AXIAL AND LATERAL RESOLUTION OF ROTATIONAL INTRAVASCULAR ULTRASOUND -IN-VITRO OBSERVATIONS AND DIAGNOSTIC IMPLICATIONS

Purpose: To determine the axial and lateral resolution of a rotating i ntravascular ultrasound system and the diagnostic implications for the diagnosis of early artherosclerosis. Methods: The resolution of a 20 MHz rotating transducer was tested in a specially designed high-resolu tion phantom and in five aortic autopsy specimens with varying degrees of early atherosclerosis. Results: The best lateral resolution is at the minimal distance between transducer and object. Measurements in th e wire phantom showed this to be better than 0.43 mm. This is less tha n the axial resolution which is better than 0.13 mm. Decreasing latera l resolution with increasing distance between transducer and object is manifested by arcing and overestimation of the extent of focal athero sclerotic lesions. Conclusion: Axial resolution is significantly bette r than lateral resolution. Rapid deterioration of lateral resolution a ffects the diagnostic ability to characterize the extent of early athe rosclerosis. Eccentric positioning of the transducer tip, particularly in larger vessels, will therefore influence diagnostic accuracy in vi vo.