Cine CT for attenuation correction in cardiac PET/CT.

In dual-modality PET/CT systems, the CT scan provides the attenuation map for PET attenuation correction. The current clinical practice of obtaining a single helical CT scan provides only a snapshot of the respiratory cycle, whereas PET occurs over multiple respiratory cycles. Misalignment of the attenuation map and emission image because of respiratory motion causes errors in the attenuation correction factors and artifacts in the attenuation-corrected PET image. To rectify this problem, we evaluated the use of cine CT, which acquires multiple low-dose CT images during a respiratory cycle. We evaluated the average and the intensity-maximum image of cine CT for cardiac PET attenuation correction. METHODS: Cine CT data and cardiac PET data were acquired from a cardiac phantom and from multiple patient studies. The conventional helical CT, cine CT, and PET data of an axially translating phantom were evaluated with and without respiratory motion. For the patient studies, we acquired 2 cine CT studies for each PET acquisition in a rest-stress (13)N-ammonia protocol. Three readers visually evaluated the alignment of 74 attenuation image sets versus the corresponding emission image and determined whether the alignment provided acceptable or unacceptable attenuation-corrected PET images. RESULTS: In the phantom study, the attenuation correction from helical CT caused a major artifactual defect in the lateral wall on the PET image. The attenuation correction from the average and from the intensity-maximum cine CT images reduced the defect by 20% and 60%, respectively. In the patient studies, 77% of the cases using the average of the cine CT images had acceptable alignment and 88% of the cases using the intensity maximum of the cine CT images had acceptable alignment. CONCLUSION: Cine CT offers an alternative to helical CT for compensating for respiratory motion in the attenuation correction of cardiac PET studies. Phantom studies suggest that the average and the intensity maximum of the cine CT images can reduce potential respiration-induced misalignment errors in attenuation correction. Patient studies reveal that cine CT provides acceptable alignment in most cases and suggest that the intensity-maximum cine image offers a more robust alternative to the average cine image.     

Does cardiac SPECT using attenuation and scatter correction accurately predict coronary artery disease in a minority women population?

BACKGROUND: Myocardial perfusion imaging (MPI) is a well-established diagnostic method for evaluation and risk stratification of coronary artery disease (CAD).We undertook this study to validate both the positive predictive value (when compared to cardiac catheterization) and the prognosis afforded by MPI in a group of minority women patients. MATERIAL/METHODS: The database of our Nuclear Imaging and Catheterization Laboratory was retrospectively queried for consecutive minority (African-American, Hispanic and Asian) women patients who underwent MPI and cardiac catheterization within 90 days of each other. Patients with recent revascularization were excluded. Attenuation/scatter correction was utilized in the final interpretation of the study. RESULTS: Of the 54 women patients who underwent MPI, 7 underwent exercise stress testing, 26 had stress testing with adenosine, 18 with dipyridamole and 3 with dobutamine. Eighteen patients (53%) had same number of vessels predicted by MPI and coronary angiography (7 patients with triple vessel disease, 7 with 2-vessel disease and 4 with single vessel disease). Five (3 with intermediate and 2 with high risk scans) out of the 54 patients (9.3%) were dead at 2 years. The sensitivity, specificity and positive predictive value of MPI as compared to angiography were 87.2%, 26.7%, 75.6% and 44.4% respectively. CONCLUSIONS: The sensitivity of MPI in this group of patients is comparable to the general population though the specificity is lower in spite of using attenuation and scatter correction. Low risk perfusion scan signifies favorable prognosis at 2 years with regards to mortality.     

Rural Demographics Racial/Ethnic Diversification in Metropolitan and Nonmetropolitan Population Change in the United States: Implications for Health Care Provision in Rural America

The diversification of the rural population of the United States provides substantial challenges to the current and to future health care systems in rural areas. Because of a variety of historical, discriminatory, and other factors, minority populations have had lower levels of access to health care in rural as well as urban areas and higher rates of both mortality and morbidity than nonminority populations. Although minority health issues have often been seen as primarily urban issues, this article demonstrates that minority population growth has become a major component of total population growth in rural areas in the past several decades (accounting for nearly 62% of the net growth in the nonmetropolitan population of the United States in the 1980s and for nearly 42% in the 1990s), that future US population growth is likely to be largely a product of minority population growth (nearly 89% of US net population growth from 2000 to 2100 is projected to be due to minority population growth), and that the incidence of diseases and disorders in the US population will come to increasingly involve minority populations (by 2050 roughly 43% of all disease/disorder incidences would involve minority population members). The growth of younger minority populations with disproportionately impoverished socioeconomic characteristics will pose challenges for rural areas and health care systems, which also are likely to face health issues created by disproportionately older populations.     

Hyperpolarization moves S4 sensors inward to open MVP,a methanococcal voltage-gated potassium channel

MVP, a Methanococcus jannaschii voltage-gated potassium channel, was cloned and shown to operate in eukaryotic and prokaryotic cells. Like pacemaker channels, MVP opens on hyperpolarization using S4 voltage sensors like those in classical channels activated by depolarization. The MVP S4 span resembles classical sensors in sequence, charge, topology and movement, traveling inward on hyperpolarization and outward on depolarization (via canaliculi in the protein that bring the extracellular and internal solutions into proximity across a short barrier). Thus, MVP opens with sensors inward indicating a reversal of S4 position and pore state compared to classical channels. Homologous channels in mammals and plants are expected to function similarly.