Experimental verification of principal losses in a regulatory particulate matter emissions sampling system for aircraft turbine engines

A sampling system for measuring emissions of nonvolatile particulate matter (nvPM) from aircraft gas turbine engines has been developed to replace the use of smoke number and is used for international regulatory purposes. This sampling system can be up to 35 m in length. The sampling system length in addition to the volatile particle remover (VPR) and other sampling system components lead to substantial particle losses, which are a function of the particle size distribution, ranging from 50 to 90% for particle number concentrations and 10-50% for particle mass concentrations. The particle size distribution is dependent on engine technology, operating point, and fuel composition. Any nvPM emissions measurement bias caused by the sampling system will lead to unrepresentative emissions measurements which limit the method as a universal metric. Hence, a method to estimate size dependent sampling system losses using the system parameters and the measured mass and number concentrations was also developed (SAE 2017; SAE 2019). An assessment of the particle losses in two principal components used in ARP6481 (SAE 2019) was conducted during the VAriable Response In Aircraft nvPM Testing (VARIAnT) 2 campaign. Measurements were made on the 25-meter sample line portion of the system using multiple, well characterized particle sizing instruments to obtain the penetration efficiencies. An agreement of ± 15% was obtained between the measured and the ARP6481 method penetrations for the 25-meter sample line portion of the system. Measurements of VPR penetration efficiency were also made to verify its performance for aviation nvPM number. The research also demonstrated the difficulty of making system loss measurements and substantiates the E-31 decision to predict rather than measure system losses.

Progression of coronary artery calcification in asymptomatic individuals with pre-existing calcium score

AIM

Coronary artery calcification (CAC) has been introduced as a reliable, non-invasive marker of atherosclerosis. In this retrospective study, we investigated the progression of CAC using electron beam computed tomography.

METHODS

The study enrolled 598 individuals (521 males; mean age: 59.3±8.3 years) with initial CAC score (CACS) ≥10. The mean interscan period was 2.4±1.35 years (range: 1-7 years). The mean CACS, for the entire cohort, was 262.4±423.9 at baseline scan and 380.3±547.6 at follow-up. The mean annualized progression in CACS was 57.7±123.7; 47.4±66.5 in females and 58.3±128.1 in males (P=0.46). The mean annualized progression in CACS was 39.6±61.3 in individuals <60 years and 75.7±161.5 in individuals >60 years (P=0.0003). In multivariate analysis, only baseline CACS (P<0.0001) and smoking (P=0.002) were independently associated with the annual change in CACS.

Coronary artery calcification progression in asymptomatic individuals with initial score of zero

The aim of this study is to determine the progression of coronary artery calcification (CAC) using electron beam computed tomography (CT) when the initial CAC score (CACS) is zero and to determine the best interval to repeat a CAC scan. We studied 388 individuals with zero CACS (308 males; mean age: 48.8 ± 8.26 years) who underwent 2 consecutive CT scans in a period of at least 12 months apart. The interscan period was 2.99 ± 1.35 years (range: 1-6 years). Three-quarters of the individuals (75%) did not develop any CAC progression, 20.87% presented CAC progression of 1 to 10, 3.6% had 11 to 50, whereas only 0.51% had >50. The average time of new CAC development was 4.2 ± 1.1 years. Individuals with CAC progression presented higher incidence of hypertension, diabetes mellitus, hypercholesterolaemia and higer frequency of male gender than those with without CAC changes (p<0.02). No cardiac events occurred during the follow-up period.

Differences in Clinical Profile of Individuals With Severe and Markedly Elevated Coronary Artery Calcification Detected by Electron Beam Computed Tomography

Although several studies have demonstrated the association between coronary artery calcification (CAC) and coronary artery disease events, the underlying mechanism has not been fully elucidated. Furthermore, extensive CAC still remains a poorly understood phenomenon. The objective of this study is to determine the clinical characteristics and differences between 831 asymptomatic individuals with very high CAC scores (CACS ≥1000) and 497 asymptomatic individuals with CAC scores of 400 to 999. Individuals with CACS ≥1000 were more likely to have hypertension ([HTN]; P = .0004), hypercholesterolemia ( P = .0001), diabetes mellitus ([DM] P = .005), and high body mass index ([BMI]; P = .03) compared with individuals with CACS = 400-999. On multivariable analysis, age ( P < .0001) and BMI ( P = .01) were found to be significant risk factors for the presence of very high CAC. While for males, age ( P < .0001), hypercholesterolemia ( P = .001), DM ( P = .002), and obesity ( P = .003) were independent risk factors; in females only HTN ( P = .04) was independent risk factor.

