Performance assessment of four 64-slice computed tomographic devices for a typical clinical protocol.

OBJECTIVE: To compare the performances of four 64-slice CT devices, as regards radiation dose and image quality. METHODS: Effective dose was measured with thermoluminescent dosimeters in an Alderson Rando phantom (Alderson Research Laboratories, New York, NY). Quantitative image quality was evaluated in a Catphan 600 phantom (The Phantom Laboratory, New York, NY) using 3 parameters (modulation transfer function, contrast-to-noise ratio, and figure of merit). Effective and main organ doses were measured in 40 patients (10 for each CT device), who underwent an abdominal study with the same standard protocol; moreover, in these patients, clinical image quality, using a 5-grade quality score, was assessed. RESULTS: In-phantom measured doses and quantitative image quality showed some differences among the 4 devices. On the contrary, effective and organ doses provided to the patients were similar; no statistically significant differences were found also for clinical image quality. CONCLUSIONS: Some differences were found among the 4 devices from a physical point of view; on the other hand, the patient data were similar.

Functional magnetic resonance imaging: comparison between activation maps and computation pipelines in a clinical context.

In this study new evaluation strategies for comparing different Statistical Parametric Maps computed from fMRI time-series analysis software tools are proposed. The aim of our work is to assess and quantitatively evaluate the statistical agreement of activation maps. Some pre-processing steps are necessary to compare SPMs (Statistical Parametric Maps), including segmentation and co-registration. The study of the statistical agreement is carried out following two ways. The first way considers SPMs as the result of two classification processes and extracts confusion matrix and Cohen's kappa index to assess agreement. Some considerations will be made on the statistical dependence of classes and a new formulation of kappa index will be used for overcoming this problem. The second way considers SPMs as two 3D images, and computes the similarity of SPMs images with a fuzzy formulation of the Jaccard Index. Several experiments were conducted both to assess the performance of the proposed evaluation tools and to compare activation maps computation pipelines from two widely used software tools in a clinical context.