Characterization of a multileaf collimator system

Journal Article · Fri Jan 15 04:00:00 EST 1993 · International Journal of Radiation Oncology, Biology and Physics; (United States)

DOI:https://doi.org/10.1016/0360-3016(93)90339-W· OSTI ID:6614872

Galvin, J M ^[1]; Smith, A R ^[2]; Lally, B ^[3]

---

1. New York Univ. Medical Center (United States)
2. Harvard Medical School, Boston, MA (United States)
3. Univ. of Pennsylvania School of BioEngineering, Philadelphia (United States)

Commissioning measurements for a multileaf collimator installed on a dual energy accelerator with 6 and 15 MV photons are described. Detailed dosimetric characterization of the multileaf collimator is a requirement for modeling the collimator with treatment planning software. Measurements include a determination of the penumbra width, leaf transmission, between-leaf leakage, and localization of the leaf ends and sides. Standard radiographic film was used for the penumbra measurements, and separate experiments using radiochromic film and thermoluminescent dosimeters were performed to verify that distortions of the dose distribution at an edge due to changing energy sensitivity of silver bromide film are negligible. Films were analyzed with a scanning laser densitometer with a 210 micron spot. Little change in the penumbra edge distribution was noted for different positions of a leaf in the field. Experiments localizing the physical end of the leaves showed less than 1 mm deviation from the 50% decrement line. This small difference is attributed to the shaped end on the leaves. One side of a single leaf corresponded to the 50% decrement line, but the opposite face was aligned with a lower value. This difference is due to the tongue and groove used to decrease between-leaf leakage. For both energies, approximately 2% of photons incident on the multileaf collimator are transmitted and an additional 0.5% leakage occurs between the leaves. Alignment of the leaves to form a straight edge results in a penumbra profile which compares favorably with the standard technique of using alloy blocks. When the edge is stepped, the isodose lines follow the leaf pattern and the boundary is poorly defined compared to divergent blocks. 19 refs., 13 figs.

• OSTI ID: 6614872
• Journal Information: International Journal of Radiation Oncology, Biology and Physics; (United States), Journal Name: International Journal of Radiation Oncology, Biology and Physics; (United States) Vol. 25:2; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

550603* -- Medicine-- External Radiation in Therapy-- (1980-)
62 RADIOLOGY AND NUCLEAR MEDICINE
COLLIMATORS
COMPUTERIZED CONTROL SYSTEMS
CONTROL SYSTEMS
DESIGN
DOSEMETERS
DOSIMETRY
MEASURING INSTRUMENTS
MEDICINE
NUCLEAR MEDICINE
ON-LINE CONTROL SYSTEMS
ON-LINE SYSTEMS
RADIOLOGY
RADIOTHERAPY
THERAPY