Intra-patient reproducibility of myocardial SPECT imaging with 201Tl.

ABSTRACT

BACKGROUND: To define the physical and clinical reproducibility of (201)Tl myocardial perfusion SPECT (MPS), this study assesses the variation between two repeated rest (201)Tl MPS with repositioning only, with a two-hour time interval and with phantom measurements as a reference. METHODS: Three anthropomorphic thorax phantoms were filled with (201)Tl. For each phantom five repeated (201)Tl MPS were obtained. In addition, in 20 patients repeated (201)Tl rest-MPS and in 26 patients early and delayed (201)Tl rest-MPS were performed. Quantitative analysis was done using MunichHeart. Statistical methods were used to calculate variability. Visual analysis was performed by 2 independent observers. RESULTS: The average variation between repeated phantom MPS was 0.5% (95% confidence interval (CI) -0.4% to 1.4%). For patient scans this was -5.0% (95% CI -2.5% to -7.5%) and between early and delayed (201)Tl MPS -15.5% (95% CI -11.7% to -19.3%). Visual assessment revealed no clinical significant differences between rest (201)Tl and repeated or delayed (201)Tl MPS. CONCLUSIONS: Repositioning in phantom (201)Tl MPS does not cause significant variation. Repeated (201)Tl MPS in patients shows 5.0% decrease of (201)Tl in 30 minutes, which increases to 15% during a two-hour time interval without quantitative or visual regional differences. This decrease indicates a time-related washout of (201)Tl, but does not change clinical diagnosis.