Direct measurement of intratumor dose-rate distributions in experimental xenografts treated with 90Y-labeled radioimmunotherapy

Mayer, Rulon; Dillehay, Larry E.; Shao, Yi; Zhang, Yong Gang; Song, Shiyu; Bartholomew, Richard M.; Mackenson, Daniel G.; Williams, Jerry R.

doi:10.1016/0360-3016(95)00567-i

Cited by 7 publications

(5 citation statements)

References 11 publications

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“…The exposed radiochromic film was scanned, similar to earlier studies, [12][13][14][15][16] with a CanoScan LiDE 700F flatbed scanner in reflection mode using 48 bit digital resolution to digitize the three color channels (Red, Green, and Blue) at a spatial resolution of 40 dpi to conform to the ECLIPSE treatment planning system. All correction options were turned off.…”

Section: Iib Scanningmentioning

confidence: 99%

“…The dose D might be generated by inserting the computed shift D [Eq. (13)] into the corrected average multichannel dose [Eq. (14)].…”

Section: Dði; Jþmentioning

confidence: 99%

“…The recent advent of EBT2 radiochromic film has spawned a number of articles examining the new film's properties and procedures for achieving optimal dosimetry. Digitization of the radiochromic film through scanning with a flatbed scanner and exploiting its ability to extract individual color components for the imagery was examined some time ago 12,13 and has become a standard procedure. 14,15 Common mode rejection (taking the ratio of images from two different color channels) was employed to buck out the effect of thickness=composition variations, in particular, Ohuchia 3 used the red and green channels.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced dosimetry procedures and assessment for EBT2 radiochromic film

Mayer

Chen

et al. 2012

Medical Physics

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This study described, developed, and tested new processing methods for reducing inaccuracies in absolute dose determination due to inhomogeneities within the film and from scanning. This study found better performance using optimized multichannel following averaging of all color channels. Combining the channel ratios in a hybrid approach also achieved high performance. Averaging the test films reduced temporal noise that severely degraded the blue channel. This methodology avoided using cumbersome, registered correction matrices. Novel registration and digital rotation of CT images enabled quantitative testing and helped improve contact between the radiochromic film and phantom.

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Section: Iib Scanningmentioning

confidence: 99%

“…The dose D might be generated by inserting the computed shift D [Eq. (13)] into the corrected average multichannel dose [Eq. (14)].…”

Section: Dði; Jþmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhanced dosimetry procedures and assessment for EBT2 radiochromic film

Mayer

Chen

et al. 2012

Medical Physics

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“…The darkening due to the proton radiation was digitized after scanning the films with a reflective scanner (CanoScan LIDE 700F) and the film grey levels were converted to dose with the aid of calibration films. [23][24][25][26] Calibration films were positioned at D max and exposed to 6 MeV x-rays from a Varian Trilogy machine. To autonomously handle media imperfections, Mayer 27 and Micke 28 conceived and tested a multichannel optimization approach and found significant improvements relative to employing a single red channel.…”

Section: Introductionmentioning

confidence: 99%

Proposed linear energy transfer areal detector for protons using radiochromic film

