Semi-Quantitative Analysis for Determining the Optimal Threshold Value on CT to Measure the Solid Portion of...

Area of Science:

• Radiology
• Pulmonary Medicine
• Oncology

Background:

• Pulmonary subsolid nodules require accurate characterization to differentiate between benign and malignant lesions.
• Identifying the solid component is crucial for assessing invasiveness and guiding treatment decisions.

Purpose of the Study:

• To determine the optimal Hounsfield unit (HU) threshold on CT scans for detecting the solid components of pulmonary subsolid nodules.
• To establish a reliable surrogate marker for invasive foci using CT imaging.

Main Methods:

• Retrospective review of thin-section non-enhanced chest CT scans from 25 patients with pathologically confirmed minimally invasive adenocarcinoma.
• Evaluation of various HU thresholds (-600 to -100 HU) to define the solid portion of nodules.
• Measurement of solid portion diameters and comparison with pathological invasive foci size using a linear mixed model.

Main Results:

• A threshold of -400 HU demonstrated the lowest bias between the CT-measured solid portion diameter and the pathological invasive foci size.
• At -400 HU, the differences in diameter measurements were statistically insignificant (p = 0.2682 for axial, p = 0.963 for multiplanar).

Conclusions:

• The -400 HU threshold is proposed as the optimal value for defining the solid portion of subsolid nodules on CT.
• -400 HU serves as a valuable surrogate marker for quantitative analysis of invasive foci in pulmonary subsolid nodules.