Song Shou Mao

Normal Thoracic Aorta Diameter on Cardiac Computed Tomography in Healthy Asymptomatic Adults : Impact of Age and Gender

RATIONALE AND OBJECTIVESnTo establish the normal criterion of ascending aortic diameter (AAOD) measured by 64 multidetector computed tomography (MDCT) and electron beam computed tomography (EBT) based on gender and age.nnnMATERIALS AND METHODSnA total of 1442 consecutive subjects who were referred for evaluation of possible coronary artery disease underwent coronary computed tomographic (CT) angiography (CTA) and coronary artery calcium scanning (CACS) (55 + 11 years, 65% male) without known coronary heart disease, hypertension, chronic pulmonary and renal disease, diabetes, and severe aortic calcification. The AAOD aortic diameter, descending aortic diameter (DAOD), pulmonary artery (PAD), and chest anteroposterior diameter (CAPD), posterior border of the sternal bone to the anterior border of the spine, were measured at the slice level of mid-right pulmonary artery using end systolic trigger imaging. The volume of four chambers, ejection fraction of left ventricle, and cardiac output were measured in 56% of the patients. Patients demographic information, age, gender, weight, height, and body surface area were recorded. The mean value and age-specific and gender-adjusted upper normal limits (mean +/- 2 standard deviation) were calculated. The linear correlation analysis was done between AAOD and all parameters. The reproducibility, wall thickness, and difference between end-systole and end-diastole were calculated.nnnRESULTSnAAOD has significant linear association with age, gender, DAOD, and pulmonary artery diameter (P < .05). There is no significant correlation between AAOD and body surface area, four-chamber volume, left ventricular ejection fraction, cardiac output, and CAPD. The mean intraluminal AAOD was 31.1 +/- 3.9 and 33.6 +/- 4.1 mm in females and males, respectively. The upper normal limits (mean +/- 2 standard deviations) of intraluminal AAOD, were 35.6, 38.3, and 40 mm for females and 37.8, 40.5, and 42.6 mm for males in age groups 20-40, 41-60, and older than 60 years, respectively. Intraluminal aortic diameters should parallel echocardiography and invasive angiography. Traditional cross-sectional imaging (with CT and magnetic resonance imaging) includes the vessel wall. The mean total AAOD was 33.5 and 36.0 mm in females and males, respectively. The upper normal limits (mean +/- 2 standard deviations) of intraluminal AAOD were 38.0, 40.7 and 42.4 mm for females and 40.2, 42.9, and 45.0 mm for males in age group 20 to 40, 41 to 60, and older than 60 years, respectively. The inter- and intraobserver, scanner, and repeated measurement variabilities were low (r value >0.91, P < .001, coefficient variation <3.2%). AAOD was 1.7 mm smaller in end-diastole than end-systole (P < .001).nnnCONCLUSIONSnThe AAOD increases with age and male gender. Gender-specific and age-adjusted normal values for aortic diameters are necessary to differentiate pathologic atherosclerotic changes in the ascending aorta. Use of intraluminal or total aortic diameter values depends on the comparison study employed.

Valvular and thoracic aortic calcium as a marker of the extent and severity of angiographic coronary artery disease

BACKGROUNDnThe presence of calcified extracoronary structures as a useful indicator of underlying coronary artery disease (CAD) has not yet been established. The purpose of this study was to evaluate whether valvular and thoracic aortic calcification is associated with obstructive CAD.nnnMETHODSnWe evaluated 99 patients who underwent both coronary angiography and electron beam tomography (EBT) coronary scanning. We identified the presence, absence, and amount of calcification in the aortic valve (AVC), mitral annulus (MAC), descending aorta (DAC), and ascending aorta (AAC). The extent of CAD was graded according to the number of vessels diseased (VD).nnnRESULTSnPatients with multivessel disease (MVD) had a higher proportion of DAC. The presence of DAC significantly increased the specificity of EBT to detect CAD (58% with a calcium score >0 to 88% for calcium score>0 and DAC >0, P <.001). Both AAC and DAC were associated with a significantly higher rate of MVD in women (DAC, 63% in MVD vs 19% without, P <.01.; AAC, 65% vs 22%, P <.05). MAC had no relationship to either stenosis severity or the presence of obstructive CAD. AVC was the strongest predictor of the severity of CAD and predicted the presence of 3-vessel disease.nnnCONCLUSIONnAVC and thoracic aortic calcification as detected with EBT are associated with the angiographic extent and severity of CAD and add incremental diagnostic value to the coronary artery calcium score. MAC does not add incremental value.

