May 9, 2014
Carbon nanotubes increase clinical breast imaging efficiency
Digital breast tomosynthesis (DBT) overcomes some of the limitations of digital mammography – the current gold standard for the early detection of breast cancer. Now, reporting in Nanotechnology, researchers have evaluated the use of carbon nanotube (CNT) cathodes in these systems and have not only increased the lifetime of the technology, but also decreased the time that is required to image patients.
DBT is a US FDA (Food and Drug Administration)-approved breast imaging modality that is gaining momentum as a competitor to two-dimensional (2D) radiography for breast-cancer screening. It is a quasi-three-dimensional (3D) modality that increases cancer detection rates by removing the effects of overlapping breast tissue. DBT acquires many X-ray projections over an angular range that are then reconstructed into a 3D image volume. This allows radiologists to scan the entire breast volume, leading to the visualization of more cancers and the proper diagnosis of those cancers.
Current DBT systems employ thermionic X-ray sources that must be physically rotated to acquire projection images. This leads to a loss of spatial resolution – crucial for properly detecting cancerous lesions – due to motion of the X-ray focal spot, gantry vibrations, and/or patient motion. The researchers have developed a stationary DBT (s-DBT) system employing field emission for X-ray production, which removes the need for tube motion (as reported in Qian et al. 2012 and Tucker et al. 2013). Removing tube motion increases the spatial resolution; further enhancing the cancer detection capabilities of the DBT modality.
Applying carbon nanotubes
The s-DBT technology has been made possible due to the field emission properties of CNTs. CNT-based X-ray source arrays have now been integrated into pre-clinical s-DBT systems. In this most recent study, the CNTs were rigorously tested for high-current capabilities, consistency, and the stability required for breast imaging tasks in a pre-clinical X-ray system.
The performance of the CNT emitters surpassed the requirements for DBT acquisition. They were further tested under conditions mimicking 2D mammography imaging. The performance of the CNT X-ray source array in the prototype s-DBT system was tracked over several years’ time. The system was put to use performing various breast imaging tasks and maintained stable operation conditions over that time, and continues to perform stably to this day.
A duplicate system has been installed at the North Carolina Cancer Hospital in Chapel Hill, NC, and is in use in a clinical trial. 100 patients will participate in this study – the results of which will hopefully support the screening and diagnostic power of DBT imaging, and illustrate the advantages of the s-DBT system in particular.
More information about the research can be found in the journal Nanotechnology 25 245704.
About the author
Emily Gidcumb is a materials science PhD student at the University of North Carolina at Chapel Hill (UNC-CH) working under the advisement of Dr Otto Zhou and Dr Jianping Lu. Her soon to be completed dissertation is titled “Performance of a carbon nanotube field emission X-ray source array for stationary digital breast tomosynthesis”, which focuses on the fabrication, development and characterization of the s-DBT prototype system.