Evaluation of Four-dimensional (4D) Computed Tomography (CT) Pulmonary Ventilation Imaging by Comparison with Single Photon Emission Computed Tomography (SPECT) Scans for a Lung Cancer Patient

The goal of this study was to present a method for physiologic validation and show results for a comparison of the 4D-CT ventilation and SPECT ventilation or perfusion. A 4D-CT and a SPECT ventilation/perfusion (V/Q) (VSPECT and QSPECT) scans were acquired for a lung cancer patient. Two 4D-CT ventilation images were created using two metrics: Hounsfield unit (HU)-change (V4D-CT) and Jacobian determinant (V4D-CT), and were compared with SPECT. The 4D-CT ventilation images were of higher resolution than SPECT. Areas of visual agreement and disagreement were identified. VSPECT suffered from central airway depositions. Quantitatively, the correlation coefficients with VSPECT (QSPECT) were 0.030 (0.357) for V4D-CT, and 0.184 (0.479) for V4D-CT. The physiologic accuracy of 4D-CT ventilation imaging has been evaluated on a human subject. The weak correlations with SPECT could be due to limitations of the 4D-CT and/or SPECT techniques. Further investigation and patient studies are needed.