How is Low-Dose Computed Tomography (LDCT) for lung cancer screening performed and is it similar to an X-ray?

How Low-Dose CT Lung Cancer Screening is Performed

Low-dose CT (LDCT) lung cancer screening is performed as a quick, non-contrast helical CT scan that is similar to a regular chest X-ray in terms of patient experience—you simply lie still and hold your breath—but uses CT technology with significantly reduced radiation exposure. 1

The Scanning Procedure

Patient Positioning and Scan Acquisition

• You lie on your back on the CT table for a single breath-hold scan that takes images from your neck (thoracic inlet) down to your adrenal glands, typically completed in seconds 2
• No intravenous contrast (IV dye) is used, making it simpler and safer than diagnostic CT scans 1
• The entire scanning process takes only a few minutes, with the actual image acquisition occurring during one breath-hold 2

Technical Differences from Standard X-rays

While the patient experience feels similar to an X-ray (lying still, holding your breath), LDCT is fundamentally different:

• LDCT uses rotating X-ray beams to create detailed cross-sectional images of your lungs, unlike chest X-rays which produce a single flat image 1
• LDCT can detect very small lung nodules (as small as 1-2 mm) that would be invisible on regular chest X-rays 1, 3
• The radiation dose is approximately 22% of a standard diagnostic CT scan and roughly equivalent to 6 months of natural background radiation 2

Radiation Exposure Details

Dose Parameters

• The target radiation dose is ≤3 mGy (milligray) for most patients, which is substantially lower than diagnostic CT scans 1, 2
• Technical settings include 120 kVp tube voltage and 20-40 mA tube current, adjusted based on your body size 2
• All technicians must be specifically trained in the low-dose protocol to ensure proper technique 1

Image Quality and Detection

What the Scan Shows

• Images are reconstructed at ≤1.0 mm slice thickness (preferred) to optimize detection of small nodules 2, 4
• Radiologists view images using specialized "lung windows" that enhance visualization of lung tissue and nodules 2
• The scan can detect solid nodules, part-solid nodules, and ground-glass opacities that may represent early lung cancers 1

Important Distinction from Chest X-rays

Chest X-rays are NOT recommended for lung cancer screening because they lack the sensitivity to detect early-stage cancers and have not been shown to reduce lung cancer mortality 1, 5. LDCT is far superior for this purpose, with studies showing 20% reduction in lung cancer mortality 5, 3.

What to Expect During Your Visit

Before the Scan

• You'll have a shared decision-making discussion with your healthcare provider about the benefits and risks of screening 1, 5
• No special preparation is typically needed—no fasting, no IV placement 1

During the Scan

• You'll be asked to hold your breath for 5-10 seconds while the scanner rotates around you 2
• The procedure is painless and non-invasive 6
• You can resume normal activities immediately after the scan

After the Scan

• Results are reported using standardized systems like Lung-RADS, which categorizes findings and provides specific follow-up recommendations 1
• Most scans (about 75-85%) show no concerning findings or only benign nodules requiring routine annual follow-up 1

Key Advantages Over X-rays

• LDCT detects lung cancers at earlier, more treatable stages (65-85% detected at stage I) compared to chest X-rays 1
• Sensitivity for detecting solid pulmonary nodules is much higher than standard chest radiography 1, 7
• The three-dimensional nature of CT imaging allows precise measurement and characterization of nodules 1

Important Caveat

LDCT may be less sensitive for detecting very low-density ground-glass nodules in larger patients, though it remains far superior to chest X-rays for lung cancer screening 1.