Biomedical subjects
Philip A Araoz
Publications and source records attributed to Philip A Araoz.
Myocardial tagging and strain analysis at 3 Tesla: comparison with 1.5 Tesla imaging.
PURPOSE: To determine whether imaging at 3 T could improve and prolong the tag contrast compared to images acquired at 1.5 T in normal volunteers, and whether such improvement would translate into the ability to perform strain measurements in diastole. MATERIALS AND METHODS: Normal volunteers (N = 13) were scanned at 1.5 T (GE Signa CV/i) and 3.0 T (GE VH/i). An ECG-triggered, segmented k-space, spoiled-gradient-echo grid-tagged sequence was used during cine acquisition. Tag contrast was determined by the difference of the mean signal intensity (SI) of the tagline to the mean SI of the myocardium divided by the standard deviation (SD) of the noise (CNR(tag)). Matched short-axis (SA) slices were analyzed. Strain measurements were performed on images using a 2D strain analysis software program (harmonic phase (HARP)). RESULTS: The average CNR(tag) over the cardiac cycle was superior at 3 T compared to 1.5 T for all slices (3 T: 23.4 +/- 12.1, 1.5 T: 9.8 +/- 8.4; P < 0.0001). This difference remained significant at cycle initiation, end-systole, and the end R-R interval (at cycle termination: 3 T = 14.0 +/- 11.0 vs. 1.5 T = 4.4 +/- 3.5; P < 0.01). Strain measures were obtainable only in early systole for 1.5 T images, but were robust throughout the entire R-R interval for 3 T images. CONCLUSION: Imaging at 3 T had a significant benefit for myocardial tag persistence through the cardiac cycle. The improvement allowed strain analysis to be performed into diastole.
Lymphoepithelioma-like carcinoma of the lung: radiologic features of an uncommon primary pulmonary neoplasm.
OBJECTIVE: The purpose of this study was to review the chest radiographic, CT, and MRI appearances of primary pulmonary lymphoepithelioma-like carcinoma (LELC). CONCLUSION: Primary pulmonary LELC is histopathologically identical to nasopharyngeal carcinoma. The radiographic, CT, and MRI features of primary pulmonary LELC are nonspecific, often resembling those of bronchogenic carcinoma. Primary pulmonary LELC usually presents as a poorly circumscribed, enhancing, peripheral solitary pulmonary nodule on CT; necrosis may be present and is considered a poor prognostic sign. MRI shows isointense to low-intensity signal on T1-weighted images and mildly increased signal on T2-weighted images; enhancement of abnormal tissue is typical. Most patients present with early-stage disease. Primary pulmonary LELC should be suspected in selected patients and requires differentiation from bronchogenic carcinoma and metastatic nasopharyngeal carcinoma.
Revascularization in severe left ventricular dysfunction: the role of viability testing.
Revascularization is a treatment option for moderate-to-severe ischemic cardiomyopathy. Limitations of the current literature, lack of completed randomized trials, and higher periprocedural risks create significant uncertainty about the optimal treatment strategy. This review focuses on the available literature describing the effect of revascularization on outcome and the role of noninvasive viability testing. It attempts to identify a subset of patients likely to benefit from therapy.
Progression of subclinical coronary atherosclerosis: does obesity make a difference?
BACKGROUND: Obesity is associated with coronary artery calcification (CAC), a marker of the presence and extent of subclinical coronary atherosclerosis. Obesity adds incremental information in identifying those at higher risk of coronary heart disease to traditional risk factor assessment. The present study examined associations between obesity measures and progression of CAC in those at higher (> or =10%) and lower (<10%) 10-year coronary heart disease risk according to the Framingham risk equation. METHODS AND RESULTS: In this study, 443 asymptomatic white individuals >30 years of age (243 men) had baseline and follow-up CAC measurements an average of 8.9 years apart. Multivariable linear regression models were fit to determine associations of obesity measures at baseline with progression of CAC defined as log(e) of the difference between follow-up and baseline CAC area plus 1 divided by time (in years) between examinations, adjusting for baseline CAC quantity, age, sex, baseline hypertension status, and baseline cholesterol level. Among 329 participants (74.3%) in the lower-risk group, waist circumference (P=0.024), waist-to-hip ratio (P<0.001), body mass index (P=0.036), and being overweight compared with being underweight or of normal weight (P=0.008) were each significantly positively associated with progression of CAC. Among those at higher coronary heart disease risk, no baseline obesity measures were associated with CAC progression. CONCLUSIONS: Various measures of obesity were associated with increased progression of CAC in those at lower risk of coronary heart disease. Future studies examining the effectiveness of weight reduction strategies in reducing CAC progression among those with an otherwise favorable risk factor profile may be warranted.
