Dose perturbation caused by high-density inhomogeneities in small beams in stereotactic radiosurgery

Surendra N. Rustgi, Atul K. Rustgi, Steve B. Jiang, Komanduri M. Ayyangar

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

The influence of high-density tissue heterogeneities in small-diameter beams used in stereotactic radiosurgery has been investigated. Dose perturbation immediately behind aluminium sheets, used to simulate a high- density tissue inhomogeneity such as bone, was studied in a solid water phantom. Dose reduction factors (DRFs), which are the ratios of the dose in the presence of the inhomogeneity to dose in a uniform density solid water phantom, were measured with a diamond detector for three thicknesses of aluminium. DRFs exhibit dependence on both the inhomogeneity thickness and the beam diameter. The DRF decreases with inhomogeneity thickness. The DRF initially decreases with increase in the beam diameter from 12.5 to 25 mm. For fields greater than 25 mm, the DRFs are nearly constant. The commonly used algorithms such as the TAR ratio method underestimate the magnitude of the measured effect. A good agreement between these measurements and Monte Carlo calculations is obtained. The influence of the high-density inhomogeneity on the tissue maximum ratio (TMR) was also measured with the inhomogeneity at a fixed depth d(max) from the entrance surface. The TMR is reduced for all detector-inhomogeneity distances investigated. The dose build-up phenomenon observed in the presence of low-density air inhomogeneity is absent in the presence of a high-density inhomogeneity. The beam width (defined by 50% dose points) immediately beyond the inhomogeneity is unaffected by the high-density inhomogeneity. However, the 90%-10% and 80%- 20% dose penumbra widths and the dose outside the beam edge (beyond the 50% dose point) are reduced. This reduction in dose outside the beam edge is caused by the reduced range of the secondary radiation (photons and electrons) in the high-density medium.

Original languageEnglish (US)
Pages (from-to)3509-3518
Number of pages10
JournalPhysics in Medicine and Biology
Volume43
Issue number12
DOIs
StatePublished - Dec 1998

Fingerprint

Radiosurgery
inhomogeneity
perturbation
dosage
Aluminum
Tissue
Diamond
Water
Photons
Detectors
Aluminum sheet
Air
Electrons
Radiation
Bone and Bones
Diamonds
Bone
aluminum
penumbras
detectors

ASJC Scopus subject areas

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

Cite this

Dose perturbation caused by high-density inhomogeneities in small beams in stereotactic radiosurgery. / Rustgi, Surendra N.; Rustgi, Atul K.; Jiang, Steve B.; Ayyangar, Komanduri M.

In: Physics in Medicine and Biology, Vol. 43, No. 12, 12.1998, p. 3509-3518.

Research output: Contribution to journalArticle

Rustgi, Surendra N. ; Rustgi, Atul K. ; Jiang, Steve B. ; Ayyangar, Komanduri M. / Dose perturbation caused by high-density inhomogeneities in small beams in stereotactic radiosurgery. In: Physics in Medicine and Biology. 1998 ; Vol. 43, No. 12. pp. 3509-3518.
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