Treatment Plans.

<p>Four-field box treatments (left and center) and five-field brain IMRT (right) treatment plans from Eclipse TPS. View of IMRT axial view and predicted dose view scaled to show plastic head-insert.</p

Flood Field Omission.

<p>The stability of the solid-tank enables a simplified acquisition technique without requiring a flood field. (a) Reconstructed central axial slice through a dosimeter irradiated with 5 small fields incident on the upper surface with different doses. (b) Reconstructing the data with and without flood-field correction (techniques outlined in previous section) indicate the new flood-field-free reconstructions were equivalent to the conventional method.</p

Treatment Plan 2—Gamma Maps.

<p>Three orthogonal views of 3%/3mm gamma maps for DFOS (column 2), DMOS (column 3), and DLOS (right) systems, with passing rates. Eclipse dose views (left) for reference.</p

Treatment Plan 2—Results.

<p>Eclipse predicted dose (left), DFOS reconstructed dose (second column), DMOS reconstructed dose (third column), and DLOS reconstructed dose (right) for three orthogonal planes in four-field box irradiation.</p

Summary of gamma 3%/3mm pass rates for all irradiations.

<p>Summary of gamma 3%/3mm pass rates for all irradiations.</p

Comparison of All Three Systems.

<p>Mean OD change (ΔOD) for the 4 distinct dose regions within the 4-field box treatment. The DFOS system is compared to the DLOS (blue) and DMOS (green). Also shown are linear fits for the two gold-standard systems compared to DFOS. Error bars span 2 standard deviations (95% confidence) for all systems.</p

Treatment Plan 3—Results.

<p>Eclipse predicted dose (left), DFOS reconstructed dose (middle) and DLOS dose (right) for three orthogonal views in brain IMRT plan.</p

Coefficient of variation for mean ΔOD values for all systems, calculated for the 3 treated dose regions within the second 4-field box treatment plan.

<p>Coefficient of variation for mean ΔOD values for all systems, calculated for the 3 treated dose regions within the second 4-field box treatment plan.</p

Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid

<div><p>Telecentric optical computed tomography (optical-CT) is a state-of-the-art method for visualizing and quantifying 3-dimensional dose distributions in radiochromic dosimeters. In this work a prototype telecentric system (DFOS—Duke Fresnel Optical-CT Scanner) is evaluated which incorporates two substantial design changes: the use of Fresnel lenses (reducing lens costs from $10-30K t0$1-3K) and the use of a ‘solid tank’ (which reduces noise, and the volume of refractively matched fluid from 1ltr to 10cc). The efficacy of DFOS was evaluated by direct comparison against commissioned scanners in our lab. Measured dose distributions from all systems were compared against the predicted dose distributions from a commissioned treatment planning system (TPS). Three treatment plans were investigated including a simple four-field box treatment, a multiple small field delivery, and a complex IMRT treatment. Dosimeters were imaged within 2h post irradiation, using consistent scanning techniques (360 projections acquired at 1 degree intervals, reconstruction at 2mm). DFOS efficacy was evaluated through inspection of dose line-profiles, and 2D and 3D dose and gamma maps. DFOS/TPS gamma pass rates with 3%/3mm dose difference/distance-to-agreement criteria ranged from 89.3% to 92.2%, compared to from 95.6% to 99.0% obtained with the commissioned system. The 3D gamma pass rate between the commissioned system and DFOS was 98.2%. The typical noise rates in DFOS reconstructions were up to 3%, compared to under 2% for the commissioned system. In conclusion, while the introduction of a solid tank proved advantageous with regards to cost and convenience, further work is required to improve the image quality and dose reconstruction accuracy of the new DFOS optical-CT system.</p></div

Dose Distribution Line Profiles.

<p>Representative line profiles from 3 dosimeters (irradiated with the 3 different dose distributions as indicated), each scanned with 3 optical-CT scanners. Elevated noise levels can be seen with the DFOS system.</p