Improving Perfusion Measurement in DSC-MR Imaging with Multiecho Information for Arterial Input Function Determination.

BACKGROUND AND PURPOSE: Clinical measurements of cerebral perfusion have been increasingly performed with multiecho dynamic susceptibility contrast-MR imaging techniques due to their ability to remove confounding T1 effects of contrast agent extravasation from perfusion quantification. However, to this point, the extra information provided by multiecho techniques has not been used to improve the process of estimating the arterial input function, which is critical to accurate perfusion quantification. The purpose of this study is to investigate methods by which multiecho DSC-MRI data can be used to automatically avoid voxels whose signal decreases to the level of noise when calculating the arterial input function. MATERIALS AND METHODS: Here we compare postprocessing strategies for clinical multiecho DSC-MR imaging data to test whether arterial input function measures could be improved by automatically identifying and removing voxels exhibiting signal attenuation (truncation) artifacts. RESULTS: In a clinical pediatric population, we found that the Pearson correlation coefficient between ΔR2* time-series calculated from each TE individually was a valuable criterion for automated estimation of the arterial input function, resulting in higher peak arterial input function values while maintaining smooth and reliable arterial input function shapes. CONCLUSIONS: This work is the first to demonstrate that multiecho information may be useful in clinically important automatic arterial input function estimation because it can be used to improve automatic selection of voxels from which the arterial input function should be measured.

On the Use of DSC-MRI for Measuring Vascular Permeability.

BACKGROUND AND PURPOSE: Contrast agent extravasation has been shown to confound brain tumor perfusion measurements with DSC-MR imaging, necessitating the use of correction techniques (eg, Weisskoff, Bjornerud). Leakage parameters (K2 and K(a)) postulated to reflect vessel permeability can be extracted from these correction methods; however, the biophysical interpretation of these parameters and their relationship to commonly used MR imaging measures of vascular permeability (eg, contrast agent volume transfer constant, [K(trans)]) remain unclear. Given that vascular density, as assessed by blood volume, and vascular permeability, as reflected by K(trans) (and potentially K2 or K(a)), report on unique and clinically informative vascular characteristics, there is a compelling interest to simultaneously assess these features. MATERIALS AND METHODS: We acquired multiecho DSC-MR imaging data, allowing the simultaneous computation and voxelwise comparison of single- and dual-echo derived measures of K2, K(a) and K(trans) in patients with glioma. This acquisition enabled the investigation of competing T1 and T2* leakage effects and TE dependency on these parameters. RESULTS: K2 and K(a) displayed nonsignificant (P = .150 and P = .060, respectively) voxelwise linear correlations with K(trans), while a significant (P < .001) inverse relationship was observed between K2 and Ka (coefficient of determination [r(2)] = 0.466-0.984). Significantly different (P < .005) mean estimates were found between voxels exhibiting predominately T1 and T2* effects for K2 and K(a). K(trans), however, was observed to be similar between these voxels (0.109 versus 0.092 minutes(-1)). Significant differences (P < .001) in extracellular-extravascular volume fraction (v(e)) (0.285 versus 0.167) were also observed between cohorts. Additionally, K2 and K(a) were found to have a significant quadratic relationship (P = .031 and P = .005, respectively) with v(e). CONCLUSIONS: Estimates of vascular permeability in brain tumors may be simultaneously acquired from multiple-echo DSC-MR imaging via K(trans); however, caution should be used in assuming a similar relationship for K2 and K(a).

World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines for evaluating the efficacy of anticoccidial drugs in chickens and turkeys.

These guidelines have been written to aid in the design, implementation and interpretation of studies for the assessment of drug efficacy against Eimeria species in chickens and turkeys. The information provided deals with many aspects of how to conduct controlled studies in battery cages (dose determination), floor pens (dose confirmation), and commercial facilities (field effectiveness studies), the selection of birds, housing, feeding, preparation of medicated rations, record keeping, diagnostic techniques, and methods for the preparation, maintenance and use of parasites. These guidelines are also intended to assist investigators in conducting specific studies, provide specific information for registration authorities involved in the decision-making process, assist in the approval and registration of new anticoccidial drugs, and facilitate the world-wide adoption of standard procedures.

Use of hepatitis A vaccine in a community-wide outbreak of hepatitis A.

Hepatitis A outbreaks in communities are often difficult to control. From July 1994 through June 1995, 676 cases of hepatitis A were reported in Shelby County, Tennessee. With the licensure of a hepatitis A vaccine in February 1995, a new tool for outbreak control became available. During August-October 1995, a mass vaccination campaign was conducted. A total of 34,054 children received the first dose of hepatitis A vaccine. From December 1995 through December 1996, the number of hepatitis A cases reported inside the intervention area declined by 64%; outside the intervention area, the number of cases declined by 40%. The precise contribution of the vaccine campaign to the decline in the number of outbreak cases is difficult to quantify because community outbreaks often wane over time. The vaccine campaign may have hastened the decline of the number of outbreak cases. Future interventions should consider an earlier campaign with greater vaccine coverage.

