[Dronedarone: a real innovation or a mere second-best choice? How to find the way among guidelines, regulatory agencies and daily clinical practice]. / Dronedarone: una reale innovazione o solo una valida seconda scelta? Come districarsi tra linee guida, agenzie regolatorie e pratica clinica quotidiana.

Dronedarone is the antiarrhythmic drug with the most complete and wide literature preceding its marketing. Most of these studies showed a good efficacy along with an excellent risk profile, especially in low- and medium-risk patients. Recently, updates of European, American and even Italian guidelines gave dronedarone its own spot into the antiarrhythmic armamentarium, recommending its use both for rhythm control and rate control in non-permanent atrial fibrillation. In Italy, however, dronedarone prescription is still possible only when amiodarone is not tolerated, making dronedarone a mere second choice of its older "relative". Moreover, patients taking dronedarone must undergo a strict alanine aminotransferase and bilirubin follow-up, which usefulness in predicting drug-induced liver damage (probably idiosyncratic in nature and therefore unpredictable) is far from demonstrated. The aim of this review is to sum up actual evidences on dronedarone, describe how these evidences had been differently transposed by panel of experts and drug agencies into guidelines and recommendations, and define the current difficulties encountered by the cardiologist in the correct use of this new antiarrhythmic agent in clinical practice.

Assessment of geometrical distortion and activity distribution after attenuation correction: A SPECT phantom study.

BACKGROUND: If single photon emission computed tomography (SPECT) images are reconstructed with filtered backprojection (FBP), not accounting for photon attenuation, artifacts can occur related to geometrical distortion and inaccurate estimation of regional distribution of radioactivity. By reconstructing the images with an iterative algorithm such as the maximum likelihood-expectation maximization (ML-EM) that incorporates the attenuation distribution information, it is possible to compensate for nonuniform attenuation. The aim of this study was to assess whether correction for nonuniform attenuation in SPECT can reduce the geometrical distortion and improve the activity quantitation. METHODS AND RESULTS: Three capillary sources containing the same amount of technetium 99m were imaged by a dual-headed SPECT system provided with two gadolinium 153 scanning transmission line sources, in nonuniform attenuation conditions. The images were reconstructed (1) with the use of FBP, (2) with the iterative ML-EM algorithm, and (3) with the iterative ML-EM algorithm incorporating attenuation maps. The geometrical distortion was estimated by comparing the spread that occurred in 2 orthogonal directions in the reconstructed transverse slices, expressed by full width at half maximum related to the x-axis and y-axis line spread functions. The accuracy of activity quantitation was analyzed by comparing the counts in regions of interest placed over the transverse slices of the 3 sources, located in different attenuating areas. The FBP-reconstructed slices showed a spread of image intensity toward the direction of minor attenuation; the source shape improved in the iterative ML-EM images, as well as in the iterative attenuation-corrected ML-EM images. The sources located deep in the phantom showed an apparent decrease in image intensity in both FBP and ML-EM images, which became less evident in the iterative attenuation-corrected ML-EM images. CONCLUSIONS: Image reconstruction with the iterative ML-EM algorithm, without the use of attenuation maps, can reduce geometrical distortion and eliminate streak artifacts, leading to an improvement in the object's shape and size, but does not reduce activity underestimation and inaccurate quantitation. In the iterative attenuation-corrected ML-EM images, there was a significant improvement in the accurate quantitation of activity distribution and a further reduction in geometrical distortion. In conclusion, nonisotropic attenuation correction with iterative ML-EM reduced the geometrical distortion of images and improved the accuracy of activity quantitation.