PET textural features stability and pattern discrimination power for radiomics analysis: An "ad-hoc" phantoms study.

PURPOSE: The analysis of PET images by textural features, also known as radiomics, shows promising results in tumor characterization. However, radiomic metrics (RMs) analysis is currently not standardized and the impact of the whole processing chain still needs deep investigation. We characterized the impact on RM values of: i) two discretization methods, ii) acquisition statistics, and iii) reconstruction algorithm. The influence of tumor volume and standardized-uptake-value (SUV) on RM was also investigated. METHODS: The Chang-Gung-Image-Texture-Analysis (CGITA) software was used to calculate 39 RMs using phantom data. Thirty noise realizations were acquired to measure statistical effect size indicators for each RM. The parameter η2 (fraction of variance explained by the nuisance factor) was used to assess the effect of categorical variables, considering η2 < 20% and 20% < η2 < 40% as representative of a "negligible" and a "small" dependence respectively. The Cohen's d was used as discriminatory power to quantify the separation of two distributions. RESULTS: We found the discretization method based on fixed-bin-number (FBN) to outperform the one based on fixed-bin-size in units of SUV (FBS), as the latter shows a higher SUV dependence, with 30 RMs showing η2 > 20%. FBN was also less influenced by the acquisition and reconstruction setup:with FBN 37 RMs had η2 < 40%, only 20 with FBS. Most RMs showed a good discriminatory power among heterogeneous PET signals (for FBN: 29 out of 39 RMs with d > 3). CONCLUSIONS: For RMs analysis, FBN should be preferred. A group of 21 RMs was suggested for PET radiomics analysis.

Validation of a method for "dose of the day" calculation in head-neck tomotherapy by using planning ct-to-MVCT deformable image registration.

PURPOSE: The aim of this study was to test the feasibility and dosimetric accuracy of a method that employs planning CT-to-MVCT deformable image registration (DIR) for calculation of the daily dose for head and neck (HN) patients treated with Helical Tomotherapy (HT). METHODS: For each patient, the planning kVCT (CTplan) was deformably registered to the MVCT acquired at the 15th therapy session (MV15) with a B-Spline Free Form algorithm using Mattes mutual information (open-source software 3D Slicer), resulting in a deformed CT (CTdef). On the same day as MVCT15, a kVCT was acquired with the patient in the same treatment position (CT15). The original HT plans were recalculated both on CTdef and CT15, and the corresponding dose distributions were compared; local dose differences <2% of the prescribed dose (DD2%) and 2D/3D gamma-index values (2%-2mm) were assessed respectively with Mapcheck SNC Patient software (Sun Nuclear) and with 3D-Slicer. RESULTS: On average, 87.9%±1.2% of voxels were found for DD2% (on average 27 slices available for each patient) and 94.6%±0.8% of points passed the 2D gamma analysis test while the 3D gamma test was satisfied in 94.8%±0.8% of body's voxels. CONCLUSIONS: This study represents the first demonstration of the dosimetric accuracy of kVCT-to-MVCT DIR for dose of the day computations. The suggested method is sufficiently fast and reliable to be used for daily delivered dose evaluations in clinical strategies for adaptive Tomotherapy of HN cancer.

The Shape of Parotid DVH Predicts the Entity of Gland Deformation During IMRT for Head and Neck Cancers.

The Jacobian of the deformation field of the registration between images taken during Radiotherapy is a measure of compression/expansion of the voxels within an organ. The Jacobian mean value was applied to investigate possible correlations between parotid deformation and anatomical, clinical and dosimetric parameters. Data of 84 patients were analyzed. Parotid deformation was evaluated through Jacobian maps of images taken at the start and at the end of the treatment. Several clinical, geometrical and dosimetric factors were considered. Correlation between Jacobian mean value and these parameters was assessed through Spearman's test. Univariate and multivariate logistic analyses were performed by considering as the end point the first quartile value of the Jacobian mean value. Parotid dose volume histograms were stratified according to gland deformation, assessing the most predictive dose-volume combination. At multivariate analysis, age (p = 0.02), overlap between tumor volume and parotid gland (p = 0.0006) and the parotid volume receiving more than 10 Gy (p = 0.02) were found as the best independent predictors, by considering Jacobian mean value fist quartile, the parotid volume receiving more than 10 Gy and 40 Gy were found as the most predictive dosimetric parameters. Parotid glands were divided in three different sub-groups (bad-, medium- and good dose volume histogram). The risk to have Jacobian means value lower than first quartile was 39.6% versus 19.6% versus 11.3% in these three groups. By including in the multivariate analysis this "dose volume grouping" parameter, age and bad dose volume histogram were found as the most predictive parameters for large shrinkage. The pattern of parotid deformation may be well predicted by some pre-treatment variables; a bad dose volume histogram seems the most important predictor.

A comparison of two blood culture procedures for the isolation of staphylococci in a paediatric intensive care unit.

