ABSTRACT
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 η2â¯<â¯20% and 20%â¯<â¯Î·2â¯<â¯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 η2â¯>â¯20%. FBN was also less influenced by the acquisition and reconstruction setup:with FBN 37 RMs had η2â¯<â¯40%, only 20 with FBS. Most RMs showed a good discriminatory power among heterogeneous PET signals (for FBN: 29 out of 39 RMs with dâ¯>â¯3). CONCLUSIONS: For RMs analysis, FBN should be preferred. A group of 21 RMs was suggested for PET radiomics analysis.
Subject(s)
Image Processing, Computer-Assisted/instrumentation , Pattern Recognition, Automated , Phantoms, Imaging , Positron-Emission Tomography , SoftwareABSTRACT
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.
Subject(s)
Head and Neck Neoplasms/radiotherapy , Radiation Dosage , Radiotherapy Planning, Computer-Assisted , Radiotherapy, Intensity-Modulated , Tomography, X-Ray Computed , Algorithms , Head , Humans , Neck , Radiometry , SoftwareABSTRACT
Vulvar and vaginal atrophy (VVA), is a chronic medical condition experienced by postmenopausal women, with prevalence estimated ranging from 10% to 50% [1]. VVA is characterized by a constellation of symptoms, that may affect daily activities, sexuality, relationships, and quality of life [3]. Early recognition and effective treatment of VVA may enhance sexual health and the quality of life of women and their partners. Some vulvar conditions such as lichen sclerosus are more prevalent in the postmenopausal years. Lichen sclerosus has been suggested as a precursor of Vulvar squamous cell carcinoma. The vulvar exam in post-menopausal women plays an essential role in prevention of cancer because it allows to identify women who should undergo vulvar skin biopsy in order to early detect pre-neoplastic lesions for early diagnosis of cancer of the vulva.
ABSTRACT
A round-robin exercise was conducted within the CALEIDOS LIFE project. The participants were invited to assess the hazard posed by a substance, applying in silico methods and read-across approaches. The exercise was based on three endpoints: mutagenicity, bioconcentration factor and fish acute toxicity. Nine chemicals were assigned for each endpoint and the participants were invited to complete a specific questionnaire communicating their conclusions. The interesting aspect of this exercise is the justification behind the answers more than the final prediction in itself. Which tools were used? How did the approach selected affect the final answer?
Subject(s)
Hazardous Substances/toxicity , Risk Assessment/methods , Animals , Computer Simulation , Fishes , Humans , Mutagenicity Tests , Quantitative Structure-Activity Relationship , Reproducibility of Results , Software , Surveys and Questionnaires , Toxicity Tests, Acute , UncertaintyABSTRACT
Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumour, with very poor prognosis. The high recurrence rate and failure of conventional treatments are expected to be related to the presence of radio-resistant cancer stem cells (CSCs) inside the tumour mass. CSCs can both self-renew and differentiate into the heterogeneous lineages of cancer cells. Recent evidence showed a higher effectiveness of C-ions and protons in inactivating CSCs, suggesting a potential advantage of Hadrontherapy compared with conventional radiotherapy for GBM treatment. To investigate the mechanisms involved in the molecular and cellular responses of CSCs to ionising radiations, two GBM stem cell (GSC) lines, named lines 1 and 83, which were derived from patients with different clinical outcomes and having different metabolic profiles (as shown by NMR spectroscopy), were irradiated with (137)Cs photons and with protons or C-ions of 62 MeV u(-1) in the dose range of 5-40 Gy. The biological effects investigated were: cell death, cell cycle progression, and DNA damage induction and repair. Preliminary results show a different response to ionising radiation between the two GSC lines for the different end points investigated. Further experiments are in progress to consolidate the data and to get more insights on the influence of radiation quality.
