Abstract
Purpose
This study was undertaken to assess the agreement of computed tomography (CT) pelvimetry with different postprocessing techniques.
Materials and methods
CT data sets of 25 patients were retrospectively analysed. There were no CT examinations performed solely for pelvimetry, and there was no radiation exposure for study purposes. Six pelvimetric measurements were obtained by two independent observers in four data sets of each patient, i.e. on biplanar topograms, multiplanar reconstructions of 1-mm slices, volume-rendered images of the same data and volume-rendered images based on 5-mm-thick images. Interobserver agreement and variability were determined by Bland-Altman analysis. A human skeleton was also scanned and measured with the same techniques and by ruler as reference.
Results
With a correlation coefficient of 0.98, interobserver agreement was best for assessing 3D volume-rendered images reconstructed from 1-mm-thick slices. Interobserver variability was very good for sagittal outlet and midpelvic diameter, transverse inlet diameter and obstetric conjugate (correlation coefficients 0.96–0.99) but limited for intertuberous and interspinous distance. CT and ruler measurements of the skeleton showed excellent agreement.
Conclusions
Pelvimetry can be obtained with low interobserver variability on 3D volume-rendered CT reconstructions. Thus, CT pelvimetry is suitable to gain exact knowledge of pelvic anatomy to identify relevant parameters for dystocia in retrospective studies.
Abstract
Obiettivo
Valutare la concordanza della pelvimetria-TC con differenti tecniche di post-processing.
Materiali e metodi
Sono stati analizzati retrospettivamente i dati TC di 25 pazienti. Non c’erano esami TC eseguiti esclusivamente per la pelvimetria, e non c’è stata esposizione alle radiazioni a soli fini di studio. Sono state ottenute 6 misurazioni pelvimetriche da due osservatori indipendenti in quattro data sets per ogni paziente, cioè topogrammi in due proiezioni, ricostruzioni multiplanari con scansioni dello spessore di 1 mm, immagini volumetriche degli stessi dati ed immagini volumetriche basate su scansioni dello spessore di 5 mm. La variabilità e la concordanza interosservatore sono state determinate secondo l’analisi Bland-Altman. E’ stato analizzato e misurato con le stesse tecniche anche uno scheletro umano ed è stato preso come modello di riferimento.
Risultati
Con un coefficiente di correlazione di 0,98, la concordanza tra gli osservatori è stata migliore nella valutazione delle immagini volumetriche tridimensionali ricostruite da scansioni dello spessore di 1 mm. La variabilità interosservatore è stata molto buona per il diametro sagittale esterno e per il diametro intermedio della pelvi, per il diametro dell’inserzione trasversa e per la coniugata ostetrica (coefficiente di correlazione 0,96–0,99), ma limitata per la distanza tra le tuberosità e tra le spine ischiatiche. C’è stata una concordanza eccellente tra la TC e le misurazioni dello scheletro.
Conclusioni
La pelvimetria può essere ottenuta con una bassa variabilità interosservatore su ricostruzioni TC volumetriche tridimensionali. Pertanto, la pelvimetria-TC è adatta ad acquisire l’esatta conoscenza dell’anatomia pelvica per identificare i parametri rilevanti per distocia negli studi retrospettivi.
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Lenhard, M., Johnson, T., Weckbach, S. et al. Three-dimensional pelvimetry by computed tomography. Radiol med 114, 827–834 (2009). https://doi.org/10.1007/s11547-009-0390-x
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DOI: https://doi.org/10.1007/s11547-009-0390-x