Fast transmission CT for determining attenuation maps using a collimated line source, rotatable air-copper-lead attenuators and fan-beam collimation

We describe a technique using a line source and a rotatable air-copper-lead assembly to acquire gamma transmission computed tomographic (TCT) data for determining attenuation maps to compensate SPECT emission scans. The technique minimizes problems associated with discriminating 99mTc transmission and 201Tl emission photons and requires only a modest increase in total study time. A 99mTc line source and a stacked foil ("multislat") collimator are placed near the focal line of a fan-beam collimator (114 cm focal length) mounted on one detector of a triple-camera SPECT system. We acquired TCT data of plastic rod and anthropomorphic thorax phantoms to investigate the capability of the line source and rotatable air-copper-lead attenuators to determine attenuation maps. The data were acquired with and without 5.4 MBq (145 microCi) of 201Tl placed in the myocardial chamber of the thorax phantom. Phantoms also were scanned using a curved transmission slab source mounted to a parallel-hole collimator. Fan-beam TCT images have improved resolution compared with parallel-beam TCT images. Two patient scans also were performed to evaluate the clinical usefulness of fan-beam TCT. The rotatable air-copper-lead attenuator method eliminates contamination of emission data by transmission photons and reduces spill-over of emission data into the transmission energy window for some cases. Results show the feasibility of using fast, sequential or interlaced transmission scans of a line source within a rotatable air-copper-lead attenuator assembly to obtain accurate attenuation maps for SPECT attenuation compensation.     

Thermodynamic driving forces for PAH isomerization and growth during thermal treatment of polluted soils

For a limiting case of thermodynamic equilibrium, the importance of two classes of thermal chemical reactions that modify the structure and bioactivity of polycyclic aromatic hydrocarbons (PAH) was assessed computationally. These reactions are molecular weight (MW) growth by acetylene addition, and intramolecular rearrangement (isomerization). Temperatures (300-1100 degrees C), and the chemical environment (C(2)H(2)/H(2) molar ratios) were selected for relevancy to thermal treatment of PAH-contaminated soils under oxygen-free conditions. Molecular mechanics methods [MM3(92)] were used to compute thermochemical properties for calculation of equilibrium constants, i.e., heats of formation, standard entropies, and heat capacities for 30 PAH with empirical formulae C(14)H(10), C(16)H(10), C(18)H(10), C(18)H(12), C(20)H(10), and C(20)H(12). Included were 11 PAH containing only six-membered rings and 19 PAH containing both five- and six-membered rings. For each of these PAH the calculations predict that with increasing temperature, isomerization increases the "complexity" of the PAH mixture, i.e., the relative abundance of each PAH isomer in the mixture other than the most stable isomer, increases. Isomerization also partially transforms non-mutagens to mutagens, e.g., pyrene and benzo[e]pyrene to fluoranthene and benzo[a]pyrene, respectively, and partially converts cyclopenta[c, d]pyrene (CPEP) and chrysene, both human cell mutagens, to one and three additional human cell mutagens, respectively. Acetylene addition transforms the non-mutagens phenanthrene and pyrene to the mutagens triphenylene and CPEP, respectively. Some of the predicted PAH have been observed elsewhere among the products of aromatics pyrolysis. This study elucidates PAH reactivity for comparison with measurements, and identifies PAH reactions to be monitored and avoided in soil thermal decontamination and other waste remediation processes.     

Molecular regulation of UVB-induced cutaneous angiogenesis

We determined whether cutaneous angiogenesis induced by exposure of mice to ultraviolet-B (UVB) radiation is associated with an imbalance between positive and negative angiogenesis-regulating molecules. Unshaved C3H/HeN mice were exposed to a single dose (15 kJ per m2) of UVB. At various times, the mice were killed, and their external ears were processed for routine histology and immunohistochemistry. Antibodies against proliferating cell nuclear antigen and bromodeoxyuridine identified dividing cells. Antibodies against CD31/ PECAM-1 identified endothelial cells, and antibodies against basic fibroblast growth factor (bFGF), vascular endothelial growth factor/vascular permeability factor, and interferon-beta (IFN-beta) identified angiogenesis-regulating molecules. Epidermal hyperplasia was documented by 48 h and reached a maximum on day 7 after exposure to UVB. The expression of bFGF increased by 24 h, whereas the expression of IFN-beta decreased by 72 h after exposure to UVB. The expression of vascular endothelial growth factor/vascular permeability factor increased slightly after irradiation. The altered balance between bFGF and IFN-beta was associated with increased endothelial cell proliferation (bromodeoxyuridine + CD31 + cells) within existing blood vessels, leading to telangiectasia and new blood vessels. UV-induced epidermal hyperplasia and cutaneous angiogenesis were highest in IFN-alpha/beta receptor knockout mice. These results demonstrate that in response to UVB radiation, dividing keratinocytes produce a positive angiogenic molecule (bFGF) but not a negative angiogenic molecule (IFN-beta), and that this altered balance is associated with enhanced cutaneous angiogenesis.     

