{'fraction_non_alphanumeric': 0.04357298474945534, 'fraction_numerical': 0.011982570806100218, 'mean_word_length': 4.049450549450549, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
The air crescent sign: causes and characteristics.

A 41-year-old man who was undergoing chronic hemodialysis for end-stage renal disease presented with new-onset hemoptysis. His chest radiograph showed an opacified middle lobe (Fig. 1), a change from earlier radiographs. Two weeks later, the middle lobe contained a large cavity with a nonmobile, intracavitary, rounded mass (Fig. 2). Core biopsy of the cavitary lesion disclosed necrotic tissue with intravascular fungal elements (Fig. 3); culture grew Aspergillus fumigatus. 
 
 
 
Fig. 1 Chest radiograph shows cardiomegaly with bilateral alveolar infiltrates and opacification of the middle lobe. 
 
 
 
 
 
Fig. 2 Chest radiograph shows a large cavity in the middle lobe with an intracavitary fungus ball (arrows). 
 
 
 
 
 
Fig. 3 Photomicrograph shows necrotic tissue with fungal elements (arrows) in the wall and lumen of a blood vessel (H & E, orig. ×200).