Effects of attenuation map accuracy on attenuation-corrected micro-SPECT images

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Quantitative Analysis

Background:

• Single-photon emission computed tomography (SPECT) relies on accurate attenuation correction for quantitative imaging.
• X-ray computed tomography (CT) derived attenuation maps are crucial but susceptible to registration and coefficient inaccuracies.
• Investigating the impact of these inaccuracies on micro-SPECT quantification is essential for reliable preclinical research.

Purpose of the Study:

• To evaluate the influence of attenuation map imperfections on micro-SPECT quantification.
• To assess the impact of misalignments (shifts, rotations) and altered attenuation coefficients.
• To determine the robustness of micro-SPECT quantitative accuracy under realistic error conditions.

Main Methods:

• Simulated misalignments (shifts up to 3mm, rotations up to 15°) and attenuation coefficient variations (±10%) were applied to micro-SPECT/CT data.
• Experiments utilized a NEMA NU 4-2008 phantom and rat cadavers with known activity sources.
• Quantitative changes in measured activities within regions of interest were analyzed for different isotopes (125I, 201Tl, 99mTc, 111In).

Main Results:

• Image quantification showed minimal changes (<1.5% for 1mm shifts, <4.5% for 3mm shifts) across various isotopes.
• Rotational misalignments (15°) had a smaller impact than 3mm shifts.
• Altering attenuation coefficients by ±10% resulted in activity changes below 5.2% (125I) and 2.7% (others), with similar trends observed in rat studies.

Conclusions:

• Micro-SPECT quantification demonstrates significant robustness to common imperfections in attenuation maps.
• Despite challenges in achieving perfect attenuation map accuracy in clinical settings, micro-SPECT imaging provides reliable quantitative data.
• These findings support the use of micro-SPECT for accurate quantitative preclinical studies.