Dosimetric impact of the 160 MLC on head and neck IMRT treatments

Abstract

The purpose of this work is to investigate if the change in plan quality with the finer leaf resolution and lower leakage of the 160 MLC would be dosimetrically significant for head and neck intensity‐modulated radiation therapy (IMRT) treatment plans. The 160 MLC consisting of 80 leaves of 0.5 cm on each bank, a leaf span of 20 cm, and leakage of less than 0.37% without additional backup jaws was compared against the 120 Millennium MLC with 60 leaves of 0.5 and 1.0 cm, a leaf span of 14.5 cm, and leakage of 2.0%. CT image sets of 16 patients previously treated for stage III and IV head and neck carcinomas were replanned on Prowess 5.0 and Eclipse 11.0 using the 160 MLC and the 120 MLC. IMRT constraints for both sets of 6 MV plans were identical and based on RTOG 0522. Dose‐volume histograms (DVHs), minimum dose, mean dose, maximum dose, and dose to 1 cc to the organ at risks (OAR) and the planning target volume, as recommended by QUANTEC 2010, were compared. Both collimators were able to achieve the target dose to the PTVs. The dose to the organs at risk (brainstem, spinal cord, parotids, and larynx) were 1%–12% (i.e., 0.5–8 Gy for a 70 Gy prescription) lower with the 160 MLC compared to the 120 MLC, depending on the proximity of the organ to the target. The large field HN plans generated with the 160 MLC were dosimetrically advantageous for critical structures, especially those located further away from the central axis, without compromising the target volume.PACS number: 87.55 D‐

Planning for mARC treatments with the Eclipse treatment planning system

“…A Siemens ARTISTE linac with a 160‐leaf MLC 16 , 17 , 18 was modeled in the system using data collected as part of the commissioning of the linac. Models were created for the flattened 6 MV beam and unflat 7 MV.…”

“…All of the test plans were created on a prototype Eclipse 13.5 system that was accessed through a citrix environment (Citrix Systems Inc., Fort Lauderdale, FL). A Siemens ARTISTE linac with a 160-leaf MLC (16)(17)(18) was modeled in the system using data collected as part of the commissioning of the linac. Models were created for the flattened 6 MV beam and unflat 7 MV.…”

Characterization of a novel VenusX orthogonal dual‐layer multileaf collimator

“…[1][2][3][4][5] MLC has been used in radiotherapy for over 30 years, 6,7 and its design characteristics influence treatment plan dose distributions. [8][9][10][11][12][13][14] Single-layer MLC architecture is primarily used in medical linear accelerators, such as the Varian Millennium 120-leaf MLC system 15,16 and the Agility collimator of the Elekta MLC system. 6 Unfortunately, the application of single-layer MLC in radiotherapy has many limitations.…”

Characterization of a novel VenusX orthogonal dual-layer multileaf collimator

“…The MultiLeaf collimator (MLC) is the most widely tool used to modulate the beam uence for intensitymodulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) [1][2][3][4][5]. MLC has been used in radiotherapy for over 30 years [6-7], and its design characteristics in uence treatment plan dose distributions [8][9][10][11][12][13][14]. Single-layer MLC architecture is mainly used in medical linear accelerator, such as the Varian Millennium 120-leaf MLC system [15,16] and the Agility collimator of Elekta MLC system [6].…”