The EIVE CubeSat - Developing a Satellite Bus for a 71-76 GHz E-Band Transmitter Payload

A high-speed data downlink system provides many challenges for a CubeSat design. Two major aspect are an adequate power management as well as the thermal implications of the dissipated power. The goal of the 6U CubeSat EIVE is to prove the feasibility of an E-band link at 71-76 GHz and explore the influence of different atmospheric conditions on the link quality. The requirements of the E-band transmitter in terms of mass, volume, power and pointing accuracy outline the specific constraints imposed on the design of the satellite bus. The major design drivers of the system are the peak power demand of 60 W for the payload itself and the required pointing accuracy of less than 1◦. To cope with these demands, general design considerations, the choice of the orbit and the operation of the satellite are discussed. A special focus is the power generation and consumptions by means of a dynamic attitude and power simulation. The thermal simulation is verified by building a detailed structural and thermal replica of the satellite to investigate the heat dissipation. An overview of the current EIVE CubeSat platform design concludes this paper

Aortic aneurysm pulsatile wall motion imaged by cine MRI: A tool to evaluate efficacy of endovascular aneurysm repair?

Objectives: to evaluate cine MRI as a means of determining the two-dimensional pulsatile wall motion (2D-PWM) of abdominal aortic aneurysm (AAA). Design: prospective study of 21 patients with AAA. 2D-PWM was defined as change in cross-sectional area. Results: the median diastolic area was 28cm 2 (intraquartile range, IQR, 22-31 cm2) and the median (IQR) 2D-PWM was 0.25 (0.10-0.40) cm2. Assuming that the AAA is circular in cross-section this represents a median (IQR) diameter increase of 0.3 (0.1-0.4) mm. However, local wall displacements up to 2 mm were present in varying directions, without significant change in surface area. Conclusion: AAA PWM is negligible and may not therefore be a potential tool to assess efficacy of endovascular aneurysm exclusion

MR imaging of healthy knees in varying degrees of flexion using a stretchable coil array provides comparable image quality compared to a standard knee coil array

Objective: Stretchable coils allow knee imaging at varying degrees of flexion. Purpose was to compare a new-developed stretchable 8-channel to a standard 8-channel knee coil array by means of quantitative and qualitative image analysis. Material and methods: IRB approved prospective study. Knee MR imaging in 10 healthy volunteers was performed at 3T using a standard 8-channel and a new-developed stretchable 8-channel coil array at 0°, 45°, and 60° of flexion and at 0° (standard coil). Image parameters were identical. Signal-to-noise ratio (SNR) was determined by combining the images with separately acquired noise data on a pixel-by-pixel basis using MATLAB routines (Natick, MA, USA). Images were qualitatively analysed by two independent radiologists who graded the visibility of several anatomic structures from 1 = not visible to 5 = excellent. ANOVA, Wilcoxon and kappa statistics were used. Results: Mean SNR ± standarddeviation of bone was 54.7 ± 10.4 and of muscle 28.0 ± 4.4 using the stretchable coil array and 54.6 ± 8.2 and 33.4 ± 4.5, respectively, using the standard knee coil array. No statistically significant SNR differences were found between both arrays (bone, p = 0.960; muscle, p = 0.132). SNR was not degraded at higher degrees of flexion. The qualitative image analysis did not reveal statistically significant differences between the stretchable and standard coil array with regard to the visibility of anatomic structures (p = 0.026–1.000). Overall kappa was 0.714. Conclusion: Stretchable 8-channel coil arrays provide similar SNR and visibility of anatomic structures compared to standard 8-channel knee coil arrays. MR imaging with high SNR will now be possible in flexed knees

Efficacy of MRI and mammography for breast-cancer screening in women with a familial or genetic predisposition.

