Comparison of topogram-based body size indices for CT dose consideration and scan protocol optimization

Area of Science:

• Medical Imaging
• Radiological Physics
• Diagnostic Radiology

Background:

• Accurate patient body size estimation is crucial for optimizing computed tomography (CT) radiation dose.
• Traditional methods for body size assessment in CT may lack precision.
• Topogram-based indices offer a potential solution for real-time dose adjustment.

Purpose of the Study:

• To compare various topogram-based patient body size indices.
• To identify the optimal index for CT dose consideration and protocol optimization.

Main Methods:

• Retrospective analysis of 43 thorax and abdomen CT scans.
• Calculation of water-equivalent diameter (D(w)) as the gold standard.
• Computation and correlation of four topogram-based indices: average diameter (D), girth (G), topogram projection area (E(topo)), and improved topogram projection area (E(topo)´).
• Linear regression analysis to assess accuracy in estimating D(w).

Main Results:

• The improved topogram projection area (E(topo)´) demonstrated the lowest standard error (±1.3 cm) in estimating D(w).
• E(topo)´ was significantly more accurate than E(topo) (±2.1 cm), D (±2.8 cm), and G (±3.1 cm).
• Linear regression models confirmed the superior accuracy of E(topo)´.

Conclusions:

• The improved topogram projection area (E(topo)´) is the most accurate topogram-based index for estimating patient x-ray attenuation.
• E(topo)´ serves as an optimal index for determining appropriate CT radiation dose levels for individual patients.
• This index facilitates personalized CT dose management and protocol optimization.