Restenosis is the major limitation of coronary angioplasty. Recently brachytherapy has emerged as a potential treatment for restenosis using photon emitters such as 192Ir, 125I, 103Pd and beta emitters such as 32P, 90Sr, and 90Y. Two approaches under investigation for intravascular brachytherapy are: (i) use of a radioactive source at the end of a catheter, (ii) permanent implantation of a radioactive stent at the occlusion site. The first is an example of temporary intracavitary brachytherapy where radioactive sources are placed in a body cavity near the target lesion; the other is an example of permanent brachytherapy where radioactive sources are implanted in the target lesion. It is well known that dose gradients in the immediate vicinity of the radioactive sources are very high because of the geometric and tissue attenuation effects. Traditionally, the dose to the target is specified at a distance of 1 cm from the source. At this reference distance the dosimetry of brachytherapy sources is reasonably well established. However, the intended target for irradiation in intravascular brachytherapy is much smaller, in the range of 1 - 3 mm. At these short distances, the dosimetry is highly uncertain and needs improvement. One of the major reasons for dose uncertainty at short distances may be the contribution from low energy secondary radiations, such as fluorescent x rays, beta particles, secondary electrons etc., which are primarily absorbed in the source encapsulation or the first few mm of tissue around the source. Their effects are largely ignored in traditional brachytherapy dosimetry because only a small fraction of the target volume is affected by them. This is, however, not true for intravascular brachytherapy where the entire target may be within millimeters of the source. With many investigations currently underway, mostly with commercial support, to determine the efficacy of intravascular brachytherapy, there is a tremendous need to not only standardize the prescription of dose, but importantly to also determine the dose delivered over short distances. This dosimetry may well be significantly different depending on specific radionuclide as well as design of source and applicators. In this project, the physics of intravascular brachytherapy dosimetry for treatment of restenosis will be investigated using thermoluminescent dosimeter chips and sheets, radiochromic film, polymer gel dosimeters, Rossi-type proportional chamber for microdosimetry, and Monte Carlo simulations. Finally, effects of tissue heterogeneity and self-shielding effects of catheters and stents for photons and beta particles will also be investigated.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL058022-03
Application #
2901294
Study Section
Radiation Study Section (RAD)
Project Start
1997-04-01
Project End
2001-07-31
Budget Start
1999-04-01
Budget End
2001-07-31
Support Year
3
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Yale University
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
082359691
City
New Haven
State
CT
Country
United States
Zip Code
06520
Yue, Ning; Roberts, Kenneth; Nath, Ravinder (2004) Effects of vessel curvature on dose distributions in catheter-based intravascular brachytherapy for various radionuclides. Cardiovasc Radiat Med 5:142-50
Nath, Ravinder; Yue, Ning (2004) Effects of off-centering on dose uniformity along and around blood vessels undergoing catheter-based intravascular brachytherapy. Cardiovasc Radiat Med 5:88-96
Yue, Ning; Roberts, Kenneth B; Son, Haijun et al. (2004) Optimization of dose distributions for bifurcated coronary vessels treated with catheter-based photon and beta emitters using the simulated annealing algorithm. Med Phys 31:2610-22
Iwata, Kazuro; Yue, Ning J; Nath, Ravinder (2004) Two-dimensional dosimetry in the near field of the model 200 103Pd source for interstitial brachytherapy implants using a thermoluminescent sheet. Phys Med Biol 49:4049-63
Iwata, Kazuro; Yue, Ning J; Nath, Ravinder (2004) Near-field dosimetry of 125I sources for interstitial brachytherapy implants measured using thermoluminescent sheets. Med Phys 31:3406-16
Roa, Dante E; Song, Haijun; Yue, Ning et al. (2004) Dosimetric characteristics of the Novoste Beta-Cath 90Sr/Y source trains at submillimeter distances. Med Phys 31:1269-76
Chen, Z; Nath, R (2001) Dose rate constant and energy spectrum of interstitial brachytherapy sources. Med Phys 28:86-96
Nath, R; Yue, N (2001) Shielding effects of metallic encapsulations and radiographic contrast agents for catheter-based intravascular brachytherapy. Cardiovasc Radiat Med 2:93-103
Yue, N; Nath, R; Roberts, K (2000) Dosimetric penumbra effects in catheter-based intravascular brachytherapy using a centered photon or beta line source. Cardiovasc Radiat Med 2:32-8
Bohan, M; Yue, N; Nath, R (2000) On the need for massive additional shielding of a catheterization laboratory for the implementation of high dose rate 192Ir intravascular brachytherapy. Cardiovasc Radiat Med 2:39-41

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