Subject(s)
Brain Neoplasms/radiotherapy , Carbon/therapeutic use , Cesium Radioisotopes/therapeutic use , Glioblastoma/radiotherapy , Neoplastic Stem Cells/radiation effects , Proton Therapy , Radiation, Ionizing , Apoptosis/radiation effects , Brain Neoplasms/metabolism , Brain Neoplasms/mortality , Brain Neoplasms/pathology , Cell Cycle/radiation effects , DNA Damage/radiation effects , Glioblastoma/metabolism , Glioblastoma/mortality , Glioblastoma/pathology , Histones/metabolism , Humans , Magnetic Resonance Spectroscopy , Neoplastic Stem Cells/metabolism , Neoplastic Stem Cells/pathology , Prognosis , Radiobiology , Survival Rate , Tumor Cells, CulturedABSTRACT
The spatial distribution of radiation-induced DNA breaks within the cell nucleus depends on radiation quality in terms of energy deposition pattern. It is generally assumed that the higher the radiation linear energy transfer (LET), the greater the DNA damage complexity. Using a combined experimental and theoretical approach, we examined the phosphorylation-dephosphorylation kinetics of radiation-induced γ-H2AX foci, size distribution and 3D focus morphology, and the relationship between DNA damage and cellular end points (i.e., cell killing and lethal mutations) after exposure to gamma rays, protons, carbon ions and alpha particles. Our results showed that the maximum number of foci are reached 30 min postirradiation for all radiation types. However, the number of foci after 0.5 Gy of each radiation type was different with gamma rays, protons, carbon ions and alpha particles inducing 12.64 ± 0.25, 10.11 ± 0.40, 8.84 ± 0.56 and 4.80 ± 0.35 foci, respectively, which indicated a clear influence of the track structure and fluence on the numbers of foci induced after a dose of 0.5 Gy for each radiation type. The γ-H2AX foci persistence was also dependent on radiation quality, i.e., the higher the LET, the longer the foci persisted in the cell nucleus. The γ-H2AX time course was compared with cell killing and lethal mutation and the results highlighted a correlation between cellular end points and the duration of γ-H2AX foci persistence. A model was developed to evaluate the probability that multiple DSBs reside in the same gamma-ray focus and such probability was found to be negligible for doses lower than 1 Gy. Our model provides evidence that the DSBs inside complex foci, such as those induced by alpha particles, are not processed independently or with the same time constant. The combination of experimental, theoretical and simulation data supports the hypothesis of an interdependent processing of closely associated DSBs, possibly associated with a diminished correct repair capability, which affects cell killing and lethal mutation.
Subject(s)
DNA Breaks, Double-Stranded/radiation effects , DNA Repair/radiation effects , Fibroblasts/radiation effects , Histones/metabolism , Linear Energy Transfer , Cell Death/radiation effects , Cell Line , Dose-Response Relationship, Radiation , Fibroblasts/cytology , Fibroblasts/metabolism , Humans , Kinetics , Mutation/radiation effects , Phosphorylation/radiation effectsABSTRACT
Very little is known about the influence of environmental radiation on living matter. In principle, important information can be acquired by analysing possible differences between parallel biological systems, one in a reference-radiation environment (RRE) and the other in a low-radiation environment (LRE). We took advantage of the unique opportunity represented by the cell culture facilities at the Gran Sasso National Laboratories of the Istituto Nazionale di Fisica Nucleare, where environment dose rate reduction factors in the underground (LRE), with respect to the external laboratory (RRE), are as follows: 10(3) for neutrons, 10(7) for directly ionizing cosmic rays and 10 for total γ-rays. Chinese hamster V79 cells were cultured for 10 months in both RRE and LRE. At the end of this period, all the cultures were kept in RRE for another 6 months. Changes in the activities of antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX) and spontaneous mutation frequency at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus were investigated. The results obtained suggest that environmental radiation might act as a trigger of defence mechanisms in V79 cells, specifically those in reference conditions, showing a higher degree of defence against endogenous damage as compared to cells grown in a very low-radiation environment. Our findings corroborate the hypothesis that environmental radiation contributes to the development of defence mechanisms in today living organisms/systems.
Subject(s)
Environment , Fibroblasts/radiation effects , Animals , Antioxidants/metabolism , Cell Line , Cricetulus , Dose-Response Relationship, Radiation , Fibroblasts/enzymology , Fibroblasts/metabolism , Gene Expression Regulation/radiation effects , RadiometryABSTRACT
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
Subject(s)
Head and Neck Neoplasms/radiotherapy , Image Interpretation, Computer-Assisted/methods , Parotid Gland/radiation effects , Radiotherapy Planning, Computer-Assisted/methods , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Radiation Dosage , Radiotherapy, Intensity-ModulatedABSTRACT
The pectoralis major myocutaneous flap (PMMF) is a safe and versatile flap used widely for head and neck cancer reconstructions, but one of the major and most feared complications is oro- or pharyngocutaneous fistula. Herein, we attempt to establish risk factors for fistula formation in reconstructions of mucosal defects in the head and neck using PMMF through retrospective analysis of PMMF performed during 3 years at a single institution, with a total of 84 procedures. There were 69 men and 15 women, with a mean age of 59.5 years. There were 15 cases of partial flap loss, two total flap losses and 31 fistulas. The independent risk factors for fistula formation were preoperative serum hemoglobin < 13 g/dl, preoperative serum albumin < 3.4 g/dl and hypopharynx reconstruction. The PMMF is still a very useful flap and this is the first multivariate analysis analysing risk factors for fistula formation. These findings are helpful in selecting patients with elevated risk of fistula formation, and therefore preventive measures can be undertaken to avoid potentially serious complications.