Mental health supplement to the Ontario Health Survey: methodology

OBJECTIVE: To describe the methodology of a province-wide, cross-sectional, epidemiologic study of psychiatric disorder among those aged 15 years and over living in household dwellings in Ontario. METHOD: Respondents for the survey were drawn from households (N = 13002) participating in a province-wide health survey. One person per household was selected, and 9953 (76.5%) participated. RESULTS: Participants and nonparticipants were similar to each other. An extensive array of data, including measures of psychiatric disorder classified using a revised version of the Composite International Diagnostic Interview (CIDI), are available for all respondents. CONCLUSIONS: The Ontario Health Supplement is contained in a public-use data file at the Ontario Ministry of Health and is available to investigators for study. A strong survey design, careful measurement, and acceptable levels of response provide the rationale for our inviting researchers to access and use the Ontario Health Supplement data base.     

Continuous non-invasive blood pressure monitoring by brachial artery displacement method in high-risk surgical patients

Continuous non-invasive blood pressure (CNBP) measurements were compared to invasive radial artery pressure recordings in 26 patients with cardiac, vascular and/or pulmonary disease. Patients were studied during general anaesthesia (n = 6), regional anaesthesia (n = 10), or combined technique (n = 10) for abdominal or transurethral surgery. CNBP was obtained from a cuff placed around the upper arm and simultaneously compared to invasive pressure from the ipsilateral radial artery. A CNBP device (7001 Cortronic) used intermittent oscillometric measurement for calibration. Through a cuff continuously inflated to a pressure of 20 mmHg, a microprocessor-controlled electro-pneumatic acquisition system sensed displacements of the brachial artery wall. Amplified, digitally converted, filtered and transformed data were displayed as a continuous pulse pressure waveform and digital pressure values on the screen. The CNBP method functioned without disturbances before surgery in all patients. Intra-operative use of electrocautery or a spontaneous occurrence of warning on the screen repeatedly triggered oscillometric recalibration, hence CNBP measurements were discontinued in nine patients. Coefficients of correlation (r) of all invasive and CNBP pairs (n = 1111) were 0.68, 0.58 and 0.70 for systolic, diastolic, and mean blood pressures, respectively. Prediction errors (bias, mean +/- SD) were -13.6 +/- 22.5 mmHg (on average CNBP < invasive pressure) for systolic, +13.0 +/- 12.4 mmHg (CNBP > invasive pressure) for diastolic and +5.0 +/- 13.9 mmHg (CNBP > invasive pressure) for mean CNBP, as compared to radial artery pressure values. Absolute errors (precision) were 25.3 +/- 9.4 mmHg for systolic, 17.4 +/- 4.5 mmHg for diastolic, and 13.9 +/- 4.6 mmHg for mean CNBP. During anaesthesia induction (n = 672) the difference between consecutive measurements (trend of pressure changes) with invasive and CNBP method exceeded 20 mmHg in 90 (13.3%) instances for systolic, in 33 (4.9%) instances for diastolic, and in 45 (6.6%) instances for mean blood pressure. In conclusion, the CNBP method by brachial artery wall displacement failed to measure the blood pressure reliably and to display the trend of pressure changes correctly during anaesthesia induction. In its present form this CNBP method should not replace invasive blood pressure monitoring in high-risk patients neither for anaesthesia induction nor during non-thoracic surgical procedures.     

Lymphocyte response to silica among offspring of silicone breast implant recipients

The current study evaluated immune response to silicon dioxide in children born to women with silicone breast implants. In part one of the study, the T lymphocytes of 21 of 24 such children were significantly stimulated by silicon dioxide (silica). Part two consisted of eleven children, four born preimplantation and seven born postimplantation. None of the preimplant offspring showed T cell responses to silica; five of the seven postimplant children were positive for T cell memory for silica. Part three was a blinded study based on statistically significant differences in T cell stimulation with silicon dioxide between postimplant children and controls. These findings indicate a common immune reaction, that of T cell memory, occurs in mothers and their children born after exposure to silicone mammary implants placed prior to pregnancy. Since not all such children were breast fed the result favors transplacental passage of immunogens such as silicone oligomers or through maternofetal cellular traffic.     

Early office-based vs late hospital-based nasolacrimal duct probing. A clinical decision analysis

BACKGROUND: Controversy exists regarding the treatment of infants with symptomatic nasolacrimal duct obstruction. One philosophy advocates "early" nasolacrimal duct probing, generally in the office. An alternate strategy advocates medical management until the infant is approximately 12 months old to allow for spontaneous resolution, with those with persistent nasolacrimal duct obstruction usually treated by "late" probing in the hospital with the use of general anesthesia. METHODS: We used clinical decision analysis to compare these two opposing treatment strategies. A decision tree was constructed with the usual designations for probability nodes and decision points, comparing early probing at 6 months of age in the office and late probing at 12 months of age in the hospital. The initial decision point thus addressed treatment of children who still had symptomatic nasolacrimal duct obstruction at 6 months of age. One repeated probing under same-strategy conditions was performed for patients in whom initial office probing failed. Values for probability nodes were derived from the ophthalmic literature, including a 70% rate of spontaneous resolution of nasolacrimal duct obstruction between the ages of 6 and 12 months. RESULTS: Both the early office probing strategy and the late hospital probing strategy yielded success rates greater than 99%. Based on prevailing fees, the late hospital strategy cost $2,310,000 more than the early office strategy per 10,000 patients, even though fewer procedures were performed. CONCLUSION: Early office probing and late hospital probing have similar high success rates, albeit at a higher cost for the late hospital probing strategy.