We have recently validated a new system (IQ-SPECT), able to reduce scan time to 1/4 compared to standard procedures in myocardial perfusion imaging (MPI). The system implements a multifocal collimator and a dedicated reconstruction software. We also demonstrated the feasibility of a 1/8 time protocol in a phantom study. It remains unclear whether such a dramatic reduction in acquisition time can be pursued also in clinical practice.
50 patients with suspected or diagnosed CAD underwent a two-days protocol MPI at rest and after a standard stress test. Images were acquired on a 2-headed gamma camera equipped with multifocal collimators and reconstructed with attenuation correction. The two acquisitions (6 and 12s/view) were sequentially performed both after stress and at rest. All images were read by 2 blinded observers to obtain summed stress (SSS), rest (SRS) and difference scores (SDS). Patients were evaluated both altogether and subdividing them into two groups on the basis of body mass index (group 1: BMI<25, group 2: BMI≥25).
Comparing 6s/view and 12s/view, no significant differences were found in mean SSS (5.68 ± 7.36 vs 5.56 ± 6.91), SRS (4.43 ± 6.72 vs 3.36 ± 4.31)and SDS (1.93 ± 4.62 vs 2.60 ± 4.85). Also considering the individual territories of distribution, the differences were not significant. By subdividing the patients into two groups, group 1 showed no differences between the two acquisitions. Conversely, in group 2 SSS and SRS were significantly higher with a 6s/view (8.45 ± 5.3 and 5.6 ± 2.4, respectively, p<0.05) than with a 12s/view acquisition time (5.25 ± 4.36 and 4.12 ± 3.2, respectively, p<0.05). SDS values did not show any significant differences.
MPI with IQ-SPECT system can be acquired in 1/8 of standard time in patients with normal BMI. This could also prospectively lead to a similar reduction in administered dose. In the other patients such a reduction in acquisition time appears excessive.