Objective measurements of image quality

Abstract

Abstract:Tissue harmonic imaging (THI) and compound imaging have been reported clinically to improve contrast resolution, tissue differentiation and overall image quality.However, there have been limited studies to date to quantify objectively the improvements in image quality achieved with these new imaging techniques. The aim of this study was to quantify differences in image quality which exist between conventional Bmode imaging, harmonic imaging, compound imaging and harmonic compound imaging. An ATL HDI 5000 scanner with three probes (C52, L74 and L125) was tested with two different types of test object, the GammexRMI model 404 GS LE and the GammexRMI 403 GS LE. The measurement limitations associated with subjective analysis methods were not present in this study, since an automated image analysis program was used to determine the image quality parameters therefore, subtle differences between the four imaging modes could be detected. Significant improvements in lateral resolution and slice thickness as a function of depth were found with THI. Contrast resolution and anechoic target detection improved with compound imaging, while harmonic compound imaging improved lateral resolution, slice thickness as a function of depth and contrast resolution. (Email: Jacinta.browne@northglasgow.scot.nhs.uk) 2

Investigation of the effect of subcutaneous fat on image quality performance of 2D conventional imaging and tissue harmonic imaging

“…An ex vivo subcutaneous pig fat layer was used to replicate beam distortion and phase aberration seen clinically in the presence of subcutaneous fat. Three different types of fat mimicking layers (olive oil, lard and lard with fish oil capsules) were evaluated.The subcutaneous pig fat layer demonstrated an improvement in anechoic target 3 detection with THI compared with 2D conventional imaging, but no improvement was demonstrated in contrast resolution performance; a similar result was found in a previous study conducted by this research group (Browne et al 2004) while using this tissue mimicking phantom without a fat layer. Similarly, while using the layers of olive oil, lard and lard with fish oil capsules, improvements due to THI were found in anechoic target detection but, again, no improvements were found for contrast resolution for any of the layer combinations.…”

“…However, a study carried out previously by the authors (Browne et al 2004) found improvements only in spatial resolution and not in contrast resolution or anechoic target detection.…”

“…However, a study carried out previously by the authors (Browne et al 2004) found improvements only in spatial resolution and not in contrast resolution or anechoic target detection.This result may have been due to the homogeneity of the phantom. Biological tissues are generally inhomogeneous and THI has been reported to improve image quality in the presence of large amounts of subcutaneous fat.…”

“…All of these give rise to the reported improvements in contrast resolution and lateral resolution in THI images compared with fundamental mode images (Averkiou et al 1997; Christopher 1997; Desser and Jeffrey 2001; Li and Zagzebski 2000; Tranquart et al 1999; Ward et al 1997. Despite these clinical studies being conducted to evaluate the improvements in image quality, there have been limited technical evaluations to provide quantitative information about the improvements in image quality with THI (Browne et al 2004). In a previous study, the authors of this paper investigated the imaging performance of compound imaging, tissue harmonic imaging and harmonic compound imaging compared with 2D conventional imaging (Browne et al 2004) and improvements were found for axial and lateral resolution and slice thickness, with no improvements in anechoic target detection or contrast resolution performance being detected with tissue harmonic imaging and improvements in contrast resolution and anechoic target detection with compound imaging and harmonic compound imaging.…”

Method for automatic detection of defective ultrasound linear array transducers based on uniformity assessment of clinical images — A case study

“…There are many methods and recommendations on how to carry out performance tests and quality control on ultrasound systems 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. The transducer is a vital part of the system and handled daily.…”