Prevalence of noncalcified coronary plaque in patients with calcium score of 0: the silent enemy

Noncalcified coronary artery plaques (NCAPs) are susceptible to rupture, resulting in coronary artery thrombosis. Using computer tomography coronary angiography (CTCA), we evaluated the prevalence and degree of stenosis caused by NCAP in patients without coronary artery calcification (CAC). A retrospective analysis of 447 symptomatic patients with 0 CAC score revealed negative CTCA in 400 (89.5%). Noncalcified coronary artery plaques were demonstrated in 47 (10.5%), with 4 presenting stenosis >50%. Patients with positive CTCA, compared to those with normal CTCA, had significantly higher mean age (56.2 years vs 50.6 years, P < .004) and higher pretest coronary artery disease (CAD) probability (26% vs 34%, P < .0001). Noncalcified coronary artery plaque was predominantly developed in the proximal segment of the left anterior descending artery. Noncalcified coronary artery plaque is present in up to 10% of patients with a CAC score of 0. Computer tomography coronary angiography could be of diagnostic value in symptomatic patients with multiple risk factors for CAD, even in the absence of CAC.

The abdominal aortic aneurysm sac after endoluminal exclusion: a medium-term morphologic follow-up based on volumetric technology

PURPOSE

The purpose of this study was to evaluate the role of three-dimensional spiral computed tomographic angiography (SCTA) for the assessment of the feasibility and results of endoluminal repair of infrarenal abdominal aortic aneurysm.

METHODS

Laboratory studies: Phantom glass aneurysms, filled with contrast, underwent SCTA. The correlation between SCTA and laboratory measurements of linear dimensions and volumes was highly accurate (r(2) = 1.0).

CLINICAL STUDIES

From the first 7 patients that were suitable for endoluminal repair, the correlation between SCTA and angiocatheter measurements was 0.85 to 0.99 (P <.04), but there was poor agreement between individual values. As determined from the measurements by 2 experienced investigators, intraobserver and interobserver errors for volume calculation in 12 randomly chosen scans from a total of 120 scans were 5.7 and 4.4 mL, respectively (range of volumes, 100-403 mL). The conditions of 53 patients were judged suitable for endoluminal repair of which 30 patients reached 1 year or more follow-up. The median aneurysm neck length and diameter were 24.5 mm (range, 11.5-60.8 mm) and 23.4 mm (18.3-31.5 mm), respectively. The fate of the sac after endografting by two techniques (pre-expanded polytetrafluoroethylene [PTFE] fixed with Palmaz stents and endografts) was defined with three-dimensional SCTA.

RESULTS

The sac volume after endografting by pre-expanded PTFE (n = 12 patients) showed a significant median increase (P =.02) from 129 mL before surgery to 141 mL at 5 days after the operation with no change at 6 (139 mL), 12 (137 mL), and 18 (159 mL) months later. With the endografts (n = 18), there was an initial increase in median volume at 5 days (179-194 mL; P =.02) and then a significant shrinkage at 6 (148 mL; P =.012) and 12 (94.9 mL; P =.02) months.

CONCLUSION

Three-dimensional SCTA has been validated and is both precise and reliable. Interobserver and intraobserver errors are within acceptable ranges. Angiocatheter measurements are less accurate and may give misleading information when used for patient selection and endograft construction. The sac volume increased after endografting and later shrank in patients who were treated with endografts, but not in those patients treated with pre-expanded PTFE. We propose that three-dimensional SCTA should be regarded as the gold standard for linear and volumetric measurement for infrarenal abdominal aortic aneurysm.

Hepatic artery aneurysms: evaluation using three-dimensional spiral CT angiography

Hepatic artery aneurysms are rare and frequently difficult to diagnose. Computed tomography (CT) and ultrasound rarely make the definitive diagnosis and angiography is usually required. We present three cases of hepatic artery aneurysms in which the definitive diagnosis was made on three-dimensional (3-D) spiral CT angiography-to our knowledge, this has not previously been described. Our experience shows that in many cases of hepatic artery aneurysm, conventional angiography need only be performed as a prelude to embolization.

Drug and AIDS education for Australian youth. The Get Real project

It illustrates an approach to "at risk" youth which implicates the age group in planning and application, in an area where they are involved. It is a communication and health initiative which has achieved a good measure of success in Australia with the rock'n roll music sub culture. It reaches out not only in the drugs area but also in the area of AIDS.