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1

The fidelity of compressed and interpolated medical images

Urbaniak Ilona Anna, Wolter Marcin

Technical Transactions

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2020

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Vol. 117, iss. 1

art. no. e2020031

EN

Due to the amount of medical image data being produced and transferred over networks, employing lossy compression has been accepted by worldwide regulatory bodies. As expected, increasing the degree of compression leads to decreasing image fidelity. The extent of allowable irreversible compression is dependent on the imaging modality and the nature of the image pathology as well as anatomy. Interpolation, which often causes image distortion, has been extensively used to rescale images during radiological diagnosis. This work attempts to assess the quality of medical images after the application of lossy compression followed by rescaling. This research proposes a fullreference objective measure of quality for medical images that considers their deterministic and statistical properties. Statistical features are acquired from the frequency domain of the signal and are combined with elements of the structural similarity index (SSIM). The aim is to construct a model that is specialized for medical images and that could serve as a predictor of quality.

PL

Obrazy medyczne umożliwiają specjalistom obserwację anatomii struktur oraz przebieg procesów fizjologicznych, które zachodzą w ludzkim ciele. Elektroniczna archiwizacja oraz możliwość cyfrowej komunikacji obrazów medycznych stały się niezwykle popularne w przemyśle systemów obrazowania medycznego. Dzięki nowoczesnym rozwiązaniom technologicznym możliwa jest zdalna diagnoza, szybszy dostęp do specjalisty, zdalne monitorowanie oraz ułatwiona komunikacja pomiędzy ośrodkami służby zdrowia. Limity szybkości sieci, eksplozja wzrostu technologicznego w dziedzinie modalności oraz ilość powstających, przetwarzanych i przesyłanych obrazów medycznych wpłynęła na rozważenie użycia metod nieodwracalnego kodowania w technologiach PACS przez światowe organy regulacyjne. Nieodwracalne kodowanie obrazów medycznych to między innymi kompresja i interpolacja oraz inne manipulacje obrazów. Zaletą użycia nieodwracalnego kodowania jest ulepszenie wydajności systemów poprzez zmniejszenie czasu przesłania oraz odtworzenia obrazu przez użytkownika. Kompromisem jest natomiast zmniejszona jakość obrazu. Niniejsze badania mają za zadanie zrozumienie i określenie efektów zaistniałych wskutek kompresji oraz interpolacji, które nieodwracalnie wpływają na jakość obrazów medycznych i mogą być zagrożeniem do prawidłowej diagnozy. Istotnym elementem badań jest zrozumienie efektów manipulacji obrazami wówczas, gdy obraz poddany jest kilku nieodwracalnym operacjom. W niniejszej pracy proponowany jest obiektywny miernik jakości obrazów medycznych, który oparty jest na deterministycznych i statystycznych właściwościach obrazów. Cechy statystyczne pochodzą z dziedziny częstotliwości Fouriera i są połączone z miernikiem Structural Similarity Index (SSIM). Proponowany model może być przydatny w ustaleniu wizualnych progów dla jakości obrazów medycznych, które są niezbędne do prawidłowej diagnozy medycznej.

2

Automatic detection of microcalcification based on morphological operations and structural similarity indices

Touil Asma, Kalti Karim, Conze Pierre-Henri, Solaiman Basel, Mahjoub Mohamed Ali

Biocybernetics and Biomedical Engineering

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2020

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Vol. 40, no. 3

1155--1173

EN

In this paper, a new method for automatic detection of microcalcifications in digitized mammograms is proposed. Based on mathematical morphology theory to deal with the problem of low contrast between microcalcifications and their surrounding pixels, it uses various structuring elements of different sizes to reduce the sensibility to microcalcification diversity sizes. The obtained morphological results are converted to a suspicion map based on an image quality assessment metric called structural similarity index (SSIM). This continuous map is, then, locally analyzed using superpixels to automatically estimate threshold values and finally detect potential microcalcification areas. The proposed method was evaluated using the publiclyavailable INBreast dataset. Experimental results show the benefits gained in terms of improving microcalcification detection performances compared to state-of-the-art methods.

3

Visual attention pooling and understanding the structural similarity index in multi-scale analysis

Bondzulic B. P., Petrovic V. S., Mitrovic S. T., Pavlovic B. Z., Andric M. S.

Optica Applicata

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2014

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Vol. 44, nr 2

267--283

EN

We present a novel spatial pooling strategy and the results of an extensive multi-scale analysis of the well-known structural similarity index metric (SSIM) for objective image quality evaluation. We show, in contrast with some previous studies, that even relatively simple perceptual importance pooling strategies can significantly improve objective metric performance evaluated as the correlation with subjective quality assessment. In particular, we define an attention and quality driven pooling mechanism that focuses structural comparisons within the SSIM model to only those pixels exhibiting significant structural degradations. We show that optimal objective metric performance is achieved over very sparse spatial domains indeed that ignore most of the signal data. We also investigate an explicit breakdown of the structural models within SSIM and show that in combination with the proposed attention and quality driven pooling some of these models represent well performing metrics in their own right, when applied at appropriate scale for which there may not be a single optimal value. Our experiments demonstrate that the augmented SSIM metric using the proposed pooling model provides performance advantage on an extensive LIVE dataset covering hundreds of degraded images and 5 different distortion types compared to both conventional SSIM and state-of-the-art objective quality metrics.

4

Digital image quality assessment using Structural Similarity index based on polynomial windows and transform-based measure using perceptually uniform colour spaces

Okarma K.

Poznan University of Technology Academic Journals. Electrical Engineering

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2009

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No 59

35-46

EN

In the paper the possibilities of using polynomial window functions for objective image quality assessment based on the Structural Similarity (SSIM) approach are considered as well as the usage of perceptually uniform colour spaces such as CIELAB and CIELUV for colour image quality assessment. The method of image quality assessment based on SSIM index is one of the latest techniques quite well correlated with the Human Visual System (HVS), but the proper choice of the window function plays an important role for the obtained results. The influence of the 2-D polynomial window properties on the values of SSIM index are investigated in the first part of the paper. Some other recently presented full-reference transform-based image quality assessment metrics utilising DFT, DCT and DWT transforms as well as SVD-based measure are typically used only for luminance channel of the image calculated according to YUV or YIQ colour models. In the second part of this paper some extension possibilities of such measures in purpose to determine the quality of colour images with better correlation to Human Visual System (HVS) are presented.