The Influence of Technical Factors on Sonoelastographic Assessment of Solid Breast Nodules

Zusammenfassung

Ziel: Ziel der Studie war die Bewertung des Einflusses technischer Parameter und/oder von Läsionscharakteristika auf den endgültigen Elastografie Score solider Mammaknoten. Material und Methoden: Eingeschlossen wurden Patientinnen mit soliden Brusttumoren die im Zeitraum von Mai 2007 bis Mai 2008 in der Radiologischen Abteilung der Universtity of Medicine and Pharmacy, Cluj-Napoca untersucht wurden. Alle Läsionen wurden mit konventionellen Ultraschall, Doppler Ultraschall und Sonoelastografie entsprechend einem voreingestellten Protokoll untersucht. Der Einfluss folgender Parameter auf den Elastografie Score wurde untersucht: Schnittbildrichtung (sagittal versus transversal); Größe der Region of Interest (klein versus groß), Amplitude und Frequenz der Bewegung; initiale Komprimierung (gering versus stark); Angulierung (senkrechte versus angulierte Sondenposition); Läsionscharakteristika (Größe und Lokalisation). Referenz war die histopathologische Diagnose und, in 20 Fällen, das Kurzzeit Follow-up. Ergebnisse: Zweiundneunzig Patientinnen mit einem mittleren Alter von 48,11 Jahren und 101 Mammaknoten wurden in die Studie eingeschlossen. Insgesamt lag die Sensitivität und die Spezifität der Elastografie bei 79 % [68 – 88 %] bzw. 79 % [65 – 89%] mit einem negativ prädiktiven Wert von 74 % [60 – 85 %] und einem positiv prädiktiven Wert von 84 % [72 – 91 %]. Die folgenden Parameter hatten keinen Einfluss auf den Elastografie Score: Schnittbildrichtung (Scores bei transversaler und longitudinaler Schnittrichtung, Z = -0,641, p = 0,552); die Amplitude und Frequenz der Bewegung während der elastografischen Untersuchung (Cochran's Q Konkordanz = 0,706, p = 0,872); starke initiale Komprimierung im Falle benigner Läsionen (Z = 0,000, p = 1,000); Größe der Läsion. Neun der elastografisch benignen Knoten waren falsch negativ und von 46 elastografisch malignen Knoten waren 12 falsch positiv. Die folgenden Parameter hatten Einfluss auf den Elastografie Score: Größe der Region of Interest (die Scores waren signifikant unterschiedlich bei der Auswahl großer im Vergleich zu kleinen Regions of Interest, Z = –0,671, p < 0,0001); Schallkopf Angulierung (Z = –5,42, p < 0,0001); starke initiale Komprimierung im Falle maligner Läsionen (Z = –6,044, p < 0,0001) und die Lokalisation der Läsion in der Nähe der Brustwand. Schlussfolgerung: Die wichtigsten Parameter, die den endgültigen Elastografie Score beeinflussen und zu falsch negativen Ergebnissen führen, sind die Größe der Region of Interest und die initiale Komprimierung und Angulierung des Schallkopfes. Dem entgegen hatten die Frequenz und die Amplitude der Bewegung während der Untersuchung keinen Einfluss auf das Ergebnis, so lange die Bildgebung zweckmäßig durchgeführt wurde. Änderung der Schallparameter führte bei malignen Mammaläsionen nie zu falsch positiven Ergebnissen.

Abstract

Purpose: The aim of the study was to assess the influence of technical factors and/or lesion characteristics on the final elastographic score in solid breast nodules. Materials and Methods: Patients with solid breast masses examined between May 2007 and May 2008 in the Radiology Department of Cluj District University Hospital were included in the study. All lesions were examined with conventional ultrasound, Doppler ultrasound and sonoelastography, according to a preset protocol. The influence of the following factors on the elastographic score was evaluated: type of section (sagittal versus transverse); size of region of interest (small versus large); amplitude and frequency of movement; initial compression (light versus strong); angulation (perpendicular versus angulated transducer); characteristics of the lesion (size and location). The reference diagnosis was the histopathology diagnosis and, in twenty cases, short-term follow-up. Results: Ninety-two patients with a mean age of 48.11 years and 101 breast nodules were included in the study. The overall sensitivity and specificity for elastography were 79 % [68–88 %] and 79 % [65 – 89 %], respectively, with a negative predictive value of 74 % [60–85 %] and a positive predictive value of 84 % [72–91 %]. The following factors did not influence the elastographic score: type of section (scores on transverse and longitudinal section, Z = –0.641, p = 0.552); the amplitude and frequency of movements during the elastographic examination (Cochran’s Q concordance = 0.706, p = 0.872); strong initial compression in the case of benign nodules (Z = 0.000, p = 1.000); size of the lesions. Of the elastographically benign nodules, 9 were false negative and of the 46 elastographically malignant nodules, 12 were false positive. The following factors influenced the elastographic scores: size of the region of interest (the scores were significantly different when small or large region of interest was used, Z = –0.671, p < 0.0001); transducer angulation (Z = –5.42, p < 0.0001); strong initial compression in the case of malignant nodules (Z = –6.044, p < 0.0001) and the location of the mass in the vicinity of the chest wall. Conclusion: The most important factors that influence the final elastographic score, leading to false negative results, are the size of the region of interest, the initial compression and angulation of the transducer, while the frequency and amplitude of movement during the examination proved to be of no importance as long as the images were obtained within a range of assessment usefulness. Changing the scanning parameters never led to false positive results in the case of malignant breast masses.

Key words

breast - ultrasound - artifacts - technical aspects

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