Can carbonated lime drink intake prior to myocardial perfusion imaging with Tc-99m MIBI reduce the extracardiac activity that degrades the image quality and leads to fallacies in interpretation?

During myocardial perfusion imaging with Tc-99m sestamibi, intestinal and hepatic radiotracer activity commonly interfere with visualization of the inferior wall of the myocardium leading to difficulties in interpretation. This study was undertaken to assess if carbonated lime drink ingestion prior to imaging prevents the said interference and improves the quality of images. The study group comprised 33 consecutive patients including 26 males (age range: 30–80 years) and 7 females (42–62 years) who were referred for myocardial perfusion imaging. Of 33 patients, 21 (18 males, 3 females) were imaged at rest, 5 patients (3 males, 2 females) underwent physical stress, and 7 patients (5 males, 2 females) had pharmacological stress with adenosine. Five to 10 minutes after intravenous injection of 296 to 444 MBq (8–12 mCi) Tc-99m MIBI, anterior, and left anterior oblique (LAO) 45 degree planar views were acquired with a gamma camera using LEHR collimator. Each view was acquired for 100 seconds in a 256 × 256 matrix in all patients. Thereafter each patient was administered about 250 mL of a carbonated lime drink and repeat views were acquired within 5 minutes with the same parameters. Quantitative assessment of counts in the inferior wall of myocardium (M) to those in adjacent abdomen (A) was performed on both pre- and postintervention studies by drawing an ROI of about 50 ± 5 pixels. M/A ratios were recorded for each patient in both the groups. The student t test was performed to evaluate the significance of difference between pre- and postintervention images. P < 0.05 was considered significant. All patients underwent myocardial perfusion single photon emission computed tomography. It was found that the inferior wall of the myocardium was better visualized, and there was no interference from gut or hepatic tracer activity in postintervention planar and single photon emission computed tomography reconstructed views as compared with preintervention images in all patients. The M/A ratio expressed as mean ± SD was significantly higher in the postintervention group, viz. 2.19 ± 0.71 in the anterior and 2.07 ± 0.70 in the LAO45 views as compared with those of preintervention values of 1.50 ± 0.59 in the anterior and 1.41 ± 0.49 in the LAO 45 views, respectively (P < 0.001). We conclude that intake of carbonated lime drink is a simple and an effective technique to improve the image quality of the inferior wall of the myocardium on myocardial perfusion imaging with Tc-99m MIBI. This technique may also help in reducing the time interval between injection of radiotracer and imaging, which is otherwise delayed in routine practice.