Development and validation of a patient-tailored dose regime in myocardial perfusion imaging using conventional SPECT

Abstract

BackgroundThe decreasing image quality in heavier patients can be compensated by administration of a patient-specific dose in myocardial perfusion imaging (MPI) using a cadmium zinc telluride-based SPECT camera. Our aim was to determine if the same can be achieved when using a conventional SPECT camera.Methods148 patients underwent SPECT stress MPI using a fixed Tc-99m tetrofosmin tracer dose. Measured photon counts were normalized to administered tracer dose and scan time and were correlated with body weight, body mass index, and mass per length to find the best predicting parameter. From these data, a protocol to provide constant image quality was derived, and subsequently validated in 125 new patients.ResultsBody weight was found to be the best predicting parameter for image quality and was used to derive a new dose formula; Aadmin (MBq) = 223·body weight (kg)0.65/Tscan (min). The measured photon counts decreased in heavier patients when using a fixed dose (P < .01) but this was no longer observed after applying a body-weight-dependent protocol (P = .20).ConclusionsApplication of a patient-specific protocol resulted in an image quality less depending on patient’s weight. The results are most likely independent of the type of SPECT camera used, and, hence, adoption of patient-specific dose and scan time protocols is recommended.

Single Photon Emission Computed Tomography (SPECT) Myocardial Perfusion Imaging Guidelines: Instrumentation, Acquisition, Processing, and Interpretation

“…Weight-based, radiotracer-dose algorithms can also reduce radiation dose compared to fixeddose protocols. 186 The tradeoff between patient dose and acquisition time must be considered on an individual basis taking into account the scanners used. Newer generation imaging equipment, including high-efficiency CZT cameras, 187 Anger cameras 186 with improved sensitivity and advanced post-processing solutions-such as iterative reconstruction, resolution recovery, and noise reduction-provide flexible options for reducing radiotracer dose, yet preserving image quality.…”

Effect of a patient-specific minimum activity in stress myocardial perfusion imaging using CZT-SPECT: Prognostic value, radiation dose, and scan outcome

“…However, as demonstrated in our previous studies, we can assume that introduction of patient-specific activity or scan-time protocols as derived for conventional SPECT cameras may allow radiation dose reductions without affecting diagnostic outcomes in these cameras as well. 12,39 …”

“…In our previous studies, we demonstrated that a body-weight dependent activity protocol not only resulted in an improved image quality but also in the possibility to further lower the tracer activity. 11,12 Prognostic evidence that such a low bodyweight dependent activity protocol with limited scan time does not affect diagnostic outcome is lacking. Hence, our aim was to compare the standard fixedactivity protocol (FAP) and patient-specific low-activity protocol (PLAP) with regard to percentage of scans interpreted as normal, radiation dose, and prognostic value for CZT-SPECT MPI.…”

The very hungry caterpillar and the ongoing effort to reduce radiation in myocardial perfusion scintigraphy: Have we become the beautiful butterfly?

“…Thus far, previous studies have shown that body-weight dependent activity protocols not only resulted in an improved image quality but also in the possibility to further lower the tracer activity. 24,25 However, prognostic evidence that such a low body-weight dependent activity protocol with limited scan time does not affect diagnostic outcome was lacking.…”