Page 88 - Ultrasonography in Prehospital and Emergency Medicine - Rein Ketelaars
P. 88

                 86
Chapter 3
Discussion
In this study we found no difference in the diagnostic performance of the linear-array, curved-array, and phased-array transducer. The diagnostic performance was very good: sensi- tivity, specificity, PPV, and NPV were all between 96.4% and 98.8%. The observers needed an additional 0.51 seconds to reach a final diagnosis with the phased-array transducer compared to the linear-array transducer. A final diagnosis was reached much faster when lung sliding was present regardless of the transducer type.
The image quality scored by the observers on a 1–5 scale was significantly different between all three transducers; the linear-array transducer achieved the best scores, the phased-array transducer the worst. Moreover, the image quality was too bad to reach a diagnosis in eight phased-array transducer clips and two linear-array transducer clips.
These findings suggest that the actual diagnostic performance of the three transducers for pneumothorax is comparable. However, these experienced observers perceived the best im- age quality and needed the least amount of time when they judged the linear-array transduc- er clips. Based on these findings the linear-array transducer might qualify as the preferred transducer for lung ultrasonography. However, the transducer choice may depend on more important factors such as the intended gamut of indications US is used for and whether the machine will be equipped with one or more transducers. In a single transducer setup, the best choice is probably a curved-array or a phased-array transducer to be able to evaluate both the abdomen and pericardium, in addition to the chest.
To our knowledge, there are no studies that have compared US transducers for diagnosing pneumothorax in a similar study design.
In a study with a comparable design, but not focused on pneumothorax, the authors com- pared a 10–5 MHz and a 14–5 MHz linear-array transducer for a wide array of emergency department point-of-care ultrasound indications.15 However, lung ultrasonography was dis- cussed only briefly. Overall, their observers most frequently preferred the 10–5 MHz trans- ducer over the 14–5 MHz transducer.
In another study, the investigators compared a 5–10 MHz linear-array and a 1–5 MHz phased-array sector transducer in 55 patients scheduled for a thoracic computed tomog- raphy (CT) scan.16 The authors evaluated the diagnostic performance for pneumothorax, pleural effusion, consolidation, and interstitial syndrome. In six patients with a pneumotho- rax, confirmed with CT, they found that the linear-array transducer performed best with a
  

























































































   86   87   88   89   90