ABSTRACT
BACKGROUND: The coronary calcium score (CCS) provides independent diagnostic and prognostic information on top of myocardial perfusion imaging (MPI) in patients suspected for coronary artery disease, but requires an additional computed tomography (CT) scan. OBJECTIVE: We investigated the accuracy and inter-reader reproducibility of visual estimation of the CCS on the CT used for attenuation correction. METHODS: 250 patients undergoing single photon emission computed tomography MPI and Agatston CCS were included. The CCS was also visually estimated on the CT for attenuation correction by two separate readers blinded to the Agatston CCS, and was categorized into a six-point scale (0, 1-10, 11-100, 101-400, 401-1000 and > 1000). RESULTS: The median Agatston CCS was 82 [25th-75th percentile: 0-562], with a range from 0 to 7287. Of the visually estimated CCS, 60% (reader 1) and 65% (reader 2) were classified correctly into the 6 categories. 93% (reader 1) and 88% (reader 2) of the visually estimated CCS did not vary by more than one category from the Agatston CCS. The intraclass correlation coefficient for agreement between the Agatston CCS and the visually estimated CCS was 0.95 for reader 1 and 0.94 for reader 2. The intraclass correlation coefficient for inter-reader reproducibility of the visually estimated CCS was 0.96. CONCLUSION: The CCS can be accurately estimated on the CT for attenuation correction, as high agreement is demonstrated with the Agatston CCS and inter-reader reproducibility is excellent. If no traditional Agatston CCS is performed, the degree of atherosclerosis should be assessed by means of estimating CCS on the CT for attenuation correction.
Subject(s)
Computed Tomography Angiography , Coronary Angiography/methods , Coronary Artery Disease/diagnostic imaging , Coronary Vessels/diagnostic imaging , Multidetector Computed Tomography , Myocardial Perfusion Imaging/methods , Single Photon Emission Computed Tomography Computed Tomography , Vascular Calcification/diagnostic imaging , Aged , Coronary Artery Disease/physiopathology , Coronary Circulation , Coronary Vessels/physiopathology , Female , Humans , Male , Middle Aged , Observer Variation , Predictive Value of Tests , Prognosis , Reproducibility of Results , Severity of Illness Index , Vascular Calcification/physiopathologyABSTRACT
BACKGROUND: The decreasing image quality in heavier patients can be compensated by administration of a patient-specific dose in myocardial perfusion imaging (MPI) using a cadmium zinc telluride-based SPECT camera. Our aim was to determine if the same can be achieved when using a conventional SPECT camera. METHODS: 148 patients underwent SPECT stress MPI using a fixed Tc-99m tetrofosmin tracer dose. Measured photon counts were normalized to administered tracer dose and scan time and were correlated with body weight, body mass index, and mass per length to find the best predicting parameter. From these data, a protocol to provide constant image quality was derived, and subsequently validated in 125 new patients. RESULTS: Body weight was found to be the best predicting parameter for image quality and was used to derive a new dose formula; A admin (MBq) = 223·body weight (kg)(0.65)/T scan (min). The measured photon counts decreased in heavier patients when using a fixed dose (P < .01) but this was no longer observed after applying a body-weight-dependent protocol (P = .20). CONCLUSIONS: Application of a patient-specific protocol resulted in an image quality less depending on patient's weight. The results are most likely independent of the type of SPECT camera used, and, hence, adoption of patient-specific dose and scan time protocols is recommended.
Subject(s)
Coronary Artery Disease/diagnostic imaging , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Myocardial Perfusion Imaging/instrumentation , Organophosphorus Compounds/administration & dosage , Organotechnetium Compounds/administration & dosage , Tomography, Emission-Computed, Single-Photon/instrumentation , Aged , Body Weight , Contrast Media/administration & dosage , Coronary Artery Disease/physiopathology , Drug Administration Schedule , Equipment Design , Equipment Failure Analysis , Female , Gamma Cameras , Humans , Image Enhancement/instrumentation , Image Interpretation, Computer-Assisted/instrumentation , Male , Myocardial Perfusion Imaging/methods , Patient-Centered Care/methods , Patient-Specific Modeling , Radiopharmaceuticals/administration & dosage , Reproducibility of Results , Sensitivity and Specificity , Tomography, Emission-Computed, Single-Photon/methodsABSTRACT
We describe a 45-year-old male survivor of Hodgkin lymphoma, treated with mediastinal radiation therapy, referred for single-photon emission computed tomography (SPECT) myocardial perfusion imaging in combination with coronary artery calcium (CAC) scoring. SPECT demonstrated a reversible moderate-sized lateral perfusion defect, and the CAC score was zero. A calcium score of zero markedly reduces the probability of having coronary artery disease (CAD) and is associated with a very low risk of future cardiovascular events. However, a CAC score of zero does not completely rule out obstructive CAD. In this case, invasive coronary angiography revealed three-vessel CAD with left main involvement. Whether mediastinal radiation therapy in general is associated with CAD without accompanying CAC is yet unclear.