Myocardial blood flow in patients with dilated cardiomyopathy: quantitative assessment with velocity-encoded cine magnetic resonance imaging of the coronary sinus.
PURPOSE: To quantify global myocardial perfusion using magnetic resonance imaging (MRI) in patients with heart failure due to idiopathic dilated cardiomyopathy (IDC) and to compare myocardial perfusion and microvascular reactivity with healthy subjects. MATERIALS AND METHODS: A total of 19 subjects (healthy volunteers (N = 12) and IDC patients (N = 7)) were studied using cine MRI to measure left ventricular (LV) mass and a velocity-encoded cine MRI technique to measure coronary sinus flow at rest and after dipyridamole-induced hyperemia. Absolute values of total myocardial blood flow (MBF) were calculated from coronary sinus flow and LV mass. RESULTS: At baseline, MBF was not significantly different in patients with IDC (0.48 +/- 0.07 mL/minute/g) and healthy subjects (0.55 +/- 0.19 mL/minute/g, P= 0.41). After dipyridamole administration, MBF in IDC patients increased to a level significantly less than that in normal volunteers (1.05 +/- 0.35 mL/minute/g vs. 1.99 +/- 1.05 mL/minute/g, P < 0.05). Consequently, MBF reserve was impaired in patients with IDC (2.19 +/- 0.77) compared to that in healthy subjects (3.51 +/- 1.29, P < 0.05). A moderate correlation was found between MBF reserve and LV ejection fraction (r = 0.48, P < 0.05). CONCLUSION: MBF reserve is reduced in patients with IDC, indicating that coronary microcirculatory flow is impaired. This integrated MRI approach allows quantitative measurement of global MBF in humans and may have the potential to study the effects of pharmacological interventions on myocardial perfusion.
Imaging of chronic thromboembolic pulmonary hypertension.
Explore the source record for details and available documents.
3 Tesla MR imaging provides improved contrast in first-pass myocardial perfusion imaging over a range of gadolinium doses.
PURPOSE: To compare myocardial enhancement during first-pass myocardial perfusion imaging at 3.0 Tesla (T) and 1.5T. MATERIALS AND METHODS: First-pass myocardial perfusion imaging was performed on twelve normal subjects at 3T and 1.5T using an interleaved notched saturation recovery gradient echo pulse sequence. Subjects received either 0.10 mmol/kg for both scans (group 1), 0.075 mmol/kg for both scans (group 2), or 0.075 mmol/kg for the 3T scan and 0.10 mmol/kg for the 1.5T scan (group 3). RESULTS: Contrast enhancement was significantly greater at 3T than at 1.5T for the 12 subjects whether enhancement was normalized to baseline signal intensity (2.58 +/- 0.76 vs. 1.52 +/- 0.37, p < 0.0001) or to noise (57.6 +/- 19.7 vs. 14.7 +/- 7.8, p < 0001). For each of the three groups, contrast enhancement was significantly greater at 3T versus 1.5T (p < 0.0001, p < 0.001, p < 0.008 when normalized to baseline signal; p < 0.0001 for all groups when normalized to noise). CONCLUSION: 3T improves contrast in first-pass myocardial perfusion imaging at either 0.10 mmol/kg or 0.075 mmol/kg.
Imaging findings in Takayasu's arteritis.
