Measured attenuation correction methods

Accurate attenuation correction is a prerequisite for the determination of exact local radioactivity concentrations in positron emission tomography. Attenuation correction factors range from 4–5 in brain studies to 50–100 in whole body measurements. This report gives an overview of the different methods of determining the attenuation correction factors by transmission measurements using an external positron emitting source. The long-lived generator nuclide⁶⁸Ge/⁶⁸Ga is commonly used for this purpose. The additional patient dose from the transmission source is usually a small fraction of the dose due to the subsequent emission measurement. Ring-shaped transmission sources as well as rotating point or line sources are employed in modern positron tomographs. By masking a rotating line or point source, random and scattered events in the transmission scans can be effectively suppressed. The problems of measured attenuation correction are discussed: transmission/emission mismatch, random and scattered event contamination, counting statistics, transmission/emission scatter compensation, transmission scan after administration of activity to the patient. By using a double masking technique simultaneous emission and transmission scans become feasible.This article was presented at the 1st EEC workshop on accuracy determination in PET, January 19–20th. 1989 Pisa, Italy (COMAC-BME Concerted Project Characterization and Standardization of PET Instrumentation)     

The immunofluorescence-microscopical evidence of insulin and glucagon in transplantated isolated Langerhans' islets in diabetic rats and dogs (author's transl)]

With the histochemical immunofluorescence technique were demonstrated the insulin and glucagon in the transplantated isolated Langerhans' islets in the liver at diabetic rats and dogs. Further on were tested the diabetic metabolic level with aid of clinico-chemical methods during the period of investigation (blood glucose, serum insulin, glucose tolerance test). It was found that after transplantation, 1 year by the rats and more than 8 weeks by the dogs, is existing a normoglycemic level. In the transplanted islets were seen a good immunofluorescence of insulin in the B cells and the glucagon in the A cells in all investigated stages.     

Changed visuomotor transformations during and after prolonged microgravity

A series of step-tracking experiments was conducted before, during, and after a 3-week space mission to assess the effects of prolonged microgravity on a non-postural motor-control task. In- and post-flight accuracy was affected only marginally. However, kinematic analyses revealed a considerable change in the underlying movement dynamics: too-small force and, thus, too-low velocity in the first part of the movements was mainly compensated by lengthening the deceleration phase of the primary movement, so that accuracy was regained at its end. The observed in-flight decrements in peak velocity and peak acceleration point to an underestimation of mass, in agreement with the re-interpretation hypothesis of Bock et. al. Post-flight no reversals of the in-flight changes (negative aftereffects) were found. Instead, there was a general slowing down, which could be due to post-flight physical exhaustion.     

Evidence for reduced traumatization during laparoscopic versus conventional cholecystectomy: Different changes in histamine levels related to special phases of operation

The role of histamine in injury due to trauma or surgical treatment is more than doubtful after more than 70 years of investigation. A comparison of histamine released during conventional versus minimal invasive surgery seems especially useful to elucidate the role of histamine in such important events of the daily clinical life.Histamine is released during conventional cholecystectomy in patients of high age, a special group of risk for perioperative morbidity and mortality. In animal experiments, it was shown that this histamine release is due to technical differences between the two types of operation. Hence histamine release seems to be a suitable parameter for the stimulus-induced approach to stress and trauma. Histamine is localized in high concentrations especially in abdominal tissues. After its release it may cause direct actions at a susceptible myocardium, pulmonary parenchyma or gastrointestinal mucosa. However, histamine release is also a proxy variable for mast cell irritation, stimulation and mediator release. This should not be forgotten when the role of histamine is discussed in shock, ARDS, DIC and other clinically relevant or even life-threatening events in routine surgical care.     

Localization of corticotropin-releasing activity in the rat hypothalamus

Hypothalamic nuclei were removed from frozen sections of rat brain and examined for their corticotropin-releasing activity. The highest concentration was measured in the median eminence. In addition there was significantly more activity detected in the nuclei paraventricularis, supraopticus, suprachiasmaticus and arcuatus than in the other nuclei.     

Infection of marmosets with parainfluenza virus types 1 and 3.

Infection of wild marmosets (Saguinus mystax) with strains of parainfluenza virus types 1 and 3 resulted in acute respiratory infection. Virus replication in the upper respiratory tract was of a degree similar to that seen in children acutely infected with parainfluenza viruses. Serum antibody developed with both virus types; however, local secretory antibody was not detectable. The infection was transmissible to susceptible animals up to 3 days inoculation of the primary animal.     

