DEVELOPMENT OF AN AUTOMATED 12-8 BIT CONVERSION ALGORITHM FOR DISPLAYING AND ARCHIVING SCANNED RADIOGRAPHS

The lossless capture of the entire range of optical densities encountered in a radiograph can require up to 4000 individual shades of gray. Most inexpensive computer displays, and most grayscale image formats contain only 256 gray shades. To use these systems, a look up table must be generated to display the scanned image, which maps the approximately 4000 gray shades in the digitized radiograph to the 256 gray shades on the monitor. However, if this conversion is inappropriately performed, much of the information contained in the original image could be lost. This study was undertaken to develop an histogram equalization algorithm that would automatically convert the 4000 gray shade digitized radiograph into a 256 gray shade image file, without perceptable loss of diagnostic information or image quality.     

The effect of Danish seine selectivity and retention on growth estimates of tiger flathead <Emphasis Type="Italic">Platycephalus richardsoni</Emphasis>

This work demonstrates the correction of gear-selectivity and retention effects in estimation of growth in fish populations. The selectivity bias can be removed from length-at-age and length increment data. To correct for bias, a maximum-likelihood estimator that incorporates gear selectivity, a size-dependent retention function and several stochastic growth models are provided. The estimator allows the use of joint samples collected by fishing gears with different selectivity, which increases sample size and data representativeness, and thus improves accuracy of population parameter estimates. Data collected from retained tiger flathead caught by Danish seine gear were used for numerical analysis of the selectivity bias. Stock assessment implications of bias in growth estimation are discussed.     

Marking live feeds with inert metal oxides for fish larvae feeding and nutrition studies

Yttrium oxide (Y₂O₃), ytterbium oxide (Yb₂O₃), lanthanum oxide (La₂O₃) and dysprosium oxide (Dy₂O₃) were evaluated as potential live feed markers for feeding and nutrition studies with fish larvae, by determining the uptake and depletion of markers over time in two trials, and quantifying ingestion of Y₂O₃‐marked rotifers (Branchionus plicatilis) by Atlantic cod (Gadus morhua) in a third trial. In the first two trials, Artemia nauplii and rotifers quickly took up markers within 10 min to concentrations useful for nutrition studies (>2% dry weight). There was no significant difference (P>0.05) among temperatures in depletion of markers (10, 15, 20 °C) with Artemia or rotifers. Depletion from rotifers was not significantly different (P>0.05) between 5 and 20 min nor between 5 and 30 min for Artemia when marked at a concentration of 50 mg of marker per litre of seawater. In the second trial, rotifers and Artemia were marked with a higher concentration (250 mg L^?1) and allowed to deplete for a longer time (90 min). In the third trial, visual estimates of Artemia consumed by Atlantic cod larvae were similar to consumption estimates determined by analysis of Y₂O₃‐marked Artemia using inductively coupled plasma optical emission spectroscopy (r²=0.77).     

Priming of multiple T cell subsets by modified-live and inactivated bovine respiratory syncytial virus vaccines

T cell activity is a critical component of immunity to bovine respiratory syncytial virus (BRSV). We tested the effects of immunization by modified-live and inactivated BRSV vaccines on cell-mediated and humoral immunity in young calves. The two forms of vaccine stimulated similar serum neutralizing antibody production, although the early kinetics of those responses differed. CD4+, CD8+, and gammadelta T cells were analyzed before and after immunization for BRSV-specific in vitro recall responses, as evaluated by CD25 upregulation measured by flow cytometry. Modified-live virus (MLV) primed each of the three subsets for statistically significant in vitro responses to antigen. Inactivated vaccine also primed each T cell population for significant antigen-driven CD25 upregulation, including responses by CD4+ and gammadelta T cells that were stronger and longer-lasting than those primed by MLV. Monoclonal antibody was used in additional assays to block MHC class I during incubation of BRSV antigen with peripheral blood mononuclear cells from an animal in the inactivated vaccine group. The recall response by CD8+ T cells was more inhibited by this treatment than the other subsets, further suggesting that the inactivated vaccine had primed antigen-specific CD8+ T cells. In summary, the data indicate that balanced BRSV-specific T cell responses can be induced by inactivated, as well as modified-live, conventional vaccines, which may implicate an alternative pathway of MHC class I antigen presentation.     

