Single-photon Emission Computed Tomography Testing Research Articles

Imaging markers of mild cognitive impairment: Multivariate analysis of CBF SPECT

This study aimed to investigate cross-sectional and longitudinal changes of regional cerebral blood flow (rCBF) in preclinical dementia using single photon emission computed tomography (SPECT). SPECT and cognitive function were investigated in 39 mild cognitive impairment (MCI) subjects and 20 age-matched controls. All subjects were followed longitudinally 19 months on average, 16 MCI subjects progressed to Alzheimer's disease (AD), who were retrospectively defined as progressive mild cognitive impairment (PMCI) at baseline and 23 MCI subjects remained stable and were defined as stable mild cognitive impairment (SMCI) at baseline. SPECT was performed both at the initial investigation and at follow-up. Image data were analyzed using multivariate analysis, SPM and volume of interest (VOI)-based analysis. Significant covariate patterns were derived, which differentiate among PMCI, SMCI and controls at baseline as well as describe the longitudinal progression of PMCI. The combined SPECT and neuropsychology increased the diagnostic accuracy of PMCI at baseline. SPECT and neuropsychological testing can be used objectively for both baseline diagnosis and to monitor changes in brain function during very early AD.

Advances in neuroimaging for HIV-1 associated neurological dysfunction: clues to the diagnosis, pathogenesis and therapeutic monitoring.

Persons with advanced human immunodeficiency virus type one (HIV-1) infection seek medical advice for a wide range of neurological disorders including, but not limited to, peripheral neuropathy, toxoplasmosis, cryptococcal meningitis, cytomegalovirus retinitis progressive multifocal leukoencephalopathy, lymphoma and dementia. The diagnosis of HIV-1-associated dementia (HAD) induced as a direct consequence of HIV infection of the brain comes commonly by exclusion. Diagnostic decisions can often be clouded by concomitant depression, motor impairments, and lethargy that follow debilitating immune suppression and weight loss. Indeed, cognitive, motor and behavior abnormalities underlie a variety of neurological dysfunctions associated with advanced HIV-1 infection. Thus, even combinations of clinical, laboratory and neuroimaging tests [for example, magnetic resonance imaging (MRI), computed tomography (CT), single photon emission computed tomography (SPECT) and positron emission tomography (PET)] often fail to provide conclusive diagnostic information. Nonetheless, the recent development of quantitative MR spectroscopic imaging has improved diagnostic possibilities for HAD. We are pleased to discuss these developments as well as taking a forward look into what will soon be made available to improve neuroimaging diagnostic precision. New MR and SPECT testing are being developed in our laboratories and elsewhere both for animal model systems and in humans with HIV-1 disease. Such tests can facilitate dynamic measures of HIV-1 neuropathogenesis providing information for disease events that even 2 years ago were unattainable.

Coronary calcium screening in asymptomatic patients as a guide to risk factor modification and stress myocardial perfusion imaging

Background Previous studies have demonstrated a correlation between the extent of coronary artery calcification (CAC) and atherosclerotic plaque. As a result, CAC screening could be useful in predicting cardiovascular risk in individuals in whom atherosclerosis is developing. One possible method of detecting and quantifying CAC is by x-ray computed tomography, which potentially allows one to stratify patients into groups requiring risk factor modification or follow-up testing such as myocardial perfusion single photon emission computed tomography (SPECT). Methods and results This study was designed to evaluate the clinical utility of multidetector computed tomography (MDCT) in a cardiology practice setting. A retrospective analysis was performed on data from 794 asymptomatic patients who underwent CAC screening over an 8-month period. On the basis of the CAC score and physician consultation, 102 patients underwent subsequent myocardial perfusion SPECT imaging. A substudy was also conducted in 306 patients to measure the interscan variability of MDCT across different CAC score ranges. CAC was detected in 422 of 794 patients. Of these, the CAC was moderate (Agatston score = 101-400) in 14% and severe (>400) in 9%. Patients with 3 or more cardiac risk factors were most likely to exhibit moderate to severe CAC. In myocardial perfusion SPECT testing, no patient with an Agatston score lower than 100 had an abnormal study. In contrast, 41% of patients with severe CAC had an abnormal SPECT study. In the reproducibility substudy the minimal CAC group had the largest variability (86.0%) whereas the severe CAC group had the lowest variability (9.5%). Conclusion CAC screening with MDCT is justified for asymptomatic patients with 3 or more cardiac risk factors. However, risk factor assessment is poor at predicting which individuals will have CAC if fewer risk factors are present. In terms of the interscan variability, MDCT is capable of following changes in CAC for patients with Agatston scores greater than 100. Finally, this study demonstrated that an Agatston score of 400 is a logical threshold to initiate follow-up myocardial perfusion SPECT testing.

