Abstract and Introduction
Abstract
The aim of this review is to provide clinicians and technicians with an overview of the development of CT protocols in lung cancer screening. CT protocols have evolved from pre-fixed settings in early lung cancer screening studies starting in 2004 towards automatic optimized settings in current international guidelines. The acquisition protocols of large lung cancer screening studies and guidelines are summarized. Radiation dose may vary considerably between CT protocols, but has reduced gradually over the years. Ultra-low dose acquisition can be achieved by applying latest dose reduction techniques. The use of low tube current or tin-filter in combination with iterative reconstruction allow to reduce the radiation dose to a submilliSievert level. However, one should be cautious in reducing the radiation dose to ultra-low dose settings since performed studies lacked generalizability. Continuous efforts are made by international radiology organizations to streamline the CT data acquisition and image quality assurance and to keep track of new developments in CT lung cancer screening. Examples like computer-aided diagnosis and radiomic feature extraction are discussed and current limitations are outlined. Deep learning-based solutions in post-processing of CT images are provided. Finally, future perspectives and recommendations are provided for lung cancer screening CT protocols.
Introduction
A growing number of countries is implementing lung cancer screening programs or are at the forefront of starting with research implementation studies.[1–7] The National Lung Screening trial (NLST, USA) and the Nederlands-Leuvens Longkanker Screenings Onderzoek (NELSON) trial have shown that lung cancer mortality can be reduced with at least 20% with lung cancer CT screening in high risk individuals meeting eligibility criteria.[8,9] Current lung cancer screening protocols recommend repeated screening at either annual or biannual frequency for eligible individuals.[10,11] On an individual level this may result in over 25 scans over a lifetime with in practice widely varying cumulative radiation dose.[12,13] Consequently, the estimates for induced cancer risk by repeated screening for an entire population vary as well depending on the used CT protocol, CT generation and expertise of institutions to optimize CT protocols.[12–15] The aim of this review is to provide clinicians with an overview of the development of the CT protocol for lung cancer screening, the current protocol recommendations and radiation dose reduction possibilities in lung cancer CT screening.