Abstract
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Introduction: Quantitative Perfusion SPECT (QPS) is used in Myocardial Perfusion Imaging (MPI) for segmentation, quantification, analysis, and display of short-axis myocardial perfusion ungated SPECT images. Images undergo segmentation followed by polar sampling. A polar map is generated as a 2D myocardium representation which displays a 17-segment model. This is normalized to facilitate comparison with other polar maps from a normal database. The normal databases are acquired with similar imaging techniques specific to male and female populations with a low likelihood of disease. These normalized patients are compared to the acquired patient data displaying the severity in the individual's polar maps and assisting in producing the attenuation maps. Breast and diaphragm attenuation artifacts (AA) are the most common attenuation types seen in MPI. Breast AA is typically found in female patients and localized in the anterior wall and septum, while diaphragmatic AA can cause artifacts in the inferior wall. However, these perfusion patterns are not mutually exclusive and can be found in male and female genders. This research uses a case study to show the benefits of using both male and female normal databases in the quantification of an MPI study in an obese male patient.
Methods: A male patient weighing 138kg, with a BMI of 49kg/m2 underwent an MPI study. This patient received a dose of 14.3mCi Tc-99m Tetrofosmin at rest, with SPECT acquired 30 minutes later, followed by a Regadenoson stress per manufacturer instructions with 44.2mCi Tc-99m Tetrofosmin. Supine stress imaging (with and without gating) was completed 1-hour post stress injection. Both images were acquired on a dual-head gamma camera with parallel hole, low energy, high-resolution collimators. The images were acquired using a 128x128 matrix with a SPECT acquisition of 16 stops per head acquired for 25 seconds per stop. Images were reconstructed using 3D iterative reconstruction and quantified using Cedars Sinai QPS. The patient's images were interpreted by a board-certified radiologist. A retrospective analysis including both the male and female Cedars Sinai QPS normal databases was performed to assess the effect on the reported defect.
Results: The initial reported findings included a small, fixed defect in the mid-distal anteroseptal wall most likely due to AA and no evidence of stress-induced ischemia (Fig. 1). Quantification was performed for the rest and stress images using the male and female databases in QPS (matched to imaging/reconstruction technique). Using the male normal database, the polar maps show reversibility in segments 7, 9, 13, and 17 (Fig 2). In the 17-segment model, these represent the mid anterior, apical anterior, apex, and mid inferoseptal regions. Using the female normal database, the polar maps show reversibility in segments 9 and 10 (Fig 3). In the 17-segment model, these represent the mid inferoseptal and mid inferior regions.
Conclusions: Quantification of the images using male and female normalized QPS data showed a numerical difference when processing the same patient. Using the female normal database for comparison, reversibility was detected in the anterior wall regions which can correspond to breast AA. When using the male normal database, the reversibility was noted in the inferior wall which can correspond to diaphragmatic AA. By using the gendered normal databases for comparison in this obese male patient, a more confident assessment of artifactual contribution to perfusion abnormality was obtained. This patient did not have other cardiac procedures performed since his MPI. Gathering data on multiple patient types could help determine if this technique could be utilized further. Further research could explore if gender should be specified when body habitus is utilized and could explore the body habitus of patients included in the normal databases.
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