OBJECTIVE: The objective of our study was to evaluate the clinical usefulness of cross-sectional imaging for establishing the diagnosis of Takayasu's arteritis (TA), an inflammatory vascular disorder that produces arterial stenoses and aneurysms primarily involving the thoracoabdominal aorta and its branches and the pulmonary arteries. CONCLUSION: CT and MRI findings of TA include vascular wall thickening and enhancement early in the disease, and arterial stenoses, occlusions, and aneurysms later in the disease. Cross-sectional imaging is useful for establishing the diagnosis of TA and for showing response to nonsurgical therapy or for planning a surgical intervention.
The year in cardiac imaging.
Explore the source record for details and available documents.
The quantification of infarct size.
We sought to summarize the published evidence regarding the measurement of infarct size by serum markers, technetium-99m sestamibi single-photon emission computed tomography (SPECT) myocardial perfusion imaging, and magnetic resonance imaging. The measurement of infarct size is an attractive surrogate end point for the early assessment of new therapies for acute myocardial infarction. For each of these three approaches, we reviewed reports published in English providing the clinical validation for the measurement of infarct size and the relevant clinical trial experience. The measurement of infarct size by serum markers has multiple theoretical and practical limitations. The measurement of troponin is promising, but the available data validating this marker are limited. Sestamibi SPECT imaging has five separate lines of published evidence supporting its validity and has received extensive study in multicenter trials. Magnetic resonance imaging has great promise but has less clinical validation and no multicenter trial experience. Therefore, SPECT sestamibi imaging is currently the best available technique for the quantitation of infarct size to assess the incremental treatment benefit of new therapies in multicenter trials of acute myocardial infarction.
The effect of helical computed tomography on diagnostic and treatment strategies in patients with suspected pulmonary embolism.
BACKGROUND: Helical computed tomography (CT) has been proposed as a first-line test for the diagnosis of pulmonary embolism. How the test affects the diagnostic evaluation of patients with suspected pulmonary embolism is unknown. METHODS: We examined a cohort of 360 patients evaluated for pulmonary embolism at a teaching hospital in the 4 years following the introduction of the helical CT scan. We collected patient demographic and clinical data to calculate the pretest likelihood of pulmonary embolism; we then read the test results and determined rates of further testing and treatment for pulmonary embolism. RESULTS: After the helical CT scan became available, the number of patients referred for pulmonary embolism testing increased markedly from 170 to 624 total evaluations during 1997 to 2000 (P <0.01). This rise was due to increased use of the helical CT scan (9% to 83% of evaluations, P <0.01) as the use of ventilation-perfusion scanning (79% to 17%, P = 0.03) and pulmonary angiography (12% to <1%, P <0.01) fell. There was no change in the pre-test likelihood of disease over time, but the percentage of scans that were positive for pulmonary embolism rose (14% to 32%, P =0.02). Clinicians treated all patients who had a positive CT scan, but became less likely over time to order further testing for patients who had a negative scan (30% to 12%, P = 0.02). CONCLUSION: At this academic medical center, introduction of the helical CT scan had a profound effect on the evaluation of pulmonary embolism, resulting in more frequent use of the CT scan, and more frequent diagnosis and treatment of pulmonary embolism, despite no change in the pretest probability of disease. Future studies should confirm our findings and determine whether increased detection of pulmonary emboli results in improved outcomes.
MR findings of collateral circulation are more accurate measures of hemodynamic significance than arm-leg blood pressure gradient after repair of coarctation of the aorta.