Blood culture results obtained between January 2000 and July 2003 were reviewed for 1360 patients in a paediatric intensive care unit (PICU). The BacT/Alert FA aerobic medium was used with a blood volume of 1.5 mL for the first 23 months, and the BacT/Alert PF paediatric medium was used with a 0.5-mL volume for the remaining 18 months. The isolation rates were similar during both periods (13.4% vs. 13.1%), and staphylococci were the most common isolates (72.8%). There was a shorter time to detection of staphylococci with the smaller-volume (PF) procedure, which thus seems suitable for use in the diagnosis of staphylococcal bacteraemia in the PICU.

Use of the E test to assess synergy of antibiotic combinations against isolates of Burkholderia cepacia-complex from patients with cystic fibrosis.

Treatment of Burkholderia cepacia-complex infections in cystic fibrosis patients is problematic, since the microorganism is often resistant to most antimicrobial agents. In this study, the Epsilometer test, or E test, was used to assess the activity of antimicrobial combinations against Burkholderia cepacia-complex. In a preliminary evaluation, the E test was compared to the checkerboard method using 10 test organisms. Synergy testing by the E test was then performed on 131 clinical isolates of Burkholderia cepacia-complex using various combinations of antimicrobial agents. Agreement between the E test and the checkerboard method was 90%. The rate of resistance to individual agents ranged from 48% for meropenem to 100% for tobramycin, chloramphenicol, and rifampin. In 71.6%, 15.6%, and 12.6% of the test evaluations performed, the combinations tested resulted in additivity/indifference, synergism, and antagonism, respectively. The highest rates of synergy were observed with combinations of ciprofloxacin-piperacillin (44%), rifampin-ceftazidime (33%), chloramphenicol-ceftazidime (22%), cotrimoxazole-piperacillin/tazobactam (22%), and ciprofloxacin-ceftazidime (21%). Rates of antagonism for cotrimoxazole and chloramphenicol in combination with beta-lactam agents were higher than those observed for ciprofloxacin plus beta-lactam agents. These results suggest that the E test is a valuable and practical method to be considered for improving the identification of possible therapeutic options in cystic fibrosis patients infected with organisms belonging to the Burkholderia cepacia-complex.

[Epidemiology and sensitivity to antibiotics in paediatric respiratory infections over a 4-year period. Retrospective study of 460 H. influenzae, S. pneumoniae and M. catarrhalis strains] / Epidemiologia e sensibilita agli antibiotici in infezioni respiratorie di pazienti pediatrici in un periodo di 4 anni. Studio retrospettivo su 460 ceppi di H. influenzae, S. pneumoniae e M. catarrhalis.

H. influenzae, S. pneumoniae and M. catarrhalis are the most common bacterial pathogens causing respiratory infections in children. Resistance to antibiotics may vary according to the geographical area. It is therefore important that the resistance pattern of such pathogens is determined by surveillance studies carried out both on a national scale and by individual laboratories. In this study, we determined retrospectively the prevalence of H. influenzae, S. pneumoniae and M. catarrhalis in upper respiratory tract infections involving subjects of paediatric age, with reference to the type of clinical sample (pharingeal swab and nasal swab), symptomatology and age group. Moreover, for the above micro-organisms the pattern of sensitivity to antibiotics was assessed. In the observation period (January 1996-December 1999), at the day hospital of the Paediatric Pneumology Division of the Gaslini Institute in Genova, in 476 patients between 0 and 15 years of age a total of 460 respiratory pathogens were isolated: 164 S. pneumoniae strains, 163 of H. influenzae (96 belonging to type B and 67 non-attributable to any type) and 133 of M. catarrhalis. As regards sensitivity to antibiotics, ceftriaxone and amoxycillin/clavulanic acid proved to be the most active molecules in all the studied strains.

The effect of fresh human serum on ofloxacin bactericidal activity.

We have studied the possibility of an increase in ofloxacin bactericidal activity when it is combined with fresh human serum. The tested strains were 10 clinical isolates of Klebsiella pneumoniae. From among our strains 5 were susceptible to serum bactericidal activity and 5 were found to be resistant. We selected two serum concentrations (15 and 35%) to test against susceptible strains and two (55 and 75%) to test against resistant strains in combination with the minimum inhibitory concentration (MIC), 1/2MIC and 1/4MIC of ofloxacin. The results show a slight variability among the tested strains depending on microbiological characteristics of single strains, however, the serum + ofloxacin combination was advantageous. Only one exception was observed: a resistant strain that had an increased survival percentage against ofloxacin and serum in combination.

The activity of antistaphylococcal drugs on nosocomial Staphylococcus epidermidis.