Measurement of Phantomless Thoracic Bone Mineral Density on Coronary Artery Calcium CT Scans Acquired with Various CT Scanner Models

PURPOSEnTo determine the accuracy and precision of thoracic phantomless bone mineral density (BMD) measurements obtained on coronary artery calcium (CAC) computed tomography (CT) scans by using a variety of commercially available CT scanners.nnnMATERIALS AND METHODSnThe institutional review board approved this Health Insurance Portability and Accountability Act-compliant study. A total of 4126 asymptomatic subjects (2022 [49%] men, 2104 [51%] women; mean age, 63.7 years ± 11.8 [standard deviation]) underwent CAC CT with the use of a quantitative CT calibration phantom for evaluation of subclinical atherosclerosis. Two hundred eighty subjects also underwent CT of the chest, abdomen, and pelvis (C7 through L5). Mean BMD of three consecutive thoracic vertebrae (in the T7-T10 range) was measured in all 4126 subjects. Individual calibration factors for each phantom insert and a general calibration factor for the spine were determined for each CT scanner model. The study population was then divided into three subgroups: All calibration factors were generated from group 1 (n = 1536) and were applied and tested in group 2 (n = 1587), and effects of various image acquisition parameters were assessed in group 3 (n = 1003). Accuracy (bias) and precision of thoracic phantomless BMD measurements across 14 CT scanner models from five manufacturers were determined.nnnRESULTSnPhantomless BMD values correlated highly with standard phantom-based quantitative CT BMD values (r = 0.987, P < .001). Bias was 3.9% ± 1.4 for phantomless BMD measurements, and the mean coefficient of variation for the general calibration factor was 4.9% ± 2.4.nnnCONCLUSIONnPhantomless BMD can be measured accurately on CAC CT scans acquired with a variety of CT scanners without additional radiation exposure.

Trabecular Bone Mineral Density Measurement Using Thoracic and Lumbar Quantitative Computed Tomography

PURPOSEnTo evaluate the agreement of bone mineral density (BMD) between lumbar (L) and individual thoracic (T) vertebrae and identify a standard thoracic spine level for BMD assessment in cardiac computed tomography (CT) images.nnnMATERIALS AND METHODSnThree hundred subjects who underwent simultaneous chest and abdomen CT scans for clinical indications were included. A calibration phantom that extended from the first thoracic spine (T(1)) to the fifth lumbar (L(5)) was employed. Vertebral BMD were measured by QCT 5000 and NVivo systems. The association between three consecutive lumbar (L1-L3) and thoracic BMD (3T, initiation site equivalent to left main coronary caudally) was evaluated.nnnRESULTSnThere was a gradual decrease in BMD values from T(1) to L(3,) subsequently increasing in L(4) and L(5) in both genders. When stratified by gender, 3T BMD was significantly higher versus L(1-3) BMD (156.9 versus 141.9vmg/cm(3), P < .001) for women as well as for men (164.8 versus 151.0 mg/cm(3), P < .001). There is good correlation between 3T and L(1-3) BMD, the Pearsons correlation coefficients are 0.91 and 0.93 for women and men, respectively. We further analyzed the associations between L(1-3) and any individual spine of T(1)-L(5) and similar relationships were observed (r value, 0.62-0.98). The intraobserver, interobserver, and interscan variation measurement of thoracic quantitative CT was 2.5 (1.0, 95% CI 0.099-1.004); 2.6 (1.0, 95CI% 0.992-1.007), and 2.8% (1.0,95% 0.0994-1.008), respectively.nnnCONCLUSIONnThe 3T BMD was highly correlated with L(1-3) BMD. Thoracic BMD can be measured during cardiac and lung CT imaging without need for additional participant burden or radiation dose. This highly reproducible methodology is actively being applied to large cohort studies to evaluate the prevalence of osteoporosis and track BMD over time.

