UVITEC Cambridge FIREREADER MAX, Руководство пользователя и обслуживания

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P O T Q U A N T I F I C A T I O N
Principles of quantification
You can use the Volume tools to quantitate bands, spots, arrays, and other image data
The images taken by the Uvitec Cambridge’s imaging systems are displayed by your
computer screen in the form of grey scale images. Our systems convert the light signals
from your gel or membrane samples into digital data.
A digital image is a finite set of pixels. The digital image contains a fixed number of rows
and columns of pixels. Pixels are the smallest individual element in an image, holding
quantized values that represent the light intensity at any specific point. The light intensity
is graded into a grey scale. The word pixel is based on a contraction of pix ("pictures") and
el (for "element").
Volume is use in the band or spot quantification process. The volume is the sum of all the
pixels intensities included in the defined area ( separation). To measure the
quantity of a particular band or spot, you need to define a band or a spot area.
Quantification is based on the image in pixels whose intensity is coded on a scale.
- The scale has 256 grey levels for a 8-bit image
- The scale has 4 096 grey levels for a 12-bit image
- The scale has 16 384 grey levels for a 14-bit image
- The scale has 65 536 grey levels for a 16-bit image
The quantity (or density) of a spot is calculated from its volume. This is made of the sum of
all pixel intensities composing the spot
In other words, the spot quantity then depends on:
- The number of pixels inside the area of the spot
- The intensities of these points
V =
∑
ni Ii
Image analysis allows comparison in between concentrated intense spots and weaker but
more diffused bands.
Results are given in volumes that may be recalculated according to an OD of reference or
a concentration master-curve.
To measure the amount of a particular spot, you need to define the boundary around the
spot and compare the intensity data inside the boundary with the data of other spots or of
a standard.