Accuracy of CT-based attenuation correction in PET/CT bone imaging.

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Radiology

Background:

• Accurate attenuation correction is crucial for quantitative Positron Emission Tomography (PET) imaging.
• Standard CT-based attenuation correction methods are well-established for soft tissues but less characterized for bone.
• The impact of CT imaging parameters, such as kilovoltage peak (kVp), on bone attenuation correction accuracy is not fully understood.

Purpose of the Study:

• To evaluate the accuracy of CT-based attenuation correction for PET data in bone.
• To quantify the underestimation of attenuation coefficients in bone using CT.
• To assess the impact of CT-derived attenuation map inaccuracies on PET standardized uptake values (SUVs) in bone.

Main Methods:

• Bovine femur segments and patient data were used to measure CT attenuation coefficients at various kVp settings.
• A (68)Ga/(68)Ge transmission scan served as the reference standard for attenuation values at 511 keV.
• Simulated and actual patient PET emission data were used to evaluate the effect of attenuation map errors on SUVs.

Main Results:

• CT-based linear attenuation underestimated true values by 2.9% for cancellous bone and 1.3% to 14.1% for compact bone depending on kVp.
• Patient scans at 140 kVp showed an average underestimation of approximately 2% in bony regions.
• PET SUV errors in bone were found to be roughly proportional to errors in the estimated linear attenuation coefficients.

Conclusions:

• CT-based attenuation correction introduces a bias in bone PET SUVs, ranging from 2.4% to 5.9% at 120-140 kVp.
• Lower kVp settings increase the potential for significant errors in dense bone attenuation correction.
• Careful evaluation of CT-based attenuation correction is necessary for quantitative PET studies involving bone uptake.