Healthcare-associated infection among residents of long-term care facilities: a cohort and nested case–control study

Knowledge of infection control measures in nursing homes is limited. This study aimed to assess the incidence of, and potential risk factors for, healthcare-associated infection in long-term care facilities in Norway. Incidence of healthcare-associated infection was recorded prospectively in six long-term care facilities located in two major cities in Norway between 1 October 2004 and 31 March 2005. For each resident with an infection we aimed for two controls in a nested case–control study to identify potential risk factors. Incidence of infection was 5.2 per 1000 resident-days. Urinary and lower respiratory tract infections were the most common. Patients confined to their beds [odds ratio (OR = 2.7)], who stayed <28 days (OR = 1.5), had chronic heart disease (OR = 1.3), urinary incontinence (OR = 1.5), an indwelling urinary catheter (OR = 2.0) or skin ulcers (OR = 1.8) were shown to have a greater risk for infection. Age, sex and accommodated in a two- versus single-bed room were not significant factors. Incidence of infection in nursing homes in Norway is within the range reported from other countries. This study identified several important risk factors for healthcare-associated infection. There is a need to prevent infection by implementing infection control programmes including surveillance in long-term care facilities

The impact of CBCT reconstruction and calibration for radiotherapy planning in the head and neck region – a phantom study

<div><p></p><p><b>Background.</b> The applicability of cone-beam computed tomography (CBCT) image sets for dose calculation purposes relies on high image quality and CT number accuracy. In this study we have investigated the use of stoichiometric calibration for transforming CT numbers into physical parameters, in combination with a new CBCT scatter correction algorithm, focusing on head and neck geometries.</p><p><b>Methods.</b> CBCT projections were acquired using an On-Board-Imager (OBI v1.4; Varian Medical Systems) using both low- and high-dose clinical image acquisition protocols. The CBCT projections were reconstructed twice, using both the standard method (OBI) as well as an experimental pre-clinical reconstruction algorithm (Full Fan Experimental - FFE). Stoichiometric calibration was performed using both a phantom from CIRS with nine tissue equivalent inserts (ranging from lung to dense bone) as well as with a custom made cylindrical PMMA head and neck phantom with variable ‘head’ diameter and with cavities designed to fit the inserts from a Gammex RMI phantom. To benchmark the CBCT performance, the same calibration procedures were performed using two conventional CT scanners. For assessment of influence on dose-volume parameters, the head part of the anthropomorphic Alderson phantom was scanned, reconstructed with both CT and CBCT using the stoichiometric calibration curves, and finally used to compare IMRT dose calculations.</p><p><b>Results.</b> The stoichiometric CBCT calibrations with the CIRS phantom resulted in an excellent fit between calculated and measured CT numbers (R = 1.000 for all combinations tested), equivalent to the results for the conventional scanners. Using the PMMA phantom, the stoichiometric calibration curves again showed excellent agreement, although the OBI reconstruction showed marginally increasing deviation from the unity line as the phantom size decreased. For the dose-volume parameters, deviations well within 1% were seen between the different reconstruction methods and acquisition modes.</p><p><b>Conclusion.</b> This study showed that the combination of an improved reconstruction method and stoichiometric calibration improved the CT number accuracy of CBCT scans acquired for head and neck phantoms. In particular, a radial size dependence of the scanned object similar to that in conventional CT could be achieved. Although high density inhomogeneities still are challenging for the reconstruction process, clinically acceptable agreement in key dose-volume parameters between CT-based and CBCT-based IMRT planning calculations on a humanoid phantom was found.</p></div

Evaluation of an application for intensity-based deformable image registration and dose accumulation in radiotherapy

<div><p></p><p><b>Background.</b> Methods to accurately accumulate doses in radiotherapy (RT) are important for tumour and normal tissues being influenced by geometric uncertainties. The purpose of this study was to investigate a pre-release deformable image registration (DIR)-based dose accumulation application, in the setting of prostate RT.</p><p><b>Material and methods.</b> Initially accumulated bladder and prostate doses were assessed (based on 8–9 repeat CT scans/patient) for nine prostate cancer patients using an intensity-based DIR and dose accumulation algorithm as provided by the Dynamic Adaptive Radiation Therapy (DART) software. The accumulated bladder and prostate dose-volume histograms (DVHs) were compared on a range of parameters (paired Wilcoxon signed-rank test, 5% significance level) to DVHs derived using an in-house developed dose accumulation method based on biomechanical, contour-driven DIR (SurfaceRegistration). Finally, both these accumulated dose distributions were compared to the ‘static’ DVH, assessed from the planning CT.</p><p><b>Results.</b> Over the population, doses accumulated with DART were overall lower than those from SurfaceRegistration (p < 0.05: D_2%, gEUD and NTCP (bladder); D_min (prostate)). The magnitude of these differences peaked for the bladder gEUD with a population median of 47 Gy for DART versus 57 Gy for SurfaceRegistration. Across the ten bladder dose/volume parameters investigated, the most pronounced individual differences were observed between the ‘accumulated’ DVHs and the ‘static’ DVHs, with deviations in mean dose up to 22 Gy.</p><p><b>Conclusion.</b> Substantial and significant differences were observed in the dose distributions between the two investigated DIR-based dose accumulation applications. The most pronounced individual differences were seen for the bladder and relative to the planned dose distribution, encouraging the use of repeat imaging data in RT planning and evaluation for this organ.</p></div