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Effect of source strength and attenuation on dual photon absorptiometry
M C DaCosta1, M M Luckey, D E Meier
1Department of Physics-Nuclear Medicine, Mount Sinai Medical Center, New York, New York 10029.
Summary
Dual photon absorptiometry (DPA) bone mineral density (BMD) measurements show systematic errors due to source strength variations. Software upgrades reduced but did not eliminate these errors, impacting patient management.
Area of Science:
- Medical Physics
- Radiological Imaging
- Bone Densitometry
Background:
- Systematic errors in dual photon absorptiometry (DPA) for bone mineral density (BMD) have been linked to source strength.
- An erroneous deadtime correction algorithm is suspected as the cause of these DPA measurement inaccuracies.
Purpose of the Study:
- To evaluate the impact of varying source activities and attenuation depths on BMD calculations using DPA.
- To assess the effectiveness of software upgrades in correcting DPA systematic errors related to source strength.
Main Methods:
- A phantom was used to simulate DPA scans at different source strengths (0.3 and 1.0 Ci) and water depths (16.4 and 24.5 cm).
- Scans were acquired using a commercial lumbar spine scanner and processed with initial and upgraded software versions.
Main Results:
- Initial software showed BMD variations of 2-14% with changes in source strength and attenuating depth.
- Software revisions decreased these discrepancies, but a residual 6% difference remained.
- The remaining error is significant enough to affect clinical decisions and research findings.
Conclusions:
- Source strength and attenuation depth introduce systematic errors in DPA BMD measurements.
- While software improvements can mitigate these errors, they do not fully resolve the issue.
- Further refinement of DPA algorithms is necessary for accurate bone mineral density assessment.