A dosimetric comparison of various multileaf collimators

M. Saiful Huq, Indra J. Das, Todd Steinberg, James M. Galvin

Research output: Contribution to journalArticle

88 Citations (Scopus)

Abstract

The dosimetric characteristics of three multileaf collimator (MLC) systems (Elekta, Siemens and Varian) having 10 mm leaf width are compared. A 6 MV photon beam was used from each unit for measurements. Film dosimetry was performed for the measurements and the analysis techniques were exactly duplicated in each system. Two of the collimators have rounded leaf ends (Elekta and Varian) and the third (Siemens) has a flat end that follows beam divergence. A scanning densitometer (Wellhöfer with 0.45 mm spot and 0.5 mm step size) was used for film analysis. The dosimetric characteristics studied include: penumbra width (80-20%) as a function of position of the leaf end in the field, inter- and intra-leaf radiation leakage, dose distribution of the tongue and groove, and isodose curves for stepped leaves forming 45° angle beam edge. Results show that MLC designs with divergent and non-divergent leaves produce penumbra (80-20%) widths that are within 2.0 mm of each other. However, the distance of the collimator from the x-ray target plays an important role, and the smallest penumbra width was noted for the Varian MLC despite its rounded leaf-end design. Compared to the other systems, this collimator is positioned about 15 cm closer to the patient which affects the skin dose. The MLC with flat leaf end, although closer to the target, showed slightly poorer penumbra width. Inter-leaf leakage through the leaves is 1.3% for two of the collimators (Elekta and Varian) with the backup jaws and is nearly 1% for the third system (Siemens). The Siemens MLC produces reduced tongue-and-groove effect compared to the other two collimators (Elekta and Varian). The isodose undulation for a stepped edge is found to be significant for the collimator closest to the patient (Varian) and does not depend on the leaf-end shape. There is no perfect MLC system that can be recommended, rather each one has unique advantages and disadvantages that should be weighed with comfort, ease and cost effectiveness for clinical use.

Original languageEnglish (US)
JournalPhysics in Medicine and Biology
Volume47
Issue number12
DOIs
StatePublished - Jun 21 2002
Externally publishedYes

Fingerprint

collimators
Tongue
leaves
Dosimetry
Film Dosimetry
Densitometers
Cost effectiveness
Jaw
Photons
Cost-Benefit Analysis
penumbras
Skin
X-Rays
Radiation
Scanning
X rays
tongue
grooves
leakage
densitometers

ASJC Scopus subject areas

  • Biomedical Engineering
  • Physics and Astronomy (miscellaneous)
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology

Cite this

A dosimetric comparison of various multileaf collimators. / Huq, M. Saiful; Das, Indra J.; Steinberg, Todd; Galvin, James M.

In: Physics in Medicine and Biology, Vol. 47, No. 12, 21.06.2002.

Research output: Contribution to journalArticle

Huq, M. Saiful ; Das, Indra J. ; Steinberg, Todd ; Galvin, James M. / A dosimetric comparison of various multileaf collimators. In: Physics in Medicine and Biology. 2002 ; Vol. 47, No. 12.
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