Martin Guski

Psychoacoustic analysis of noise and the application of earplugs in an ICU: A randomised controlled clinical trial.

BACKGROUND Patients and medical staff are exposed to high noise levels in ICUs, which may have a negative impact on their health. Due to the diversity of noise sources present, including the operating noise of medical devices, staff conversations and the unwrapping of disposables, noise profiles are varied. Psychoacoustics deals with the analysis of sound, focusing on its effects on physiological perception and stress. OBJECTIVES The aim of our study was to examine and to classify noise and its psychoacoustic properties in different locations in our ICU at different times. The impact of noise on subjective parameters and stress-related physiological data was also assessed with and without interventional methods. DESIGN A randomised, controlled, single-blinded clinical trial. SETTING University Hospital, from November 2010 to May 2011. PATIENTS One hundred and forty-four patients in the ICU. INTERVENTIONS In the first part, multidisciplinary psychoacoustic measurement was performed on the patients in our ICU. In the subsequent clinical trial, patients were equipped with effective earplugs, less effective earplugs and no earplugs. Thereafter, active noise cancellation headphones with or without sound masking were employed on a third patient population. MAIN OUTCOME MEASURES Cortisol and &agr;-amylase in saliva, skin conductance measures, vital signs, psychoacoustic analyses and two standardised questionnaires [State-Trait Anxiety Inventory (STAI) and Hospital Anxiety and Depression Scale (HADS)] were assessed. RESULTS In the first part, the mean ± standard deviation (SD) subjective loudness was 9.2 ± 4.0 sone. Although absolute sound pressure level and loudness were lower during the night, the number of loud events increased significantly. Skin conductance in the earplug groups was significantly reduced in comparison to that in the control population but not the active noise reduction groups. Nevertheless, noise reduction was found to be comfortable for most patients. CONCLUSION Noise in the ICU is of high clinical relevance. Diverse noise reduction methods, such as earplugs and active noise cancellation, are available. The avoidance of unnecessary noise, however, should be the primary focus. TRIAL REGISTRATION German Clinical Trials Register (DRKS00000534).

Intensity based multi-scale blending for panoramic images in fluorescence endoscopy

Panoramic images providing a larger local overview of the internal urinary bladder wall can be used for documentation and surgery planning, as well as assist the re-identification of multi-focal tumors during a cystoscopy. In contrast to white light illumination, the photodynamic diagnosis (PDD) leads to an enhanced tissue contrast, resulting in a reddish fluorescence of malignant tissue excited by a bluish small-band illumination. Due to the low illumination power, the fluorescence intensity and the contrast of vasculature are heavily dependent on the distance between the endoscope and the bladder wall. Thus, images with varying illumination and different resolved structures are combined during the iterative panorama composition. In this case, common linear blending methods applied by mosaicking algorithm for endoscopic images, generate strong visual interpolation artifacts in the output image. Instead, the developed intensity based multi-scale blending method, tailored to fluorescence endoscope images, provides a better visual panoramic image quality. Based on a highest intensity decision, a non-linear weighting function is applied on several sub-bands of a Laplacian pyramid image representation. Thus, bright fluorescence information and small vessel texture are preserved in the image composition at the same time. Besides an image quality improvement, the blending algorithm permits a more comfortable and unrestricted endoscope movement for the physician during the bladder scan.

A non-linear multi-scale blending algorithm for fluorescence bladder images

The composition of panoramic images of the internal urinary bladder wall from single endoscope images can strongly support the off-line documentation and surgery planning for cancer treatment, as well as assist the re-identification of multi-focal tumors during a cystoscopy. Unlike white light endoscopy, fluorescence techniques such as photodynamic diagnostics (PDD) lower the risk of missing flat and small tumors due to an enhanced tissue contrast. As a result of the low illumination power and the free hand movement of the endoscope, PDD video sequences usually show strong variations in illumination and resolution. During the subsequent mosaicking and blending process, these effects impede the preservation of original and unbiased input image information in the composed panoramic overview image, and make it difficult to avoid visual interpolation artifacts. Thus, a non-linear intensity based multi-scale blending method for fluorescence images is developed. Based on a highest intensity decision, a region mask modeling the endoscopic illumination characteristic is used to weight the input images on several sub-bands of a Laplacian pyramid. In comparison to basic linear interpolation and standard multi-scale methods the new method preserves high fluorescence intensities as well as fine vessel structures in the final image composition. Furthermore the adaptive characteristics of the blending algorithm allow the physician to move the endoscope more freely along the bladder wall during the image mosaicking process.