Comparison of two-dimensional transmitted dose maps: evaluation of existing algorithms

Mohammadi, Mohammad; Bezak, Eva; Reich, P

doi:10.1007/bf03178891

Cited by 5 publications

(2 citation statements)

References 22 publications

(20 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has been shown that in the presence of homogenous attenuators, there is a reasonable agreement between EPID and TPS dose values for large radiation fields. [43,44] The results prove that the calibration method used in this study guaranties sufficient accuracy when using the EPID dosimetry.…”

Section: Resultssupporting

confidence: 52%

Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device

Mohammadi

Bezak

2012

J Med Phys

View full text Add to dashboard Cite

The dose delivery verification for a head and neck static intensity modulated radiation therapy (IMRT) case using a scanning liquid ionization chamber electronic portal imaging device (SLIC-EPID) was investigated. Acquired electronic portal images were firstly converted into transmitted dose maps using an in-house developed method. The dose distributions were then compared with those calculated in a virtual EPID using the Pinnacle3 treatment planning system (TPS). Using gamma evaluation with the ΔDmax and DTA criteria of 3%/2.54 mm, an excellent agreement was observed between transmitted dose measured using SLIC-EPID and that calculated by TPS (gamma score approximately 95%) for large MLC fields. In contrast, for several small subfields, due to SLIC-EPID image blurring, significant disagreement was found in the gamma results. Differences between EPID and TPS dose maps were also observed for several parts of the radiation subfields, when the radiation beam passed through air on the outside of tissue. The transmitted dose distributions measured using portal imagers such as SLIC-EPID can be used to verify the dose delivery to a patient. However, several aspects such as accurate calibration procedure and imager response under different conditions should be taken into the consideration. In addition, SLIC-EPID image blurring is another important issue, which should be considered if the SLIC-EPID is used for clinical dosimetry verification.

show abstract

Section: Resultssupporting

confidence: 52%

Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device

Mohammadi

Bezak

2012

J Med Phys

View full text Add to dashboard Cite

show abstract

“…In addition, although the gamma function is a powerful tool to recognize the agreed and disagreed areas, it is not able to separate the over and underdose regions. [16] Moreover, if there is a search for a consistent dose value in neighboring points in a two-dimensional area, this cannot be extended into a volume. The hypothesis of this study is that “with extension into the third dimension, consideration of the “less or more” fluctuations in the z direction, caused by patient positioning, organ motion, couch positioning, and isocenter calibration, for the point dose displacement in the z dimension can be achieved”.…”

Section: Introductionmentioning

confidence: 99%

Modification of the gamma function for the recognition of over- and under-dose regions in three dimensions

Mohammadi¹,

Rostampour²,

Rutten³

2012

J Med Phys

View full text Add to dashboard Cite

In order to evaluate two-dimensional radiation dose distributions, an algorithm called the Gamma function has recently been modified. The current study concentrates on modification of the gamma function as a three-dimensional dose distribution evaluation tool, and includes the recognition of over-dose/under-dose areas. Using a sign term, the conventional gamma function separates the disagreed areas into two parts: over-dose and under-dose areas. The new gamma function was modified using an extension of the dose difference criterion, ΔD, from two dimensions into three dimensions. In order to provide two-dimensional dose maps for analysis, several images were acquired for a range of regular and irregular radiation fields using a Scanning Liquid Ionization Chamber Electronic Portal Imaging Device. The raw images were then converted into two-dimensional transmitted dose maps using an empirical method. They were utilized as reference dose maps. Translational and rotational manipulations were performed on the reference dose distribution maps to provide evaluated dose maps. The reference and evaluated dose maps were then compared using conventional and modified gamma tools. The results indicated that the modified algorithm is able to enhance the over- and under-dose regions. In addition, a slight increase of the agreement percentage for reference and evaluated dose maps were observed by the extension of ΔD to three dimensions. It is concluded that the modified method is more realistic and applicable for the evaluation of both two-dimensional and three-dimensional dose distributions.

show abstract

Thirty year celebration of journal publications on radiation oncology medical physics

Oliver

2007

Australas. Phys. Eng. Sci. Med.

View full text Add to dashboard Cite

The Australasian Physical & Engineering Sciences in Medicine Journal (APESM) is an avenue for the profession to report scientific work in medicine; provide a facility for the publication of current work, new research and new techniques developed or reviewed; report on professional news from elsewhere and; publish the Australasian College of Physical Scientists and Engineers in Medicine (ACPSEM) policies and protocols. The journal is a vital instrument within the ACPSEM organisation with a worldwide circulation. This review of APESM on medical physics in radiation oncology is meant to be a progress summary of work in that specialty. Even so, it has become a lengthy appraisal due to the many years involved. In considering publications related to medical physics in radiation oncology, this review has shown the progression of the College journal to an international journal. There is an increase in the number of papers contributed from Asia and other countries world wide for this discipline. Growth in the number of contributions should continue to rise. In order to provide some appreciation of where the present medical physics activity arose from, this article commences its discussion in 1959 and progresses towards the present, describing along the way, from radiation oncology papers published in APESM, the use of linear accelerators, brachytherapy, the medical physics workforce, the formation of the ACPSEM, and the more modern developments in radiotherapy such as 3-D treatment planning and IMRT.

show abstract

Comparison of two-dimensional transmitted dose maps: evaluation of existing algorithms

Cited by 5 publications

References 22 publications

Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device

Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device

Modification of the gamma function for the recognition of over- and under-dose regions in three dimensions

Thirty year celebration of journal publications on radiation oncology medical physics

Contact Info

Product

Resources

About