Developing a Methodology for 3-D Correlation of PET-CT Images and Whole-Mount Histopathology in Non-Small Cell Lung Cancer

Max Dahele, David Hwang, Chris Peressotti, Laibao Sun, Maggie Kusano, Shaista Okhai, Gail Darling, Martin Yaffe, Curtis Caldwell, Kathy Mah, Jennifer Hornby, Lisa Ehrlich, Simon Raphael, Ming Tsao, Yee C. Ung, A. Behzadi, C. Weigensberg



Background:  Understanding the 3-dimensional (3-D), volumetric relationship between imaging and functional or histopathological heterogeneity of tumors is a key concept in the development of image-guided radiotherapy.  Our aim was to develop a methodological framework to enable the reconstruction of resected lung specimens containing non-small cell lung cancers (NSCLC), register them in 3-D with diagnostic imaging and import the reconstruction into a radiation treatment planning system.

  Methods and Results: 12 patients were recruited to investigate RPC in NSCLC. PET/CT imaging was obtained before resection. Resected specimens were formalin fixed for 1-24 hours prior to sectioning at 3-10 mm intervals. In order to try and retain their shape, the specimens were embedded in agar prior to sectioning. Consecutive sections were laid out for photographing and manually adjusted to maintain their shape. Following embedding the tissue blocks underwent 4mm thick whole-mount sectioning and staining with hematoxylin and eosin. Large histopathology slides were used to whole-mount entire sections for digitisation. The correct sequence was maintained to assist in subsequent reconstruction.

Using AdobeâPhotoshopâ, contours were placed on the photographic images to represent the external border of the section, and extent of macroscopic disease. Sections were stacked in sequence and manually orientated in Photoshopâ. The macroscopic tumor contours were then transferred to MATLABâ and stacked, resulting in 3-D surface renderings of the resected specimen and embedded gross tumor. In order to evaluate the microscopic extent of disease, customized ‘tile-based’ and commercial confocal panoramic laser scanning (TISSUEscopeä) systems were used to generate digital images of whole-mount histopathology sections. Using the digital whole-mount images and imaging software, the gross and the microscopic extent of disease were contoured.

Two methods of registering pathology and imaging were used. First, selected PET/CT images were transferred into Photoshopâ and contoured, stacked and reconstructed. After importing the pathology and imaging contours to MATLABâ they were reconstructed, manually rotated and rigidly registered. In the second method, MATLABâ tumor renderings were exported to a software platform enabling manual registration with the original PET/CT images in multiple planes. Data from this software platform were then exported to the Pinnacle radiation treatment planning system in DICOM format.

 Conclusions: There is no one definitive method for 3-dimensional volumetric RPC in NSCLC. An innovative approach to the 3-D reconstruction of resected NSCLC specimens, incorporates agar embedding of the specimen and whole-mount digital histopathology. The reconstructions can be rigidly and manually registered to imaging modalities like CT and PET and exported to a radiation treatment planning system.

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ISSN: 1198-0052 (Print) ISSN: 1718-7729 (Online)