Characterization of attenuation and respiratory motion artifacts and their influence on SPECT MP image evaluation using a dynamic phantom assembly with variable cardiac defects.

BACKGROUND: A phantom assembly that simulates the respiratory motion of the heart was used to investigate artifacts and their impact on defect detection. METHODS: SPECT/CT images were acquired for phantoms with and without small and large cardiac defects during normal and deep breathing, and also at four static respiratory phases. Acquisitions were reconstructed with and without AC, and with misalignment of transmission and emission scans. A quantitative analysis was performed to assess artifacts. Two physicians reported on defect presence or absence and their results were evaluated. RESULTS: All large defects were correctly reported. Attenuation reduced uptake in the basal LV walls, increasing FN physicians' reports for small defects. Respiratory motion reduced uptake mainly in the anterior and inferior walls increasing FP and FN reports on images without and with small defects, respectively. Artifacts due to misalignment between CT and SPECT scans in normal breathing phantoms did not influence the physicians' reports. CONCLUSIONS: Attenuation and respiratory motion correction should be applied to reduce artifacts before reporting on small defects in deep breathing conditions. Artifacts due to misalignment between CT and SPECT scans do not affect defect detection in normal breathing when the LV is co-registered in SPECT and CT images prior to AC.

Impact of respiratory motion correction on SPECT myocardial perfusion imaging using a mechanically moving phantom assembly with variable cardiac defects.

BACKGROUND: The aim of this study was to determine the impact of respiratory motion correction on SPECT MPI and on defect detection using a phantom assembly. METHODS: SPECT/CT data were acquired using an anthropomorphic phantom with inflatable lungs and with an ECG beating and moving cardiac compartment. The heart motion followed the respiratory pattern in the cranio-caudal direction to simulate normal or deep breathing. Small or large transmural defects were inserted into the myocardial wall of the left ventricle. SPECT/CT images were acquired for each of the four respiratory phases, from exhale to inhale. A respiratory motion correction was applied using an image-based method with transformation parameters derived from the SPECT data by a non-rigid registration algorithm. A report on defect detection from two physicians and a quantitative analysis on MPI data were performed before and after applying motion correction. RESULTS: Respiratory motion correction eliminated artifacts present in the images, resulting in a uniform uptake and reduction of motion blurring, especially in the inferior and anterior regions of the LV myocardial walls. The physicians' report after motion correction showed that images were corrected for motion. CONCLUSIONS: A combination of motion correction with attenuation correction reduces artifacts in SPECT MPI. AC-SPECT images with and without motion correction should be simultaneously inspected to report on small defects.

Diagnostic sensitivity of SPECT myocardial perfusion imaging using a pumping cardiac phantom with inserted variable defects.

BACKGROUND: The diagnostic sensitivity of various SPECT MPI procedures was assessed using a pumping cardiac phantom with variable defects inserted in the myocardial wall of the left ventricle. METHODS AND RESULTS: A diagnostic evaluation of 142 myocardial defects was performed. A diagnosis blinded to prior-known conditions was compared to the known defects severity (transmural, subendocardial) and defects position within the myocardial wall of the left ventricle (apical, anterior, inferior) for three body types (average male, large male, large female). Non-attenuation corrected, attenuation corrected and gated SPECT MPI were performed. The diagnostic sensitivity was improved when applying attenuation correction or gating techniques to identify subendocardial defects in the inferior, anterior and apical segments of the myocardial wall of the left ventricle for all three body types. Transmural defects could be identified without any attenuation correction or gating. CONCLUSIONS: The diagnostic sensitivity was improved when applying AC or GSPECT techniques.

Clinical significance of myocardial perfusion abnormalities in patients with varying degree of coronary artery stenosis.

OBJECTIVES: (1) To identify myocardial perfusion abnormalities in a cohort of patients having coronary artery disease (CAD) risk factors, with either suspected or clinical evidence of ischaemic heart disease (IHD), and with varying degree of coronary artery stenosis. (2) To evaluate the clinical significance of the extent and severity of perfusion abnormalities assessed by myocardial perfusion scintigraphy (MPS) in relation to the anatomical location of coronary stenosis demonstrated by five-vessel selective coronary angiography (SCA). METHODS: One hundred and thirty-eight patients (106 male, 32 female) with suspected or clinical evidence of IHD underwent diagnostic evaluation at the Central Hospital of Nicosia, between November 2002 and August 2003. The diagnostic work-up included clinical examination, exercise tolerance test, SCA and myocardial perfusion scintigraphy (MPS) using either Tl chloride or Tc-tetrofosmin. RESULTS: Based on the results of SCA, patients were divided into five groups on the basis of stenosis as cross-sectional area of coronary artery lumen and its haemodynamic significance, ranging from group 1=less than 50% coronary stenosis to group 5=100% stenosis (occlusion). Nine of 11 (40.9%) patients with angiographically normal coronary arteries (group 1) had moderate inducible reversible ischaemia on MPS and 9/47 (19.1%) patients with insignificant coronary stenosis (less than 75% stenosis=group 2) had fixed perfusion defects, compatible with previous myocardial infarction. The extent of perfusion abnormalities in post-stress MPS patients from group 2 was not found to be statistically significant (P>0.05) when compared to patients belonging to groups 3, 4 and 5. However, the extent of perfusion abnormalities between patients from group 2, when compared to groups 3, 4 and 5 demonstrated significant statistical difference (P<0.05) on post-rest MPS studies. Furthermore, there was no significant statistical correlation between anatomical location of coronary stenosis and severity of perfusion abnormalities in the corresponding myocardial segments. CONCLUSION: Patients with CAD risk factors, and coronary arteries with insignificant stenosis on angiography, may demonstrate inducible reversible myocardial ischaemia. This is suggestive of coronary endothelial dysfunction. Patients with insignificant coronary artery stenosis and no previous history of adverse coronary events may demonstrate features of previous myocardial infarction on MPS. The severity of perfusion defects demonstrated by MPS may be independent of the anatomical location of coronary artery stenosis.