Non-Uniform Attenuation Correction for Myocardial SPET Using Two Gd-153 Line Sources^[*]

 

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Summary

Aim: This study deals with the effect of the non-uniform attenuation correction method on myocardial tomograms of normal subjects. Method: A total of 35 patients (20 female, 15 male) without evidence of cardiac disease underwent SPET with and without attenuation correction using a dual head camera and transmission data obtained by two scanning Gd-153 line sources after administration of 400 MBq Tc-99m-tetrofosmin. Results: In non-corrected (NC) stress studies the lowest count rates were found in the inferior segments with mean differences in count rates between maxima and minima of 35.8 ± 10.8%. In attenuation corrected (AC) images the respective segmental differences averaged only 20.9 ± 3.3% and the images did not show significant count deficiency in the inferior segments. The effects of correction revealed to be sex dependent, but independent of body mass on average. Conclusion: AC using the above technique significantly reduces the variability of count rate distribution in normal subjects and improves the preconditions for accurate diagnostic evaluation of coronary artery disease using SPET.

Zusammenfassung

Ziel: Ziel der Studie war, die non-uniforme Schwächungskorrektur und deren Auswirkung auf die Variabilität der myokardialen Repräsentation bei der SPET von Normalpersonen zu untersuchen. Methode: 35 Patienten (20 w, 15 m) wurden nach i.v. Injektion von 400 MBq Tc-99m-Tetrofosmin mit und ohne Schwächungskorrektur unter Verwendung einer 2-Kopf-Kamera mit je einer linear bewegten Gd-153-Linienquelle untersucht. Ergebnisse: Bei den nichtkorrigierten (NC) Aufnahmen fand sich die niedrigste Impulsrate im Bereich der inferioren Wand. Die durchschnittlichen Differenzen hinsichtlich der Impulsrate der maximal und minimal repräsentierten Wandareale betrugen 35.9 ± 10.8%. Bei schwächungskorrigierten (AC) Aufnahmen betrugen die entsprechenden Differenzen nur 20,9 ± 3.3%; die Tomogramme zeigten keine signifikante Minderrepräsentation der inferioren Wandsegmente. Die Auswirkungen der Korrektur erwiesen sich als geschlechts-, jedoch nicht als körpermasseabhängig. Schlußfolgerung: Schwächungskorrektur nach der o.g. Methode reduziert die interindividuelle Variabilität normaler Tomogramme und bewirkt eine genauere Repräsentation der Aktivitätsverteilung.

^* Dedicated to Prof. L. E. Feinendegen on the occasion of his 70th birthday

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