Assembling 3D histology volumes from sections of cancerous lymph nodes to match 3D high-frequency quantitative ultrasound images

Abstract

High-Frequency Quantitative Ultrasound (HFQUS) imaging methods are under investigation to evaluate their ability to detect small metastases (<; 2 mm) in lymph nodes freshly dissected from cancer patients. To assess the performance of these methods, 3D HFQUS must be compared to gold-standard histologic images. Histologic images have to be assembled to form volumetric histologic information. This study addresses this issue. The acquisition of high-frequency ultrasound (HFU) data with a 26-MHz center-frequency transducer and histologic preparation are described. Dissected nodes were longitudinally cut in half and pairs of histologic sections separated by 65 μm, for nodes <; 5 mm, or 115 μm, for nodes >; 5 mm, were photographed. Then a fully automatic method to assemble and orient a 3D histologic volume from a set of 2D images was developed and applied. Identification of the histology sections on each slide relies on a parametric shape modeling of the histologic sections with ellipses. Then a set of rigid transformations were estimated and applied to construct volumetric histologic data. The method was visually evaluated on a set of 50 lymph nodes and is valuable for comparing histologic data to HFQUS estimates in 3D.