Gender differences in coronary artery diameter are not related to body habitus or left ventricular mass.

Smaller coronary artery diameter portends worse outcomes after coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI). The suggestion that women have smaller coronary artery diameters than men has not been validated by a large‐scale study.

Application of quantitative computed tomography for assessment of trabecular bone mineral density, microarchitecture and mechanical property

Osteoporosis is a common metabolic bone disease, causing increased skeletal fragility characterized by a low bone mass and trabecular microarchitectural deterioration. Assessment of the bone mineral density (BMD) is the primary determinant of skeletal fragility. Computed tomography (CT)-based trabecular microarchitectural and mechanical assessments are important methods to evaluate the skeletal strength. In this review, we focus the feasibility of QCT BMD measurement using a calibration phantom or phantomless. The application of QCT could extend the bone mineral density assessment to all patients who underwent a heart, lung, whole-body, and as well as all routine clinical implications of CT scan.

Detection and quantification of myocardial perfusion defects by resting single-phase 64-slice cardiac computed tomography angiography compared with SPECT myocardial perfusion imaging.

ObjectiveHypoenhanced regions on cardiac computed tomography angiography (CCTA) correlate with myocardial hypoperfusion. We evaluated the ability of resting single-phase 64-slice CCTA to detect the presence of myocardial infarction (MI) compared with nuclear myocardial perfusion imaging (MPI). MethodsOne hundred and forty symptomatic patients (age 66±12 years, 64% men) with an irreversible perfusion defect (n=69) or a normal/reversible perfusion defect (n=71) on MPI were subjected to CCTA for further evaluation. MI on CCTA was detected visually on the basis of areas of hypoattenuation (dark) in the myocardium and the corresponding Hounsfield Units (HU) were measured. ResultsCCTA accurately detected MI in 62 patients with an irreversible perfusion defect on MPI, yielding a sensitivity of 90%, a specificity of 94%, a negative predictive value of 91%, and a positive predictive value of 94%. The mean HU of normal and infarcted left ventricular myocardium was 107±23 and 16±40, respectively (P<0.001). An HU cut-off of 28 detected the presence of myocardial scar with 86% sensitivity and 59% specificity. The infarct volume measured by CCTA correlated well with the summed rest score (r=0.567; P<0.001) and the summed stress score (r=0.489; P<0.001) on MPI. In a substudy of 50 patients, the GE perfusion tool yielded a sensitivity of 92%, a specificity of 73%, an negative predictive value of 91%, and a positive predictive value of 76% in detecting MI. ConclusionResting single-phase CCTA is highly accurate in detecting and quantifying MI. This study highlights a novel clinical utility of CCTA in addition to assessment of plaque burden and stenosis with no risk of additional radiation or contrast exposure to the patient.

Noncontrast cardiac computed tomography image-based vertebral bone mineral density: the Multi-Ethnic Study of Atherosclerosis (MESA).

RATIONALE AND OBJECTIVESnCardiac computer tomography (CT) image-based vertebral bone mineral density (BMD) assessment and the influence of cardiovascular disease risk factors on BMD have not been systematically evaluated, especially in a community-based, multiethnic population.nnnMETHODSnA cross-sectional study design is used to determine if cardiac CT image is a reliable source to assess vertebral BMD, and a total of 2028 CT images were obtained from the Multi-Ethnic Study of Atherosclerosis, a large, diverse US cohort of adults 45 to 84 years of age.nnnRESULTSnCardiac CT image allows the rapid assessment of vertebral BMD and related fractures. The mean BMD was significantly higher in men compared with women for thoracic vertebrae (143.2 ± 41.2 vs 138.7 ± 42.7 mg/cm³, respectively, P = .014), as well as for lumbar vertebrae (125.0 ± 37.9 vs 117.2 ± 39.4 mg/cm³, respectively, P < .0001). Thoracic and lumbar BMDs are closely correlated (correlation coefficient 0.87, P < .001), independent of age and other confounders including sex and race. African American men had the highest thoracic BMD among all race/ethnicity and sex subgroups. Prevalence of fractures in total vertebrae is 4.2%. Lumbar had approximately 2 times higher prevalence of fracture than thoracic, and the prevalence of vertebral fractures is 1.5% and 3.1% for thoracic and lumbar vertebrae, respectively.nnnCONCLUSIONSnUsing cardiac CT images to garner and assess vertebral BMD is a feasible and reliable method. Cardiac CT has the additional advantages of evaluate vertebral bone health while assessing cardiovascular disease risk with no extra cost or radiation exposure.