Mayer

Lin

Fager

et al. 2015

Review of Scientific Instruments

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Radiation therapy depends on predictably and reliably delivering dose to tumors and sparing normal tissues. Protons with kinetic energy of a few hundred MeV can selectively deposit dose to deep seated tumors without an exit dose, unlike x-rays. The better dose distribution is attributed to a phenomenon known as the Bragg peak. The Bragg peak is due to relatively high energy deposition within a given distance or high Linear Energy Transfer (LET). In addition, biological response to radiation depends on the dose, dose rate, and localized energy deposition patterns or LET. At present, the LET can only be measured at a given fixed point and the LET spatial distribution can only be inferred from calculations. The goal of this study is to develop and test a method to measure LET over extended areas. Traditionally, radiochromic films are used to measure dose distribution but not for LET distribution. We report the first use of these films for measuring the spatial distribution of the LET deposited by protons. The radiochromic film sensitivity diminishes for large LET. A mathematical model correlating the film sensitivity and LET is presented to justify relating LET and radiochromic film relative sensitivity. Protons were directed parallel to radiochromic film sandwiched between solid water slabs. This study proposes the scaled-normalized difference (SND) between the Treatment Planning system (TPS) and measured dose as the metric describing the LET. The SND is correlated with a Monte Carlo (MC) calculation of the LET spatial distribution for a large range of SNDs. A polynomial fit between the SND and MC LET is generated for protons having a single range of 20 cm with narrow Bragg peak. Coefficients from these fitted polynomial fits were applied to measured proton dose distributions with a variety of ranges. An identical procedure was applied to the protons deposited from Spread Out Bragg Peak and modulated by 5 cm. Gamma analysis is a method for comparing the calculated LET with the LET measured using radiochromic film at the pixel level over extended areas. Failure rates using gamma analysis are calculated for areas in the dose distribution using parameters of 25% of MC LET and 3 mm. The processed dose distributions find 5%-10% failure rates for the narrow 12.5 and 15 cm proton ranges and 10%-15% for proton ranges of 15, 17.5, and 20 cm and modulated by 5 cm. It is found through gamma analysis that the measured proton energy deposition in radiochromic film and TPS can be used to determine LET. This modified film dosimetry provides an experimental areal LET measurement that can verify MC calculations, support LET point measurements, possibly enhance biologically based proton treatment planning, and determine the polymerization process within the radiochromic film.

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“…In radionuclide therapy, the dose rate is temporally variant and a number of investigators have examined the implications of this on tumor control and normal tissue toxicity (21)(22)(23)(24)(25)(26). To date, almost all clinical studies have considered total absorbed dose, the majority of which is delivered at an exponentially decreasing dose rate, while the benchmark for projecting potential toxicity and justifying initial phase I activity and absorbed dose levels has been the experience with normal organ tolerance in external beam radiotherapy, the majority of which is delivered at high dose-rate in daily 2-Gy …”

Section: Introductionmentioning

confidence: 99%

Patient-Specific Dosimetry and Radiobiological Modeling of Targeted Radionuclide Therapy Grant - final report

Sgouros¹

2007

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Phantom-based and patient-specific imaging-based dosimetry methodologies have traditionally yielded mean organ absorbed doses or spatial dose distributions over tumors and normal organs. In this work, radiobiological modeling is introduced to convert the spatial distribution of absorbed dose into biologically effective dose and equivalent uniform dose parameters. The methodology is illustrated using data from a thyroid cancer patient treated with radioiodine. METHODS: Three registered SPECT/CT scans were used to generate 3-D images of radionuclide kinetics (clearance rate) and cumulated activity. The cumulated activity image and corresponding CT were provided as input into an EGSnrc-based Monte Carlo calculation; the cumulated activity image defined the distribution of decays while an attenuation image derived from CT was used to define the corresponding spatial tissue density and composition distribution. The rate images were used to convert the spatial absorbed dose distribution to a Biologically Effective Dose (BED) distribution which was then used to estimate a single Equivalent Uniform Dose (EUD) for segmented volumes of interest. EUD was also calculated from the absorbed dose distribution directly. RESULTS: Validation using simple models and also comparison of the dose-volume histogram to a previously analyzed clinical case is shown as well as the mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for an illustrative clinical case of a pediatric thyroid cancer patient with diffuse lung metastases. The mean absorbed dose, mean BED and EUD for tumor was 57.7, 58.5 and 25.0 Gy, respectively. Corresponding values for normal lung tissue were 9.5, 9.8 and 8.3 Gy, respectively. CONCLUSION The analysis demonstrates the impact of radiobiological modeling on response prediction. The 57% reduction in the equivalent dose value for the tumor reflects a high level of dose non-uniformity in the tumor and a corresponding reduced likelihood of achieving a tumor response. Such analyses are expected to be useful in treatment planning for radionuclide therapy.

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Direct measurement of intratumor dose-rate distributions in experimental xenografts treated with 90Y-labeled radioimmunotherapy

Cited by 7 publications

References 11 publications

Enhanced dosimetry procedures and assessment for EBT2 radiochromic film

Enhanced dosimetry procedures and assessment for EBT2 radiochromic film

Proposed linear energy transfer areal detector for protons using radiochromic film

Patient-Specific Dosimetry and Radiobiological Modeling of Targeted Radionuclide Therapy Grant - final report

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