Contains fulltext : 58587.pdf (publisher's version ) (Open Access)BACKGROUND: The value of regular surveillance for breast cancer in women with a genetic or familial predisposition to breast cancer is currently unproven. We compared the efficacy of magnetic resonance imaging (MRI) with that of mammography for screening in this group of high-risk women. METHODS: Women who had a cumulative lifetime risk of breast cancer of 15 percent or more were screened every six months with a clinical breast examination and once a year by mammography and MRI, with independent readings. The characteristics of the cancers that were detected were compared with the characteristics of those in two different age-matched control groups. RESULTS: We screened 1909 eligible women, including 358 carriers of germ-line mutations. Within a median follow-up period of 2.9 years, 51 tumors (44 invasive cancers, 6 ductal carcinomas in situ, and 1 lymphoma) and 1 lobular carcinoma in situ were detected. The sensitivity of clinical breast examination, mammography, and MRI for detecting invasive breast cancer was 17.9 percent, 33.3 percent, and 79.5 percent, respectively, and the specificity was 98.1 percent, 95.0 percent, and 89.8 percent, respectively. The overall discriminating capacity of MRI was significantly better than that of mammography (P<0.05). The proportion of invasive tumors that were 10 mm or less in diameter was significantly greater in our surveillance group (43.2 percent) than in either control group (14.0 percent [P<0.001] and 12.5 percent [P=0.04], respectively). The combined incidence of positive axillary nodes and micrometastases in invasive cancers in our study was 21.4 percent, as compared with 52.4 percent (P<0.001) and 56.4 percent (P=0.001) in the two control groups. CONCLUSIONS: MRI appears to be more sensitive than mammography in detecting tumors in women with an inherited susceptibility to breast cancer

Differences between first and subsequent rounds of the MRISC breast cancer screening program for women with a familial or genetic predisposition

BACKGROUND. within the Dutch MRI Screening (MRISC) study, a Dutch multicenter screening study for hereditary breast cancer, the authors investigated whether previously reported increased diagnostic accuracy of magnetic resonance imaging (MRI) compared with mammography would be maintained during subsequent screening rounds. METHODS. From November 1999 to October 2003,1909 eligible women were included in the study. Screening parameters and tumor characteristics of different rounds were calculated and compared. The authors defined 3 different types of imaging screening rounds: first round in women never screened by imaging before, first round in women screened by imaging (mainly mammography) before, and subsequent rounds. RESULTS. The difference in sensitivity for invasive cancers between mammography and MRI was largest in the first round of women previously screened with mammography (20.0 vs. 93.3%; P =.003), but also in subsequent rounds, there was a significant difference in favor of MRI (29.4 vs. 76.5%; P =.02). The difference in false-positive rate between mammography and MRI was also largest in the first round of women previously screened with mammography (5.5 vs. 14.0%; P CONCLUSIONS. in subsequent rounds, a significantly higher sensitivity and better discriminating capacity of MRI compared with mammography was maintained, and a favorable tumor stage compared with age-matched symptomatic controls. As results of these subsequent screening rounds were most predictive for long-term effects, the authors expect that this screening program will contribute to a decrease of breast cancer mortality in these high-risk women

The reliability of plain radiography in experimental fracture healing

To investigate the reliability of radiographs in the evaluation of healing of closed fractures. A closed midshaft tibial fracture was created in 40 goats and stabilized with an external fixator. The animals were assigned to four groups: no injection, injection of 1 mg osteogenic protein-1 (OP-1), 1 mg OP-1 with collagenous carrier, or carrier alone. Radiographs were performed weekly until the animals were killed after 2 and 4 weeks. Healing was evaluated using radiographs, biomechanical testing, and histological examination. All radiographs were examined by two independent observers. Interobserver agreement was calculated and radiographic scores were compared with mechanical and histological scores using regression analysis. Regression analysis showed poor correlation between radiographic scores and biomechanical and histological data. Correlation coefficients varied between 0.39 and 0.63. Good agreement between the observers was seen in only three parameters: visibility of the fracture line, weightbearing ability, and a combined healing parameter. Plain radiography provides poor parameters for monitoring the fracture healing proces