Very small calcifications are detected and scored in the coronary arteries from small voxel MDCT images using a new automated/calibrated scoring method with statistical and patient specific plaque definitions

A negative (zero) Agatston coronary calcium score (CCS) by current methods confers a very low risk for hard coronary events during the next years. However, controversy remains on how to use a negative score since some hard events still occur. We report on a new method with improved detection sensitivity for very small calcifications with the potential to more confidently rule out early atherosclerotic disease. Seventy-eight (78) patients with negative Agatston scores by conventional methods with 2.5xa0mm slices were selected from routine GE 64 MDCT scans. Each scan was reconstructed a second time from the same data to create 0.625xa0mm isotropic voxels. The 2.5xa0mm images were manually scored by the usual Agatston method using the GE SmartScore™ software. Both the 2.5 and 0.625xa0mm image sets were scored with a new automated and calibrated method (N-vivo™, Image Analysis). The software automatically computes dual scoring thresholds that are statistically defined and specific for each patient, scanner, and scan. The images were hybrid calibrated by simultaneous scanned phantoms in combination with in vivo blood/muscle references. The output reported the calibrated mass scores along with the number of plaques using 18 pt, 3-D connectivity criteria. A CCS Test phantom with known CaHA microspheres was used to validate the method. Twenty-three percent (18 of 78) of the patients with negative Agatston scores by the conventional method scored positive for coronary calcifications by the N-vivo method. The number of small plaques scored per patient varied from 1 to 4. One patient with a single small calcification suffered a hard coronary event during the CT scan. All of the detected plaques were located in the proximal heart. The conventional CCS method misclassified 23% of these patients as having negative coronary calcium scores. The N-vivo automated scoring method with small voxel CT images increased the detection sensitivity of small calcifications with no increase in radiation dose. Detection of small coronary calcified plaques occult to conventional scoring methods may increase the negative predictive power of calcium scoring and may improve plaque composition analysis.

Dual-standard reference values of left ventricular volumetric parameters by multidetector CT angiography

BACKGROUNDnThe papillary and trabecular muscles constitute a significant percentage of left ventricular mass and volume. The influence of the papillary and trabecular muscles on left ventricular parameters has not been described with multidetector CT angiography.nnnOBJECTIVEnThe aims of this study are (1) to derive reference values for left ventricular volumetric parameters both including and excluding the papillary and trabecular muscles and (2) to establish the optimal segmentation method for measuring these values.nnnMETHODSnA total of 179 subjects (mean age, 55.4 ± 9 years; 102 women) without heart disease and at low risk of cardiovascular disease who underwent CT angiography were selected. Left ventricular volumes, myocardial volume, and ejection fraction were measured with epicardial and 2 endocardial trace methods, including and excluding trace for the papillary and trabecular muscles. Values of all parameters obtained by both endocardial trace methods were compared.nnnRESULTSnSignificant difference between both trace groups for all parameters on both sexes was found (P < .001). Significant differences in precision error of remeasurement were found in the including trace (3.6%) compared with the excluding trace (4.7%; P < .05) and in the epicardial trace (2.2%) compared with both endocardial traces (P < .001).nnnCONCLUSIONnThe left ventricular parameters measured by CT angiography were influenced significantly by the trace method by including or excluding the papillary and trabecular muscles. The dual-standard reference values of left ventricular parameters were established, and the optimal segmentation methods were definite in considering the heart size and image quality studied with retrospective and prospective CT angiography.