Left: Monitor units and predicted treatment times for different plan scenarios, with standard deviations.

<p>Right: linear fit of calculated treatment time as a function of segment number of each scenario.</p

Dose-volume histogram of plans shown in Figure 3.

<p>Solid line: 6 MV, dashed line: FFF 7 MV. The right parotid fell inside the PTV, so it received considerable doses as compared with the left parotid, which was spared as much as possible.</p

Visualisation of Respiratory Tumour Motion and Co-Moving Isodose Lines in the Context of Respiratory Gating, IMRT and Flattening-Filter-Free Beams

<div><p>Respiratory motion during percutaneous radiotherapy can be considered based on respiration-correlated computed tomography (4DCT). However, most treatment planning systems perform the dose calculation based on a single primary CT data set, even though cine mode displays may allow for a visualisation of the complete breathing cycle. This might create the mistaken impression that the dose distribution were independent of tumour motion. We present a movie visualisation technique with the aim to direct attention to the fact that the dose distribution migrates to some degree with the tumour and discuss consequences for gated treatment, IMRT plans and flattening-filter-free beams. This is a feasibility test for a visualisation of tumour and isodose motion. Ten respiratory phases are distinguished on the CT, and the dose distribution from a stationary IMRT plan is calculated on each phase, to be integrated into a movie of tumour and dose motion during breathing. For one example patient out of the sample of five lesions, the plan is compared with a gated treatment plan with respect to tumour coverage and lung sparing. The interplay-effect for small segments in the IMRT plan is estimated. While the high dose rate, together with the cone-shaped beam profile, makes the use of flattening-filter-free beams more problematic for conformal and IMRT treatment, it can be the option of choice if gated treatment is preferred. The different effects of respiratory motion, dose build-up and beam properties (segments and flatness) for gated vs. un-gated treatment can best be considered if planning is performed on the full 4DCT data set, which may be an incentive for future developments of treatment planning systems.</p></div

Final optimized inversion constraints.

<p>*exluding parotis where only edge of parotis reaches into PTV.</p

PTV and tumour motion characteristics.

<p>PTV and tumour motion characteristics.</p

Quality measures and doses to organs at risk for all plan scenarios, plotted with standard deviations.

<p>CI: conformity index, HI: homogeneity index, GI: gradient index. Within each plan scenario, segment number decreases from left to right (shown for 6 MV, 7 beams).</p

Box-diagram of CI from pairwise test of 6 MV vs. FFF 7 MV, taking all scenarios (7, 11, or 18 beams) together, for all plans (all) or a given number of segments (given in top line).

<p>Box-diagram of CI from pairwise test of 6 MV vs. FFF 7 MV, taking all scenarios (7, 11, or 18 beams) together, for all plans (all) or a given number of segments (given in top line).</p

Example head & neck plan using 11 beams, 6 MV (left) vs. FFF 7 MV (right), same patient as in Figure 2.

<p>Example head & neck plan using 11 beams, 6 MV (left) vs. FFF 7 MV (right), same patient as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094371#pone-0094371-g002" target="_blank">Figure 2</a>.</p

Baseline Demographic and Patient Characteristics.

<p><i>Abbreviations:</i> 1) NSCLC = non-small cell lung cancer; 2) thereof one patient with two lung lesions.</p

Plan characteristics and IMRT inversion parameters for three different beam arrangements.

<p>Plan characteristics and IMRT inversion parameters for three different beam arrangements.</p