Radiation dose and image information in computed radiography. A phantom study of angle measurements in the weight-bearing knee

Purpose: To establish a correlation between radiation dose and diagnostic accuracy when employing a new digital method for angle determinations. The specific intention was to determine how far the radiation dose can be reduced without losing measuring accuracy and to compare this radiation dose with that employed with our conventional method.Material and Methods: An image succession of an anthropomorphic phantom was generated with a computed radiography (CR) system, by reducing the exposure stepwise. The images were archived and transferred to a workstation for evaluation. The intraobserver variation of two angle determinations was used as an indicator of the evaluation accuracy. Patient radiation doses were measured with thermoluminescent dosimeters. The energy imparted, indicating the relative risk associated with exposure to ionising radiation, and the effective dose, which determines the absolute risk, were calculated.Results and Conclusion: No significant correlation was found between patient dose and measuring accuracy within the evaluated exposure interval. At the lowest exposure of the CR system, the energy imparted to the patient was 30 μJ. Compared with our conventional analogue method this is a reduction by 98%. The effective dose was as low as 1.5 μSv. The CR technique creates possibilities to adapt exposure parameters, and thus the radiation dose to the patient, according to the purpose of the investigation.     

ESB clinical biomechanics award 2008: Complete data of total knee replacement loading for level walking and stair climbing measured in vivo with a follow-up of 6–10 months

Background

Detailed information about the loading of the knee joint is required for various investigations in total knee replacement. Up to now, gait analysis plus analytical musculo-skeletal models were used to calculate the forces and moments acting in the knee joint. Currently, all experimental and numerical pre-clinical tests rely on these indirect measurements which have limitations. The validation of these methods requires in vivo data; therefore, the purpose of this study was to provide in vivo loading data of the knee joint.

Methods

A custom-made telemetric tibial tray was used to measure the three forces and three moments acting in the implant. This prosthesis was implanted into two subjects and measurements were obtained for a follow-up of 6 and 10 months, respectively.Subjects performed level walking and going up and down stairs using a self-selected comfortable speed. The subjects’ activities were captured simultaneously with the load data on a digital video tape. Customized software enabled the display of all information in one video sequence.

Findings

The highest mean values of the peak load components from the two subjects were as follows: during level walking the forces were 276 %BW (percent body weight) in axial direction, 21 %BW (medio-lateral), and 29 %BW (antero-posterior). The moments were 1.8 %BW*m in the sagittal plane, 4.3 %BW*m (frontal plane) and 1.0 %BW*m (transversal plane). During stair climbing the axial force increased to 306 %BW, while the shear forces changed only slightly. The sagittal plane moment increased to 2.4 %BW*m, while the frontal and transversal plane moments decreased slightly. Stair descending produced the highest forces of 352 %BW (axial), 35 %BW (medio-lateral), and 36 %BW (antero-posterior). The sagittal and frontal plane moments increased to 2.8 %BW*m and 4.6 %BW*m, respectively, while the transversal plane moment changed only slightly.

Interpretation

Using the data obtained, mechanical simulators can be programmed according to realistic load profiles. Furthermore, musculo-skeletal models can be validated, which until now often lacked the ability to predict properly the non-sagittal load values, e.g. varus–valgus and internal–external moments.     

Revealing mental health status in Iran's capital: putting equity and efficiency together

Information about urban health is often based on averages, while to better understand health status in urban areas, inequality should also be included. In this paper, we applied an achievement index approach in order to surmount this defect and to examine mental health status in Iran's capital, Tehran. The data we required for this study were taken from the Urban Health Equity Assessment and Response Tool (Urban HEART) survey which was conducted in Tehran in 2007, covering people aged 15 and above. The concentration index, which is a commonly used measure of socioeconomic inequalities in health, was extended to enable the combination of inequality and averages and the formation of a mental health achievement index. Values from the standard concentration indices showed that mental disorders are concentrated disproportionately among the poor in Tehran. An extension of the standard concentration indices revealed that, in most of Tehran's districts, the mental health of populations in the poorest quintile is much worse than that of other groups. In addition, when we computed the achievement index and ranked districts according to this index, the ranking was different from the ranking by averages. These findings imply that mental health varies significantly across the economic groups of the population in Tehran and that efficiency-oriented strategies which target average level of mental health alone are not sufficient to improve mental health of all people especially mental health of the poor. Equity-oriented strategies which target the mental health inequalities should be considered as well.     

