved vessel visibility (p = 0.021) with reduced imaging time (p = 0.013) compared to the images obtained using retrospective navigator gating.

Adult↗
PubMed2001

Magnetic resonance imaging of large vessel vasculitis.

Conventional x-ray angiography has traditionally played a prominent role in the radiologic evaluation of large vessel vasculitis. Recently, noninvasive magnetic resonance (MR) methods have received much attention for their potential to complement and possibly supplant conventional angiography. In particular, promising advances have been made in the areas of MR angiography and physiologic imaging. MR provides high resolution anatomic information, including lumen configuration and vascular wall thickness, and physiologic data, such as measurements of the degree of wall enhancement and the presence of edema. Moreover, imaging data are obtained noninvasively in a multitude of obliquities. Owing to these features, MR occupies a unique role in the evaluation of large vessel vasculitis.

Arteries↗
PubMed2001

Carotid MR angiography: phase II study of safety and efficacy for MS-325.

PURPOSE: To evaluate the safety and efficacy of MS-325 in patients suspected of having carotid arterial disease. MATERIALS AND METHODS: Fifty carotid arteries in 26 patients were imaged with three-dimensional spoiled gradient-recalled-echo magnetic resonance (MR) angiography at 5 and 50 minutes after injection of MS-325. MS-325 was administered intravenously as a single dose of 0.01, 0.03, or 0.05 mmol per kilogram of body weight as determined with a dose randomization scheme for four, nine, and 13 patients, respectively. Safety, including clinical laboratory changes and electrocardiographic monitoring, was assessed until approximately 3 days after injection. Conventional contrast agent-enhanced angiography was used as the standard of reference. Independent readers blinded to the dose interpreted the MR angiographic and conventional images. Images were assessed for location and extent of carotid arterial stenosis. RESULTS: There were no severe or serious adverse events. For the determination of clinically significant stenosis (>70%) on the 5-minute images, sensitivity, specificity, and accuracy (P =.07, three-way comparison) were 100%, 100%, and 100%; 63%, 100%, and 88%; and 40%, 75%, and 55% at 0.01, 0.03, and 0.05 mmol/kg, respectively. Sensitivity and specificity for images at 50 minutes after MS-325 administration showed the same trends as the 5-minute images. CONCLUSION: Overall accuracy for MS-325-enhanced carotid MR angiography performed during steady-state conditions of circulating contrast agent approximately 5 minutes after injection was high (88%-100%) at 0.03 and 0.01 mmol/kg. MS-325 was well tolerated at all evaluated doses.

Carotid Stenosis↗
PubMed2001

MR imaging of intrahepatic cholangiocarcinoma: use of ferumoxides for lesion localization and extension.

OBJECTIVE: The purpose of this study was to evaluate the use of ferumoxides in the visualization and localization of intrahepatic cholangiocarcinoma. CONCLUSION: The contrast-to-noise ratio of cholangiocarcinoma compared with that of the adjacent liver significantly (p < 0.03) improves after ferumoxides administration. Ferumoxides-enhanced MR imaging is a useful technique for the visualization and localization of intrahepatic cholangiocarcinoma.

Aged↗
PubMed2000

Microvascular obstruction and left ventricular remodeling early after acute myocardial infarction.

