The impact of adenosine pharmacologic stress combined with low-level exercise in patients undergoing myocardial perfusion imaging (BIWAKO adenosine-Ex trial).

BACKGROUND: The combination of adenosine infusion with low-level exercise has become a common approach for inducing stress during stress myocardial perfusion imaging (MPI). We investigated stress MPI performed by combined low-level exercise and adenosine infusion. This combined protocol can decrease adverse reactions and reduce the effect of scattered rays from the liver. METHODS AND RESULTS: Subjects were clinically referred for a 53-min rest-stress Tc-99m Sestamibi MPI procedure using BIWAKO PROTOCOL. Ninety-eight patients (44.5%) underwent adenosine infusion with ergometer exercise testing and 122 patients (55.5%) underwent adenosine infusion without exercise testing. We evaluated the liver/heart (L/H) uptake ratio, background activity in the upper mediastinum, and adverse reactions. RESULTS: The L/H ratio and background activity were lower in the adenosine-exercise group than in the adenosine-non-exercise group (1.8 ± 0.54 vs. 2.1 ± 0.62, P < 0.0056; 43.1 ± 12.2 vs. 61.5 ± 15.4, P < 0.0001). The adenosine-exercise group had fewer adverse reactions than the adenosine-non-exercise group (11.2 vs. 19.7%). All of the adverse reactions were minor, with the exception of severe back pain in one case. The incidence of adverse reactions in our study was lower than that in previous studies for unknown reason. CONCLUSION: Adenosine infusion in combination with low-level exercise seems to result in higher-quality images and fewer adverse reactions than adenosine infusion without exercise. The combined protocol decreases adverse reactions and improves the quality of myocardial perfusion images by decreasing background activity.

Countermeasures against physical motion in schoolchildren requiring no sedation during rest and stress myocardial perfusion imaging with technetium-99m-tetrofosmin.

For children, cardiac nuclear medicine imaging has not been widely used because of problems of physical motion, even in schoolchildren who require no sedation. In this study, rest-stress myocardial perfusion imaging (MPI) with technetium-99m-tetrofosmin (Tc-99m TF) was performed with the use of a Vac-Loc cushion, a patient immobilizer commonly used for radiotherapy, for immobilizing school-age patients. The immobilizer attenuated the gamma radiation by 6%. By visual assessment, physical motion-related artifacts were markedly improved in images acquired with the immobilizer, compared to those without. In the assessment of image reproducibility with the immobilizer, taking the reproducibility as 2.5Σ + 0.7σ, there were deviations of 4.45, 5.28, and 3.28 mm along the X-, Y-, and Z-axes, respectively, demonstrating a high reproducibility and a negligible rest-stress position error. It is suggested that for radiotherapy, the immobilizer could expand the versatility of MPI while allowing only minimal physical motion in children.

New protocol of myocardial SPECT imaging with technetium-99m sestamibi for reducing the time interval between rest and adenosine stress phases.

We have developed a new protocol of myocardial perfusion-gated single-photon emission computed tomography (SPECT), by use of technetium-99m sestamibi (MIBI), in which SPECT imaging at rest followed by SPECT imaging after adenosine with low level ergometer stress can be conducted by use of the Monzen position within a shortened total testing time of 1 h or less. The study group consisted of 137 patients who underwent this new imaging protocol. The diagnostic quality of the images was as good as that of images obtained with the conventional method (30-60 min after the injection of MIBI). The SPECT image quality for the 137 patients was evaluated, and the percentages of images rated as excellent, good, fair, and poor were 65.3, 27.4, 5.8, and 1.5% for the rest image, and 68.2, 21.9, 8.4, and 1.5% for the stress image, respectively. The shortened total testing time reduced the physical and mental burden on the patient compared with that of conventional myocardial perfusion imaging. Because this technique allows us to perform rest and stress myocardial imaging within a short period, it is expected to be very useful in the clinical setting.

[Evaluation of a New Protocol for Two-isotope (123)I-BMIPP/(99m)Tc-TF Single Photon Emission Computed Tomography (SPECT) to Detect Myocardial Damage within One Hour].

Objective The present study aimed at establishing a new protocol using both (99m)Tc-Tetrofosmin (TF) and (123)I-BMIPP SPECT to detect myocardial damage within one hour. Methods Initial (123)I-BMIPP SPECT was immediately followed by (99m)Tc-TF SPECT. The influence of (123)I scattered rays on (99m)Tc energy windows set at 15% and 10% were measured using an RH-2 phantom. Participants in the study were patients with heart diseases who had provided written informed consent to undergo the new protocol. The patients maintained the MONZEN position throughout the procedure and an injection syringe was attached to the left arm for (99m)Tc-TF injection during (123)I-BMIPP SPECT. Results & Discussion The phantom study showed only slight (123)I contamination of (99m)Tc at the 10% window setting. The new method separated the (123)I and (99m)Tc energy windows well and neither crosstalk nor scatter correction were needed. Images obtained from dual (simultaneous) acquisition were contaminated, whereas contamination and influence of scattered rays were absent in images obtained by use of the new protocol. These images were thus useful for clinical diagnosis. Conclusion The new protocol is more convenient for patients and might improve the efficiency of detecting myocardial damage.

Reduction of infracardiac intestinal activity by a small amount of soda water in technetium-99m tetrofosmin myocardial perfusion scintigraphy with adenosine stress.

BACKGROUND: In technetium (Tc)-99m myocardial perfusion imaging (MPI), intestinal activity often interferes with the assessment of myocardial perfusion of the inferior wall. We examined whether a small amount of soda water prevents intestinal activity and improves image quality of the inferior wall in Tc-99m tetrofosmin MPI. METHODS AND RESULTS: Ninety-five patients referred for 1-day rest/stress Tc-99m tetrofosmin MPI were assigned to one of two groups automatically, according to the date when they underwent MPI: the soda water group (n = 63) ingested 100 mL soda water just before image acquisition after adenosine stress, and the control group (n = 32) underwent no intervention. The frequency of intestinal activity was assessed visually on planar images. The inferior myocardial wall and the abdominal activity adjacent to the myocardium were assessed quantitatively on three different planar images during stress, and the mean inferior wall-to-abdomen (I/A) count ratio was calculated. The frequency of intestinal activity was 69.8% in the soda water group, and 90.6% in the control group (P = .038). The I/A count ratio was significantly higher in the soda water group than in the control group (1.98 +/- 0.51 vs 1.50 +/- 0.35, respectively, P < .0001, +/- SD). CONCLUSIONS: The intake of 100 mL of soda water improves intestinal activity and improves the image quality of the inferior wall.

Exploring a technique for reducing the influence of scattered rays from surrounding organs to the heart during myocardial perfusion scintigraphy with technetium-99m sestamibi and technetium-99m tetrofosmin.

We have devised a new position (Monzen position) which can suppress the influence of scattered rays from surrounding organs (liver, etc.) when conducting myocardial imaging. Unlike the conventional techniques, which require a waiting period of 30-60 minutes before imaging can be started after the infusion of technetium-99m sestamibi or technetium-99m tetrofosmin, this position allows single-photon emission tomography to be started about 5-10 minutes after the infusion of the tracer. Therefore, with this technique the total time required for imaging is reduced and consequently the physical and mental burden of the patient is also reduced. Furthermore, the number of patients who can receive this test at any facility can be increased. This position may also be applicable in myocardial scintigraphy using some other tracers.