Effect of attenuation correction on lesion detection using a hybrid PET system

Chiraporn Tocharoenchai, Benjamin Tsui, Eric Frey, Wen Tung Wang

Research output: Contribution to journalArticle

Abstract

Objective: The purpose of this study was to investigate the effect of attenuation correction (AC) on lesion detection for a hybrid PET system. Material and Method: Experimental list-mode data were acquired from hot spheres inside a uniform cylindrical phantom with an elliptical cross-section using a Siemens E.CAM+ dual-camera hybrid PET system. Spheres with inner diameters of 0.8- and 1-cm and the cylindrical phantom were filled with F-18 to simulate lesions with lesion-to-background (L/B) ratios of 14:1 and 8:1, respectively, found in clinical PET studies. The list-mode data of each sphere size were regrouped into sinograms with peak-to-peak energy window settings at 30% and 20% for the 0.8- and 1-cm diameter lesion, respectively. They were then rebinned using the single slice rebinning method. Attenuation correction was applied assuming uniform attenuation. The sinograms with and without AC were reconstructed using 5 iterations of OS-EM algorithm with 8 angles/subset and postfiltered with a Butterworth filter with n = 5 and fc = 0.52 cycles/cm. Human observer performance study and localization receiver operating characteristic (LROC) analysis were used to evaluate the reconstructed images for maximum lesion detection. Average areas under the LROC curves (ALROC) across 8 observers obtained with and without AC were determined. The null hypothesis that there was no difference between with AC and without AC was tested using a two-tailed t-test with 95% confidence interval. Results: The results indicated that for the 0.8-cm lesion with 14:1 L/B ratio, the ALROC decreases from 0.66 to 0.62 when AC is applied as compared to without AC and from 0.69 to 0.63 for the 1.0-cm lesion with 8:1 L/ B ratio, but no statistical significant difference (p > 0.05). Conclusion: The authors conclude that for a phantom with hot lesions embedded in a uniform background, AC decreases lesion detectability compared to without AC using a hybrid PET system for small lesion sizes.

Original languageEnglish (US)
Pages (from-to)96-102
Number of pages7
JournalJournal of the Medical Association of Thailand
Volume88
Issue number1
StatePublished - Jan 2005

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ROC Curve
Area Under Curve
Confidence Intervals
Clinical Studies

Keywords

  • Attenuation correction
  • Hybrid PET
  • LROC study

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Effect of attenuation correction on lesion detection using a hybrid PET system. / Tocharoenchai, Chiraporn; Tsui, Benjamin; Frey, Eric; Wang, Wen Tung.

In: Journal of the Medical Association of Thailand, Vol. 88, No. 1, 01.2005, p. 96-102.

Research output: Contribution to journalArticle

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abstract = "Objective: The purpose of this study was to investigate the effect of attenuation correction (AC) on lesion detection for a hybrid PET system. Material and Method: Experimental list-mode data were acquired from hot spheres inside a uniform cylindrical phantom with an elliptical cross-section using a Siemens E.CAM+ dual-camera hybrid PET system. Spheres with inner diameters of 0.8- and 1-cm and the cylindrical phantom were filled with F-18 to simulate lesions with lesion-to-background (L/B) ratios of 14:1 and 8:1, respectively, found in clinical PET studies. The list-mode data of each sphere size were regrouped into sinograms with peak-to-peak energy window settings at 30{\%} and 20{\%} for the 0.8- and 1-cm diameter lesion, respectively. They were then rebinned using the single slice rebinning method. Attenuation correction was applied assuming uniform attenuation. The sinograms with and without AC were reconstructed using 5 iterations of OS-EM algorithm with 8 angles/subset and postfiltered with a Butterworth filter with n = 5 and fc = 0.52 cycles/cm. Human observer performance study and localization receiver operating characteristic (LROC) analysis were used to evaluate the reconstructed images for maximum lesion detection. Average areas under the LROC curves (ALROC) across 8 observers obtained with and without AC were determined. The null hypothesis that there was no difference between with AC and without AC was tested using a two-tailed t-test with 95{\%} confidence interval. Results: The results indicated that for the 0.8-cm lesion with 14:1 L/B ratio, the ALROC decreases from 0.66 to 0.62 when AC is applied as compared to without AC and from 0.69 to 0.63 for the 1.0-cm lesion with 8:1 L/ B ratio, but no statistical significant difference (p > 0.05). Conclusion: The authors conclude that for a phantom with hot lesions embedded in a uniform background, AC decreases lesion detectability compared to without AC using a hybrid PET system for small lesion sizes.",
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