BACKGROUND: The presence of microvascular obstruction (MO) within infarcted regions may adversely influence left ventricular (LV) remodeling after acute myocardial infarction. This study examined whether the extent of MO directly alters the mechanical properties of the infarcted myocardium. METHODS AND RESULTS: Seventeen dogs underwent 90 minutes of balloon occlusion of the left anterior descending coronary artery, followed by reperfusion. Gadolinium-enhanced perfusion MRI and 3D-tagging were performed 4 to 6 and 48 hours (8 animals) and 10 days (9 animals) after reperfusion. Early increase in LV end-diastolic volume (from 42+/-9 to 54+/-14 mL, P<0.05) between 4 to 6 and 48 hours after reperfusion was predicted by both extent of MO (r=0.89, P<0.01) and infarct size (r=0.83, P<0.01), defined as MRI hypoenhanced and hyperenhanced regions, respectively. Multivariate analysis demonstrated that extent of MO had better and independent value to predict LV volume than overall infarct size. A strong inverse relationship existed between magnitude of first principal strain (r=-0.80, P<0.001) and relative extent of MO within infarcted myocardium. Also, infarcted myocardium involved by extensive areas of MO demonstrated reductions of circumferential (r=-0.61, P<0.01) and longitudinal (r=-0.53, P<0. 05) stretching. Furthermore, significant reductions of radial thickening (9+/-6% versus 14+/-3%, P<0.01) occurred in noninfarcted regions adjacent to infarcts that had increased (>35%) amounts of MO. CONCLUSIONS: In the early healing phase of acute myocardial infarction, the extent of MO in infarcted tissue relates to reduced local myocardial deformation and dysfunction of noninfarcted adjacent myocardium. Such strain alterations might explain the increased remodeling observed in patients with large regions of MO.

Animals↗
PubMed2000

Fast determination of regional myocardial strain fields from tagged cardiac images using harmonic phase MRI.

BACKGROUND: Tagged MRI of the heart is difficult to implement clinically because of the lack of fast analytical techniques. We investigated the accuracy of harmonic phase (HARP) imaging for rapid quantification of myocardial strains and for detailed analysis of left ventricular (LV) function during dobutamine stimulation. METHODS AND RESULTS: Tagged MRI was performed in 10 volunteers at rest and during 5 to 20 microg(-1). kg(-1). min(-1) dobutamine and in 9 postinfarct patients at rest. We compared 2D myocardial strains (circumferential shortening, Ecc; maximal shortening, E(2); and E(2), direction) as assessed by a conventional technique and by HARP. Full quantitative analysis of the data was 10 times faster with HARP. For pooled data, the regression coefficient was r=0.93 for each strain (P<0.001). In volunteers, Ecc and E(2) were greater in the free wall than in the septum (P<0.01), but recruitable myocardial strain at peak dobutamine was greater in the LV septum (P<0.01). E(2) orientation shifted away from the circumferential direction at peak dobutamine (P<0.01). HARP accurately detected subtle changes in myocardial strain fields under increasing doses of dobutamine. In patients, HARP-determined Ecc and E(2) values were dramatically reduced in the asynergic segments as compared with remote (P<0.001), and E(2) direction shifted away from the circumferential direction (P<0.001). CONCLUSIONS: HARP MRI provides fast, accurate assessment of myocardial strains from tagged MR images in normal subjects and in patients with coronary artery disease with wall motion abnormalities. HARP correctly indexes dobutamine-induced changes in strains and has the potential for on-line quantitative monitoring of LV function during stress testing.

Adult↗
PubMed2000

MR imaging of mediastinal lymph nodes: evaluation using a superparamagnetic contrast agent.

The purpose of this study was to determine whether intravenous injection of a magnetic resonance (MR) contrast agent, ultrasmall superparamagnetic iron oxide (ferumoxtran-10), can be useful in characterizing lymph nodes in patients with lung cancer. Twelve patients with known or suspected lung cancer were studied. Pre- and postcontrast injection of ferumoxtran-10 MR scans of the chest were obtained. Analysis of the signal intensities and bronchoscopic fine needle aspiration of a single node were performed in each patient. Six of 12 patients had a final diagnosis of lung cancer. T1-weighted images were best for localizing mediastinal lymph nodes. Signal intensity changes before and after contrast were best visualized on T2-weighted and gradient-echo images. All four patients with lung cancer who had nodes positive for malignancy at biopsy had no change in signal intensity of the nodes on T2 images. The signal intensity decreased in the remaining two patients, and the nodes were benign. Of the eight patients with benign disease, five had no change in signal intensity of the nodes. Therefore the sensitivity for tumor involvement of the nodes is 100%, but the specificity is only 37.5%. Ferumoxtran-10 is a contrast agent that can alter the signal intensity of lymph nodes. Lack of signal change may be due to malignant or inflammatory change. Studies in a larger population of lung cancer patients may help to characterize the utility of this agent further. J. Magn. Reson. Imaging 2000;12:899-904.

