Nonrigid temporal registration of multiphase CT pulmonary angiography using low-kV and low contrast: a feasibility...

This study aimed to compare the nonrigid temporal registration of multiphase computed tomography pulmonary angiography (CTPA) with single-phase CTPA in terms of radiation dose, contrast agent usage, objective and subjective image quality.

Consecutive patients suspected of acute pulmonary embolism were prospectively included in this study, and randomly received multiphase or single-phase CTPA. Regarding the contrast media, 15 mL was applied in the multiphase CTPA in comparison with 40 mL applied in the single-phase CTPA. Temporal registration was performed for multiphase CTPA during post-processing. Two experienced radiologists independently evaluated the image quality (IQ) based on objective measurements, subjective impression and diagnostic confidence. Patient demographics, scan parameters and image quality were compared between the two groups.

A total of 72 patients were analysed (37 multiphase CTPA and 35 single-phase CTPA). Positive pulmonary embolism was confirmed in five and seven patients, respectively. The two patient groups had similar demographics besides older age in those who underwent single-phase CTPA. Radiation dose and the contrast-to-noise ratio (CNR) were also similar between groups except for the CNR in the right main pulmonary artery. Both readers rated the multiphase CTPA with a statistically superior subjective IQ over the single-phase CTPA. The diagnostics confidence of the two CTPA protocols was similarly rated by one reader and slightly different according to the second reader.

The nonrigid temporal registration of multiphase CT pulmonary angiography could offer similar or even better image quality than the single-phase protocol and significantly reduce the amount of contrast usage.