Final answer:
Application software is not directly captured by PACS, as PACS (Picture Archiving and Communication System) is focused on medical imaging modalities like CT, MRI, PET scans, and ultrasound, which generate the images that PACS stores and manages.
Step-by-step explanation:
The question pertains to PACS, which stands for Picture Archiving and Communication System. This system is used for storing, retrieving, managing, distributing, and presenting medical images. When evaluating the modalities not directly captured by PACS, we need to consider that PACS is designed to handle imaging modalities like CT scans, MRI, PET scans, and ultrasound. Now, looking at the options provided, digital fluoroscopy (a), picture archiving (c), and communication system (d) are all related directly to the functionalities of PACS. However, application software (b) is a broader category that can include a range of softwares used for various purposes within healthcare and is not a modality. Therefore, application software is the correct answer as it is not a modality directly captured by PACS. PACS itself can be considered a type of application software, but it is specifically designed for handling medical imaging data.