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Astonish reconstruction

White Paper
Philips NM Marketing Philips Healthcare

Myocardial perfusion imaging is a useful tool to help diagnose patients suspected of having coronary artery disease, or to assess patients with known disease. There has been significant growth in the number of these procedures with about 8.9 million performed in 2007. The laboratories performing these procedures are under pressure to reduce costs, improve image acquisition efficiency, reduce absorbed radiation dose, and improve diagnostic accuracy. Additionally, the recent shortages of Tc-99m have further increased the call for more efficient use of Tc-99m-labeled radiopharmaceuticals.

To address these needs, Philips has developed an improved reconstruction method termed Astonish. Astonish improves reconstruction accuracy and makes more efficient use of acquired counts by incorporating imaging physics into the reconstruction process. Astonish also provides for scatter and attenuation correction which can mitigate artifacts in the imaging process that can reduce lesion contrast or mimic perfusion defects.

Clinical trials
The clinical imaging performance of Astonish and Astonish with scatter and attenuation correction was evaluated in a published, multicenter trial.1,2 Both catheterization and normalcy were used as the gold standards. Image quality, diagnostic confidence and diagnostic accuracy for detection of coronary artery disease was evaluated on data from 187 consecutive patients undergoing clinically-indicated myocardial perfusion SPECT studies.

Astonish trial results in half-count imaging

Image quality
There was a statistically significant improvement in image quality for both full-count and half-count images reconstructed with Astonish in comparison with those reconstructed with filtered back projection (FBP).

Interpretive certainty
There was no statistical difference in the interpretive certainty of full-count and half-count images reconstructed with Astonish, p=0.18. This demonstrates the ability of Astonish to achieve good image quality with half the counts.

Diagnostic accuracy
There was not a statistical difference in the diagnostic accuracy of full-time data reconstructed with filtered back projection or full-count or half-count imaging using Astonish. However, there was a statistically significant improvement in specificity and normalcy when myocardial perfusion data was corrected for scatter and attenuation. This was true for both full-count and half-count data.

Astonish trial results in stress only imaging

In the stress only portion of the trial, patient studies were interpreted without using the rest images of the studies.

Interpretive certainty
The stress-only data provided a high level of diagnostic confidence for both the full-count and half-count data, and a high degree of diagnostic accuracy was obtained.

To test the robustness of results derived from full-count and half-count images other stress only comparisons were performed. There was no statistical difference for summed stress scores, ejection fraction, or the need for resting images between the full-count and half-count data. There was a desire for resting data in approximately 20% of the images interpreted with stress-only images.

Finally, a comparison was performed between stress-only half-count Astonish with scatter and attenuation correction and traditional rest/stress FBP SPECT. The same diagnostic accuracy was found despite using only a single image set (stress-only) and with half the counts in the images reconstructed using Astonish with attenuation correction.

Conclusions
When images were reconstructed using Astonish without attenuation correction, this study demonstrated statistically significant improvements in perfusion image quality. Furthermore, diagnostic certainty was unchanged and there was no loss in diagnostic accuracy when half-count data was reconstructed using Astonish. Note normalcy and cardiac catheterization were used as the gold standard.

When full-count and half-count data were reconstructed using Astonish with scatter and attenuation correction, this study demonstrated a significant increase in normalcy and specificity with no significant loss in sensitivity.

These data demonstrate that the use of Astonish technology, with or without attenuation correction, improves image quality and may be applied to reduced acquisition time studies. The ability to reduce imaging times can help lead to reduced patient discomfort, reduced likelihood of patient motion, and improved laboratory throughput and improved laboratory efficiency. Alternatively, absorbed radiation doses can be reduced by injecting less activity and imaging for standard imaging times.

The trial results on stress-only imaging demonstrate that perfusion and gated imaging can be performed on half-count data with high diagnostic accuracy and acceptable image quality. Stress only imaging can increase laboratory efficiency by eliminating the need for rest imaging. Performing studies using stress-only can increase patient acceptance, further reduces radiation doses (compared to stress/rest half dose imaging), and improves laboratory efficiency.

Astonish references
  1. Carmelo CV, Heller GV, Bateman TM, et al. A multicenter evaluation of a new post-processing method with depth-dependent collimator resolution applied to full-time and half-time acquisitions without and with simultaneously acquired attenuation correction. JNucl Cardiol 2009: 16 #5: 714-725
  2. Bateman TM, Heller GV, McGhie AI, et al. Multicenter investigation comparing a highly efficient half-time stress-only attenuation correction approach against standard rest-stress Tc-99m SPECT imaging. J Nucl Cardiol 2009; 16 #5: 726-735


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White Paper
Astonish, Cardiac, FBP reconstruction, image quality, myocardial perfusion, Perfusion
 

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