Subject(s)
Cutaneous Fistula/epidemiology , Fistula/epidemiology , Head and Neck Neoplasms/surgery , Myocutaneous Flap , Oral Fistula/epidemiology , Pharyngeal Diseases/epidemiology , Plastic Surgery Procedures/methods , Postoperative Complications/epidemiology , Aged , Female , Humans , Male , Middle Aged , Pectoralis Muscles/transplantation , Retrospective Studies , Risk FactorsABSTRACT
Adaptive response (AR) is a term that has been generally accepted to describe the ability of a low 'priming' radiation dose to decrease the cell response to a subsequent higher 'challenging' dose. The main proposed mechanisms to explain AR are: increased efficiency of DNA repair and induction of antioxidant enzymes. A model that considers a modulation of the efficiency of DNA repair activity and of the level of antioxidant enzymes, starting from the framework of a lethal-potentially lethal (LPL) model is proposed. The LPL model has been extended with the inclusion of the dynamic variables representing the efficiency of repair, the levels of radiation induced radicals and of antioxidant enzymes. The model used here is able to describe the protective effect of a priming dose. Moreover, in agreement with the data in the literature, the simulations show that the AR happens in given priming dose and priming dose-rate ranges only, and requires at least 4 h to develop. In order to get more insights into the role of cell-cell communication as factors affecting the AR, experimental studies were planned using sparse or confluent AG1522 cell monolayer. The results obtained after gamma irradiation suggest that cell density is a crucial factor for observing an AR.
Subject(s)
Adaptation, Physiological/radiation effects , DNA Damage/physiology , Fibroblasts/physiology , Fibroblasts/radiation effects , Linear Energy Transfer/physiology , Models, Biological , Radiation Tolerance/physiology , Adaptation, Physiological/physiology , Animals , Cell Line , Computer Simulation , Dose-Response Relationship, Radiation , Humans , Radiation DosageABSTRACT
The importance of research to reduce uncertainties in risk assessment of low and protracted exposures is now recognised globally. In Europe a new initiative, called 'Multidisciplinary European LOw Dose Initiative' (MELODI), has been proposed by a 'European High Level and Expert Group on low-dose risk research' (www.hleg.de), aimed at integrating national and EC (Euratom) efforts. Five national organisations: BfS (DE), CEA (FR), IRSN (FR), ISS (IT) and STUK (FI), with the support of the EC, have initiated the creation of MELODI by signing a letter of intent. In the forthcoming years, MELODI will integrate in a step-by-step approach EU institutions with significant programmes in the field and will be open to other scientific organisations and stakeholders. A key role of MELODI is to develop and maintain over time a strategic research agenda (SRA) and a road map of scientific priorities within a multidisciplinary approach, and to transfer the results for the radiation protection system. Under the coordination of STUK a network has been proposed in the 2009 Euratom Programme, called DoReMi (Low-Dose Research towards Mutidisciplinary Integration), which can help the integration process within the MELODI platform. DoReMi and the First MELODI Open Workshop, organised by BfS in September 2009, are now important inputs for the European SRA.
Subject(s)
Government Programs/organization & administration , Radiation Protection/methods , Research Design/trends , Risk Assessment/methods , Europe , Interdisciplinary Studies , Radiation DosageABSTRACT
The PARTRAC code has been developed constantly in the last several years. It is a Monte Carlo code based on an event-by-event description of the interactions taking place between the ionising radiation and liquid water, and in the present version simulates the transport of photons, electrons, protons, helium and heavier ions. This is combined with an atom-by-atom representation of the biological target, i.e. the DNA target model of a diploid human fibroblast in its interphase (genome of 6 Gigabase pairs). DNA damage is produced by the events of energy depositions, either directly, if they occur in the volume occupied by the sugar-phosphate backbone, or indirectly, if this volume is reached by radiation-induced radicals. This requires the determination of the probabilities of occurrence of DNA damage. Experimental data are essential for this determination. However, after the adjustment of the relevant parameters through the comparison of the simulation data with the DNA fragmentation induced by photon irradiation, the code has been used without further parameter adjustments, and the comparison with the fragmentation induced by charged particle beams has validated the code. In this paper, the results obtained for the DNA fragmentation induced by gamma rays and by charged particle beams of various LET are shown, with a particular attention to the production of very small fragments that are not detected in experiments.
