Relative thoracic changes from supine to upright patient position: A proton collaborative group study

Area of Science:

• Medical Imaging
• Radiation Oncology
• Anatomy

Background:

• Patient positioning is critical in radiotherapy to ensure accurate dose delivery.
• Understanding organ motion between different patient orientations (upright vs. supine) is essential for treatment planning.

Purpose of the Study:

• To quantify and analyze positional changes of key thoracic organs between upright and supine patient orientations.
• To assess the clinical relevance of these positional shifts for radiotherapy.

Main Methods:

• Utilized a commercial treatment planning system (TPS) to measure anatomical distances.
• Analyzed four-dimensional computed tomography (4D CT) datasets for upright and supine positions.
• Calculated 95% confidence intervals (CI) to determine the statistical significance of observed changes.

Main Results:

• The distance from the bottom of the heart to the top of the sternum changed by +2.6% (+4 mm) (95% CI [+0.30%,+4.9%]).
• The distance from the C3 vertebra center to the backrest changed by +29% (95% CI [+22%,+36%]).
• Contoured lung volumes increased: left lung by +17% (95% CI [+12%,+21%]) and right lung by +9.9% (95% CI [+4.1%,+16%]).
• Changes in the sternum-to-liver distance were inconclusive due to high uncertainty.

Conclusions:

• Significant positional changes in lung volumes and heart position were observed between upright and supine orientations with 95% confidence.
• These findings suggest that patient positioning can impact internal organ positions, potentially affecting radiotherapy accuracy.
• Further investigation is needed to fully understand the implications for upright radiotherapy treatments.