Effect of lung inflation states on chest CT image quality and pulmonary nodule detection with visualized respiratory Indicator.

Background: Parts of lung cancer screening guidelines describe the specific scanning protocol of low dose CT (LDCT), among which the requirement for respiratory state is full inspiration end-breath hold. The main focus of lung cancer screening is to evaluate and follow-up pulmonary nodule (PN), so the display and detection of PNs are important. To achieve full inspiration, strict breathing training is required for patients. In clinical scans, the lung inflation state of patient is not visualized and the possibility of incomplete inspiration exists. Thus, the image quality and nodule detection of chest CT in different lung inflation states need to be explored.

Methods: Fifty-six participants (32 females, 24 males) were included in this prospective study. Each participant underwent non-contrast chest CT scanned three times continually with different lung inflation state, including deep inspiration end-breath hold, calm breath hold, and deep expiration end-breath hold. A respiratory indicator was used to monitor the state of lung inflation visually. Subjective and objective image quality and nodule detection among these lung inflation states were analyzed in this study.

Results: The images of deep inspiration end-breath hold yielded the best, with superior subjective ratings and objective image quality, including the lowest image noise and the best signal-to-noise ratio. PN detection was most accurate in the inflation state of deep inspiration end-breath hold, particularly for nodules ≤ 5 mm, while fewer nodules detected in the inflation state of calm breath hold and deep expiration end-breath hold.

Conclusions: Lung inflation states significantly impact both image quality and PN detection in chest CT. Deep inspiration end-breath hold provided optimal image quality and nodule detection, while non-fully inflated states reduced diagnostic accuracy, especially for PNs≤5 mm. In clinical application, deep inspiration end-breath hold is recommended as the best inflation state of chest CT.