Optimization of Ga-67 imaging for detection and estimation tasks: dependence of imaging performance on spectral acquisition parameters

We have compared the use of two (93 and 185 keV) and three (93, 185, and 300 keV) photopeaks for Ga-67 tumor imaging and optimized the placement of each energy window. METHODS: The bases for optimization and evaluation were ideal and Bayesian signal-to-noise ratios (SNR) for the detection of spheres embedded in a realistic anthropomorphic digital torso phantom and ideal SNR for the estimation of their size and activity concentration. Seven spheres of radii ranging from 1 to 3 cm, located at several sites in the torso, were simulated using a realistic Monte Carlo program. We also calculated the ideal SNR for the detection from simple phantom acquisitions. RESULTS: For detection and estimation tasks, the optimum windows were identical for all sphere sizes and locations. For the 93 keV photopeak, the optimal window was 84-102 keV for the detection and 87-102 keV for estimation; these windows are narrower than the 20% window often used in the clinic (83-101 keV). For the 185 keV photopeak, the optimal window was 170-220 keV for the detection and 170-215 keV for estimation; these are substantially different than the 15% window used in our clinic (171-199 keV). For the 300 keV photopeak, the optimal window for detection was 270-320 keV, and for estimation, 280-320 keV. Using the three optimized, rather than only the two lower-energy, windows yielded a 9% increase in the SNR for the detection of the 3 cm diam sphere (a 12% increase for a 2 cm diam sphere) and a 7% increase in the SNR for estimation of its size. For the acquired phantom data, detection also increased by 9%-12% when using three, rather than two, energy windows.     

Evaluation of three techniques for detection of low-level methicillin-resistant Staphylococcus aureus (MRSA): a disk diffusion method with cefoxitin and moxalactam,the Vitek 2 system,and the MRSA-screen latex agglutination test

Very-low-level methicillin-resistant Staphylococcus aureus (MRSA), or class 1 MRSA, is often misdiagnosed as methicillin-susceptible S. aureus (MSSA). We evaluated the performances of three methods for detection of low-level methicillin resistance: the disk diffusion method using the cephamycin antibiotics cefoxitin and moxalactam, the Vitek 2 system (bioMérieux), and the MRSA-screen test (Denka). Detection of the mecA gene by PCR was considered to be the "gold standard." We also determined the sensitivity of the oxacillin disk diffusion method with 5- and 1-microg disks and that of the Oxascreen agar assay with 6 mg of oxacillin liter(-1) for detection of MRSA. We compared the distributions of MICs of oxacillin and cefoxitin by the E-test (AB Biodisk), and those of moxalactam by dilutions in agar, for MRSA and MSSA isolates. The 152 clinical isolates of S. aureus studied were divided into 69 MSSA (mecA-negative) and 83 MRSA (mecA-positive) isolates, including 63 heterogeneous isolates and 26 class 1 isolates (low-level resistance). The cefoxitin and moxalactam disk diffusion tests detected 100% of all the MRSA classes: cefoxitin inhibition zone diameters were <27 mm, and moxalactam inhibition zone diameters were <24 mm. The Vitek 2 system and the MRSA-screen test detected 94 and 97.6% of all MRSA isolates, respectively. The sensitivities of the 5- and 1-microg oxacillin disks were 95.2 and 96.4%, respectively, whereas that of the Oxascreen agar screen assay was 94%. All of the tests except the 1-microg oxacillin disk test were 100% specific. For the class 1 MRSA isolates, the sensitivity of the Vitek 2 test was 92.3%, whereas those of the MRSA-screen test and the disk diffusion method with cefoxitin and moxalactam were 100%. Therefore, the cefoxitin and moxalactam disk diffusion methods were the best-performing tests for routine detection of all classes of MRSA.     

Effect of zidovudine resistance mutations on virologic response to treatment with zidovudine or stavudine,each in combination with lamivudine and indinavir