An evaluation of fructooligosaccharide in diets for broiler chickens and effects on salmonellae contamination of carcasses.

Two similar trials were conducted to evaluate the effects of dietary inclusion of fructooligosaccharide (FOS) on live performance and carcass characteristics of broilers and on incidence and level of salmonellae on prechill broiler carcasses. The FOS was fed at two levels (0 and .375%) in a complete factorial arrangement with two levels (0 and 55 mg/kg) of bacitracin methylene disalicylate (BMD) in nutritionally complete diets. Broilers were grown to 49 days of age, and samples were processed to determine dressing percentage, abdominal fat content, and most probable number salmonellae on prechill carcasses. The addition of FOS to nutritionally complete broiler diets at .375% had little consistent effect on growth rate, feed utilization, mortality, carcass dressing percentage, abdominal fat content, or incidence or severity of salmonellae contamination of processed broiler carcasses. There appeared to be an antagonism between FOS and BMD on both live performance and salmonellae contamination of processed broiler carcasses.

Research note: does compensatory growth occur following withdrawal of salinomycin from the diet of broilers?

Two floor pen studies were conducted to determine whether compensatory growth occurs following withdrawal of the anticoccidial drug salinomycin from the feed of broilers reared to 46 days of age. There were no significant differences in weight gain or feed conversion between medicated and unmedicated birds whether overall performance or performance during the 1-wk withdrawal period was measured. Feed intake of birds given salinomycin, however, was significantly lower than that of unmedicated birds, and feed intake following withdrawal was greater than that of birds still receiving the drug.

Effects of protein and amino acid level fed zero to forty-two days on response of broilers to protein and amino acid levels fed forty-two to forty-nine days of age.

Three studies were conducted to evaluate the effect of protein and amino acid (AA) levels fed 0 to 42 days posthatch on response of broiler chickens to levels of protein and AA fed during the finisher period. Birds were grown to 42 days on diets formulated to contain a minimum of 105 or 120% of recommended AA levels, and then randomly assigned to diets formulated to contain a minimum of 70, 80, 90, 100, 110, or 120% of recommended AA levels for 42 to 49 days. No minimum protein level was imposed on the diets. Body weight, feed intake, feed utilization, dressing percentage, abdominal fat content, and parts yield were determined. The protein and AA level fed 0 to 42 days had significant effects on 42- and 49-day body weight and 42- to 49-day feed intake of male but not female broilers. However, there was no interaction of protein and AA levels fed 0 to 42 days on response to protein and AA levels fed 42 to 49 days for these criteria. Weight gain, feed intake, and feed utilization of both males and females 42 to 49 days were significantly influenced by protein and AA levels fed during this time; protein and AA requirements of females during this time appeared to be equal to, or greater than, those of the male broiler. Although there were significant interactions of protein and AA levels 0 to 42 and 42 to 49 days on various carcass parameters for both male and female broilers, these followed no consistent pattern. Protein and amino acid levels fed 0 to 42 days had a significant influence on both quantity and percentage of abdominal fat in both male and female broilers processed at 49 days but not on any other carcass parameters. The protein and AA levels fed 42 to 49 days had a significant effect on both quantity and percentage of abdominal fat in male but not female broilers. The protein and AA levels fed 42 to 49 days significantly influenced quantity but not percentage of breast meat in male but not female broilers. The results of the current study indicate that there was minimal carryover effect of protein and AA levels fed 0 to 42 days on response to AA levels fed 42 to 49 days.

Effects of dietary amino acid level and duration of finisher period on performance and carcass content of broilers forty-nine days of age.

Two studies were conducted to evaluate feeding reduced levels of amino acids (AA) to broilers during the finisher period. Birds grown to 42 days on nutritionally complete diets were fed diets formulated to contain a minimum of 70, 80, 90, 100, or 110% of recommended AA levels for periods of 3, 5, or 7 days prior to slaughter at 49 days of age. Body weight, feed intake, feed utilization, dressing percentage, and abdominal fat content were determined. For finisher periods of 3 to 5 days, a reduction in recommended dietary AA levels may be utilized without impairment of body weight gains of broilers. Extending the finisher period to 7 days resulted in significant (P less than .05) reduction of body weight gains on diets with AA levels less than 90% of recommended levels. Feed utilization was more sensitive to reduction in AA levels and may be affected adversely even by a 5-day withdrawal period. Dressing percentage was reduced in some instances, and abdominal fat generally increased when reduced AA levels were fed. The economics of feeding reduced AA levels must be considered in evaluating the results of the present studies.

