Quantitative Image Quality Measurements of a Digital Breast Tomosynthesis System

Abstract

Purpose: The aim of this study was to measure the image quality of a digital breast tomosynthesis (DBT) system quantitatively.

Materials and Methods: The signal transfer property (STP), modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of the Hologic Selenia Dimensions breast tomosynthesis system were measured according to established methods. The NPS was calculated from two-dimensional (2 D) fast Fourier transform (FFT) of flat field images. The presampling MTF of the system was determined for 2 D standard projection mammography and 3 D breast tomosynthesis mode using the edge method. The DQE was derived for different detector air kerma (DAK) values from NPS and MTF measurements.

Results: The detector response function was linear for both two-dimensional (2 D) standard projection mammography and three-dimensional (3 D) breast tomosynthesis modes. The gradient of the detector response in the 3 D imaging mode was higher than the gradient in the 2 D imaging mode by a factor of 3.1. The MTF values measured at the Nyquist frequency were 32 % and 39 % in 2 D and 3 D imaging modes, respectively. The DQE was saturated at an air kerma value approximately 3.5 times lower in 3 D mode than in 2 D mode. The measured maximum DQE value was 54 %.

Conclusion: The measured DQE values were comparable with breast tomosynthesis systems from other companies (Siemens, GE).

Citation Format:

• Olgar T, Kahn T, Gosch D. Quantitative Image Quality Measurements of a Digital Breast Tomosynthesis System. Fortschr Röntgenstr 2013; 185: 1188 – 1194

Zusammenfassung

Ziel: Das Ziel der Studie war die quantitative Messung der Bildqualität an einem Brusttomosynthesesystem.

Material und Methoden: Die Signalübertragungseigenschaften (STP), die Modulationsübertragungsfunktion (MTF), das Rauschspektrum (NPS) und die detektive Quantenausbeute (DQE) wurden nach etablierten Methoden an einem Brusttomosynthesesystem Selenia Dimensions von Hologic gemessen. Das NPS wurde mittels zweidimensionaler (2-D) schneller Fouriertransformation (FFT) aus Flatfieldbildern berechnet. Die presampling MTF des Systems wurde mittels der Kantenmethode für 2-D-Standardprojektionsaufnahmen und für den 3-D-Brusttomosynthesemodus ermittelt. Die DQE wurde für unterschiedliche Detektordosiswerte (DAK) aus den gemessenen NPS und MTF abgeleitet.

Ergebnisse: Die Detektorresponsfunktion war linear für die 2-D-Standardprojektionsaufnahmen und für den 3-D-Brusttomosynthesemodus. Der Gradient der Detektorrespons im 3-D-Aufnahmemodus war um den Faktor 3,1 höher als im 2-D-Aufnahmebetrieb. Die bei der Nyquist-Frequenz gemessenen MTF-Werte waren 32 % im 2-D-Modus und 39 % im 3-D-Modus. Die Sättigung der DQE im 3-D-Modus erfolgte bei Luftkermawerten, die um den Faktor 3,5 niedriger waren als im 2-D-Modus. Der gemessene maximale DQE-Wert lag bei 54 %.

Schlussfolgerung: Die gemessenen DQE-Werte waren vergleichbar mit denen von Brusttomosynthesesystemen anderer Hersteller (Siemens, GE).

Key words

image quality - detective quantum efficiency - digital breast tomosynthesis - modulation transfer function - noise power spectrum

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