Determination of Breast-Absorbed Dose Using Conjugated View Method in Patients Undergoing Perfusion Scan with Radiotracer 99mTc-sestamibi

Internal dosimetry in nuclear medicine is very important for assessing the benefits of the used method against its risks. The absorbed dose of injected radiopharmaceutical is determined by several different methods. The aim of this study was to determine the absorbed dose of the breast using the software Medical Internal Radiation Dose (MIRD) and to compare it with the computer-simulation software [quoted] in some authentic articles.
22 females were posed to gamma camera at intervals of 15, 60 and 90 minutes after injection of the radiopharmaceutical 99mTC-sestamibi, and scanned. Radiotracer based on activity was performed using conjugated-view method. The breast dose was calculated using MIRD formula. The quantitative data of dosimetry were analyzed via SPSS software.
Findings: The breast activity in 15, 60 and 90 minutes after injection of the radiopharmaceutical was calculated as 0.234 ± 0.076, 0.17± 0.053 and 0.134 ± 0.053 mCi, respectively. By drawing graphs of the activity over time using Excel software, we witnessed a decline of the graph. The average amount of radiopharmaceutical uptake by heart was then calculated as 3.065 ± 0.327 percent.
The results of this study were not in good agreement whit valid studies. So, the conjugated view method is not an accurate approach for organ activity quantification in myocardial perfusion scan.