title: Thoracoscopic ultrasonography for localization of subcentimetre lung nodules.
abstract: OBJECTIVE
  Localization of small, non-visible and non-palpable subcentimetre nodules can be challenging during video-assisted thoracoscopic surgery (VATS). Intraoperative ultrasonography is an option for localization of such lesions, yet this technology has not been fully adapted to thoracic surgery. The objective of this study was to assess a newly developed thoracoscopic ultrasound for localization and biopsy of subcentimetre pulmonary nodules in animal models.
  
  
  METHODS
  A prototype convex probe ultrasound thoracoscope (XLTF-UC180, Olympus Medical Systems Corp.) was used in this study. Multiple 5% agar pseudo-tumours were created in porcine lungs (n = 10) and assessed for localization with different frequencies (5.0-12.0 MHz) in deflated lungs. The evaluated pseudo-tumours were divided into two groups based on the distinctness of the tumour margin on the ultrasound images and compared in terms of the size and depth of the tumours. The visualization of real tumours and the biopsy capability were assessed using rabbit VX2 lung tumour models (n = 7).
  
  
  RESULTS
  The thoracoscopic ultrasound clearly visualized normal lung structures within a 1.5-cm depth including small vessels and bronchioles less than 5 mm in diameter in the completely deflated lung. Twenty-eight of 30 agar pseudo-tumours (93.3%) were successfully detected in deflated lungs (average size: 8.5 ± 2.1 mm; average depth: 7.4 ± 7.5 mm and depth range: 0-24.8 mm). Two tumours were not detected due to residual air surrounding the tumour. Higher frequency (12 MHz) tended to show more distinct margins of the targets. Indistinct tumours were located significantly deeper in the lung than the distinct tumours (14.11vs 2.42 mm), regardless of them being in a similar size range. VX2 tumours were identified as heterogeneous isoechoic lesions and adequate tissue sampling for diagnosis was achieved using a dedicated needle.
  
  
  CONCLUSIONS
  The newly developed convex probe ultrasound thoracoscope was capable of localizing subcentimetre nodules in the porcine deflated lung as well as of obtaining sufficient sampling from lung tumours in the rabbit model, which may enable single-port VATS lung nodule biopsy in a human clinical setting. However, the depth of the tumours significantly influenced the quality of ultrasound images. Complete collapse of the lung and use of high frequency may facilitate achieving distinct visualization of the targets.
authors: Division of Thoracic Surgery, Toronto General Hospital, University Health Network, Toronto, Canada Department of General Thoracic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Hironobu
authors: H
authors: Wada
authors: Division of Thoracic Surgery, Toronto General Hospital, University Health Network, Toronto, Canada.
authors: Takashi
authors: T
authors: Anayama
authors: Division of Thoracic Surgery, Toronto General Hospital, University Health Network, Toronto, Canada.
authors: Kentaro
authors: K
authors: Hirohashi
authors: Division of Thoracic Surgery, Toronto General Hospital, University Health Network, Toronto, Canada Department of General Thoracic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Takahiro
authors: T
authors: Nakajima
authors: Division of Thoracic Surgery, Toronto General Hospital, University Health Network, Toronto, Canada.
authors: Tatsuya
authors: T
authors: Kato
authors: Division of Thoracic Surgery, Toronto General Hospital, University Health Network, Toronto, Canada.
authors: Thomas K
authors: TK
authors: Waddell
authors: Division of Thoracic Surgery, Toronto General Hospital, University Health Network, Toronto, Canada.
authors: Shaf
authors: S
authors: Keshavjee
authors: Department of General Thoracic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan.
authors: Ichiro
authors: I
authors: Yoshino
authors: Division of Thoracic Surgery, Toronto General Hospital, University Health Network, Toronto, Canada kazuhiro.yasufuku@uhn.ca.
authors: Kazuhiro
authors: K
authors: Yasufuku
mesh_terms: D000818:Animals; D001706:Biopsy; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D011013:Pneumonectomy / Q000295:instrumentation / Q000379:methods*; D011817:Rabbits; D013552:Swine; D020775:Thoracic Surgery, Video-Assisted / Q000295:instrumentation / Q000379:methods*; D020708:Thoracoscopes; D018084:Ultrasonography, Interventional / Q000295:instrumentation / Q000379:methods*
keywords: Imaging; Lung wedge resection; Surgical equipment; Thoracoscopy/VATS; Ultrasound