Medical Imaging and Timely Diagnosis of Invasive Pulmonary Aspergillosis

and respiratory symptoms in a population of patients with a high a priori likelihood of developing invasive, opportunistic fun- gal infections. The majority of the patients had hematological immunosuppressive conditions; only 14% of patients had non- hematological immunosuppressive con- ditions. It was found that most patients (94%) presented with nodular lesions, and 61% of patients presented with a halo sign. Furthermore, the outcomes of patients presenting with a halo sign were signifi- cantly better than those of patients with other radiological abnormalities. This study provides large-scale confirmation of the diagnostic value of early CT scanning of the chest in patients with severe neu- tropenia who are developing respiratory symptoms and signs suggestive for IPA, as was established by Caillot et al. (3). Timely recognition of IPA shortens the delay be- fore institution of appropriate therapy, creating an opportunity for curing the dis- ease at an early stage with an inoculum amenable to antifungals. The CT halo sign appears early during the course of IPA, whereas the air crescent sign occurs later and is less useful for early diagnosis (4). Approximately half of the patients in the Global Comparative Aspergillosis Study did not have neutropenia at the time of enrollment in the treatment protocol. The high prevalence of the halo sign in this series of patients supports its diagnostic value even for severely immunocompro- mised patients without severe neutro-