Chest tomosynthesis: Technical principles and clinical update

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Abstract

Digital tomosynthesis is a radiographic technique that can produce an arbitrary number of section images of a patient from a single pass of the X-ray tube. It utilizes a conventional X-ray tube, a flat-panel detector, a computer-controlled tube mover, and special reconstruction algorithms to produce section images. While it does not have the depth resolution of computed tomography (CT), tomosynthesis provides some of the tomographic benefits of CT but at lower cost and radiation dose than CT. Compared to conventional chest radiography, chest tomosynthesis results in improved visibility of normal structures such as vessels, airway and spine. By reducing visual clutter from overlying normal anatomy, it also enhances detection of small lung nodules. This review article outlines the components of a tomosynthesis system, discusses results regarding improved lung nodule detection from the recent literature, and presents examples of nodule detection from a clinical trial in human subjects. Possible implementation strategies for use in clinical chest imaging are discussed.

Introduction

Digital tomosynthesis is a newly available imaging modality that offers the potential to be a substantial improvement over conventional chest radiography for the detection of subtle lung disease. It is a form of limited angle tomography that allows for the reconstruction of multiple section images from a set of projection images acquired as the X-ray tube moves along a prescribed path. Although originally conceived of many decades ago, tomosynthesis has only recently become practical for clinical use. Two commercial devices are currently on the market for chest imaging. Contemporary tomosynthesis devices use a conventional X-ray tube, a digital detector, a custom-designed device to move the X-ray tube, and appropriate reconstruction algorithms. Tomosynthesis has recently been applied to chest imaging for the detection of subtle pulmonary nodules, with very promising results.

This review will present the basic principles of digital tomosynthesis and will summarize the most recent clinical evaluations of this technique in chest imaging. Although tomosynthesis has potential utility in a variety of chest imaging applications, the one most commonly investigated is detection of small lung nodules, which will be the primary focus of this article. Other less investigated applications will also be briefly described.

Section snippets

Challenges in chest imaging

Chest radiography remains the mainstay for diagnosis of many lung diseases, despite advances in cross-sectional imaging techniques such as CT. It is frequently the first and may be the only imaging test performed in patients with known or suspected lung disease. It very likely remains the most commonly performed diagnostic imaging test worldwide [1]. Over the past one hundred years, technological advances have resulted in many improvements in chest radiography. Advances in electronics and

Digital tomosynthesis

Digital tomosynthesis is an imaging technique that yields some of the tomographic benefits of CT but at reduced cost and dose [5], [6], [32]. Although tomosynthesis has better spatial resolution in the xy plane (i.e., coronal plane) than CT, it does not have as good a resolution in the depth direction. Despite this tradeoff, tomosynthesis still permits improved performance over conventional chest radiography. Tomosynthesis also has the advantage that it can be easily implemented as an adjunct

Basics of chest tomosynthesis

Fig. 1 depicts the standard components of a typical chest tomosynthesis system. The patient is positioned in front of a stationary flat-panel detector, and a motorized tube crane causes the X-ray tube to move in a vertical path. Images are acquired rapidly during the course of tube movement, and are read out in coordination with the X-ray generator. A workstation is used to reconstruct the tomosynthesis section images.

We constructed a prototype chest tomosynthesis system in our laboratory. It

Chest tomosynthesis for lung nodule detection

There is growing interest in tomosynthesis for a number of clinical uses, including mammographic, orthopedic, and chest imaging applications, as evidenced by the increased number of tomosynthesis presentations at scientific meetings. As noted above, most of the interest in regard to chest tomosynthesis has been directed toward lung nodule detection. There have been few published results from clinical trials of chest tomosynthesis to date. Two main studies have been published so far, one from

Future directions

The main application of chest tomosynthesis to date has been in improving detection of pulmonary nodules, but it may also have other potential uses in thoracic imaging. Such potential uses include, but are not limited to, evaluation of suspected interstitial lung disease, early detection of infection in immunocompromised patients, detection of subtle pneumothoraces, detection of cardiac or coronary artery calcification and evaluation of ribs and spine for fractures, metastases or other osseous

Acknowledgments

The research described in this article was supported in part by grants from the U.S. National Institutes of Health (R01 CA080490) and GE Healthcare (Milwaukee, WI, USA). Duke University and GE Healthcare jointly hold a patent on a tube movement strategy in tomosynthesis. The authors wish to thank Devon J. Godfrey, PhD, Christina M. Li, Annette Rich, RT(R), Brenda Prince, RT(R), Melissa Jenkins, RT(R), and Anne Jarvis, RT(R)(M) for help in acquiring the clinical image data of research subjects.

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