Pressure distribution analysis of X-Ray table mattresses.

BACKGROUND: There is a risk of developing pressure ulcers from lying on an X-ray table mattress, if the mattress pressure redistribution properties are poor. AIM: To assess the pressure redistribution properties of 'new' and 'in current clinical use' X-ray table mattresses. METHODS AND MATERIALS: Twenty one X-ray table mattresses, each of 2.5 cm thickness, were evaluated. An anthropomorphic human phantom of adult stature with five different weights (minimum, first quartile, mean, third quartile and maximum) was used to simulate human head, pelvis and heels (pressure ulcer jeopardy areas). Using Xsensor technology, peak pressure was measured and Interface Pressure Ratio was calculated for the three pressure ulcer jeopardy areas 'with' and 'without' an X-ray table mattress. RESULTS: For all mattresses, statistically significant differences (p < 0.05) were found between the peak pressure values with and without using an X-ray table mattress for the three pressure ulcer jeopardy areas; similarly, for all mattresses, statistically significant differences (p < 0.05) were found between the Interface Pressure Ratio values with and without using x-ray table mattress. The type and age of the mattress was observed to have an impact on peak pressure values and Interface Pressure Ratios, with older mattresses performing worse. CONCLUSION: Peak pressure values and Interface Pressure Ratios are reduced significantly when using newer X-ray table mattresses. This could be because newer mattresses use more appropriate materials in their construction and/or older mattresses have lost their pressure redistribution properties. Radiology departments should consider assessing mattresses pressure redistribution properties, perhaps on an annual basis.

A Phantom-Based Method to Assess X-Ray Table Mattress Interface Pressures.

BACKGROUND: Pressure redistribution performance of x-ray table mattresses can influence the development of pressure ulcers in at-risk populations. Interface pressure analysis, with human participants, is a common method to assess mattresses. This approach has limitations that relate to the lack of standardisation between and within humans. AIM: This study aimed to develop and validate an anthropomorphic phantom-based method to assess x-ray table mattress interface pressures as an index of mattress performance. METHODS: A three dimensional phantom simulating an adult's head, pelvis, and heels was printed from x-ray computed tomography image data and attached to a metal frame 175 cm in length. Dry sand was added to the phantom head, pelvis, and heels to represent a range of human weights. Pressure distribution was assessed using XSensor. Phantom validation was achieved by comparing phantom mattress interface pressure characteristics, for five human equivalent weights, against 27 sets of human mattress interface pressure data. RESULTS: Using the correlation coefficient R, phantom and human pressure data showed good correlation for the five phantom weights (R values: head = 0.993, pelvis = 0.997, and heels = 0.996). CONCLUSION: A novel method to test x-ray mattresses for interface pressure was developed and validated. The method could have utility in the testing of x-ray mattresses that are in routine use and for new mattress development. Phantom interface pressure data could be provided by manufacturers to help inform procurement decisions when matching mattress characteristics to medical imaging demands and the underlying patient populations.

Implication of Free Fatty Acids in Thrombin Generation and Fibrinolysis in Vascular Inflammation in Zucker Rats and Evolution with Aging.

Background: The metabolic syndrome (MetS) and aging are associated with modifications in blood coagulation factors, vascular inflammation, and increased risk of thrombosis. Objectives: Our aim was to determine concomitant changes in thrombin generation in the blood compartment and at the surface of vascular smooth muscle cells (VSMCs) and its interplay with adipokines, free fatty acids (FFA), and metalloproteinases (MMPs) in obese Zucker rats that share features of the human MetS. Methods: Obese and age-matched lean Zucker rats were compared at 25 and 80 weeks of age. Thrombin generation was assessed by calibrated automated thrombography (CAT). Results: Endogenous thrombin potential (ETP) was increased in obese rats independent of platelets and age. Clot half-lysis time was delayed with obesity and age. Interleukin (IL)-1ß and IL-13 were increased with obesity and age respectively. Addition of exogenous fibrinogen, leptin, linoleic, or palmitic acid increased thrombin generation in plasma whereas adiponectin had an opposite effect. ETP was increased at the surface of VSMCs from obese rats and addition of exogenous palmitic acid further enhanced ETP values. Gelatinase activity was increased in aorta at both ages in obese rats and MMP-2 activity was increased in VSMCs from obese rats. Conclusions: Our study demonstrated in MetS an early prothrombotic phenotype of the blood compartment reinforced by procoagulant properties of dedifferentiated and inflammatory VSMCs. Mechanisms involved (1) increased fibrinogen and impaired fibrinolysis and (2) increased saturated fatty acids responsible for additive procoagulant effects. Whether specifically targeting this hypercoagulability using direct thrombin inhibitors would improve outcome in MetS is worth investigating.