Subject(s)
DNA Damage/physiology , DNA/chemistry , DNA/radiation effects , Models, Chemical , Models, Genetic , Models, Statistical , Monte Carlo Method , Algorithms , Computer Simulation , DNA/genetics , Dose-Response Relationship, Radiation , Radiation DosageABSTRACT
We simulated the irradiation of human fibroblasts with gamma rays, protons and helium, carbon and iron ions at a fixed dose of 5 Gy. The simulations were performed with the biophysical Monte Carlo code PARTRAC. From the output of the code, containing in particular the genomic positions of the radiation-induced DNA double-strand breaks (DSBs), we obtained the DNA fragmentation spectra. Very small fragments, in particular those related to "complex lesions" (few tens of base pairs), are probably very important for the late cellular consequences, but their detection is not possible with the common experimental techniques. We paid special attention to the differences among the various ions in the production of these very small fragments; in particular, we compared the fragmentation spectra for ions of the same specific energy and for ions of the same LET (linear energy transfer). As found previously for iron ions, we found that the RBE (relative biological effectiveness) for DSB production was considerably higher than 1 for all high-LET radiations considered. This is at variance with the results obtainable from experimental data, and it is due to the ability to count the contribution of small fragments. It should be noted that for a given LET this RBE decreases with increasing ion charge, due mainly to the increasing mean energy of secondary electrons. A precise quantification of the DNA initial damage can be of great importance for both radiation protection, particularly in open-space long-term manned missions, and hadrontherapy.
Subject(s)
DNA Breaks, Double-Stranded/radiation effects , DNA Fragmentation/radiation effects , Monte Carlo Method , Fibroblasts/metabolism , Fibroblasts/radiation effects , Humans , Linear Energy Transfer , Quality Control , Radiation, IonizingABSTRACT
Where allergic investigations are carried out for occupational dermatitis, appropriate tests must be performed but commercially available batteries are not always suitable for the working conditions and for the products handled by patients. During testing, the products being handled must thus be correctly diluted with full knowledge of their composition in order to prevent harmful effects, particularly caustic effects, and to avoid false positives and false negatives.
Subject(s)
Dermatitis, Allergic Contact/diagnosis , Dermatitis, Occupational/diagnosis , Patch Tests/methods , Allergens , Dermatitis, Allergic Contact/etiology , Dermatitis, Occupational/etiology , HumansABSTRACT
We report on the extraordinary superionic conductivity in the fulleride polymer Li4C60, a crystalline material with no disorder. 7Li, NMR, and dc frequency dependent conductivity show uncorrelated ionic hopping across small energy barriers (DeltaE_{a} approximately 200 meV) and an ionic conductivity of 10;{-2} S/cm at room temperature, higher than in "standard" ionic conductors. Ab initio calculations of the molecular structure find intrinsic unoccupied interstitial sites that can be filled by Li+ cations in stoichiometric Li4C60 even at low temperatures. The low energy required for the occupation of these sites allows a sizable Li+ diffusion above 130 K. The results suggest novel application of lithium intercalated fullerides as electrodes in Li ions batteries.
ABSTRACT
We studied the DNA fragmentation induced in human fibroblasts by iron-ion beams of two different energies: 115 MeV/nucleon and 414 MeV/nucleon. Experimental data were obtained in the fragment size range 1-5700 kbp; Monte Carlo simulations were performed with the PARTRAC code; data analysis was also performed through the Generalized Broken Stick (GBS) model. The comparison between experimental and simulated data for the number of fragments produced in two different size ranges, 1-23 kbp and 23-5700 kbp, gives a satisfactory agreement for both radiation qualities. The Monte Carlo simulations also allow the counting of fragments outside the experimental range: The number of fragments smaller than 1 kbp is large for both beams, although with a strong difference between the two cases. As a consequence, we can compute different RBEs depending on the size range considered for the fragment counting. The PARTRAC evaluation takes into account fragments of all sizes, while the evaluation from the experimental data considers only the fragments in the range of 1-5700 kbp. When the PARTRAC evaluation is restricted to this range, the agreement between experimental and computed RBE values is again good. When fragments smaller than 1 kbp are also considered, the RBE increases considerably, since gamma rays produce a small number of such fragments. The analysis performed with the GBS model proved to be quite sensitive to showing, with a phenomenological single parameter, variations in double-strand break (DSB) correlation.
