Standardized evaluation methodology and reference database for evaluating coronary artery centerline extraction algorithms

Efficiently obtaining a reliable coronary artery centerline from computed tomography angiography data is relevant in clinical practice. Whereas numerous methods have been presented for this purpose, up to now no standardized evaluation methodology has been published to reliably evaluate and compare the performance of the existing or newly developed coronary artery centerline extraction algorithms. This paper describes a standardized evaluation methodology and reference database for the quantitative evaluation of coronary artery centerline extraction algorithms. The contribution of this work is fourfold: 1) a method is described to create a consensus centerline with multiple observers, 2) well-defined measures are presented for the evaluation of coronary artery centerline extraction algorithms, 3) a database containing thirty-two cardiac CTA datasets with corresponding reference standard is described and made available, and 4) thirteen coronary artery centerline extraction algorithms, implemented by different research groups, are quantitatively evaluated and compared. The presented evaluation framework is made available to the medical imaging community for benchmarking existing or newly developed coronary centerline extraction algorithms

A systematic review of the clinical effectiveness of 64-slice or higher computed tomography angiography as an alternative to invasive coronary angiography in the investigation of suspected coronary artery disease

<p>Abstract</p> <p>Background</p> <p>This systematic review summarized recent evidence pertaining to the clinical effectiveness of 64-slice or higher computed tomography angiography (CTA) in patients with suspected coronary artery disease (CAD). If CTA proves to be a successful diagnostic performance measure, it could prevent the use of invasive diagnostic procedures in some patients. This would provide multiple health and cost benefits, particularly for under resourced areas where invasive coronary angiography is not always available.</p> <p>Methods</p> <p>A systematic method of literature searching and selection was employed with searches limited to December 2006 to March 2009. Included studies were quality assessed using National Health and Medical Research Council (NHMRC) diagnostic levels of evidence and a modified Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. Individual and pooled diagnostic performance measures were calculated using standard meta-analytic techniques at the patient, vessel and segment level. A positive result was defined as greater than or equal to 50% stenosis.</p> <p>Results</p> <p>Twenty-eight studies were included in the systematic review examining 3,674 patients. The primary meta-analysis at the patient-level indicated a sensitivity of 98.2% and specificity of 81.6%. The median (range) positive predictive value (PPV) was 90.5% (76%-100%) and negative predictive value (NPV) 99.0% (83%-100%). In all vessels, the pooled sensitivity was 94.9%, specificity 89.5%, and median (range) PPV 75.0% (53%-95%) and NPV 99.0% (93%-100%). At the individual artery level, overall diagnostic accuracy appeared to be slightly higher in the left main coronary artery and slightly lower in the left anterior descending and circumflex artery. In all segments, the sensitivity was 91.3%, specificity 94.0% and median (range) PPV 69.0% (44%-86%) and NPV 99.0% (98%-100%).</p> <p>Conclusions</p> <p>The high sensitivity indicates that CTA can effectively identify the majority of patients with significant coronary artery stenosis. The high NPV at the patient, vessel and segment level establishes CTA as an effective non-invasive alternative to invasive coronary angiography (ICA) for the exclusion of stenosis.</p

Non-invasive or minimally invasive autopsy compared to conventional autopsy of suspected natural deaths in adults: a systematic review

Objectives: Autopsies are used for healthcare quality control and improving medical knowledge. Because autopsy rates are declining worldwide, various non-invasive or minimally invasive autopsy methods are now being developed. To investigate whether these might replace the invasive autopsies conventionally performed in naturally deceased adults, we systematically reviewed original prospective validation studies. Materials and methods: We searched six databases. Two reviewers independently selected articles and extracted data. Methods and patient groups were too heterogeneous for meaningful meta-analysis of outcomes. Results: Sixteen of 1538 articles met our inclusion criteria. Eight studies used a blinded comparison; ten included less than 30 appropriate cases. Thirteen studies used radiological imaging (seven dealt solely with non-invasive procedures), two thoracoscopy and laparoscopy, and one sampling without imaging. Combining CT and MR was the best non-invasive method (agreement for cause of death: 70 %, 95%CI: 62.6; 76.4), but minimally invasive methods surpassed non-invasive methods. The highest sensitivity for cause of death (90.9 %, 95%CI: 74.5; 97.6, suspected duplicates excluded) was achieved in recent studies combining CT, CT-angiography and biopsies. Conclusion: Minimally invasive autopsies including biopsies performed best. To establish a feasible alternative to conventional autopsy and to increase consent to post-mortem investigations, further research in larger study groups is needed. Key points: • Health care quality control benefits from clinical feedback provided by (alternative) autopsies. • So far, sixteen studies investigated alternative autopsy methods for naturally deceased adults. • Thirteen studies used radiological imaging modalities, eight tissue biopsies, and three CT-angiography. • Combined CT, CT-angiography and biopsies were most sensitive diagnosing cause of death