Fiber optic probe for polarized reflectance spectroscopy in vivo: design and performance

We present the design and construction of a fiber optic probe for elastic light scattering spectroscopy in vivo with polarized excitation and polarization sensitive detection. The performance of the fiber probe is evaluated using a suspension of polystyrene spheres placed atop a diffusely scattering substrate, and it demonstrates that the size-dependent characteristics of the scatterers can be extracted in the presence of a highly diffusely scattering background using a linear combination of forward and backward Mie scattering components of the scatterers. Subsequently, Mie theory calculations are performed over a broad range of diagnostically relevant parameters of nuclei-mean diameter, size distribution, and relative refractive index-to understand how the polarized reflectance measurements with the fiber probe can be used to extract morphological information about epithelial tissue. Finally, the feasibility of in vivo measurements with the fiber optic based polarization sensitive light scattering spectroscopy is demonstrated.     

Ontogenetic transition in fetal wound transforming growth factor-beta regulation correlates with collagen organization

Fetal rat skin transitions from scarless fetal-type repair to adult-type repair with scar between day 16 (E16) and day 18 (E18) of gestation (term = 21.5 days). Deficient transforming growth factor (TGF)-beta 1 and -beta 2 injury response has been proposed as a mechanism for scarless fetal-type repair. However, previous fetal studies have inconsistently reported the degree of TGF-beta induction after injury. To minimize developmental variables in fetal versus adult TGF-beta regulation, we narrowed our study to wounded fetal animals. We hypothesize that TGF-beta ligand and receptor expression will be differentially regulated during the transition from early gestation (E16) wounds manifesting scarless fetal-type repair to late gestation (E19) wounds manifesting adult-type repair with scar. In this study, decreased and rapidly cleared TGF-beta 1 and -beta 2 expression accompanied by increased and prolonged TGF-beta 3 levels in wounded E16 animals correlated with organized collagen deposition. In contrast, increased and prolonged TGF-beta 1 and -beta 2 expression accompanied by decreased and delayed TGF-beta 3 expression in wounded E19 animals correlated with disorganized collagen architecture. Similarly, expression of TGF-beta receptors type I and II were also increased or prolonged in E19 animals. Our results implicate increased TGF-beta 1, -beta 2, and decreased TGF-beta 3 expression, as well as increased type I and II receptor expression in late gestation fetal scar formation.     

T-cell-activation inhibitors in rheumatoid arthritis

As rheumatoid arthritis (RA) is a chronic inflammatory disabling disease and a cure is not available, optimisation of therapeutic strategies is mandatory. Within recent years many new details of the inflammatory cascade(s) have been elaborated, leading to new therapeutic options such as neutralisation of tumour necrosis factor-alpha (TNFalpha). T-cell inhibition is another new approach to the treatment of RA. However, it is important to note two points: first, the role of T lymphocytes in the initiation and/or perpetuation of RA is still debated controversially. Second, there are few truly T-cell-specific agents that have proven to be effective and are established in the treatment of inflammatory disorders. Leflunomide may be considered one such agent; another in development is the fusion protein CTLA4-Ig. From a clinical perspective, studies demonstrating efficacy of these agents might represent the strongest support for a role of T cells in RA. In addition to leflunomide and CTLA4-Ig, therapeutic agents with activity against T cells, including anti-CD4 antibodies, cyclosporin, tacrolimus and T-cell receptor (TCR)-Vbeta-chain vaccination strategies, have been studied in patients with RA. Combination therapies including any of these T-cell-activation inhibitors with non-T-cell-specific agents such as methotrexate, antimalarials or anti-TNFalpha biologicals may prove the most effective strategies in controlling this complex disease.     

Histamine release during induction of anaesthesia and preparation for operation in patients undergoing general surgery: Incidence and clinically severe cases

Histamine release events were shown in a prospective randomized controlled trial in patients undergoing elective general surgery with an extraordinarily high incidence: 73 per cent. This high incidence was explained by several factors: — the sample size which was much greater than in previous studies — the improved plasma histamine assay — the precise definition of histamine release in clinical conditions and its measurement at the top of Bateman functions — the standardized induction of anaesthesia and preparation of the surgical patient — and finally the considerable number of cancer patients since more than 60% of the reactions >5 ng/ml occurred in this group which comprised only 20% of the study population.

Two cases of life-threatening anaphylactoid reactions occurred in this trial corresponding to an incidence of 1 per cent. This was — again — very high compared to previous epidemiological studies. Both cases were again cancer patients and occurred in the placebo group — information given by the external study advisory group for further treatment of the individual patient.

The data on the high incidence of histamine release including the high incidence of life-threatening reactions favourrationally a preoperative H₁ ⁻+H₂-prophylaxis with the drugs used in this study: dimetindene and cimetidine. The question of the incidence was one of the unsettled problems which led to this trial. Analysis of the first 180 patients already answered this question more than we had ever expected.