Subject(s)
DNA Fragmentation , DNA/radiation effects , Fibroblasts/radiation effects , Ions , Iron , Computer Simulation , DNA Damage , Dose-Response Relationship, Radiation , Humans , Monte Carlo Method , Radiation DosageABSTRACT
Previously we reported that yeast and Chinese hamster V79 cells cultured under reduced levels of background environmental ionizing radiation show enhanced susceptibility to damage caused by acute doses of genotoxic agents. Reduction of environmental radiation dose rate was achieved by setting up an underground laboratory at Laboratori Nazionali del Gran Sasso, central Italy. We now report on the extension of our studies to a human cell line. Human lymphoblastoid TK6 cells were maintained under identical in vitro culture conditions for six continuous months, at different environmental ionizing radiation levels. Compared to "reference" environmental radiation conditions, we found that cells cultured in the underground laboratories were more sensitive to acute exposures to radiation, as measured both at the level of DNA damage and oxidative metabolism. Our results are compatible with the hypothesis that ultra-low dose rate ionizing radiation, i.e. environmental radiation, may act as a conditioning agent in the radiation-induced adaptive response.
Subject(s)
Lymphocytes/radiation effects , Radiation, Ionizing , Antioxidants/metabolism , Background Radiation , Catalase/metabolism , Cell Line , Cell Proliferation/radiation effects , DNA Damage , Dose-Response Relationship, Radiation , Environmental Exposure , Humans , Micronucleus Tests , Radiometry , X-RaysABSTRACT
Experimental data on DNA double strand break (DSB) induction in human fibroblasts (AG1522), following irradiation with several radiation qualities, namely gamma rays, 0.84 MeV protons, 58.9 MeV u(-1) carbon ions, iron ions of 115 MeV u(-1), 414 MeV u(-1), 1 GeV u(-1), and 5 GeV u(-1), are presented. DSB yields were measured by calibrated Pulsed Field Gel Electrophoresis in the DNA fragment size range 0.023-5.7 Mbp. The DSB yields show little LET dependence, in spite of the large variation of the latter among the beams, and are slightly higher than that obtained using gamma rays. The highest yield was found for the 5 GeV u(-1) iron beam, that gave a value 30% higher than the 1 GeV u(-1) iron beam. A phenomenological method is used to parametrise deviation from randomness in fragment size spectra.
Subject(s)
DNA Damage , DNA Fragmentation/radiation effects , DNA/genetics , DNA/radiation effects , Fibroblasts/physiology , Fibroblasts/radiation effects , Cells, Cultured , Dose-Response Relationship, Radiation , Humans , Radiation DosageABSTRACT
A 244Cm alpha-particle irradiator was designed and constructed for radiobiological studies where protracted exposure at a low dose rate of cultured mammalian cells is required. It allows irradiation of a cell monolayer attached to the Mylar bottom of a specially designed Petri dish of 56 mm diameter (approximately 25 cm(2) area). The irradiator is based on a 20-mm-diameter stainless steel chamber containing a 148 kBq 244Cm source. The chamber, flushed with helium gas at a pressure kept slightly above the external pressure, is inserted into a cell incubator where temperature and CO2 concentration are controlled. Spectrometric and dosimetric characterization of the irradiator was carried out by means of an ion-implanted-silicon charged-particle detector, CR39 detectors, and Monte Carlo simulations with the TRIM code. Average LET of particles incident on the cells at the center of the Petri dish was evaluated to be 120 keV microm(-1) at 59 mm from the source, and the average dose rate was 5.69 x 10 Gy s(-1), with +12% and -8% variations at the center and the edge, respectively. The irradiator has been successfully tested and used for several experiments involving 16-d exposure of human fibroblasts monolayers.
Subject(s)
Alpha Particles , Curium , Cells, Cultured , Humans , Radiation DosageABSTRACT
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.