PURPOSE: To determine the relationship between percent stenosis and three indicators of hemodynamic significance-arm-leg blood pressure gradient, direct visualization of collaterals, and percent increase flow from proximal to distal descending thoracic aorta-in patients with prior repair of coarctation of the aorta (CoA). MATERIALS AND METHODS: Magnetic resonance imaging (MRI) examinations of 19 patients with prior repair of CoA were retrospectively reviewed. Percent stenosis was compared to the arm-leg blood pressure gradient as obtained from chart review, the depiction of collaterals by gadolinium-enhanced magnetic resonance angiography (MRA), and the percent increased flow in the distal thoracic aorta as measured by velocity-encoded cine MRI. Some imaging series or blood-pressure values were not available in some patients. All of the data were available for 15 of the 19 patients. RESULTS: The arm-leg blood pressure gradient showed no statistical association with percent stenosis (R(2) = 0.10, P = 0.22), direct visualization of collaterals (P = 0.80), or percent increase in flow (R(2) < 0.01, P = 0.85). Percent stenosis did show association with visualization of collaterals (P = 0.01) and increase flow (R(2) = 0.62, P < 0.01). CONCLUSION: The arm-leg blood pressure gradient is not a reliable indicator of hemodynamic significance of restenosis in patients with prior repair of CoA. Direct visualization of collateral vessels by MRA and percent increase in flow from proximal to distal descending thoracic aorta are reliable indicators of hemodynamic significance.
Computed tomography for functional evaluation of the heart.
Explore the source record for details and available documents.
Helical CT pulmonary angiography predictors of in-hospital morbidity and mortality in patients with acute pulmonary embolism.
PURPOSE: To determine if CT variables predict in-hospital morbidity and mortality in patients with pulmonary embolism (PE). MATERIALS AND METHODS: CT scans and charts of 173 patients with CT scans positive for PE were reviewed. CT scans were reviewed for leftward ventricular septal bowing, increased right ventricle (RV) to left ventricle (LV) diameter ratio, clot burden, increased pulmonary artery to aorta diameter ratio, and oligemia. Charts were reviewed for severe morbidity and mortality outcomes: death from pulmonary emboli or any cause, and cardiac arrest. Charts were also reviewed for milder morbidity outcomes: intubation, vasopressor use, or admission to an intensive care unit (ICU) and for multiple comorbidities. RESULTS: No CT predictor was significantly associated with severe morbidity or mortality outcomes. Ventricular septal bowing and increased RV/LV diameter ratio were both associated with subsequent admission to an ICU (P = 0.004 and P = 0.025, respectively). Oligemia (either lung) was associated with subsequent intubation; right lung oligemia was associated with the subsequent use of vasopressors. After controlling for history of congestive heart failure, ischemic heart disease, and pulmonary disease, both septal bowing and an increased RV/LV diameter ratio remained associated with admission to an ICU. CONCLUSION: No CT variables predicted severe in-hospital morbidity and mortality (death from pulmonary embolism, death from any cause, or cardiac arrest) in patients with PE. However, ventricular septal bowing and increased RV/LV diameter ratio were both strongly predictive of less severe morbidity, namely, subsequent ICU admission, and oligemia was associated with subsequent intubation and vasopressor use.
Images in cardiovascular medicine. Magnetic resonance angiography of criss-cross heart.
Explore the source record for details and available documents.
Thoracic complications of illicit drug use: an organ system approach.
Illicit drug use constitutes a major health problem and may be associated with various thoracic complications. These complications vary depending on the specific drug used and the route of administration. Commonly abused drugs that may play a role in causing thoracic disease include cocaine, opiates, and methamphetamine derivatives. Intravenously abused oral medications may contain filler agents that may be responsible for disease. Thoracic complications may be categorized as pulmonary, pleural, mediastinal, cardiovascular, and chest wall complications. Pulmonary complications of drug abuse include pneumonia, cardiogenic edema, acute lung injury, pulmonary hemorrhage, and aspiration pneumonia. Filler agents such as talc may result in panacinar emphysema or high-attenuation upper-lobe conglomerate masses. The primary pleural complication of illicit drug use is pneumothorax. Mediastinal and cardiovascular complications of illicit drug use include pneumomediastinum, cardiomyopathy, myocardial infarction, aortic dissection, and injection-related pseudoaneurysms. Chest wall complications include diskitis and vertebral osteomyelitis, epidural abscess, necrotizing fasciitis, costochondritis, and septic arthritis. Categorization of thoracic complications of illicit drug use may facilitate understanding of these disorders and allow accurate diagnosis.