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Kevin Sanders

Publications and source records attributed to Kevin Sanders.

6 recordsLinked to original sources
PubMed2006

Novel method to calculate pulmonary compliance images in rodents from computed tomography acquired at constant pressures.

Our goal was to develop a method for generating high-resolution three-dimensional pulmonary compliance images in rodents from computed tomography (CT) images acquired at a series of constant pressures in ventilated animals. One rat and one mouse were used to demonstrate this technique. A pre-clinical GE flat panel CT scanner (maximum 31 line-pairs cm(-1) resolution) was utilized for image acquisition. The thorax of each animal was imaged with breath-holds at 2, 6, 10, 14 and 18 cm H2O pressure in triplicate. A deformable image registration algorithm was applied to each pair of CT images to map corresponding tissue elements. Pulmonary compliance was calculated on a voxel by voxel basis using adjacent pairs of CT images. Triplicate imaging was used to estimate the measurement error of this technique. The 3D pulmonary compliance images revealed regional heterogeneity of compliance. The maximum total lung compliance measured 0.080 (+/-0.007) ml air per cm H2O per ml of lung and 0.039 (+/-0.004) ml air per cm H2O per ml of lung for the rat and mouse, respectively. In this study, we have demonstrated a unique method of quantifying regional lung compliance from 4 to 16 cm H2O pressure with sub-millimetre spatial resolution in rodents.

Algorithms↗
PubMed2006

Dynamic ventilation imaging from four-dimensional computed tomography.

A novel method for dynamic ventilation imaging of the full respiratory cycle from four-dimensional computed tomography (4D CT) acquired without added contrast is presented. Three cases with 4D CT images obtained with respiratory gated acquisition for radiotherapy treatment planning were selected. Each of the 4D CT data sets was acquired during resting tidal breathing. A deformable image registration algorithm mapped each (voxel) corresponding tissue element across the 4D CT data set. From local average CT values, the change in fraction of air per voxel (i.e. local ventilation) was calculated. A 4D ventilation image set was calculated using pairs formed with the maximum expiration image volume, first the exhalation then the inhalation phases representing a complete breath cycle. A preliminary validation using manually determined lung volumes was performed. The calculated total ventilation was compared to the change in contoured lung volumes between the CT pairs (measured volume). A linear regression resulted in a slope of 1.01 and a correlation coefficient of 0.984 for the ventilation images. The spatial distribution of ventilation was found to be case specific and a 30% difference in mass-specific ventilation between the lower and upper lung halves was found. These images may be useful in radiotherapy planning.

Algorithms↗
PubMed2005

Quantification of regional ventilation from treatment planning CT.

PURPOSE: We describe a method of quantifying regional ventilation from the radiotherapy treatment planning computed tomography (CT) images, with the goal of developing functional images for treatment planning and optimization. METHODS AND MATERIALS: A series of exhalation breath-hold (eBH-CT) and inhalation breath-hold (iBH-CT) CT images obtained using a feedback-guided breath-hold technique for radiotherapy treatment planning was selected. The eBH-CT was mapped on a voxel-by-voxel basis to the iBH-CT using a deformable image registration algorithm. By using the average CT number over a 3 mm(3) region surrounding each pair of mapped voxels, the change in fraction of air per voxel (i.e., regional ventilation) was calculated. This methodology was applied to a series of 22 patients. The calculated total ventilation was compared to the change in contoured lung volumes between the exhalation and inhalation CTs (measured tidal volume). RESULTS: A significant correlation was found between the calculated and measured tidal volumes for the left (R = 0.982) and right (R = 0.985), and for both lungs combined (R = 0.985). In the resulting images, the regional ventilation was highly variable and corresponded with the spatial distribution of differences in the CT values (Hounsfield units) between the eBH-CT and the iBH-CT images. CONCLUSIONS: A method of quantifying regional ventilation from radiotherapy treatment planning CT data sets was demonstrated. The ventilation images can be used in plan optimization to minimize injury to functioning lung.

Algorithms↗
PubMed2004

Pharmacodynamic target attainment analysis against Streptococcus pneumoniae using levofloxacin 500 mg, 750 mg and 1000 mg once daily in plasma (P) and epithelial lining fluid (ELF) of hospitalized patients with community acquired pneumonia (CAP).

The pharmacokinetics and pharmacodynamics of levofloxacin in patients with respiratory infections such as community-acquired pneumonia (CAP) are poorly documented. This work aimed at assessing the pharmacodynamic target attainment against Streptococcus pneumoniae using levofloxacin 500 mg, 750 mg and 1000 mg administered once daily in plasma (P) and epithelial lining fluid (ELF) of hospitalized patients with community acquired pneumonia. The pharmacokinetics of levofloxacin in elderly (>/=65 years) compared with younger patients (<65 years) hospitalized with CAP were simulated. Susceptibility data with S. pneumoniae from our ongoing national surveillance study (Canadian Respiratory Organism Susceptibility Study-CROSS) were then used to produce pharmacodynamic indices of AUC(0-24)/MIC(all.) Monte Carlo simulations were then used to analyse target attainment of levofloxacin using doses of 500 mg, 750 mg and 1000 mg once daily to achieve free drug AUC(0-24)/MIC(all) >/= 30-100 versus S. pneumoniae in patients with CAP. Pharmacokinetics of levofloxacin simulated after 500 mg, 750 mg and 1000 mg once daily dosing resulted in levofloxacin volume of distribution: elderly patients = younger patients, while levofloxacin clearance was: elderly patients < younger patients. Levofloxacin t(1/2) values were longer in elderly patients (9.8 +/- 2.5h) than younger patients with CAP (7.4 +/- 2.5h). Free levofloxacin AUC(0-24) as well as AUC(0-24)/MIC(all) for S. pneumoniae were higher in elderly patients than younger patients. Monte Carlo simulation using levofloxacin 500 mg yielded probabilities of achieving free-drug AUC(0-24)/MIC(all) of 30 in P and ELF (95.7% and 98.1%) in elderly and younger patients (72.7% and 80.6%) respectively. Levofloxacin 750 mg and 1000 mg once daily had probability of achieving free-drug AUC(0-24)/MIC(all) of 30 in P/ELF of 98.1%/98.6% and 99.2%/99.0%, respectively, in elderly patients compared with 89.9%/94.1% and 95.2%/96.5%, respectively, for younger patients. Probability of achieving of AUC(0-24)/MIC(all) of 100 in P or ELF was very low in both patient populations at different doses except in the case of elderly patients receiving levofloxacin in a dose of 1000 mg once daily P/ELF of 78.5%/87.0%. We conclude that levofloxacin pharmacokinetics in elderly patients with CAP are markedly different from those of younger patients. Levofloxacin 750 mg OD provides high probabilities of achieving free-drug AUC(0-24)/MIC(all) of 30 in both plasma and epithelial lining fluid in patients with CAP including younger patients. Levofloxacin 500 mg OD provides high probabilities of achieving free-drug AUC(0-24)/MIC(all) of 30 in elderly patients with CAP, although we favour the 750 mg dosing in these patients as well. Levofloxacin 750 mg OD results in high probability of pharmacodynamic target attainment and improved bacteriological outcome against S. pneumoniae in patients with CAP.

Adolescent↗