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4 Diagnosis Table 2. High-Resolution CT Scanning Parameters Recommended Scanning Protocol Advantages of Updated Recommendations 1. Noncontrast examination — 2. Volumetric acquisition with selection of: • Sub-millimetric collimation • Shortest rotation time • Highest pitch • Tube potential and tube current appropriate to patient size: ▶ Typically 120 kVp and ≤240 mAs ▶ Lower tube potentials (e.g., 100 kVp) with adjustment of tube current encouraged for thin patients • Use of techniques available to avoid unnecessary radiation exposure (e.g., tube current modulation) A. Acquisition covering the entire lung volume (vs. analysis of 10% of lung volume with sequential scanning ) • No risk of missing subtle infiltrative abnormalities • Possibility of multiplanar reformations, helpful for analysis of the ILD pattern and predominant distribution of lung changes • Possibility of post-processing to optimize detection of subtle hypoattenuated lesions (minimum intensity projection) and micronodular infiltration (maximum intensity projection) • Possibility of detection of additional lesions (e.g., incidental identification of lung nodule or focal consolidation in lung fibrosis that may correspond to lung carcinoma) • Optimal to assess progression or improvement in patient's follow-up B. Dramatic increase in temporal resolution and speed of data acquisition • Motion-free images C. Availability of numerous dose-reduction tools 3. Reconstruction of thin-section CT images (≤1.5 mm): • Contiguous or overlapping • Using a high-spatial-frequency algorithm • Iterative reconstruction algorithm if validated on the CT unit (if not, filtered back projection) — 4. Number of acquisitions: • Supine: inspiratory (volumetric) • Supine: expiratory (can be volumetric or sequential) • Prone: only inspiratory scans (can be sequential or volumetric); optional (see text) • Inspiratory scans obtained at full inspiration A. Expiratory scans useful to detect air trapping B. Prone scans allow analysis of peripheral lung changes without dependent lung atelectasis that may be mistaken for abnormal lung infiltration or mimic disease (e.g., pseudohoneycombing when combined with paraseptal emphysema) C. Inadequate inspiration increases lung attenuation (which should not be interpreted as ground-glass attenuation) and is responsible for dependent lung atelectasis (which may mimic abnormal lung infiltration or mask subtle abnormalities) 5. Recommended radiation dose for the inspiratory volumetric acquisition: • 1–3 mSv (i.e., "reduced" dose) • Strong recommendation to avoid "ultralow-dose CT" (<1 mSv) A. Considerable dose reduction compared to conventional scanning