The authors studied the effect of zidovudine (ZDV) resistance mutation on virologic response to treatment with ZDV or stavudine (d4T) each in combination with lamivudine and indinavir. Viral genotyping was performed on plasma HIV-1 RNA at study entry and concerned 155 patients previously treated with ZDV, didanosine, or zalcitabine and enrolled in the NOVAVIR (Agence National de Recherche sur le SIDA [ANRS] 073) trial. Three virologic responses were investigated: early response (<50 copies/mL at week 24), late response (<500 copies/mL at week 80), and virologic failure (two HIV-1 RNA >5000 copies/mL). Patients were classified as resistant or susceptible to ZDV according to the ANRS algorithm. Plasma viral RNA from 123 of 155 patients had two or more ZDV resistance mutations. The number of ZDV resistance mutations was positively correlated with the duration of prior antiviral therapy (p <.001). At week 24, 74% and 77% of patients with virus classified as resistant were responders in the d4T and ZDV arm, respectively. Similar results were found at week 80. Virologic failure was reached in 7 of 24 patients with virus classified as susceptible and in 26 of 131 patients with resistant virus (p =.29). In the ZDV arm, patients classified as resistant had longer times to virologic failure than those classified as susceptible (p =.003). In conclusion, sustained virologic response despite presence of ZDV resistance mutations implies that these mutations do not preclude an early and durable response to treatment with a potent three-drug regimen in these patients. Patients susceptible to ZDV had lower median mean corpuscular volumes and lower random indinavir levels, suggesting that adherence was the main reason for failure.     

In-vitro adhesion of endometrium to autologous peritoneal membranes: effect of the cycle phase and the stage of endometriosis

BACKGROUND: Endometrium can adhere to autologous peritoneum. This study was undertaken to determine the effect of the menstrual cycle phase and the presence and stage of endometriosis on in-vitro adhesion of endometrium onto autologous peritoneum. METHODS: This was performed in an academic medical research centre. Sixty-seven subfertile women with a visually normal pelvis (n = 18) and with biopsy-proven endometriosis (n = 49) were included. Endometrial and peritoneal biopsies were obtained at laparoscopy during menstrual, follicular and luteal phase. Endometrium was cultured in vitro with autologous peritoneum, followed by fixation, paraffin embedding, serial sectioning, hematoxylin-eosin and immunohistochemical staining. Endometrial-peritoneal adhesion was evaluated using light microscopy. RESULTS: Endometrial-peritoneal adhesion was observed in approximately 80% of the adhesion assays and was not affected by the phase of the cycle, or by the presence and stage of endometriosis. The continuity of the mesothelial layer was disrupted at the attachment sites. Epithelialization was observed along the edges to integrate the endometrial implant. After adhesion, histological changes were observed within and below the implant. CONCLUSIONS: Endometrium obtained during menstrual, follicular or luteal phase appears to have a similar potential to implant in vitro on autologous peritoneum, and this adhesion process is not affected by the stage of endometriosis.     

A solitary minute thyroid lymphoma of MALT-type without lymphoid thyroiditis

Most of the primary thyroid malignant lymphomas have been considered of mucosa-associated lymphoid tissue (MALT) type and arise from lymphocytic thyroiditis. We report an uncommon case of a 67-yr-old man who underwent total thyroidectomy for multinodular goiter with tracheal compression. At histopathologic examination, we discovered a minute (3-mm diameter) lesion of low-grade thyroid lymphoma of MALT type without any lymphocytic thyroiditis lesion on 33 section levels of the entire thyroid gland. No general inflammatory, autoimmune, or lymphomatous disorder has been evidenced both at staging and after 30 mo of follow-up. MALT-type low-grade lymphoma may, in some instances, develop de novo within the thyroid without an antecedent MALT-type lymphoma.     

NK cells developing in vitro from fetal mouse progenitors express at least one member of the Ly49 family that is acquired in a time-dependent and stochastic manner independently of CD94 and NKG2

NK cells developing in vitro from fetal progenitors in the presence of IL-2 are phenotypically and functionally indistinguishable from mature adult NK cells, with the exception that they generally lack surface expression of any of the Ly49 molecules that have previously been examined. Using two recently developed anti-Ly49 mAb, we show here that most of these NK cells in fact express high levels of at least one previously uncharacterized member of the Ly49 family, most likely Ly49E. Detailed kinetic and clonal analysis revealed that these Ly49 molecules were acquired in a progressive and stochastic manner independently of CD94 and NKG2. CD94 and NKG2 were both expressed early in NK cell development, sometimes in the absence of NK1.1, with CD94 invariably being expressed at two different levels. IL-4 differentially inhibited the expression of CD94 and Ly49 receptors, but had little or no effect on the expression of NKRP1 molecules.     

