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Benefits of Radiotherapy Added Nanoparticle Assessed by a Quantitative Analysis of Dose‐Gradient: An Evaluation in Soft and Lung Tissues by Monte Carlo
Author(s) -
Marques T,
Schwarcke M,
Garrido C,
Baffa O,
Nicolucci P
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3468350
Subject(s) - nuclear medicine , dosimetry , monte carlo method , volume (thermodynamics) , radiation therapy , materials science , biomedical engineering , physics , mathematics , medicine , radiology , statistics , quantum mechanics
Purpose : Evaluate the volume fraction enclosed by maximum isodose (isodose max ) within a structure as a quantitative criterion for assessing the benefits of using nanoparticles in Radiotherapy. Material and Methods : Dose enhancement can be evaluated in a volume with and without nanoparticles by the ratio between mean doses, defining an average‐dose‐enhancement‐factor (DEF). Decompounding DEF in multiplicative terms is possible to define a maximum‐dose‐enhancement‐factor(DEFmax) and a dose‐gradient‐factor(GF). GF express what fraction of volume is enclosed by the isodose max present in the analyzed structure. GF close to 1 express that the isodose max present in the analyzed volume increase its value. GF close to 0 indicates that the isodose max decrease its value. Soft and lung targets with 3×3×1cm 3 containing and not containing 0.11mM concentration of gold nanoparticles (AuNP) were considered to Monte Carlo simulations, performed with PENELOPE‐2008. Adjacent‐volumes were delimited as tissues 1cm far from the target in all directions. A 120kV x‐ray beam was considered to simulate Intra‐Operative‐Radiotherapy situations. Results : Dose distributions visually revels changes in dose‐gradient and depth dose curves presents it quantitatively. In target soft tissue: DEF soft ‐ tissuetarget = 2 . 44 and DEF max soft ‐ tissue target = 2 . 40 ; To adjacent‐volume DEF soft ‐ tissueadjacent volume = 1 . 14 and max soft ‐ tissueadjacent volume = 2 . 44 . It indicates that in target isodose max changes not so much, presenting almost the same values in situations with and without AuNP; However in adjacent‐volume isodose max had its value increased. In target lung tissue: DEF lung ‐ tissuetarget = 2 . 43 ;DEF max lung ‐ tissuetarget = 2 . 49 ;DEF lung ‐ tissueadjacent volume = 0 . 92 ;DEF max lung ‐ tissueadjacent volume = 2 . 30 . These parameters indicate that the isodose max changes its value not so much in lung‐target but radically in lung‐adjacent‐tissue. This behavior is expressed in each corresponding GF of these structures: GF soft ‐ tissuetarget = 1 . 02 ;GF soft ‐ tissueadjacent volume = 0 . 47 ;GF lung ‐ tissuetarget = 0 . 97 ;GF lung ‐ tissueadjacent volume = 0 . 39 . Coclusions : AuNP increase the mean dose in target and decrease radically the maximum isodose in adjacent tissues. The GF express quantitatively how attenuation and dose‐contribution effects are balanced providing information to guide clinical cases of nanoparticle added to Radiotherapy.