Korean J Radiol.  2010 Jun;11(3):320-326. 10.3348/kjr.2010.11.3.320.

Dual-Energy Subtraction Imaging for Diagnosing Vocal Cord Paralysis with Flat Panel Detector Radiography

• Machida H
• Yoda K
• Arai Y
• Nishida S
• Masukawa A
• Asanuma M
• Yuhara T
• Morita S
• Suzuki K
• Ueno E
• Sabol JM

• KMID: 946272
• DOI: http://doi.org/10.3348/kjr.2010.11.3.320

Abstract

OBJECTIVE
To investigate the clinical feasibility of dual energy subtraction (DES) imaging to improve the delineation of the vocal cord and diagnostic accuracy of vocal cord paralysis as compared with the anterior-posterior view of flat panel detector (FPD) neck radiography. MATERIALS AND METHODS: For 122 consecutive patients who underwent both a flexible laryngoscopy and conventional/DES FPD radiography, three blinded readers retrospectively graded the radiographs during phonation and inspiration on a scale of 1 (poor) to 5 (excellent) for the delineation of the vocal cord, and in consensus, reviewed the diagnostic accuracy of vocal cord paralysis employing the laryngoscopy as the reference. We compared vocal cord delineation scores and accuracy of vocal cord paralysis diagnosis by both conventional and DES techniques using kappa statistics and assessing the area under the receiver operating characteristic curve (AUC). RESULTS: Vocal cord delineation scores by DES (mean, 4.2 +/- 0.4) were significantly higher than those by conventional imaging (mean, 3.3 +/- 0.5) (p < 0.0001). Sensitivity for diagnosing vocal cord paralysis by the conventional technique was 25%, whereas the specificity was 94%. Sensitivity by DES was 75%, whereas the specificity was 96%. The diagnostic accuracy by DES was significantly superior (kappa = 0.60, AUC = 0.909) to that by conventional technique (kappa = 0.18, AUC = 0.852) (p = 0.038). CONCLUSION: Dual energy subtraction is a superior method compared to the conventional FPD radiography for delineating the vocal cord and accurately diagnosing vocal cord paralysis.

Keyword

Dual energy subtraction; Flat panel detector radiography; Vocal cord delineation; Vocal cord paralysis

MeSH Terms

Absorptiometry, Photon/*instrumentation/*methods
Adolescent
Adult
Aged
Aged, 80 and over
Child
Child, Preschool
Feasibility Studies
Female
Humans
Male
Middle Aged
Observer Variation
Reproducibility of Results
Sensitivity and Specificity
Subtraction Technique
Vocal Cord Paralysis/*radiography
Vocal Cords/radiography
*X-Ray Intensifying Screens
Young Adult

Figure

• 

  Fig. 1 Mean delineation scale scores for readers of pyriform sinus, subglottis, and vocal cord on conventional and dual energy subtraction radiographs. Scale of delineation with dual energy subtraction was significantly higher than with conventional technique for all these anatomical sites (p < 0.0001). Left bar: conventional method; Right bar: dual energy subtraction method. Number shown in each bar graph represents mean delineation scale of each anatomy ± estimated error of mean.

• 

  Fig. 2 Receiver operating characteristic curves for diagnosis of vocal cord paralysis by conventional (left) and dual energy subtraction (right) radiographs. Area under receiver operating characteristic curve value is shown for each technique. Area under receiver operating curve value with dual energy subtraction was significantly higher than for conventional technique (p = 0.038). On these curves, 95% confidence intervals were plotted as dotted curves. AUC = area under receiver operating characteristic curve.

• 

  Fig. 3 75-year-old man with left vocal cord paralysis. Delineation of vocal cord with dual energy subtraction (all readers grade 5) was rated higher than by conventional technique (grades 2, 2, and 3) by three readers. Left vocal cord (arrows) was fixed more definitely at midline on soft-tissue only image during inspiration using dual energy subtraction method. DES = dual energy subtraction

• 

  Fig. 4 64-year-old woman with left vocal cord paralysis. Delineation of vocal cord by dual energy subtraction (all readers grade 5) was rated higher than by conventional technique (grades 4, 4, and 5) by three readers. Left vocal cord (arrows) was thinner and more pointed with loss of left subglottic arch compared to contralateral side and visualized more definitively on soft-tissue only image during inspiration using dual energy subtraction method. DES = dual energy subtraction

• 

  Fig. 5 71-year-old man without vocal cord paralysis. Right vocal cord appeared fixed at paramedian position on soft-tissue only image during inspiration using dual energy subtraction method. However, laryngoscope examination revealed no vocal cord paralysis. We regarded this patient as false positive case.

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  Fig. 6 78-year-old woman with right vocal cord paralysis. Soft-tissue only images using dual energy subtraction method could not lead to diagnosis of vocal cord paralysis. However, laryngoscope examination revealed right vocal cord paralysis. We regarded this patient as false negative case.

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