Current status of stress myocardial perfusion imaging pharmaceuticals and radiation exposure in Japan: Results from a nationwide survey.

BACKGROUND: Ionizing radiation generated during medical imaging procedures is a matter of concern. However, the current status of radiopharmaceutical use in stress myocardial perfusion imaging (MPI) and the radiation exposure from these radiopharmaceuticals is unknown in Japan. METHODS AND RESULTS: A nationwide survey was conducted from June through July 2016. The questionnaires on the radiopharmaceuticals used and their administered doses during stress MPI were sent to 641 nuclear medicine facilities. The responses were collected from 431 facilities and the effective dose (ED) for an adult with standard body weight was calculated. Forty-three percent of the facilities used only 201TlCl, 35% used only 99mTc radiopharmaceuticals, and the remaining 22% used both. The two main reasons for using 201TlCl instead of 99mTc radiopharmaceuticals were "more familiarity with the usage of 201TlCl than 99mTc radiopharmaceuticals" and "apprehension about increasing the burden of physicians performing tracer injection twice." The mean ED was 14.0 ± 5.5 mSv (range, 3.9 to 25.2 mSv), which was higher than that reported in other countries. CONCLUSIONS: The ED of stress MPI radiopharmaceuticals in Japan is probably higher than the world standard because more than 50% of the facilities still use 201TlCl. We recommend revising the routine stress MPI protocol to reduce the effects of ionizing radiation.

Evaluation of Glucose Uptake and Uncoupling Protein 1 Activity in Adipose Tissue of Diabetic Mice upon ß-Adrenergic Stimulation.

PURPOSE: Regulation of metabolic activity in adipose tissue is of great concern for treating obesity. This study aimed to evaluate the adrenergic regulation of glucose uptake and the thermogenic program in adipose tissues in mouse models of both type 1 and 2 diabetes mellitus (DM). PROCEDURES: Male mice were treated with streptozotocin to induce type 1 (T1) DM, and obese ob/ob mice were used for the type 2 (T2) DM model. After selective ß3-adrenoreceptor stimulation by CL 316,243 (CL) treatment, 2-deoxy-D-[14C]glucose ([14C]DG) was administered to DM and corresponding control mice. Radioactivity and uncoupling protein 1 (UCP1) expression were measured and analyzed in adipose tissues. RESULTS: In T1DM, [14C]DG uptake in brown adipose tissue (BAT) decreased both at rest and upon CL stimulation, and UCP1 expression was preserved. However, CL treatment enhanced [14C]DG uptake without impairing UCP1 expression in inguinal white adipose tissue (iWAT). In this model, CL could not alter blood glucose levels. In T2DM mice, the blood glucose level was significantly lowered by CL treatment. There was no decrease in CL-induced [14C]DG uptake in BAT, and UCP1 expression was maintained. However, [14C]DG uptake was not increased in iWAT and no UCP1 expression was observed in iWAT (browning). CONCLUSIONS: The metabolic response against adrenergic stimulation varied depending on the type of adipose tissue and DM. This could be important for the therapeutic activation of adipose tissue metabolism in obese diabetic patients.

The Status of Stress Myocardial Perfusion Imaging Using 99mTc Pharmaceuticals in Japan: Results from a Nationwide Survey.

OBJECTIVES: To appropriately use one-day myocardial perfusion imaging (MPI) with 99mTc radiopharmaceuticals (i.e. to avoid shine-through artifacts), injection doses need to be optimized and dose ratios between the 1st and 2nd scans should be maintained at ≥ 3. However, the current state of practice in Japan is unclear. Thus, the aim of this study was to clarify the details of MPI protocols using 99mTc radiopharmaceuticals in Japan. METHODS: A nationwide survey was conducted in June and July 2016. Questionnaires about stress MPI protocols using 99mTc radiopharmaceuticals were sent to 641 nuclear medicine facilities. RESULTS: Responses were received from 246 facilities. One-day protocols were used in 97.1% of the facilities. The most common injection dose ratio was 2.5. Only 18.2% of facilities achieved the recommended injection dose ratio. Stress-only protocols were performed in only 1.7% of facilities; the primary reasons for not performing stress-only protocols were as follows: 1) "The reading-physician cannot interpret the image just after the first scan," and 2) "Preparation of radiopharmaceuticals and scan arrangements turn out to be complicated." CONCLUSION: Approximately 80% of nuclear medicine facilities do not follow the recommended injection dose ratio. Stress-only protocols are ideal, but are performed at very few facilities. Both optimization and standardization of stress MPI protocols using 99mTc radiopharmaceuticals are needed in Japan.

Optimal injected dose ratio of a very rapid 1-day protocol of myocardial perfusion imaging with cadmium-zinc-telluride single-photon emission tomography: simulation and phantom study.

OBJECTIVE: Cadmium-zinc-telluride detectors enable shorter acquisition durations in myocardial perfusion imaging (MPI), but the time interval of sequential scanning is still unchanged in clinical practice. We designed a very rapid 1-day protocol of MPI using cadmium-zinc-telluride single-photon emission tomography and evaluated the optimal dose ratio between two scanning acquisitions by means of simulations and phantom experiments. METHODS: We intended to perform a 1-day MPI within 140 min and simulate radioactivities in the second scan under various injected dose ratios. To apply this, a cardiac phantom was scanned with various radioactivities and scans were compared with a reference scan with the ideal tracer concentrations. RESULTS: In the stress-first protocol, the dose ratio 1 : 5 was enough to show the same regional percentage uptake compared with the reference. However, in the rest-first protocol, the regional percentage uptakes were higher than those of the reference image even with a 1 : 6 dose ratio. CONCLUSION: The injected dose ratio 1 : 5 is optimal in a stress-first rapid 1-day protocol. The rest-first protocol is not appropriate because a dose ratio greater than 1 : 6 is required to withdraw shine-through artifacts.