The posterior pleural reflections.

Area of Science:

• Radiology
• Medical Imaging
• Thoracic Anatomy

Background:

• The paraspinal and paraaortic lines are observed on plain radiography.
• These lines are traditionally thought to represent posterior mediastinal pleural reflections.
• Their precise nature and diagnostic implications remain debated.

Purpose of the Study:

• To investigate the nature of the posterior mediastinal pleural reflections, specifically the paraspinal and paraaortic lines.
• To determine if these lines represent anatomical structures or optical phenomena.
• To assess the reliability of plain radiography in evaluating the posterior mediastinum.

Main Methods:

• Conventional linear tomography, computed tomography (CT), and photodensitometry were employed.
• Eight normal patients were studied and compared with patients exhibiting abnormal features.
• Correlated evidence from multiple imaging modalities was analyzed.

Main Results:

• The study indicates that the paraspinal and paraaortic lines are not distinct anatomical structures.
• These lines are identified as optical phenomena, specifically Mach bands.
• Their appearance is attributed to the shape of the lung-mediastinal interface, not tissue composition.

Conclusions:

• Posterior mediastinal lines on plain radiography are optical phenomena (Mach bands).
• Their presence does not reliably indicate normal or abnormal posterior mediastinal or pleural conditions.
• Computed tomography (CT) is the definitive method for differentiating normal from pathological states of the posterior mediastinum and pleura.