Digital imaging of the chest

During the past several years, image acquisition in nuclear medicine, computed tomography, ultrasonography, subtraction angiography, and magnetic resonance has been by digitization. Despite these advances, research in the development of digital imaging in conventional radiography has lagged behind. Although studies with a variety of digital techniques have been carried out on several fronts, we still do not possess a method that has captured the imagination of the majority of radiologists and other physicians to a point where it could replace conventional screen-film imaging. This article reviews the current status and general principles of the technology, focusing on the four digital radiographic techniques that have shown the greatest promise - film digitization, an image intensifier - based system, photostimulable phosphor plates, and a scanned projection system. The physical aspects of each of the four systems and the clinical results that have been reported to date, as well as the advantages and disadvantages of each system, are presented.     

High insulin and low IGF-I plasma levels following pancreas transplantation in rats. Implications for bone and mineral metabolism

Primary disturbances in mineral metabolism and deficiencies in insulin and insulin-like growth factor-I (IGF-I) have been implicated in the pathogenesis of diabetic osteopenia. This prompted us to investigate whether normal bone minerals and bone morphology are preserved after pancreas transplantation. To this end, 8 inbred rats (transplants) were compared with 9 sham-operated rats (controls) 20 months after orthotopic pancreas transplantation. While basal levels of insulin remained unaffected by transplantation, an oral glucose load elicited hyperinsulinemia (integrated incremental response: mean +/- SEM, 62+/-8 nmol l(-1) 60 min in transplants vs. 32+/-6 nmol l(-1) 60 min in controls; p<0.01) in the presence of normal glucose levels. Fecal and urinary excretion and fractional intestinal absorption of calcium, magnesium and phosphorus, net calcium absorption and the respective serum mineral levels were unchanged after transplantation, as were those of the calciotropic hormones. Serum osteocalcin and bone alkaline phosphatase remained unaffected, and urinary excretion of pyridinium and deoxypyridinium were unchanged. Fasting plasma IGF-I concentration was significantly decreased in transplants (930+/-42 ng ml(-1)) vs. control rats (1074+/-49 ng ml(-1); p < 0.05). Despite similar physical and chemical properties of bone in both groups, histomorphometry revealed slight osteopenia in transplant rats, as reflected by a 38% reduction in the cancellous bone area of the proximal tibial metaphysis. Plasma IGF-I levels were significantly correlated with bone mineral apposition rate (r=0.70, p<0.02), osteoblast perimeter (r=0.60, p<0.05) and osteoid perimeter (r=0.60, p<0.05). In conclusion, pancreas transplantation preserves physical and chemical properties of bone, but bone metabolism is not completely normal after transplantation, as evidenced by decreased cancellous bone. This might have resulted from the insulin resistance associated with the lowering of the plasma IGF-I level, which was correlated with the mineral apposition rate.     

The distribution of infectivity in blood components and plasma derivatives in experimental models of transmissible spongiform encephalopathy

BACKGROUND: The administration of blood components from donors who subsequently develop Creutzfeldt-Jakob disease has raised the issue of blood as a possible vehicle for iatrogenic disease. STUDY DESIGN AND METHODS: We examined infectivity in blood components and Cohn plasma fractions in normal human blood that had been "spiked" with trypsinized cells from a scrapie-infected hamster brain, and in blood of clinically ill mice that had been inoculated with a mouse-adapted strain of human transmissible spongiform encephalopathy. Infectivity was assayed by intracerebral inoculation of the blood specimens into healthy animals. RESULTS: Most of the infectivity in spiked human blood was associated with cellular blood components; the smaller amount present in plasma, when fractionated, was found mainly in cryoprecipitate (the source of factor VIII) and fraction I+II+III (the source of fibrinogen and immunoglobulin); almost none was recovered in fraction IV (the source of vitamin-K-dependent proteins) and fraction V (the source of albumin). Mice infected with the human strain of spongiform encephalopathy had very low levels of endogenous infectivity in buffy coat, plasma, cryoprecipitate, and fraction I+II+III, and no detectable infectivity in fractions IV or V. CONCLUSION: Convergent results from exogenous spiking and endogenous infectivity experiments, in which decreasing levels of infectivity occurred in cellular blood components, plasma, and plasma fractions, suggest a potential but minimal risk of acquiring Creutzfeldt-Jakob disease from the administration of human plasma protein concentrates.     

Iron supplementation in female blood donors deferred by copper sulfate screening

Female blood donors with low hematocrit levels detected by copper sulfate screening were selected randomly to receive either 75 mg of iron per day, as ferrous gluconate, or a calcium phosphate placebo. Their ferritin, serum iron, total iron-binding capacity, zinc protoporphyrin, and hemoglobin values, as well as their suitability to donate blood, were determined initially (Visit 1) and at four follow-up visits (Visits 2-5). By the second visit, the serum ferritin and iron values of donors receiving iron supplementation differed significantly from those of donors receiving placebo. By the fifth visit, a less marked but significant increase in hemoglobin had occurred in the iron group, but not in the placebo group. At no time was there a significant difference between the groups' suitability to donate blood, with each group donating at almost half of their visits. The authors conclude that iron supplementation at this dose level in deferred female blood donors improves their iron status and hemoglobin levels, but does not significantly increase their suitability to donate blood as compared with the suitability of placebo-treated donors.     