Scatter fraction: measurement and correction

The concept of scatter in Positron Emission Tomography is reviewed regarding origin and influence on data. Different ways to measure and correct for scatter are discussed.This article was presented at the 1st EEC workshop on accuracy determination in PET, January 19–20th. 1989 Pisa, Italy (COMACBME Concerted Project Characterization and Standardization of PET Instrumentation)     

Mini Uni-Twin托槽系统治疗中重度牙列拥挤患者的临床研究

目的 应用Mini Uni-Twin(MUT)托槽系统矫治中重度牙列拥挤的患者,评价其临床矫治效果.方法 选取安氏1类牙列拥挤的患者60例,拔除4个第一前磨牙,随机分为两组并分别应用MUT托槽系统和传统直丝弓技术进行矫治,对治疗前后的头影测量项目进行统计分析,并记录所有患者的平均疗程以及矫治器戴入后的疼痛程度.结果 30例MUT患者平均疗程17.5±2.8个月,30例传统直丝患者平均疗程21.8±3.2个月,其差异有统计学意义;第一次戴入后24 h以及48hMUT组患者的疼痛明显低于传统直丝弓组;两组间治疗前后头影测量的结果并无明显差异.结论 MUT托槽系统可减轻矫治初期的疼痛,缩短疗程,是一种高效的矫治系统.     

Is it safe for extended-role radiographers to measure migration percentage in children with cerebral palsy?

IntroductionIn the surveillance of children with cerebral palsy, the measurement of migration percentage is used to identify children at risk of hip dislocation. Early identification of children at risk facilitates early intervention with less invasive surgical procedures to prevent further deterioration.The aim of this study is to evaluate the safety of the measurements of migration percentage for surveillance in cerebral palsy by extended-role radiographers by evaluating the reliability and validity of measurements performed by these professionals.MethodsA sample of thirty pelvic x-rays were selected from the local cerebral palsy database. A range of hip displacement was selected including some challenging borderline x-rays. All ten extended-role radiographers completed measurements using TraumaCAD which were repeated at a minimum of 4 weeks.Inter-rater and intra-rater reliability was calculated using intraclass correlation coefficients. The accuracy and safety of the system was evaluated by converting measurements into referral categories (red, amber or green) and cohen's kappa was calculated when categories were compared to measurements to orthopaedic surgeonResultsThe inter-rater reliability between radiographers was 0.938 (95% CI 0.914–0.991). The intra-rater reliability was 0.941 (95% CI 0.931–0.949).The percentage agreement was 94.8% for green, 93.8% for amber and 98.2% for red hips. The weighted kappa value was 0.923 (95% CI 0.889–0.957).ConclusionThe reliability and accuracy of radiographer measurement of migration percentage is excellent. It is safe for radiographers to calculate the migration percentage using semi-automated software for the surveillance of children with cerebral palsy.Implications for practiceWe recommend the measurement of migration percentage may be performed by extended-role radiographers to deliver accurate and reliable measurements for use in cerebral palsy surveillance.     

Patient shielding during dentomaxillofacial radiography: Recommendations from the American Academy of Oral and Maxillofacial Radiology

BackgroundThe American Academy of Oral and Maxillofacial Radiology established an ad hoc committee to draft evidence-based recommendations and clinical guidance for the application of patient contact shielding during dentomaxillofacial imaging.Types of Studies ReviewedThe committee reviewed monographs and reports from radiation protection organizations and studies that reported radiation dose to gonads, breasts, and thyroid gland from dentomaxillofacial imaging.ResultsConsidering the absence of radiation-induced heritable effects in humans and the negligible dose to the gonads and fetus from dentomaxillofacial imaging, the committee recommends discontinuing shielding of the gonads, pelvic structures, and fetuses during all dentomaxillofacial radiographic imaging procedures. On the basis of radiation doses from contemporaneous maxillofacial imaging, the committee considered that the risks from thyroid cancer are negligible and recommends that thyroid shielding not be used during intraoral, panoramic, cephalometric, and cone-beam computed tomographic imaging.Practical ImplicationsThis position statement informs and educates the reader on evolving radiation protection practices and provides simple, unequivocal guidance to dental personnel to implement these guidelines. State and local authorities should be contacted to update regulations to reflect these recommendations.