Dipyridamole-thallium/sestamibi before vascular surgery: A prospective blinded study in moderate-risk patients

AbstractPurpose: This study assessed in a prospective, blinded fashion whether a reversible defect on dipyridamole-thallium (DTHAL)/sestamibi (DMIBI) can predict adverse cardiac events after elective vascular surgery in patients with one or more clinical risk factors. Methods: Consecutive patients with one or more clinical risk factors underwent a preoperative blinded DTHAL/DMIBI. Patients with recent congestive heart failure (CHF) or myocardial infarction (MI) or severe or unstable angina were excluded. Results: Eighty patients (78% men; mean age, 65 years) completed the study. Diabetes mellitus was the most frequent clinical risk factor (73%), followed by age older than 70 years (41%), angina (29%), Q wave on electrocardiogram (26%), history of CHF (7%), and ventricular ectopy (3%). The results of DTHAL/DMIBI were normal in 36 patients (45%); a reversible plus or minus fixed defect was demonstrated in 28 patients (36%), and a fixed defect alone was demonstrated in 15 patients (19%). Nine adverse cardiac events (11%) occurred, including three cases of CHF, and one case each of unstable angina, Q wave MI, non-Q wave MI, and cardiac arrest (successfully resuscitated). Two cardiac deaths occurred (2% overall mortality), one after a Q wave MI and one after CHF and a non-Q wave MI. The cardiac event rate was 14% for reversible defect and 9.8% without reversible defect (P =.71). The cardiac event rate was 12.5% (one of eight cases) for two or more reversible defects, versus 11.1% (eight of 72 cases) for fewer than two reversible defects (P = 1.0). The sensitivity rate of two or more areas of redistribution was 11% (95% CI, 0.3%-48%), the specificity rate was 90%, and the positive and negative predictive values were 12.5% and 89%, respectively. Conclusion: Our study demonstrated no association between reversible defects on DTHAL/DMIBI and adverse cardiac events in moderate-risk patients undergoing elective vascular surgery. (J Vasc Surg 2000;32:77-89.

Improved 3-D correction for partial volume effects

Abstract: An improved method for correction of partial volume effects (PVE) in brain SPECT is proposed. It is fully three-dimensional, does not require particular patient positioning, and works with scans only partially covering the brain. The location of functionally inactive brain regions (primarily cerebrospinal fluid) is extracted from high-resolution MRI. An automatic 3D registration algorithm then determines the geometric transformation between MRI and SPECT. Correction consists of: 1) counting the volumetric active/inactive ratio in each volume element of the functional scan using the measured SPECT point spread function; 2) correcting the functional measures according to these ratios; 3) fusing functional and anatomical information at the resolution of MRI. Quantitative validation was performed using a phantom containing a test region in which multiple parallel acrylic plates thinner than SPECT resolution created high PVE, as well as a large reference region not suffering from PVE. Reference activity was recovered in the test region with an accuracy of 1–3%. The method was applied to clinical images demonstrating a combination of hypoperfusion and cortical atrophy. The composite anatomical-functional corrected images, in which the main sulci are visible, yield better differentiation between decreased function an