Fast laser optical CT scanner with rotating mirror and Fresnel lenses

Conklin, J. W.; Deshpande, Rashmi; Battista, Jerry; Jordan, Kevin

doi:10.1088/1742-6596/56/1/030

Cited by 13 publications

(8 citation statements)

References 3 publications

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“…However, upgrades to laser CT scanners to improve speed and resolution are in progress. 34,35 III.A.1.c. Spatial resolution Representative raw projection images from the CCD-scanner for an unirradiated PRESAGE™ insert and inserts irradiated with the single rectangular beam treatment, parallel-opposed treatment and IMRT treatment are shown in Figs.…”

Section: Iiia1b Scan Time a Complete Set Of 360 Projectionmentioning

confidence: 99%

Fast, high‐resolution 3D dosimetry utilizing a novel optical‐CT scanner incorporating tertiary telecentric collimation

Sakhalkar

Oldham

2007

Medical Physics

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This study introduces a charge coupled device (CCD) area detector based optical-computed tomography (optical-CT) scanner for comprehensive verification of radiation dose distributions recorded in nonscattering radiochromic dosimeters. Defining characteristics include: (i) a very fast scanning time of ~5 min to acquire a complete three-dimensional (3D) dataset, (ii) improved image formation through the use of custom telecentric optics, which ensures accurate projection images and minimizes artifacts from scattered and stray-light sources, and (iii) high resolution (potentially 50 μm) isotropic 3D dose readout. The performance of the CCD scanner for 3D dose readout was evaluated by comparison with independent 3D readout from the single laser beam OCTOPUS™-scanner for the same PRESAGE™ dosimeters. The OCTOPUS™ scanner was considered the "gold standard" technique in light of prior studies demonstrating its accuracy. Additional comparisons were made against calculated dose distributions from the ECLIPSE treatment-planning system. Dose readout for the following treatments were investigated: (i) a single rectangular beam irradiation to investigate small field and very steep dose gradient dosimetry away from edge effects, (ii) a 2-field open beam parallel-opposed irradiation to investigate dosimetry along steep dose gradients, and (iii) a 7-field intensity modulated radiation therapy (IMRT) irradiation to investigate dosimetry for complex treatment delivery involving modulation of fluence and for dosimetry along moderate dose gradients. Dose profiles, dose-difference plots, and gamma maps were employed to evaluate quantitative estimates of agreement between independently measured and calculated dose distributions. Results indicated that dose readout from the CCD scanner was in agreement with independent gold-standard readout from the OCTOPUS™-scanner as well as the calculated ECLIPSE dose distribution for all treatments, except in regions within a few millimeters of the edge of the dosimeter, where edge artifact is predominant. Agreement of line profiles was observed, even along steep dose gradients. Dose difference plots indicated that the CCD scanner dose readout differed from the OCTOPUS™ scanner readout and ECLIPSE calculations by ~10% along steep dose gradients and by ~5% along moderate dose gradients. Gamma maps (3% dose-difference and 3 mm distance-toagreement acceptance criteria) revealed agreement, except for regions within 5 mm of the edge of the dosimeter where the edge artifact occurs. In summary, the data demonstrate feasibility of using the fast, high-resolution CCD scanner for comprehensive 3D dosimetry in all applications, except where dose readout is required close to the edges of the dosimeter. Further work is ongoing to reduce this artifact.

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Section: Iiia1b Scan Time a Complete Set Of 360 Projectionmentioning

confidence: 99%

Fast, high‐resolution 3D dosimetry utilizing a novel optical‐CT scanner incorporating tertiary telecentric collimation

Sakhalkar

Oldham

2007

Medical Physics

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“…Immersion of dosimeters in a refractively matched fluid is a ubiquitous technique to minimize refraction artifacts in optical-CT 3D dosimetry. [1][2][3][4][5] Radiochromic dosimeters such as PRESAGE R (Ref. 6) have high refractive index (RI) of ∼1.50.…”

Section: Introductionmentioning

confidence: 99%

On the feasibility of optical‐CT imaging in media of different refractive index

Rankine

Oldham

2013

Medical Physics

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For applications where dose information is not required in the periphery of the dosimeter, some dry and low-viscous matching configurations may be feasible. For all three dose distributions (uniform, VMAT, brachytherapy) the point source geometry produced slightly more favorable results (an extra 1%-2% usable radii) than parallel and converging. When dosimetry is required on the periphery, best results were obtained using close refractive matching and ART. A concern for water or dry-scanning is the increase in required detector size, introducing potential cost penalties for manufacturing.

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“…Micro optical-CT has been used to study the characteristics of a high-dose gradient dosimeter [30] . To improve scanning speed, a rotating mirror and Fresnel lenses were used [31] – [33] . A significant development in optical-CT scanning was proposed by Krstajic and Doran (2007) [15] – [17] .…”

Section: Methodsmentioning

confidence: 99%

“…To consider the curvature effect in the response function, the test for curvature was performed by adding five center points to the 2 4 factorial designs. Finally, the regression model was represented by the terms of the coded factors [33] . Two batches of gels of the same composition were produced to replicate the experiments.…”

Section: Methodsmentioning

confidence: 99%

Effect of Composition Interactions on the Dose Response of an N-Isopropylacrylamide Gel Dosimeter

Chang

Hsieh²

2012

PLoS ONE

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In this study, a two-level full factorial design was used to identify the effects of the interactions between compositions in an N-isopropylacrylamide (NIPAM) gel dosimeter involving the following variables: (A) gelatin, (B) NIPAM, (C) the crosslinker N, N′-methylene-bis-acrylamide (Bis), and (D) the antioxidant tetrakis (hydroxymethyl) phosphonium chloride (THPC). The dose range was from 0 Gy to 5 Gy. Optical computed tomography was used to scan the polymer gel dosimeter. Each component was set to two levels for all four variables, including (A) 4% and 6%, (B) 4% and 6%, (C) 2% and 4%, as well as (D) 5 and 15 mM. Response surface methodology and a central composite design were adopted for the quantitative investigation of the respective interaction effects on the dose response curve of the gel. The results showed that the contributions of the interaction effects, i.e., AB (6.22%), AC (8.38%), AD (7.74%), BC (9.44%), ABC (18.24%), BCD (12.66%), and ABCD (13.4%), were greater than those of the four main effects, accounting for over 76.08% of the total variability. These results also indicated that the NIPAM gel recipe with the highest sensitivity was at 40%C (mass fraction of Bis).

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Fast laser optical CT scanner with rotating mirror and Fresnel lenses

Cited by 13 publications

References 3 publications

Fast, high‐resolution 3D dosimetry utilizing a novel optical‐CT scanner incorporating tertiary telecentric collimation

Fast, high‐resolution 3D dosimetry utilizing a novel optical‐CT scanner incorporating tertiary telecentric collimation

On the feasibility of optical‐CT imaging in media of different refractive index

Effect of Composition Interactions on the Dose Response of an N-Isopropylacrylamide Gel Dosimeter

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