Effects of bird density on Salmonella contamination of prechill carcasses.

Two similar trials were conducted to evaluate the effects of bird density on Salmonella contamination of processed broilers. Commercial strain broiler chicks were reared in floor pens on new litter at densities of 557, 619, 697, 796, 929, and 1,115 cm2 per bird. Twenty percent of the chicks in each density were gavaged directly into the crop with .5 mL of 10(8) nalidixic-acid-resistant (NAR) Salmonella typhimurium on Day 2. Twenty percent of the uninoculated birds in each density category were processed at 42 days. Prechill carcasses were evaluated for NAR Salmonella incidence using the whole carcass rinse technique and a mechanical shaking device. The resulting NAR Salmonella contamination rates (from lowest to highest bird densities) were as follows, 55, 4.2, 35.7, 34.3, 88.9, and 20% in Trial 1; and 30, 20.8, 28.6, 50, 58.3, and 30% in Trial 2. A random sample of the prechill carcasses of gavaged birds indicated a contamination rate of 13.8% in Trial 1 and 61.1% in Trial 2. The NAR Salmonella contamination rates of the prechill carcasses did not appear to be affected by the bird densities evaluated in these trials. Feed intake and body weight at 42 days were adversely affected by the highest bird density, but feed utilization was not affected.

Effects of dietary lactose on incidence and levels of salmonellae on carcasses of broiler chickens grown to market age.

Two trials were conducted to evaluate the effects of lactose in the diet of broilers grown to market weights on incidence and levels of salmonellae on the carcass. Lactose was substituted for sand in otherwise nutritionally complete diets at levels of 0, 2.5, 5, and 7.5% and fed from day-old to 49 days of age. Birds were reared on used (Trial 1) or new (Trial 2) litter and inoculated via the drinking water on Days 2, 7, and 14 with 10(8) cfu/mL Salmonella typhimurium (ATCC 14028). At 50 days, 12 (Trial 1) or 24 (Trial 2) birds per treatment were processed and prechill carcasses were evaluated for salmonellae incidence and level by the most probable number (MPN) method. Body weight of male broilers was significantly reduced by feeding diets containing up to 7.5% lactose. Feed intake of broilers fed diets containing lactose was significantly reduced and feed utilization improved, suggesting that lactose provided some metabolizable energy. The degree of litter caking was significantly increased, and cecal pH was significantly decreased as dietary lactose increased. Prechill carcases of broilers fed diets with 7.5% lactose had significantly higher levels of salmonellae than did prechill carcasses of broilers fed 0% lactose. The results of the present study suggest that supplementing poultry diets with lactose is not a viable means in itself of reducing or eliminating salmonellae incidence or levels on processed broiler carcasses.

Comparison of different anticoccidials on processing characteristics and parts yield of broiler chickens.

Broilers were grown to 42 days of age on diets supplemented with salinomycin (60 mg/kg), monensin (99 mg/kg), or halofuginone (3 mg/kg) and continued on unmedicated diets to 49 days of age. There were no significant (P greater than .05) differences among anticoccidials in final body weight, feed conversion, or mortality rates. Samples of birds were processed for dressing percentage and parts yield. Both males and females fed salinomycin had significantly higher breast meat yield as a percentage of postchill weight than those fed halofuginone but not those fed monensin; differences were not significant for breast meat yield of males or females fed monensin or halofuginone. Males fed halofuginone had significantly heavier leg quarters than those fed salinomycin but not those fed monensin. Females fed salinomycin had significantly higher water uptake during chill than those fed monensin or halofuginone. Results of the present study indicate that the anticoccidial used in growing broilers may influence some carcass yield parameters.

Research note: fumaric acid enhances performance of broiler chickens.

Two studies were conducted to examine the effects of dietary inclusion of fumaric acid on performance and carcass composition of broiler chickens. Fumaric acid was added to nutritionally complete diets at levels of 0, .125, .25, and .5% and fed from 1 to 49 days under simulated commercial conditions. In one trial, samples of birds were processed to determine dressing percentage and abdominal fat content. In the first trial (mixed sex broilers), the addition of .125% fumaric acid significantly (P less than .05) improved 49-day body weight of females and average weight gain of both sexes with no effect on feed utilization. Feed consumption was significantly increased when diets contained .125 or .50% fumaric acid. In the second trial (male broilers), 49-day body weight was significantly (P less than .05) improved by the addition of .125 and .25% fumaric acid. There were no significant differences in feed consumption; feed utilization was improved by the addition of all levels of fumaric acid. Dietary fumaric acid had no adverse effects on dressing percentage, abdominal fat content, or mortality rate.