In reporting on the activity of cephalothin, cefamandole, FCE 22101, gentamicin, netilmicin, amikacin, rifampicin, clindamycin, josamycin, ofloxacin, ciprofloxacin, vancomycin and teicoplanin on 72 Staphylococcus epidermidis strains clinically isolated in the hospital, the Authors observed a high percentage of methicillin-resistance (68.05%) as well as resistance to other important drugs such as gentamicin (72.22%), rifampicin (27.7%), clindamycin (36.1%), and josamycin (40.27%). They also recorded good inhibitory activity of the studied beta-lactam drugs. However, this activity was not confirmed against methicillin-resistant strains when the test was performed under particular technical conditions (hypertonic medium, incubation at 30 degrees C, inoculum = 10(6)). The Authors also emphasize the poor bactericidal activity against these strains. The activity of quinolones was good; the activity of vancomycin and teicoplanin was very good on all strains studied.

Microbiological indications for the treatment of Staphylococcus aureus infections.

The Authors report microbiological data on the inhibitory activity of cephalothin, cefamandole, FCE 22101, gentamicin, netilmicin, amikacin, rifampicin, clindamycin, josamycin, ofloxacin, ciprofloxacin, vancomycin and teicoplanin against 165 clinically isolated Staphylococcus aureus strains. 34 of the study strains, i.e. 20.6%, were methicillin- and oxacillin-resistant. The activity of the tested drugs was good; the presence of nosocomial strains resistant to rifampicin (12.13%), clindamycin (13.94%), josamycin (18.2%), ofloxacin (4.85%), ciprofloxacin (12.7%), gentamicin (27.3%), amikacin (9.7%), netilmicin (7.9%) was noted. The Authors emphasize the good inhibitory activity of tested beta-lactam drugs against methicillin-sensitive Staphylococci, but also the limits of these drugs against methicillin-resistant strains. The activity of vancomycin and teicoplanin on all study strains was very good.

In vitro activity of sulbactam/ampicillin and ampicillin against methicillin-sensitive and methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis.

Minimum inhibitory concentrations (MICs) of ampicillin and ampicillin + sulbactam (1:1) against 165 strains of Staphylococcus aureus and 72 strains of Staphylococcus epidermidis have been evaluated. The activity of the combination was very good. A concentration of 16 micrograms/ml + 16 micrograms/ml inhibited 96.9% of S. aureus and the 100% of S. epidermidis strains (at the same concentration ampicillin alone inhibited only 55.15% and 56.9% of S. aureus and S. epidermidis strains respectively). Activity against methicillin-resistant S. aureus (14.5%) was poor, whereas against methicillin-resistant S. epidermidis (67.2%) the combination maintained high efficacy.

Activity of xibornol against Staphylococcus aureus.

The minimal inhibitory concentrations (MIC) and the minimal bactericidal concentrations (MBC) of xibornol against 100 strains of Staphylococcus aureus, clinically isolated, have been evaluated. Xibornol has shown very good in vitro activity and a significant uniformity of the results. In fact the inhibitory and bactericidal activity range was between 2 micrograms/ml and 8 micrograms/ml.

5-Fluorocytosine and Candida yeasts.

The authors report 5-fluorocytosine's activity against 101 Candida albicans and 42 Candida non-albicans strains. They point out the drug's lower inhibitory and lethal activity against Candida non-albicans. A 1.56 microgram/ml concentration inhibits 83% of Candida albicans while only 40% of Candida non-albicans is inhibited.

Susceptibility of enterococci. I. Inhibitory and bactericidal activity of several chemoantibiotics against Streptococcus faecalis and Streptococcus faecium.

The authors present a microbiological study of 100 strains of Enterococcus (70 strains of Streptococcus faecalis and 30 strains of Streptococcus faecium) tested for susceptibility to the following antibiotics, amoxicillin, ampicillin + flucloxacillin, piperacillin, rifampicin, vancomycin, netilmicin, ofloxacin, and norfloxacin. The assessment of minimum inhibitory and minimum bactericidal concentrations of these substances indicates that all have good inhibitory activity except netilmicin, which is active at higher concentrations; with rifampicin and vancomycin showing very poor bactericidal activity. The bactericidal activity of penicillins was hard to assess because of tolerance and paradoxical effect phenomena. The quinolones showed good inhibitory and bactericidal activity.

Susceptibility of enterococci. II. Inhibitory and bactericidal activity of drugs in combination against Streptococcus faecalis and Streptococcus faecium.

The microbiological utility of antibiotic combinations against Streptococcus faecalis and Streptococcus faecium strains was studied. The drugs used were netilmicin + amoxicillin (20 strains); netilmicin + piperacillin (20 strains); netilmicin- + vancomycin (20 strains); netilmicin + rifampicin (20 strains). Netilmicin used in combination with the penicillins was advantageous against Streptococcus faecalis, but not uniformly against Streptococcus faecium. The combinations of netilmicin with vancomycin or rifampicin were no more effective than the single drugs in most cases, although the response varied for the different strains of the two species.