Evaluation of techniques for slice sensitivity profile measurement and analysis

Area of Science:

• Medical Physics
• Radiological Imaging
• Diagnostic Imaging Technology

Background:

• Accurate measurement of slice sensitivity profiles (SSP) is crucial for quantitative analysis in computed tomography (CT).
• The full width at half maximum (FWHM) of the SSP is a key parameter for assessing image spatial resolution and slice thickness accuracy.
• Variations in phantom design and analysis methods can potentially influence SSP and FWHM measurements.

Purpose of the Study:

• To compare the full width at half maximum (FWHM) of slice sensitivity profiles (SSP) generated using different commercially available CT phantoms.
• To evaluate and determine the most appropriate imaging technique and analysis method for SSP and FWHM determination.
• To assess the impact of different region of interest (ROI) values and FWHM calculation methods on measurement accuracy.

Main Methods:

• Four CT phantoms (Fluke CT-SSP, Gammex 464, CatPhan 600, Kagaku Micro Disc) were imaged using standardized CT parameters (120 kVp, 325 mAs, head FOV, helical scan).
• Images were reconstructed across various slice thicknesses (0.625 mm - 5.0 mm).
• A custom computer program analyzed images to generate SSPs and determine FWHM using mean vs. maximum ROI values and linear interpolation vs. Gaussian curve fitting.

Main Results:

• No significant differences in FWHM were found between the four phantoms (p ≥ 0.089), with an average error of 3.5% compared to manufacturer specifications.
• Using the mean ROI value resulted in statistically different FWHMs (p ≤ 3.99 × 10¹³), whereas different FWHM calculation methods showed no significant difference (p ≤ 0.499).
• SSP evaluation is dependent on the ROI value chosen; the maximum ROI value is recommended for generating SSPs.

Conclusions:

• CT phantom type does not significantly affect SSP FWHM measurements when using appropriate analysis methods.
• The maximum ROI value should be preferentially used for SSP generation to ensure reliable FWHM determination.
• SSP measurement is robust and independent of the specific phantom utilized in this study, highlighting the importance of standardized analysis protocols.