Physics

Internal medicine

Radiology

Nuclear medicine

Biology

Optics

Resolution (logic)

Paleontology

Artificial intelligence

Tomography

Volume (thermodynamics)

Lung

Nodule (geology)

High-resolution computed tomography

Photon counting

Computer science

Computed tomography

Quantum mechanics

Medicine

Detector

Journal of Medical Imaging

An ultra-high resolution (UHR) mode, with a detector pixel size of 0.25 mm×0.25 mm relative to isocenter, has been implemented on a whole body research photon-counting detector (PCD) computed tomography (CT) system. Twenty synthetic lung nodules were scanned using UHR and conventional resolution (macro) modes and reconstructed with medium and very sharp kernels. Linear regression was used to compare measured nodule volumes from CT images to reference volumes. The full-width-at-half-maximum of the calculated curvature histogram for each nodule was used as a shape index, and receiver operating characteristic analysis was performed to differentiate sphere- and star-shaped nodules. Results showed a strong linear relationship between measured nodule volumes and reference volumes for both modes. The overall volume estimation was more accurate using UHR mode and the very sharp kernel, having 4.8% error compared with 10.5% to 12.6% error in the macro mode. The improvement in volume measurements using the UHR mode was more evident for small nodule sizes or star-shaped nodules. Images from the UHR mode with the very sharp kernel consistently demonstrated the best performance [AUC=(0.839,0.867)] for separating star- from sphere-shaped nodules, showing advantages of UHR mode on a PCD CT scanner for lung nodule characterization.

Lung nodule volume quantification and shape differentiation with an ultra-high resolution technique on a photon-counting detector computed tomography system