Translucent poly(vinyl alcohol) cryogel dosimeters for simultaneous dose buildup and monitoring during chest wall radiation therapy

Abstract

Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phantom was shifted by ±2,±3, and ±5 mm from the planned position in the anterior/posterior (A/P) direction; these shifts represent setup errors and the uncertainty associated with lung filling during breath‐hold. The two‐dimensional absolute dose distributions measured in the cryogel at the planned position were compared with the distributions at all shifts from this position using gamma analysis (3%/3 mm, 10% threshold). For shifts of ±2,±3, and ±5 mm the passing rates ranged from 94.3% to 95.6%, 74.0% to 78.8%, and 17.5% to 22.5%, respectively. These results are consistent with the same gamma analysis performed on dose planes calculated in the middle of the cryogel and on the phantom surface using our treatment planning system, which ranged from 94.3% to 95.0%, 76.8% to 77.9%, and 23.5% to 24.3%, respectively. The Pinnacle dose planes were then scaled empirically and compared to the cryogel measurements. Using the same gamma metric, the pass rates ranged from 97.0% to 98.4%. The results of this study suggest that cryogels may be used as both a buildup material and to evaluate errors in chest wall treatment positioning during deep‐inspiration breath‐hold delivery. The cryogels are sensitive to A/P chest wall shifts of less than 3 mm, which potentially allows for the detection of clinically relevant errors.PACS number(s): 87.55.km, 87.57.uq

Measurement of skin surface dose distributions in radiation therapy using poly(vinyl alcohol) cryogel dosimeters

“…The relationship between absorption coefficient and dose delivered to the 0.5 cm slabs of radiochromic bolus in its linear range was (3.00 ± 0.04) × 10 −4 mm −1 cGy −1 , which is consistent with our previous measurements . Figure shows the irradiated radiochromic bolus and EBT‐2 film following exposures of 1000 MU at gantry angles of 0°, 45°, and 90°.…”

“…These cryogels may be used as both a buildup material and act as an in vivo dosimeter to monitor the treatment delivery. These cryogels were used to monitor chest wall radiation therapy treatment; it can quantitate uncertainties in setup, and breathing irregularities during left breast or chest wall deep inspiration breathing hold (DIBH) technique . And therefore, the PVA‐C‐based dosimeter may used as a dosimetric bolus for simultaneous skin dose boosting and measurement during radiotherapy to provide an accurate estimation of superficial dose distribution.…”

Optimizing the feasibility of polyvinyl alcohol-potassium iodine gel for medical dosimeter

“…All components were collected in alight-tight box. This system has been used previously and shown to be an excellent imaging gel dosimetry system for 2D dose and absorbance change maps with radiation therapy applications [21,22,34,36]. The scanning of the pre and post irradiated gel templates (i.e., 2D absorbance maps) were obtained with RGB source using the CCD camera camware software.…”

“…One of the known kinds of radiochromic gels is the Fricke gel that combined with the dyes of Xyleno Orange (XO) dye and Methyl thymol blue (MTB) dye [14,[17][18][19]. During irradiation, the oxidation of ferrous ions to ferric ions can be occur [20][21][22][23][24]. Various approaches have been applied to reduce the diffusion in Fricke gels through this filed.…”

Thin poly(vinyl alcohol) cryogels: reactive groups, macropores and translucency in microtiter plate assays

“…An attractive property of cryogels, which has rarely been studied, is their translucency allowing photometric studies. Recently, a radiochromic dosimeter [3] has been developed by incorporation of xylenol orange – iron (II) complexes into a poly(vinyl alcohol) (PVA) cryogel. Thin hydrogels of gelatin [4], polyacrylamide [5] or poly(N,N-dimethylacrylamide) [6] produced in non-frozen solutions were earlier studied as immobilization media for reactive dyes able to change their spectral characteristics in response to low molecular weight analytes such as metal ions or saccharides.…”