Determination of Very Slow Diffusion of Paramagnetic Ions by NMR Spectroscopy


Autoria(s): Cervantes Rodríguez, Hernán Joel; Bloise Junior, Antonio Carlos; Rabbani, Said Rahnamaye
Contribuinte(s)

UNIVERSIDADE DE SÃO PAULO

Data(s)

20/10/2012

20/10/2012

2010

Resumo

In this paper, we propose a new method of measuring the very slow paramagnetic ion diffusion coefficient using a commercial high-resolution spectrometer. If there are distinct paramagnetic ions influencing the hydrogen nuclear magnetic relaxation time differently, their diffusion coefficients can be measured separately. A cylindrical phantom filled with Fricke xylenol gel solution and irradiated with gamma rays was used to validate the method. The Fricke xylenol gel solution was prepared with 270 Bloom porcine gelatin, the phantom was irradiated with gamma rays originated from a (60)Co source and a high-resolution 200 MHz nuclear magnetic resonance (NMR) spectrometer was used to obtain the phantom (1)H profile in the presence of a linear magnetic field gradient. By observing the temporal evolution of the phantom NMR profile, an apparent ferric ion diffusion coefficient of 0.50 mu m(2)/ms due to ferric ions diffusion was obtained. In any medical process where the ionizing radiation is used, the dose planning and the dose delivery are the key elements for the patient safety and success of treatment. These points become even more important in modern conformal radio therapy techniques, such as stereotactic radiosurgery, where the delivered dose in a single session of treatment can be an order of magnitude higher than the regular doses of radiotherapy. Several methods have been proposed to obtain the three-dimensional (3-D) dose distribution. Recently, we proposed an alternative method for the 3-D radiation dose mapping, where the ionizing radiation modifies the local relative concentration of Fe(2+)/Fe(3+) in a phantom containing Fricke gel and this variation is associated to the MR image intensity. The smearing of the intensity gradient is proportional to the diffusion coefficient of the Fe(3+) and Fe(2+) in the phantom. There are several methods for measurement of the ionic diffusion using NMR, however, they are applicable when the diffusion is not very slow.

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao Paulo

Comissao Nacional de Energia Nuclear (CNEN)

Comissão Nacional de Energia Nuclear (CNEN)

IPEN

Instituto de Pesquisas Energéticas e Nucleares (IPEN)

Identificador

APPLIED MAGNETIC RESONANCE, v.38, n.4, p.417-429, 2010

0937-9347

http://producao.usp.br/handle/BDPI/29187

10.1007/s00723-010-0130-3

http://dx.doi.org/10.1007/s00723-010-0130-3

Idioma(s)

eng

Publicador

SPRINGER WIEN

Relação

Applied Magnetic Resonance

Direitos

restrictedAccess

Copyright SPRINGER WIEN

Palavras-Chave #DOSE DISTRIBUTIONS #Physics, Atomic, Molecular & Chemical #Spectroscopy
Tipo

article

original article

publishedVersion