Comparison of intensity‐modulated radiotherapy and forward‐planning dynamic arc therapy techniques for prostate cancer

Abstract

We compare an inverse‐planning intensity‐modulated radiotherapy (IMRT) technique with three previously published forward‐planning dynamic arc therapy techniques and a newly implemented technique for treatment of prostate only. The three previously published dynamic arc techniques are dynamic arc therapy (DAT), two‐axis dynamic arc therapy (2A‐DAT), and modified dynamic arc therapy (M‐DAT). The newly implemented technique is the bilateral wedged dynamic arc (BW‐DAT). In all dynamic arcs, the multileaf collimator is moving during rotation to fit the prostate, except that, in 2A‐DAT, it is fitting two separate symmetrical rhombi including the prostate. The rectum is shielded during rotation only in the cases of M‐DAT and BW‐DAT.The results obtained indicate that the BW‐DAT, M‐DAT, and DAT techniques provide the intended dose coverage of the prescribed dose to the planning target volume (PTV)—that is, 95% of the PTV is covered by 100% of the dose. The maximum dose to a 3‐cm margin of healthy tissue that surrounds the PTV is lower by 2.5% in the case of IMRT than in both BW‐DAT and M‐DAT, but it is lower by 5.0% than that in both DAT and 2A‐DAT. The maximum dose to the rest of the healthy tissue in the case of BW‐DAT is 33.2Gy±2.2Gy. This dose covers percentage healthy body volumes of 8%±3.2% with IMRT, 4%±1.5% with DAT, and 6%±1.2% with both 2A‐DAT and M‐DAT. Also, this dose is much lower than the accepted maximum dose (52 Gy) to the femoral heads and necks according to Report 62 from the International Commission on Radiation Units and Measurements. Accordingly, it would be possible to neglect delineation of the femoral heads and necks as organs at risk in cases of BW‐DAT.Doses to 15%, 25%, 35%, and 50% (D15%, D25%, D35%, and D50%) of the rectum volume in the case of BW‐DAT were 43.5Gy±8.6Gy, 24.2Gy±8.7Gy, 13.2Gy±4.2Gy, and 5.7Gy±2.1Gy respectively. The D15% of rectum in the case of IMRT was lower than that in BW‐DAT, M‐DAT, 2A‐DAT, and DAT by 7.3%, 10.3%, 33.0%, and 17.6% of the prescribed dose (78 Gy in 39 fractions) respectively. The D25%, D35%, and D50% of the rectum volume in the cases of IMRT and DAT were comparable (with a maximum variation of 4.5%); they were similarly comparable in the cases of M‐DAT and BW‐DAT (with maximum variation of 1.5%). These same doses in BW‐DAT were lower than those in IMRT by 8.7%, 10.6%, and 6.2% respectively, but they were quite lower than those in 2A‐DAT, because the average variation was 41.6% (with a maximum of 44.0%).The D15%, D25%, D35%, and D50% of the bladder volume in the case of BW‐DAT were 33.2Gy±10.9Gy, 17.4Gy±7.9Gy, 6.5Gy±4.3Gy, and 4.2Gy±3.5Gy respectively. The D15% and D25% of the bladder in the cases of IMRT, M‐DAT, and BW‐DAT were comparable (with a maximum variation of 2.2% and 3.6% respectively), and the mean values of each dose were lower in DAT by 14.3% and 11.7% respectively. However, the values of D35% and D50% in the four techniques were comparable, with maximum variations of 5.1% and 2.7% respectively. The D15%, D25%, D35%, and D50% of the bladder in the ...

Implementation of a wedged-dynamic arc therapy technique for head and neck cancer

“…In the analogy of the previously applied technique for prostate, [8] four half arcs covering 350° (0°-165°, 165°-0°, 185°-0°, 0°-185°) with a hard 45° wedge was applied. Each bilateral pair of arcs was in opposite orientations as shown in Figure 1.…”

“…Film calibration was performed with five kodak extended dose range (EDR2) films (Gammex rmi, Middleton, WI) and 30 cm × cm 30 × 30 cm solid water phantom (PTW-29672: PTW) typically as previously published. [7,8] For each plan a pinpoint ion chamber (PTW 31006, 0.015 cm 3 : PTW) located at the central axis of the cylindrical phantom was used to verify the isocenter point dose, while an EDR2 film was inserted axially into the Alderson phantom at the region of the primary tumor to carry out the 2D dose measurement. The measured and calculated dose planes were imported and compared using Varisoft software (version 3.1: PTW).…”

“…This technique had been published and applied successfully for the treatment of prostate cancer. [7,8] When a static wedge is attached to the rotating gantry the technique is known as wedged dynamic arc therapy (W-DAT). Consequently, one can consider this technique as one step forward of the 3D-CRT toward to provide the complex concave dose distribution.…”

Dosimetric comparison between three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) in the treatment of different stages of nasopharyngeal carcinoma

“…23 Film calibration was performed with the help of five kodak EDR2 films and 30 × 30 × 30 cm 3 solid water phantom (PTW--29672, Freiburg, Germany). 24,25 All plan verification methods ensured that for all three techniques (3D-CRT, 7F-IMRT and 9F-IMRT) measured and calculated dose planes were compatible and respect the gamma index criteria.…”

Beam's-Eye-View Dosimetrics–Guided Inverse Planning for Aperture-Modulated Arc Therapy

“…Aperture-modulated arc therapy (AMAT) has recently attracted much attention because of its rapid delivery as well as superior dose distribution (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). The AMAT treatment plan for a given patient is usually obtained by approximating a continuous arc delivery with a large number of fixed-gantry beams, followed by optimizing an objective function with respect to the weights and segment shapes of the beams.…”