News Column

Studies from Bioengineering Unit Further Understanding of Algorithms

February 7, 2014



By a News Reporter-Staff News Editor at Health & Medicine Week -- Investigators publish new report on Algorithms. According to news originating from Pavia, Italy, by NewsRx correspondents, research stated, "The aim of the study was to evaluate the dosimetric impact of low-Z and high-Z metallic implants on IMRT plans. Computed tomography (CT) scans of three patients were analyzed to study effects due to the presence of Titanium (low-Z), Platinum and Gold (high-Z) inserts."

Our news journalists obtained a quote from the research from Bioengineering Unit, "To eliminate artifacts in CT images, a sinogram-based metal artifact reduction algorithm was applied. IMRT dose calculations were performed on both the uncorrected and corrected images using a commercial planning system (convolution/superposition algorithm) and an in-house Monte Carlo platform. Dose differences between uncorrected and corrected datasets were computed and analyzed using gamma index (P gamma < 1) and setting 2 mm and 2% as distance to agreement and dose difference criteria, respectively. Beam specific depth dose profiles across the metal were also examined. Dose discrepancies between corrected and uncorrected datasets were not significant for low-Z material. High-Z materials caused under-dosage of 20%-25% in the region surrounding the metal and over dosage of 10%-15% downstream of the hardware. Gamma index test yielded P. < 1> 99% for all low-Z cases; while for high-Z cases it returned 91% < P. < 1< 99%. Analysis of the depth dose curve of a single beam for low-Z cases revealed that, although the dose attenuation is altered inside the metal, it does not differ downstream of the insert. However, for high-Z metal implants the dose is increased up to 10%-12% around the insert. In addition, Monte Carlo method was more sensitive to the presence of metal inserts than superposition/convolution algorithm. The reduction in terms of dose of metal artifacts in CT images is relevant for high-Z implants. In this case, dose distribution should be calculated using Monte Carlo algorithms, given their superior accuracy in dose modeling in and around the metal."

According to the news editors, the research concluded: "In addition, the knowledge of the composition of metal inserts improves the accuracy of the Monte Carlo dose calculation significantly. c 2014 American Association of Physicists in Medicine."

For more information on this research see: The impact of low-Z and high-Z metal implants in IMRT: A Monte Carlo study of dose inaccuracies in commercial dose algorithms. Medical Physics, 2014;41(1):57-66. Medical Physics can be contacted at: Amer Assoc Physicists Medicine Amer Inst Physics, Ste 1 No 1, 2 Huntington Quadrangle, Melville, NY 11747-4502, USA. (American Association of Physicists in Medicine - www.aapm.org; Medical Physics - online.medphys.org/)

The news correspondents report that additional information may be obtained from M.F. Spadea, Fdn CNAO, Bioengn Unit, I-27100 Pavia, Italy. Additional authors for this research include J.M. Verburg, G. Baroni and J. Seco (see also Algorithms).

Keywords for this news article include: Pavia, Italy, Europe, Algorithms

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Source: Health & Medicine Week


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