Exercise echocardiography or exercise SPECT imaging? A meta-analysis of diagnostic test performance.

Cardiac imaging has advanced rapidly, providing clinicians with several choices for evaluating patients with suspected coronary artery disease, but few studies compare modalities directly. To review the contemporary literature and to compare the diagnostic performance of exercise echocardiography (ECHO) and exercise single-photon emission computed tomography (SPECT) imaging in the diagnosis of coronary artery disease. Studies published between January 1990 and October 1997 identified from MEDLINE search; bibliographies of reviews and original articles; and suggestions from experts in each area. Articles were included if they discussed exercise ECHO and/or exercise SPECT imaging with thallous chloride TI 201 (thallium) or technetium Tc 99m sestamibi for detection and/or evaluation of coronary artery disease, if data on coronary angiography were presented as the reference test, and if the absolute numbers of true-positive, false-negative, true-negative, and false-positive observations were available or derivable from the data presented. Studies performed exclusively in patients after myocardial infarction, after percutaneous transluminal coronary angioplasty, after coronary artery bypass grafting, or with recent unstable coronary syndromes were excluded. Clinical variables, technical factors, and test performance were independently extracted by 2 reviewers on a standardized spreadsheet. Discrepancies were resolved by consensus. Forty-four articles met inclusion criteria. In pooled data weighted by the sample size of each study, exercise ECHO had a sensitivity of 85% (95% confidence interval [CI], 83%-87%) with a specificity of 77% (95% CI, 74%-80%). Exercise SPECT yielded a similar sensitivity of 87% (95% CI, 86%-88%) but a lower specificity of 64% (95% CI, 60%-68%). In a summary receiver operating characteristic model comparing exercise ECHO performance to exercise SPECT, exercise ECHO was associated with significantly better discriminatory power (parameter estimate, 1.18; 95% CI, 0.71-1.65), when adjusted for age, publication year, and a setting including known coronary artery disease for SPECT studies. In models comparing the discriminatory abilities of exercise ECHO and exercise SPECT vs exercise testing without imaging, both ECHO and SPECT performed significantly better than exercise testing. The incremental improvement in performance was greater for ECHO (3.43; 95% CI, 2.74-4.11) than for SPECT (1.49; 95% CI, 0.91-2.08). Exercise ECHO and exercise SPECT have similar sensitivities for the detection of coronary artery disease, but exercise ECHO has better specificity and, therefore, higher overall discriminatory capabilities as used in contemporary practice.

Accuracy and usefulness of atrial pacing in conjunction with transthoracic echocardiography in the detection of cardiac ischemia

Transthoracic echocardiography combined with transesophageal atrial pacing was performed in a community outpatient setting and compared with single-photon emission computed tomography (SPECT) and with coronary arteriography to determine the accuracy and usefulness of the technique. Two groups were defined: group A consisted of 65 of 189 patients who underwent all 3 procedures within a 90-day period; group B consisted of 53 patients who had atrial pacing with transthoracic echocardiography. Seventy-one patients had previously undergone atrial pacing with simultaneous transesophageal echocardiograpny. Atrial pacing to induce abnormal wall morion as an indicator of ischemia was performed by increasing the double product to >20,000. We obtained a sensitivity and specificity of 87% and 88% for group A and 72% and 80% for group B, respectively. We believe that transthoracic echocardiography with atrial pacing is indicated as a means of stress echocardiography in its own right, especially in nonambulatory and chronotropically incompetent patients, as well as in the presence of an ambiguous result on SPECT testing. It is highly accurate compared with our previous study with atrial pacing and simultaneous transesophageal echocardiography, better tolerated, more easily accepted, less invasive, and less costly. Thus, it is a useful stress modality in the detection of myocardial ischemia.