From the Guidelines
The best type of chest CT scan to visualize atelectasis is a high-resolution CT (HRCT) scan without contrast, utilizing thin-section imaging with a slice thickness of 1.5 mm or thinner, as recommended by recent studies 1. When evaluating atelectasis, it is crucial to prioritize techniques that provide the most detailed images of lung parenchyma.
- HRCT scans are optimal for identifying areas of collapsed lung tissue characteristic of atelectasis.
- The scan should be performed during a breath-hold at full inspiration to maximize lung expansion, which helps distinguish true atelectasis from normal expiratory lung volume changes.
- In some cases, additional expiratory images may be helpful to differentiate atelectasis from air trapping.
- Contrast administration is generally not necessary for atelectasis evaluation unless there's suspicion of an underlying mass or pulmonary embolism causing the collapse. Key considerations for the CT protocol include:
- Thin slices (typically 1-2 mm) that provide excellent spatial resolution to visualize the characteristic signs of atelectasis, including displacement of fissures, crowding of vessels, bronchial distortion, and increased density of affected lung segments.
- The use of modern multidetector CT scanners, such as 320-row multidetector CT scanners, which can enable cinematic 4-D volumetric images of the trachea, allowing time-resolved coverage of the entire trachea throughout an inspiratory/expiratory cycle 1.
- Low-dose volumetric CT using 40 to 80 mA is comparable to standard higher-dose techniques in demonstrating degree of trachea collapse, and low-dose techniques have been widely adopted for dynamic expiratory imaging assessment 1.
From the Research
Types of Chest CT for Atelectasis
To visualize atelectasis, the following types of chest Computed Tomography (CT) scans can be utilized:
- High-resolution CT (HRCT) for detailed lung parenchyma evaluation 2
- Contrast-enhanced CT to differentiate between benign and malignant causes of obstructive atelectasis 2
- Computed Tomographic Pulmonary Angiography (CT-PA) to evaluate patients with suspected pulmonary embolism and identify atelectasis as an alternative diagnosis 3
- Functional lung imaging using CT, such as CT-Spectral Imaging (Dual Energy) and CT-Perfusion, to assess lung function and ventilation-perfusion mismatch 4
Advantages of Each Type
Each type of chest CT has its advantages:
- HRCT provides detailed images of the lung parenchyma, allowing for accurate diagnosis of atelectasis and its underlying causes 2
- Contrast-enhanced CT helps differentiate between benign and malignant causes of obstructive atelectasis, guiding further management 2
- CT-PA is useful in evaluating patients with suspected pulmonary embolism and identifying atelectasis as an alternative diagnosis, reducing unnecessary anticoagulation therapy 3
- Functional lung imaging using CT provides comprehensive information on lung function, enabling better understanding of the effects of various diseases and therapeutic interventions 4
Clinical Applications
These types of chest CT scans have various clinical applications:
- Diagnosing atelectasis and its underlying causes, such as obstructive airway disease or pulmonary embolism 2, 3
- Evaluating patients with suspected pulmonary embolism and identifying alternative diagnoses, such as atelectasis or pneumonia 3
- Assessing lung function and ventilation-perfusion mismatch in patients with various lung diseases, such as asthma or chronic obstructive pulmonary disease (COPD) 4