A feasibility study for anatomical noise reduction in dual-energy chest digital tomosynthesis

Abstract

Lung cancer is the leading cause of cancer death worldwide. Thus, early diagnosis is of considerable importance. For early screening of lung cancer, computed tomography (CT) has been used as the gold standard. Chest digital tomosynthesis (CDT) is a recently introduced modality for lung cancer screening with a relatively low radiation dose compared to CT. The dual energy material decomposition method has been proposed for better detection of pulmonary nodules by means of reducing anatomical noise. In this study, the possibility of material decomposition in CDT was tested by both a simulation study and an experimental study using a CDT prototype. The Geant4 application for tomographic emission (GATE) v6 and tungsten anode spectral model using interpolating polynomials (TASMIP) codes were used for the simulation study to create simulated phantom shapes consisting of five inner cylinders filled with different densities of bone and airequivalent materials. Furthermore, the CDT prototype system and human phantom chest were used for the experimental study. CDT scan in both the simulation and experimental studies was performed with linear movement and 21 projection images were obtained over a 30 degree angular range with a 1.5 degree angular interval. To obtain materialselective images, a projectionbased energy subtraction technique was applied to high and low energy images. The resultant simulation images showed that dual-energy reconstruction could achieve an approximately 32% higher contrast to noise ratio (CNR) in images and the difference in CNR value according to bone density was significant compared to single energy CDT. Additionally, image artifacts were effectively corrected in dual energy CDT simulation studies. Likewise the experimental study with dual energy produced clear images of lung fields and bone structure by removing unnecessary anatomical structures. Dual energy tomosynthesis is a new technique; therefore, there is little guidance regarding its integration into clinical practice and this study can be used to improve the diagnostic efficiency of lung field and spinal bone screening using CDT. K: X-ray radiography and digital radiography (DR); Computerized Tomography (CT) and Computed Radiography (CR); Medical-image reconstruction methods and algorithms, computeraided diagnosis; Medical-image reconstruction methods and algorithms, computer-aided software 1Corresponding author.

Comparison study of noise reduction algorithms in dual energy chest digital tomosynthesis

“…However, the low detection sensitivity for small size lung nodules is well known. On the other hand, CDT provides medical images with much higher sensitivity compared to chest radiography by addressing anatomical overlapping problems in the chest [4,5].…”

“…The dual energy X-ray imaging technique, with its ability to produce separate soft tissue and bone radiographic images, is an interesting approach to reduce anatomical noise in chest images and improve pathology diagnosis [7][8][9]. Because of this advantage, the dual energy X-ray imaging technique was suggested to be an effective method for resolving inherent problems associated with data incompleteness in CDT [5]. For example, the previous study regarding dual energy CDT demonstrated that the image artifacts were effectively reduced, and the diagnostic efficiency was increased by focusing on structures in the region of interest (ROI) by simplifying anatomical structure with a dual-energy material decomposition technique.…”

Improvement of material decomposition and image quality in dual-energy radiography by reducing image noise

“…However, the radiation dose to the patient is a cause of concern in dual-energy X-ray imaging due to the two exposures with different X-ray spectra. Therefore, the exposure parameters should be adjusted in dual-energy radiography to deliver a reasonable radiation dose [9].…”