N-甲基-D-天冬氨酸受体在缺氧缺血性脑损伤新生大鼠脑海马中的远期表达

目的:观察新生大鼠缺氧缺血性脑损伤后,海马发育过程中N-甲基-D-天冬氨酸受体的远期表达变化。方法:实验于2006-03/06在解放军第三军医大学新桥医院中心实验室完成。选用新生7日龄SD大鼠72只,按随机数字表法分为缺氧缺血性脑损伤组和假手术组,每组36只。各组又分为生后15d(n=6)、22d(n=6)、29d(n=6)、36d(n=12)及43d(n=6)5个时相点。①参照Rice法通过结扎7日龄大鼠左侧颈总动脉,吸入氧气体积分数为0.08的氮氧混合气,制成缺氧缺血性脑损伤模型,出现自发或夹尾左旋则证明模型制作成功。假手术组仅切开颈部皮肤,暴露左侧颈总动脉。②应用免疫组织化学法检测缺氧缺血后不同时点两组大鼠脑海马CA1区N-甲基-D-天冬氨酸受体NR1亚单位的表达(n=6),测量平均灰度值,灰度值越低,蛋白表达越强;生后36d时相点大鼠(n=6)利用Morris水迷宫测定学习记忆能力;最后应用电镜观察生后36d大鼠海马突触结构。结果:72只大鼠,全部进入结果分析,无脱失。①生后22-43d缺氧缺血性脑损伤组大鼠(缺氧缺血后15-36d)脑海马CA1区NR1平均灰度值分别为167.69±6.48,174.57±4.81,179.30±5.92,176.50±5.93,均显著高于同日龄假手术组148.96±4.91,151.17±6.37,152.06±9.86,156.32±6.86(P均<0.01)。②Morris水迷宫实验中,缺氧缺血性脑损伤组大鼠逃避潜伏期显著长于假手术组(48.87±9.47)s,(11.97±2.20)s,(P<0.01);原平台象限游泳距离/总游泳距离的百分比显著低于假手术组(14.45±3.85)%,(62.20±8.74)%(P<0.01)。③生后36d(缺氧缺血后29d),透射电镜下缺氧缺血性脑损伤组大鼠患侧海马突触后膜致密物较假手术组明显减少。结论:新生大鼠缺氧缺血性脑损伤后期存在海马N-甲基-D-天冬氨酸受体的表达下调,可能对大鼠远期空间学习记忆产生一定影响。     

Evaluation of the Atrial Evoked Response for Capture Detection with High-Polarization Leads

AutoCapture™ based on the evoked response can be confounded by electrode polarization. In this study, polarization was measured in human subjects who had chronic atrial leads. The aim of the study was to determine whether electrode polarization can be measured using a time integral atrial evoked-response integral (AERI) of the negative portion of the atrial paced ER evoked-response signal and to determine whether high-polarization atrial leads unsuitable for AutoCapture™ can be identified a priori. Atrial intracardiac-electrogram (IEGM) signals from 39 patients with implanted pacemakers were recorded and analyzed. The signals were recorded during conventional atrial-threshold searches. A total of 221 atrial-capture thresholds were recorded, ranging from 0.25 to 2.75 V with a mean of 0.79 V. Each evoked response was evaluated using the AERI in a 36 ms window following the 0.4 ms atrial stimulus. The polarization was estimated as a linear function of stimulus voltage using the evoked-response signal integral of captured beats identified on the IEGM. The 221 threshold-search datasets were obtained using leads with eight different electrode materials. Polarization could be measured using AERI as a function of stimulus voltage. Furthermore, this polarization measure can be used to identify high-polarization leads, which are ill suited for the atrial AutoCapture™ algorithm.     

Optimizing the Geometry of Implantable Leads for Recording the Monophasic Action Potential with Fractally Coated Electrodes

This study investigates the influence of various lead geometry on intracardial signals like the monophasic action potential (MAP) to optimize the geometry of implantable MAP leads. The experimental results were compared with a field theoretical approach to the origin of MAP from the transmembrane potential (TAP). During the experiments several lead geometries (tip surface: 1.3 to 12 mm²; tip-ring distance: 0.8 mm to 25 cm; ring surface: 1.8mm² to 40 mm²) were investigated in endo- and epicardial positions in 12 dogs (17±9 kg). The electrodes were fixed passively (tines) or actively (screws). MAP was recorded during several interventions and correlated with MAP measured using an Ag-AgCl MAP catheter. The experimental results showed that small tips provided high MAP amplitudes with less pressure. No difference was observed using active and passive fixations. A tip-ring distance smaller than 5 mm with a ring surface smaller than the tip (<5 mm²) avoided artifacts in the repolarization course. For the theoretical approach the quasistatic, anisotropic bidomain model was calculated in smalt unity volumes V_i where the TAP φ_m was constant and represented by the current density J. Two solutions for electrode positions at and outside the heart were achieved. By superposition of each solution φ_ei the summed potential at the electrode position was calculated. The theoretical findings show in good correlation with the experimental results that a larger distance than 10 mm leads to distortions in repolarization course by signals proportional to φ_out.     

Blood loss and replacement in total hip arthroplasty: a multicenter study. The Preoperative Autologous Blood Donation Study Group

To determine blood loss, the number of transfusions, and the hemoglobin levels achieved in patients via transfusion in the course of total hip arthroplasty, 324 patient records from 1987 through 1989 were reviewed at three university and three community hospitals. Calculated blood loss was 3.2 +/- 1.3 units in primary procedures and 4.0 +/- 2.1 units in revision procedures (mean +/- SD). Of 777 red cell units transfused, 455 (59%) were autologous units. Transfused patients received 2.0 +/- 1.8 units for primary procedures and 2.9 +/- 2.3 units for revision procedures (mean +/- SD). The maximum number of units given to 95 percent of the transfused patients was 4 for primary procedures and 6 for revision procedures. The mean postoperative hemoglobin level after all transfusions was 103 to 110 g per L, regardless of patient age group of physical status, autologous donor status, or hospital. No difference in length of hospital stay was observed for patients less than 65 years old with hemoglobin concentrations of 80 to 139 g per L at discharge.