ABSTRACT
PURPOSE: To perform qualitative and quantitative evaluation of low-monoenergetic images (50 KeV) compared with conventional images (120 kVp) in pulmonary embolism (PE) studies and to determine the extent and clinical relevance of these differences as well as radiologists' preferences. MATERIALS AND METHODS: One hundred fifty CT examinations for PE detection conducted on a single-source dual-energy CT were retrospectively evaluated. Attenuation, contrast-to-noise-ratio, and signal-to-noise-ratio were obtained in a total of 8 individual pulmonary arteries on each exam-including both central (450/1200=37.5%) and peripheral (750/1200=62.5%) locations. Results were compared between the conventional and low-monoenergetic images. For quality assessment, 41 images containing PE were presented side-by-side as pairs of slices in both conventional and monoenergetic modes and evaluated for ease in embolus detection by 9 radiologists: cardiothoracic specialists (3), noncardiothoracic specialists (3), and residents (3). Paired samples t tests, a-parametric Wilcoxon test, McNemar test, and kappa statistics were performed. RESULTS: Monoenergetic images had an overall statistically significant increased average ratio of 2.09 to 2.26 ( P <0.05) for each measured vessel attenuation, with an increase in signal-to-noise ratio (23.82±9.29 vs. 11.39±3.2) and contrast-to-noise ratio (17.17±6.7 vs 7.27±2.52) ( P <0.05). Moreover, 10/150 (6%) of central pulmonary artery measurements considered suboptimal on conventional mode were considered diagnostic on the monoenergetic images (181±14.6 vs. 387.7±72.4 HU respectively, P <0.05). In the subjective evaluation, noncardiothoracic radiologists showed a preference towards low-monoenergetic images, whereas cardiothoracic radiologists did not (74.4% vs. 57.7%, respectively, P <0.05). CONCLUSIONS: The SNR and CNR increase on monoenergetic images may have clinical significance particularly in the setting of sub-optimal PE studies. Noncardiothoracic radiologists and residents prefer low monoenergetic images.
Subject(s)
Pulmonary Artery , Pulmonary Embolism , Radiography, Dual-Energy Scanned Projection , Humans , Pulmonary Artery/diagnostic imaging , Female , Pulmonary Embolism/diagnostic imaging , Retrospective Studies , Male , Middle Aged , Aged , Adult , Radiography, Dual-Energy Scanned Projection/methods , Computed Tomography Angiography/methods , Aged, 80 and over , Tomography, X-Ray Computed/methods , Signal-To-Noise Ratio , Radiographic Image Interpretation, Computer-Assisted/methods , Reproducibility of Results , Observer VariationABSTRACT
In recent years, advances in molecular biology and cancer research have led to the identification of sensitive and specific biomarkers that associate with various types of cancer. However, in vivo cancer detection methods with computed tomography, based on tracing and detection of these molecular cancer markers, are unavailable today. This paper demonstrates in vivo the feasibility of cancer diagnosis based on molecular markers rather than on anatomical structures, using clinical computed tomography. Anti-epidermal growth factor receptor conjugated gold nanoparticles (30 nm) were intravenously injected into nude mice implanted with human squamous cell carcinoma head and neck cancer. The results clearly demonstrate that a small tumor, which is currently undetectable through anatomical computed tomography, is enhanced and becomes clearly visible by the molecularly-targeted gold nanoparticles. It is further shown that active tumor targeting is more efficient and specific than passive targeting. This noninvasive and nonionizing molecular cancer imaging tool can facilitate early cancer detection and can provide researchers with a new technique to investigate in vivo the expression and activity of cancer-related biomarkers and molecular processes.