Effects of dietary amino acid levels on performance and carcass composition of broilers 42 to 49 days of age.

Broilers were grown to 42 days on nutritionally complete diets. From 42 to 49 days in two trials, broilers were fed diets formulated to contain 70, 80, 90, 100, 110, or 120% of recommended amino acid (AA) values. In four additional trials, the same AA levels were fed; in addition, Met and Lys were added to diets formulated to contain 70, 80, and 90% to equal levels of the 110% AA diet. Body weight gain (BWG), feed consumption (FC), feed conversion (FCR), dressing percentage (DP), and abdominal fat (AF) were measured. From 42 to 49 days, dietary AA levels had little effect on BWG, DP, or AF of female broilers. When male broilers were fed diets containing less than 100% of the recommended AA levels, BWG was reduced and AF increased. Broiler FC increased and FCR decreased as the AA level of the diet decreased. The addition of Met and Lys to the 90% AA diet improved performance; however, the addition of Met and Lys to the 70% AA diet had no beneficial effect. Amino acid levels may be reduced in broilers diets fed from 42 to 49 days; however, male broilers are more sensitive than females to reductions in AA levels during this period.

Effects of dietary amino acid levels on bone development in broiler chickens.

Studies with several species suggest that dietary protein may influence bone calcification. Six pens of six male broilers in two consecutive trials were fed from 1 to 21 days either .5 or 1.0% Ca in diets with 80, 90, 100, 110, or 120% of the amino acid (AA) standards suggested by Thomas et al. in 1986 at a constant .46% nonphytate P. The BW and feed conversion rate (FCR) were determined, and bone measurements were taken. Both AA and Ca levels influenced BW with an interaction of the two factors. The Ca level, but not AA level, influenced FCR. The lower Ca level inhibited feed intake. Increasing AA levels reduced bone ash but did not affect tibia breaking strength. There was an interaction of AA and Ca on tibia ash, tibia weight, and tibia length. The higher AA levels supported normal linear growth of the tibia but decreased rate of calcification, especially in the diets with .5% Ca. In diets with marginal Ca levels, higher AA levels may reduce bone calcification.

Effects of formic acid or calcium formate in feed on performance and microbiological characteristics of broilers.

Three experiments were conducted to determine the effects of feeding broilers formic acid (FA) or calcium formate (CF) on performance and microbiological characteristics of broilers. Live bird performance was not adversely affected by feeding up to 1.0% FA or 1.45% CF. In Experiment 1, levels of salmonellae in carcass and cecal samples were significantly reduced by feeding birds .36% CF. Salmonellae were not isolated from any of the carcasses of birds fed .36% CF. Similar reductions were not noted for total organisms or presumptive coliforms. In Experiment 2, feeding .36% CF nonsignificantly reduced levels of salmonellae in carcass and cecal samples, but again, levels of total organisms and coliforms were not reduced. In Experiment 3, salmonellae in the ceca or in the carcass rinse fluid were not reduced by feeding .36% CF.

Effects of different antibiotics on performance, processing characteristics, and parts yield of broiler chickens.

Broilers were grown to 49 days of age on diets supplemented with bambermycins (BAM, 2.2 ppm), bacitracin methylene disalicylate (BMD, 27.5 ppm), virginiamycin (VM, 11 ppm), or an unmedicated control. Samples of birds were processed for dressing percentage and parts yield. There were no significant (P greater than .05) effects of antibiotics on final body weight, feed conversion, or mortality. In male broilers, BMD and VM significantly (P less than or equal to .05) increased dressing percentage and percentage yield and reduced the skeletal rack as a percentage of postchill weight compared to those fed the nonmedicated control. All antibiotics significantly increased breast skin weight and breast skin as a percentage of postchill weight of as compared with those fed the unmedicated control. In female broilers, BAM and BMD significantly increased dressing percentage and percentage yield and increased breast weight and breast as percentage of postchill weight as compared with those fed the unmedicated control diet. Females fed BMD also had significantly heavier leg quarters and breast skin than those fed the unmediated control. Females fed VM had increased breast skin weight and breast skin as a percentage of postchill weight than those fed the unmedicated control. The results of the present study indicate that antibiotics may influence dressing percentage and parts yield in the absence of improvements in body weight gain or feed utilization.

Use of simple tasks to test for impairment of complex skills by a sedative.

Examination of the effect of three doses of pentobarbital on the comparative performance of a complex psychomotor task with two simple neuromotor tasks, i. e., standing steady and pendulum eye tracking, revealed a high correlation. These simple tasks could be used as measures of intoxication since they do not require extensive training. Examination of the complex task impairment blood level ratio revealed that impairment relative to blood level was much greater in the absorption phase. This changing ratio underscores the point that blood levels alone are not an adequate estimate of intoxication.