Aged↗
PubMed2000

Transmural contractile reserve after reperfused myocardial infarction in dogs.

OBJECTIVES: The goal of this study was to characterize detailed transmural left ventricular (LV) function at rest and during dobutamine stimulation in subendocardial and transmural experimental infarcts. BACKGROUND: The relation between segmental LV function and the transmural extent of myocardial necrosis is complex. However, its detailed understanding is crucial for the diagnosis of myocardial viability as assessed by inotropic stimulation. METHODS: Short-axis tagged magnetic resonance images were acquired at five to seven levels encompassing the LV from base to apex in seven dogs 2 days after a 90-min closed-chest left anterior descending coronary occlusion, followed by reflow. Myocardial strains were measured transmurally in the entire LV by harmonic phase imaging at rest and 5 ig x kg(-1) x min(-1) dobutamine. Risk regions were assessed by radioactive microspheres, and the transmural extent of the infarct was assessed by 2,3,5 triphenyltetrazolium chloride staining. RESULTS: Circumferential shortening (Ecc), radial thickening (Err) and maximal shortening at rest were greater in segments with subendocardial versus transmural infarcts, both in subepicardium (-1.1+/-1.0 vs. 2.5+/-0.6% for Ecc, -0.5+/-1.9 vs. -1.8+/-1.0% for Err, p < 0.05) and subendocardium (-2.0+/-1.4 vs. 2.8+/-0.8%, 2.4+/-1.7 vs. 0.0+/-0.9%, respectively, p < 0.05). Under inotropic stimulation, risk regions retained maximal contractile reserve. Recruitable deformation was found in outer layers of subendocardial infarcts (p < 0.01 for Ecc and Err) but also in inner layers (p < 0.01). Conversely, no contractile reserve was observed in segments with transmural infarcts. CONCLUSIONS: Under dobutamine challenge, recruitment of myofiber shortening and thickening was observed in inner layers of segments with subendocardial infarcts. These results may have important clinical implications for the detection of myocardial viability.

Animals↗
PubMed2000

Nontraumatic osteonecrosis: MR perfusion imaging evaluation in an experimental model.

RATIONALE AND OBJECTIVES: Because the nature and time course of changes in early, nontraumatic osteonecrosis at perfusion and magnetic resonance (MR) imaging are unknown, the authors evaluated this technique in the assessment of early osteonecrosis with a nontraumatic model. MATERIALS AND METHODS: Five rabbits underwent intravenous injection of lipopolysaccharide endotoxin followed by intramuscular injection of methylprednisolone. MR imaging of the femora was performed before and at weekly intervals after endotoxin injection. Histologic findings from the areas of osteonecrosis were correlated with the findings of MR imaging and MR perfusion studies. RESULTS: Histologic evaluation showed osteonecrosis in six femora of four animals 2-4 weeks after endotoxin injection. Findings on T1-weighted images of the femur were normal in all animals; T2-weighted images of one femur showed equivocal changes. On MR perfusion images, the baseline mean peak percentage of enhancement was 52.7% +/- 12.6. In the six areas without osteonecrosis, the mean percentage of enhancement was similar to the baseline percentage of enhancement at 1 week (62.2% +/- 31.2). In the four areas with diffuse osteonecrosis, there was essentially no contrast enhancement 1-4 weeks after endotoxin injection. CONCLUSION: T1- and T2-weighted MR imaging is insensitive to the presence of early nontraumatic osteonecrosis. MR perfusion imaging might be useful to detect early nontraumatic osteonecrosis.

Animals↗