Evaluation of the performance of VIPAR polymer gels using a variety of x-ray and electron beams

Pappas, E.; Angelopoulos, A.; Kipouros, P.; Vlachos, L.; Xenofos, S; Seimenis, Ioannis

doi:10.1088/0031-9155/48/5/401

Cited by 15 publications

(11 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although polymer gel dosimetry is still a questionable method for absolute dosimetry, 18,22 its satisfying performance for relative dosimetry has been well documented. [23][24][25][26] ͑2͒ Since polymer gels are practically water equivalent 27 having the role of both phantom and dosimeter ͑unlike conventional detectors͒ they do not perturb the charged particle fluence and do not result in related beam penumbra alterations. ͑3͒ The detection size of this dosimetric tool is determined by the MR-imaging voxel size 28 which can exhibit any desired value down to sub-mm 3 ͑Refs.…”

Section: Introductionmentioning

confidence: 99%

Experimental determination of the effect of detector size on profile measurements in narrow photon beams

et al. 2006

View full text Add to dashboard Cite

The aim of this work is to investigate experimentally the detector size effect on narrow beam profile measurements. Polymer gel and magnetic resonance imaging dosimetry was used for this purpose. Profile measurements (Pm(s)) of a 5 mm diameter 6 MV stereotactic beam were performed using polymer gels. Eight measurements of the profile of this narrow beam were performed using correspondingly eight different detector sizes. This was achieved using high spatial resolution (0.25 mm) two-dimensional measurements and eight different signal integration volumes A X A X slice thickness, simulating detectors of different size. "A" ranged from 0.25 to 7.5 mm, representing the detector size. The gel-derived profiles exhibited increased penumbra width with increasing detector size, for sizes >0.5 mm. By extrapolating the gel-derived profiles to zero detector size, the true profile (Pt) of the studied beam was derived. The same polymer gel data were also used to simulate a small-volume ion chamber profile measurement of the same beam, in terms of volume averaging. The comparison between these results and actual corresponding small-volume chamber profile measurements performed in this study, reveal that the penumbra broadening caused by both volume averaging and electron transport alterations (present in actual ion chamber profile measurements) is a lot more intense than that resulted by volume averaging effects alone (present in gel-derived profiles simulating ion chamber profile measurements). Therefore, not only the detector size, but also its composition and tissue equivalency is proved to be an important factor for correct narrow beam profile measurements. Additionally, the convolution kernels related to each detector size and to the air ion chamber were calculated using the corresponding profile measurements (Pm(s)), the gel-derived true profile (Pt), and convolution theory. The response kernels of any desired detector can be derived, allowing the elimination of the errors associated with narrow beam profile measurements.

show abstract

Section: Introductionmentioning

confidence: 99%

Experimental determination of the effect of detector size on profile measurements in narrow photon beams

et al. 2006

View full text Add to dashboard Cite

show abstract

“…In this study, Vinylpyrrolidone‐based polymer gels were used. A detailed description of Vinylpyrrolidone‐(VIPAR) based polymer gels, the manufacturing process, and their dosimetric characteristics can be found in the literature 17 , 18 , 19 , 20 . Polymer‐gel MRI dosimetry is based on the radiation‐induced polymerization of the gel monomers and cross‐linkers.…”

Section: Methodsmentioning

confidence: 99%

“…A detailed description of Vinylpyrrolidone-(VIPAR) based polymer gels, the manufacturing process, and their dosimetric characteristics can be found in the literature. (17)(18)(19)(20) Polymer-gel MRI dosimetry is based on the radiation-induced polymerization of the gel monomers and cross-linkers. The amount of absorbed dose in an elementary gel volume is directly related with the amount of polymerization within that volume, and this in turn is directly related to the spin-spin (T 2 ) relaxation time of that volume.…”

Section: Dual Diode Array Measurement Of Dose Distribution and Gi mentioning

confidence: 99%

Dosimetric validation for an automatic brain metastases planning software using single‐isocenter dynamic conformal arcs