Placental inflammation and perinatal transmission of HIV-1

The effect of placental membrane inflammation on mother-to-child transmission (MTCT) of HIV-1 is reported. Placentas from HIV-1-infected women were examined as part of a perinatal HIV-1 project in Mombasa, Kenya. Polymerase chain reaction analysis was used to test for HIV-1 in the infants at birth and at 6 weeks. The maternal HIV-1 seroprevalence was 13.3% (298 of 2,235). The overall rate of MTCT of HIV-1 was 25.4%; polymerase chain reaction analysis revealed that of the 201 infants 6.0% (12) were already HIV-1-positive at birth (intrauterine transmission) and 19.4% (39) were infected during the peripartum period or in early neonatal life (perinatal transmission). The prevalence of acute chorioamnionitis was 8.8%, that of deciduitis was 10.8%, and that of villitis was 1.6%. Acute chorioamnionitis was independently associated with peripartum HIV-1 transmission but not with in utero MTCT (17.9% vs. 6.7%, respectively; adjusted odds ratio, 3.9; 95% confidence interval, 1.2-12.5; p =.025). Other correlates of perinatal MTCT were presence of HIV in the genital tract and in the baby's oral cavity and a high maternal viral load in peripheral blood. The adjusted population attributable fraction of 12.8% (95% confidence interval, 1.5%-22.8%) indicated that approximately 3% of MTCT could be prevented if acute chorioamnionitis was eliminated. We suggest that further research on the role of antimicrobial treatment in the prevention of chorioamnionitis and the reduction of peripartum MTCT needs to be performed.     

What triggers catch-up saccades during visual tracking?

When tracking moving visual stimuli, primates orient their visual axis by combining two kinds of eye movements, smooth pursuit and saccades, that have very different dynamics. Yet, the mechanisms that govern the decision to switch from one type of eye movement to the other are still poorly understood, even though they could bring a significant contribution to the understanding of how the CNS combines different kinds of control strategies to achieve a common motor and sensory goal. In this study, we investigated the oculomotor responses to a large range of different combinations of position error and velocity error during visual tracking of moving stimuli in humans. We found that the oculomotor system uses a prediction of the time at which the eye trajectory will cross the target, defined as the "eye crossing time" (T(XE)). The eye crossing time, which depends on both position error and velocity error, is the criterion used to switch between smooth and saccadic pursuit, i.e., to trigger catch-up saccades. On average, for T(XE) between 40 and 180 ms, no saccade is triggered and target tracking remains purely smooth. Conversely, when T(XE) becomes smaller than 40 ms or larger than 180 ms, a saccade is triggered after a short latency (around 125 ms).     

Detection of apple chlorotic leaf spot virus using a 5' nuclease assay with a fluorescent 3' minor groove binder-DNA probe

The development of a real-time 5' nuclease RT-PCR assay for the detection of apple chlorotic leaf spot virus (ACLSV) from infected plant material is described. A short fluorogenic 3' minor groove binder-DNA hydrolysis probe was used to circumvent genome variability between isolates and target a short conserved sequence. The covalent attachment of the minor groove binder moiety at the 3' end of the probe increased the probe/target duplex stability and raised the melting temperature to a range suitable for real-time analysis. The method is rapid, sensitive and takes place within a single tube without post-PCR handling of the amplification products.     

Reduction of CO(2)-pneumoperitoneum-induced metabolic hypoxaemia by the addition of small amounts of O(2) to the CO(2) in a rabbit ventilated model. A preliminary study

BACKGROUND: CO(2)-pneumoperitoneum used in endoscopic surgery induces system effects by CO(2) absorption. This study investigated the effect of the addition of O(2) to CO(2)-pneumoperitoneum, upon CO(2) absorption. METHODS: The effect of a pneumoperitoneum using 100% CO(2) or 94% CO(2) + 6% O(2) upon arterial blood gases, acid base and O(2) homeostasis was evaluated. In series A suboptimal ventilation and a pneumoperitoneum pressure (PP) of 10 mmHg was used. In series B adequate ventilation and PP of 6 mmHg was used. RESULTS: CO(2)-pneumoperitoneum profoundly affected blood gases and acid base homeostasis i.e. increasing pCO(2), HCO(3)(P < 0.001) and lactate concentrations (P < 0.05) and decreasing pH, actual base excess and standard bicarbonate (P < 0.001), resulting in metabolic hypoxaemia with desaturation, lower pO(2) (P < 0.001) and O(2)Hb (P < 0.05). These effects were more pronounced with higher PP and suboptimal ventilation. CONCLUSION: CO(2)-pneumoperitoneum profoundly affected blood gases and acid base homeostasis resulting in metabolic hypoxaemia. The addition of 6% of O(2) to the CO(2)-pneumoperitoneum prevented these effects to a large extent. If these preliminary data are confirmed in the human, the addition of a few percent of O(2) to CO(2) could become important for endoscopic surgery of long duration, especially in obese patients with limited cardiorespiratory adaptation and steep Trendelenburg.