11 Time-of-Flight Spectroscopy
269
11.4 Application of TOF-NIRS to Agricultural Science
The important parameters for fruits or vegetables (i.e., maturity, quality parameters,
and defect) can be detected by measuring the optical parameters as Lu et al. reviewed
[5]. The couple of most important quality attributes to different fruits are firmness
and soluble solids content (SSC). Many studies demonstrate that both μ a and μ
s
have relation to hardness, SSC, and skin color. However, it was generally reported
that μ a was suitable for predicting these quality parameters. This may be due to the
fact that pigments or other chemical compositions would change during maturation
with changes of cell structure directly affecting hardness. In most of the cases, the
combination of μ a and μ
s was found to improve the prediction of fruit maturity
and quality parameters. The prediction of firmness and SSC by TR technology was
widely reported for apple, kiwifruit, mango, nectarine, peach, and pear. Because
physiological disorders often cause the changes in the chemical and structural properties of the fruits product result in the change of μ a and μ
s , it is possible to detect
the defect in the fruits by observing the optical properties in fruits. Especially, TR
technology can be used to detect internal browning and internal bleeding of apples,
nectarines, plums, thanks to its ability to penetrate tissue deeper inside the fruits.
Determined bulked absorption coefficients of fruits in the spectral regions of 500–
1850 nm were largely dominated by the water in the NIR range and fruit-specific
pigments in the visible range. The differences in μ
s behavior (μ
s decrease exponentially with the increase of wavelength) between fruits, cultivars and tissue type are
related to microstructural differences, such as differences in cellular structure and
porosity. μ
s values are reported for various fruits ranging from 0 to 20 cm
−1 .
11.5 Application of TOF-NIRS to Medical Science
One of the research areas where TR investigation is most actively conducted is the
medical science. Diffuse optical tomography in NIR region at the range of wavelength
from 700 to 1000 nm is proven to have the potential for noninvasive diagnoses of
tissue oxygenation and thyroid cancers. As a first step toward properly designing
devices, interpreting diagnostic measurements or planning therapeutic is to identify
the accurate optical properties of a tissue. Following research might be the use of
optical properties determined to describe the light transportation and absorption.
Jacques [9] summarized 1. μ a of various tissues in terms of the average hemoglobin
concentration or some similar properties and 2. μ
s with the parameters (a, b), or
alternatively (a
, f Rayleigh , b Mie ) which explain the μ
s variation with wavelength
change. The μ
s (λ) were expressed by the equation μ
s = a
λ
500(nm)
−b
or μ
s =
a
f Rayleigh
λ
500(nm)
−4 +
1 − f Rayleigh
λ
500(nm)
−b Mie
where the λ is wavelength.
In the later equation, scattering is described in terms of the separate contribution
269
11.4 Application of TOF-NIRS to Agricultural Science
The important parameters for fruits or vegetables (i.e., maturity, quality parameters,
and defect) can be detected by measuring the optical parameters as Lu et al. reviewed
[5]. The couple of most important quality attributes to different fruits are firmness
and soluble solids content (SSC). Many studies demonstrate that both μ a and μ
s
have relation to hardness, SSC, and skin color. However, it was generally reported
that μ a was suitable for predicting these quality parameters. This may be due to the
fact that pigments or other chemical compositions would change during maturation
with changes of cell structure directly affecting hardness. In most of the cases, the
combination of μ a and μ
s was found to improve the prediction of fruit maturity
and quality parameters. The prediction of firmness and SSC by TR technology was
widely reported for apple, kiwifruit, mango, nectarine, peach, and pear. Because
physiological disorders often cause the changes in the chemical and structural properties of the fruits product result in the change of μ a and μ
s , it is possible to detect
the defect in the fruits by observing the optical properties in fruits. Especially, TR
technology can be used to detect internal browning and internal bleeding of apples,
nectarines, plums, thanks to its ability to penetrate tissue deeper inside the fruits.
Determined bulked absorption coefficients of fruits in the spectral regions of 500–
1850 nm were largely dominated by the water in the NIR range and fruit-specific
pigments in the visible range. The differences in μ
s behavior (μ
s decrease exponentially with the increase of wavelength) between fruits, cultivars and tissue type are
related to microstructural differences, such as differences in cellular structure and
porosity. μ
s values are reported for various fruits ranging from 0 to 20 cm
−1 .
11.5 Application of TOF-NIRS to Medical Science
One of the research areas where TR investigation is most actively conducted is the
medical science. Diffuse optical tomography in NIR region at the range of wavelength
from 700 to 1000 nm is proven to have the potential for noninvasive diagnoses of
tissue oxygenation and thyroid cancers. As a first step toward properly designing
devices, interpreting diagnostic measurements or planning therapeutic is to identify
the accurate optical properties of a tissue. Following research might be the use of
optical properties determined to describe the light transportation and absorption.
Jacques [9] summarized 1. μ a of various tissues in terms of the average hemoglobin
concentration or some similar properties and 2. μ
s with the parameters (a, b), or
alternatively (a
, f Rayleigh , b Mie ) which explain the μ
s variation with wavelength
change. The μ
s (λ) were expressed by the equation μ
s = a
λ
500(nm)
−b
or μ
s =
a
f Rayleigh
λ
500(nm)
−4 +
1 − f Rayleigh
λ
500(nm)
−b Mie
where the λ is wavelength.
In the later equation, scattering is described in terms of the separate contribution