Effect of CT-based attenuation correction on uptake ratios in skeletal SPECT

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Radiopharmacology

Background:

• Simultaneous SPECT/CT imaging offers improved anatomical localization and quantification over SPECT alone.
• Attenuation correction (AC) is crucial for accurate quantitative analysis in SPECT imaging.
• Polyphosphonates, such as diphosphonates (DPD), are widely used in bone scintigraphy to assess skeletal uptake.

Purpose of the Study:

• To evaluate the clinical relevance of patient-specific CT-based attenuation correction for skeletal DPD uptake analysis in SPECT/CT.
• To investigate the impact of SPECT-CT data misregistration on DPD uptake ratios.

Main Methods:

• Retrospective analysis of 36 bone SPECT/CT datasets.
• Region of Interest (ROI) measurements of DPD uptake in the lumbar spine and iliacal spinae.
• Comparison of uptake ratios between uncorrected (NAC) and attenuation-corrected (AC) images.
• Analysis of AC images with induced SPECT-CT misalignments (ACX, ACY, ACZ).

Main Results:

• AC significantly altered DPD uptake ratios across all studied regions, with changes ranging from 32% to 39%.
• Induced misalignments between SPECT and CT data caused significant changes in whole-slice uptake ratios (3.5%–25%).
• Misregistration particularly affected left-to-right ratios in facet joints (8%) and iliacal spines (31%).

Conclusions:

• CT-based attenuation correction significantly influences DPD uptake quantification in SPECT/CT.
• SPECT-CT data misalignment can lead to considerable errors in quantitative analysis, impacting diagnostic accuracy.
• Careful assessment for potential misalignments is essential during the clinical evaluation of attenuation-corrected SPECT/CT scans.