Mathematical modelling of radiation-induced cancer risk from breast screening by mammography.

OBJECTIVES: Establish a method to determine and convey lifetime radiation risk from FFDM screening. METHODS: Radiation risk from screening mammography was quantified using effective risk (number of radiation-induced cancer cases/million). For effective risk calculations, organ doses and examined breast MGD were used. Screening mammography was simulated by exposing a breast phantom for cranio-caudal and medio-lateral oblique for each breast using 16 FFDM machines. An ATOM phantom loaded with TLD dosimeters was positioned in contact with the breast phantom to simulate the client's body. Effective risk data were analysed using SPSS software to establish a regression model to predict the effective risk of any screening programme. Graphs were generated to extrapolate the effective risk of all screening programmes for a range of commencement ages and time intervals between screens. RESULTS: The most important parameters controlling clients' total effective risk within breast screening are the screening commencement age and number of screens (correlation coefficients were -0.865 and 0.714, respectively). Since the tissue radio-sensitivity reduces with age, the end age of screening does not result in noteworthy effect on total effective risk. CONCLUSIONS: The regression model can be used to predict the total effective risk for clients within breast screening but it cannot be used for exact assessment of total effective risk. Graphical representation of risk could be an easy way to represent risk in a fashion which might be helpful to clients and clinicians.

Morphological Characterisation of Unstained and Intact Tissue Micro-architecture by X-ray Computed Micro- and Nano-Tomography.

Characterisation and quantification of tissue structures is limited by sectioning-induced artefacts and by the difficulties of visualising and segmenting 3D volumes. Here we demonstrate that, even in the absence of X-ray contrast agents, X-ray computed microtomography (microCT) and nanotomography (nanoCT) can circumvent these problems by rapidly resolving compositionally discrete 3D tissue regions (such as the collagen-rich adventitia and elastin-rich lamellae in intact rat arteries) which in turn can be segmented due to their different X-ray opacities and morphologies. We then establish, using X-ray tomograms of both unpressurised and pressurised arteries that intra-luminal pressure not only increases lumen cross-sectional area and straightens medial elastic lamellae but also induces profound remodelling of the adventitial layer. Finally we apply microCT to another human organ (skin) to visualise the cell-rich epidermis and extracellular matrix-rich dermis and to show that conventional histological and immunohistochemical staining protocols are compatible with prior X-ray exposure. As a consequence we suggest that microCT could be combined with optical microscopy to characterise the 3D structure and composition of archival paraffin embedded biological materials and of mechanically stressed dynamic tissues such as the heart, lungs and tendons.

Brachial artery modifications to blood flow-restricted handgrip training and detraining.

Low load resistance training with blood flow restriction (BFR) can increase muscle size and strength, but the implications on the conduit artery are uncertain. We examined the effects of low-load dynamic handgrip training with and without BFR, and detraining, on measures of brachial artery function and structure. Nine male participants (26 ± 4 yr, 178 ± 3 cm, 78 ± 10 kg) completed 4 wk (3 days/wk) of dynamic handgrip training at 40% 1 repetition maximum (1RM). In a counterbalanced manner, one forearm trained under BFR (occlusion cuff at 80 mmHg) and the other under nonrestricted (CON) conditions. Brachial artery function [flow-mediated dilation (FMD)] and structure (diameter) were assessed using Doppler ultrasound. Measurements were made before training (pretraining), after training (posttraining), and after 2-wk no training (detraining). Brachial artery diameter at rest, in response to 5-min ischemia (peak diameter), and ischemic exercise (maximal diameter) increased by 3.0%, 2.4%, and 3.1%, respectively, after BFR training but not after CON. FMD did not change at any time point in either arm. Vascular measures in the BFR arm returned to baseline after 2 wk detraining with no change after CON. The data demonstrate that dynamic low-load handgrip training with BFR induced transient adaptations to conduit artery structure but not function.