Temperature mapping of laser-induced hyperthermia in an ocular phantom using magnetic resonance thermography

Saher M. Maswadi, Stephen J. Dodd, Jia Hong Gao, Randolph D. Glickman

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Laser-induced heating in an ocular phantom is measured with magnetic resonance thermography (MRT) using temperature-dependent phase changes in proton resonance frequency. The ocular phantom contains a layer of melanosomes isolated from bovine retinal pigment epithelium. The phantom is heated by the 806-nm output of a continuous wave diode laser with an irradiance of 2.4 to 21.6 W/cm2 in a beam radius of 0.8 or 2.4 mm, depending on the experiment. MRT is performed with a 2T magnet, and a two-turn, 6-cm-diam, circular radio frequency coil. Two-dimensional temperature gradients are measured within the plane of the melanin layer, as well as normal to it, with a temperature resolution of 1°C or better. The temperature gradients extending within the melanin layer are broader than those orthogonal to the layer, consistent with the higher optical absorption and consequent heating in the melanin. The temperature gradients in the phantom measured by MRT closely approximate the predictions of a classical heat diffusion model. Three-dimensional temperature maps with a spatial resolution of 0.25 mm in all directions are also made. Although the temporal resolution is limited in the prototype system (22.9 s for a single image "slice"), improvements in future implementations are likely. These results indicate that MRT has sufficient spatial and temperature resolution to monitor target tissue temperature during transpupillary thermotherapy in the human eye.

Original languageEnglish (US)
Pages (from-to)711-718
Number of pages8
JournalJournal of Biomedical Optics
Volume9
Issue number4
DOIs
StatePublished - Jul 2004

Fingerprint

Induced Hyperthermia
hyperthermia
Magnetic resonance
magnetic resonance
Melanin
Lasers
Magnetic Resonance Spectroscopy
melanin
Melanins
Temperature
Thermal gradients
temperature gradients
lasers
spatial resolution
temperature
proton resonance
Heating
heating
Retinal Pigments
epithelium

Keywords

  • Infrared
  • Lasers
  • Magnetic resonance thermography
  • Ocular phantoms
  • Transpupillary thermotherapy

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology
  • Clinical Biochemistry
  • Atomic and Molecular Physics, and Optics
  • Biomedical Engineering
  • Biomaterials
  • Electronic, Optical and Magnetic Materials

Cite this

Temperature mapping of laser-induced hyperthermia in an ocular phantom using magnetic resonance thermography. / Maswadi, Saher M.; Dodd, Stephen J.; Gao, Jia Hong; Glickman, Randolph D.

In: Journal of Biomedical Optics, Vol. 9, No. 4, 07.2004, p. 711-718.

Research output: Contribution to journalArticle

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