Optimal phase for coronary interpretations and correlation of ejection fraction using late-diastole and end-diastole imaging in cardiac computed tomography angiography: implications for prospective triggering

A typical acquisition protocol for multi-row detector computed tomography (MDCT) angiography is to obtain all phases of the cardiac cycle, allowing calculation of ejection fraction (EF) simultaneously with plaque burden. New MDCT protocols scanner, designed to reduce radiation, use prospectively acquired ECG gated image acquisition to obtain images at certain specific phases of the cardiac cycle with least coronary artery motion. These protocols do not we allow acquisition of functional data which involves measurement of ejection fraction requiring end-systolic and end-diastolic phases. We aimed to quantitatively identify the cardiac cycle phase that produced the optimal images as well as aimed to evaluate, if obtaining only 35% (end-systole) and 75% (as a surrogate for end-diastole) would be similar to obtaining the full cardiac cycle and calculating end diastolic volumes (EDV) and EF from the 35th and 95th percentile images. 1,085 patients with no history of coronary artery disease were included; 10 images separated by 10% of R–R interval were retrospectively constructed. Images with motion in the mid portion of RCA were graded from 1 to 3; with ‘1’ being no motion, ‘2’ if 0 to <1 mm motion, and ‘3’ if there is >1 mm motion and/or non-interpretable study. In a subgroup of 216 patients with EF > 50%, we measured left ventricular (LV) volumes in the 10 phases, and used those obtained during 25, 35, 75 and 95% phase to calculate the EF for each patient. The average heart rate (HR) for our patient group was 56.5 ± 8.4 (range 33–140). The distribution of image quality at all heart rates was 958 (88.3%) in Grade 1, 113 (10.42%) in Grade 2 and 14 (1.29%) in Grade 3 images. The area under the curve for optimum image quality (Grade 1 or 2) in patients with HR > 60 bpm for phase 75% was 0.77 ± 0.04 [95% CI: 0.61–0.87], while for similar heart rates the area under the curve for phases 75 + 65 + 55 + 45% combined was 0.92 ± 0.02. LV volume at 75% phase was strongly correlated with EDV (LV volume at 95% phase) (r = 0.970, P < 0.001). There was also a strong correlation between LVEF (75_35) and LVEF (95_35) (r = 0.93, P < 0.001). Subsequently, we developed a formula to correct for the decrement in LVEF using 35–75% phase: LVEF (95_35) = 0.783 × LVEF (75_35) + 20.68; adjusted R2 = 0.874, P < 0.001. Using 64 MDCT scanners, in order to acquire >90% interpretable studies, if HR < 60 bpm 75% phase of RR interval provides optimal images; while for HR > 60 analysis of images in 4 phases (75, 35, 45 and 55%) is needed. Our data demonstrates that LVEF can be predicted with reasonable accuracy by using data acquired in phases 35 and 75% of the R–R interval. Future prospective acquisition that obtains two phases (35 and 75%) will allow for motion free images of the coronary arteries and EF estimates in over 90% of patients

A Combined–System Simulator for Mechatronic Systems

We discuss the development of a new algorithm for simulation of combined systems, that controls the traditional numerical integration process, such that time events and state events are handled efficiently and accurately. The algorithm is generic, i.e. independent of the used integration method. Furthermore, a new algorithm is developed to sort the equations automatically into four sections (static, initial, dynamic and output), to obtain a simulation model as fast as possible. Tests with a 6DOF robot model showed that the distribution of the equations among categories resulted in a performance increase of 4x. The more structured design using Object Oriented techniques, enables a structured and straightforward implementation of the simulator, resulting in a performance increase of 3x using the Van der Pol equation as a test case

1997], Improving dynamic system model building through constraints, submitted to

An important step in model building that has been given little attention is the formulation of consistent initial state – and parameter vectors. In this paper we motivate that indeed this step is error prone. Improvement is obtained by incorporating in the model ‘static relations ’ that limit the freedom in choosing values for the initial state – and parameter vectors. Such relations should be implemented by means of constraints. A prototype realisation in 20-sim is described