The Effect of Marker Location Variability on Noninvasive Canine Stifle Kinematics

Objective: Evaluate the effect of marker placement on kinematics of the canine stifle in 3 distinct hindlimb models. Study Design: In vivo biomechanical study. Animals: Normal adult mixed‐breed dogs (n=5). Methods: Ten retroreflective markers were affixed to the skin on the right rear leg of each dog to establish normal stifle kinematics. Four additional markers were placed around the greater trochanter (GT), 2 cm cranial, caudal, dorsal, and ventral to evaluate single marker placement variability on kinematic model data. Dogs were walked and trotted 5 times through the calibrated space. Sagittal flexion and extension angle waveforms were acquired during each trial with 3 models that were produced simultaneously during each gait. The GT marker was reassigned to 1 of the 4 additional locations (cranial, caudal, dorsal, and ventral) to alter the kinematic model. Comparison of sagittal flexion and extension angle waveforms was performed with Generalized Indicator Function Analysis. Results: Each model provided consistent equivalent sagittal flexion–extension data. Analysis revealed statistically significant differences between all GT locations. The differences were greatest in the cranial and caudal locations for all models. Conclusions: Deviation of the GT marker in the cranial/caudal direction from an anatomically normal position produces a greater degree of difference than deviation in a dorsal/ventral direction.     

THE USE OF99mTc RADIOAEROSOL VENTILATION AND MACROAGGREGATED ALBUMIN PERFUSION IMAGING FOR THE DETECTION OF PULMONARY EMBOLI IN THE DOG

This study was undertaken to design protocol for use of radioaerosol of technetium-99m-labeled diethylenetriaminepentacetic acid (^99mTc-DTPA) for ventilation imaging as clinical tool in the dog and to evaluate imaging characteristics in both normal dogs and dogs with simulated pulmonary embolism. Clearance of the 99mTc-DTPA radioaerosol from the lung was also evaluated. Six normal dogs were used in two phases: (1) as their own controls and (2) during pulmonary artery occlusion using Swan-Ganz catheter. Radioaerosol ventilation images were obtained and rate of clearance from normal and occluded lungs determined. Perfusion studies using technetium-99m-macroaggregated albumin (^99mTc-MAA) immediately followed. Clearance half-times (T_1/2) were found to be significantly increased (p < 0.05) in acutely occluded lungs; however, the small magnitude of this change was visually difficult to detect on the ventilation images. Good quality initial ventilation and perfusion images were obtained and provided ready evaluation of ventilation (V), perfusion (Q), and induced V/Q mismatches. A clinical case of pulmonary thromboembolic disease was also evaluated with diagnostic result, indicating that this method of V/Q scintigraphy can provide useful information in those clinical cases in which pulmonary thromboembolism is suspected.     

Thermal and mechanical nociceptive threshold testing in pregnant sheep

ObjectiveAnalgesic regimes were compared in pregnant ewes after laparotomy by measuring thermal (TT) and mechanical (MT) nociceptive thresholds.Study designProspective randomised experimental study.AnimalsPregnant ewes at 121 days gestation underwent laparotomy as part of another research project.MethodsThermal and mechanical thresholds were measured before, and 2, 6, 24 and 48 hours after surgery. Thermal stimuli were delivered to the lateral aspect of the metatarsus via a skin-mounted probe, and mechanical stimuli to the contralateral site via a pneumatically driven 1.5 mm diameter pin. Each test was performed five times, alternating thermal and mechanical stimuli, with ten minutes between thermal stimuli. At the end of surgery ewes received either: 75 μg hour^?1 transdermal fentanyl patch (medial thigh) (group FP) (n = 8), or 3 μg kg^?1hour^?1 intra-peritoneal medetomidine via an osmotic pump (group IPM) (n = 8) inserted immediately prior to closure. Data were analysed using the Kruskal–Wallis RS Test (p < 0.05). Once a significant effect was identified, pairwise comparisons were performed using paired Wilcoxon RS tests. To compensate for multiple hypotheses testing, p < 0.005 was considered significant.ResultsPrior to surgery mean ± SD TT was 56.1 ± 5.0 °C (FP) and 55.6 ± 5.0 °C (IPM); MT was 5.3 ± 2.6 N (FP) and 8.0 ± 5.0 N (IPM). In FP there was no significant change in either TT or MT over time. In IPM there was no significant change in MT over time but TT increased at two hours to 59.2 ± 3.0 °C (p = 0.003). Skin temperature (ST) ranged from 33.0 to 34.7 °C and did not change over time. There were no significant differences between groups in TT, MT or ST.Conclusions and clinical relevanceAdministration of intra-peritoneal medetomidine (3 μg kg^?1hour^?1) by an osmotic pump increases the thermal nociceptive threshold in the immediate post operative period in pregnant sheep, suggesting that this agent may have a role in providing post-operative analgesia.