Texture analysis in 177Lu SPECT phantom images: Statistical assessment of uniformity requirements using texture features.

The purpose of this study was to apply texture analysis (TA) to evaluate the uniformity of SPECT images reconstructed with the 3D Ordered Subsets Expectation Maximization (3D-OSEM) algorithm. For this purpose, a cylindrical homogeneous phantom filled with 177Lu was used and a total of 24 spherical volumes of interest (VOIs) were considered inside the phantom. The location of the VOIs was chosen in order to define two different configurations, i.e. gravity and radial configuration. The former configuration was used to investigate the uniformity of distribution of 177Lu inside the phantom, while the latter configuration was used to investigate the lack of uniformity from center towards edge of the images. For each VOI, the trend of different texture features considered as a function of 3D-OSEM updates was investigated in order to evaluate the influence of reconstruction parameters. TA was performed using CGITA software. The equality of the average texture feature trends in both spatial configurations was assumed as the null hypothesis and was tested by functional analysis of variance (fANOVA). With regard to the gravity configuration, no texture feature rejected the null hypothesis when the number of subsets increased. For the radial configuration, the statistical analysis revealed that, depending on the 3D-OSEM parameters used, a few texture features were capable of detecting the non-uniformity of 177Lu distribution inside the phantom moving from the center of the image towards its edge. Finally, cross-correlation coefficients were calculated to better identify the features that could play an important role in assessing quality assurance procedures performed on SPECT systems.

Myocardial perfusion imaging and risk classification for coronary heart disease in diabetic patients. The IDIS study: a prospective, multicentre trial.

PURPOSE: To determine whether stress-rest myocardial perfusion single-photon emission (MPS) computed tomography improves coronary heart disease (CHD) risk classification in diabetic patients. METHODS: In 822 consecutive diabetic patients, risk estimates for a CHD event were categorized as 0% to <3%, 3% to <5%, and ≥5% per year using Cox proportional hazards models. Model 1 used traditional CHD risk factors and electrocardiography (ECG) stress test data and model 2 used these variables plus MPS imaging data. We calculated the net reclassification improvement (NRI) and compared the distribution of risk using model 2 vs. model 1. CHD death, myocardial infarction and unstable angina requiring coronary revascularization were the outcome measures. RESULTS: During follow-up (58 ± 11 months), 148 events occurred. Model 2 improved risk prediction compared to model 1 (NRI 0.25, 95% confidence interval, CI, 0.15-0.34; p < 0.001). Overall, 301 patients were reclassified to a higher risk category, with an event rate of 28%, and 26 to a lower risk category, with an event rate of 15%. Among patients at 3% to <5% risk, 53% were reclassified at higher risk and 25% at lower risk (NRI 0.42, 95% CI 0.07-0.76; p < 0.05). The cost per NRI was $880.80 for MPS imaging as compared to an outpatient visit with an ECG stress test. CONCLUSION: The addition of MPS imaging data to a prediction model based on traditional risk factors and ECG stress test data significantly improved CHD risk classification in patients with diabetes.

Assessment of left ventricular volume and function by integration of simplified 3D echocardiography, tissue harmonic imaging and automated extraction of endocardial borders.

BACKGROUND: Quantitative three-dimensional echocardiography (3DEcho) of left ventricle (LV) is still limited because of the need for manually tracing endocardial borders: this can increase observer variability depending on the quality of fundamental (FUND) 2D images. We tested the combination of a simplified 3DEcho technique for LV reconstruction with automated endocardial border detection (Digital Echo Quantification, DEQ) and tissue harmonic imaging (THI) for enhancement of endocardium-cavity interface. METHODS: Twenty-five consecutive patients with ischaemic heart disease and dilated or distorted LV underwent 3DEcho and gated-SPECT nuclear examinations evaluating: (a) end-diastolic and end-systolic volumes (EDV, ESV); (b) ejection fraction (EF); (c) volume/time curve (VTC). Thereafter, 3DEcho was applied to 47 patients with acute myocardial infarction (AMI) at pre-discharge and 6 months to evaluate remodelling. RESULTS: Integrated 3DEcho values in THI modality were obtained in 84% of patients and correlated well with nuclear data for EDV (r = 0.95, mean difference = -2.2 +/- 15.8 ml), ESV (r = 0.98, mean difference = -3.5 +/- 10.2 ml), and EF (r = 0.82, mean difference = 0.6 +/- 6.4%; all mean differences NS vs. 0), with an interobserver variability of 4.9, 5.7 and 8.2% for EDV, ESV and EF respectively. Automated VTC by 3DEcho in THI modality reproduced well that obtained by nuclear technique (r = 0.96) and allowed recognition of LV remodelling in 36% of patients at 6 months. Integrated 3DEcho values in FUND modality were obtained only in 52% of patients and showed much higher errors and interobserver variability. CONCLUSIONS: THI permits accurate 3D reconstruction of LV borders detected by DEQ, allowing automated VTC throughout the cardiac cycle as well as study of LV remodelling.