Journal Article

Optimal image reconstruction for detection and characterization of small pulmonary nodules during low-dose CT

Hashemi, SayedMasoud, Paul, Narinder S., Mehrez, Hatem, Cobbold, Richard S. C.

2014

Overview

Objectives To optimize the slice thickness/overlap parameters for image reconstruction and to study the effect of iterative reconstruction (IR) on detectability and characterization of small non-calcified pulmonary nodules during low-dose thoracic CT. Materials and methods Data was obtained from computer simulations, phantom, and patient CTs. Simulations and phantom CTs were performed with 9 nodules (5, 8, and 10 mm with 100, −630, and −800 HU). Patient data were based on 11 ground glass opacities (GGO) and 9 solid nodules. For each analysis the nodules were reconstructed with filtered back projection and IR algorithms using 10 different combinations of slice thickness/overlap (0.5–5 mm). The attenuation (CT#) and the contrast to noise ratio (CNR) were measured. Spearman’s coefficient was used to correlate the error in CT# measurements and slice thickness. Paired Student’s t test was used to measure the significance of the errors. Results CNR measurements : CNR increases with increasing slice thickness/overlap for large nodules and peaks at 4.0/2.0 mm for smaller ones. Use of IR increases the CNR of GGOs by 60 %. CT# measurements : Increasing slice thickness/overlap above 3.0/1.5 mm results in decreased CT# measurement accuracy. Conclusion Optimal detection of small pulmonary nodules requires slice thickness/overlap of 4.0/2.0 mm. Slice thickness/overlap of 2.0/2.0 mm is required for optimal nodule characterization. IR improves conspicuity of small ground glass nodules through a significant increase in nodule CNR. Key Points • Slice thickness/overlap affects the accuracy of pulmonary nodule detection and characterization. • Slice thickness ≥3 mm increases the risk of misclassifying small nodules. • Optimal nodule detection during low-dose CT requires 4.0/2.0-mm reconstructions. • Optimal nodule characterization during low-dose CT requires 2.0/2.0-mm reconstructions. • Iterative reconstruction improves the CNR of ground glass nodules by 60 %.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V
• Subject: Accuracy / Algorithms / Biomedical engineering / Calcification / Chest / Computer Simulation / Diagnostic Radiology / Humans / Image Processing, Computer-Assisted / Imaging / Internal Medicine / Interventional Radiology / Lung cancer / Medicine / Medicine & Public Health / Mortality / Multiple Pulmonary Nodules - diagnostic imaging / Neuroradiology / Phantoms, Imaging / Radiology / Reproducibility of Results / Simulation / Tomography / Tomography, X-Ray Computed - methods / Ultrasound