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angles, as is known for flow cytometry in which forward scatter 0.5~1.5 degree is regarded as an esti-
mate of the size of whole cell [15]. The scattering information in larger scattering angles indicates that
the nucleus is primarily responsible for scattering; and smaller organelles, such as mitochondria and ly-
sosomes, are likely responsible for scattering at larger angles [16]. According to these corresponding
relationships, forward scattering information (FS) in label free cells' laser scattering spectra can be cho-
sen for diagnosing cells' healthy state with their obvious outer size differences. Under the conditions of
cells with similar outer sizes, the side scattering information (SS) in label free cells laser scattering
spectra is needed as another diagnosis standard. In flow cytometry, cells are distinguished by plotting
FS-SS scattering diagrams in which the abscissa is forward scattering intensity data and the ordinate is
sideward scattering intensity data. Cell's type and healthy status can be determined by the distributions
of scattering data in FS-SS scattering diagrams. But for cells which have similar size and structure, their
scattering points in FS-SS scattering diagrams will be overlapped. All the signal points are mixed up
and gathered in same FS-SS scattering diagram zone. Unfortunately, this overlapping phenomenon al-
ways occurs in FS-SS scattering diagrams. Therefore, cells with similar size but tiny structural differ-
ences can not be distinguished, such as monoblast and abnormal infantile monocyte of human acute
monocytic leukemia. But recognizing and distinguishing these cells have very significant meaning, be-
cause it can supply an important hint for precancerous patients to let them get timely treatments in early
cancerous stage. With the help of this kind of hints, the survival rates of cancerous patients can be
greatly improved. In flow cytometry, normally the threshold gates for distinguishing cells’ types are set
manually in terms of the experiences of operators. However, in this way the overlapping problem can
not be solved also. FS-SS scattering diagram is still invalid in separating cells with similar size but tiny
structural differences. The information of cells’ slight structural differences is submerged in the scat-
tering cloud clusters of FS-SS scattering diagram.
As the most important cells' internal structure, nucleus's size difference has very close relationships
with cell's health state. Normally, when cells transfer malignant, their whole sizes almost keep un-
changed. But nucleus's size becomes large. In this paper, cells with the same membrane size but differ-
ent nucleus size are set as the research objects. Aiming to this kind of cell's malignant transformation,
how to distinguish healthy and malignant cells by their laser scattering spectra is our main research tar-
get. To the best of our knowledge, only Caigen Liu [17] proposed an algorithm in 2005 named
area-averaged quantity algorithm to process laser scattering spectra for distinguishing cells structural
differences. But Liu’s algorithm is not sensitive enough for cells which size or structural differences are
slight. In this paper, a novel analysis algorithm of laser scattering spectrum, named Even Interval Inci-
dent Angle algorithm (EIIA), is put forward for classifying normal and abnormal cells which have tiny
different structure properties.
2 EVEN INTERVAL INCIDENT ANLGE ALGORITHM
In order to illuminate EIIA, laser scattering spectra of label free Jurkat cells are firstly selected as an
example. Jurkat cell belongs to an immortalized line of T lymphocyte cells that are used to study acute
T cell leukemia, T cell signaling, and the expression of various chemokine receptors susceptible to viral
entry, particularly HIV. The shapes of normal Jurkat cells are round and roe-like with the average radius
about 6 m
, and the nucleus average radius is about 3 m
which refractive index is 1.39. The cytoplasm
whose refractive index is 1.35 is full of the room between cell’s nucleus and membrane. Assuming Jur-
kat cell’s outside environment refractive index is 1.33, and it is illuminated by laser light with wave-
length 633nm. According to the parameters, finite difference time domain method (FDTD) is utilized to
simulate laser scattering spectra in spatial fields. The detail methods for FDTD modeling and program-
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