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Spatial distribution of dose in computed tomography with special reference to thin-slice techniques.
1Department of Diagnostic Radiology, Akademiska Sjukhuset, University of Uppsala, Sweden.
Acta Radiologica (Stockholm, Sweden : 1987)
|November 1, 1987
Summary
Computed tomography (CT) scanner dose distribution varies significantly. Multiple scans reduce surface-to-center dose differences due to scattered radiation, crucial for patient safety in diagnostic imaging.
Area of Science:
- Medical Physics
- Radiological Dosimetry
Background:
- Computed Tomography (CT) is a vital diagnostic tool, but accurate dose assessment is critical.
- Understanding spatial dose distribution is essential for optimizing CT protocols and minimizing patient exposure.
Purpose of the Study:
- To measure and analyze the spatial dose distribution in a polystyrene phantom across seven CT scanners.
- To evaluate the impact of single and multiple scan procedures on dose profiles.
- To compare CT dose index and multiple-scan average dose across different scanners.
Main Methods:
- Measurements were conducted in a cylindrical polystyrene phantom (200 mm diameter) using seven CT scanners in head mode.
- Both radial and axial dose profiles were measured for narrow slices (1.5-4 mm).
- Dose distribution for multiple-scan procedures was calculated, simulating examinations like orbital CT.
Main Results:
- The surface-to-center dose ratio for a single scan ranged from 1.8 to 4.3, higher for narrow slices.
- Multiple contiguous scans reduced the surface-to-center dose difference due to scattered radiation.
- CT Dose Index varied from 5.6 to 27.2 mGy/100 mAs; multiple-scan average dose ranged from 4.3 to 16.4 mGy/100 mAs.
Conclusions:
- Significant variations in CT dose index exist among scanners.
- Multiple scanning procedures effectively mitigate dose heterogeneity, highlighting the importance of scatter radiation.
- These findings are crucial for establishing standardized dose monitoring and optimization in CT imaging.