Characterization of a multileaf collimator system

Galvin, James M.; Smith, Alfred R.; Lally, Brian E.

doi:10.1016/0360-3016(93)90339-w

Cited by 165 publications

(88 citation statements)

References 15 publications

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“…The dosimetric effects of the 1.0‐cm leaf width multileaf collimators have been described previously. ( 1 – 3 ) The limitation of a broad‐leaved MLC may be pronounced when employing small fields in stereotactic radiotherapy or treating targets in close proximity to critical organs.…”

Section: Introductionmentioning

confidence: 99%

Stereotactic IMRT for prostate cancer: Dosimetric impact of multileaf collimator leaf width in the treatment of prostate cancer with IMRT

Wang

Movsas

Jacob

et al. 2004

J Applied Clin Med Phys

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The focus of this work is the dosimetric impact of multileaf collimator (MLC) leaf width on the treatment of prostate cancer with intensity‐modulated radiation therapy (IMRT). Ten patients with prostate cancer were planned for IMRT delivery using two different MLC leaf widths—4 mm and 10 mm— representing the Radionics micro‐multileaf collimator (mMLC) and Siemens MLC, respectively. Treatment planning was performed on the XKnifeRT2 treatment‐planning system (Radionics, Burlington, MA). All beams and optimization parameters were identical for the mMLC and MLC plans. All the plans were normalized to ensure that 95% of the planning target volume (PTV) received 100% of the prescribed dose. The differences in dose distribution between the two different plans were assessed by dose–volume histogram (DVH) analysis of the target and critical organs. We specifically compared the volume of rectum receiving 40 Gy (V40), 50 Gy (V50), 60 Gy (V60), the dose received by 17% and 35% of rectum (D17 and D35), and the maximum dose to 1 cm3 of the rectum for a prescription dose of 74 Gy. For the urinary bladder, the dose received by 25% of bladder (D25), V40, and the maximum dose to 1 cm3 of the organ were recorded. For PTV we compared the maximum dose to the “hottest” 1 cm3 (Dmax1cm3) and the dose to 99% of the PTV (D99). The dose inhomogeneity in the target, defined as the ratio of the difference in Dmax1cm3 and D99 to the prescribed dose, was also compared between the two plans. In all cases studied, significant reductions in the volume of rectum receiving doses less than 65 Gy were seen using the mMLC. The average decrease in the volume of the rectum receiving 40 Gy, 50 Gy, and 60 Gy using the mMLC plans was 40.2%, 33.4%, and 17.7%, respectively, with p<0.0001 for V40 and V50 and p<0.012 for V60. The mean dose reductions for D17 and D35 for the rectum using the mMLC were 20.4% (p<0.0001) and 18.3% (p<0.0002), respectively. There were consistent reductions in all dose indices studied for the bladder. The target dose inhomogeneity was improved in the mMLC plans by an average of 29%. In the high‐dose range, there was no significant difference in the dose deposited in the “hottest” 1 cm3 of the rectum between the two plans for all cases (p>0.78). In conclusion, the use of the mMLC for IMRT of the prostate resulted in significant improvement in the DVH parameters of the prostate and critical organs, which may improve the therapeutic ratio.PACS number: 87.53.Tf

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Section: Introductionmentioning

confidence: 99%

Stereotactic IMRT for prostate cancer: Dosimetric impact of multileaf collimator leaf width in the treatment of prostate cancer with IMRT

Wang

Movsas

Jacob

et al. 2004

J Applied Clin Med Phys

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“…Early implementations of multileaf collimation [51][52][53] were limited to tests and tolerance recommendations for early Varian MLC machines. Soon afterward, Jordan and Williams 54 published a paper for Elekta machines and Das et al 55 for Siemens machines.…”

Section: Iid3 Mlcmentioning

confidence: 99%

Task Group 142 report: Quality assurance of medical acceleratorsa)

et al. 2009

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The task group ͑TG͒ for quality assurance of medical accelerators was constituted by the American Association of Physicists in Medicine's Science Council under the direction of the Radiation Therapy Committee and the Quality Assurance and Outcome Improvement Subcommittee. The task group ͑TG-142͒ had two main charges. First to update, as needed, recommendations of Table II of the AAPM TG-40 report on quality assurance and second, to add recommendations for asymmetric jaws, multileaf collimation ͑MLC͒, and dynamic/virtual wedges. The TG accomplished the update to TG-40, specifying new test and tolerances, and has added recommendations for not only the new ancillary delivery technologies but also for imaging devices that are part of the linear accelerator. The imaging devices include x-ray imaging, photon portal imaging, and cone-beam CT. The TG report was designed to account for the types of treatments delivered with the particular machine. For example, machines that are used for radiosurgery treatments or intensity-modulated radiotherapy ͑IMRT͒ require different tests and/or tolerances. There are specific recommendations for MLC quality assurance for machines performing IMRT. The report also gives recommendations as to action levels for the physicists to implement particular actions, whether they are inspection, scheduled action, or immediate and corrective action. The report is geared to be flexible for the physicist to customize the QA program depending on clinical utility. There are specific tables according to daily, monthly, and annual reviews, along with unique tables for wedge systems, MLC, and imaging checks. The report also gives specific recommendations regarding setup of a QA program by the physicist in regards to building a QA team, establishing procedures, training of personnel, documentation, and end-to-end system checks. been considerably expanded as compared with the original TG-40 report and the recommended tolerances accommodate differences in the intended use of the machine functionality ͑non-IMRT, IMRT, and stereotactic delivery͒.

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“…Galvin et al (1993a) and Klein et al (1995) reported leaf transmission values of 1.5 to 2.0% for a Varian 6 MV beam, and 1.5 to 5% for an 18 MV beam. Transmission through the screw attachment plane was 2.5%.…”

Section: Multileaf Collimationmentioning

confidence: 95%