Abstract
To evaluate dynamic conformal arc therapy (DAT) dose distribution and clinical applicability in comparison to intensity‐modulated radiotherapy (IMRT) in different types of tumors and locations, twelve patients with prostate cancer with no node involvement and three patients with single tumors in the pituitary, in the neck and in the thoracic spinal region treated with IMRT, were retrospectively planned with DAT using Eclipse (V8.1). The prostate cases were also planned with three‐dimensional conformal radiation therapy (3DCRT). Dose distributions were evaluated through comparisons of dose‐volumetric histograms and in‐house IMRT protocol constraints, as well as validated via ion chamber array measurements. DAT plans for prostate showed a statistically comparable achievement of tumor conformity and dose sparing for bladder and rectum when compared to IMRT. Dose on femoral heads were similar to those achieved using 3DCRT. DAT could be planned with similar results to those obtained in IMRT for the dose constraints of the defined structures by using a 360° arc for the brain lesion and several arcs including noncoplanar ones for the head‐and‐neck and spinal tumors. Experimental validation of the calculated dose distributions via gamma analysis of composite distributions for DAT provided that more than 95% of the pixels satisfy the criteria 3 mm–3%, which was similar to that of IMRT. The average number of monitor units was approximately five times lower than IMRT. In conclusion, DAT is capable of providing conformal dose distributions to the targets accomplishing many of the IMRT dose constraints simultaneously. Experimental dose‐validation accuracy, ease of planning and reduced treatment times make DAT both acceptable and attractive for clinical use.PACS numbers: 87.55.D‐, 87.55.dk, 87.55.Qr, 87.56.bd, 87.56.Fc, 87.53.Kn, 87.55. de, 87.55.kd
Highlights
Does intensity-modulated radiotherapy (IMRT) planning and dose validation demand increased treatment efforts compared to other conventional external-beam radiation therapy techniques, and the dynamic/static multileaf collimator (MLC) modulation in IMRT requires increased treatment times
The mean minimum and maximum dose values for prostate-planning target volumes (PTV) are better achieved with 3DCRT
One possible explanation is that the six static symmetrically arranged coplanar beams provide a slightly better chance to get a higher degree of uniformity in dose distribution than the more lateral arc coverage in dynamic conformal arc therapy (DAT) and, in a lesser degree, the additional constraints imposed for the other organs in inverse IMRT planning
Summary
Does IMRT planning and dose validation demand increased treatment efforts compared to other conventional external-beam radiation therapy techniques, and the dynamic/static MLC modulation in IMRT requires increased treatment times (monitor units). Image-guidance techniques are often utilized (i.e., cone beam CT and respiratory gating),(1) which further add extra complexity and treatment time Another issue which may be associated with long periods of time to deliver a desired dose is biological effectiveness. For cases where static beams with no modulation are not sufficiently adequate to deliver dose to the tumor as well as sparing healthy organs, the additional option of rotating the gantry while shaping the MLC around the tumor may considerably improve the resulting dose distributions. This technique is known as dynamic conformal arc therapy (DAT). The DAT technique will shorten treatment times and may reduce the need for complex image guidance procedures
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