Overranging at multisection CT: an underestimated source of excess radiation exposure.
ABSTRACT To reconstruct the first and last sections of a helical computed tomographic (CT) scan, the scan length is automatically extended beyond the planned image boundaries, a phenomenon known as overranging. With common 16-section CT scanning protocols, the overrange length is between 3 and 6 cm. For scanners with 64 or more sections, this length will be much greater, since overranging increases as pitch or detector collimation increases. Manufacturers have equipped the latest generation of CT scanners (128 sections or more) with overrange dose-reducing innovations that reduce overranging by typically up to 50%, which in the best cases reduces overranging to that of the previous scanner models (64 sections). To reduce the impact of overranging on radiosensitive organs just outside the planned scan region, it is best to use an axial protocol rather than a helical protocol. If this is not an option, lowering the pitch or the detector collimation will significantly reduce overranging. Finally, CT examinations should be planned in such a way that radiosensitive organs are as far as possible from the imaged volume.
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ABSTRACT: Introduction: Computed tomography (CT) dose optimization is an important issue in radiography because CT is the largest contributor to medical radiation dose and its use is increasing. However, CT dose optimization for pediatric patients could be more challenging than their adult counterparts. The purpose of this literature review was to identify and discuss the current pediatric CT dose saving techniques. Optimized pediatric protocols were also proposed. Methods: A comprehensive literature search was conducted using the Medline, ProQuest Health and Medical Complete, PubMed, ScienceDirect, Scopus, Springer Link, and Web of Science databases and the keywords CT, pediatric, optimization, protocol, and radiation dose to identify articles focusing on pediatric CT dose optimization strategies published between 2004 and 2014. Results and Summary: Seventy-seven articles were identified in the literature search. Strategies for optimizing a range of scan parameters and technical considerations including tube voltage and current, iterative reconstruction, diagnostic reference levels, bowtie filters, scout view, pitch, scan collimation and time, overscanning, and overbeaming for pediatric patients with different ages and body sizes and compositions were discussed. An example of optimized pediatric protocols specific to age and body size for the 64-slice CT scanners was devised. It is expected that this example could provide medical radiation technologists, radiologists, and medical physicists with ideas to optimize their pediatric protocols.Journal of Medical Imaging and Radiation Sciences 06/2015; 46(2):241-249. DOI:10.1016/j.jmir.2015.03.003
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ABSTRACT: The European Union has recently implemented its Data Directive on Privacy, a legal measure stating that certain “personal” information (e.g., an individual's race, sexual orientation, or medical records) cannot leave the EU unless it is going to a nation with privacy laws similar to those of the EU Directive. As the United States is not a member of the EU and as it has no official national data privacy legislation paralleling that of the EU, it cannot legally receive any form of “personal” information from any of the EU's 15 member states unless it first receives the consent of the individual. The United States responses with the “Safe Harbor Principles” which shift the burden of meeting EU privacy standards away from the national governments and to individual companies. The Safe Harbor Principles, however, have not been well received by either the EU or the American companies they were designed to help. To date, response to the EU Data Privacy Directive remains mixed, but one thing is certain-it will forever alter the way in which we view and we use the online environmentProfessional Communication Conference, 1999. IPCC 99. Communication Jazz: Improvising the New International Communication Culture. Proceedings. 1999 IEEE International; 02/1999
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ABSTRACT: Organ doses are useful for estimating radiation doses to patients. However, it is impossible to determine specific organ doses for each patient. The aim of this study was to examine the relationship between specific organ doses and volumetric CT dose indices (CTDIvols) in multidetector CT studies to estimate specific organ doses in each patient. Radiophotoluminescent glass dosimeters were placed at locations corresponding to specific organs of an anthropomorphic phantom. Thereafter, the phantoms were examined with respect to various imaging ranges and protocols, including cranial, thoracic and abdominal acquisitions using a 64-section multidetector CT. Concurrently, we recorded the mean CTDIvol for each acquisition range. In the cranial acquisition, the displayed mean CTDIvol was 69.0mGy, and the absorbed doses for brain and intra-ocular lenses were 57.2±2.6 and 57.1±3.0mGy, respectively. In the thoracic acquisition, the displayed mean CTDIvol was 16.3mGy, and the absorbed doses for breast and lung were 19.1±6.4 and 31.7±2.2mGy, respectively. In the abdominal acquisition, the displayed mean CTDIvol was 21.6mGy, and the absorbed doses for stomach and colon were 28.2±6.1 and 28.0±8.6mGy, respectively. The displayed mean CTDIvols overestimated the specific organ doses in the cranial acquisition and underestimated them in the thoracic and abdominal acquisitions. However, the approximate specific organ doses may be estimated by multiplying the displayed mean CTDIvols with a conversion factor for each organ.Journal of Medical Imaging and Radiation Oncology 10/2011; 55(5):493-7. DOI:10.1111/j.1754-9485.2011.02293.x · 0.95 Impact Factor