Example of HCT-OP on CT scan of the chest. Noncontrast axial CT image, demonstrating multifocal consolidative and ground-glass pulmonary opacities. The atoll sign (arrowhead) can occasionally be seen and is characterized by central ground-glass opacity surrounded by dense consolidation, representing perilobular involvement, known as the reversed halo sign. Involvement in this case is predominantly peripheral, but HCT-OP can also be peribronchovascular, or occasionally nodular.