Liu

Pappas

et al. 2016

J Applied Clin Med Phys

View full text Add to dashboard Cite

An automatic brain‐metastases planning (ABMP) software has been installed in our institution. It is dedicated for treating multiple brain metastases with radiosurgery on linear accelerators (linacs) using a single‐setup isocenter with noncoplanar dynamic conformal arcs. This study is to validate the calculated absolute dose and dose distribution of ABMP. Three types of measurements were performed to validate the planning software: 1, dual micro ion chambers were used with an acrylic phantom to measure the absolute dose; 2, a 3D cylindrical phantom with dual diode array was used to evaluate 2D dose distribution and point dose for smaller targets; and 3, a 3D pseudo‐in vivo patient‐specific phantom filled with polymer gels was used to evaluate the accuracy of 3D dose distribution and radiation delivery. Micro chamber measurement of two targets (volumes of 1.2 cc and 0.9 cc, respectively) showed that the percentage differences of the absolute dose at both targets were less than 1%. Averaged GI passing rate of five different plans measured with the diode array phantom was above 98%, using criteria of 3% dose difference, 1 mm distance to agreement (DTA), and 10% low‐dose threshold. 3D gel phantom measurement results demonstrated a 3D displacement of nine targets of 0.7±0.4 mm (range 0.2 ~ 1.1 mm). The averaged two‐dimensional (2D) GI passing rate for several region of interests (ROI) on axial slices that encompass each one of the nine targets was above 98% (5% dose difference, 2 mm DTA, and 10% low‐dose threshold). Measured normalD95, the minimum dose that covers 95% of the target volume, of the nine targets was 0.7% less than the calculated normalD95. Three different types of dosimetric verification methods were used and proved the dose calculation of the new automatic brain metastases planning (ABMP) software was clinical acceptable. The 3D pseudo‐in vivo patient‐specific gel phantom test also served as an end‐to‐end test for validating not only the dose calculation, but the treatment delivery accuracy as well.PACS number(s): 87.53.Lv, 87.55.km, 87.55.Qr

show abstract

“…BANG (bisacrylamide nitrogen gelatine) has been commercialised with multiple formulations, such as BANG-1 33 that is made with powdered acrylamide and BANG-2 6, 36 that uses acrylic acid as a monomer with sodium hydroxide to alter the pH. Other gels of reduced toxicity exist, such as PABIG (polyethylene glycol diacrylate bis gelatine) 37 and VIPAR (N-vinyl pyrolidone argon gel) [38][39][40] . Fong et al developed a normoxic gel dosimeter, MAGIC (methacrylic acid, ascorbic acid in gelatine initiated by copper), which does not require an oxygen-free environment to be prepared 41 .…”

Section: Gel Dosimetersmentioning

confidence: 99%

The effective atomic number of dosimetric gels

Taylor

Franich

Trapp

et al. 2008

Australas. Phys. Eng. Sci. Med.

View full text Add to dashboard Cite

Radiological properties of gel dosimeters and phantom materials are often compared against each other and against water or tissue by consideration parameters including their effective atomic number, Zeff. Effective atomic numbers have been calculated for a range of ferrous-sulphate and polymeric gel dosimeters using mass attenuation coefficient data over the energy range 10 keV to 10 MeV. Data is presented relative to water to allow direct comparison over a range of energies. These data provide energy specific values of Zeff which improves on the practice of applying a power-law based formula to estimate an energy independent value. For applications that require a single value of Zeff, the data presented here allows the choice of a value appropriate to the energy of the photon source or a spectrum-weighted average. Studying the variation of Zeff, which is equivalent to taking into account the variation of mass attenuation coefficients with photon energy, it is found that gels typically match water better than water matches human tissues. As such, the subtle differences in effective atomic number between water and gels are small and may be considered negligible. Consideration of the mean disparity over a large energy range shows, broadly, BANG-1 to be the most water equivalent gel.

show abstract

Evaluation of the performance of VIPAR polymer gels using a variety of x-ray and electron beams

Cited by 15 publications

References 28 publications

Experimental determination of the effect of detector size on profile measurements in narrow photon beams

Experimental determination of the effect of detector size on profile measurements in narrow photon beams

Dosimetric validation for an automatic brain metastases planning software using single‐isocenter dynamic conformal arcs

The effective atomic number of dosimetric gels

Contact Info

Product

Resources

About